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Lab 4

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This commit is contained in:
Anish Athalye 2018-10-06 09:52:47 -04:00
parent a9d7717cc4
commit da1f8392b1
56 changed files with 2696 additions and 37 deletions
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4
GNUmakefile
View File

@ -88,6 +88,7 @@ CFLAGS := $(CFLAGS) $(DEFS) $(LABDEFS) -O1 -fno-builtin -I$(TOP) -MD
CFLAGS += -fno-omit-frame-pointer
CFLAGS += -std=gnu99
CFLAGS += -static
CFLAGS += -fno-pie
CFLAGS += -Wall -Wno-format -Wno-unused -Werror -gstabs -m32
# -fno-tree-ch prevented gcc from sometimes reordering read_ebp() before
# mon_backtrace()'s function prologue on gcc version: (Debian 4.7.2-5) 4.7.2
@ -142,9 +143,12 @@ include lib/Makefrag
include user/Makefrag
CPUS ?= 1
QEMUOPTS = -drive file=$(OBJDIR)/kern/kernel.img,index=0,media=disk,format=raw -serial mon:stdio -gdb tcp::$(GDBPORT)
QEMUOPTS += $(shell if $(QEMU) -nographic -help | grep -q '^-D '; then echo '-D qemu.log'; fi)
IMAGES = $(OBJDIR)/kern/kernel.img
QEMUOPTS += -smp $(CPUS)
QEMUOPTS += $(QEMUEXTRA)
.gdbinit: .gdbinit.tmpl

7
boot/main.c
View File

@ -39,6 +39,7 @@ void
bootmain(void)
{
struct Proghdr *ph, *eph;
int i;
// read 1st page off disk
readseg((uint32_t) ELFHDR, SECTSIZE*8, 0);
@ -50,10 +51,14 @@ bootmain(void)
// load each program segment (ignores ph flags)
ph = (struct Proghdr *) ((uint8_t *) ELFHDR + ELFHDR->e_phoff);
eph = ph + ELFHDR->e_phnum;
for (; ph < eph; ph++)
for (; ph < eph; ph++) {
// p_pa is the load address of this segment (as well
// as the physical address)
readseg(ph->p_pa, ph->p_memsz, ph->p_offset);
for (i = 0; i < ph->p_memsz - ph->p_filesz; i++) {
*((char *) ph->p_pa + ph->p_filesz + i) = 0;
}
}
// call the entry point from the ELF header
// note: does not return!

4
conf/lab.mk
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@ -1,2 +1,2 @@
LAB=3
PACKAGEDATE=Tue Sep 25 12:21:10 EDT 2018
LAB=4
PACKAGEDATE=Mon Oct 8 21:31:51 PDT 2018

190
grade-lab4 Executable file
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@ -0,0 +1,190 @@
#!/usr/bin/env python
import re
from gradelib import *
r = Runner(save("jos.out"),
stop_breakpoint("readline"))
def E(s, trim=False):
"""Expand $En in s to the environment ID of the n'th user
environment."""
tmpl = "%x" if trim else "%08x"
return re.sub(r"\$E([0-9]+)",
lambda m: tmpl % (0x1000 + int(m.group(1))-1), s)
@test(5)
def test_dumbfork():
r.user_test("dumbfork")
r.match(E(".00000000. new env $E1"),
E(".$E1. new env $E2"),
"0: I am the parent.",
"9: I am the parent.",
"0: I am the child.",
"9: I am the child.",
"19: I am the child.",
E(".$E1. exiting gracefully"),
E(".$E1. free env $E1"),
E(".$E2. exiting gracefully"),
E(".$E2. free env $E2"))
end_part("A")
@test(5)
def test_faultread():
r.user_test("faultread")
r.match(E(".$E1. user fault va 00000000 ip 008....."),
"TRAP frame at 0xf....... from CPU .",
" trap 0x0000000e Page Fault",
" err 0x00000004.*",
E(".$E1. free env $E1"),
no=["I read ........ from location 0."])
@test(5)
def test_faultwrite():
r.user_test("faultwrite")
r.match(E(".$E1. user fault va 00000000 ip 008....."),
"TRAP frame at 0xf....... from CPU .",
" trap 0x0000000e Page Fault",
" err 0x00000006.*",
E(".$E1. free env $E1"))
@test(5)
def test_faultdie():
r.user_test("faultdie")
r.match("i faulted at va deadbeef, err 6",
E(".$E1. exiting gracefully"),
E(".$E1. free env $E1"))
@test(5)
def test_faultregs():
r.user_test("faultregs")
r.match("Registers in UTrapframe OK",
"Registers after page-fault OK",
no=["Registers in UTrapframe MISMATCH",
"Registers after page-fault MISMATCH"])
@test(5)
def test_faultalloc():
r.user_test("faultalloc")
r.match("fault deadbeef",
"this string was faulted in at deadbeef",
"fault cafebffe",
"fault cafec000",
"this string was faulted in at cafebffe",
E(".$E1. exiting gracefully"),
E(".$E1. free env $E1"))
@test(5)
def test_faultallocbad():
r.user_test("faultallocbad")
r.match(E(".$E1. user_mem_check assertion failure for va deadbeef"),
E(".$E1. free env $E1"))
@test(5)
def test_faultnostack():
r.user_test("faultnostack")
r.match(E(".$E1. user_mem_check assertion failure for va eebfff.."),
E(".$E1. free env $E1"))
@test(5)
def test_faultbadhandler():
r.user_test("faultbadhandler")
r.match(E(".$E1. user_mem_check assertion failure for va (deadb|eebfe)..."),
E(".$E1. free env $E1"))
@test(5)
def test_faultevilhandler():
r.user_test("faultevilhandler")
r.match(E(".$E1. user_mem_check assertion failure for va (f0100|eebfe)..."),
E(".$E1. free env $E1"))
@test(5)
def test_forktree():
r.user_test("forktree")
r.match("....: I am .0.",
"....: I am .1.",
"....: I am .000.",
"....: I am .100.",
"....: I am .110.",
"....: I am .111.",
"....: I am .011.",
"....: I am .001.",
E(".$E1. exiting gracefully"),
E(".$E2. exiting gracefully"),
".0000200.. exiting gracefully",
".0000200.. free env 0000200.")
end_part("B")
@test(5)
def test_spin():
r.user_test("spin")
r.match(E(".00000000. new env $E1"),
"I am the parent. Forking the child...",
E(".$E1. new env $E2"),
"I am the parent. Running the child...",
"I am the child. Spinning...",
"I am the parent. Killing the child...",
E(".$E1. destroying $E2"),
E(".$E1. free env $E2"),
E(".$E1. exiting gracefully"),
E(".$E1. free env $E1"))
@test(5)
def test_stresssched():
r.user_test("stresssched", make_args=["CPUS=4"])
r.match(".000010... stresssched on CPU 0",
".000010... stresssched on CPU 1",
".000010... stresssched on CPU 2",
".000010... stresssched on CPU 3",
no=[".*ran on two CPUs at once"])
@test(5)
def test_sendpage():
r.user_test("sendpage", make_args=["CPUS=2"])
r.match(".00000000. new env 00001000",
E(".00000000. new env $E1"),
E(".$E1. new env $E2"),
E("$E1 got message: hello child environment! how are you?", trim=True),
E("child received correct message", trim=True),
E("$E2 got message: hello parent environment! I'm good", trim=True),
E("parent received correct message", trim=True),
E(".$E1. exiting gracefully"),
E(".$E1. free env $E1"),
E(".$E2. exiting gracefully"),
E(".$E2. free env $E2"))
@test(5)
def test_pingpong():
r.user_test("pingpong", make_args=["CPUS=4"])
r.match(E(".00000000. new env $E1"),
E(".$E1. new env $E2"),
E("send 0 from $E1 to $E2", trim=True),
E("$E2 got 0 from $E1", trim=True),
E("$E1 got 1 from $E2", trim=True),
E("$E2 got 8 from $E1", trim=True),
E("$E1 got 9 from $E2", trim=True),
E("$E2 got 10 from $E1", trim=True),
E(".$E1. exiting gracefully"),
E(".$E1. free env $E1"),
E(".$E2. exiting gracefully"),
E(".$E2. free env $E2"))
@test(5)
def test_primes():
r.user_test("primes", stop_on_line("CPU .: 1877"), stop_on_line(".*panic"),
make_args=["CPUS=4"], timeout=60)
r.match(E(".00000000. new env $E1"),
E(".$E1. new env $E2"),
E("CPU .: 2 .$E2. new env $E3"),
E("CPU .: 3 .$E3. new env $E4"),
E("CPU .: 5 .$E4. new env $E5"),
E("CPU .: 7 .$E5. new env $E6"),
E("CPU .: 11 .$E6. new env $E7"),
E("CPU .: 1877 .$E289. new env $E290"))
end_part("C")
run_tests()

11
inc/env.h
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@ -51,9 +51,20 @@ struct Env {
enum EnvType env_type; // Indicates special system environments
unsigned env_status; // Status of the environment
uint32_t env_runs; // Number of times environment has run
int env_cpunum; // The CPU that the env is running on
// Address space
pde_t *env_pgdir; // Kernel virtual address of page dir
// Exception handling
void *env_pgfault_upcall; // Page fault upcall entry point
// Lab 4 IPC
bool env_ipc_recving; // Env is blocked receiving
void *env_ipc_dstva; // VA at which to map received page
uint32_t env_ipc_value; // Data value sent to us
envid_t env_ipc_from; // envid of the sender
int env_ipc_perm; // Perm of page mapping received
};
#endif // !JOS_INC_ENV_H

3
inc/error.h
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@ -14,6 +14,9 @@ enum {
// the maximum allowed
E_FAULT , // Memory fault
E_IPC_NOT_RECV , // Attempt to send to env that is not recving
E_EOF , // Unexpected end of file
MAXERROR
};

35
inc/lib.h
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@ -16,6 +16,7 @@
#include <inc/env.h>
#include <inc/memlayout.h>
#include <inc/syscall.h>
#include <inc/trap.h>
#define USED(x) (void)(x)
@ -31,6 +32,9 @@ extern const volatile struct PageInfo pages[];
// exit.c
void exit(void);
// pgfault.c
void set_pgfault_handler(void (*handler)(struct UTrapframe *utf));
// readline.c
char* readline(const char *buf);
@ -39,6 +43,37 @@ void sys_cputs(const char *string, size_t len);
int sys_cgetc(void);
envid_t sys_getenvid(void);
int sys_env_destroy(envid_t);
void sys_yield(void);
static envid_t sys_exofork(void);
int sys_env_set_status(envid_t env, int status);
int sys_env_set_pgfault_upcall(envid_t env, void *upcall);
int sys_page_alloc(envid_t env, void *pg, int perm);
int sys_page_map(envid_t src_env, void *src_pg,
envid_t dst_env, void *dst_pg, int perm);
int sys_page_unmap(envid_t env, void *pg);
int sys_ipc_try_send(envid_t to_env, uint32_t value, void *pg, int perm);
int sys_ipc_recv(void *rcv_pg);
// This must be inlined. Exercise for reader: why?
static inline envid_t __attribute__((always_inline))
sys_exofork(void)
{
envid_t ret;
asm volatile("int %2"
: "=a" (ret)
: "a" (SYS_exofork), "i" (T_SYSCALL));
return ret;
}
// ipc.c
void ipc_send(envid_t to_env, uint32_t value, void *pg, int perm);
int32_t ipc_recv(envid_t *from_env_store, void *pg, int *perm_store);
envid_t ipc_find_env(enum EnvType type);
// fork.c
#define PTE_SHARE 0x400
envid_t fork(void);
envid_t sfork(void); // Challenge!

