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    Subject[PATCH AUTOSEL for 4.9 053/190] ARM: 8668/1: ftrace: Fix dynamic ftrace with DEBUG_RODATA and !FRAME_POINTER
    Date
    From: Abel Vesa <abelvesa@linux.com>

    [ Upstream commit 6f05d0761af612e04572ba4d65b4c0274a88444f ]

    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@gmail.com>
    Acked-by: Rabin Vincent <rabin@rab.in>
    Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    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 3f1759411d51..414e60ed0257 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;
    --
    2.14.1
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