linux-kernel - [PATCH v1 11/11] x86: perf: intel_bts: Add core dump related functionality

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Date:	Thu,  6 Feb 2014 12:50:34 +0200
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH v1 11/11] x86: perf: intel_bts: Add core dump related functionality

BTS data can be used in process core dumps. This patch implements itrace
core dump related hooks that will configure and output BTS traces into
a core file.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
 arch/x86/kernel/cpu/perf_event_intel_bts.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_bts.c b/arch/x86/kernel/cpu/perf_event_intel_bts.c
index 0a08969..20a19b2 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_bts.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_bts.c
@@ -436,6 +436,26 @@ static void bts_event_read(struct perf_event *event)
 {
 }
 
+static size_t bts_trace_core_size(struct perf_event *event)
+{
+	return 0;
+}
+
+static void bts_trace_core_output(struct coredump_params *cprm,
+				  struct perf_event *event,
+				  unsigned long len)
+{
+	struct bts_buffer *buf = itrace_event_get_priv(event);
+	u64 head = local64_read(&buf->head);
+
+	if (head < len) {
+		dump_emit(cprm, buf->buf + head, buf->real_size - head);
+		dump_emit(cprm, buf->buf, len - buf->real_size + head);
+	} else
+		dump_emit(cprm, buf->buf + head - len, len);
+	itrace_event_put(event);
+}
+
 static __init int bts_init(void)
 {
 	int ret, cpu;
@@ -459,6 +479,8 @@ static __init int bts_init(void)
 	bts_pmu.pmu.read		= bts_event_read;
 	bts_pmu.alloc_buffer		= bts_buffer_itrace_alloc;
 	bts_pmu.free_buffer		= bts_buffer_itrace_free;
+	bts_pmu.core_size		= bts_trace_core_size;
+	bts_pmu.core_output		= bts_trace_core_output;
 	bts_pmu.name			= "intel_bts";
 
 	ret = itrace_pmu_register(&bts_pmu);
-- 
1.8.5.2

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