3
inc/memlayout.h
View File

@ -138,6 +138,9 @@
// The location of the user-level STABS data structure
#define USTABDATA (PTSIZE / 2)
// Physical address of startup code for non-boot CPUs (APs)
#define MPENTRY_PADDR 0x7000
#ifndef __ASSEMBLER__
typedef uint32_t pte_t;

9
inc/syscall.h
View File

@ -7,6 +7,15 @@ enum {
SYS_cgetc,
SYS_getenvid,
SYS_env_destroy,
SYS_page_alloc,
SYS_page_map,
SYS_page_unmap,
SYS_exofork,
SYS_env_set_status,
SYS_env_set_pgfault_upcall,
SYS_yield,
SYS_ipc_try_send,
SYS_ipc_recv,
NSYSCALLS
};

11
inc/trap.h
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@ -74,6 +74,17 @@ struct Trapframe {
uint16_t tf_padding4;
} __attribute__((packed));
struct UTrapframe {
/* information about the fault */
uint32_t utf_fault_va; /* va for T_PGFLT, 0 otherwise */
uint32_t utf_err;
/* trap-time return state */
struct PushRegs utf_regs;
uintptr_t utf_eip;
uint32_t utf_eflags;
/* the trap-time stack to return to */
uintptr_t utf_esp;
} __attribute__((packed));
#endif /* !__ASSEMBLER__ */

25
kern/Makefrag
View File

@ -32,6 +32,12 @@ KERN_SRCFILES := kern/entry.S \
lib/readline.c \
lib/string.c
# Source files for LAB4
KERN_SRCFILES += kern/mpentry.S \
kern/mpconfig.c \
kern/lapic.c \
kern/spinlock.c
# Only build files if they exist.
KERN_SRCFILES := $(wildcard $(KERN_SRCFILES))
@ -51,6 +57,25 @@ KERN_BINFILES := user/hello \
user/faultwrite \
user/faultwritekernel
# Binary files for LAB4
KERN_BINFILES += user/idle \
user/yield \
user/dumbfork \
user/stresssched \
user/faultdie \
user/faultregs \
user/faultalloc \
user/faultallocbad \
user/faultnostack \
user/faultbadhandler \
user/faultevilhandler \
user/forktree \
user/sendpage \
user/spin \
user/fairness \
user/pingpong \
user/pingpongs \
user/primes
KERN_OBJFILES := $(patsubst %.c, $(OBJDIR)/%.o, $(KERN_SRCFILES))
KERN_OBJFILES := $(patsubst %.S, $(OBJDIR)/%.o, $(KERN_OBJFILES))
KERN_OBJFILES := $(patsubst $(OBJDIR)/lib/%, $(OBJDIR)/kern/%, $(KERN_OBJFILES))

5
kern/console.c
View File

@ -7,6 +7,8 @@
#include <inc/assert.h>
#include <kern/console.h>
#include <kern/trap.h>
#include <kern/picirq.h>
static void cons_intr(int (*proc)(void));
static void cons_putc(int c);
@ -373,6 +375,9 @@ kbd_intr(void)
static void
kbd_init(void)
{
// Drain the kbd buffer so that QEMU generates interrupts.
kbd_intr();
irq_setmask_8259A(irq_mask_8259A & ~(1<<IRQ_KBD));
}

46
kern/cpu.h Normal file
View File

@ -0,0 +1,46 @@
#ifndef JOS_INC_CPU_H
#define JOS_INC_CPU_H
#include <inc/types.h>
#include <inc/memlayout.h>
#include <inc/mmu.h>
#include <inc/env.h>
// Maximum number of CPUs
#define NCPU 8
// Values of status in struct Cpu
enum {
CPU_UNUSED = 0,
CPU_STARTED,
CPU_HALTED,
};
// Per-CPU state
struct CpuInfo {
uint8_t cpu_id; // Local APIC ID; index into cpus[] below
volatile unsigned cpu_status; // The status of the CPU
struct Env *cpu_env; // The currently-running environment.
struct Taskstate cpu_ts; // Used by x86 to find stack for interrupt
};
// Initialized in mpconfig.c
extern struct CpuInfo cpus[NCPU];
extern int ncpu; // Total number of CPUs in the system
extern struct CpuInfo *bootcpu; // The boot-strap processor (BSP)
extern physaddr_t lapicaddr; // Physical MMIO address of the local APIC
// Per-CPU kernel stacks
extern unsigned char percpu_kstacks[NCPU][KSTKSIZE];
int cpunum(void);
#define thiscpu (&cpus[cpunum()])
void mp_init(void);
void lapic_init(void);
void lapic_startap(uint8_t apicid, uint32_t addr);
void lapic_eoi(void);
void lapic_ipi(int vector);
#endif

38
kern/env.c
View File

@ -11,9 +11,11 @@
#include <kern/pmap.h>
#include <kern/trap.h>
#include <kern/monitor.h>
#include <kern/sched.h>
#include <kern/cpu.h>
#include <kern/spinlock.h>
struct Env *envs = NULL; // All environments
struct Env *curenv = NULL; // The current env
static struct Env *env_free_list; // Free environment list
// (linked by Env->env_link)
@ -34,7 +36,7 @@ static struct Env *env_free_list; // Free environment list
// definition of gdt specifies the Descriptor Privilege Level (DPL)
// of that descriptor: 0 for kernel and 3 for user.
//
struct Segdesc gdt[] =
struct Segdesc gdt[NCPU + 5] =
{
// 0x0 - unused (always faults -- for trapping NULL far pointers)
SEG_NULL,
@ -51,7 +53,8 @@ struct Segdesc gdt[] =
// 0x20 - user data segment
[GD_UD >> 3] = SEG(STA_W, 0x0, 0xffffffff, 3),
// 0x28 - tss, initialized in trap_init_percpu()
// Per-CPU TSS descriptors (starting from GD_TSS0) are initialized
// in trap_init_percpu()
[GD_TSS0 >> 3] = SEG_NULL
};
@ -242,6 +245,15 @@ env_alloc(struct Env **newenv_store, envid_t parent_id)
e->env_tf.tf_cs = GD_UT | 3;
// You will set e->env_tf.tf_eip later.
// Enable interrupts while in user mode.
// LAB 4: Your code here.
// Clear the page fault handler until user installs one.
e->env_pgfault_upcall = 0;
// Also clear the IPC receiving flag.
e->env_ipc_recving = 0;
// commit the allocation
env_free_list = e->env_link;
*newenv_store = e;
@ -398,15 +410,26 @@ env_free(struct Env *e)
//
// Frees environment e.
// If e was the current env, then runs a new environment (and does not return
// to the caller).
//
void
env_destroy(struct Env *e)
{
// If e is currently running on other CPUs, we change its state to
// ENV_DYING. A zombie environment will be freed the next time
// it traps to the kernel.
if (e->env_status == ENV_RUNNING && curenv != e) {
e->env_status = ENV_DYING;
return;
}
env_free(e);
cprintf("Destroyed the only environment - nothing more to do!\n");
while (1)
monitor(NULL);
if (curenv == e) {
curenv = NULL;
sched_yield();
}
}
@ -419,6 +442,9 @@ env_destroy(struct Env *e)
void
env_pop_tf(struct Trapframe *tf)
{
// Record the CPU we are running on for user-space debugging
curenv->env_cpunum = cpunum();
asm volatile(
"\tmovl %0,%%esp\n"
"\tpopal\n"

3
kern/env.h
View File

@ -4,9 +4,10 @@
#define JOS_KERN_ENV_H
#include <inc/env.h>
#include <kern/cpu.h>
extern struct Env *envs; // All environments
extern struct Env *curenv; // Current environment
#define curenv (thiscpu->cpu_env) // Current environment
extern struct Segdesc gdt[];
void env_init(void);

88
kern/init.c
View File

@ -10,18 +10,17 @@
#include <kern/kclock.h>
#include <kern/env.h>
#include <kern/trap.h>
#include <kern/sched.h>
#include <kern/picirq.h>
#include <kern/cpu.h>
#include <kern/spinlock.h>
static void boot_aps(void);
void
i386_init(void)
{
extern char edata[], end[];
// Before doing anything else, complete the ELF loading process.
// Clear the uninitialized global data (BSS) section of our program.
// This ensures that all static/global variables start out zero.
memset(edata, 0, end - edata);
// Initialize the console.
// Can't call cprintf until after we do this!
cons_init();
@ -35,18 +34,85 @@ i386_init(void)
env_init();
trap_init();
// Lab 4 multiprocessor initialization functions
mp_init();
lapic_init();
// Lab 4 multitasking initialization functions
pic_init();
// Acquire the big kernel lock before waking up APs
// Your code here:
// Starting non-boot CPUs
boot_aps();
#if defined(TEST)
// Don't touch -- used by grading script!
ENV_CREATE(TEST, ENV_TYPE_USER);
#else
// Touch all you want.
ENV_CREATE(user_hello, ENV_TYPE_USER);
ENV_CREATE(user_primes, ENV_TYPE_USER);
#endif // TEST*
// We only have one user environment for now, so just run it.
env_run(&envs[0]);
// Schedule and run the first user environment!
sched_yield();
}
// While boot_aps is booting a given CPU, it communicates the per-core
// stack pointer that should be loaded by mpentry.S to that CPU in
// this variable.
void *mpentry_kstack;
// Start the non-boot (AP) processors.
static void
boot_aps(void)
{
extern unsigned char mpentry_start[], mpentry_end[];
void *code;
struct CpuInfo *c;
// Write entry code to unused memory at MPENTRY_PADDR
code = KADDR(MPENTRY_PADDR);
memmove(code, mpentry_start, mpentry_end - mpentry_start);
// Boot each AP one at a time
for (c = cpus; c < cpus + ncpu; c++) {
if (c == cpus + cpunum()) // We've started already.
continue;
// Tell mpentry.S what stack to use
mpentry_kstack = percpu_kstacks[c - cpus] + KSTKSIZE;
// Start the CPU at mpentry_start
lapic_startap(c->cpu_id, PADDR(code));
// Wait for the CPU to finish some basic setup in mp_main()
while(c->cpu_status != CPU_STARTED)
;
}
}
// Setup code for APs
void
mp_main(void)
{
// We are in high EIP now, safe to switch to kern_pgdir
lcr3(PADDR(kern_pgdir));
cprintf("SMP: CPU %d starting\n", cpunum());
lapic_init();
env_init_percpu();
trap_init_percpu();
xchg(&thiscpu->cpu_status, CPU_STARTED); // tell boot_aps() we're up
// Now that we have finished some basic setup, call sched_yield()
// to start running processes on this CPU. But make sure that
// only one CPU can enter the scheduler at a time!
//
// Your code here:
// Remove this after you finish Exercise 6
for (;;);
}
/*
* Variable panicstr contains argument to first call to panic; used as flag
@ -71,7 +137,7 @@ _panic(const char *file, int line, const char *fmt,...)
asm volatile("cli; cld");
va_start(ap, fmt);
cprintf("kernel panic at %s:%d: ", file, line);
cprintf("kernel panic on CPU %d at %s:%d: ", cpunum(), file, line);
vcprintf(fmt, ap);
cprintf("\n");
va_end(ap);

9
kern/kernel.ld
View File

@ -44,18 +44,19 @@ SECTIONS
/* The data segment */
.data : {
*(.data)
*(.data .data.*)
}
.bss : {
PROVIDE(edata = .);
*(.bss)
*(.dynbss)
*(.bss .bss.*)
*(COMMON)
PROVIDE(end = .);
BYTE(0)
}
/DISCARD/ : {
*(.eh_frame .note.GNU-stack)
*(.eh_frame .note.GNU-stack .comment .note)
}
}

