From: Thomas Gleixner <tglx@linutronix.de>
To: Ammar Faizi <ammarfaizi2@gnuweeb.org>, Borislav Petkov <bp@alien8.de>
Cc: Ammar Faizi <ammarfaizi2@gnuweeb.org>,
Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Tony Luck <tony.luck@intel.com>,
Yazen Ghannam <yazen.ghannam@amd.com>,
Linux Edac Mailing List <linux-edac@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Stable Kernel <stable@vger.kernel.org>,
GNU/Weeb Mailing List <gwml@vger.gnuweeb.org>,
x86 Mailing List <x86@kernel.org>,
David Laight <David.Laight@ACULAB.COM>,
Jiri Hladky <hladky.jiri@googlemail.com>
Subject: Re: [PATCH v6 1/2] x86/delay: Fix the wrong asm constraint in `delay_loop()`
Date: Sun, 03 Apr 2022 19:14:34 +0200 [thread overview]
Message-ID: <87tubaks1x.ffs@tglx> (raw)
In-Reply-To: <87zgl2ksu3.ffs@tglx>
On Sun, Apr 03 2022 at 18:57, Thomas Gleixner wrote:
> On Tue, Mar 29 2022 at 17:47, Ammar Faizi wrote:
>> The asm constraint does not reflect that the asm statement can modify
>> the value of @loops. But the asm statement in delay_loop() does modify
>> the @loops.
>>
>> Specifiying the wrong constraint may lead to undefined behavior, it may
>> clobber random stuff (e.g. local variable, important temporary value in
>> regs, etc.). This is especially dangerous when the compiler decides to
>> inline the function and since it doesn't know that the value gets
>> modified, it might decide to use it from a register directly without
>> reloading it.
Ignore me, I misread this part of the explanation.
Thanks,
tglx
next prev parent reply other threads:[~2022-04-03 17:14 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-29 10:47 [PATCH v6 0/2] Two x86 fixes Ammar Faizi
2022-03-29 10:47 ` [PATCH v6 1/2] x86/delay: Fix the wrong asm constraint in `delay_loop()` Ammar Faizi
2022-04-01 17:42 ` Dave Hansen
2022-04-02 5:15 ` Ammar Faizi
2022-04-03 16:57 ` Thomas Gleixner
2022-04-03 17:11 ` Ammar Faizi
2022-04-03 17:14 ` Thomas Gleixner [this message]
2022-04-05 20:50 ` [tip: x86/misc] x86/delay: Fix the wrong asm constraint in delay_loop() tip-bot2 for Ammar Faizi
2022-03-29 10:47 ` [PATCH v6 2/2] x86/MCE/AMD: Fix memory leak when `threshold_create_bank()` fails Ammar Faizi
2022-04-03 17:03 ` Thomas Gleixner
2022-04-03 17:43 ` Ammar Faizi
2022-04-03 17:45 ` Ammar Faizi
2022-04-03 18:46 ` Borislav Petkov
2022-04-05 20:56 ` [tip: ras/core] x86/MCE/AMD: Fix memory leak when threshold_create_bank() fails tip-bot2 for Ammar Faizi
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