From: Johannes Berg <johannes@sipsolutions.net>
To: YiFei Zhu <zhuyifei1999@gmail.com>,
Colin Ian King <colin.king@canonical.com>
Cc: linux-um@lists.infradead.org, Jeff Dike <jdike@addtoit.com>,
Richard Weinberger <richard@nod.at>,
Anton Ivanov <anton.ivanov@cambridgegreys.com>,
Benjamin Berg <benjamin@sipsolutions.net>
Subject: Re: [PATCH v2] um: Fix stack pointer alignment
Date: Tue, 20 Apr 2021 08:51:17 +0200 [thread overview]
Message-ID: <4f6922f1739dc675d50130a3c07bf28a2bc6f380.camel@sipsolutions.net> (raw)
In-Reply-To: <CABqSeAQdwhJCTyO9w6f2cmyobh2bnA5wG6ZgCS9gD0b7ZSi=yw@mail.gmail.com> (sfid-20210420_074740_851869_49DF5D49)
>
> It seems config related. I tested with my original config and it
> segfault loops, but then I tested with a fresh defconfig, then enabled
> RTC_CLASS and UML_RTC and it boots successfully, with the assembly as:
>
> movaps (%rdx),%xmm0
> movaps %xmm0,(%r12)
>
> The move from xmm0 to stack is omitted.
>
> After a bit of trial and error I found changing from
> CC_OPTIMIZE_FOR_SIZE to CC_OPTIMIZE_FOR_PERFORMANCE alone makes the
> difference. What's also interesting is that instead of
> segfault-looping (as in, segfault recovery did not do anything to fix
> the fault, so after sigreturn it segfaults again), it panics with
> "Segfault with no mm" which seems more like the expected behavior.
Aha, interesting.
>
> I'll send a v3 to clarify CC_OPTIMIZE_FOR_PERFORMANCE.
Cool, thanks for all the digging and fixes!
johannes
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next prev parent reply other threads:[~2021-04-20 6:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 15:32 [PATCH v2] um: Fix stack pointer alignment YiFei Zhu
2021-04-19 19:41 ` Johannes Berg
2021-04-19 20:36 ` YiFei Zhu
2021-04-20 5:47 ` YiFei Zhu
2021-04-20 6:20 ` YiFei Zhu
2021-04-20 6:51 ` Johannes Berg [this message]
2021-04-20 6:50 ` Johannes Berg
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