182
kern/lapic.c Normal file
View File

@ -0,0 +1,182 @@
// The local APIC manages internal (non-I/O) interrupts.
// See Chapter 8 & Appendix C of Intel processor manual volume 3.
#include <inc/types.h>
#include <inc/memlayout.h>
#include <inc/trap.h>
#include <inc/mmu.h>
#include <inc/stdio.h>
#include <inc/x86.h>
#include <kern/pmap.h>
#include <kern/cpu.h>
// Local APIC registers, divided by 4 for use as uint32_t[] indices.
#define ID (0x0020/4) // ID
#define VER (0x0030/4) // Version
#define TPR (0x0080/4) // Task Priority
#define EOI (0x00B0/4) // EOI
#define SVR (0x00F0/4) // Spurious Interrupt Vector
#define ENABLE 0x00000100 // Unit Enable
#define ESR (0x0280/4) // Error Status
#define ICRLO (0x0300/4) // Interrupt Command
#define INIT 0x00000500 // INIT/RESET
#define STARTUP 0x00000600 // Startup IPI
#define DELIVS 0x00001000 // Delivery status
#define ASSERT 0x00004000 // Assert interrupt (vs deassert)
#define DEASSERT 0x00000000
#define LEVEL 0x00008000 // Level triggered
#define BCAST 0x00080000 // Send to all APICs, including self.
#define OTHERS 0x000C0000 // Send to all APICs, excluding self.
#define BUSY 0x00001000
#define FIXED 0x00000000
#define ICRHI (0x0310/4) // Interrupt Command [63:32]
#define TIMER (0x0320/4) // Local Vector Table 0 (TIMER)
#define X1 0x0000000B // divide counts by 1
#define PERIODIC 0x00020000 // Periodic
#define PCINT (0x0340/4) // Performance Counter LVT
#define LINT0 (0x0350/4) // Local Vector Table 1 (LINT0)
#define LINT1 (0x0360/4) // Local Vector Table 2 (LINT1)
#define ERROR (0x0370/4) // Local Vector Table 3 (ERROR)
#define MASKED 0x00010000 // Interrupt masked
#define TICR (0x0380/4) // Timer Initial Count
#define TCCR (0x0390/4) // Timer Current Count
#define TDCR (0x03E0/4) // Timer Divide Configuration
physaddr_t lapicaddr; // Initialized in mpconfig.c
volatile uint32_t *lapic;
static void
lapicw(int index, int value)
{
lapic[index] = value;
lapic[ID]; // wait for write to finish, by reading
}
void
lapic_init(void)
{
if (!lapicaddr)
return;
// lapicaddr is the physical address of the LAPIC's 4K MMIO
// region. Map it in to virtual memory so we can access it.
lapic = mmio_map_region(lapicaddr, 4096);
// Enable local APIC; set spurious interrupt vector.
lapicw(SVR, ENABLE | (IRQ_OFFSET + IRQ_SPURIOUS));
// The timer repeatedly counts down at bus frequency
// from lapic[TICR] and then issues an interrupt.
// If we cared more about precise timekeeping,
// TICR would be calibrated using an external time source.
lapicw(TDCR, X1);
lapicw(TIMER, PERIODIC | (IRQ_OFFSET + IRQ_TIMER));
lapicw(TICR, 10000000);
// Leave LINT0 of the BSP enabled so that it can get
// interrupts from the 8259A chip.
//
// According to Intel MP Specification, the BIOS should initialize
// BSP's local APIC in Virtual Wire Mode, in which 8259A's
// INTR is virtually connected to BSP's LINTIN0. In this mode,
// we do not need to program the IOAPIC.
if (thiscpu != bootcpu)
lapicw(LINT0, MASKED);
// Disable NMI (LINT1) on all CPUs
lapicw(LINT1, MASKED);
// Disable performance counter overflow interrupts
// on machines that provide that interrupt entry.
if (((lapic[VER]>>16) & 0xFF) >= 4)
lapicw(PCINT, MASKED);
// Map error interrupt to IRQ_ERROR.
lapicw(ERROR, IRQ_OFFSET + IRQ_ERROR);
// Clear error status register (requires back-to-back writes).
lapicw(ESR, 0);
lapicw(ESR, 0);
// Ack any outstanding interrupts.
lapicw(EOI, 0);
// Send an Init Level De-Assert to synchronize arbitration ID's.
lapicw(ICRHI, 0);
lapicw(ICRLO, BCAST | INIT | LEVEL);
while(lapic[ICRLO] & DELIVS)
;
// Enable interrupts on the APIC (but not on the processor).
lapicw(TPR, 0);
}
int
cpunum(void)
{
if (lapic)
return lapic[ID] >> 24;
return 0;
}
// Acknowledge interrupt.
void
lapic_eoi(void)
{
if (lapic)
lapicw(EOI, 0);
}
// Spin for a given number of microseconds.
// On real hardware would want to tune this dynamically.
static void
microdelay(int us)
{
}
#define IO_RTC 0x70
// Start additional processor running entry code at addr.
// See Appendix B of MultiProcessor Specification.
void
lapic_startap(uint8_t apicid, uint32_t addr)
{
int i;
uint16_t *wrv;
// "The BSP must initialize CMOS shutdown code to 0AH
// and the warm reset vector (DWORD based at 40:67) to point at
// the AP startup code prior to the [universal startup algorithm]."
outb(IO_RTC, 0xF); // offset 0xF is shutdown code
outb(IO_RTC+1, 0x0A);
wrv = (uint16_t *)KADDR((0x40 << 4 | 0x67)); // Warm reset vector
wrv[0] = 0;
wrv[1] = addr >> 4;
// "Universal startup algorithm."
// Send INIT (level-triggered) interrupt to reset other CPU.
lapicw(ICRHI, apicid << 24);
lapicw(ICRLO, INIT | LEVEL | ASSERT);
microdelay(200);
lapicw(ICRLO, INIT | LEVEL);
microdelay(100); // should be 10ms, but too slow in Bochs!
// Send startup IPI (twice!) to enter code.
// Regular hardware is supposed to only accept a STARTUP
// when it is in the halted state due to an INIT. So the second
// should be ignored, but it is part of the official Intel algorithm.
// Bochs complains about the second one. Too bad for Bochs.
for (i = 0; i < 2; i++) {
lapicw(ICRHI, apicid << 24);
lapicw(ICRLO, STARTUP | (addr >> 12));
microdelay(200);
}
}
void
lapic_ipi(int vector)
{
lapicw(ICRLO, OTHERS | FIXED | vector);
while (lapic[ICRLO] & DELIVS)
;
}

225
kern/mpconfig.c Normal file
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@ -0,0 +1,225 @@
// Search for and parse the multiprocessor configuration table
// See http://developer.intel.com/design/pentium/datashts/24201606.pdf
#include <inc/types.h>
#include <inc/string.h>
#include <inc/memlayout.h>
#include <inc/x86.h>
#include <inc/mmu.h>
#include <inc/env.h>
#include <kern/cpu.h>
#include <kern/pmap.h>
struct CpuInfo cpus[NCPU];
struct CpuInfo *bootcpu;
int ismp;
int ncpu;
// Per-CPU kernel stacks
unsigned char percpu_kstacks[NCPU][KSTKSIZE]
__attribute__ ((aligned(PGSIZE)));
// See MultiProcessor Specification Version 1.[14]
struct mp { // floating pointer [MP 4.1]
uint8_t signature[4]; // "_MP_"
physaddr_t physaddr; // phys addr of MP config table
uint8_t length; // 1
uint8_t specrev; // [14]
uint8_t checksum; // all bytes must add up to 0
uint8_t type; // MP system config type
uint8_t imcrp;
uint8_t reserved[3];
} __attribute__((__packed__));
struct mpconf { // configuration table header [MP 4.2]
uint8_t signature[4]; // "PCMP"
uint16_t length; // total table length
uint8_t version; // [14]
uint8_t checksum; // all bytes must add up to 0
uint8_t product[20]; // product id
physaddr_t oemtable; // OEM table pointer
uint16_t oemlength; // OEM table length
uint16_t entry; // entry count
physaddr_t lapicaddr; // address of local APIC
uint16_t xlength; // extended table length
uint8_t xchecksum; // extended table checksum
uint8_t reserved;
uint8_t entries[0]; // table entries
} __attribute__((__packed__));
struct mpproc { // processor table entry [MP 4.3.1]
uint8_t type; // entry type (0)
uint8_t apicid; // local APIC id
uint8_t version; // local APIC version
uint8_t flags; // CPU flags
uint8_t signature[4]; // CPU signature
uint32_t feature; // feature flags from CPUID instruction
uint8_t reserved[8];
} __attribute__((__packed__));
// mpproc flags
#define MPPROC_BOOT 0x02 // This mpproc is the bootstrap processor
// Table entry types
#define MPPROC 0x00 // One per processor
#define MPBUS 0x01 // One per bus
#define MPIOAPIC 0x02 // One per I/O APIC
#define MPIOINTR 0x03 // One per bus interrupt source
#define MPLINTR 0x04 // One per system interrupt source
static uint8_t
sum(void *addr, int len)
{
int i, sum;
sum = 0;
for (i = 0; i < len; i++)
sum += ((uint8_t *)addr)[i];
return sum;
}
// Look for an MP structure in the len bytes at physical address addr.
static struct mp *
mpsearch1(physaddr_t a, int len)
{
struct mp *mp = KADDR(a), *end = KADDR(a + len);
for (; mp < end; mp++)
if (memcmp(mp->signature, "_MP_", 4) == 0 &&
sum(mp, sizeof(*mp)) == 0)
return mp;
return NULL;
}
// Search for the MP Floating Pointer Structure, which according to
// [MP 4] is in one of the following three locations:
// 1) in the first KB of the EBDA;
// 2) if there is no EBDA, in the last KB of system base memory;
// 3) in the BIOS ROM between 0xE0000 and 0xFFFFF.
static struct mp *
mpsearch(void)
{
uint8_t *bda;
uint32_t p;
struct mp *mp;
static_assert(sizeof(*mp) == 16);
// The BIOS data area lives in 16-bit segment 0x40.
bda = (uint8_t *) KADDR(0x40 << 4);
// [MP 4] The 16-bit segment of the EBDA is in the two bytes
// starting at byte 0x0E of the BDA. 0 if not present.
if ((p = *(uint16_t *) (bda + 0x0E))) {
p <<= 4; // Translate from segment to PA
if ((mp = mpsearch1(p, 1024)))
return mp;
} else {
// The size of base memory, in KB is in the two bytes
// starting at 0x13 of the BDA.
p = *(uint16_t *) (bda + 0x13) * 1024;
if ((mp = mpsearch1(p - 1024, 1024)))
return mp;
}
return mpsearch1(0xF0000, 0x10000);
}
// Search for an MP configuration table. For now, don't accept the
// default configurations (physaddr == 0).
// Check for the correct signature, checksum, and version.
static struct mpconf *
mpconfig(struct mp **pmp)
{
struct mpconf *conf;
struct mp *mp;
if ((mp = mpsearch()) == 0)
return NULL;
if (mp->physaddr == 0 || mp->type != 0) {
cprintf("SMP: Default configurations not implemented\n");
return NULL;
}
conf = (struct mpconf *) KADDR(mp->physaddr);
if (memcmp(conf, "PCMP", 4) != 0) {
cprintf("SMP: Incorrect MP configuration table signature\n");
return NULL;
}
if (sum(conf, conf->length) != 0) {
cprintf("SMP: Bad MP configuration checksum\n");
return NULL;
}
if (conf->version != 1 && conf->version != 4) {
cprintf("SMP: Unsupported MP version %d\n", conf->version);
return NULL;
}
if ((sum((uint8_t *)conf + conf->length, conf->xlength) + conf->xchecksum) & 0xff) {
cprintf("SMP: Bad MP configuration extended checksum\n");
return NULL;
}
*pmp = mp;
return conf;
}
void
mp_init(void)
{
struct mp *mp;
struct mpconf *conf;
struct mpproc *proc;
uint8_t *p;
unsigned int i;
bootcpu = &cpus[0];
if ((conf = mpconfig(&mp)) == 0)
return;
ismp = 1;
lapicaddr = conf->lapicaddr;
for (p = conf->entries, i = 0; i < conf->entry; i++) {
switch (*p) {
case MPPROC:
proc = (struct mpproc *)p;
if (proc->flags & MPPROC_BOOT)
bootcpu = &cpus[ncpu];
if (ncpu < NCPU) {
cpus[ncpu].cpu_id = ncpu;
ncpu++;
} else {
cprintf("SMP: too many CPUs, CPU %d disabled\n",
proc->apicid);
}
p += sizeof(struct mpproc);
continue;
case MPBUS:
case MPIOAPIC:
case MPIOINTR:
case MPLINTR:
p += 8;
continue;
default:
cprintf("mpinit: unknown config type %x\n", *p);
ismp = 0;
i = conf->entry;
}
}
bootcpu->cpu_status = CPU_STARTED;
if (!ismp) {
// Didn't like what we found; fall back to no MP.
ncpu = 1;
lapicaddr = 0;
cprintf("SMP: configuration not found, SMP disabled\n");
return;
}
cprintf("SMP: CPU %d found %d CPU(s)\n", bootcpu->cpu_id, ncpu);
if (mp->imcrp) {
// [MP 3.2.6.1] If the hardware implements PIC mode,
// switch to getting interrupts from the LAPIC.
cprintf("SMP: Setting IMCR to switch from PIC mode to symmetric I/O mode\n");
outb(0x22, 0x70); // Select IMCR
outb(0x23, inb(0x23) | 1); // Mask external interrupts.
}
}

