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xv6-65oo2/syscall.c
rtm 2aa4c3bc29 complain if no disk 1 
lots of cleanup
2006-08-30 18:55:06 +00:00

678 lines
11 KiB
C
Raw Blame History

#include "types.h"
#include "stat.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
#include "traps.h"
#include "syscall.h"
#include "spinlock.h"
#include "buf.h"
#include "fs.h"
#include "fsvar.h"
#include "elf.h"
#include "fd.h"
#include "fcntl.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 32 bits from a user-supplied pointer.
* returns 0 if addr was OK, -1 if illegal.
*/
int
fetchint(struct proc *p, uint addr, int *ip)
{
*ip = 0;
if(addr > p->sz - 4)
return -1;
*ip = *(int*)(p->mem + addr);
return 0;
}
// Fetch byte from a user-supplied pointer.
// Returns 0 on success, -1 if pointer is illegal.
int
fetchbyte(struct proc *p, uint addr, char* c)
{
if(addr >= p->sz)
return -1;
*c = *(p->mem + addr);
return 0;
}
int
fetcharg(int argno, void *ip)
{
uint esp;
esp = (uint) curproc[cpu()]->tf->esp;
return fetchint(curproc[cpu()], esp + 4 + 4*argno, ip);
}
// check that an entire string is valid in user space.
// returns the length, not including null, or -1.
int
checkstring(uint s)
{
char c;
int len = 0;
while(1){
if(fetchbyte(curproc[cpu()], s, &c) < 0)
return -1;
if(c == '\0')
return len;
len++;
s++;
}
}
int
putint(struct proc *p, uint addr, int x)
{
if(addr > p->sz - 4)
return -1;
memmove(p->mem + addr, &x, 4);
return 0;
}
int
sys_pipe(void)
{
struct fd *rfd = 0, *wfd = 0;
int f1 = -1, f2 = -1;
struct proc *p = curproc[cpu()];
uint 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:
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(void)
{
int fd, n, ret;
uint 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(void)
{
int fd, n, ret;
uint 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(void)
{
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(void)
{
struct proc *np;
if((np = copyproc(curproc[cpu()])) == 0)
return -1;
np->state = RUNNABLE;
return np->pid;
}
int
sys_exit(void)
{
proc_exit();
return 0; // not reached
}
int
sys_wait(void)
{
return proc_wait();
}
int
sys_kill(void)
{
int pid;
if(fetcharg(0, &pid) < 0)
return -1;
return proc_kill(pid);
}
int
sys_open(void)
{
struct proc *cp = curproc[cpu()];
struct inode *ip, *dp;
uint arg0, arg1;
int ufd;
struct fd *fd;
int l;
char *last;
if(fetcharg(0, &arg0) < 0 || fetcharg(1, &arg1) < 0)
return -1;
if((l = checkstring(arg0)) < 0)
return -1;
if(arg1 & O_CREATE){
dp = namei(cp->mem + arg0, NAMEI_CREATE, 0, &last, &ip);
if(dp){
ip = mknod1(dp, last, T_FILE, 0, 0);
iput(dp);
if(ip == 0)
return -1;
} else if(ip == 0){
return -1;
} else if(ip->type == T_DIR){
iput(ip);
return -1;
}
} else {
ip = namei(cp->mem + arg0, NAMEI_LOOKUP, 0, 0, 0);
if(ip == 0)
return -1;
}
if(ip->type == T_DIR && ((arg1 & O_RDWR) || (arg1 & O_WRONLY))){
iput(ip);
return -1;
}
if((fd = fd_alloc()) == 0){
iput(ip);
return -1;
}
if((ufd = fd_ualloc()) < 0){
iput(ip);
fd_close(fd);
return -1;
}
iunlock(ip);
fd->type = FD_FILE;
if (arg1 & O_RDWR) {
fd->readable = 1;
fd->writeable = 1;
} else if (arg1 & O_WRONLY) {
fd->readable = 0;
fd->writeable = 1;
} else {
fd->readable = 1;
fd->writeable = 0;
}
fd->ip = ip;
fd->off = 0;
cp->fds[ufd] = fd;
return ufd;
}
int
sys_mknod(void)
{
struct proc *cp = curproc[cpu()];
struct inode *nip;
uint arg0, arg1, arg2, arg3;
int l;
if(fetcharg(0, &arg0) < 0 || fetcharg(1, &arg1) < 0 ||
fetcharg(2, &arg2) < 0 || fetcharg(3, &arg3) < 0)
