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

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Mon, 24 Jun 2019 16:00:09 -0300

Em Thu, Jun 20, 2019 at 08:58:29AM +0800, Leo Yan escreveu:
> Hi Mathieu,
> 
> On Wed, Jun 19, 2019 at 11:49:44AM -0600, Mathieu Poirier wrote:
> 
> [...]
> 
> > > diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> > > index 51dd00f65709..4776c2c1fb6d 100644
> > > --- a/tools/perf/Makefile.config
> > > +++ b/tools/perf/Makefile.config
> > > @@ -418,6 +418,30 @@ ifdef CORESIGHT
> > >      endif
> > >      LDFLAGS += $(LIBOPENCSD_LDFLAGS)
> > >      EXTLIBS += $(OPENCSDLIBS)
> > > +    ifneq ($(wildcard $(srctree)/arch/arm64/kernel/vmlinux.lds),)
> > > +      # Extract info from lds:
> > > +      #  . = ((((((((0xffffffffffffffff)) - (((1)) << (48)) + 1) + (0)) + (0x08000000))) + (0x08000000))) + 0x00080000;
> > > +      # ARM64_PRE_START_SIZE := (0x08000000 + 0x08000000 + 0x00080000)
> > > +      ARM64_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)
> > > +    else
> > > +      ARM64_PRE_START_SIZE := 0
> > > +    endif
> > > +    CFLAGS += -DARM64_PRE_START_SIZE="$(ARM64_PRE_START_SIZE)"
> > > +    ifneq ($(wildcard $(srctree)/arch/arm/kernel/vmlinux.lds),)
> > > +      # 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)
> > > +    else
> > > +      ARM_PRE_START_SIZE := 0
> > > +    endif
> > > +    CFLAGS += -DARM_PRE_START_SIZE="$(ARM_PRE_START_SIZE)"
> > >      $(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..ae831f836c70 100644
> > > --- a/tools/perf/util/cs-etm.c
> > > +++ b/tools/perf/util/cs-etm.c
> > > @@ -613,10 +613,34 @@ 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;
> > > +       const char *arch;
> > >
> > >         machine = etmq->etm->machine;
> > > +       arch = perf_env__arch(machine->env);
> > >
> > > -       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.
> > > +        */
> > > +       if (!strcmp(arch, "arm64"))
> > > +               fixup_kernel_start = etmq->etm->kernel_start -
> > > +                                    ARM64_PRE_START_SIZE;
> > > +       else if (!strcmp(arch, "arm"))
> > > +               fixup_kernel_start = etmq->etm->kernel_start -
> > > +                                    ARM_PRE_START_SIZE;
> > 
> > I will test your work but from a quick look wouldn't it be better to
> > have a single define name here?  From looking at the modifications you
> > did to Makefile.config there doesn't seem to be a reason to have two.
> 
> Thanks for suggestion.  I changed to use single define
> ARM_PRE_START_SIZE and sent patch v2 [1].
> 
> If possible, please test patch v2.
> 
> Thanks,
> Leo Yan

So just for the record, I'm waiting for Mathieu on this one, i.e. for
him to test/ack v3.

- Arnaldo
 
> [1] https://lore.kernel.org/linux-arm-kernel/[email-masked]/T/#u
> 
> > > +
> > > +       if (address >= fixup_kernel_start) {
> > >                 if (machine__is_host(machine))
> > >                         return PERF_RECORD_MISC_KERNEL;
> > >                 else
> > > --
> > > 2.17.1
> > >

-- 

- Arnaldo