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 222507e..d073d98 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -132,7 +132,9 @@
".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 @@
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;
}