[PATCH v2 2/7] ARM: Introduce arm_get_current_stack_frame()
Will Deacon
will.deacon at arm.com
Fri May 30 10:20:54 PDT 2014
On Fri, May 30, 2014 at 05:59:46PM +0100, Nikolay Borisov wrote:
> From: Nikolay Borisov <Nikolay.Borisov at arm.com>
>
> Currently there are numerous places where "struct pt_regs" are used to
> populate "struct stackframe", however all of those location do not
> consider the situation where the kernel might be compiled in THUMB2
> mode, in which case the framepointer member of pt_regs become ARM_r7
> instead of ARM_fp (r11). Document this idiosyncracy in the
> definition of "struct stackframe"
>
> The easiest solution is to introduce a new function (in the spirit of
> https://groups.google.com/forum/#!topic/linux.kernel/dA2YuUcSpZ4)
> which would hide the complexity of initializing the stackframe struct
> from pt_regs.
>
> Also implement a macro frame_pointer(regs) that would return the correct
> register so that we can use it in cases where we just require the frame
> pointer and not a whole struct stackframe
>
> Signed-off-by: Nikolay Borisov <Nikolay.Borisov at arm.com>
> ---
> arch/arm/include/asm/ptrace.h | 6 ++++++
> arch/arm/include/asm/stacktrace.h | 12 ++++++++++++
> 2 files changed, 18 insertions(+)
>
> diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
> index c877654..601264d 100644
> --- a/arch/arm/include/asm/ptrace.h
> +++ b/arch/arm/include/asm/ptrace.h
> @@ -84,6 +84,12 @@ static inline long regs_return_value(struct pt_regs *regs)
>
> #define instruction_pointer(regs) (regs)->ARM_pc
>
> +#ifdef CONFIG_THUMB2_KERNEL
> +#define frame_pointer(regs) (regs)->ARM_r7
> +#else
> +#define frame_pointer(regs) (regs)->ARM_fp
> +#endif
> +
> static inline void instruction_pointer_set(struct pt_regs *regs,
> unsigned long val)
> {
> diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
> index 4d0a164..6a5b13e 100644
> --- a/arch/arm/include/asm/stacktrace.h
> +++ b/arch/arm/include/asm/stacktrace.h
> @@ -2,12 +2,24 @@
> #define __ASM_STACKTRACE_H
>
> struct stackframe {
> + /* FP member should hold R7 when CONFIG_THUMB2_KERNEL is enabled.
> + * and R11 otherwise
> + */
Very minor nit: please reformat the comment like:
/*
* FP member should hold R7 when CONFIG_THUMB2_KERNEL is enabled
* and R11 otherwise.
*/
for consistency with the rest of the kernel (I also moved the full-stop to
the end of the sentence).
With that:
Acked-by: Will Deacon <will.deacon at arm.com>
Will
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