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fs: add ksys_fchmod() and do_fchmodat() helpers and ksys_chmod() wrapper; remove in-kernel calls to syscall

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Using the fs-internal do_fchmodat() helper allows us to get rid of
fs-internal calls to the sys_fchmodat() syscall.

Introducing the ksys_fchmod() helper and the ksys_chmod() wrapper allows
us to avoid the in-kernel calls to the sys_fchmod() and sys_chmod()
syscalls. The ksys_ prefix denotes that these functions are meant as a
drop-in replacement for the syscalls. In particular, they use the same
calling convention as sys_fchmod() and sys_chmod().

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>
This commit is contained in:
Dominik Brodowski
2018-03-11 11:34:53 +01:00
parent 46ea89eb65
commit 03450e271a
4 changed files with 27 additions and 6 deletions
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17
fs/open.c
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@@ -551,7 +551,7 @@ out_unlock:
return error;
}
SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
int ksys_fchmod(unsigned int fd, umode_t mode)
{
struct fd f = fdget(fd);
int err = -EBADF;
@@ -564,7 +564,12 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
return err;
}
SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
{
return ksys_fchmod(fd, mode);
}
int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
{
struct path path;
int error;
@@ -582,9 +587,15 @@ retry:
return error;
}
SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
umode_t, mode)
{
return do_fchmodat(dfd, filename, mode);
}
SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
{
return sys_fchmodat(AT_FDCWD, filename, mode);
return do_fchmodat(AT_FDCWD, filename, mode);
}
static int chown_common(const struct path *path, uid_t user, gid_t group)