97
kern/mpentry.S Normal file
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@ -0,0 +1,97 @@
/* See COPYRIGHT for copyright information. */
#include <inc/mmu.h>
#include <inc/memlayout.h>
###################################################################
# entry point for APs
###################################################################
# Each non-boot CPU ("AP") is started up in response to a STARTUP
# IPI from the boot CPU. Section B.4.2 of the Multi-Processor
# Specification says that the AP will start in real mode with CS:IP
# set to XY00:0000, where XY is an 8-bit value sent with the
# STARTUP. Thus this code must start at a 4096-byte boundary.
#
# Because this code sets DS to zero, it must run from an address in
# the low 2^16 bytes of physical memory.
#
# boot_aps() (in init.c) copies this code to MPENTRY_PADDR (which
# satisfies the above restrictions). Then, for each AP, it stores the
# address of the pre-allocated per-core stack in mpentry_kstack, sends
# the STARTUP IPI, and waits for this code to acknowledge that it has
# started (which happens in mp_main in init.c).
#
# This code is similar to boot/boot.S except that
# - it does not need to enable A20
# - it uses MPBOOTPHYS to calculate absolute addresses of its
# symbols, rather than relying on the linker to fill them
#define RELOC(x) ((x) - KERNBASE)
#define MPBOOTPHYS(s) ((s) - mpentry_start + MPENTRY_PADDR)
.set PROT_MODE_CSEG, 0x8 # kernel code segment selector
.set PROT_MODE_DSEG, 0x10 # kernel data segment selector
.code16
.globl mpentry_start
mpentry_start:
cli
xorw %ax, %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %ss
lgdt MPBOOTPHYS(gdtdesc)
movl %cr0, %eax
orl $CR0_PE, %eax
movl %eax, %cr0
ljmpl $(PROT_MODE_CSEG), $(MPBOOTPHYS(start32))
.code32
start32:
movw $(PROT_MODE_DSEG), %ax
movw %ax, %ds
movw %ax, %es
movw %ax, %ss
movw $0, %ax
movw %ax, %fs
movw %ax, %gs
# Set up initial page table. We cannot use kern_pgdir yet because
# we are still running at a low EIP.
movl $(RELOC(entry_pgdir)), %eax
movl %eax, %cr3
# Turn on paging.
movl %cr0, %eax
orl $(CR0_PE|CR0_PG|CR0_WP), %eax
movl %eax, %cr0
# Switch to the per-cpu stack allocated in boot_aps()
movl mpentry_kstack, %esp
movl $0x0, %ebp # nuke frame pointer
# Call mp_main(). (Exercise for the reader: why the indirect call?)
movl $mp_main, %eax
call *%eax
# If mp_main returns (it shouldn't), loop.
spin:
jmp spin
# Bootstrap GDT
.p2align 2 # force 4 byte alignment
gdt:
SEG_NULL # null seg
SEG(STA_X|STA_R, 0x0, 0xffffffff) # code seg
SEG(STA_W, 0x0, 0xffffffff) # data seg
gdtdesc:
.word 0x17 # sizeof(gdt) - 1
.long MPBOOTPHYS(gdt) # address gdt
.globl mpentry_end
mpentry_end:
nop

86
kern/picirq.c Normal file
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@ -0,0 +1,86 @@
/* See COPYRIGHT for copyright information. */
#include <inc/assert.h>
#include <inc/trap.h>
#include <kern/picirq.h>
// Current IRQ mask.
// Initial IRQ mask has interrupt 2 enabled (for slave 8259A).
uint16_t irq_mask_8259A = 0xFFFF & ~(1<<IRQ_SLAVE);
static bool didinit;
/* Initialize the 8259A interrupt controllers. */
void
pic_init(void)
{
didinit = 1;
// mask all interrupts
outb(IO_PIC1+1, 0xFF);
outb(IO_PIC2+1, 0xFF);
// Set up master (8259A-1)
// ICW1: 0001g0hi
// g: 0 = edge triggering, 1 = level triggering
// h: 0 = cascaded PICs, 1 = master only
// i: 0 = no ICW4, 1 = ICW4 required
outb(IO_PIC1, 0x11);
// ICW2: Vector offset
outb(IO_PIC1+1, IRQ_OFFSET);
// ICW3: bit mask of IR lines connected to slave PICs (master PIC),
// 3-bit No of IR line at which slave connects to master(slave PIC).
outb(IO_PIC1+1, 1<<IRQ_SLAVE);
// ICW4: 000nbmap
// n: 1 = special fully nested mode
// b: 1 = buffered mode
// m: 0 = slave PIC, 1 = master PIC
// (ignored when b is 0, as the master/slave role
// can be hardwired).
// a: 1 = Automatic EOI mode
// p: 0 = MCS-80/85 mode, 1 = intel x86 mode
outb(IO_PIC1+1, 0x3);
// Set up slave (8259A-2)
outb(IO_PIC2, 0x11); // ICW1
outb(IO_PIC2+1, IRQ_OFFSET + 8); // ICW2
outb(IO_PIC2+1, IRQ_SLAVE); // ICW3
// NB Automatic EOI mode doesn't tend to work on the slave.
// Linux source code says it's "to be investigated".
outb(IO_PIC2+1, 0x01); // ICW4
// OCW3: 0ef01prs
// ef: 0x = NOP, 10 = clear specific mask, 11 = set specific mask
// p: 0 = no polling, 1 = polling mode
// rs: 0x = NOP, 10 = read IRR, 11 = read ISR
outb(IO_PIC1, 0x68); /* clear specific mask */
outb(IO_PIC1, 0x0a); /* read IRR by default */
outb(IO_PIC2, 0x68); /* OCW3 */
outb(IO_PIC2, 0x0a); /* OCW3 */
if (irq_mask_8259A != 0xFFFF)
irq_setmask_8259A(irq_mask_8259A);
}
void
irq_setmask_8259A(uint16_t mask)
{
int i;
irq_mask_8259A = mask;
if (!didinit)
return;
outb(IO_PIC1+1, (char)mask);
outb(IO_PIC2+1, (char)(mask >> 8));
cprintf("enabled interrupts:");
for (i = 0; i < 16; i++)
if (~mask & (1<<i))
cprintf(" %d", i);
cprintf("\n");
}

28
kern/picirq.h Normal file
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@ -0,0 +1,28 @@
/* See COPYRIGHT for copyright information. */
#ifndef JOS_KERN_PICIRQ_H
#define JOS_KERN_PICIRQ_H
#ifndef JOS_KERNEL
# error "This is a JOS kernel header; user programs should not #include it"
#endif
#define MAX_IRQS 16 // Number of IRQs
// I/O Addresses of the two 8259A programmable interrupt controllers
#define IO_PIC1 0x20 // Master (IRQs 0-7)
#define IO_PIC2 0xA0 // Slave (IRQs 8-15)
#define IRQ_SLAVE 2 // IRQ at which slave connects to master
#ifndef __ASSEMBLER__
#include <inc/types.h>
#include <inc/x86.h>
extern uint16_t irq_mask_8259A;
void pic_init(void);
void irq_setmask_8259A(uint16_t mask);
#endif // !__ASSEMBLER__
#endif // !JOS_KERN_PICIRQ_H

108
kern/pmap.c
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@ -9,6 +9,7 @@
#include <kern/pmap.h>
#include <kern/kclock.h>
#include <kern/env.h>
#include <kern/cpu.h>
// These variables are set by i386_detect_memory()
size_t npages; // Amount of physical memory (in pages)
@ -62,6 +63,7 @@ i386_detect_memory(void)
// Set up memory mappings above UTOP.
// --------------------------------------------------------------
static void mem_init_mp(void);
static void boot_map_region(pde_t *pgdir, uintptr_t va, size_t size, physaddr_t pa, int perm);
static void check_page_free_list(bool only_low_memory);
static void check_page_alloc(void);
@ -207,6 +209,9 @@ mem_init(void)
// Permissions: kernel RW, user NONE
// Your code goes here:
// Initialize the SMP-related parts of the memory map
mem_init_mp();
// Check that the initial page directory has been set up correctly.
check_kern_pgdir();
@ -232,6 +237,31 @@ mem_init(void)
check_page_installed_pgdir();
}
// Modify mappings in kern_pgdir to support SMP
// - Map the per-CPU stacks in the region [KSTACKTOP-PTSIZE, KSTACKTOP)
//
static void
mem_init_mp(void)
{
// Map per-CPU stacks starting at KSTACKTOP, for up to 'NCPU' CPUs.
//
// For CPU i, use the physical memory that 'percpu_kstacks[i]' refers
// to as its kernel stack. CPU i's kernel stack grows down from virtual
// address kstacktop_i = KSTACKTOP - i * (KSTKSIZE + KSTKGAP), and is
// divided into two pieces, just like the single stack you set up in
// mem_init:
// * [kstacktop_i - KSTKSIZE, kstacktop_i)
// -- backed by physical memory
// * [kstacktop_i - (KSTKSIZE + KSTKGAP), kstacktop_i - KSTKSIZE)
// -- not backed; so if the kernel overflows its stack,
// it will fault rather than overwrite another CPU's stack.
// Known as a "guard page".
// Permissions: kernel RW, user NONE
//
// LAB 4: Your code here:
}
// --------------------------------------------------------------
// Tracking of physical pages.
// The 'pages' array has one 'struct PageInfo' entry per physical page.
@ -247,6 +277,10 @@ mem_init(void)
void
page_init(void)
{
// LAB 4:
// Change your code to mark the physical page at MPENTRY_PADDR
// as in use
// The example code here marks all physical pages as free.
// However this is not truly the case. What memory is free?
// 1) Mark physical page 0 as in use.
@ -439,10 +473,45 @@ void
tlb_invalidate(pde_t *pgdir, void *va)
{
// Flush the entry only if we're modifying the current address space.
// For now, there is only one address space, so always invalidate.
if (!curenv || curenv->env_pgdir == pgdir)
invlpg(va);
}
//
// Reserve size bytes in the MMIO region and map [pa,pa+size) at this
// location. Return the base of the reserved region. size does *not*
// have to be multiple of PGSIZE.
//
void *
mmio_map_region(physaddr_t pa, size_t size)
{
// Where to start the next region. Initially, this is the
// beginning of the MMIO region. Because this is static, its
// value will be preserved between calls to mmio_map_region
// (just like nextfree in boot_alloc).
static uintptr_t base = MMIOBASE;
// Reserve size bytes of virtual memory starting at base and
// map physical pages [pa,pa+size) to virtual addresses
// [base,base+size). Since this is device memory and not
// regular DRAM, you'll have to tell the CPU that it isn't
// safe to cache access to this memory. Luckily, the page
// tables provide bits for this purpose; simply create the
// mapping with PTE_PCD|PTE_PWT (cache-disable and
// write-through) in addition to PTE_W. (If you're interested
// in more details on this, see section 10.5 of IA32 volume
// 3A.)
//
// Be sure to round size up to a multiple of PGSIZE and to
// handle if this reservation would overflow MMIOLIM (it's
// okay to simply panic if this happens).
//
// Hint: The staff solution uses boot_map_region.
//
// Your code here:
panic("mmio_map_region not implemented");
}
static uintptr_t user_mem_check_addr;
//
@ -541,6 +610,8 @@ check_page_free_list(bool only_low_memory)
assert(page2pa(pp) != EXTPHYSMEM - PGSIZE);
assert(page2pa(pp) != EXTPHYSMEM);
assert(page2pa(pp) < EXTPHYSMEM || (char *) page2kva(pp) >= first_free_page);
// (new test for lab 4)
assert(page2pa(pp) != MPENTRY_PADDR);
if (page2pa(pp) < EXTPHYSMEM)
++nfree_basemem;
@ -663,9 +734,15 @@ check_kern_pgdir(void)
assert(check_va2pa(pgdir, KERNBASE + i) == i);
// check kernel stack
// (updated in lab 4 to check per-CPU kernel stacks)
for (n = 0; n < NCPU; n++) {
uint32_t base = KSTACKTOP - (KSTKSIZE + KSTKGAP) * (n + 1);
for (i = 0; i < KSTKSIZE; i += PGSIZE)
assert(check_va2pa(pgdir, KSTACKTOP - KSTKSIZE + i) == PADDR(bootstack) + i);
assert(check_va2pa(pgdir, KSTACKTOP - PTSIZE) == ~0);
assert(check_va2pa(pgdir, base + KSTKGAP + i)
== PADDR(percpu_kstacks[n]) + i);
for (i = 0; i < KSTKGAP; i += PGSIZE)
assert(check_va2pa(pgdir, base + i) == ~0);
}
// check PDE permissions
for (i = 0; i < NPDENTRIES; i++) {
@ -674,6 +751,7 @@ check_kern_pgdir(void)
case PDX(KSTACKTOP-1):
case PDX(UPAGES):
case PDX(UENVS):
case PDX(MMIOBASE):
assert(pgdir[i] & PTE_P);
break;
default:
@ -716,6 +794,7 @@ check_page(void)
struct PageInfo *fl;
pte_t *ptep, *ptep1;
void *va;
uintptr_t mm1, mm2;
int i;
extern pde_t entry_pgdir[];
@ -858,6 +937,29 @@ check_page(void)
page_free(pp1);
page_free(pp2);
// test mmio_map_region
mm1 = (uintptr_t) mmio_map_region(0, 4097);
mm2 = (uintptr_t) mmio_map_region(0, 4096);
// check that they're in the right region
assert(mm1 >= MMIOBASE && mm1 + 8192 < MMIOLIM);
assert(mm2 >= MMIOBASE && mm2 + 8192 < MMIOLIM);
// check that they're page-aligned
assert(mm1 % PGSIZE == 0 && mm2 % PGSIZE == 0);
// check that they don't overlap
assert(mm1 + 8192 <= mm2);
// check page mappings
assert(check_va2pa(kern_pgdir, mm1) == 0);
assert(check_va2pa(kern_pgdir, mm1+PGSIZE) == PGSIZE);
assert(check_va2pa(kern_pgdir, mm2) == 0);
assert(check_va2pa(kern_pgdir, mm2+PGSIZE) == ~0);
// check permissions
assert(*pgdir_walk(kern_pgdir, (void*) mm1, 0) & (PTE_W|PTE_PWT|PTE_PCD));
assert(!(*pgdir_walk(kern_pgdir, (void*) mm1, 0) & PTE_U));
// clear the mappings
*pgdir_walk(kern_pgdir, (void*) mm1, 0) = 0;
*pgdir_walk(kern_pgdir, (void*) mm1 + PGSIZE, 0) = 0;
*pgdir_walk(kern_pgdir, (void*) mm2, 0) = 0;
cprintf("check_page() succeeded!\n");
}

