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[PATCH] perf: fix hypervisor branch sampling permission check
From: Stephane Eranian <eranian () google com>
Date: Thu, 6 Jun 2013 11:02:04 +0200


Commit 2b923c8 perf/x86: Check branch sampling priv level in generic code
was missing the check for the hypervisor (HV) priv level, so add it back.

With this patch, we get the following correct behavior:

  # echo 2 >/proc/sys/kernel/perf_event_paranoid 

  $ perf record -j any,k noploop 1
  Error:
  You may not have permission to collect stats.
  Consider tweaking /proc/sys/kernel/perf_event_paranoid:
   -1 - Not paranoid at all
    0 - Disallow raw tracepoint access for unpriv
    1 - Disallow cpu events for unpriv
    2 - Disallow kernel profiling for unpriv

   $ perf record -j any,hv noploop 1
   Error:
   You may not have permission to collect stats.
   Consider tweaking /proc/sys/kernel/perf_event_paranoid:
    -1 - Not paranoid at all
     0 - Disallow raw tracepoint access for unpriv
     1 - Disallow cpu events for unpriv
     2 - Disallow kernel profiling for unpriv

Signed-off-by: Stephane Eranian <eranian () google com>
---
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 95edd5a..f0880fb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6501,8 +6501,8 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
                         */
                        attr->branch_sample_type = mask;
                }
-               /* kernel level capture: check permissions */
-               if ((mask & PERF_SAMPLE_BRANCH_KERNEL)
+               /* privileged levels capture (kernel, hv): check permissions */
+               if ((mask & PERF_SAMPLE_BRANCH_PERM_PLM)
                    && perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
                        return -EACCES;
        }


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