From: "Arnd Bergmann" <arnd@arndb.de>
To: "Alexey Gladkov" <legion@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
"Alexander Viro" <viro@zeniv.linux.org.uk>
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Subject: Re: [PATCH v3 2/5] fs: Add fchmodat4()
Date: Tue, 11 Jul 2023 13:42:19 +0200 [thread overview]
Message-ID: <83363cbb-2431-4520-81a9-0d71f420cb36@app.fastmail.com> (raw)
In-Reply-To: <d11b93ad8e3b669afaff942e25c3fca65c6a983c.1689074739.git.legion@kernel.org>
On Tue, Jul 11, 2023, at 13:25, Alexey Gladkov wrote:
> From: Palmer Dabbelt <palmer@sifive.com>
>
> 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@sifive.com>
> Signed-off-by: Alexey Gladkov <legion@kernel.org>
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@arndb.de>
next prev parent reply other threads:[~2023-07-11 11:42 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 1:27 Add a new fchmodat4() syscall, v2 Palmer Dabbelt
2019-07-17 1:27 ` [PATCH v2 1/4] Non-functional cleanup of a "__user * filename" Palmer Dabbelt
2019-07-17 1:27 ` [PATCH v2 2/4] Add fchmodat4(), a new syscall Palmer Dabbelt
2019-07-17 1:48 ` Al Viro
2019-07-17 2:12 ` Palmer Dabbelt
2019-07-17 2:40 ` Rich Felker
2019-07-17 3:02 ` Al Viro
2019-07-17 1:27 ` [PATCH v2 3/4] arch: Register fchmodat4, usually as syscall 434 Palmer Dabbelt
2019-07-17 1:27 ` [PATCH v2 4/4] tools: Add fchmodat4 Palmer Dabbelt
2019-07-17 12:39 ` Arnaldo Carvalho de Melo
2020-06-09 13:52 ` Add a new fchmodat4() syscall, v2 Florian Weimer
2023-07-11 11:25 ` [PATCH v3 0/5] Add a new fchmodat4() syscall Alexey Gladkov
2023-07-11 11:25 ` [PATCH v3 1/5] Non-functional cleanup of a "__user * filename" Alexey Gladkov
2023-07-11 11:32 ` Arnd Bergmann
2023-07-11 11:25 ` [PATCH v3 2/5] fs: Add fchmodat4() Alexey Gladkov
2023-07-11 11:42 ` Arnd Bergmann [this message]
2023-07-11 11:52 ` Christian Brauner
2023-07-11 12:51 ` Alexey Gladkov
2023-07-11 14:01 ` Christian Brauner
2023-07-11 15:23 ` Alexey Gladkov
2023-07-11 12:28 ` Matthew Wilcox
2023-07-11 12:49 ` Alexey Gladkov
2023-07-11 11:25 ` [PATCH v3 3/5] arch: Register fchmodat4, usually as syscall 451 Alexey Gladkov
2023-07-11 11:31 ` Arnd Bergmann
2023-07-11 11:25 ` [PATCH v3 4/5] tools headers UAPI: Sync files changed by new fchmodat4 syscall Alexey Gladkov
2023-07-11 11:25 ` [PATCH v3 5/5] selftests: add fchmodat4(2) selftest Alexey Gladkov
2023-07-11 12:10 ` Florian Weimer
2023-07-11 13:38 ` Alexey Gladkov
2023-07-11 12:24 ` [PATCH v3 0/5] Add a new fchmodat4() syscall Florian Weimer
2023-07-11 15:14 ` Christian Brauner
2023-07-25 11:05 ` Alexey Gladkov
2023-07-25 12:05 ` Christian Brauner
2023-07-11 16:16 ` [PATCH v4 0/5] Add a new fchmodat2() syscall Alexey Gladkov
2023-07-11 16:16 ` [PATCH v4 1/5] Non-functional cleanup of a "__user * filename" Alexey Gladkov
2023-07-11 16:16 ` [PATCH v4 2/5] fs: Add fchmodat2() Alexey Gladkov
2023-07-11 17:05 ` Christian Brauner
2023-07-25 16:36 ` Aleksa Sarai
2023-07-26 13:45 ` Alexey Gladkov
2023-07-27 10:26 ` Christian Brauner
2023-07-27 17:12 ` Aleksa Sarai
2023-07-27 17:39 ` Aleksa Sarai
2023-07-28 8:43 ` David Laight
2023-07-28 18:42 ` dalias
2023-07-27 9:01 ` David Laight
2023-07-27 16:28 ` Andreas Schwab
2023-07-27 17:02 ` Christian Brauner
2023-07-27 17:13 ` dalias
2023-07-27 17:36 ` Christian Brauner
2023-07-27 16:31 ` dalias
2023-07-11 16:16 ` [PATCH v4 3/5] arch: Register fchmodat2, usually as syscall 452 Alexey Gladkov
2023-07-11 16:26 ` Arnd Bergmann
2023-07-25 7:16 ` Geert Uytterhoeven
2023-07-25 16:43 ` Aleksa Sarai
2023-07-27 10:37 ` Christian Brauner
2023-07-27 17:42 ` Aleksa Sarai
2023-07-11 16:16 ` [PATCH v4 4/5] tools headers UAPI: Sync files changed by new fchmodat2 syscall Alexey Gladkov
2023-07-11 17:19 ` Namhyung Kim
2023-07-11 17:23 ` Alexey Gladkov
2023-07-11 16:16 ` [PATCH v4 5/5] selftests: Add fchmodat2 selftest Alexey Gladkov
2023-07-11 17:36 ` (subset) [PATCH v4 0/5] Add a new fchmodat2() syscall Christian Brauner
2023-07-12 2:42 ` Rich Felker
2023-07-25 15:58 ` Add fchmodat2() - or add a more general syscall? David Howells
2023-07-25 16:10 ` Florian Weimer
2023-07-25 16:50 ` Aleksa Sarai
2023-07-25 18:39 ` David Howells
2023-07-25 18:44 ` Rich Felker
2023-07-26 13:30 ` Christian Brauner
2023-07-27 3:57 ` Eric Biggers
2023-07-27 10:27 ` Christian Brauner
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