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

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Date:   Mon, 13 Sep 2021 15:57:08 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Guenter Roeck' <linux@...ck-us.net>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     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>,
        Max Filippov <jcmvbkbc@...il.com>
Subject: RE: [PATCH] xtensa: Increase size of gcc stack frame check

From: Guenter Roeck
> Sent: 12 September 2021 03:53
> 
> 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.

Have you done anything to check what happens at run-time?
I'd guess that the deepest stack use is inside printk() in
some obscure error path.

In reality all these 1k+ stack frames need killing
rather than the limit for the compiler warning increased.

While it may be sensible for a system call entry function
so allocate a reasonable size buffer on stack (as poll()
and sendmsg() probably do) allocating big buffers way
down the call stack could easily cause stack overflow.
Even a 1k stack frame is huge.

	David

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