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

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)
 
 #if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL)
 
-unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
+#ifdef CONFIG_X86_64
+unsigned char ideal_nop5[5] = { 0x66, 0x66, 0x66, 0x66, 0x90 };
+#else
+unsigned char ideal_nop5[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 };
+#endif
 
 void __init arch_init_ideal_nop5(void)
 {
-        extern const unsigned char ftrace_test_p6nop[];
-        extern const unsigned char ftrace_test_nop5[];
-        extern const unsigned char ftrace_test_jmp[];
-        int faulted = 0;
-
         /*
-         * There is no good nop for all x86 archs.
-         * We will default to using the P6_NOP5, but first we
-         * will test to make sure that the nop will actually
-         * work on this CPU. If it faults, we will then
-         * go to a lesser efficient 5 byte nop. If that fails
-         * we then just use a jmp as our nop. This isn't the most
-         * efficient nop, but we can not use a multi part nop
-         * since we would then risk being preempted in the middle
-         * of that nop, and if we enabled tracing then, it might
-         * cause a system crash.
+         * There is no good nop for all x86 archs.  This selection
+         * algorithm should be unified with the one in find_nop_table(),
+         * but this should be good enough for now.
          *
-         * TODO: check the cpuid to determine the best nop.
+         * For cases other than the ones below, use the safe (as in
+         * always functional) defaults above.
          */
-        asm volatile (
-                "ftrace_test_jmp:"
-                "jmp ftrace_test_p6nop\n"
-                "nop\n"
-                "nop\n"
-                "nop\n"  /* 2 byte jmp + 3 bytes */
-                "ftrace_test_p6nop:"
-                P6_NOP5
-                "jmp 1f\n"
-                "ftrace_test_nop5:"
-                ".byte 0x66,0x66,0x66,0x66,0x90\n"
-                "1:"
-                ".section .fixup, \"ax\"\n"
-                "2:     movl $1, %0\n"
-                "       jmp ftrace_test_nop5\n"
-                "3:     movl $2, %0\n"
-                "       jmp 1b\n"
-                ".previous\n"
-                _ASM_EXTABLE(ftrace_test_p6nop, 2b)
-                _ASM_EXTABLE(ftrace_test_nop5, 3b)
-                : "=r"(faulted) : "0" (faulted));
-
-        switch (faulted) {
-        case 0:
-                pr_info("converting mcount calls to 0f 1f 44 00 00\n");
-                memcpy(ideal_nop5, ftrace_test_p6nop, IDEAL_NOP_SIZE_5);
-                break;
-        case 1:
-                pr_info("converting mcount calls to 66 66 66 66 90\n");
-                memcpy(ideal_nop5, ftrace_test_nop5, IDEAL_NOP_SIZE_5);
-                break;
-        case 2:
-                pr_info("converting mcount calls to jmp . + 5\n");
-                memcpy(ideal_nop5, ftrace_test_jmp, IDEAL_NOP_SIZE_5);
-                break;
-        }
-
+#ifdef CONFIG_X86_64
+        /* Don't use these on 32 bits due to broken virtualizers */
+        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
+                memcpy(ideal_nop5, p6_nops[5], 5);
+#endif
 }
 #endif