On 05/03/2010 11:42 PM, dann frazier wrote: > 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 <[email protected]> > > Thanks Helge! If you can poke me when this goes into Kyle's tree, I'll > get it added to Debian.
Hi Dan, the patch was now applied to Kyle's tree and will be in Linus upstream Kernel 2.6.35: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=550f0d922286556c7ea43974bb7921effb5a5278 Best regards, Helge > >> 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); >> >> > -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: http://lists.debian.org/[email protected]
