Date: Tue, 7 Mar 2017 16:45:40 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: musl segfaulting when compiled with -O2 On Tue, Mar 07, 2017 at 05:55:29PM -0300, Breno Leitao wrote: > Hi Rich, > > On Tue, Mar 07, 2017 at 03:39:05PM -0500, Rich Felker wrote: > > On Tue, Mar 07, 2017 at 05:32:35PM -0300, Breno Leitao wrote: > > > Musl package on Debian on ppc64le is broken. > > > > > > When running any software with it, it segfaults. Doing a little bit of > > > debugging I found that libc.so is broken. > > > > > > I got the upstream code, and found that the problme is also > > > reproducible. > > > > > > I found that the problem only happen when compiling with -O2 and -O3. If > > > I compile musl with -O1 or -O0, the problm does not happen. > > > > > > This is the bt of the code that crashes: > > > > > > (gdb) bt > > > #0 0x0000000148b84dc0 in ?? () > > > #1 0x0000000048bdb8dc in _dlstart_c (sp=0x3fffc33294b0, dynv=<optimized out>) at ldso/dlstart.c:147 > > > #2 0x0000000048bdebe0 in _dlstart () > > > > > > (gdb) up > > > #1 0x0000000048bdb8dc in _dlstart_c (sp=0x3fffc33294b0, dynv=<optimized out>) at ldso/dlstart.c:147 > > > 147 dls2((void *)base, sp); > > > > > > $ gcc --version > > > gcc (Debian 6.3.0-5) 6.3.0 20170124 > > > > > > Not sure if this is a GCC issue or a musl issue now. > > > > Can you post the crashing libc.so somewhere? Depending on how they're > > building it, the problem could be in various different places. A > > glibc-targeted powerpc* gcc is not suitable for compiling musl, since > > it has various ABI mismatches, but that's probably not what you're > > seeing here even if one was used. > > Sure. You can grab it directly from Debian: > > $ wget http://cdn-fastly.deb.debian.org/debian/pool/main/m/musl/musl_1.1.16-2_ppc64el.deb > > $ dpkg-deb -x musl_1.1.16-2_ppc64el.deb . > > $ lib/powerpc64le-linux-musl/libc.so >  25672 segmentation fault (core dumped) lib/powerpc64le-linux-musl/libc.so Can you do a register dump and a dissassembly dump and around the point that crashes? The Debian package is fully stripped (lacks debug symbols) so it's hard to follow what it's doing, but I didn't see anything obviously wrong. Rich
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