return -1;
if((l = checkstring(arg0)) < 0)
return -1;
if(l >= DIRSIZ)
return -1;
nip = mknod (cp->mem + arg0, (short) arg1, (short) arg2, (short) arg3);
if(nip)
iput(nip);
return (nip == 0) ? -1 : 0;
}
int
sys_mkdir(void)
{
struct proc *cp = curproc[cpu()];
struct inode *nip;
struct inode *dp;
uint arg0;
int l;
struct dirent de;
char *last;
if(fetcharg(0, &arg0) < 0)
return -1;
if((l = checkstring(arg0)) < 0)
return -1;
dp = namei(cp->mem + arg0, NAMEI_CREATE, 0, &last, 0);
if(dp == 0)
return -1;
nip = mknod1(dp, last, T_DIR, 0, 0);
if(nip == 0){
iput(dp);
return -1;
}
dp->nlink += 1;
iupdate(dp);
memset (de.name, '\0', DIRSIZ);
de.name[0] = '.';
de.inum = nip->inum;
writei (nip, (char *) &de, 0, sizeof(de));
de.inum = dp->inum;
de.name[1] = '.';
writei (nip, (char *) &de, sizeof(de), sizeof(de));
iput(dp);
iput(nip);
return 0;
}
int
sys_chdir(void)
{
struct proc *cp = curproc[cpu()];
struct inode *ip;
uint arg0;
int l;
if(fetcharg(0, &arg0) < 0)
return -1;
if((l = checkstring(arg0)) < 0)
return -1;
if ((ip = namei(cp->mem + arg0, NAMEI_LOOKUP, 0, 0, 0)) == 0)
return -1;
if (ip == cp->cwd) {
iput (ip);
return 0;
}
if (ip->type != T_DIR) {
iput(ip);
return -1;
}
idecref(cp->cwd);
cp->cwd = ip;
iunlock(cp->cwd);
return 0;
}
int
sys_unlink(void)
{
struct proc *cp = curproc[cpu()];
uint arg0;
int r;
if(fetcharg(0, &arg0) < 0)
return -1;
if(checkstring(arg0) < 0)
return -1;
r = unlink(cp->mem + arg0);
return r;
}
int
sys_fstat(void)
{
struct proc *cp = curproc[cpu()];
uint fd, addr;
int r;
if(fetcharg(0, &fd) < 0)
return -1;
if(fetcharg(1, &addr) < 0)
return -1;
if(fd < 0 || fd >= NOFILE)
return -1;
if(cp->fds[fd] == 0)
return -1;
if(addr + sizeof(struct stat) > cp->sz)
return -1;
r = fd_stat (cp->fds[fd], (struct stat *)(cp->mem + addr));
return r;
}
int
sys_dup(void)
{
struct proc *cp = curproc[cpu()];
uint fd, ufd1;
if(fetcharg(0, &fd) < 0)
return -1;
if(fd < 0 || fd >= NOFILE)
return -1;
if(cp->fds[fd] == 0)
return -1;
if ((ufd1 = fd_ualloc()) < 0)
return -1;
cp->fds[ufd1] = cp->fds[fd];
fd_incref(cp->fds[ufd1]);
return ufd1;
}
int
sys_link(void)
{
struct proc *cp = curproc[cpu()];
uint name1, name2;
int r;
if(fetcharg(0, &name1) < 0 || checkstring(name1) < 0)
return -1;
if(fetcharg(1, &name2) < 0 || checkstring(name2) < 0)
return -1;
r = link(cp->mem + name1, cp->mem + name2);
return r;
}
int
sys_getpid(void)
{
struct proc *cp = curproc[cpu()];
return cp->pid;
}
int
sys_sbrk(void)
{
uint addr;
int n;
struct proc *cp = curproc[cpu()];
if(fetcharg(0, &n) < 0)
return -1;
if((addr = growproc(n)) == 0xffffffff)
return -1;
setupsegs(cp);
return addr;
}
int
sys_exec(void)
{
struct proc *cp = curproc[cpu()];
uint arg0, arg1, sz=0, ap, sp, p1, p2;
int i, nargs, argbytes, len;
struct inode *ip;
struct elfhdr elf;
struct proghdr ph;
char *mem = 0;
if(fetcharg(0, &arg0) < 0)
return -1;
if(fetcharg(1, &arg1) < 0)
return -1;
if(checkstring(arg0) < 0)
return -1;
ip = namei(cp->mem + arg0, NAMEI_LOOKUP, 0, 0, 0);
if(ip == 0)
return -1;
if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
goto bad;
if(elf.magic != ELF_MAGIC)
goto bad;
sz = 0;
for(i = 0; i < elf.phnum; i++){
if(readi(ip, (char*)&ph, elf.phoff + i * sizeof(ph),
sizeof(ph)) != sizeof(ph))
goto bad;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.memsz < ph.filesz)
goto bad;
sz += ph.memsz;
}
sz += 4096 - (sz % 4096);
sz += 4096;
mem = kalloc(sz);
if(mem == 0)
goto bad;
memset(mem, 0, sz);
// arg1 is a pointer to an array of pointers to string.
