netdev - Re: [PATCH v2] perf cs-etm: Improve completeness for kernel address space

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Date:   Thu, 20 Jun 2019 11:51:46 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>, coresight@...ts.linaro.org
Subject: Re: [PATCH v2] perf cs-etm: Improve completeness for kernel address
 space

Hi all,

On Thu, Jun 20, 2019 at 08:54:28AM +0800, Leo Yan wrote:

[...]

> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 51dd00f65709..cf5906d667aa 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -418,6 +418,26 @@ ifdef CORESIGHT
>      endif
>      LDFLAGS += $(LIBOPENCSD_LDFLAGS)
>      EXTLIBS += $(OPENCSDLIBS)
> +    ARM_PRE_START_SIZE := 0
> +    ifeq ($(SRCARCH),arm64)
> +      # Extract info from lds:
> +      #  . = ((((((((0xffffffffffffffff)) - (((1)) << (48)) + 1) + (0)) + (0x08000000))) + (0x08000000))) + 0x00080000;
> +      # ARM_PRE_START_SIZE := (0x08000000 + 0x08000000 + 0x00080000)
> +      ARM_PRE_START_SIZE := $(shell egrep ' \. \= \({8}0x[0-9a-fA-F]+\){2}' \
> +        $(srctree)/arch/arm64/kernel/vmlinux.lds | \
> +        sed -e 's/[(|)|.|=|+|<|;|-]//g' -e 's/ \+/ /g' -e 's/^[ \t]*//' | \
> +        awk -F' ' '{print "("$$6 "+"  $$7 "+" $$8")"}' 2>/dev/null)
> +    endif
> +    ifeq ($(SRCARCH),arm)
> +      # Extract info from lds:
> +      #   . = ((0xC0000000)) + 0x00208000;
> +      # ARM_PRE_START_SIZE := 0x00208000
> +      ARM_PRE_START_SIZE := $(shell egrep ' \. \= \({2}0x[0-9a-fA-F]+\){2}' \
> +        $(srctree)/arch/arm/kernel/vmlinux.lds | \
> +        sed -e 's/[(|)|.|=|+|<|;|-]//g' -e 's/ \+/ /g' -e 's/^[ \t]*//' | \
> +        awk -F' ' '{print "("$$2")"}' 2>/dev/null)
> +    endif
> +    CFLAGS += -DARM_PRE_START_SIZE="$(ARM_PRE_START_SIZE)"

I did testing for building perf with this patch, this patch is fragile
and easily introduce the building warning:

  <command-line>: error: "ARM_PRE_START_SIZE" redefined [-Werror]
  <command-line>: note: this is the location of the previous definition

To dismiss this error, I need to change the macro define as below:

  +    CFLAGS += -DARM_PRE_START_SIZE=$(ARM_PRE_START_SIZE)

So I sent patch v3 to address this issue and please directly reivew
patch v3.  Sorry for spamming.

Thanks,
Leo Yan


>      $(call detected,CONFIG_LIBOPENCSD)
>      ifdef CSTRACE_RAW
>        CFLAGS += -DCS_DEBUG_RAW
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 0c7776b51045..5fa0be3a3904 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -613,10 +613,27 @@ static void cs_etm__free(struct perf_session *session)
>  static u8 cs_etm__cpu_mode(struct cs_etm_queue *etmq, u64 address)
>  {
>  	struct machine *machine;
> +	u64 fixup_kernel_start = 0;
>  
>  	machine = etmq->etm->machine;
>  
> -	if (address >= etmq->etm->kernel_start) {
> +	/*
> +	 * Since arm and arm64 specify some memory regions prior to
> +	 * 'kernel_start', kernel addresses can be less than 'kernel_start'.
> +	 *
> +	 * For arm architecture, the 16MB virtual memory space prior to
> +	 * 'kernel_start' is allocated to device modules, a PMD table if
> +	 * CONFIG_HIGHMEM is enabled and a PGD table.
> +	 *
> +	 * For arm64 architecture, the root PGD table, device module memory
> +	 * region and BPF jit region are prior to 'kernel_start'.
> +	 *
> +	 * To reflect the complete kernel address space, compensate these
> +	 * pre-defined regions for kernel start address.
> +	 */
> +	fixup_kernel_start = etmq->etm->kernel_start - ARM_PRE_START_SIZE;
> +
> +	if (address >= fixup_kernel_start) {
>  		if (machine__is_host(machine))
>  			return PERF_RECORD_MISC_KERNEL;
>  		else
> -- 
> 2.17.1
>