From: Christian Brauner <[email protected]>
To: Linus Torvalds <[email protected]>
Cc: Xi Ruoyao <[email protected]>,
[email protected],
"Andreas K. Huettel" <[email protected]>,
Arnd Bergmann <[email protected]>,
Huacai Chen <[email protected]>,
Mateusz Guzik <[email protected]>,
Alexander Viro <[email protected]>,
Jan Kara <[email protected]>,
[email protected], [email protected],
[email protected], Jens Axboe <[email protected]>,
[email protected]
Subject: Re: [PATCH 2/2] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...)
Date: Wed, 3 Jul 2024 20:39:39 +0200 [thread overview]
Message-ID: <20240703-zusagen-allzu-214f7651ecfd@brauner> (raw)
In-Reply-To: <20240703-begossen-extrem-6ed55a165113@brauner>
On Wed, Jul 03, 2024 at 08:14:15PM GMT, Christian Brauner wrote:
> On Wed, Jul 03, 2024 at 10:54:53AM GMT, Linus Torvalds wrote:
> > On Wed, 3 Jul 2024 at 10:40, Linus Torvalds
> > <[email protected]> wrote:
> > >
> > > Oh wow. Shows just *how* long ago that was - and how long ago I looked
> > > at 32-bit code. Because clearly, I was wrong.
> >
> > Ok, so clearly any *new* 32-bit architecture should use 'struct statx'
> > as 'struct stat', and at least avoid the conversion pain.
> >
> > Of course, if using <asm-generic/stat.h> like loongarch does, that is
> > very much not what happens. You get those old models with just 'long'.
> >
> > So any architecture that didn't do that 'stat == statx' and has
> > binaries with old stat models should just continue to have them.
> >
> > It's not like we can get rid of the kernel side code for that all _anyway_.
>
> Fwiw, the original motivation for that whole "let's do NULL with
> AT_EMPTY_PATH" (somewhat independent from the generic use of it) that
> somehow morphed into this discussion was that the Chrome Sandbox has
> rewrites fstatat() system calls to fstat() via SECCOMP_RET_TRAP:
>
> if (args.nr == __NR_fstatat_default) {
> if (*reinterpret_cast<const char*>(args.args[1]) == '\0' &&
> args.args[3] == static_cast<uint64_t>(AT_EMPTY_PATH)) {
> return syscall(__NR_fstat_default, static_cast<int>(args.args[0]),
> reinterpret_cast<default_stat_struct*>(args.args[2]));
> }
>
> while also disabling statx() completely because they can't (easily)
> rewrite it and don't want to allow it unless we have NULL for
> AT_EMPTY_PATH (which we'll have soon ofc).
>
> In any case in [1] I proposed they add back fstat()/fstatat64() which
> should get that problem solved because they can rewrite that thing.
>
> In any case, which one of these does a new architecture have to add for
> reasonable backward compatibility:
Going by riscv added in 2017 it would be:
newstat()
newlstat()
newfstat()
newfstatat()
statx()
>
> fstat()
> fstat64()
> fstatat64()
>
> lstat()
> lstat64()
>
> stat()
> stat64()
> statx()
>
> newstat()
> newlstat()
> newfstat()
> newfstatat()
>
> Because really that's a complete mess and we have all sorts of overflow
> issues and odd failures in the varioius variants. And the userspace
> ifdefery in libcs is just as bad if not very much worse.
>
> [1]: https://lore.kernel.org/lkml/20240226-altmodisch-gedeutet-91c5ba2f6071@brauner
next prev parent reply other threads:[~2024-07-03 18:39 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-25 11:00 [PATCH 0/2] statx NULL path support Mateusz Guzik
2024-06-25 11:00 ` [PATCH 1/2] vfs: add CLASS fd_raw Mateusz Guzik
2024-06-25 12:22 ` Xi Ruoyao
2024-06-25 13:13 ` Mateusz Guzik
2024-06-25 11:00 ` [PATCH 2/2] vfs: support statx(..., NULL, AT_EMPTY_PATH, ...) Mateusz Guzik
2024-06-25 13:24 ` Xi Ruoyao
2024-06-25 13:28 ` Xi Ruoyao
2024-06-25 13:28 ` Mateusz Guzik
2024-06-25 14:09 ` Huacai Chen
2024-06-25 14:58 ` Xi Ruoyao
2024-06-30 1:40 ` Huacai Chen
2024-06-30 2:39 ` Xi Ruoyao
2024-06-30 13:18 ` Huacai Chen
2024-07-01 11:59 ` Arnd Bergmann
2024-07-02 15:36 ` Huacai Chen
2024-07-02 17:06 ` Arnd Bergmann
2024-07-03 4:30 ` Huacai Chen
2024-07-03 8:45 ` Christian Brauner
2024-07-03 9:35 ` Huacai Chen
2024-07-03 10:07 ` Xi Ruoyao
2024-07-03 16:31 ` Linus Torvalds
2024-07-03 16:54 ` Xi Ruoyao
2024-07-03 17:09 ` Linus Torvalds
2024-07-03 17:30 ` Xi Ruoyao
2024-07-03 17:40 ` Linus Torvalds
2024-07-03 17:54 ` Linus Torvalds
2024-07-03 18:14 ` Christian Brauner
2024-07-03 18:39 ` Christian Brauner [this message]
2024-07-03 19:00 ` Linus Torvalds
2024-07-03 19:18 ` Linus Torvalds
2024-07-03 18:48 ` Xi Ruoyao
2024-07-03 19:05 ` Linus Torvalds
2024-07-03 19:33 ` Christian Brauner
2024-07-03 19:52 ` Linus Torvalds
2024-07-03 18:44 ` Arnd Bergmann
2024-07-03 19:55 ` Christian Brauner
2024-07-03 17:11 ` Xi Ruoyao
2024-07-04 2:38 ` Huacai Chen
2024-07-04 3:23 ` Xi Ruoyao
2024-07-04 4:14 ` Xi Ruoyao
2024-07-04 5:55 ` Florian Weimer
2024-07-04 6:02 ` Xi Ruoyao
2024-07-01 4:38 ` [PATCH 0/2] statx NULL path support Christoph Hellwig
2024-07-01 6:46 ` Xi Ruoyao
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