[PATCH v2 5/6] perf/x86/intel/pt: Use extended error reporting in event initialization

Alexander Shishkin
2015-08-24T14:35:50Z

Event attribute validation is one of the biggest sources of EINVALs around
perf_event_open() syscall. This patch annotates error checks with extended
error reporting macros to provide the user with more details on what they
are doing wrong.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
arch/x86/kernel/cpu/perf_event_intel_pt.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c
index 4216928344..9a09c89928 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_pt.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c
@@ -18,6 +18,8 @@

#undef DEBUG

+#define PERF_MODNAME "perf/x86/intel/pt"
+
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
@@ -198,29 +200,29 @@ fail:
RTIT_CTL_CYC_PSB | \
RTIT_CTL_MTC)

-static bool pt_event_valid(struct perf_event *event)
+static int pt_event_valid(struct perf_event *event)
{
u64 config = event->attr.config;
u64 allowed, requested;

if ((config & PT_CONFIG_MASK) != config)
- return false;
+ return perf_err(-EINVAL, "PT config: disallowed bits");

if (config & RTIT_CTL_CYC_PSB) {
if (!pt_cap_get(PT_CAP_psb_cyc))
- return false;
+ return perf_err(-EINVAL, "PT config: PSB/CYC not supported");

allowed = pt_cap_get(PT_CAP_psb_periods);
requested = (config & RTIT_CTL_PSB_FREQ) >>
RTIT_CTL_PSB_FREQ_OFFSET;
if (requested && (!(allowed & BIT(requested))))
- return false;
+ return perf_err(-EINVAL, "PT config: unsupported PSB period");

allowed = pt_cap_get(PT_CAP_cycle_thresholds);
requested = (config & RTIT_CTL_CYC_THRESH) >>
RTIT_CTL_CYC_THRESH_OFFSET;
if (requested && (!(allowed & BIT(requested))))
- return false;
+ return perf_err(-EINVAL, "PT config: unsupported CYC threshold");
}

if (config & RTIT_CTL_MTC) {
@@ -232,20 +234,20 @@ static bool pt_event_valid(struct perf_event *event)
* CPUID is 0 will #GP, so better safe than sorry.
*/
if (!pt_cap_get(PT_CAP_mtc))
- return false;
+ return perf_err(-EINVAL, "PT config: MTC not supported");

allowed = pt_cap_get(PT_CAP_mtc_periods);
if (!allowed)
- return false;
+ return perf_err(-EINVAL, "PT config: MTC periods not supported");

requested = (config & RTIT_CTL_MTC_RANGE) >>
RTIT_CTL_MTC_RANGE_OFFSET;

if (!(allowed & BIT(requested)))
- return false;
+ return perf_err(-EINVAL, "PT config: unsupported MTC period");
}

- return true;
+ return 0;
}

/*
@@ -1111,14 +1113,17 @@ static void pt_event_destroy(struct perf_event *event)

static int pt_event_init(struct perf_event *event)
{
+ int err;
+
if (event->attr.type != pt_pmu.pmu.type)
return -ENOENT;

- if (!pt_event_valid(event))
- return -EINVAL;
+ err = pt_event_valid(event);
+ if (err)
+ return err;

if (x86_add_exclusive(x86_lbr_exclusive_pt))
- return -EBUSY;
+ return perf_err(-EBUSY, "PT conflicts with active events");

event->destroy = pt_event_destroy;

--
2.5.0