2
kern/pmap.h
View File

@ -63,6 +63,8 @@ void page_decref(struct PageInfo *pp);
void tlb_invalidate(pde_t *pgdir, void *va);
void * mmio_map_region(physaddr_t pa, size_t size);
int user_mem_check(struct Env *env, const void *va, size_t len, int perm);
void user_mem_assert(struct Env *env, const void *va, size_t len, int perm);

84
kern/sched.c Normal file
View File

@ -0,0 +1,84 @@
#include <inc/assert.h>
#include <inc/x86.h>
#include <kern/spinlock.h>
#include <kern/env.h>
#include <kern/pmap.h>
#include <kern/monitor.h>
void sched_halt(void);
// Choose a user environment to run and run it.
void
sched_yield(void)
{
struct Env *idle;
// Implement simple round-robin scheduling.
//
// Search through 'envs' for an ENV_RUNNABLE environment in
// circular fashion starting just after the env this CPU was
// last running. Switch to the first such environment found.
//
// If no envs are runnable, but the environment previously
// running on this CPU is still ENV_RUNNING, it's okay to
// choose that environment.
//
// Never choose an environment that's currently running on
// another CPU (env_status == ENV_RUNNING). If there are
// no runnable environments, simply drop through to the code
// below to halt the cpu.
// LAB 4: Your code here.
// sched_halt never returns
sched_halt();
}
// Halt this CPU when there is nothing to do. Wait until the
// timer interrupt wakes it up. This function never returns.
//
void
sched_halt(void)
{
int i;
// For debugging and testing purposes, if there are no runnable
// environments in the system, then drop into the kernel monitor.
for (i = 0; i < NENV; i++) {
if ((envs[i].env_status == ENV_RUNNABLE ||
envs[i].env_status == ENV_RUNNING ||
envs[i].env_status == ENV_DYING))
break;
}
if (i == NENV) {
cprintf("No runnable environments in the system!\n");
while (1)
monitor(NULL);
}
// Mark that no environment is running on this CPU
curenv = NULL;
lcr3(PADDR(kern_pgdir));
// Mark that this CPU is in the HALT state, so that when
// timer interupts come in, we know we should re-acquire the
// big kernel lock
xchg(&thiscpu->cpu_status, CPU_HALTED);
// Release the big kernel lock as if we were "leaving" the kernel
unlock_kernel();
// Reset stack pointer, enable interrupts and then halt.
asm volatile (
"movl $0, %%ebp\n"
"movl %0, %%esp\n"
"pushl $0\n"
"pushl $0\n"
// Uncomment the following line after completing exercise 13
//"sti\n"
"1:\n"
"hlt\n"
"jmp 1b\n"
: : "a" (thiscpu->cpu_ts.ts_esp0));
}

12
kern/sched.h Normal file
View File

@ -0,0 +1,12 @@
/* See COPYRIGHT for copyright information. */
#ifndef JOS_KERN_SCHED_H
#define JOS_KERN_SCHED_H
#ifndef JOS_KERNEL
# error "This is a JOS kernel header; user programs should not #include it"
#endif
// This function does not return.
void sched_yield(void) __attribute__((noreturn));
#endif // !JOS_KERN_SCHED_H

116
kern/spinlock.c Normal file
View File

@ -0,0 +1,116 @@
// Mutual exclusion spin locks.
#include <inc/types.h>
#include <inc/assert.h>
#include <inc/x86.h>
#include <inc/memlayout.h>
#include <inc/string.h>
#include <kern/cpu.h>
#include <kern/spinlock.h>
#include <kern/kdebug.h>
// The big kernel lock
struct spinlock kernel_lock = {
#ifdef DEBUG_SPINLOCK
.name = "kernel_lock"
#endif
};
#ifdef DEBUG_SPINLOCK
// Record the current call stack in pcs[] by following the %ebp chain.
static void
get_caller_pcs(uint32_t pcs[])
{
uint32_t *ebp;
int i;
ebp = (uint32_t *)read_ebp();
for (i = 0; i < 10; i++){
if (ebp == 0 || ebp < (uint32_t *)ULIM)
break;
pcs[i] = ebp[1]; // saved %eip
ebp = (uint32_t *)ebp[0]; // saved %ebp
}
for (; i < 10; i++)
pcs[i] = 0;
}
// Check whether this CPU is holding the lock.
static int
holding(struct spinlock *lock)
{
return lock->locked && lock->cpu == thiscpu;
}
#endif
void
__spin_initlock(struct spinlock *lk, char *name)
{
lk->locked = 0;
#ifdef DEBUG_SPINLOCK
lk->name = name;
lk->cpu = 0;
#endif
}
// Acquire the lock.
// Loops (spins) until the lock is acquired.
// Holding a lock for a long time may cause
// other CPUs to waste time spinning to acquire it.
void
spin_lock(struct spinlock *lk)
{
#ifdef DEBUG_SPINLOCK
if (holding(lk))
panic("CPU %d cannot acquire %s: already holding", cpunum(), lk->name);
#endif
// The xchg is atomic.
// It also serializes, so that reads after acquire are not
// reordered before it.
while (xchg(&lk->locked, 1) != 0)
asm volatile ("pause");
// Record info about lock acquisition for debugging.
#ifdef DEBUG_SPINLOCK
lk->cpu = thiscpu;
get_caller_pcs(lk->pcs);
#endif
}
// Release the lock.
void
spin_unlock(struct spinlock *lk)
{
#ifdef DEBUG_SPINLOCK
if (!holding(lk)) {
int i;
uint32_t pcs[10];
// Nab the acquiring EIP chain before it gets released
memmove(pcs, lk->pcs, sizeof pcs);
cprintf("CPU %d cannot release %s: held by CPU %d\nAcquired at:",
cpunum(), lk->name, lk->cpu->cpu_id);
for (i = 0; i < 10 && pcs[i]; i++) {
struct Eipdebuginfo info;
if (debuginfo_eip(pcs[i], &info) >= 0)
cprintf(" %08x %s:%d: %.*s+%x\n", pcs[i],
info.eip_file, info.eip_line,
info.eip_fn_namelen, info.eip_fn_name,
pcs[i] - info.eip_fn_addr);
else
cprintf(" %08x\n", pcs[i]);
}
panic("spin_unlock");
}
lk->pcs[0] = 0;
lk->cpu = 0;
#endif
// The xchg instruction is atomic (i.e. uses the "lock" prefix) with
// respect to any other instruction which references the same memory.
// x86 CPUs will not reorder loads/stores across locked instructions
// (vol 3, 8.2.2). Because xchg() is implemented using asm volatile,
// gcc will not reorder C statements across the xchg.
xchg(&lk->locked, 0);
}

48
kern/spinlock.h Normal file
View File

@ -0,0 +1,48 @@
#ifndef JOS_INC_SPINLOCK_H
#define JOS_INC_SPINLOCK_H
#include <inc/types.h>
// Comment this to disable spinlock debugging
#define DEBUG_SPINLOCK
// Mutual exclusion lock.
struct spinlock {
unsigned locked; // Is the lock held?
#ifdef DEBUG_SPINLOCK
// For debugging:
char *name; // Name of lock.
struct CpuInfo *cpu; // The CPU holding the lock.
uintptr_t pcs[10]; // The call stack (an array of program counters)
// that locked the lock.
#endif
};
void __spin_initlock(struct spinlock *lk, char *name);
void spin_lock(struct spinlock *lk);
void spin_unlock(struct spinlock *lk);
#define spin_initlock(lock) __spin_initlock(lock, #lock)
extern struct spinlock kernel_lock;
static inline void
lock_kernel(void)
{
spin_lock(&kernel_lock);
}
static inline void
unlock_kernel(void)
{
spin_unlock(&kernel_lock);
// Normally we wouldn't need to do this, but QEMU only runs
// one CPU at a time and has a long time-slice. Without the
// pause, this CPU is likely to reacquire the lock before
// another CPU has even been given a chance to acquire it.
asm volatile("pause");
}
#endif

201
kern/syscall.c
View File

@ -10,6 +10,7 @@
#include <kern/trap.h>
#include <kern/syscall.h>
#include <kern/console.h>
#include <kern/sched.h>
// Print a string to the system console.
// The string is exactly 'len' characters long.
@ -62,6 +63,206 @@ sys_env_destroy(envid_t envid)
return 0;
}
// Deschedule current environment and pick a different one to run.
static void
sys_yield(void)
{
sched_yield();
}
// Allocate a new environment.
// Returns envid of new environment, or < 0 on error. Errors are:
// -E_NO_FREE_ENV if no free environment is available.
// -E_NO_MEM on memory exhaustion.
static envid_t
sys_exofork(void)
{
// Create the new environment with env_alloc(), from kern/env.c.
// It should be left as env_alloc created it, except that
// status is set to ENV_NOT_RUNNABLE, and the register set is copied
// from the current environment -- but tweaked so sys_exofork
// will appear to return 0.
// LAB 4: Your code here.
panic("sys_exofork not implemented");
}
// Set envid's env_status to status, which must be ENV_RUNNABLE
// or ENV_NOT_RUNNABLE.
//
// Returns 0 on success, < 0 on error. Errors are:
// -E_BAD_ENV if environment envid doesn't currently exist,
// or the caller doesn't have permission to change envid.
// -E_INVAL if status is not a valid status for an environment.
static int
sys_env_set_status(envid_t envid, int status)
{
// Hint: Use the 'envid2env' function from kern/env.c to translate an
// envid to a struct Env.
// You should set envid2env's third argument to 1, which will
// check whether the current environment has permission to set
// envid's status.
// LAB 4: Your code here.
panic("sys_env_set_status not implemented");
}
// Set the page fault upcall for 'envid' by modifying the corresponding struct
// Env's 'env_pgfault_upcall' field. When 'envid' causes a page fault, the
// kernel will push a fault record onto the exception stack, then branch to
// 'func'.
//
// Returns 0 on success, < 0 on error. Errors are:
// -E_BAD_ENV if environment envid doesn't currently exist,
// or the caller doesn't have permission to change envid.
static int
sys_env_set_pgfault_upcall(envid_t envid, void *func)
{
// LAB 4: Your code here.
panic("sys_env_set_pgfault_upcall not implemented");
}
// Allocate a page of memory and map it at 'va' with permission
// 'perm' in the address space of 'envid'.
// The page's contents are set to 0.
// If a page is already mapped at 'va', that page is unmapped as a
// side effect.
//
// perm -- PTE_U | PTE_P must be set, PTE_AVAIL | PTE_W may or may not be set,
// but no other bits may be set. See PTE_SYSCALL in inc/mmu.h.
//
// Return 0 on success, < 0 on error. Errors are:
// -E_BAD_ENV if environment envid doesn't currently exist,
// or the caller doesn't have permission to change envid.
// -E_INVAL if va >= UTOP, or va is not page-aligned.
// -E_INVAL if perm is inappropriate (see above).
// -E_NO_MEM if there's no memory to allocate the new page,
// or to allocate any necessary page tables.
static int
sys_page_alloc(envid_t envid, void *va, int perm)
{
// Hint: This function is a wrapper around page_alloc() and
// page_insert() from kern/pmap.c.
// Most of the new code you write should be to check the
// parameters for correctness.
// If page_insert() fails, remember to free the page you
// allocated!
// LAB 4: Your code here.
panic("sys_page_alloc not implemented");
}
// Map the page of memory at 'srcva' in srcenvid's address space
// at 'dstva' in dstenvid's address space with permission 'perm'.
// Perm has the same restrictions as in sys_page_alloc, except
// that it also must not grant write access to a read-only
// page.
//
// Return 0 on success, < 0 on error. Errors are:
// -E_BAD_ENV if srcenvid and/or dstenvid doesn't currently exist,
// or the caller doesn't have permission to change one of them.
// -E_INVAL if srcva >= UTOP or srcva is not page-aligned,
// or dstva >= UTOP or dstva is not page-aligned.
// -E_INVAL is srcva is not mapped in srcenvid's address space.
// -E_INVAL if perm is inappropriate (see sys_page_alloc).
// -E_INVAL if (perm & PTE_W), but srcva is read-only in srcenvid's
// address space.
// -E_NO_MEM if there's no memory to allocate any necessary page tables.
static int
sys_page_map(envid_t srcenvid, void *srcva,
envid_t dstenvid, void *dstva, int perm)
{
// Hint: This function is a wrapper around page_lookup() and
// page_insert() from kern/pmap.c.
// Again, most of the new code you write should be to check the
// parameters for correctness.
// Use the third argument to page_lookup() to
// check the current permissions on the page.
// LAB 4: Your code here.
panic("sys_page_map not implemented");
}
// Unmap the page of memory at 'va' in the address space of 'envid'.
// If no page is mapped, the function silently succeeds.
//
// Return 0 on success, < 0 on error. Errors are:
// -E_BAD_ENV if environment envid doesn't currently exist,
// or the caller doesn't have permission to change envid.
// -E_INVAL if va >= UTOP, or va is not page-aligned.
static int
sys_page_unmap(envid_t envid, void *va)
{
// Hint: This function is a wrapper around page_remove().
// LAB 4: Your code here.
panic("sys_page_unmap not implemented");
}
// Try to send 'value' to the target env 'envid'.
// If srcva < UTOP, then also send page currently mapped at 'srcva',
// so that receiver gets a duplicate mapping of the same page.
//
// The send fails with a return value of -E_IPC_NOT_RECV if the
// target is not blocked, waiting for an IPC.
//
// The send also can fail for the other reasons listed below.
//
// Otherwise, the send succeeds, and the target's ipc fields are
// updated as follows:
// env_ipc_recving is set to 0 to block future sends;
// env_ipc_from is set to the sending envid;
// env_ipc_value is set to the 'value' parameter;
// env_ipc_perm is set to 'perm' if a page was transferred, 0 otherwise.
// The target environment is marked runnable again, returning 0
// from the paused sys_ipc_recv system call. (Hint: does the
// sys_ipc_recv function ever actually return?)
//
// If the sender wants to send a page but the receiver isn't asking for one,
// then no page mapping is transferred, but no error occurs.
// The ipc only happens when no errors occur.
//
// Returns 0 on success, < 0 on error.
// Errors are:
// -E_BAD_ENV if environment envid doesn't currently exist.
// (No need to check permissions.)
// -E_IPC_NOT_RECV if envid is not currently blocked in sys_ipc_recv,
// or another environment managed to send first.
// -E_INVAL if srcva < UTOP but srcva is not page-aligned.
// -E_INVAL if srcva < UTOP and perm is inappropriate
// (see sys_page_alloc).
// -E_INVAL if srcva < UTOP but srcva is not mapped in the caller's
// address space.
// -E_INVAL if (perm & PTE_W), but srcva is read-only in the
// current environment's address space.
// -E_NO_MEM if there's not enough memory to map srcva in envid's
// address space.
static int
sys_ipc_try_send(envid_t envid, uint32_t value, void *srcva, unsigned perm)
{
// LAB 4: Your code here.
panic("sys_ipc_try_send not implemented");
}
// Block until a value is ready. Record that you want to receive
// using the env_ipc_recving and env_ipc_dstva fields of struct Env,
// mark yourself not runnable, and then give up the CPU.
//
// If 'dstva' is < UTOP, then you are willing to receive a page of data.
// 'dstva' is the virtual address at which the sent page should be mapped.
//
// This function only returns on error, but the system call will eventually
// return 0 on success.
// Return < 0 on error. Errors are:
// -E_INVAL if dstva < UTOP but dstva is not page-aligned.
static int
sys_ipc_recv(void *dstva)
{
// LAB 4: Your code here.
panic("sys_ipc_recv not implemented");
return 0;
}
// Dispatches to the correct kernel function, passing the arguments.
int32_t
syscall(uint32_t syscallno, uint32_t a1, uint32_t a2, uint32_t a3, uint32_t a4, uint32_t a5)

