valgrind on amd64 crashes when delivering signal for threaded application

[Stanislav Sedov]

On Apr 23, 2014, at 1:01 PM, Mikolaj Golub <trociny at freebsd.org> wrote:

>  --- coregrind/m_sigframe/sigframe-amd64-freebsd.c.orig  2014-04-23 22:39:45.000000000 +0300
>  +++ coregrind/m_sigframe/sigframe-amd64-freebsd.c       2014-04-23 22:40:23.000000000 +0300
>  @@ -250,7 +250,7 @@ static Addr build_sigframe(ThreadState *
>      UWord err;
> 
>      rsp -= sizeof(*frame);
>  -   rsp = VG_ROUNDDN(rsp, 16);
>  +   rsp = VG_ROUNDDN(rsp, 16) - 8;
>      frame = (struct sigframe *)rsp;
> 
>      if (!extend(tst, rsp, sizeof(*frame)))
> 
> Unfortunately, I have poor understanding of valgrind internals and
> what is going on exactly when it delivers a signal to the process, so
> failed to find a proper fix.

This sounds like a proper solution to me though.  Stack handling in valgrind
is indeed convoluted, but it seems in this case it clearly misaligns the stack
as it does not take into account the return address.  Any objections if I commit
this fix to valgrind-freebsd?

Thanks a lot for tracking this!

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ST4096-RIPE