On Mon, Aug 12, 2019 at 10:23:21AM +0300, Adrian Hunter wrote:
> 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@xxxxxxxxxx>
> >>> ---
> >>> 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.
You are right, thanks for suggestion. Will use perf_env__arch() in
next spin.
Thanks,
Leo Yan
>
> > + machine->kernel_start -= ARM_PRE_START_SIZE;
> > }
> > return err;
> > }
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