xv6/syscall.c
rtm 8b4e2a08fe swtch saves callee-saved registers
swtch idles on per-CPU stack, not on calling process's stack
fix pipe bugs
usertest.c tests pipes, fork, exit, close
2006-07-01 21:26:01 +00:00

266 lines
4.5 KiB
C

#include "types.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
#include "traps.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 frame pointer, a program counter, and then
* the first argument.
*
* Return value? Error indication? Errno?
*/
/*
* fetch 32 bits from a user-supplied pointer.
* returns 1 if addr was OK, 0 if illegal.
*/
int
fetchint(struct proc *p, unsigned addr, int *ip)
{
*ip = 0;
if(addr > p->sz - 4)
return 0;
memcpy(ip, p->mem + addr, 4);
return 1;
}
int
fetcharg(int argno, int *ip)
{
unsigned esp;
esp = (unsigned) curproc[cpu()]->tf->tf_esp;
return fetchint(curproc[cpu()], esp + 8 + 4*argno, ip);
}
int
putint(struct proc *p, unsigned addr, int ip)
{
if(addr > p->sz - 4)
return 0;
memcpy(p->mem + addr, &ip, 4);
return 1;
}
int
sys_pipe()
{
struct fd *rfd = 0, *wfd = 0;
int f1 = -1, f2 = -1;
struct proc *p = curproc[cpu()];
unsigned fdp;
if(pipe_alloc(&rfd, &wfd) < 0)
goto oops;
if((f1 = fd_ualloc()) < 0)
goto oops;
p->fds[f1] = rfd;
if((f2 = fd_ualloc()) < 0)
goto oops;
p->fds[f2] = wfd;
if(fetcharg(0, &fdp) < 0)
goto oops;
if(putint(p, fdp, f1) < 0)
goto oops;
if(putint(p, fdp+4, f2) < 0)
goto oops;
return 0;
oops:
cprintf("sys_pipe failed\n");
if(rfd)
fd_close(rfd);
if(wfd)
fd_close(wfd);
if(f1 >= 0)
p->fds[f1] = 0;
if(f2 >= 0)
p->fds[f2] = 0;
return -1;
}
int
sys_write()
{
int fd, n, ret;
unsigned addr;
struct proc *p = curproc[cpu()];
if(fetcharg(0, &fd) < 0 || fetcharg(1, &addr) < 0 || fetcharg(2, &n) < 0)
return -1;
if(fd < 0 || fd >= NOFILE)
return -1;
if(p->fds[fd] == 0)
return -1;
if(addr + n > p->sz)
return -1;
ret = fd_write(p->fds[fd], p->mem + addr, n);
return ret;
}
int
sys_read()
{
int fd, n, ret;
unsigned addr;
struct proc *p = curproc[cpu()];
if(fetcharg(0, &fd) < 0 || fetcharg(1, &addr) < 0 || fetcharg(2, &n) < 0)
return -1;
if(fd < 0 || fd >= NOFILE)
return -1;
if(p->fds[fd] == 0)
return -1;
if(addr + n > p->sz)
return -1;
ret = fd_read(p->fds[fd], p->mem + addr, n);
return ret;
}
int
sys_close()
{
int fd;
struct proc *p = curproc[cpu()];
if(fetcharg(0, &fd) < 0)
return -1;
if(fd < 0 || fd >= NOFILE)
return -1;
if(p->fds[fd] == 0)
return -1;
fd_close(p->fds[fd]);
p->fds[fd] = 0;
return 0;
}
int
sys_fork()
{
struct proc *np;
np = newproc();
return np->pid;
}
int
sys_exit()
{
struct proc *p;
struct proc *cp = curproc[cpu()];
int fd;
for(fd = 0; fd < NOFILE; fd++){
if(cp->fds[fd]){
fd_close(cp->fds[fd]);
cp->fds[fd] = 0;
}
}
cp->state = ZOMBIE;
// wake up parent
for(p = proc; p < &proc[NPROC]; p++)
if(p->pid == cp->ppid)
wakeup(p);
// abandon children
for(p = proc; p < &proc[NPROC]; p++)
if(p->ppid == cp->pid)
p->pid = 1;
swtch();
return 0;
}
int
sys_wait()
{
struct proc *p;
struct proc *cp = curproc[cpu()];
int any, pid;
cprintf("waid pid %d ppid %d\n", cp->pid, cp->ppid);
while(1){
any = 0;
for(p = proc; p < &proc[NPROC]; p++){
if(p->state == ZOMBIE && p->ppid == cp->pid){
kfree(p->mem, p->sz);
kfree(p->kstack, KSTACKSIZE);
pid = p->pid;
p->state = UNUSED;
cprintf("%x collected %x\n", cp, p);
return pid;
}
if(p->state != UNUSED && p->ppid == cp->pid)
any = 1;
}
if(any == 0){
cprintf("%x nothing to wait for\n", cp);
return -1;
}
sleep(cp);
}
}
int
sys_cons_putc()
{
int c;
fetcharg(0, &c);
cons_putc(c & 0xff);
return 0;
}
void
syscall()
{
struct proc *cp = curproc[cpu()];
int num = cp->tf->tf_regs.reg_eax;
int ret = -1;
//cprintf("%x sys %d\n", cp, num);
switch(num){
case SYS_fork:
ret = sys_fork();
break;
case SYS_exit:
ret = sys_exit();
break;
case SYS_wait:
ret = sys_wait();
break;
case SYS_cons_putc:
ret = sys_cons_putc();
break;
case SYS_pipe:
ret = sys_pipe();
break;
case SYS_write:
ret = sys_write();
break;
case SYS_read:
ret = sys_read();
break;
case SYS_close:
ret = sys_close();
break;
default:
cprintf("unknown sys call %d\n", num);
// XXX fault
break;
}
cp->tf->tf_regs.reg_eax = ret;
}