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-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 5ceeca382820..5079f24c955a 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

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