Re: [Qemu-devel] qemu-user-x86_64 segfaults on armv5 (WAS: qemu-user + networking issues / segfaults)

[Christof Schulze]

Hello

Richard, using your vdso patch from today that takes into account vtime
as well, running linux-x86_64 code on arm via qemu-user works! Thank you
very much for your support and energy! 

As promised on IRC the software is dead-slow but I do not mind since it
is a batch application anyways.

I only wonder why this is not in the master branch.

Christof

Am Freitag, 6. September 2013, 12:38:21 schrieb Christof Schulze:
> Hello

> Am Mittwoch, 4. September 2013, 08:35:37 schrieb Richard Henderson:
> > On 08/29/2013 02:27 PM, Christof Schulze wrote:
> > > #5  0x6012a100 in tb_gen_code (env=0x612def20, pc=18446744073699066880,
> > > cs_base=0, flags=4243635, cflags=0)

> > >     at /mnt/data/build/qemu-1.6.0-ministatic/translate-all.c:964

> > In know exactly what this is -- the fallback vsyscall page.

> > I've had a patch set around for the last three years or so to provide
> > a real vdso for x86_64.  I repost it every so often, usually to no
> > response.

> > See git://github.com/rth7680/qemu.git elfload-vdso

> after trying the patch itself and still getting slightly other crashes
> on irc we decided to try this patch based on the master branch. This
> allowed for debugging with gdb as it circumvented a bug of the early
> 1.6rcs of qemu where the g packet was transmitting two many registers.


> Having set a breakpoint at *0x0000000040816725 (the memory position
> where the segfault happens) I got the following
> output.

> Loaded symbols for /lib64/ld-linux-x86-64.so.2
> 0x0000000040802650 in _start () from /lib64/ld-linux-x86-64.so.2
> (gdb) b *0x0000000040816725
> Haltepunkt 1 at 0x40816725: file ../sysdeps/x86_64/dl-trampoline.S, line 46.
> (gdb) cont
> Continuing.
> Breakpoint 1, _dl_runtime_resolve () at ../sysdeps/x86_64/dl-trampoline.S:46
> 46    ../sysdeps/x86_64/dl-trampoline.S: Datei oder Verzeichnis nicht
> gefunden. it says dl-trampoline.S: file or directory not found and gives me
> the gdb shell

> Breakpoint 1, _dl_runtime_resolve () at ../sysdeps/x86_64/dl-trampoline.S:46
> 46    in ../sysdeps/x86_64/dl-trampoline.S
> (gdb)
> Continuing.
> Program received signal SIGSEGV, Segmentation fault.
> 0xffffffffff600400 in ?? ()

> RTH mentioned that the runtime resolution of the symbol was into the
> vsyscall page.

> Now I am unsure where I should go from this point.
> Should I collect more data? If so, what exactly is needed?
> What else could I do to get this resolved?

> Christof
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