From 6b099d9b040b0f3d0aec05b560d7caf879af5077 Mon Sep 17 00:00:00 2001 From: Alexander Shishkin Date: Thu, 11 Jun 2015 15:13:56 +0300 Subject: [PATCH] perf/x86/intel/bts: Fix DS area sharing with x86_pmu events Currently, the intel_bts driver relies on the DS area allocated by the x86_pmu code in its event_init() path, which is a bug: creating a BTS event while no x86_pmu events are present results in a NULL pointer dereference. The same DS area is also used by PEBS sampling, which makes it quite a bit trickier to have a separate one for intel_bts' purposes. This patch makes intel_bts driver use the same DS allocation and reference counting code as x86_pmu to make sure it is always present when either intel_bts or x86_pmu need it. Signed-off-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: acme@infradead.org Cc: adrian.hunter@intel.com Link: http://lkml.kernel.org/r/1434024837-9916-2-git-send-email-alexander.shishkin@linux.intel.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event.c | 52 ++++++++++++++-------- arch/x86/kernel/cpu/perf_event.h | 4 ++ arch/x86/kernel/cpu/perf_event_intel_bts.c | 9 ++++ 3 files changed, 46 insertions(+), 19 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index 4f7001f28936..aa4e3a74e541 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -270,11 +270,7 @@ static bool check_hw_exists(void) static void hw_perf_event_destroy(struct perf_event *event) { - if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) { - release_pmc_hardware(); - release_ds_buffers(); - mutex_unlock(&pmc_reserve_mutex); - } + x86_release_hardware(); } void hw_perf_lbr_event_destroy(struct perf_event *event) @@ -324,6 +320,35 @@ set_ext_hw_attr(struct hw_perf_event *hwc, struct perf_event *event) return x86_pmu_extra_regs(val, event); } +int x86_reserve_hardware(void) +{ + int err = 0; + + if (!atomic_inc_not_zero(&active_events)) { + mutex_lock(&pmc_reserve_mutex); + if (atomic_read(&active_events) == 0) { + if (!reserve_pmc_hardware()) + err = -EBUSY; + else + reserve_ds_buffers(); + } + if (!err) + atomic_inc(&active_events); + mutex_unlock(&pmc_reserve_mutex); + } + + return err; +} + +void x86_release_hardware(void) +{ + if (atomic_dec_and_mutex_lock(&active_events, &pmc_reserve_mutex)) { + release_pmc_hardware(); + release_ds_buffers(); + mutex_unlock(&pmc_reserve_mutex); + } +} + /* * Check if we can create event of a certain type (that no conflicting events * are present). @@ -336,9 +361,10 @@ int x86_add_exclusive(unsigned int what) return 0; mutex_lock(&pmc_reserve_mutex); - for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++) + for (i = 0; i < ARRAY_SIZE(x86_pmu.lbr_exclusive); i++) { if (i != what && atomic_read(&x86_pmu.lbr_exclusive[i])) goto out; + } atomic_inc(&x86_pmu.lbr_exclusive[what]); ret = 0; @@ -527,19 +553,7 @@ static int __x86_pmu_event_init(struct perf_event *event) if (!x86_pmu_initialized()) return -ENODEV; - err = 0; - if (!atomic_inc_not_zero(&active_events)) { - mutex_lock(&pmc_reserve_mutex); - if (atomic_read(&active_events) == 0) { - if (!reserve_pmc_hardware()) - err = -EBUSY; - else - reserve_ds_buffers(); - } - if (!err) - atomic_inc(&active_events); - mutex_unlock(&pmc_reserve_mutex); - } + err = x86_reserve_hardware(); if (err) return err; diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h index ef78516850fb..f068695eaca0 100644 --- a/arch/x86/kernel/cpu/perf_event.h +++ b/arch/x86/kernel/cpu/perf_event.h @@ -703,6 +703,10 @@ int x86_add_exclusive(unsigned int what); void x86_del_exclusive(unsigned int what); +int x86_reserve_hardware(void); + +void x86_release_hardware(void); + void hw_perf_lbr_event_destroy(struct perf_event *event); int x86_setup_perfctr(struct perf_event *event); diff --git a/arch/x86/kernel/cpu/perf_event_intel_bts.c b/arch/x86/kernel/cpu/perf_event_intel_bts.c index ac1f0c55f379..7795f3f8b1d5 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_bts.c +++ b/arch/x86/kernel/cpu/perf_event_intel_bts.c @@ -483,17 +483,26 @@ static int bts_event_add(struct perf_event *event, int mode) static void bts_event_destroy(struct perf_event *event) { + x86_release_hardware(); x86_del_exclusive(x86_lbr_exclusive_bts); } static int bts_event_init(struct perf_event *event) { + int ret; + if (event->attr.type != bts_pmu.type) return -ENOENT; if (x86_add_exclusive(x86_lbr_exclusive_bts)) return -EBUSY; + ret = x86_reserve_hardware(); + if (ret) { + x86_del_exclusive(x86_lbr_exclusive_bts); + return ret; + } + event->destroy = bts_event_destroy; return 0; -- GitLab