jos/kern/monitor.c

// Simple command-line kernel monitor useful for
// controlling the kernel and exploring the system interactively.

#include <inc/stdio.h>
#include <inc/string.h>
#include <inc/memlayout.h>
#include <inc/assert.h>
#include <inc/x86.h>

#include <kern/env.h>
#include <kern/ansi.h>
#include <kern/console.h>
#include <kern/monitor.h>
#include <kern/kdebug.h>
#include <kern/trap.h>
#include <kern/pmap.h>
#include <inc/string.h>

#define CMDBUF_SIZE	80	// enough for one VGA text line


struct Command {
	const char *name;
	const char *desc;
	// return -1 to force monitor to exit
	int (*func)(int argc, char** argv, struct Trapframe* tf);
};

// LAB 1: add your command to here...
static struct Command commands[] = {
	{ "help", "Display this list of commands", mon_help },
	{ "kerninfo", "Display information about the kernel", mon_kerninfo },
	{ "backtrace", "Display current backtrace", mon_backtrace },
	{ "showmappings", "Display the physical mappings for range", mon_showmappings },
	{ "mperms", "Change the permissions of a memory range", mon_mperms },
	{ "resume", "Resume from a breakpoint", mon_resume },
	{ "step", "Step to next instruction", mon_step }
	
};

/***** Implementations of basic kernel monitor commands *****/

int
mon_help(int argc, char **argv, struct Trapframe *tf)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(commands); i++)
		cprintf("%s - %s\n", commands[i].name, commands[i].desc);
	return 0;
}

int
mon_kerninfo(int argc, char **argv, struct Trapframe *tf)
{
	extern char _start[], entry[], etext[], edata[], end[];

	cprintf("Special kernel symbols:\n");
	cprintf("  _start		  %08x (phys)\n", _start);
	cprintf("  entry  %08x (virt)  %08x (phys)\n", entry, entry - KERNBASE);
	cprintf("  etext  %08x (virt)  %08x (phys)\n", etext, etext - KERNBASE);
	cprintf("  edata  %08x (virt)  %08x (phys)\n", edata, edata - KERNBASE);
	cprintf("  end    %08x (virt)  %08x (phys)\n", end, end - KERNBASE);
	cprintf("Kernel executable memory footprint: %dKB\n",
		ROUNDUP(end - entry, 1024) / 1024);
	return 0;
}

int
mon_backtrace(int argc, char **argv, struct Trapframe *tf)
{
	// LAB 1: Your code here.
    // HINT 1: use read_ebp().
    // HINT 2: print the current ebp on the first line (not current_ebp[0])
	uint32_t* ebp;
	uint32_t eip;
	struct Eipdebuginfo info;

	ebp = (uint32_t*) read_ebp();
	cprintf("Stack backtrace:\n");
	while(ebp) {
		eip = ebp[1];
		cprintf("  ebp %08x  eip %08x  args %08x %08x %08x %08x %08x\n",
			ebp, eip, ebp[2], ebp[3], ebp[4], ebp[5], ebp[6]);
		ebp = (uint32_t*) ebp[0];
		
		debuginfo_eip(eip, &info);
		cprintf("	   %s:%d: %.*s+%d\n",
			info.eip_file, info.eip_line,
			info.eip_fn_namelen, info.eip_fn_name,
			eip - info.eip_fn_addr);
	};
	
	return 0;
}

#define EXPECT_ARGS(n, ac) if(ac - 1 != n) { \
	cprintf(ACOL_ERR("Expected %d arguments, " \
		"got %d\n"), n, ac - 1); \
	return 1; }

#define VA_TXT ACOL_CYAN "VA" ACOL_CLEAR
#define PA_TXT ACOL_GREEN "PA" ACOL_CLEAR

char*
decode_pte_perms(pte_t pte, char* buffer) {
	buffer[0] = (pte & PTE_W) ? 'w' : 'r';
	buffer[1] = (pte & PTE_U) ? 'u' : 'k';
	return buffer;
}

void
get_pagebounds(char* one, char* two, uintptr_t* pone, uintptr_t* ptwo) {
	long from = strtol(one, NULL, 0);
	long to = strtol(two, NULL, 0);
	*pone = ROUNDDOWN(from, PGSIZE);
	*ptwo = ROUNDUP(to, PGSIZE);
	if(*pone != from) cprintf(ACOL_WARN("Aligning start address %p down to %p\n"),
		from, *pone);
	if(*ptwo != to) cprintf(ACOL_WARN("Aligning end address %p up to %p\n"),
		to, *ptwo);
}

int
mon_showmappings(int argc, char** argv, struct Trapframe* tf) {
	EXPECT_ARGS(2, argc);
	uintptr_t va_start, va_end;
	char buffer[3] = {0};

	get_pagebounds(argv[1], argv[2], &va_start, &va_end);

