Messages in this thread Patch in this message | | | Date | Tue, 18 Jan 2005 03:12:45 +0200 | From | Juho Snellman <> | Subject | x86-64: int3 no longer causes SIGTRAP in 2.6.10 |
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2.6.10 changed the behaviour of the int3 instruction on x86-64. It used to result in a SIGTRAP, now it's a SIGSEGV in both native and 32-bit legacy modes. This was apparently caused by the kprobe port, specifically this part:
--- a/arch/x86_64/kernel/traps.c 2004-12-24 13:36:17 -08:00 +++ b/arch/x86_64/kernel/traps.c 2004-12-24 13:36:17 -08:00 @@ -862,8 +910,8 @@ set_intr_gate(0,÷_error); set_intr_gate_ist(1,&debug,DEBUG_STACK); set_intr_gate_ist(2,&nmi,NMI_STACK); - set_system_gate(3,&int3); /* int3-5 can be called from all */ - set_system_gate(4,&overflow); + set_intr_gate(3,&int3); + set_system_gate(4,&overflow); /* int4-5 can be called from all */
Was effectively disabling int3 a conscious decision, or just an unintended side-effect? This breaks at least Steel Bank Common Lisp (x86 and x86-64) and CMU Common Lisp (x86), which use int3 for error traps and breakpoints.
Simple test case:
% cat foo.c int main (void) { asm("int3"); return 0; } % gcc -o foo foo.c % ./foo zsh: trace trap ./foo % gcc -m32 -o foo-32 foo.c % ./foo-32 zsh: trace trap ./foo-32 [ reboot ]
% uname -a Linux kiki 2.6.10 #2 Sun Dec 26 04:54:05 EET 2004 x86_64 x86_64 x86_64 % ./foo zsh: segmentation fault ./foo % ./foo-32 zsh: segmentation fault ./foo-32
-- Juho Snellman - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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