107
kern/trap.c
View File

@ -8,6 +8,11 @@
#include <kern/monitor.h>
#include <kern/env.h>
#include <kern/syscall.h>
#include <kern/sched.h>
#include <kern/kclock.h>
#include <kern/picirq.h>
#include <kern/cpu.h>
#include <kern/spinlock.h>
static struct Taskstate ts;
@ -55,6 +60,8 @@ static const char *trapname(int trapno)
return excnames[trapno];
if (trapno == T_SYSCALL)
return "System call";
if (trapno >= IRQ_OFFSET && trapno < IRQ_OFFSET + 16)
return "Hardware Interrupt";
return "(unknown trap)";
}
@ -74,6 +81,31 @@ trap_init(void)
void
trap_init_percpu(void)
{
// The example code here sets up the Task State Segment (TSS) and
// the TSS descriptor for CPU 0. But it is incorrect if we are
// running on other CPUs because each CPU has its own kernel stack.
// Fix the code so that it works for all CPUs.
//
// Hints:
// - The macro "thiscpu" always refers to the current CPU's
// struct CpuInfo;
// - The ID of the current CPU is given by cpunum() or
// thiscpu->cpu_id;
// - Use "thiscpu->cpu_ts" as the TSS for the current CPU,
// rather than the global "ts" variable;
// - Use gdt[(GD_TSS0 >> 3) + i] for CPU i's TSS descriptor;
// - You mapped the per-CPU kernel stacks in mem_init_mp()
// - Initialize cpu_ts.ts_iomb to prevent unauthorized environments
// from doing IO (0 is not the correct value!)
//
// ltr sets a 'busy' flag in the TSS selector, so if you
// accidentally load the same TSS on more than one CPU, you'll
// get a triple fault. If you set up an individual CPU's TSS
// wrong, you may not get a fault until you try to return from
// user space on that CPU.
//
// LAB 4: Your code here:
// Setup a TSS so that we get the right stack
// when we trap to the kernel.
ts.ts_esp0 = KSTACKTOP;
@ -96,7 +128,7 @@ trap_init_percpu(void)
void
print_trapframe(struct Trapframe *tf)
{
cprintf("TRAP frame at %p\n", tf);
cprintf("TRAP frame at %p from CPU %d\n", tf, cpunum());
print_regs(&tf->tf_regs);
cprintf(" es 0x----%04x\n", tf->tf_es);
cprintf(" ds 0x----%04x\n", tf->tf_ds);
@ -145,6 +177,19 @@ trap_dispatch(struct Trapframe *tf)
// Handle processor exceptions.
// LAB 3: Your code here.
// Handle spurious interrupts
// The hardware sometimes raises these because of noise on the
// IRQ line or other reasons. We don't care.
if (tf->tf_trapno == IRQ_OFFSET + IRQ_SPURIOUS) {
cprintf("Spurious interrupt on irq 7\n");
print_trapframe(tf);
return;
}
// Handle clock interrupts. Don't forget to acknowledge the
// interrupt using lapic_eoi() before calling the scheduler!
// LAB 4: Your code here.
// Unexpected trap: The user process or the kernel has a bug.
print_trapframe(tf);
if (tf->tf_cs == GD_KT)
@ -162,17 +207,34 @@ trap(struct Trapframe *tf)
// of GCC rely on DF being clear
asm volatile("cld" ::: "cc");
// Halt the CPU if some other CPU has called panic()
extern char *panicstr;
if (panicstr)
asm volatile("hlt");
// Re-acqurie the big kernel lock if we were halted in
// sched_yield()
if (xchg(&thiscpu->cpu_status, CPU_STARTED) == CPU_HALTED)
lock_kernel();
// Check that interrupts are disabled. If this assertion
// fails, DO NOT be tempted to fix it by inserting a "cli" in
// the interrupt path.
assert(!(read_eflags() & FL_IF));
cprintf("Incoming TRAP frame at %p\n", tf);
if ((tf->tf_cs & 3) == 3) {
// Trapped from user mode.
// Acquire the big kernel lock before doing any
// serious kernel work.
// LAB 4: Your code here.
assert(curenv);
// Garbage collect if current enviroment is a zombie
if (curenv->env_status == ENV_DYING) {
env_free(curenv);
curenv = NULL;
sched_yield();
}
// Copy trap frame (which is currently on the stack)
// into 'curenv->env_tf', so that running the environment
// will restart at the trap point.
@ -188,9 +250,13 @@ trap(struct Trapframe *tf)
// Dispatch based on what type of trap occurred
trap_dispatch(tf);
// Return to the current environment, which should be running.
assert(curenv && curenv->env_status == ENV_RUNNING);
// If we made it to this point, then no other environment was
// scheduled, so we should return to the current environment
// if doing so makes sense.
if (curenv && curenv->env_status == ENV_RUNNING)
env_run(curenv);
else
sched_yield();
}
@ -209,6 +275,37 @@ page_fault_handler(struct Trapframe *tf)
// We've already handled kernel-mode exceptions, so if we get here,
// the page fault happened in user mode.
// Call the environment's page fault upcall, if one exists. Set up a
// page fault stack frame on the user exception stack (below
// UXSTACKTOP), then branch to curenv->env_pgfault_upcall.
//
// The page fault upcall might cause another page fault, in which case
// we branch to the page fault upcall recursively, pushing another
// page fault stack frame on top of the user exception stack.
//
// It is convenient for our code which returns from a page fault
// (lib/pfentry.S) to have one word of scratch space at the top of the
// trap-time stack; it allows us to more easily restore the eip/esp. In
// the non-recursive case, we don't have to worry about this because
// the top of the regular user stack is free. In the recursive case,
// this means we have to leave an extra word between the current top of
// the exception stack and the new stack frame because the exception
// stack _is_ the trap-time stack.
//
// If there's no page fault upcall, the environment didn't allocate a
// page for its exception stack or can't write to it, or the exception
// stack overflows, then destroy the environment that caused the fault.
// Note that the grade script assumes you will first check for the page
// fault upcall and print the "user fault va" message below if there is
// none. The remaining three checks can be combined into a single test.
//
// Hints:
// user_mem_assert() and env_run() are useful here.
// To change what the user environment runs, modify 'curenv->env_tf'
// (the 'tf' variable points at 'curenv->env_tf').
// LAB 4: Your code here.
// Destroy the environment that caused the fault.
cprintf("[%08x] user fault va %08x ip %08x\n",
curenv->env_id, fault_va, tf->tf_eip);

1
kern/trapentry.S
View File

@ -4,6 +4,7 @@
#include <inc/memlayout.h>
#include <inc/trap.h>
#include <kern/picirq.h>
###################################################################

5
lib/Makefrag
View File

@ -10,6 +10,11 @@ LIB_SRCFILES := lib/console.c \
lib/string.c \
lib/syscall.c
LIB_SRCFILES := $(LIB_SRCFILES) \
lib/pgfault.c \
lib/pfentry.S \
lib/fork.c \
lib/ipc.c

2
lib/console.c
View File

@ -18,7 +18,7 @@ getchar(void)
int r;
// sys_cgetc does not block, but getchar should.
while ((r = sys_cgetc()) == 0)
;
sys_yield();
return r;
}

90
lib/fork.c Normal file
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@ -0,0 +1,90 @@
// implement fork from user space
#include <inc/string.h>
#include <inc/lib.h>
// PTE_COW marks copy-on-write page table entries.
// It is one of the bits explicitly allocated to user processes (PTE_AVAIL).
#define PTE_COW 0x800
//
// Custom page fault handler - if faulting page is copy-on-write,
// map in our own private writable copy.
//
static void
pgfault(struct UTrapframe *utf)
{
void *addr = (void *) utf->utf_fault_va;
uint32_t err = utf->utf_err;
int r;
// Check that the faulting access was (1) a write, and (2) to a
// copy-on-write page. If not, panic.
// Hint:
// Use the read-only page table mappings at uvpt
// (see <inc/memlayout.h>).
// LAB 4: Your code here.
// Allocate a new page, map it at a temporary location (PFTEMP),
// copy the data from the old page to the new page, then move the new
// page to the old page's address.
// Hint:
// You should make three system calls.
// LAB 4: Your code here.
panic("pgfault not implemented");
}
//
// Map our virtual page pn (address pn*PGSIZE) into the target envid
// at the same virtual address. If the page is writable or copy-on-write,
// the new mapping must be created copy-on-write, and then our mapping must be
// marked copy-on-write as well. (Exercise: Why do we need to mark ours
// copy-on-write again if it was already copy-on-write at the beginning of
// this function?)
//
// Returns: 0 on success, < 0 on error.
// It is also OK to panic on error.
//
static int
duppage(envid_t envid, unsigned pn)
{
int r;
// LAB 4: Your code here.
panic("duppage not implemented");
return 0;
}
//
// User-level fork with copy-on-write.
// Set up our page fault handler appropriately.
// Create a child.
// Copy our address space and page fault handler setup to the child.
// Then mark the child as runnable and return.
//
// Returns: child's envid to the parent, 0 to the child, < 0 on error.
// It is also OK to panic on error.
//
// Hint:
// Use uvpd, uvpt, and duppage.
// Remember to fix "thisenv" in the child process.
// Neither user exception stack should ever be marked copy-on-write,
// so you must allocate a new page for the child's user exception stack.
//
envid_t
fork(void)
{
// LAB 4: Your code here.
panic("fork not implemented");
}
// Challenge!
int
sfork(void)
{
panic("sfork not implemented");
return -E_INVAL;
}

