Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH v3 1/6] arm64: Add ftrace support | Date | Mon, 10 Feb 2014 16:03:21 +0100 |
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On Friday 07 February 2014, AKASHI Takahiro wrote: > @@ -0,0 +1,23 @@
> + > +#ifdef CONFIG_FUNCTION_TRACER > +#define MCOUNT_ADDR ((unsigned long)_mcount) > +#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ > + > +#ifndef __ASSEMBLY__ > +extern void _mcount(unsigned long); > +#endif /* __ASSEMBLY__ */ > +#endif /* CONFIG_FUNCTION_TRACER */
We generally like to have as few #ifdef as possible, and I think the #ifdef CONFIG_FUNCTION_TRACER here is not needed.
> +#endif /* __ASM_FTRACE_H */ > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile > index 2d4554b..ca921fb 100644 > --- a/arch/arm64/kernel/Makefile > +++ b/arch/arm64/kernel/Makefile > @@ -5,6 +5,11 @@ > CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET) > AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET) > > +ifdef CONFIG_FUNCTION_TRACER > +CFLAGS_REMOVE_ftrace.o = -pg > +CFLAGS_REMOVE_insn.o = -pg > +endif
Same here. It never hurts to have the CFLAGS_REMOVE_* statements here, since you will not want to build these files for profiling.
> diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c > index 338b568..7f0512f 100644 > --- a/arch/arm64/kernel/arm64ksyms.c > +++ b/arch/arm64/kernel/arm64ksyms.c > @@ -56,3 +56,7 @@ EXPORT_SYMBOL(clear_bit); > EXPORT_SYMBOL(test_and_clear_bit); > EXPORT_SYMBOL(change_bit); > EXPORT_SYMBOL(test_and_change_bit); > + > +#ifdef CONFIG_FUNCTION_TRACER > +EXPORT_SYMBOL(_mcount); > +#endif
This one is clearly needed of course.
> +/* > + * Gcc with -pg will put the following code in the beginning of each function: > + * mov x0, x30 > + * bl _mcount > + * [function's body ...] > + * "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic > + * ftrace is enabled.
Unrelated to your patch, I have run into problems with this on arm32, maybe someone on Cc to this mail has an idea what to do about it:
If I build a large "randconfig" kernel or "allyesconfig", the kernel image size exceeds 32MB, which means I can no longer link callers with a 26 bit signed immediate argument like the "bl _mcount" here. For any other function calls, "gcc -mlong-calls" can be used to work around this, but this particular instance is created by inserting assembly statements into the output without considering the long-call options. Is there a way to get the kernel to link anyway?
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
Here, again, you an remove the #ifdef by making the entire file built only for CONFIG_FUNCTION_GRAPH_TRACER.
Arnd
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