On Tue, Dec 06, 2016 at 05:06:04PM +0000, Abel Vesa wrote:
> This adds __ftrace_regs_caller which, unlike __ftrace_caller,
> adds register saving/restoring and livepatch handling if
> the pc register gets modified by klp_ftrace_handler.
>
> Signed-off-by: Abel Vesa <abelv...@linux.com>
> ---
> arch/arm/kernel/entry-ftrace.S | 49
> ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 49 insertions(+)
>
> diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
> index c73c403..b6ada5c 100644
> --- a/arch/arm/kernel/entry-ftrace.S
> +++ b/arch/arm/kernel/entry-ftrace.S
> @@ -92,6 +92,46 @@
> 2: mcount_exit
> .endm
>
> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> +
> +.macro __ftrace_regs_caller suffix
> +
> + stmdb sp!, {r0-r15}
> + mov r3, sp
> +
> + ldr r10, [sp, #60]
> +
> + mcount_get_lr r1 @ lr of instrumented func
> + mcount_adjust_addr r0, lr @ instrumented function
> +
> + .globl ftrace_regs_call\suffix
> +ftrace_regs_call\suffix:
> + bl ftrace_stub
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> + .globl ftrace_regs_graph_call\suffix
> +ftrace_regs_graph_call\suffix:
> + mov r0, r0
> +#endif
> +#ifdef CONFIG_LIVEPATCH
> + ldr r0, [sp, #60]
> + cmp r0, r10
> + beq ftrace_regs_caller_end
> + ldmia sp!, {r0-r12}
> + add sp, sp, #8
> + ldmia sp!, {r11}
> + sub sp, r12, #16
> + str r11, [sp, #12]
> + ldmia sp!, {r11, r12, lr, pc}
Some comments about the above stack manipulation (in the code) would be
useful - remember, the contents of your cover letter is lost when the
patches are applied.
However, I'm not convinced yet that this doesn't unbalance the stack,
unless the livepatching code pushes some extra registers onto it,
particularly with the following unstacking code after the livepatch
code.
--
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