linux-kernel - Re: [PATCH] xtensa: Increase size of gcc stack frame check

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Message-ID: <49f8f332-a964-5b98-64c6-9fa5d028731a@roeck-us.net>
Date:   Sat, 11 Sep 2021 21:02:47 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Max Filippov <jcmvbkbc@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "open list:TENSILICA XTENSA PORT (xtensa)" 
        <linux-xtensa@...ux-xtensa.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Chris Zankel <chris@...kel.net>
Subject: Re: [PATCH] xtensa: Increase size of gcc stack frame check

On 9/11/21 8:05 PM, Max Filippov wrote:
> On Sat, Sep 11, 2021 at 7:52 PM Guenter Roeck <linux@...ck-us.net> wrote:
>>
>> xtensa frame size is larger than the frame size for almost all other
>> architectures. This results in more than 50 "the frame size of <n> is
>> larger than 1024 bytes" errors when trying to build xtensa:allmodconfig.
>>
>> Increase frame size for xtensa to 1536 bytes to avoid compile errors
>> due to frame size limits.
>>
>> Cc: Chris Zankel <chris@...kel.net>
>> Cc: Max Filippov <jcmvbkbc@...il.com>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>>   lib/Kconfig.debug | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index ed4a31e34098..afad11e57d6b 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -346,7 +346,7 @@ config FRAME_WARN
>>          int "Warn for stack frames larger than"
>>          range 0 8192
>>          default 2048 if GCC_PLUGIN_LATENT_ENTROPY
>> -       default 1536 if (!64BIT && PARISC)
>> +       default 1536 if (!64BIT && (PARISC || XTENSA))
>>          default 1024 if (!64BIT && !PARISC)
> 
> Shouldn't that line also be changed to
>    default 1024 if (!64BIT && !(PARISC || XTENSA))
> ?

I could do that, but I tested it and it looks like the evaluation
is top-down, so it didn't seem necessary or useful. For example,
the default value is 2048 for 32-bit systems (such as arm, riscv32,
or i386) if GCC_PLUGIN_LATENT_ENTROPY is enabled, even though the
line with the default of 1024 matches as well.

Thanks,
Guenter