linux-kernel - [PATCH 3.16 098/127] sparc64: Fix pcr_ops initialization and usage bugs.

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Message-Id: <20141028033425.127052005@linuxfoundation.org>
Date:	Tue, 28 Oct 2014 11:35:33 +0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Christopher Alexander Tobias Schulze 
	<cat.schulze@...ce-dsl.net>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 098/127] sparc64: Fix pcr_ops initialization and usage bugs.

3.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "David S. Miller" <davem@...emloft.net>

[ Upstream commit 8bccf5b313180faefce38e0d1140f76e0f327d28 ]

Christopher reports that perf_event_print_debug() can crash in uniprocessor
builds.  The crash is due to pcr_ops being NULL.

This happens because pcr_arch_init() is only invoked by smp_cpus_done() which
only executes in SMP builds.

init_hw_perf_events() is closely intertwined with pcr_ops being setup properly,
therefore:

1) Call pcr_arch_init() early on from init_hw_perf_events(), instead of
   from smp_cpus_done().

2) Do not hook up a PMU type if pcr_ops is NULL after pcr_arch_init().

3) Move init_hw_perf_events to a later initcall so that it we will be
   sure to invoke pcr_arch_init() after all cpus are brought up.

Finally, guard the one naked sequence of pcr_ops dereferences in
__global_pmu_self() with an appropriate NULL check.

Reported-by: Christopher Alexander Tobias Schulze <cat.schulze@...ce-dsl.net>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/sparc/kernel/perf_event.c |    7 +++++--
 arch/sparc/kernel/process_64.c |    3 +++
 arch/sparc/kernel/smp_64.c     |    1 -
 3 files changed, 8 insertions(+), 3 deletions(-)

--- a/arch/sparc/kernel/perf_event.c
+++ b/arch/sparc/kernel/perf_event.c
@@ -1671,9 +1671,12 @@ static bool __init supported_pmu(void)
 
 static int __init init_hw_perf_events(void)
 {
+	int err;
+
 	pr_info("Performance events: ");
 
-	if (!supported_pmu()) {
+	err = pcr_arch_init();
+	if (err || !supported_pmu()) {
 		pr_cont("No support for PMU type '%s'\n", sparc_pmu_type);
 		return 0;
 	}
@@ -1685,7 +1688,7 @@ static int __init init_hw_perf_events(vo
 
 	return 0;
 }
-early_initcall(init_hw_perf_events);
+pure_initcall(init_hw_perf_events);
 
 void perf_callchain_kernel(struct perf_callchain_entry *entry,
 			   struct pt_regs *regs)
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -312,6 +312,9 @@ static void __global_pmu_self(int this_c
 	struct global_pmu_snapshot *pp;
 	int i, num;
 
+	if (!pcr_ops)
+		return;
+
 	pp = &global_cpu_snapshot[this_cpu].pmu;
 
 	num = 1;
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -1383,7 +1383,6 @@ void __cpu_die(unsigned int cpu)
 
 void __init smp_cpus_done(unsigned int max_cpus)
 {
-	pcr_arch_init();
 }
 
 void smp_send_reschedule(int cpu)


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