On Mon, May 03, 2010 at 10:44:21PM +0200, Helge Deller wrote: > On 12/14/2009 11:08 PM, Thibaut Paumard wrote: > > Le 14 déc. 09 à 16:06, Carlos O'Donell a écrit : > > Attached is a rather small testcase. > > > > Compile with > > gcc -lm -o fputest fputest.c > > > > Run with > > ./fputest > > or with any succession of 'i's and 'f's, e.g. > > ./fputest iffifi > > > > The expected behaviour (checked on i386) is that for each f or i letter, > > a line is output, for instance > > $ ./fputest iffi > > Triggering integer SIGFPE: 1/0=(SIGFPE trapped)0 > > Triggering floating SIGFPE: 1./0.=(SIGFPE trapped)0.000000 > > Triggering floating SIGFPE: 1./0.=(SIGFPE trapped)0.000000 > > Triggering integer SIGFPE: 1/0=(SIGFPE trapped)0 > > $ echo $? > > 0 > > > > All the SIGFPEs should be trapped and the program should exit gracefully > > (check $?). > > > > Under HPPA, the integer SIGFPEs are trapped but the floating-point > > SIGFPEs are not: > > $ ./fputest iffi > > Triggering integer SIGFPE: 1/0=(SIGFPE trapped)0 > > Triggering floating SIGFPE: 1./0.=Floating point exception > > $ echo $? > > 136 > > > The problem in this test case is, that a signal handler is called > when SIGFPE happens. Then glibc uses a trampoline handler to call the > signal handler, in which it touches the floating point registers again > and finally gets another SIGFPE. In this case, the program just ends > (since the original signal handler already trapped). > Involved glibc function is _dl_runtime_resolve() at > ports/sysdeps/hppa/dl-trampoline.S:73 > > The solution is simple. > Just clear the exception register in arch/parisc/math-emu/decode_exc.c > in the linux kernel before sending the SIGFPE signal to user space. > > Patch attached. > > While at this, I think we need to clear the exception registers for > the other cases like OVERFLOWEXCEPTION and INEXACTEXCEPTION at least > as well (see arch/parisc/math-emu/decode_exc.c, line 286 ff). > > Helge > > Patch: > ------------------------- > [PATCH] parisc: clear floating point exception flag on SIGFPE signal > > Clear the floating point exception flag before returning to > user space. This is needed, else the libc trampoline handler > may hit the same SIGFPE again while building up a trampoline > to a signal handler. > > Fixes debian bug #559406. > > Signed-off-by: Helge Deller <del...@gmx.de>
Thanks Helge! If you can poke me when this goes into Kyle's tree, I'll get it added to Debian. > diff --git a/arch/parisc/math-emu/decode_exc.c > b/arch/parisc/math-emu/decode_exc.c > index 3ca1c61..27a7492 100644 > --- a/arch/parisc/math-emu/decode_exc.c > +++ b/arch/parisc/math-emu/decode_exc.c > @@ -342,6 +342,7 @@ decode_fpu(unsigned int Fpu_register[], unsigned int > trap_counts[]) > return SIGNALCODE(SIGFPE, FPE_FLTINV); > case DIVISIONBYZEROEXCEPTION: > update_trap_counts(Fpu_register, aflags, bflags, trap_counts); > + Clear_excp_register(exception_index); > return SIGNALCODE(SIGFPE, FPE_FLTDIV); > case INEXACTEXCEPTION: > update_trap_counts(Fpu_register, aflags, bflags, trap_counts); > > -- dann frazier -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
