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Commit 8b27386a authored by Anders Kaseorg's avatar Anders Kaseorg Committed by Ingo Molnar
Browse files

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: default avatarAnders Kaseorg <andersk@mit.edu>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent bfadadfc

arch/x86/kernel/ftrace.c

+4 −2
Original line number Diff line number Diff line
@@ -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;

	}