linux-kernel - Re: [PATCH] riscv: Disable STACKPROTECTOR_PER_TASK if GCC_PLUGIN

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Message-ID: <9a2918b0-0c85-7e56-58e0-d2ea0ea10068@roeck-us.net>
Date:   Tue, 3 Aug 2021 22:25:29 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        guoren@...ux.alibaba.com
Subject: Re: [PATCH] riscv: Disable STACKPROTECTOR_PER_TASK if
 GCC_PLUGIN_RANDSTRUCT is enabled

On 8/3/21 10:14 PM, Palmer Dabbelt wrote:
> On Fri, 23 Jul 2021 17:58:13 PDT (-0700), Palmer Dabbelt wrote:
>> On Tue, 06 Jul 2021 09:26:21 PDT (-0700), linux@...ck-us.net wrote:
>>> riscv uses the value of TSK_STACK_CANARY to set
>>> stack-protector-guard-offset. With GCC_PLUGIN_RANDSTRUCT enabled, that
>>> value is non-deterministic, and with riscv:allmodconfig often results
>>> in build errors such as
>>>
>>> cc1: error: '8120' is not a valid offset in '-mstack-protector-guard-offset='
>>>
>>> Enable STACKPROTECTOR_PER_TASK only if GCC_PLUGIN_RANDSTRUCT is disabled
>>> to fix the problem.
>>>
>>> Fixes: fea2fed201ee5 ("riscv: Enable per-task stack canaries")
>>> Cc: Guo Ren <guoren@...ux.alibaba.com>
>>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>>> ---
>>>  arch/riscv/Kconfig | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>>> index 469a70bd8da6..3afb84fa2190 100644
>>> --- a/arch/riscv/Kconfig
>>> +++ b/arch/riscv/Kconfig
>>> @@ -486,6 +486,7 @@ config CC_HAVE_STACKPROTECTOR_TLS
>>>
>>>  config STACKPROTECTOR_PER_TASK
>>>      def_bool y
>>> +    depends on !GCC_PLUGIN_RANDSTRUCT
>>>      depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
>>>
>>>  config PHYS_RAM_BASE_FIXED
>>
>> Thanks, this is on fixes.  I do an allmodconfig build and haven't seen
>> these failures, is there something special I need to do to get this
>> working?  I know nothing about GCC plugins...
> 
> Sorry, looks like I screwed something up and I didn't actually merge this onto fixes.  Not sure what happened, but this time it should actually be on fixes.

Ah, I thought you decided not to apply it for some reason. I changed
my test scripts to always disable GCC_PLUGIN_RANDSTRUCT for riscv
build tests and stopped reporting the problem. I mentioned this
a couple of weeks ago in my test reports. Just in case you wondered.

Guenter