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Message-ID: <20150106225647.GA2194@newbook>
Date: Tue, 6 Jan 2015 14:56:50 -0800
From: Isaac Dunham <ibid.ag@...il.com>
To: musl@...ts.openwall.com
Subject: Re: musl built with pcc yields segfaults in dynlink.c

On Tue, Jan 06, 2015 at 03:49:24PM -0500, Rich Felker wrote:
> On Mon, Jan 05, 2015 at 11:48:50PM -0800, Isaac Dunham wrote:
> > Hello,
> > I'm trying to get a pcc-built libc.so that works.
> > With the latest PCC, musl builds (lib/libc.so) and the result will display
> > the proper messages if run from the command line without arguments.
> > However, if I try to run a program with it 
> > (even via -Wl,-dynamic-linker,`pwd`/lib/libc.so), I get a segfault
> > in src/ldso/dynlink.c:
> > (gdb) where
> > #0  sysv_hash (s0=0x0, s0=0x0) at src/ldso/dynlink.c:177
> > #1  0xb7f6f747 in find_sym (dso=0xbffffb18, rel=0xb7ffe1d4 <.L1502>, 
> >     rel_size=<unknown type>, stride=<unknown type>, dso=0xbffffb18, 
> >     rel=0xb7ffe1d4 <.L1502>, rel_size=<unknown type>, stride=<unknown type>)
> >     at src/ldso/dynlink.c:251
> >     #2  0xb7f6f916 in do_relocs () at src/ldso/dynlink.c:308
> >     Backtrace stopped: frame did not save the PC
> > 
> > I'm using Alpine Linux edge, recently updated, with linux-vanilla.
> 
> It would be helpful to see the readelf -a output for libc.so and the
> binary using it, and whatever information gdb can give on the value of
> local vars at each of the above call frames.

Attaching a tar.xz containing the output of:
- readelf -a lib/libc.so:	libc-pcc.readelf
- readelf -a a.out:		argvname.readelf
- echo -e 'run\nwhere\nbt full' |gdb ./a.out:	argvname.gdb
 (which is substantially similar to the output for "lib/libc.so ./a.out")
- and the source for a.out:	argvname.c

It's 51k, so I'm hoping it gets through.

Thanks,
Isaac Dunham

Download attachment "pcclibc.tar.xz" of type "application/octet-stream" (53072 bytes)

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