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SubjectRe: [PATCH v1 3/5] mips function graph tracer support

On Fri, 29 May 2009, wuzhangjin@gmail.com wrote:
> diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
> index ce8a0ba..bd58f16 100644
> --- a/arch/mips/kernel/mcount.S
> +++ b/arch/mips/kernel/mcount.S
> @@ -28,6 +28,10 @@
> PTR_SUBU sp, PT_SIZE
> PTR_S ra, PT_R31(sp)
> PTR_S $1, PT_R1(sp)
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> + PTR_S v0, PT_R2(sp)
> + PTR_S v1, PT_R3(sp)
> +#endif
> PTR_S a0, PT_R4(sp)
> PTR_S a1, PT_R5(sp)
> PTR_S a2, PT_R6(sp)
> @@ -43,6 +47,10 @@
> .macro MCOUNT_RESTORE_REGS
> PTR_L ra, PT_R31(sp)
> PTR_L $1, PT_R1(sp)
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> + PTR_L v0, PT_R2(sp)
> + PTR_L v1, PT_R3(sp)
> +#endif
> PTR_L a0, PT_R4(sp)
> PTR_L a1, PT_R5(sp)
> PTR_L a2, PT_R6(sp)
> @@ -89,6 +97,14 @@ ftrace_call:
> nop
>
> MCOUNT_RESTORE_REGS
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> + .globl ftrace_graph_call
> +ftrace_graph_call:
> + j ftrace_stub
> + nop
> +#endif
> +
> .globl ftrace_stub
> ftrace_stub:
> RETURN_BACK
> @@ -106,7 +122,15 @@ NESTED(_mcount, PT_SIZE, ra)
> PTR_L t1, ftrace_trace_function /* please don't use t1 later, safe? */
> bne t0, t1, static_trace
> nop
> -
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> + PTR_L t2, ftrace_graph_return
> + bne t0, t2, ftrace_graph_caller
> + nop
> + PTR_LA t0, ftrace_graph_entry_stub
> + PTR_L t2, ftrace_graph_entry
> + bne t0, t2, ftrace_graph_caller
> + nop
> +#endif
> j ftrace_stub
> nop
>
> @@ -125,5 +149,37 @@ ftrace_stub:
>
> #endif /* ! CONFIG_DYNAMIC_FTRACE */
>
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +
> +NESTED(ftrace_graph_caller, PT_SIZE, ra)
> + MCOUNT_SAVE_REGS
> +
> + MCOUNT_SET_ARGS
> + jal prepare_ftrace_return
> + nop
> +
> + /* overwrite the parent as &return_to_handler: v0 -> $1(at) */
> + PTR_S v0, PT_R1(sp)
> +
> + MCOUNT_RESTORE_REGS
> + RETURN_BACK
> + END(ftrace_graph_caller)
> +
> + .align 2
> + .globl return_to_handler
> +return_to_handler:
> + MCOUNT_SAVE_REGS

I'm not sure which version of function_graph tracer you looked at, but I'm
pretty sure you can just save the return code registers of the function.

return_to_handler is called on the return of a function. Thus, any callee
saved registers have already been restored and would also be restored by
ftrace_return_to_handler. Any callee registers would have been saved by
the function you are about to return to.

Thus the only things you need to save are the return code registers.

-- Steve


> +
> + jal ftrace_return_to_handler
> + nop
> +
> + /* restore the real parent address: v0 -> ra */
> + PTR_S v0, PT_R31(sp)
> +
> + MCOUNT_RESTORE_REGS
> + RETURN_BACK
> +
> +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> +
> .set at
> .set reorder
> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
> index 58738c8..67435e5 100644
> --- a/arch/mips/kernel/vmlinux.lds.S
> +++ b/arch/mips/kernel/vmlinux.lds.S
> @@ -36,6 +36,7 @@ SECTIONS
> SCHED_TEXT
> LOCK_TEXT
> KPROBES_TEXT
> + IRQENTRY_TEXT
> *(.text.*)
> *(.fixup)
> *(.gnu.warning)
> --
> 1.6.0.4
>
>


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