Re: [PATCH] LoongArch: Define __ARCH_WANT_NEW_STAT in unistd.h
From: maobibo
Date: Wed May 15 2024 - 05:30:48 EST
On 2024/5/11 下午8:17, Arnd Bergmann wrote:
On Sat, May 11, 2024, at 12:01, Huacai Chen wrote:
Chromium sandbox apparently wants to deny statx [1] so it could properly
inspect arguments after the sandboxed process later falls back to fstat.
Because there's currently not a "fd-only" version of statx, so that the
sandbox has no way to ensure the path argument is empty without being
able to peek into the sandboxed process's memory. For architectures able
to do newfstatat though, glibc falls back to newfstatat after getting
-ENOSYS for statx, then the respective SIGSYS handler [2] takes care of
inspecting the path argument, transforming allowed newfstatat's into
fstat instead which is allowed and has the same type of return value.
But, as LoongArch is the first architecture to not have fstat nor
newfstatat, the LoongArch glibc does not attempt falling back at all
when it gets -ENOSYS for statx -- and you see the problem there!
My main objection here is that this is inconsistent with 32-bit
architectures: we normally have newfstatat() on 64-bit
architectures but fstatat64() on 32-bit ones. While loongarch64
is the first 64-bit one that is missing newfstatat(), we have
riscv32 already without fstatat64().
Importantly, we can't just add fstatat64() on riscv32 because
there is no time64 version for it other than statx(), and I don't
want the architectures to diverge more than necessary.
yes, I agree. Normally there is newfstatat() on 64-bit architectures but
fstatat64() on 32-bit ones.
I do not understand why fstatat64() can be added for riscv32 still.
32bit timestamp seems works well for the present, it is valid until
(0x1UL << 32) / 365 / 24 / 3600 + 1970 == 2106 year. Year 2106 should
be enough for 32bit system.
Regards
Bibo Mao
I would not mind adding a variant of statx() that works for
both riscv32 and loongarch64 though, if it gets added to all
architectures.
Arnd