Commit 6f05d076 authored Apr 03, 2017 by Abel Vesa Committed by Russell King Apr 20, 2017

ARM: 8668/1: ftrace: Fix dynamic ftrace with DEBUG_RODATA and !FRAME_POINTER



The support for dynamic ftrace with CONFIG_DEBUG_RODATA involves
overriding the weak arch_ftrace_update_code() with a variant which makes
the kernel text writable around the patching.

This override was however added under the CONFIG_OLD_MCOUNT ifdef, and
CONFIG_OLD_MCOUNT is only enabled if frame pointers are enabled.

This leads to non-functional dynamic ftrace (ftrace triggers a
WARN_ON()) when CONFIG_DEBUG_RODATA is enabled and CONFIG_FRAME_POINTER
is not.

Move the override out of that ifdef and into the CONFIG_DYNAMIC_FTRACE
ifdef where it belongs.

Fixes: 80d6b0c2 ("ARM: mm: allow text and rodata sections to be read-only")
Suggested-by: Nicolai Stange <nicstange@gmail.com>
Suggested-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Abel Vesa <abelvesa@gmail.com>
Acked-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

parent b089c31c

arch/arm/kernel/ftrace.c

+6 −5

Original line number	Diff line number	Diff line
		@@ -29,11 +29,6 @@
		#endif

		#ifdef CONFIG_DYNAMIC_FTRACE
		#ifdef CONFIG_OLD_MCOUNT
		#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
		#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)

		#define OLD_NOP 0xe1a00000 /* mov r0, r0 */

		static int __ftrace_modify_code(void *data)
		{
		@@ -51,6 +46,12 @@ void arch_ftrace_update_code(int command)
		stop_machine(__ftrace_modify_code, &command, NULL);
		}

		#ifdef CONFIG_OLD_MCOUNT
		#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
		#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)

		#define OLD_NOP 0xe1a00000 /* mov r0, r0 */

		static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
		{
		return rec->arch.old_mcount ? OLD_NOP : NOP;