56
lib/ipc.c Normal file
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@ -0,0 +1,56 @@
// User-level IPC library routines
#include <inc/lib.h>
// Receive a value via IPC and return it.
// If 'pg' is nonnull, then any page sent by the sender will be mapped at
// that address.
// If 'from_env_store' is nonnull, then store the IPC sender's envid in
// *from_env_store.
// If 'perm_store' is nonnull, then store the IPC sender's page permission
// in *perm_store (this is nonzero iff a page was successfully
// transferred to 'pg').
// If the system call fails, then store 0 in *fromenv and *perm (if
// they're nonnull) and return the error.
// Otherwise, return the value sent by the sender
//
// Hint:
// Use 'thisenv' to discover the value and who sent it.
// If 'pg' is null, pass sys_ipc_recv a value that it will understand
// as meaning "no page". (Zero is not the right value, since that's
// a perfectly valid place to map a page.)
int32_t
ipc_recv(envid_t *from_env_store, void *pg, int *perm_store)
{
// LAB 4: Your code here.
panic("ipc_recv not implemented");
return 0;
}
// Send 'val' (and 'pg' with 'perm', if 'pg' is nonnull) to 'toenv'.
// This function keeps trying until it succeeds.
// It should panic() on any error other than -E_IPC_NOT_RECV.
//
// Hint:
// Use sys_yield() to be CPU-friendly.
// If 'pg' is null, pass sys_ipc_try_send a value that it will understand
// as meaning "no page". (Zero is not the right value.)
void
ipc_send(envid_t to_env, uint32_t val, void *pg, int perm)
{
// LAB 4: Your code here.
panic("ipc_send not implemented");
}
// Find the first environment of the given type. We'll use this to
// find special environments.
// Returns 0 if no such environment exists.
envid_t
ipc_find_env(enum EnvType type)
{
int i;
for (i = 0; i < NENV; i++)
if (envs[i].env_type == type)
return envs[i].env_id;
return 0;
}

82
lib/pfentry.S Normal file
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@ -0,0 +1,82 @@
#include <inc/mmu.h>
#include <inc/memlayout.h>
// Page fault upcall entrypoint.
// This is where we ask the kernel to redirect us to whenever we cause
// a page fault in user space (see the call to sys_set_pgfault_handler
// in pgfault.c).
//
// When a page fault actually occurs, the kernel switches our ESP to
// point to the user exception stack if we're not already on the user
// exception stack, and then it pushes a UTrapframe onto our user
// exception stack:
//
// trap-time esp
// trap-time eflags
// trap-time eip
// utf_regs.reg_eax
// ...
// utf_regs.reg_esi
// utf_regs.reg_edi
// utf_err (error code)
// utf_fault_va <-- %esp
//
// If this is a recursive fault, the kernel will reserve for us a
// blank word above the trap-time esp for scratch work when we unwind
// the recursive call.
//
// We then have call up to the appropriate page fault handler in C
// code, pointed to by the global variable '_pgfault_handler'.
.text
.globl _pgfault_upcall
_pgfault_upcall:
// Call the C page fault handler.
pushl %esp // function argument: pointer to UTF
movl _pgfault_handler, %eax
call *%eax
addl $4, %esp // pop function argument
// Now the C page fault handler has returned and you must return
// to the trap time state.
// Push trap-time %eip onto the trap-time stack.
//
// Explanation:
// We must prepare the trap-time stack for our eventual return to
// re-execute the instruction that faulted.
// Unfortunately, we can't return directly from the exception stack:
// We can't call 'jmp', since that requires that we load the address
// into a register, and all registers must have their trap-time
// values after the return.
// We can't call 'ret' from the exception stack either, since if we
// did, %esp would have the wrong value.
// So instead, we push the trap-time %eip onto the *trap-time* stack!
// Below we'll switch to that stack and call 'ret', which will
// restore %eip to its pre-fault value.
//
// In the case of a recursive fault on the exception stack,
// note that the word we're pushing now will fit in the
// blank word that the kernel reserved for us.
//
// Throughout the remaining code, think carefully about what
// registers are available for intermediate calculations. You
// may find that you have to rearrange your code in non-obvious
// ways as registers become unavailable as scratch space.
//
// LAB 4: Your code here.
// Restore the trap-time registers. After you do this, you
// can no longer modify any general-purpose registers.
// LAB 4: Your code here.
// Restore eflags from the stack. After you do this, you can
// no longer use arithmetic operations or anything else that
// modifies eflags.
// LAB 4: Your code here.
// Switch back to the adjusted trap-time stack.
// LAB 4: Your code here.
// Return to re-execute the instruction that faulted.
// LAB 4: Your code here.

37
lib/pgfault.c Normal file
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@ -0,0 +1,37 @@
// User-level page fault handler support.
// Rather than register the C page fault handler directly with the
// kernel as the page fault handler, we register the assembly language
// wrapper in pfentry.S, which in turns calls the registered C
// function.
#include <inc/lib.h>
// Assembly language pgfault entrypoint defined in lib/pfentry.S.
extern void _pgfault_upcall(void);
// Pointer to currently installed C-language pgfault handler.
void (*_pgfault_handler)(struct UTrapframe *utf);
//
// Set the page fault handler function.
// If there isn't one yet, _pgfault_handler will be 0.
// The first time we register a handler, we need to
// allocate an exception stack (one page of memory with its top
// at UXSTACKTOP), and tell the kernel to call the assembly-language
// _pgfault_upcall routine when a page fault occurs.
//
void
set_pgfault_handler(void (*handler)(struct UTrapframe *utf))
{
int r;
if (_pgfault_handler == 0) {
// First time through!
// LAB 4: Your code here.
panic("set_pgfault_handler not implemented");
}
// Save handler pointer for assembly to call.
_pgfault_handler = handler;
}

2
lib/printfmt.c
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@ -26,6 +26,8 @@ static const char * const error_string[MAXERROR] =
[E_NO_MEM] = "out of memory",
[E_NO_FREE_ENV] = "out of environments",
[E_FAULT] = "segmentation fault",
[E_IPC_NOT_RECV]= "env is not recving",
[E_EOF] = "unexpected end of file",
};
/*

50
lib/syscall.c
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@ -61,3 +61,53 @@ sys_getenvid(void)
return syscall(SYS_getenvid, 0, 0, 0, 0, 0, 0);
}
void
sys_yield(void)
{
syscall(SYS_yield, 0, 0, 0, 0, 0, 0);
}
int
sys_page_alloc(envid_t envid, void *va, int perm)
{
return syscall(SYS_page_alloc, 1, envid, (uint32_t) va, perm, 0, 0);
}
int
sys_page_map(envid_t srcenv, void *srcva, envid_t dstenv, void *dstva, int perm)
{
return syscall(SYS_page_map, 1, srcenv, (uint32_t) srcva, dstenv, (uint32_t) dstva, perm);
}
int
sys_page_unmap(envid_t envid, void *va)
{
return syscall(SYS_page_unmap, 1, envid, (uint32_t) va, 0, 0, 0);
}
// sys_exofork is inlined in lib.h
int
sys_env_set_status(envid_t envid, int status)
{
return syscall(SYS_env_set_status, 1, envid, status, 0, 0, 0);
}
int
sys_env_set_pgfault_upcall(envid_t envid, void *upcall)
{
return syscall(SYS_env_set_pgfault_upcall, 1, envid, (uint32_t) upcall, 0, 0, 0);
}
int
sys_ipc_try_send(envid_t envid, uint32_t value, void *srcva, int perm)
{
return syscall(SYS_ipc_try_send, 0, envid, value, (uint32_t) srcva, perm, 0);
}
int
sys_ipc_recv(void *dstva)
{
return syscall(SYS_ipc_recv, 1, (uint32_t)dstva, 0, 0, 0, 0);
}

80
user/dumbfork.c Normal file
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@ -0,0 +1,80 @@
// Ping-pong a counter between two processes.
// Only need to start one of these -- splits into two, crudely.
#include <inc/string.h>
#include <inc/lib.h>
envid_t dumbfork(void);
void
umain(int argc, char **argv)
{
envid_t who;
int i;
// fork a child process
who = dumbfork();
// print a message and yield to the other a few times
for (i = 0; i < (who ? 10 : 20); i++) {
cprintf("%d: I am the %s!\n", i, who ? "parent" : "child");
sys_yield();
}
}
void
duppage(envid_t dstenv, void *addr)
{
int r;
// This is NOT what you should do in your fork.
if ((r = sys_page_alloc(dstenv, addr, PTE_P|PTE_U|PTE_W)) < 0)
panic("sys_page_alloc: %e", r);
if ((r = sys_page_map(dstenv, addr, 0, UTEMP, PTE_P|PTE_U|PTE_W)) < 0)
panic("sys_page_map: %e", r);
memmove(UTEMP, addr, PGSIZE);
if ((r = sys_page_unmap(0, UTEMP)) < 0)
panic("sys_page_unmap: %e", r);
}
envid_t
dumbfork(void)
{
envid_t envid;
uint8_t *addr;
int r;
extern unsigned char end[];
// Allocate a new child environment.
// The kernel will initialize it with a copy of our register state,
// so that the child will appear to have called sys_exofork() too -
// except that in the child, this "fake" call to sys_exofork()
// will return 0 instead of the envid of the child.
envid = sys_exofork();
if (envid < 0)
panic("sys_exofork: %e", envid);
if (envid == 0) {
// We're the child.
// The copied value of the global variable 'thisenv'
// is no longer valid (it refers to the parent!).
// Fix it and return 0.
thisenv = &envs[ENVX(sys_getenvid())];
return 0;
}
// We're the parent.
// Eagerly copy our entire address space into the child.
// This is NOT what you should do in your fork implementation.
for (addr = (uint8_t*) UTEXT; addr < end; addr += PGSIZE)
duppage(envid, addr);
// Also copy the stack we are currently running on.
duppage(envid, ROUNDDOWN(&addr, PGSIZE));
// Start the child environment running
if ((r = sys_env_set_status(envid, ENV_RUNNABLE)) < 0)
panic("sys_env_set_status: %e", r);
return envid;
}

25
user/fairness.c Normal file
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@ -0,0 +1,25 @@
// Demonstrate lack of fairness in IPC.
// Start three instances of this program as envs 1, 2, and 3.
// (user/idle is env 0).
#include <inc/lib.h>
void
umain(int argc, char **argv)
{
envid_t who, id;
id = sys_getenvid();
if (thisenv == &envs[1]) {
while (1) {
ipc_recv(&who, 0, 0);
cprintf("%x recv from %x\n", id, who);
}
} else {
cprintf("%x loop sending to %x\n", id, envs[1].env_id);
while (1)
ipc_send(envs[1].env_id, 0, 0, 0);
}
}

24
user/faultalloc.c Normal file
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@ -0,0 +1,24 @@
// test user-level fault handler -- alloc pages to fix faults
#include <inc/lib.h>
void
handler(struct UTrapframe *utf)
{
int r;
void *addr = (void*)utf->utf_fault_va;
cprintf("fault %x\n", addr);
if ((r = sys_page_alloc(0, ROUNDDOWN(addr, PGSIZE),
PTE_P|PTE_U|PTE_W)) < 0)
panic("allocating at %x in page fault handler: %e", addr, r);
snprintf((char*) addr, 100, "this string was faulted in at %x", addr);
}
void
umain(int argc, char **argv)
{
set_pgfault_handler(handler);
cprintf("%s\n", (char*)0xDeadBeef);
cprintf("%s\n", (char*)0xCafeBffe);
}

24
user/faultallocbad.c Normal file
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@ -0,0 +1,24 @@
// test user-level fault handler -- alloc pages to fix faults
// doesn't work because we sys_cputs instead of cprintf (exercise: why?)
#include <inc/lib.h>
void
handler(struct UTrapframe *utf)
{
int r;
void *addr = (void*)utf->utf_fault_va;
cprintf("fault %x\n", addr);
if ((r = sys_page_alloc(0, ROUNDDOWN(addr, PGSIZE),
PTE_P|PTE_U|PTE_W)) < 0)
panic("allocating at %x in page fault handler: %e", addr, r);
snprintf((char*) addr, 100, "this string was faulted in at %x", addr);
}
void
umain(int argc, char **argv)
{
set_pgfault_handler(handler);
sys_cputs((char*)0xDEADBEEF, 4);
}