nargs = 0;
argbytes = 0;
for(i = 0; ; i++){
if(fetchint(cp, arg1 + 4*i, &ap) < 0)
goto bad;
if(ap == 0)
break;
len = checkstring(ap);
if(len < 0)
goto bad;
nargs++;
argbytes += len + 1;
}
// argn\0
// ...
// arg0\0
// 0
// ptr to argn
// ...
// 12: ptr to arg0
// 8: argv (points to ptr to arg0)
// 4: argc
// 0: fake return pc
sp = sz - argbytes - (nargs+1)*4 - 4 - 4 - 4;
*(uint*)(mem + sp) = 0xffffffff;
*(uint*)(mem + sp + 4) = nargs;
*(uint*)(mem + sp + 8) = (uint)(sp + 12);
p1 = sp + 12;
p2 = sp + 12 + (nargs + 1) * 4;
for(i = 0; i < nargs; i++){
fetchint(cp, arg1 + 4*i, &ap);
len = checkstring(ap);
memmove(mem + p2, cp->mem + ap, len + 1);
*(uint*)(mem + p1) = p2;
p1 += 4;
p2 += len + 1;
}
*(uint*)(mem + p1) = 0;
// commit to the new image.
kfree(cp->mem, cp->sz);
cp->sz = sz;
cp->mem = mem;
mem = 0;
for(i = 0; i < elf.phnum; i++){
if(readi(ip, (char*)&ph, elf.phoff + i * sizeof(ph),
sizeof(ph)) != sizeof(ph))
goto bad2;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.va + ph.memsz > sz)
goto bad2;
if(readi(ip, cp->mem + ph.va, ph.offset, ph.filesz) != ph.filesz)
goto bad2;
memset(cp->mem + ph.va + ph.filesz, 0, ph.memsz - ph.filesz);
}
iput(ip);
cp->tf->eip = elf.entry;
cp->tf->esp = sp;
setupsegs(cp);
return 0;
bad:
if(mem)
kfree(mem, sz);
iput(ip);
return -1;
bad2:
iput(ip);
proc_exit();
return 0;
}
void
syscall(void)
{
struct proc *cp = curproc[cpu()];
int num = cp->tf->eax;
int ret = -1;
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_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;
case SYS_kill:
ret = sys_kill();
break;
case SYS_exec:
ret = sys_exec();
break;
case SYS_open:
ret = sys_open();
break;
case SYS_mknod:
ret = sys_mknod();
break;
case SYS_unlink:
ret = sys_unlink();
break;
case SYS_fstat:
ret = sys_fstat();
break;
case SYS_link:
ret = sys_link();
break;
case SYS_mkdir:
ret = sys_mkdir();
break;
case SYS_chdir:
ret = sys_chdir();
break;
case SYS_dup:
ret = sys_dup();
break;
case SYS_getpid:
ret = sys_getpid();
break;
case SYS_sbrk:
ret = sys_sbrk();
break;
default:
cprintf("unknown sys call %d\n", num);
// XXX fault
break;
}
cp->tf->eax = ret;
}
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