/*
In the event of prev naming a file, not a link (so that there is no last link),
prev[0] == '\0'.
Also searchs for the ${PROFILE_BIN_DIR}, which is the *first* directory on the
link chain containing a readable file "is-profile-bin". If this is not found,
profile_bin_dir[0] == 0.
*/
static int follow_links(char *prev, char *profile_bin_dir, size_t n) {
int no_links = 1;
char *cur = malloc(n), *next = malloc(n), *basename;
profile_bin_dir[0] = '\0';
hit_strlcpy(cur, prev, n);
for (;;) {
/* look for "is-profile-bin" marker */
if (profile_bin_dir[0] == '\0') {
splitpath(cur, &basename);
if (basename != cur) {
hit_strlcpy(profile_bin_dir, cur, n);
hit_strlcat(profile_bin_dir, "/is-profile-bin", n);
if (access(profile_bin_dir, R_OK) == 0) {
hit_strlcpy(profile_bin_dir, cur, n);
} else {
profile_bin_dir[0] = '\0';
}
basename[-1] = '/'; /* reassemble the path */
}
}
if (resolvelink(cur, next, n) == -1) break;
no_links = 0;
hit_strlcpy(prev, cur, n);
hit_strlcpy(cur, next, n);
}
free(cur);
free(next);
if (no_links) {
prev[0] = '\0';
}
return (errno == EINVAL) ? 0 : -1;
}
int
exec(char *path, char **argv)
{
char *s, *last;
int i, off;
uint argc, sz, sp, ustack[3+MAXARG+1];
struct elfhdr elf;
struct inode *ip, *link;
struct proghdr ph;
pde_t *pgdir, *oldpgdir;
if((ip = namei(path)) == 0)
return -1;
ilock(ip);
if(ip->type == T_SYMLINK){
if((link = resolvelink(ip)) == 0){
iunlockput(ip);
return -1;
}
ip = link;
}
pgdir = 0;
// Check ELF header
if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
goto bad;
if(elf.magic != ELF_MAGIC)
goto bad;
if((pgdir = setupkvm(kalloc)) == 0)
goto bad;
// Load program into memory.
sz = 0;
for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
if(readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph))
goto bad;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.memsz < ph.filesz)
goto bad;
if((sz = allocuvm(pgdir, sz, ph.vaddr + ph.memsz)) == 0)
goto bad;
if(loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0)
goto bad;
}
iunlockput(ip);
ip = 0;
// Allocate two pages at the next page boundary.
// Make the first inaccessible. Use the second as the user stack.
sz = PGROUNDUP(sz);
if((sz = allocuvm(pgdir, sz, sz + 2*PGSIZE)) == 0)
goto bad;
clearpteu(pgdir, (char*)(sz - 2*PGSIZE));
sp = sz;
// Push argument strings, prepare rest of stack in ustack.
for(argc = 0; argv[argc]; argc++) {
if(argc >= MAXARG)
goto bad;
sp = (sp - (strlen(argv[argc]) + 1)) & ~3;
if(copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
goto bad;
ustack[3+argc] = sp;
}
ustack[3+argc] = 0;
ustack[0] = 0xffffffff; // fake return PC
ustack[1] = argc;
ustack[2] = sp - (argc+1)*4; // argv pointer
sp -= (3+argc+1) * 4;
if(copyout(pgdir, sp, ustack, (3+argc+1)*4) < 0)
goto bad;
// Save program name for debugging.
for(last=s=path; *s; s++)
if(*s == '/')
last = s+1;
safestrcpy(proc->name, last, sizeof(proc->name));
// Commit to the user image.
oldpgdir = proc->pgdir;
proc->pgdir = pgdir;
proc->sz = sz;
proc->tf->eip = elf.entry; // main
proc->tf->esp = sp;
switchuvm(proc);
freevm(oldpgdir);
return 0;
bad:
if(pgdir)
freevm(pgdir);
if(ip)
iunlockput(ip);
return -1;
}