14
user/faultbadhandler.c Normal file
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@ -0,0 +1,14 @@
// test bad pointer for user-level fault handler
// this is going to fault in the fault handler accessing eip (always!)
// so eventually the kernel kills it (PFM_KILL) because
// we outrun the stack with invocations of the user-level handler
#include <inc/lib.h>
void
umain(int argc, char **argv)
{
sys_page_alloc(0, (void*) (UXSTACKTOP - PGSIZE), PTE_P|PTE_U|PTE_W);
sys_env_set_pgfault_upcall(0, (void*) 0xDeadBeef);
*(int*)0 = 0;
}

19
user/faultdie.c Normal file
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@ -0,0 +1,19 @@
// test user-level fault handler -- just exit when we fault
#include <inc/lib.h>
void
handler(struct UTrapframe *utf)
{
void *addr = (void*)utf->utf_fault_va;
uint32_t err = utf->utf_err;
cprintf("i faulted at va %x, err %x\n", addr, err & 7);
sys_env_destroy(sys_getenvid());
}
void
umain(int argc, char **argv)
{
set_pgfault_handler(handler);
*(int*)0xDeadBeef = 0;
}

11
user/faultevilhandler.c Normal file
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@ -0,0 +1,11 @@
// test evil pointer for user-level fault handler
#include <inc/lib.h>
void
umain(int argc, char **argv)
{
sys_page_alloc(0, (void*) (UXSTACKTOP - PGSIZE), PTE_P|PTE_U|PTE_W);
sys_env_set_pgfault_upcall(0, (void*) 0xF0100020);
*(int*)0 = 0;
}

12
user/faultnostack.c Normal file
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@ -0,0 +1,12 @@
// test user fault handler being called with no exception stack mapped
#include <inc/lib.h>
void _pgfault_upcall();
void
umain(int argc, char **argv)
{
sys_env_set_pgfault_upcall(0, (void*) _pgfault_upcall);
*(int*)0 = 0;
}

146
user/faultregs.c Normal file
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@ -0,0 +1,146 @@
// test register restore on user-level page fault return
#include <inc/lib.h>
struct regs
{
struct PushRegs regs;
uintptr_t eip;
uint32_t eflags;
uintptr_t esp;
};
#define SAVE_REGS(base) \
"\tmovl %%edi, "base"+0x00\n" \
"\tmovl %%esi, "base"+0x04\n" \
"\tmovl %%ebp, "base"+0x08\n" \
"\tmovl %%ebx, "base"+0x10\n" \
"\tmovl %%edx, "base"+0x14\n" \
"\tmovl %%ecx, "base"+0x18\n" \
"\tmovl %%eax, "base"+0x1c\n" \
"\tmovl %%esp, "base"+0x28\n"
#define LOAD_REGS(base) \
"\tmovl "base"+0x00, %%edi\n" \
"\tmovl "base"+0x04, %%esi\n" \
"\tmovl "base"+0x08, %%ebp\n" \
"\tmovl "base"+0x10, %%ebx\n" \
"\tmovl "base"+0x14, %%edx\n" \
"\tmovl "base"+0x18, %%ecx\n" \
"\tmovl "base"+0x1c, %%eax\n" \
"\tmovl "base"+0x28, %%esp\n"
static struct regs before, during, after;
static void
check_regs(struct regs* a, const char *an, struct regs* b, const char *bn,
const char *testname)
{
int mismatch = 0;
cprintf("%-6s %-8s %-8s\n", "", an, bn);
#define CHECK(name, field) \
do { \
cprintf("%-6s %08x %08x ", #name, a->field, b->field); \
if (a->field == b->field) \
cprintf("OK\n"); \
else { \
cprintf("MISMATCH\n"); \
mismatch = 1; \
} \
} while (0)
CHECK(edi, regs.reg_edi);
CHECK(esi, regs.reg_esi);
CHECK(ebp, regs.reg_ebp);
CHECK(ebx, regs.reg_ebx);
CHECK(edx, regs.reg_edx);
CHECK(ecx, regs.reg_ecx);
CHECK(eax, regs.reg_eax);
CHECK(eip, eip);
CHECK(eflags, eflags);
CHECK(esp, esp);
#undef CHECK
cprintf("Registers %s ", testname);
if (!mismatch)
cprintf("OK\n");
else
cprintf("MISMATCH\n");
}
static void
pgfault(struct UTrapframe *utf)
{
int r;
if (utf->utf_fault_va != (uint32_t)UTEMP)
panic("pgfault expected at UTEMP, got 0x%08x (eip %08x)",
utf->utf_fault_va, utf->utf_eip);
// Check registers in UTrapframe
during.regs = utf->utf_regs;
during.eip = utf->utf_eip;
during.eflags = utf->utf_eflags & ~FL_RF;
during.esp = utf->utf_esp;
check_regs(&before, "before", &during, "during", "in UTrapframe");
// Map UTEMP so the write succeeds
if ((r = sys_page_alloc(0, UTEMP, PTE_U|PTE_P|PTE_W)) < 0)
panic("sys_page_alloc: %e", r);
}
void
umain(int argc, char **argv)
{
set_pgfault_handler(pgfault);
asm volatile(
// Light up eflags to catch more errors
"\tpushl %%eax\n"
"\tpushfl\n"
"\tpopl %%eax\n"
"\torl $0x8d5, %%eax\n"
"\tpushl %%eax\n"
"\tpopfl\n"
// Save before registers
// eflags
"\tmov %%eax, %0+0x24\n"
// eip
"\tleal 0f, %%eax\n"
"\tmovl %%eax, %0+0x20\n"
"\tpopl %%eax\n"
// others
SAVE_REGS("%0")
// Fault at UTEMP
"\t0: movl $42, 0x400000\n"
// Save after registers (except eip and eflags)
SAVE_REGS("%1")
// Restore registers (except eip and eflags). This
// way, the test will run even if EIP is the *only*
// thing restored correctly.
LOAD_REGS("%0")
// Save after eflags (now that stack is back); note
// that we were very careful not to modify eflags in
// since we saved it
"\tpushl %%eax\n"
"\tpushfl\n"
"\tpopl %%eax\n"
"\tmov %%eax, %1+0x24\n"
"\tpopl %%eax\n"
: : "m" (before), "m" (after) : "memory", "cc");
// Check UTEMP to roughly determine that EIP was restored
// correctly (of course, we probably wouldn't get this far if
// it weren't)
if (*(int*)UTEMP != 42)
cprintf("EIP after page-fault MISMATCH\n");
after.eip = before.eip;
check_regs(&before, "before", &after, "after", "after page-fault");
}

38
user/forktree.c Normal file
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@ -0,0 +1,38 @@
// Fork a binary tree of processes and display their structure.
#include <inc/lib.h>
#define DEPTH 3
void forktree(const char *cur);
void
forkchild(const char *cur, char branch)
{
char nxt[DEPTH+1];
if (strlen(cur) >= DEPTH)
return;
snprintf(nxt, DEPTH+1, "%s%c", cur, branch);
if (fork() == 0) {
forktree(nxt);
exit();
}
}
void
forktree(const char *cur)
{
cprintf("%04x: I am '%s'\n", sys_getenvid(), cur);
forkchild(cur, '0');
forkchild(cur, '1');
}
void
umain(int argc, char **argv)
{
forktree("");
}

20
user/idle.c Normal file
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@ -0,0 +1,20 @@
// idle loop
#include <inc/x86.h>
#include <inc/lib.h>
void
umain(int argc, char **argv)
{
binaryname = "idle";
// Loop forever, simply trying to yield to a different environment.
// Instead of busy-waiting like this,
// a better way would be to use the processor's HLT instruction
// to cause the processor to stop executing until the next interrupt -
// doing so allows the processor to conserve power more effectively.
while (1) {
sys_yield();
}
}

29
user/pingpong.c Normal file
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@ -0,0 +1,29 @@
// Ping-pong a counter between two processes.
// Only need to start one of these -- splits into two with fork.
#include <inc/lib.h>
void
umain(int argc, char **argv)
{
envid_t who;
if ((who = fork()) != 0) {
// get the ball rolling
cprintf("send 0 from %x to %x\n", sys_getenvid(), who);
ipc_send(who, 0, 0, 0);
}
while (1) {
uint32_t i = ipc_recv(&who, 0, 0);
cprintf("%x got %d from %x\n", sys_getenvid(), i, who);
if (i == 10)
return;
i++;
ipc_send(who, i, 0, 0);
if (i == 10)
return;
}
}

33
user/pingpongs.c Normal file
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@ -0,0 +1,33 @@
// Ping-pong a counter between two shared-memory processes.
// Only need to start one of these -- splits into two with sfork.
#include <inc/lib.h>
uint32_t val;
void
umain(int argc, char **argv)
{
envid_t who;
uint32_t i;
i = 0;
if ((who = sfork()) != 0) {
cprintf("i am %08x; thisenv is %p\n", sys_getenvid(), thisenv);
// get the ball rolling
cprintf("send 0 from %x to %x\n", sys_getenvid(), who);
ipc_send(who, 0, 0, 0);
}
while (1) {
ipc_recv(&who, 0, 0);
cprintf("%x got %d from %x (thisenv is %p %x)\n", sys_getenvid(), val, who, thisenv, thisenv->env_id);
if (val == 10)
return;
++val;
ipc_send(who, 0, 0, 0);
if (val == 10)
return;
}
}

53
user/primes.c Normal file
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// Concurrent version of prime sieve of Eratosthenes.
// Invented by Doug McIlroy, inventor of Unix pipes.
// See http://swtch.com/~rsc/thread/.
// The picture halfway down the page and the text surrounding it
// explain what's going on here.
//
// Since NENV is 1024, we can print 1022 primes before running out.
// The remaining two environments are the integer generator at the bottom
// of main and user/idle.
#include <inc/lib.h>
unsigned
primeproc(void)
{
int i, id, p;
envid_t envid;
// fetch a prime from our left neighbor
top:
p = ipc_recv(&envid, 0, 0);
cprintf("CPU %d: %d ", thisenv->env_cpunum, p);
// fork a right neighbor to continue the chain
if ((id = fork()) < 0)
panic("fork: %e", id);
if (id == 0)
goto top;
// filter out multiples of our prime
while (1) {
i = ipc_recv(&envid, 0, 0);
if (i % p)
ipc_send(id, i, 0, 0);
}
}
void
umain(int argc, char **argv)
{
int i, id;
// fork the first prime process in the chain
if ((id = fork()) < 0)
panic("fork: %e", id);
if (id == 0)
primeproc();
// feed all the integers through
for (i = 2; ; i++)
ipc_send(id, i, 0, 0);
}

31
user/spin.c Normal file
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// Test preemption by forking off a child process that just spins forever.
// Let it run for a couple time slices, then kill it.
#include <inc/lib.h>
void
umain(int argc, char **argv)
{
envid_t env;
cprintf("I am the parent. Forking the child...\n");
if ((env = fork()) == 0) {
cprintf("I am the child. Spinning...\n");
while (1)
/* do nothing */;
}
cprintf("I am the parent. Running the child...\n");
sys_yield();
sys_yield();
sys_yield();
sys_yield();
sys_yield();
sys_yield();
sys_yield();
sys_yield();
cprintf("I am the parent. Killing the child...\n");
sys_env_destroy(env);
}

39
user/stresssched.c Normal file
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#include <inc/lib.h>
volatile int counter;
void
umain(int argc, char **argv)
{
int i, j;
int seen;
envid_t parent = sys_getenvid();
// Fork several environments
for (i = 0; i < 20; i++)
if (fork() == 0)
break;
if (i == 20) {
sys_yield();
return;
}
// Wait for the parent to finish forking
while (envs[ENVX(parent)].env_status != ENV_FREE)
asm volatile("pause");
// Check that one environment doesn't run on two CPUs at once
for (i = 0; i < 10; i++) {
sys_yield();
for (j = 0; j < 10000; j++)
counter++;
}
if (counter != 10*10000)
panic("ran on two CPUs at once (counter is %d)", counter);
// Check that we see environments running on different CPUs
cprintf("[%08x] stresssched on CPU %d\n", thisenv->env_id, thisenv->env_cpunum);
}

17
user/yield.c Normal file
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// yield the processor to other environments
#include <inc/lib.h>
void
umain(int argc, char **argv)
{
int i;
cprintf("Hello, I am environment %08x.\n", thisenv->env_id);
for (i = 0; i < 5; i++) {
sys_yield();
cprintf("Back in environment %08x, iteration %d.\n",
thisenv->env_id, i);
}
cprintf("All done in environment %08x.\n", thisenv->env_id);
}