On 03/19/2010 02:43 PM, Ashwin Chaugule wrote:
> Is there a better way to fix this in the original ftrace_graph_caller ?
> The lr isn't pushed on the stack before "bl mcount".
>
> --
>
> From: Ashwin Chaugule <ashwinc@xxxxxxxxxxx>
>
> Newer compilers use the __gnu_mcount_nc stub in every function
> prologue. The lr of the instrumented function is pushed on the
> stack before branching to __gnu_mcount_nc. Pop it before returning
> back to instrumented function so that it can return to its parent
> from its epilogue.
>
>
> Signed-off-by: Ashwin Chaugule <ashwinc@xxxxxxxxxxx>
> ---
> arch/arm/kernel/entry-common.S | 20 ++++++++++++++++++++
> 1 files changed, 20 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
> index b8a9e47..30feac3 100644
> --- a/arch/arm/kernel/entry-common.S
> +++ b/arch/arm/kernel/entry-common.S
> @@ -144,6 +144,14 @@ ENTRY(__gnu_mcount_nc)
> adr r0, ftrace_stub
> cmp r0, r2
> bne gnu_trace
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> + ldr r1, =ftrace_graph_return
> + ldr r2, [r1]
> + cmp r0, r2 @ if *ftrace_graph_return != ftrace_stub
> + bne new_ftrace_graph_caller
> +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> +
> ldmia sp!, {r0-r3, ip, lr}
> bx ip
>
> @@ -155,6 +163,18 @@ gnu_trace:
> mov pc, r2
> ldmia sp!, {r0-r3, ip, lr}
> bx ip
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +ENTRY(new_ftrace_graph_caller) @ for use with __gnu_mcount_nc
> + sub r0, fp, #4 @ &lr of instrumented routine
> (&parent)
> + mov r1, lr @ instrumented routine (func)
> + sub r1, r1, #MCOUNT_INSN_SIZE
> + mov r2, fp @ frame pointer
> + bl prepare_ftrace_return
> + ldmia sp!, {r0-r3, ip, lr} @ need to pop lr, pushed before
> + mov pc, ip @ bl __gnu_mcount_nc
> +
> +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>
> ENTRY(mcount)
> stmdb sp!, {r0-r3, lr}
Wow, interesting timing. I just finished yesterday my own
version of this patch (for 2.6.29) - it looks amazingingly similar.
What's up with putting fp in r2 - is that required in the latest
prepare_ftrace_return()?
-- Tim
------------- patch follows ----------------
Add support to __gnu_mcount_nc, used by newer (4.x?) Gnu compilers,
for ftrace function_graph support on ARM.
Signed-off-by: Tim Bird <tim.bird@xxxxxxxxxxx>
---
arch/arm/kernel/entry-common.S | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -140,6 +140,12 @@ ENTRY(__gnu_mcount_nc)
adr r0, ftrace_stub
cmp r0, r2
bne gnu_trace
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ ldr r1, =ftrace_graph_return
+ ldr r2, [r1]
+ cmp r0, r2 @ if *ftrace_graph_return != ftrace_stub
+ bne gnu_ftrace_graph_caller
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
ldmia sp!, {r0-r3, ip, lr}
bx ip
@@ -196,6 +202,13 @@ return_to_handler:
ldmia sp!, {r0-r3}
mov pc, lr
+ENTRY(gnu_ftrace_graph_caller)
+ sub r0, fp, #4 @ &lr of instrumented routine (&parent)
+ sub r1, lr, #MCOUNT_INSN_SIZE @ instrumented routine (func)
+ bl prepare_ftrace_return
+ ldmia sp!, {r0-r3, ip, lr}
+ bx ip
+
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#endif /* CONFIG_DYNAMIC_FTRACE */
--
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