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>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 222507e8157b..d073d981a730 100644
--- 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;
         }