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

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Message-ID: <CAMo8BfLOhr8Gw9RbSM_pVhgokDcBZ3PgwQAG6sCxDBAm_rMy7Q@mail.gmail.com>
Date:   Tue, 14 Sep 2021 00:04:56 -0700
From:   Max Filippov <jcmvbkbc@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     David Laight <David.Laight@...lab.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "linux-xtensa@...ux-xtensa.org" <linux-xtensa@...ux-xtensa.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chris Zankel <chris@...kel.net>
Subject: Re: [PATCH] xtensa: Increase size of gcc stack frame check

On Mon, Sep 13, 2021 at 9:11 AM Guenter Roeck <linux@...ck-us.net> wrote:
> The functions I checked typically have pretty large local data
> (like, more than 700-800 bytes). The errors are only observed
> with xtensa:allmodconfig test builds. While it may be arguable
> if those functions really need that much data on the stack, it
> is unreasonable to assume that all those errors (again, more
> than 50) are ever going to get fixed, especially since the errors
> are only seen with xtensa and not with any other architecture

That's not what I observe. If I build allmodconfig on v5.15-rc1
for arm with gcc-8.3 I get 69 of them.

> (including parisc; setting a stack limit of 1024 works just fine
> with that architecture, at least with gcc 11.x). So the realistic

This comparison is a bit biased because allmodconfig on xtensa
enables KASAN which is not supported by the parisc. Disabling
KASAN roughly halves the size of stack frames for a few
instances that I've checked.

-- 
Thanks.
-- Max