From: Anders Kaseorg <andersk@MIT.EDU>
Date: Fri, 10 Oct 2008 02:19:08 +0000 (-0400)
Subject: ftrace: make ftrace_test_p6nop disassembler-friendly
X-Git-Tag: firefly_0821_release~17186^2~7
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=8b27386a9ce9c7f0f8702cff7565a46802ad57d1;p=firefly-linux-kernel-4.4.55.git

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 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;
 	}