* [RESEND] arm: ftrace: fix dynamic ftrace with DEBUG_RODATA and !FRAME_POINTER
@ 2017-03-26 15:55 Abel Vesa
2017-03-30 20:06 ` Kees Cook
0 siblings, 1 reply; 2+ messages in thread
From: Abel Vesa @ 2017-03-26 15:55 UTC (permalink / raw)
To: linux-arm-kernel
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: 80d6b0c2eed2a ("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@linux.com>
Acked-by: Rabin Vincent <rabin@rab.in>
---
arch/arm/kernel/ftrace.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 3f17594..414e60e 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -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;
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [RESEND] arm: ftrace: fix dynamic ftrace with DEBUG_RODATA and !FRAME_POINTER
2017-03-26 15:55 [RESEND] arm: ftrace: fix dynamic ftrace with DEBUG_RODATA and !FRAME_POINTER Abel Vesa
@ 2017-03-30 20:06 ` Kees Cook
0 siblings, 0 replies; 2+ messages in thread
From: Kees Cook @ 2017-03-30 20:06 UTC (permalink / raw)
To: linux-arm-kernel
On Sun, Mar 26, 2017 at 8:55 AM, Abel Vesa <abelvesa@linux.com> wrote:
> 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: 80d6b0c2eed2a ("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@linux.com>
> Acked-by: Rabin Vincent <rabin@rab.in>
This looks fine to me. I'd send it to the ARM patch tracker since
you've gotten an Ack:
http://www.arm.linux.org.uk/developer/patches/info.php
-Kees
> ---
> arch/arm/kernel/ftrace.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
> index 3f17594..414e60e 100644
> --- a/arch/arm/kernel/ftrace.c
> +++ b/arch/arm/kernel/ftrace.c
> @@ -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;
> --
> 2.7.4
>
--
Kees Cook
Pixel Security
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