	if(va_start == va_end) va_end += PGSIZE;
	while(va_start < va_end) {
		pte_t* pte = pgdir_walk(kern_pgdir, (const void*) va_start, 0);
		cprintf(VA_TXT " 0x%08p -> ", va_start);

		if(pte && (*pte & PTE_P)) {
			cprintf(PA_TXT " 0x%08p (%s)\n", PTE_ADDR(*pte),
				decode_pte_perms(*pte, buffer));
		} else {
			cprintf(PA_TXT " ------------\n");
		}

		va_start += PGSIZE;
	}

	return 0;
}

int mon_mperms(int argc, char** argv, struct Trapframe* tf) {
	EXPECT_ARGS(3, argc);
	pte_t perms = 0;
	enum {
		PERM_ADD,
		PERM_REMOVE,
		PERM_SET
	} pmode;

	const char* str = argv[1];
	if(str[0] == '+') { pmode = PERM_ADD; str++; }
	else if(str[0] == '-') { pmode = PERM_REMOVE; str++; }
	else pmode = PERM_SET;

	while(*str) {
		if(*str == 'w') perms |= PTE_W;
		else if(*str == 'u') perms |= PTE_U;
		else {
			cprintf(ACOL_ERR("Unknown permission character %c\n"), *str);
			return 1;
		}
		str++;
	}

	uintptr_t va_start, va_end;
	get_pagebounds(argv[2], argv[3], &va_start, &va_end);
	if(va_start == va_end) va_end += PGSIZE;
	while(va_start < va_end) {
		pte_t* pte = pgdir_walk(kern_pgdir, (void*) va_start, 0);
		if(!pte || !(*pte & PTE_P)) { va_start += PGSIZE; continue; }
		
		if(pmode == PERM_ADD) {
			*pte |= perms;
		} else if(pmode == PERM_REMOVE) {
			*pte &= ~perms;
		} else if(pmode == PERM_SET) {
			*pte = PTE_ADDR(*pte) | perms | PTE_P;
		}
		va_start += PGSIZE;
	}

	return 0;
}

// This is a nice thought and all...
// But we should modify the trap frame.
// I feel stupid.
static inline void
set_eflag(uint16_t flagno, int value) {
	uint32_t temp;
	uint32_t mask = ~(1 << flagno);
	uint32_t regv = value << flagno;
	asm volatile("pushfl\n\t"
			"pop %w0\n\t"
			"and %w1, %w0\n\t"
			"or %w2, %w0\n\t"
			"push %w0\n\t"
			"popfl\n\t"
			: "=r" (temp)
			: "r" (mask), "r" (regv));
}

#define EXPECT_BRKPT if(!(tf->tf_trapno == T_BRKPT || tf->tf_trapno == T_DEBUG)) { \
	cprintf(ACOL_ERR("I don't think I should resume from this.\n")); \
	return 0; }
#define EFLAGS_TF 0x8

int mon_resume(int argc, char** argv, struct Trapframe* tf) {
	EXPECT_BRKPT;
	tf->tf_eflags &= ~(1 << EFLAGS_TF);
	env_pop_tf(tf);
	return 0;
}

int mon_step(int argc, char** argv, struct Trapframe* tf) {
	EXPECT_BRKPT;
	tf->tf_eflags |= 1 << EFLAGS_TF;
	env_pop_tf(tf);
	return 0;
}

/***** Kernel monitor command interpreter *****/

#define WHITESPACE "\t\r\n "
#define MAXARGS 16

static int
runcmd(char *buf, struct Trapframe *tf)
{
	int argc;
	char *argv[MAXARGS];
	int i;

	// Parse the command buffer into whitespace-separated arguments
	argc = 0;
	argv[argc] = 0;
	while (1) {
		// gobble whitespace
		while (*buf && strchr(WHITESPACE, *buf))
			*buf++ = 0;
		if (*buf == 0)
			break;

		// save and scan past next arg
		if (argc == MAXARGS-1) {
			cprintf("Too many arguments (max %d)\n", MAXARGS);
			return 0;
		}
		argv[argc++] = buf;
		while (*buf && !strchr(WHITESPACE, *buf))
			buf++;
	}
	argv[argc] = 0;

	// Lookup and invoke the command
	if (argc == 0)
		return 0;
	for (i = 0; i < ARRAY_SIZE(commands); i++) {
		if (strcmp(argv[0], commands[i].name) == 0)
			return commands[i].func(argc, argv, tf);
	}
	cprintf("Unknown command '%s'\n", argv[0]);
	return 0;
}

void
monitor(struct Trapframe *tf)
{
	char *buf;

	cprintf("Welcome to the JOS kernel monitor!\n");
	cprintf("Type 'help' for a list of commands.\n");

	if (tf != NULL)
		print_trapframe(tf);

	while (1) {
		buf = readline("K> ");
		if (buf != NULL)
			if (runcmd(buf, tf) < 0)
				break;
	}
}