On Tue, Jul 11, 2023 at 04:01:03PM +0200, Christian Brauner wrote: > On Tue, Jul 11, 2023 at 02:51:01PM +0200, Alexey Gladkov wrote: > > On Tue, Jul 11, 2023 at 01:52:01PM +0200, Christian Brauner wrote: > > > On Tue, Jul 11, 2023 at 01:42:19PM +0200, Arnd Bergmann wrote: > > > > On Tue, Jul 11, 2023, at 13:25, Alexey Gladkov wrote: > > > > > From: Palmer Dabbelt <palmer@xxxxxxxxxx> > > > > > > > > > > On the userspace side fchmodat(3) is implemented as a wrapper > > > > > function which implements the POSIX-specified interface. This > > > > > interface differs from the underlying kernel system call, which does not > > > > > have a flags argument. Most implementations require procfs [1][2]. > > > > > > > > > > There doesn't appear to be a good userspace workaround for this issue > > > > > but the implementation in the kernel is pretty straight-forward. > > > > > > > > > > The new fchmodat4() syscall allows to pass the AT_SYMLINK_NOFOLLOW flag, > > > > > unlike existing fchmodat. > > > > > > > > > > [1] > > > > > https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/fchmodat.c;h=17eca54051ee28ba1ec3f9aed170a62630959143;hb=a492b1e5ef7ab50c6fdd4e4e9879ea5569ab0a6c#l35 > > > > > [2] > > > > > https://git.musl-libc.org/cgit/musl/tree/src/stat/fchmodat.c?id=718f363bc2067b6487900eddc9180c84e7739f80#n28 > > > > > > > > > > Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxx> > > > > > Signed-off-by: Alexey Gladkov <legion@xxxxxxxxxx> > > > > > > > > I don't know the history of why we ended up with the different > > > > interface, or whether this was done intentionally in the kernel > > > > or if we want this syscall. > > > > > > > > Assuming this is in fact needed, I double-checked that the > > > > implementation looks correct to me and is portable to all the > > > > architectures, without the need for a compat wrapper. > > > > > > > > Acked-by: Arnd Bergmann <arnd@xxxxxxxx> > > > > > > The system call itself is useful afaict. But please, > > > > > > s/fchmodat4/fchmodat2/ > > > > Sure. I will. > > Thanks. Can you also wire this up for every architecture, please? > I don't see that this has been done in this series. Sure. I have already added in all architectures as far as I can tell: $ diff -s <(find arch/ -name '*.tbl' |sort -u) <(git grep -lw fchmodat2 arch/ |sort -u) Files /dev/fd/63 and /dev/fd/62 are identical -- Rgrds, legion
