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simplify faccessat AT_EACCESS path and eliminate resource dependence 

now that we're waiting for the exit status of the child process, the
result can be conveyed in the exit status rather than via a pipe.
since the error value might not fit in 7 bits, a table is used to
translate possible meaningful error values to small integers.
This commit is contained in:
Rich Felker 2013-11-01 20:34:05 -04:00
parent 984af5c99e
commit f9fb20b42d
1 changed files with 21 additions and 14 deletions
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33
src/unistd/faccessat.c
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@ -1,5 +1,6 @@
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/wait.h>
#include "syscall.h"
#include "pthread_impl.h"
@ -8,19 +9,26 @@ struct ctx {
int fd;
const char *filename;
int amode;
int p;
};
static const int errors[] = {
0, -EACCES, -ELOOP, -ENAMETOOLONG, -ENOENT, -ENOTDIR,
-EROFS, -EBADF, -EINVAL, -ETXTBSY,
-EFAULT, -EIO, -ENOMEM,
-EBUSY
};
static int checker(void *p)
{
struct ctx *c = p;
int ret;
int i;
if (__syscall(SYS_setregid, __syscall(SYS_getegid), -1)
|| __syscall(SYS_setreuid, __syscall(SYS_geteuid), -1))
__syscall(SYS_exit, 1);
ret = __syscall(SYS_faccessat, c->fd, c->filename, c->amode, 0);
__syscall(SYS_write, c->p, &ret, sizeof ret);
return 0;
for (i=0; i < sizeof errors/sizeof *errors - 1 && ret!=errors[i]; i++);
return i;
}
int faccessat(int fd, const char *filename, int amode, int flag)
@ -34,21 +42,20 @@ int faccessat(int fd, const char *filename, int amode, int flag)
char stack[1024];
sigset_t set;
pid_t pid;
int status;
int ret, p[2];
if (pipe2(p, O_CLOEXEC)) return __syscall_ret(-EBUSY);
struct ctx c = { .fd = fd, .filename = filename, .amode = amode, .p = p[1] };
int ret = -EBUSY;
struct ctx c = { .fd = fd, .filename = filename, .amode = amode };
__block_all_sigs(&set);
pid = __clone(checker, stack+sizeof stack, 0, &c);
__syscall(SYS_close, p[1]);
if (pid<0 || __syscall(SYS_read, p[0], &ret, sizeof ret) != sizeof(ret))
ret = -EBUSY;
__syscall(SYS_close, p[0]);
if (pid > 0) {
int status;
do {
__syscall(SYS_wait4, pid, &status, __WCLONE, 0);
} while (!WIFEXITED(status) && !WIFSIGNALED(status));
if (WIFEXITED(status))
ret = errors[WEXITSTATUS(status)];
}
__restore_sigs(&set);