Messages in this thread Patch in this message | | | Date | Wed, 16 Jul 2008 22:57:38 -0400 | From | Mathieu Desnoyers <> | Subject | Immedate Values Optimized Jump Fix |
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I rarely emit a single patch for a fix wrt LTTng (I usually just release a new version), but this one is worth it. It will be in 0.11 pretty soon, but if you want to apply it to 0.10 meanwhile, it's highly recommended.
Caused a kernel OOPS when loading the tracepoint probes once in a while on a 8-way x86_64.
Immedate Values Optimized Jump Fix
Fix the immediate values optimized jump fallback, which parameters were wrong following the last changes. It should be a 5 bytes instruction (not 2) with a 4 bytes operand.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> --- arch/x86/kernel/immediate.c | 2 +- include/asm-x86/immediate.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
Index: linux-2.6-lttng/arch/x86/kernel/immediate.c =================================================================== --- linux-2.6-lttng.orig/arch/x86/kernel/immediate.c 2008-07-16 22:50:35.000000000 -0400 +++ linux-2.6-lttng/arch/x86/kernel/immediate.c 2008-07-16 22:51:07.000000000 -0400 @@ -500,7 +500,7 @@ __kprobes int arch_imv_update(struct __i "Jump target fallback at %lX, nr fail %d\n", imv->imv, ++nr_fail); #endif - imv->size = 1; + imv->size = 4; /* Fallback on movl */ } else { #ifdef DEBUG_IMMEDIATE static int nr_success; Index: linux-2.6-lttng/include/asm-x86/immediate.h =================================================================== --- linux-2.6-lttng.orig/include/asm-x86/immediate.h 2008-07-16 22:49:19.000000000 -0400 +++ linux-2.6-lttng/include/asm-x86/immediate.h 2008-07-16 22:51:07.000000000 -0400 @@ -132,7 +132,7 @@ struct __imv { BUILD_BUG_ON(sizeof(__typeof__(name##__imv)) > 1); \ asm (".section __imv,\"aw\",@progbits\n\t" \ _ASM_PTR "%c1, (3f)-4\n\t" \ - ".byte 0, 2\n\t" \ + ".byte 0, 5\n\t" \ ".previous\n\t" \ "mov $0,%0\n\t" \ "3:\n\t" \ -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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