fs: add do_faccessat() helper and ksys_access() wrapper; remove in-kernel calls to syscall
Using the fs-internal do_faccessat() helper allows us to get rid of
fs-internal calls to the sys_faccessat() syscall.
Introducing the ksys_access() wrapper allows us to avoid the in-kernel
calls to the sys_access() syscall. The ksys_ prefix denotes that this
function is meant as a drop-in replacement for the syscall. In
particular, it uses the same calling convention as sys_access().
This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
diff --git a/fs/internal.h b/fs/internal.h
index 2474bf4..26f4f05 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -119,6 +119,7 @@
extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
const char *, const struct open_flags *);
+long do_faccessat(int dfd, const char __user *filename, int mode);
int do_fchmodat(int dfd, const char __user *filename, umode_t mode);
extern int open_check_o_direct(struct file *f);
diff --git a/fs/open.c b/fs/open.c
index 6037f2b..0fc8188 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -350,7 +350,7 @@
* We do this by temporarily clearing all FS-related capabilities and
* switching the fsuid/fsgid around to the real ones.
*/
-SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
+long do_faccessat(int dfd, const char __user *filename, int mode)
{
const struct cred *old_cred;
struct cred *override_cred;
@@ -426,9 +426,14 @@
return res;
}
+SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
+{
+ return do_faccessat(dfd, filename, mode);
+}
+
SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
{
- return sys_faccessat(AT_FDCWD, filename, mode);
+ return do_faccessat(AT_FDCWD, filename, mode);
}
int ksys_chdir(const char __user *filename)