Skip to contentSkip to conversation

Patch "perf/x86: Fix RDPMC vs. mm_struct tracking" has been added to the 4.12-stable tree

PATCH [email protected] 1 participant 1 message Aug 20, 2017

Subsystems (3)
Stable branch x86 perf events
lore
Share & tools
lore

[email protected]

author maintainer Applied
#0 lore raw

This is a note to let you know that I've just added the patch titled

perf/x86: Fix RDPMC vs. mm_struct tracking

to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-x86-fix-rdpmc-vs.-mm_struct-tracking.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From bfe334924ccd9f4a53f30240c03cf2f43f5b2df1 Mon Sep 17 00:00:00 2001

From: Peter Zijlstra <[email protected]>
Date: Wed, 2 Aug 2017 19:39:30 +0200
Subject: perf/x86: Fix RDPMC vs. mm_struct tracking

From: Peter Zijlstra <[email protected]>

commit bfe334924ccd9f4a53f30240c03cf2f43f5b2df1 upstream.

Vince reported the following rdpmc() testcase failure:

Quoted 8 lines

Failing test case:

	fd=perf_event_open();
	addr=mmap(fd);
	exec()  // without closing or unmapping the event
	fd=perf_event_open();
	addr=mmap(fd);
	rdpmc()	// GPFs due to rdpmc being disabled

The problem is of course that exec() plays tricks with what is current->mm, only destroying the old mappings after having installed the new mm.

Fix this confusion by passing along vma->vm_mm instead of relying on current->mm.

Reported-by Vince Weaver <[email protected]>
Tested-by Vince Weaver <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Reviewed-by Andy Lutomirski <[email protected]>
Cc Arnaldo Carvalho de Melo <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Stephane Eranian <[email protected]>
Cc Thomas Gleixner <[email protected]>
Fixes 1e0fb9ec679c ("perf: Add pmu callbacks to track event mapping and unmapping")
Link http://lkml.kernel.org/r/[email protected] open here
[ Minor cleanups. ]
Signed-off-by Ingo Molnar <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 arch/x86/events/core.c     |   16 +++++++---------
 include/linux/perf_event.h |    4 ++--
 kernel/events/core.c       |    6 +++---
 3 files changed, 12 insertions(+), 14 deletions(-)
arch/x86/events/core.c +7 -9
@@ -2105,7 +2105,7 @@ static void refresh_pce(void *ignored)
 		load_mm_cr4(current->active_mm);
 }
 
-static void x86_pmu_event_mapped(struct perf_event *event)
+static void x86_pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)
 {
 	if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED))
 		return;

@@ -2120,22 +2120,20 @@ static void x86_pmu_event_mapped(struct
 	 * For now, this can't happen because all callers hold mmap_sem
 	 * for write.  If this changes, we'll need a different solution.
 	 */
-	lockdep_assert_held_exclusive(&current->mm->mmap_sem);
+	lockdep_assert_held_exclusive(&mm->mmap_sem);
 
-	if (atomic_inc_return(&current->mm->context.perf_rdpmc_allowed) == 1)
-		on_each_cpu_mask(mm_cpumask(current->mm), refresh_pce, NULL, 1);
+	if (atomic_inc_return(&mm->context.perf_rdpmc_allowed) == 1)
+		on_each_cpu_mask(mm_cpumask(mm), refresh_pce, NULL, 1);
 }
 
-static void x86_pmu_event_unmapped(struct perf_event *event)
+static void x86_pmu_event_unmapped(struct perf_event *event, struct mm_struct *mm)
 {
-	if (!current->mm)
-		return;
 
 	if (!(event->hw.flags & PERF_X86_EVENT_RDPMC_ALLOWED))
 		return;
 
-	if (atomic_dec_and_test(&current->mm->context.perf_rdpmc_allowed))
-		on_each_cpu_mask(mm_cpumask(current->mm), refresh_pce, NULL, 1);
+	if (atomic_dec_and_test(&mm->context.perf_rdpmc_allowed))
+		on_each_cpu_mask(mm_cpumask(mm), refresh_pce, NULL, 1);
 }
 
 static int x86_pmu_event_idx(struct perf_event *event)
include/linux/perf_event.h +2 -2
@@ -310,8 +310,8 @@ struct pmu {
 	 * Notification that the event was mapped or unmapped.  Called
 	 * in the context of the mapping task.
 	 */
-	void (*event_mapped)		(struct perf_event *event); /*optional*/
-	void (*event_unmapped)		(struct perf_event *event); /*optional*/
+	void (*event_mapped)		(struct perf_event *event, struct mm_struct *mm); /* optional */
+	void (*event_unmapped)		(struct perf_event *event, struct mm_struct *mm); /* optional */
 
 	/*
 	 * Flags for ->add()/->del()/ ->start()/->stop(). There are
kernel/events/core.c +3 -3
@@ -5084,7 +5084,7 @@ static void perf_mmap_open(struct vm_are
 		atomic_inc(&event->rb->aux_mmap_count);
 
 	if (event->pmu->event_mapped)
-		event->pmu->event_mapped(event);
+		event->pmu->event_mapped(event, vma->vm_mm);
 }
 
 static void perf_pmu_output_stop(struct perf_event *event);

@@ -5107,7 +5107,7 @@ static void perf_mmap_close(struct vm_ar
 	unsigned long size = perf_data_size(rb);
 
 	if (event->pmu->event_unmapped)
-		event->pmu->event_unmapped(event);
+		event->pmu->event_unmapped(event, vma->vm_mm);
 
 	/*
 	 * rb->aux_mmap_count will always drop before rb->mmap_count and

@@ -5405,7 +5405,7 @@ aux_unlock:
 	vma->vm_ops = &perf_mmap_vmops;
 
 	if (event->pmu->event_mapped)
-		event->pmu->event_mapped(event);
+		event->pmu->event_mapped(event, vma->vm_mm);
 
 	return ret;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/x86-asm-64-clear-ac-on-nmi-entries.patch queue-4.12/kernel-watchdog-prevent-false-positives-with-turbo-modes.patch queue-4.12/perf-x86-fix-rdpmc-vs.-mm_struct-tracking.patch