syscall.c

#include "types.h"
#include "defs.h"
#include "param.h"
#include "memlayout.h"
#include "mmu.h"
#include "proc.h"
#include "x86.h"
#include "syscall.h"

// User code makes a system call with INT T_SYSCALL.
// System call number in %eax.
// Arguments on the stack, from the user call to the C
// library system call function. The saved user %esp points
// to a saved program counter, and then the first argument.

// Fetch the int at addr from the current process.
int
fetchint(uint addr, int *ip)
{
	struct proc *curproc = myproc();

	if (addr >= curproc->sz || addr + 4 > curproc->sz) return -1;
	*ip = *(int *)(addr);
	return 0;
}

// Fetch the nul-terminated string at addr from the current process.
// Doesn't actually copy the string - just sets *pp to point at it.
// Returns length of string, not including nul.
int
fetchstr(uint addr, char **pp)
{
	char *       s, *ep;
	struct proc *curproc = myproc();

	if (addr >= curproc->sz) return -1;
	*pp = (char *)addr;
	ep  = (char *)curproc->sz;
	for (s = *pp; s < ep; s++) {
		if (*s == 0) return s - *pp;
	}
	return -1;
}

// Fetch the nth 32-bit system call argument.
int
argint(int n, int *ip)
{
	return fetchint((myproc()->tf->esp) + 4 + 4 * n, ip);
}

// Fetch the nth word-sized system call argument as a pointer
// to a block of memory of size bytes.  Check that the pointer
// lies within the process address space.
int
argptr(int n, char **pp, int size)
{
	int          i;
	struct proc *curproc = myproc();

	if (argint(n, &i) < 0) return -1;
	if (size < 0 || (uint)i >= curproc->sz || (uint)i + size > curproc->sz) return -1;
	*pp = (char *)i;
	return 0;
}

// Fetch the nth word-sized system call argument as a string pointer.
// Check that the pointer is valid and the string is nul-terminated.
// (There is no shared writable memory, so the string can't change
// between this check and being used by the kernel.)
int
argstr(int n, char **pp)
{
	int addr;
	if (argint(n, &addr) < 0) return -1;
	return fetchstr(addr, pp);
}

extern int sys_chdir(void);
extern int sys_close(void);
extern int sys_dup(void);
extern int sys_exec(void);
extern int sys_exit(void);
extern int sys_fork(void);
extern int sys_fstat(void);
extern int sys_getpid(void);
extern int sys_kill(void);
extern int sys_link(void);
extern int sys_mkdir(void);
extern int sys_mknod(void);
extern int sys_open(void);
extern int sys_pipe(void);
extern int sys_read(void);
extern int sys_sbrk(void);
extern int sys_sleep(void);
extern int sys_unlink(void);
extern int sys_wait(void);
extern int sys_write(void);
extern int sys_uptime(void);
extern int sys_haw(void);

static int (*syscalls[])(void) = {
  [SYS_fork] sys_fork,   [SYS_exit] sys_exit,     [SYS_wait] sys_wait,     [SYS_pipe] sys_pipe,
  [SYS_read] sys_read,   [SYS_kill] sys_kill,     [SYS_exec] sys_exec,     [SYS_fstat] sys_fstat,
  [SYS_chdir] sys_chdir, [SYS_dup] sys_dup,       [SYS_getpid] sys_getpid, [SYS_sbrk] sys_sbrk,
  [SYS_sleep] sys_sleep, [SYS_uptime] sys_uptime, [SYS_open] sys_open,     [SYS_write] sys_write,
  [SYS_mknod] sys_mknod, [SYS_unlink] sys_unlink, [SYS_link] sys_link,     [SYS_mkdir] sys_mkdir,
  [SYS_close] sys_close, [SYS_haw] sys_haw,
};

void
syscall(void)
{
	int          num;
	struct proc *curproc = myproc();

	num = curproc->tf->eax;
	if (num > 0 && num < NELEM(syscalls) && syscalls[num]) {
		curproc->tf->eax = syscalls[num]();
	} else {
		cprintf("%d %s: unknown sys call %d\n", curproc->pid, curproc->name, num);
		curproc->tf->eax = -1;
	}
}