[PATCH v4 0/5] Add a new fchmodat2() syscall

Alexey Gladkov
2023-07-11T16:17:01Z

In glibc, the fchmodat(3) function has a flags argument according to the
POSIX specification [1], but kernel syscalls has no such argument.
Therefore, libc implementations do workarounds using /proc. However,
this requires procfs to be mounted and accessible.

This patch set adds fchmodat2(), a new syscall. The syscall allows to
pass the AT_SYMLINK_NOFOLLOW flag to disable LOOKUP_FOLLOW. In all other
respects, this syscall is no different from fchmodat().

[1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/chmod.html

Changes since v3 [cover.1689074739.git.legion@kernel.org]:

* Rebased to master because a new syscall has appeared in master.
* Increased __NR_compat_syscalls as pointed out by Arnd Bergmann.
* Syscall renamed fchmodat4 -> fchmodat2 as suggested by Christian Brauner.
* Returned do_fchmodat4() the original name. We don't need to version
internal functions.
* Fixed warnings found by checkpatch.pl.

Changes since v2 [20190717012719.5524-1-palmer@sifive.com]:

* Rebased to master.
* The lookup_flags passed to sys_fchmodat4 as suggested by Al Viro.
* Selftest added.

Changes since v1 [20190531191204.4044-1-palmer@sifive.com]:

* All architectures are now supported, which support squashed into a
single patch.
* The do_fchmodat() helper function has been removed, in favor of directly
calling do_fchmodat4().
* The patches are based on 5.2 instead of 5.1.

---

Alexey Gladkov (2):
fs: Add fchmodat2()
selftests: Add fchmodat2 selftest

Palmer Dabbelt (3):
Non-functional cleanup of a "__user * filename"
arch: Register fchmodat2, usually as syscall 452
tools headers UAPI: Sync files changed by new fchmodat2 syscall

arch/alpha/kernel/syscalls/syscall.tbl | 1 +
arch/arm/tools/syscall.tbl | 1 +
arch/arm64/include/asm/unistd.h | 2 +-
arch/arm64/include/asm/unistd32.h | 2 +
arch/ia64/kernel/syscalls/syscall.tbl | 1 +
arch/m68k/kernel/syscalls/syscall.tbl | 1 +
arch/microblaze/kernel/syscalls/syscall.tbl | 1 +
arch/mips/kernel/syscalls/syscall_n32.tbl | 1 +
arch/mips/kernel/syscalls/syscall_n64.tbl | 1 +
arch/mips/kernel/syscalls/syscall_o32.tbl | 1 +
arch/parisc/kernel/syscalls/syscall.tbl | 1 +
arch/powerpc/kernel/syscalls/syscall.tbl | 1 +
arch/s390/kernel/syscalls/syscall.tbl | 1 +
arch/sh/kernel/syscalls/syscall.tbl | 1 +
arch/sparc/kernel/syscalls/syscall.tbl | 1 +
arch/x86/entry/syscalls/syscall_32.tbl | 1 +
arch/x86/entry/syscalls/syscall_64.tbl | 1 +
arch/xtensa/kernel/syscalls/syscall.tbl | 1 +
fs/open.c | 18 +-
include/linux/syscalls.h | 4 +-
include/uapi/asm-generic/unistd.h | 5 +-
tools/include/uapi/asm-generic/unistd.h | 5 +-
.../arch/mips/entry/syscalls/syscall_n64.tbl | 2 +
.../arch/powerpc/entry/syscalls/syscall.tbl | 2 +
.../perf/arch/s390/entry/syscalls/syscall.tbl | 2 +
.../arch/x86/entry/syscalls/syscall_64.tbl | 2 +
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/fchmodat2/.gitignore | 2 +
tools/testing/selftests/fchmodat2/Makefile | 6 +
.../selftests/fchmodat2/fchmodat2_test.c | 162 ++++++++++++++++++
30 files changed, 223 insertions(+), 8 deletions(-)
create mode 100644 tools/testing/selftests/fchmodat2/.gitignore
create mode 100644 tools/testing/selftests/fchmodat2/Makefile
create mode 100644 tools/testing/selftests/fchmodat2/fchmodat2_test.c

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2.33.8