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authorIngo Molnar <mingo@elte.hu>2010-10-30 04:43:08 -0400
committerIngo Molnar <mingo@elte.hu>2010-10-30 04:43:08 -0400
commit169ed55bd30305b933f52bfab32a58671d44ab68 (patch)
tree32e280957474f458901abfce16fa2a1687ef7497 /arch/x86/kernel/alternative.c
parent3d7851b3cdd43a734e5cc4c643fd886ab28ad4d5 (diff)
parent45f81b1c96d9793e47ce925d257ea693ce0b193e (diff)
Merge branch 'tip/perf/jump-label-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/urgent
Diffstat (limited to 'arch/x86/kernel/alternative.c')
-rw-r--r--arch/x86/kernel/alternative.c69
1 files changed, 15 insertions, 54 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index a36bb90aef53..0b30214282a8 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -644,65 +644,26 @@ void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len)
644 644
645#if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL) 645#if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL)
646 646
647unsigned char ideal_nop5[IDEAL_NOP_SIZE_5]; 647#ifdef CONFIG_X86_64
648unsigned char ideal_nop5[5] = { 0x66, 0x66, 0x66, 0x66, 0x90 };
649#else
650unsigned char ideal_nop5[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
651#endif
648 652
649void __init arch_init_ideal_nop5(void) 653void __init arch_init_ideal_nop5(void)
650{ 654{
651 extern const unsigned char ftrace_test_p6nop[];
652 extern const unsigned char ftrace_test_nop5[];
653 extern const unsigned char ftrace_test_jmp[];
654 int faulted = 0;
655
656 /* 655 /*
657 * There is no good nop for all x86 archs. 656 * There is no good nop for all x86 archs. This selection
658 * We will default to using the P6_NOP5, but first we 657 * algorithm should be unified with the one in find_nop_table(),
659 * will test to make sure that the nop will actually 658 * but this should be good enough for now.
660 * work on this CPU. If it faults, we will then
661 * go to a lesser efficient 5 byte nop. If that fails
662 * we then just use a jmp as our nop. This isn't the most
663 * efficient nop, but we can not use a multi part nop
664 * since we would then risk being preempted in the middle
665 * of that nop, and if we enabled tracing then, it might
666 * cause a system crash.
667 * 659 *
668 * TODO: check the cpuid to determine the best nop. 660 * For cases other than the ones below, use the safe (as in
661 * always functional) defaults above.
669 */ 662 */
670 asm volatile ( 663#ifdef CONFIG_X86_64
671 "ftrace_test_jmp:" 664 /* Don't use these on 32 bits due to broken virtualizers */
672 "jmp ftrace_test_p6nop\n" 665 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
673 "nop\n" 666 memcpy(ideal_nop5, p6_nops[5], 5);
674 "nop\n" 667#endif
675 "nop\n" /* 2 byte jmp + 3 bytes */
676 "ftrace_test_p6nop:"
677 P6_NOP5
678 "jmp 1f\n"
679 "ftrace_test_nop5:"
680 ".byte 0x66,0x66,0x66,0x66,0x90\n"
681 "1:"
682 ".section .fixup, \"ax\"\n"
683 "2: movl $1, %0\n"
684 " jmp ftrace_test_nop5\n"
685 "3: movl $2, %0\n"
686 " jmp 1b\n"
687 ".previous\n"
688 _ASM_EXTABLE(ftrace_test_p6nop, 2b)
689 _ASM_EXTABLE(ftrace_test_nop5, 3b)
690 : "=r"(faulted) : "0" (faulted));
691
692 switch (faulted) {
693 case 0:
694 pr_info("converting mcount calls to 0f 1f 44 00 00\n");
695 memcpy(ideal_nop5, ftrace_test_p6nop, IDEAL_NOP_SIZE_5);
696 break;
697 case 1:
698 pr_info("converting mcount calls to 66 66 66 66 90\n");
699 memcpy(ideal_nop5, ftrace_test_nop5, IDEAL_NOP_SIZE_5);
700 break;
701 case 2:
702 pr_info("converting mcount calls to jmp . + 5\n");
703 memcpy(ideal_nop5, ftrace_test_jmp, IDEAL_NOP_SIZE_5);
704 break;
705 }
706
707} 668}
708#endif 669#endif