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Date: Mon, 7 Jul 2014 15:42:08 +0200 From: Jean Pihet <jean.pihet@...aro.org> To: Will Deacon <will.deacon@....com> Cc: "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>, Sneha Priya <sneha.cse@...mail.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>, Arnaldo Carvalho de Melo <acme@...radead.org> Subject: Re: [PATCH 3/3] ARM: perf: allow tracing with kernel tracepoints events Will, On 3 July 2014 19:54, Will Deacon <will.deacon@....com> wrote: > On Fri, Jun 27, 2014 at 03:57:47PM +0100, Jean Pihet wrote: >> When tracing with tracepoints events the IP and CPSR are set to 0, >> preventing the perf code to resolve the symbols: >> >> ./perf record -e kmem:kmalloc cal >> [ perf record: Woken up 1 times to write data ] >> [ perf record: Captured and wrote 0.007 MB perf.data (~321 samples) ] >> >> ./perf report >> Overhead Command Shared Object Symbol >> ........ ....... ............. ........... >> 40.78% cal [unknown] [.]00000000 >> 31.6% cal [unknown] [.]00000000 >> >> The examination of the gathered samples (perf report -D) shows the IP >> is set to 0 and that the samples are considered as user space samples, >> while the IP should be set from the registers and the samples should be >> considered as kernel samples. >> >> The fix is to implement perf_arch_fetch_caller_regs for ARM, which >> fills the necessary registers used for the callchain unwinding and >> to determine the user/kernel space property of the samples: ip, sp, fp >> and cpsr. >> >> Tested with perf record and tracepoints triggering (-e <tracepoint>), with >> unwinding using fp (--call-graph fp) and dwarf info (--call-graph dwarf). >> >> Reported by Sneha Priya on linaro-dev, cf. >> http://lists.linaro.org/pipermail/linaro-dev/2014-May/017151.html >> >> Signed-off-by: Jean Pihet <jean.pihet@...aro.org> >> Cc: Will Deacon <will.deacon@....com> >> Reported-by: Sneha Priya <sneha.cse@...mail.com> >> --- >> arch/arm/include/asm/perf_event.h | 19 +++++++++++++++++++ >> 1 file changed, 19 insertions(+) >> >> diff --git a/arch/arm/include/asm/perf_event.h b/arch/arm/include/asm/perf_event.h >> index 7558775..b02b5d3 100644 >> --- a/arch/arm/include/asm/perf_event.h >> +++ b/arch/arm/include/asm/perf_event.h >> @@ -26,6 +26,25 @@ struct pt_regs; >> extern unsigned long perf_instruction_pointer(struct pt_regs *regs); >> extern unsigned long perf_misc_flags(struct pt_regs *regs); >> #define perf_misc_flags(regs) perf_misc_flags(regs) >> + >> +/* >> + * Take a snapshot of the regs. >> + * We only need a few of the regs: >> + * - ip for PERF_SAMPLE_IP, >> + * - sp & fp for fp & dwarf based callchain unwinding, >> + * - cpsr for user_mode() tests. >> + */ >> +#define perf_arch_fetch_caller_regs(regs, __ip) { \ >> + instruction_pointer(regs)= (__ip); \ >> + __asm__ ( \ >> + "str sp, %[_ARM_sp] \n\t" \ >> + "str fp, %[_ARM_fp] \n\t" \ >> + "mrs %[_ARM_cpsr], cpsr \n\t" \ >> + : [_ARM_sp] "=m" (regs->ARM_sp), \ >> + [_ARM_fp] "=m" (regs->ARM_fp), \ >> + [_ARM_cpsr] "=r" (regs->ARM_cpsr) \ >> + ); \ >> +} > > You don't appear to have addressed my comments from last time. What changed? A new patch set it on its way, with the commit description and the comments in the code updated. Jean > > Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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