ftrace: make ftrace_test_p6nop disassembler-friendly

Commit 4c3dc21b136f8cb4b72afee16c3ba7e961656c0b in tip introduced the
5-byte NOP ftrace_test_p6nop:

   jmp . + 5
   .byte 0x00, 0x00, 0x00

This is not friendly to disassemblers because an odd number of 0x00s
ends in the middle of an instruction boundary.  This changes the 0x00s
to 1-byte NOPs (0x90).

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 222507e8157be6713850b6bd178f7c35ae0103e7..d073d981a730306f970aabdf5f7174453c24d226 100644 (file)
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -132,7 +132,9 @@ int __init ftrace_dyn_arch_init(void *data)
                ".section .text, \"ax\"\n"
                "ftrace_test_jmp:"
                "jmp ftrace_test_p6nop\n"
-               ".byte 0x00,0x00,0x00\n"  /* 2 byte jmp + 3 bytes */
+               "nop\n"
+               "nop\n"
+               "nop\n"  /* 2 byte jmp + 3 bytes */
                "ftrace_test_p6nop:"
                P6_NOP5
                "jmp 1f\n"
@@ -161,7 +163,7 @@ int __init ftrace_dyn_arch_init(void *data)
                ftrace_nop = (unsigned long *)ftrace_test_nop5;
                break;
        case 2:
-               pr_info("ftrace: converting mcount calls to jmp 1f\n");
+               pr_info("ftrace: converting mcount calls to jmp . + 5\n");
                ftrace_nop = (unsigned long *)ftrace_test_jmp;
                break;
        }