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authorRich Felker <dalias@aerifal.cx>2022-04-28 02:02:38 -0400
committerRich Felker <dalias@aerifal.cx>2022-05-01 23:25:21 -0400
commit7edbcbeb76cb46381c34e2c0491dcc459cd5fa46 (patch)
parent9a9374955517bf731f11fd2c4a071b3cc1120526 (diff)
drop direct use of stat syscalls in fchmodat
instead, use the fstatat/stat functions, so that the logic for which
syscalls are present and usable is all in fstatat.

this results in a slight increase in cost for old kernels on 32-bit
archs: now statx will be attempted first rather than just using the
legacy time32 syscalls, despite us not caring about timestamps.
however, it's not even clear that the legacy syscalls *should* succeed
if the timestamps are out of range; arguably they should fail with
EOVERFLOW. as such, paying a small cost here on old kernels seems

with this change, fchmodat itself is no longer blocking ports to new
archs that lack the legacy syscalls.
1 files changed, 7 insertions, 8 deletions
diff --git a/src/stat/fchmodat.c b/src/stat/fchmodat.c
index 4ee00b0a..bc581050 100644
--- a/src/stat/fchmodat.c
+++ b/src/stat/fchmodat.c
@@ -2,7 +2,6 @@
 #include <fcntl.h>
 #include <errno.h>
 #include "syscall.h"
-#include "kstat.h"
 int fchmodat(int fd, const char *path, mode_t mode, int flag)
@@ -11,12 +10,12 @@ int fchmodat(int fd, const char *path, mode_t mode, int flag)
 	if (flag != AT_SYMLINK_NOFOLLOW)
 		return __syscall_ret(-EINVAL);
-	struct kstat st;
+	struct stat st;
 	int ret, fd2;
 	char proc[15+3*sizeof(int)];
-	if ((ret = __syscall(SYS_fstatat, fd, path, &st, flag)))
-		return __syscall_ret(ret);
+	if (fstatat(fd, path, &st, flag))
+		return -1;
 	if (S_ISLNK(st.st_mode))
 		return __syscall_ret(-EOPNOTSUPP);
@@ -27,12 +26,12 @@ int fchmodat(int fd, const char *path, mode_t mode, int flag)
 	__procfdname(proc, fd2);
-	ret = __syscall(SYS_fstatat, AT_FDCWD, proc, &st, 0);
+	ret = stat(proc, &st);
 	if (!ret) {
-		if (S_ISLNK(st.st_mode)) ret = -EOPNOTSUPP;
-		else ret = __syscall(SYS_fchmodat, AT_FDCWD, proc, mode);
+		if (S_ISLNK(st.st_mode)) ret = __syscall_ret(-EOPNOTSUPP);
+		else ret = syscall(SYS_fchmodat, AT_FDCWD, proc, mode);
 	__syscall(SYS_close, fd2);
-	return __syscall_ret(ret);
+	return ret;