Messages in this thread | | | Date | Tue, 21 May 2013 15:55:14 +0200 | Subject | Re: [PATCH 3/3] perf, x86, lbr: Demand proper privileges for PERF_SAMPLE_BRANCH_KERNEL | From | Stephane Eranian <> |
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On Thu, May 16, 2013 at 12:15 PM, Michael Neuling <mikey@neuling.org> wrote: > Peter Zijlstra <peterz@infradead.org> wrote: > >> 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.zijlstra@chello.nl> wrote: >> > > We should always have proper privileges when requesting kernel data. >> > > >> > > Cc: Andi Kleen <ak@linux.intel.com> >> > > Cc: eranian@google.com >> > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> >> > > Link: http://lkml.kernel.org/n/tip-v0x9ky3ahzr6nm3c6ilwrili@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. > > Peter, > > BTW PowerPC also has the ability to filter on conditional branches. Any > chance we could add something like the follow to perf also? > > Mikey > > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h > index fb104e5..891c769 100644 > --- a/include/uapi/linux/perf_event.h > +++ b/include/uapi/linux/perf_event.h > @@ -157,8 +157,9 @@ enum perf_branch_sample_type { > PERF_SAMPLE_BRANCH_ANY_CALL = 1U << 4, /* any call branch */ > PERF_SAMPLE_BRANCH_ANY_RETURN = 1U << 5, /* any return branch */ > PERF_SAMPLE_BRANCH_IND_CALL = 1U << 6, /* indirect calls */ > + PERF_SAMPLE_BRANCH_CONDITIONAL = 1U << 7, /* conditional branches */ > I would use PERF_SAMPLE_BRANCH_COND here.
> - PERF_SAMPLE_BRANCH_MAX = 1U << 7, /* non-ABI */ > + PERF_SAMPLE_BRANCH_MAX = 1U << 8, /* non-ABI */ > }; > > #define PERF_SAMPLE_BRANCH_PLM_ALL \ > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > index cdf58ec..5b0b89d 100644 > --- a/tools/perf/builtin-record.c > +++ b/tools/perf/builtin-record.c > @@ -676,6 +676,7 @@ static const struct branch_mode branch_modes[] = { > BRANCH_OPT("any_call", PERF_SAMPLE_BRANCH_ANY_CALL), > BRANCH_OPT("any_ret", PERF_SAMPLE_BRANCH_ANY_RETURN), > BRANCH_OPT("ind_call", PERF_SAMPLE_BRANCH_IND_CALL), > + BRANCH_OPT("cnd", PERF_SAMPLE_BRANCH_CONDITIONAL),
use "cond"
> BRANCH_END > }; >
And if you do this, you also need to update the x86 perf_event_intel_lbr.c mapping tables to fill out the entries for PERF_SAMPLE_BRANCH_COND:
[PERF_SAMPLE_BRANCH_COND] = LBR_JCC,
And you also need to update intel_pmu_setup_sw_lbr_filter() to handle the conversion to x86 instructions:
if (br_type & PERF_SAMPLE_BRANCH_COND) mask |= X86_BR_JCC;
You also need to update the perf-record.txt documentation to list cond as a possible branch filter.
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