jos/lib/syscall.c

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2018-09-25 09:22:51 -07:00
// System call stubs.
#include <inc/syscall.h>
#include <inc/lib.h>
static inline int32_t
syscall(int num, int check, uint32_t a1, uint32_t a2, uint32_t a3, uint32_t a4, uint32_t a5)
{
int32_t ret;
// Generic system call: pass system call number in AX,
// up to five parameters in DX, CX, BX, DI, SI.
// Interrupt kernel with T_SYSCALL.
//
// The "volatile" tells the assembler not to optimize
// this instruction away just because we don't use the
// return value.
//
// The last clause tells the assembler that this can
// potentially change the condition codes and arbitrary
// memory locations.
asm volatile("int %1\n"
: "=a" (ret)
: "i" (T_SYSCALL),
"a" (num),
"d" (a1),
"c" (a2),
"b" (a3),
"D" (a4),
"S" (a5)
: "cc", "memory");
if(check && ret > 0)
panic("syscall %d returned %d (> 0)", num, ret);
return ret;
}
void
sys_cputs(const char *s, size_t len)
{
syscall(SYS_cputs, 0, (uint32_t)s, len, 0, 0, 0);
}
int
sys_cgetc(void)
{
return syscall(SYS_cgetc, 0, 0, 0, 0, 0, 0);
}
int
sys_env_destroy(envid_t envid)
{
return syscall(SYS_env_destroy, 1, envid, 0, 0, 0, 0);
}
envid_t
sys_getenvid(void)
{
return syscall(SYS_getenvid, 0, 0, 0, 0, 0, 0);
}