From: Paul Burton <paulburton@kernel.org>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"open list:BROADCOM NVRAM DRIVER" <linux-mips@vger.kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Christian Brauner <christian.brauner@canonical.com>
Subject: Re: [PATCH] mips: vdso: conditionalize 32-bit time functions on COMPAT_32BIT_TIME
Date: Tue, 31 Dec 2019 20:25:00 -0800 [thread overview]
Message-ID: <20200101042500.zmhldrthr3l45trq@lantea.localdomain> (raw)
In-Reply-To: <20200101041056.xionott76qbrffih@lantea.localdomain>
Hi Jason,
On Tue, Dec 31, 2019 at 08:10:56PM -0800, Paul Burton wrote:
> I'm still not quite sure *why* this happens; perhaps GCC just decides it
> doesn't need to save & restore $gp/$28 when it spots that it's being
> "used" for __current_thread_info (even though that's never actually
> referenced in the VDSO)?
Ah:
> After defining a global register variable, for the current compilation
> unit:
>
> - If the register is a call-saved register, call ABI is affected: the
> register will not be restored in function epilogue sequences after
> the variable has been assigned. Therefore, functions cannot safely
> return to callers that assume standard ABI.
https://gcc.gnu.org/onlinedocs/gcc/Global-Register-Variables.html
That makes sense then. What doesn't make sense is how this ever
worked. A question for another day...
Thanks,
Paul
next prev parent reply other threads:[~2020-01-01 4:22 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-23 13:08 vdso-related userspace crashes on 5.5 mips64 Jason A. Donenfeld
2019-12-23 21:44 ` Jason A. Donenfeld
2019-12-23 23:29 ` Paul Burton
2019-12-24 13:37 ` Jason A. Donenfeld
2019-12-30 15:58 ` Arnd Bergmann
2019-12-24 14:19 ` Jason A. Donenfeld
2019-12-24 13:54 ` [PATCH] mips: vdso: conditionalize 32-bit time functions on COMPAT_32BIT_TIME Jason A. Donenfeld
2019-12-30 11:57 ` Arnd Bergmann
2019-12-30 12:26 ` Jason A. Donenfeld
2019-12-30 12:34 ` Arnd Bergmann
2019-12-30 14:37 ` Jason A. Donenfeld
2019-12-30 15:10 ` Jason A. Donenfeld
2019-12-30 15:37 ` Arnd Bergmann
2019-12-30 15:39 ` Jason A. Donenfeld
2019-12-30 15:47 ` Arnd Bergmann
2019-12-30 15:58 ` Jason A. Donenfeld
2019-12-30 17:33 ` Arnd Bergmann
2019-12-30 21:09 ` Jason A. Donenfeld
2019-12-30 21:42 ` Jason A. Donenfeld
2019-12-31 16:14 ` Jason A. Donenfeld
2020-01-01 4:10 ` Paul Burton
2020-01-01 4:25 ` Paul Burton [this message]
2020-01-01 9:47 ` Jason A. Donenfeld
2020-01-01 9:47 ` Jason A. Donenfeld
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