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Date: Mon, 12 Aug 2019 10:23:21 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Leo Yan <leo.yan@...aro.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
David Miller <davem@...emloft.net>,
Milian Wolff <milian.wolff@...b.com>,
Donald Yandt <donald.yandt@...il.com>,
Davidlohr Bueso <dave@...olabs.net>,
Wei Li <liwei391@...wei.com>, Mark Drayton <mbd@...com>,
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@...il.com>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
bpf@...r.kernel.org, clang-built-linux@...glegroups.com,
Mathieu Poirier <mathieu.poirier@...aro.org>
Subject: Re: [PATCH v4 1/2] perf machine: Support arch's specific kernel start
address
On 12/08/19 10:02 AM, Leo Yan wrote:
> On Mon, Aug 12, 2019 at 09:37:33AM +0300, Adrian Hunter wrote:
>> On 10/08/19 10:21 AM, Leo Yan wrote:
>>> machine__get_kernel_start() gives out the kernel start address; some
>>> architectures need to tweak the start address so that can reflect the
>>> kernel start address correctly. This is not only for x86_64 arch, but
>>> it is also required by other architectures, e.g. arm/arm64 needs to
>>> tweak the kernel start address so can include the kernel memory regions
>>> which are used before the '_stext' symbol.
>>>
>>> This patch refactors machine__get_kernel_start() by adding a weak
>>> arch__fix_kernel_text_start(), any architecture can implement it to
>>> tweak its specific start address; this also allows the arch specific
>>> code to be placed into 'arch' folder.
>>>
>>> Signed-off-by: Leo Yan <leo.yan@...aro.org>
>>> ---
>>> tools/perf/arch/x86/util/machine.c | 10 ++++++++++
>>> tools/perf/util/machine.c | 13 +++++++------
>>> tools/perf/util/machine.h | 2 ++
>>> 3 files changed, 19 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/tools/perf/arch/x86/util/machine.c b/tools/perf/arch/x86/util/machine.c
>>> index 1e9ec783b9a1..9f012131534a 100644
>>> --- a/tools/perf/arch/x86/util/machine.c
>>> +++ b/tools/perf/arch/x86/util/machine.c
>>> @@ -101,4 +101,14 @@ int machine__create_extra_kernel_maps(struct machine *machine,
>>> return ret;
>>> }
>>>
>>> +void arch__fix_kernel_text_start(u64 *start)
>>> +{
>>> + /*
>>> + * On x86_64, PTI entry trampolines are less than the
>>> + * start of kernel text, but still above 2^63. So leave
>>> + * kernel_start = 1ULL << 63 for x86_64.
>>> + */
>>> + *start = 1ULL << 63;
>>> +}
>>
>> That is needed for reporting x86 data on any arch i.e. it is not specific to
>> the compile-time architecture, it is specific to the perf.data file
>> architecture, which is what machine__is() compares. So, this looks wrong.
>
> Thanks for reviewing, Adrian.
>
> If so, I think we should extend the function machine__get_kernel_start()
> as below; for building successfully, will always define the macro
> ARM_PRE_START_SIZE in Makefile.config.
>
> @Arnaldo, @Adrian, Please let me know if this works for you?
I don't know how you intend to calculate ARM_PRE_START_SIZE, but below is OK
for x86.
>
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index f6ee7fbad3e4..30a0ff627263 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -2687,13 +2687,26 @@ int machine__get_kernel_start(struct machine *machine)
> machine->kernel_start = 1ULL << 63;
> if (map) {
> err = map__load(map);
> + if (err)
> + return err;
> +
> /*
> * On x86_64, PTI entry trampolines are less than the
> * start of kernel text, but still above 2^63. So leave
> * kernel_start = 1ULL << 63 for x86_64.
> */
> - if (!err && !machine__is(machine, "x86_64"))
> + if (!machine__is(machine, "x86_64"))
> machine->kernel_start = map->start;
> +
> + /*
> + * On arm/arm64, some memory regions are prior to '_stext'
> + * symbol; to reflect the complete kernel address space,
> + * compensate these pre-defined regions for kernel start
> + * address.
> + */
> + if (machine__is(machine, "arm64") ||
> + machine__is(machine, "arm"))
machine__is() does not normalize the architecture, so you may want to use
perf_env__arch() instead.
> + machine->kernel_start -= ARM_PRE_START_SIZE;
> }
> return err;
> }
>
> Thanks,
> Leo Yan
>
>>> +
>>> #endif
>>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>>> index f6ee7fbad3e4..603518835692 100644
>>> --- a/tools/perf/util/machine.c
>>> +++ b/tools/perf/util/machine.c
>>> @@ -2671,6 +2671,10 @@ int machine__nr_cpus_avail(struct machine *machine)
>>> return machine ? perf_env__nr_cpus_avail(machine->env) : 0;
>>> }
>>>
>>> +void __weak arch__fix_kernel_text_start(u64 *start __maybe_unused)
>>> +{
>>> +}
>>> +
>>> int machine__get_kernel_start(struct machine *machine)
>>> {
>>> struct map *map = machine__kernel_map(machine);
>>> @@ -2687,14 +2691,11 @@ int machine__get_kernel_start(struct machine *machine)
>>> machine->kernel_start = 1ULL << 63;
>>> if (map) {
>>> err = map__load(map);
>>> - /*
>>> - * On x86_64, PTI entry trampolines are less than the
>>> - * start of kernel text, but still above 2^63. So leave
>>> - * kernel_start = 1ULL << 63 for x86_64.
>>> - */
>>> - if (!err && !machine__is(machine, "x86_64"))
>>> + if (!err)
>>> machine->kernel_start = map->start;
>>> }
>>> +
>>> + arch__fix_kernel_text_start(&machine->kernel_start);
>>> return err;
>>> }
>>>
>>> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
>>> index ef803f08ae12..9cb459f4bfbc 100644
>>> --- a/tools/perf/util/machine.h
>>> +++ b/tools/perf/util/machine.h
>>> @@ -278,6 +278,8 @@ void machine__get_kallsyms_filename(struct machine *machine, char *buf,
>>> int machine__create_extra_kernel_maps(struct machine *machine,
>>> struct dso *kernel);
>>>
>>> +void arch__fix_kernel_text_start(u64 *start);
>>> +
>>> /* Kernel-space maps for symbols that are outside the main kernel map and module maps */
>>> struct extra_kernel_map {
>>> u64 start;
>>>
>>
>
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