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Re: [PATCH] Come up with --param asan-stack-small-redzone (PR sanitizer/81715).
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Martin Liška <mliska at suse dot cz>
- Cc: gcc-patches at gcc dot gnu dot org, arnd at linaro dot org
- Date: Thu, 29 Nov 2018 17:46:50 +0100
- Subject: Re: [PATCH] Come up with --param asan-stack-small-redzone (PR sanitizer/81715).
- References: <20180925092415.GC8250@tucnak> <9e39fc11-4c5b-0f84-785e-1e41306d2213@suse.cz> <20180925104022.GD8250@tucnak> <81ed697e-5dfb-be1a-cc3b-db93eb132b86@suse.cz> <20180925155325.GG8250@tucnak> <064bfab8-2d32-c1ba-7440-456d573347a8@suse.cz> <20181128114148.GY12380@tucnak> <9ecf5503-a919-1c1d-b88f-d049979848d8@suse.cz> <20181129151730.GM12380@tucnak> <2bbba0d0-e4a7-8d29-5f76-15da053cc786@suse.cz>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Thu, Nov 29, 2018 at 05:37:11PM +0100, Martin Liška wrote:
> 0x10007fff7b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x10007fff7b10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x10007fff7b20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x10007fff7b30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x10007fff7b40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> =>0x10007fff7b50: 00 00 00 00 f1 f1 f1 f1[01]f2 00 00 01 f2 f2 f2
> 0x10007fff7b60: f2 f2 00 00 00 06 f2 f2 f2 f2 00 00 00 00 00 f3
> 0x10007fff7b70: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
> 0x10007fff7b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x10007fff7b90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 0x10007fff7ba0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>
> as seen 06f2f2f2 is completely unaligned write.
Sure, but the whole frame section where the vars from one function are
is properly aligned. So, you shouldn't store 0xf2f2f206, but 0xf2f20600
one byte earlier, and then 0x0000f2f2 after it. Of course, if we decide
that we want to do solely SImode stores. If we want to complicate it
through determining costs and comparing if we should do a 1 or 2 or 4 byte
store and if unaligned is possible and not very expensive consider even
those in some cases, the code might be more complex.
I guess for now I'd be fine with SImode stores only and if we get complains,
we can address that incrementally (the question is if we'd want hooks or
what to determine it).
Jakub