xv6-cs450/sysfile.c

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7.3 KiB
C
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#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"
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#include "file.h"
#include "fcntl.h"
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// Fetch the nth word-sized system call argument as a file descriptor
// and return both the descriptor and the corresponding struct file.
static int
argfd(int argno, int *pfd, struct file **pf)
{
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int fd;
struct file *f;
if(argint(argno, &fd) < 0)
return -1;
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if(fd < 0 || fd >= NOFILE || (f=cp->ofile[fd]) == 0)
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return -1;
if(pfd)
*pfd = fd;
if(pf)
*pf = f;
return 0;
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}
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// Allocate a file descriptor for the given file.
// Takes over file reference from caller on success.
static int
fdalloc(struct file *f)
{
int fd;
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for(fd = 0; fd < NOFILE; fd++){
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if(cp->ofile[fd] == 0){
cp->ofile[fd] = f;
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return fd;
}
}
return -1;
}
int
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sys_pipe(void)
{
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int *fd;
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struct file *rf, *wf;
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int fd0, fd1;
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if(argptr(0, (void*)&fd, 2*sizeof fd[0]) < 0)
return -1;
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if(pipe_alloc(&rf, &wf) < 0)
return -1;
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fd0 = -1;
if((fd0 = fdalloc(rf)) < 0 || (fd1 = fdalloc(wf)) < 0){
if(fd0 >= 0)
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cp->ofile[fd0] = 0;
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fileclose(rf);
fileclose(wf);
return -1;
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}
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fd[0] = fd0;
fd[1] = fd1;
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return 0;
}
int
sys_write(void)
{
struct file *f;
int n;
char *cp;
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if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &cp, n) < 0)
return -1;
return filewrite(f, cp, n);
}
int
sys_read(void)
{
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struct file *f;
int n;
char *cp;
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if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &cp, n) < 0)
return -1;
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return fileread(f, cp, n);
}
int
sys_close(void)
{
int fd;
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struct file *f;
if(argfd(0, &fd, &f) < 0)
return -1;
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cp->ofile[fd] = 0;
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fileclose(f);
return 0;
}
int
sys_open(void)
{
struct inode *ip, *dp;
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char *path;
int omode;
int fd;
struct file *f;
char *last;
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if(argstr(0, &path) < 0 || argint(1, &omode) < 0)
return -1;
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if(omode & O_CREATE){
dp = namei(path, 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 {
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ip = namei(path, NAMEI_LOOKUP, 0, 0, 0);
if(ip == 0)
return -1;
}
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if(ip->type == T_DIR && ((omode & O_RDWR) || (omode & O_WRONLY))){
iput(ip);
return -1;
}
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if((f = filealloc()) == 0){
iput(ip);
return -1;
}
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if((fd = fdalloc(f)) < 0){
iput(ip);
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fileclose(f);
return -1;
}
iunlock(ip);
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f->type = FD_FILE;
if(omode & O_RDWR) {
f->readable = 1;
f->writable = 1;
} else if(omode & O_WRONLY) {
f->readable = 0;
f->writable = 1;
} else {
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f->readable = 1;
f->writable = 0;
}
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f->ip = ip;
f->off = 0;
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return fd;
}
int
sys_mknod(void)
{
struct inode *nip;
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char *path;
int len;
int type, major, minor;
if((len=argstr(0, &path)) < 0 || argint(1, &type) < 0 ||
argint(2, &major) < 0 || argint(3, &minor) < 0)
return -1;
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if(len >= DIRSIZ)
return -1;
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if((nip = mknod(path, type, major, minor)) == 0)
return -1;
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iput(nip);
return 0;
}
int
sys_mkdir(void)
{
struct inode *nip;
struct inode *dp;
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char *path;
struct dirent de;
char *last;
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if(argstr(0, &path) < 0)
return -1;
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dp = namei(path, 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;
}
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dp->nlink++;
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 inode *ip;
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char *path;
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if(argstr(0, &path) < 0)
return -1;
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if((ip = namei(path, NAMEI_LOOKUP, 0, 0, 0)) == 0)
return -1;
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if(ip == cp->cwd) {
iput(ip);
return 0;
}
if(ip->type != T_DIR) {
iput(ip);
return -1;
}
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idecref(cp->cwd);
cp->cwd = ip;
iunlock(cp->cwd);
return 0;
}
int
sys_unlink(void)
{
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char *path;
if(argstr(0, &path) < 0)
return -1;
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return unlink(path);
}
int
sys_fstat(void)
{
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struct file *f;
struct stat *st;
if(argfd(0, 0, &f) < 0 || argptr(1, (void*)&st, sizeof *st) < 0)
return -1;
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return filestat(f, st);
}
int
sys_dup(void)
{
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struct file *f;
int fd;
if(argfd(0, 0, &f) < 0)
return -1;
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if((fd=fdalloc(f)) < 0)
return -1;
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fileincref(f);
return fd;
}
int
sys_link(void)
{
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char *old, *new;
if(argstr(0, &old) < 0 || argstr(1, &new) < 0)
return -1;
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return link(old, new);
}
int
sys_exec(void)
{
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uint sz=0, ap, sp, p1, p2;
int i, nargs, argbytes, len;
struct inode *ip;
struct elfhdr elf;
struct proghdr ph;
char *mem = 0;
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char *path, *s, *last;
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uint argv;
if(argstr(0, &path) < 0 || argint(1, (int*)&argv) < 0)
return -1;
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ip = namei(path, 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);
nargs = 0;
argbytes = 0;
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for(i = 0;; i++){
if(fetchint(cp, argv + 4*i, (int*)&ap) < 0)
goto bad;
if(ap == 0)
break;
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len = fetchstr(cp, ap, &s);
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++){
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fetchint(cp, argv + 4*i, (int*)&ap);
len = fetchstr(cp, ap, &s);
memmove(mem + p2, s, len + 1);
*(uint*)(mem + p1) = p2;
p1 += 4;
p2 += len + 1;
}
*(uint*)(mem + p1) = 0;
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// Save name for debugging.
for(last=s=path; *s; s++)
if(*s == '/')
last = s+1;
safestrcpy(cp->name, last, sizeof cp->name);
// 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);
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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;
}