On Wed, May 15, 2013 at 03:37:22PM +0200, Stephane Eranian wrote:
> On Fri, May 3, 2013 at 2:11 PM, Peter Zijlstra <a.p.zijls...@chello.nl> wrote:
> > We should always have proper privileges when requesting kernel data.
> >
> > Cc: Andi Kleen <a...@linux.intel.com>
> > Cc: eran...@google.com
> > Signed-off-by: Peter Zijlstra <a.p.zijls...@chello.nl>
> > Link: http://lkml.kernel.org/n/tip-v0x9ky3ahzr6nm3c6ilwr...@git.kernel.org
> > ---
> > arch/x86/kernel/cpu/perf_event_intel_lbr.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
> > +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
> > @@ -318,8 +318,11 @@ static void intel_pmu_setup_sw_lbr_filte
> > if (br_type & PERF_SAMPLE_BRANCH_USER)
> > mask |= X86_BR_USER;
> >
> > - if (br_type & PERF_SAMPLE_BRANCH_KERNEL)
> > + if (br_type & PERF_SAMPLE_BRANCH_KERNEL) {
> > + if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
> > + return -EACCES;
> > mask |= X86_BR_KERNEL;
> > + }
> >
> This will prevent regular users from capturing kernel -> kernel branches.
> But it won't prevent users from getting kernel -> user branches. Thus
> some kernel address will still be captured. I guess they could be eliminated
> by the sw_filter.
>
> When using LBR priv level filtering, the filter applies to the branch target
> only.
How about something like the below? It also adds the branch flags Mikey wanted
for PowerPC.
---
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 12 +++++++++---
include/linux/perf_event.h | 10 +++++++---
2 files changed, 16 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index d978353..f44d635 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -585,17 +585,23 @@ intel_pmu_lbr_filter(struct cpu_hw_events *cpuc)
/* if type does not correspond, then discard */
if (type == X86_BR_NONE || (br_sel & type) != type) {
- cpuc->lbr_entries[i].from = 0;
+ cpuc->lbr_entries[i].__delete = 1;
compress = true;
}
+
+ /* hide kernel addresses if we're not privileged */
+ if (!(br_sel & X86_BR_KERNEL) && kernel_ip(from)) {
+ cpuc->lbr_entries[i].from = -1L;
+ cpuc->lbr_entries[i].invalid_from = 1;
+ }
}
if (!compress)
return;
- /* remove all entries with from=0 */
+ /* remove all entries with __delete */
for (i = 0; i < cpuc->lbr_stack.nr; ) {
- if (!cpuc->lbr_entries[i].from) {
+ if (cpuc->lbr_entries[i].__delete) {
j = i;
while (++j < cpuc->lbr_stack.nr)
cpuc->lbr_entries[j-1] = cpuc->lbr_entries[j];
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f463a46..7acf1c9 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -77,9 +77,13 @@ struct perf_raw_record {
struct perf_branch_entry {
__u64 from;
__u64 to;
- __u64 mispred:1, /* target mispredicted */
- predicted:1,/* target predicted */
- reserved:62;
+ __u64 mispred:1, /* target mispredicted */
+ predicted:1, /* target predicted */
+ invalid_to:1, /* @to isn't to be trusted */
+ invalid_from:1, /* @from isn't to be trusted */
+ reserved:59,
+ __delete:1; /* Implementation; userspace should
+ always see a 0 */
};
/*
--
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