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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Guenter Roeck' <linux@roeck-us.net>,
        Andrew Morton <akpm@linux-foundation.org>
CC:     Masahiro Yamada <masahiroy@kernel.org>,
        "linux-xtensa@linux-xtensa.org" <linux-xtensa@linux-xtensa.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Chris Zankel <chris@zankel.net>,
        Max Filippov <jcmvbkbc@gmail.com>
Subject: RE: [PATCH] xtensa: Increase size of gcc stack frame check
Thread-Topic: [PATCH] xtensa: Increase size of gcc stack frame check
Thread-Index: AQHXp4FD14pA8IBSYEm3jyWL1V8qFauiH7lQ
Date:   Mon, 13 Sep 2021 15:57:08 +0000
Message-ID: <315e4a23990444f585a15d2e23a39b8f@AcuMS.aculab.com>
References: <20210912025235.3514761-1-linux@roeck-us.net>
In-Reply-To: <20210912025235.3514761-1-linux@roeck-us.net>
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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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