linux/arch/powerpc/perf
Anton Blanchard 72e349f112 powerpc/perf: Fix book3s kernel to userspace backtraces
When we take a PMU exception or a software event we call
perf_read_regs(). This overloads regs->result with a boolean that
describes if we should use the sampled instruction address register
(SIAR) or the regs.

If the exception is in kernel, we start with the kernel regs and
backtrace through the kernel stack. At this point we switch to the
userspace regs and backtrace the user stack with perf_callchain_user().

Unfortunately these regs have not got the perf_read_regs() treatment,
so regs->result could be anything. If it is non zero,
perf_instruction_pointer() decides to use the SIAR, and we get issues
like this:

0.11%  qemu-system-ppc  [kernel.kallsyms]        [k] _raw_spin_lock_irqsave
       |
       ---_raw_spin_lock_irqsave
          |
          |--52.35%-- 0
          |          |
          |          |--46.39%-- __hrtimer_start_range_ns
          |          |          kvmppc_run_core
          |          |          kvmppc_vcpu_run_hv
          |          |          kvmppc_vcpu_run
          |          |          kvm_arch_vcpu_ioctl_run
          |          |          kvm_vcpu_ioctl
          |          |          do_vfs_ioctl
          |          |          sys_ioctl
          |          |          system_call
          |          |          |
          |          |          |--67.08%-- _raw_spin_lock_irqsave <--- hi mum
          |          |          |          |
          |          |          |           --100.00%-- 0x7e714
          |          |          |                     0x7e714

Notice the bogus _raw_spin_irqsave when we transition from kernel
(system_call) to userspace (0x7e714). We inserted what was in the SIAR.

Add a check in regs_use_siar() to check that the regs in question
are from a PMU exception. With this fix the backtrace makes sense:

     0.47%  qemu-system-ppc  [kernel.vmlinux]         [k] _raw_spin_lock_irqsave
            |
            ---_raw_spin_lock_irqsave
               |
               |--53.83%-- 0
               |          |
               |          |--44.73%-- hrtimer_try_to_cancel
               |          |          kvmppc_start_thread
               |          |          kvmppc_run_core
               |          |          kvmppc_vcpu_run_hv
               |          |          kvmppc_vcpu_run
               |          |          kvm_arch_vcpu_ioctl_run
               |          |          kvm_vcpu_ioctl
               |          |          do_vfs_ioctl
               |          |          sys_ioctl
               |          |          system_call
               |          |          __ioctl
               |          |          0x7e714
               |          |          0x7e714

Cc: stable@vger.kernel.org
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2015-06-02 13:26:38 +10:00
..
req-gen powerpc/perf/{hv-gpci, hv-common}: generate requests with counters annotated 2015-02-02 17:56:39 +11:00
Makefile powerpc/perf: Add kconfig option for hypervisor provided counters 2014-03-24 09:48:32 +11:00
bhrb.S powerpc/perf: Add basic assembly code to read BHRB entries on POWER8 2013-04-26 16:11:11 +10:00
callchain.c powerpc/mm/thp: Make page table walk safe against thp split/collapse 2015-04-17 11:23:39 +10:00
core-book3s.c powerpc/perf: Fix book3s kernel to userspace backtraces 2015-06-02 13:26:38 +10:00
core-fsl-emb.c perf/powerpc: reset event hw state when adding it to the PMU 2015-01-29 23:44:18 -06:00
e500-pmu.c powerpc/perf: Add stalled-cycles events 2013-01-10 17:00:56 +11:00
e6500-pmu.c powerpc/perf: Add e6500 PMU driver 2013-08-07 18:38:04 -05:00
hv-24x7-catalog.h powerpc/perf/hv-24x7: parse catalog and populate sysfs with events 2015-02-02 17:56:38 +11:00
hv-24x7-domains.h powerpc/perf/hv-24x7: parse catalog and populate sysfs with events 2015-02-02 17:56:38 +11:00
hv-24x7.c powerpc updates for 4.1 2015-04-16 13:53:32 -05:00
hv-24x7.h powerpc/perf/hv-24x7: Modify definition of request and result buffers 2015-04-11 20:49:21 +10:00
hv-common.c powerpc/perf/{hv-gpci, hv-common}: generate requests with counters annotated 2015-02-02 17:56:39 +11:00
hv-common.h perf: define EVENT_DEFINE_RANGE_FORMAT_LITE helper 2015-02-02 17:56:38 +11:00
hv-gpci-requests.h powerpc/perf/hv-gpci: add the remaining gpci requests 2015-02-02 17:56:39 +11:00
hv-gpci.c powerpc/perf/{hv-gpci, hv-common}: generate requests with counters annotated 2015-02-02 17:56:39 +11:00
hv-gpci.h powerpc/perf/{hv-gpci, hv-common}: generate requests with counters annotated 2015-02-02 17:56:39 +11:00
mpc7450-pmu.c powerpc/perf: Pass the struct perf_events down to compute_mmcr() 2014-07-28 14:30:47 +10:00
power4-pmu.c powerpc/perf: Pass the struct perf_events down to compute_mmcr() 2014-07-28 14:30:47 +10:00
power5+-pmu.c powerpc/perf: Pass the struct perf_events down to compute_mmcr() 2014-07-28 14:30:47 +10:00
power5-pmu.c powerpc/perf: Pass the struct perf_events down to compute_mmcr() 2014-07-28 14:30:47 +10:00
power6-pmu.c powerpc/perf: Pass the struct perf_events down to compute_mmcr() 2014-07-28 14:30:47 +10:00
power7-events-list.h powerpc/perf: Make some new raw event codes available in sysfs 2014-03-24 09:48:23 +11:00
power7-pmu.c powerpc/perf: Pass the struct perf_events down to compute_mmcr() 2014-07-28 14:30:47 +10:00
power8-pmu.c powerpc/perf: Add per-event excludes on Power8 2014-07-28 14:30:58 +10:00
ppc970-pmu.c powerpc/perf: Pass the struct perf_events down to compute_mmcr() 2014-07-28 14:30:47 +10:00