From: Luca Bonissi <qemu@bonslack.org>
To: Michael Tokarev <mjt@tls.msk.ru>, Helge Deller <deller@gmx.de>,
WANG Xuerui <xen0n@gentoo.org>,
qemu-devel@nongnu.org
Cc: "Laurent Vivier" <laurent@vivier.eu>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
"Andreas K . Hüttel" <dilfridge@gentoo.org>,
"Richard Henderson" <richard.henderson@linaro.org>
Subject: Re: [PATCH] linux-user: Implement faccessat2
Date: Tue, 18 Oct 2022 15:05:23 +0200 [thread overview]
Message-ID: <99174e4e-cf9e-b685-0911-d0f60a4e13be@bonslack.org> (raw)
In-Reply-To: <a69ae272-b0a3-cea3-b9a7-a678af274c2a@msgid.tls.msk.ru>
On 18/10/22 11:58, Michael Tokarev wrote:
> 10.10.2022 11:53, Helge Deller wrote:
>> On 10/9/22 08:08, WANG Xuerui wrote:
>>> User space has been preferring this syscall for a while, due to its
>>> closer match with C semantics, and newer platforms such as LoongArch
>>> apparently have libc implementations that don't fallback to faccessat
>>> so normal access checks are failing without the emulation in place.
>>
>> https://lore.kernel.org/qemu-devel/YzLdcnL6x646T61W@p100/
I think this one is the more complete and simplest solution.
Only change:
+#if defined(TARGET_NR_faccessat2) && defined(__NR_faccessat2)
with
+#if defined(TARGET_NR_faccessat2)
(not necessary to have host __NR_faccessat2)
and replace "faccessat2(...)" with "faccessat(...)", so it uses glibc
implementation, that uses __NR_faccessat2 if host has this syscall,
otherwise it falls back to faccessat with the addition of fstatat if
flags!=0 (obviously, the definition of syscall4(... faccessat2 ...)
should be removed).
> For loongarch64 users this has become essential, because this is a
> new enough arch so that userspace does not bother using older syscalls,
> in this case it uses faccessat2() for everything, and simplest programs
> fail under qemu due to no fallback whatsoever.
I agree that it has become essential. Development with qemu-user is much
faster than using qemu-system, with all the benefits to use chroot on a
shared file system.
I tested (and currently testing) the above patch with Slackware-current
build scripts on x86_64 host: all works fine!
Thanks!
Luca
next prev parent reply other threads:[~2022-10-18 14:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-09 6:08 [PATCH] linux-user: Implement faccessat2 WANG Xuerui
2022-10-10 8:53 ` Helge Deller
2022-10-18 9:58 ` Michael Tokarev
2022-10-18 13:05 ` Luca Bonissi [this message]
2022-10-21 15:37 ` Laurent Vivier
-- strict thread matches above, loose matches on Subject: below --
2022-07-29 20:14 Richard Henderson
2022-07-31 15:38 ` Richard Henderson
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