From: Sasha Levin <sashal@kernel.org>
To: Hauke Mehrtens <hauke@hauke-m.de>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
Victor Kamensky <kamensky@cisco.com>,
Bruce Ashfield <bruce.ashfield@gmail.com>,
Paul Burton <paulburton@kernel.org>,
linux-mips@vger.kernel.org, Ralf Baechle <ralf@linux-mips.org>,
James Hogan <jhogan@kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
richard.purdie@linuxfoundation.org,
Tony Ambardar <itugrok@yahoo.com>
Subject: Re: [PATCH AUTOSEL 5.4 10/58] mips: vdso: fix 'jalr t9' crash in vdso code
Date: Sat, 29 Aug 2020 09:56:56 -0400 [thread overview]
Message-ID: <20200829135656.GX8670@sasha-vm> (raw)
In-Reply-To: <d10c1981-ab79-86a9-4cf4-bd098d8c55f4@hauke-m.de>
On Sat, Aug 29, 2020 at 03:08:01PM +0200, Hauke Mehrtens wrote:
>On 3/5/20 6:13 PM, Sasha Levin wrote:
>> From: Victor Kamensky <kamensky@cisco.com>
>>
>> [ Upstream commit d3f703c4359ff06619b2322b91f69710453e6b6d ]
>>
>> Observed that when kernel is built with Yocto mips64-poky-linux-gcc,
>> and mips64-poky-linux-gnun32-gcc toolchain, resulting vdso contains
>> 'jalr t9' instructions in its code and since in vdso case nobody
>> sets GOT table code crashes when instruction reached. On other hand
>> observed that when kernel is built mips-poky-linux-gcc toolchain, the
>> same 'jalr t9' instruction are replaced with PC relative function
>> calls using 'bal' instructions.
>>
>> The difference boils down to -mrelax-pic-calls and -mexplicit-relocs
>> gcc options that gets different default values depending on gcc
>> target triplets and corresponding binutils. -mrelax-pic-calls got
>> enabled by default only in mips-poky-linux-gcc case. MIPS binutils
>> ld relies on R_MIPS_JALR relocation to convert 'jalr t9' into 'bal'
>> and such relocation is generated only if -mrelax-pic-calls option
>> is on.
>>
>> Please note 'jalr t9' conversion to 'bal' can happen only to static
>> functions. These static PIC calls use mips local GOT entries that
>> are supposed to be filled with start of DSO value by run-time linker
>> (missing in VDSO case) and they do not have dynamic relocations.
>> Global mips GOT entries must have dynamic relocations and they should
>> be prevented by cmd_vdso_check Makefile rule.
>>
>> Solution call out -mrelax-pic-calls and -mexplicit-relocs options
>> explicitly while compiling MIPS vdso code. That would get correct
>> and consistent between different toolchains behaviour.
>>
>> Reported-by: Bruce Ashfield <bruce.ashfield@gmail.com>
>> Signed-off-by: Victor Kamensky <kamensky@cisco.com>
>> Signed-off-by: Paul Burton <paulburton@kernel.org>
>> Cc: linux-mips@vger.kernel.org
>> Cc: Ralf Baechle <ralf@linux-mips.org>
>> Cc: James Hogan <jhogan@kernel.org>
>> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> Cc: richard.purdie@linuxfoundation.org
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>> ---
>> arch/mips/vdso/Makefile | 1 +
>> 1 file changed, 1 insertion(+)
>>
>
>Hi Sasha,
>
>Why was this not added to the 5.4 stable branch?
>
>Some OpenWrt users ran into this problem with kernel 5.4 on MIPS64 [0].
>We backported this patch on our own in OpenWrt [1], but it should be
>added to the sable branch in my opinion as it fixes a real problem.
>
>@Sasha: Can you add it to the 5.4 stable branch or should I send some
>special email?
It failed building on 5.4. If you'd like it included, please send me a
tested backport for 5.4.
--
Thanks,
Sasha
next prev parent reply other threads:[~2020-08-29 13:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200305171420.29595-1-sashal@kernel.org>
2020-03-05 17:13 ` [PATCH AUTOSEL 5.4 10/58] mips: vdso: fix 'jalr t9' crash in vdso code Sasha Levin
2020-08-29 13:08 ` Hauke Mehrtens
2020-08-29 13:56 ` Sasha Levin [this message]
2020-08-29 14:37 ` Hauke Mehrtens
2020-08-30 2:23 ` Sasha Levin
2020-03-05 17:13 ` [PATCH AUTOSEL 5.4 11/58] MIPS: Disable VDSO time functionality on microMIPS Sasha Levin
2020-03-05 17:13 ` [PATCH AUTOSEL 5.4 12/58] mips: vdso: add build time check that no 'jalr t9' calls left Sasha Levin
2020-03-05 17:13 ` [PATCH AUTOSEL 5.4 13/58] MIPS: VPE: Fix a double free and a memory leak in 'release_vpe()' Sasha Levin
2020-03-05 17:13 ` [PATCH AUTOSEL 5.4 17/58] MIPS: vdso: Wrap -mexplicit-relocs in cc-option Sasha Levin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200829135656.GX8670@sasha-vm \
--to=sashal@kernel.org \
--cc=bruce.ashfield@gmail.com \
--cc=hauke@hauke-m.de \
--cc=itugrok@yahoo.com \
--cc=jhogan@kernel.org \
--cc=kamensky@cisco.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=paulburton@kernel.org \
--cc=ralf@linux-mips.org \
--cc=richard.purdie@linuxfoundation.org \
--cc=stable@vger.kernel.org \
--cc=vincenzo.frascino@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).