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Message-ID: <20200226095624.GG14278@port70.net>
Date: Wed, 26 Feb 2020 10:56:24 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: Tobias Koch <tobias.koch@...terra.com>
Cc: musl@...ts.openwall.com
Subject: Re: Crash on (qemu'ed) s390x doing prlimit call after probing
stack size
* Tobias Koch <tobias.koch@...terra.com> [2020-02-26 01:07:58 +0300]:
> I have some programs crashing on me under QEMU s390x user emulation. I see
> them probe the stack size using mremaps and then do a prlimit as in this
> snippet
>
> 24948 mremap(274877911040,4096,8192,0,0,56) = -1 errno=12 (Cannot allocate
> memory)
> 24948 mremap(274877906944,4096,8192,0,0,56) = -1 errno=12 (Cannot allocate
> memory)
> 24948 mremap(274877902848,4096,8192,0,0,56) = -1 errno=14 (Bad address)
> 24948 prlimit64(0,3,0,274889373840,274879934536,56) = 0
> --- SIGSEGV {si_signo=SIGSEGV, si_code=1, si_addr=0x0000004000001000} ---
> Segmentation fault
i'd use
qemu-s390x -d page -strace exe
to see how 0x0000004000001000 is mapped and then
qemu-s390x -d page,in_asm,cpu,nochain -strace exe
to see the exact failing instruction, that may give a hint.
>
> The same programs on other 64bit arches (such as aarch64 or powerpc64le)
> emluated with QEMU work OK. I'm trying to understand, what musl is doing
> here and why QEMU cannot handle it.Any pointers would be appreciated.
>
> Tobias
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