[PATCH 1/2] perf: Sample additional clock value

[Adrian Hunter <adrian.hunter@intel.com>]

Add PERF_SAMPLE_CLOCK to sample some other clock.
The patch allows for 16 possible clock selections
with the only initial possibility an architecture-specific
clock which will be used for TSC on x86.

Although there are only 16 possible clock selections,
it is envisioned that POSIX clock ids would be a
single selection, with the actual clock id provided
in another perf_event_attr member.

Based-on-patch-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 include/linux/perf_event.h      |  3 ++-
 include/uapi/linux/perf_event.h | 19 +++++++++++++++++--
 kernel/events/core.c            | 30 ++++++++++++++++++++++++++++++
 kernel/events/internal.h        |  4 ++++
 4 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index efe2d2d..e86637e 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -655,7 +655,7 @@ extern void perf_pmu_migrate_context(struct pmu *pmu,
 				int src_cpu, int dst_cpu);
 extern u64 perf_event_read_value(struct perf_event *event,
 				 u64 *enabled, u64 *running);
-
+u64 perf_sample_clock_arch(void);
 
 struct perf_sample_data {
 	/*
@@ -687,6 +687,7 @@ struct perf_sample_data {
 		u32	cpu;
 		u32	reserved;
 	}				cpu_entry;
+	u64				clock;
 	struct perf_callchain_entry	*callchain;
 
 	/*
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index be9ff06..4d081d5 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -139,8 +139,9 @@ enum perf_event_sample_format {
 	PERF_SAMPLE_IDENTIFIER			= 1U << 16,
 	PERF_SAMPLE_TRANSACTION			= 1U << 17,
 	PERF_SAMPLE_REGS_INTR			= 1U << 18,
+	PERF_SAMPLE_CLOCK			= 1U << 19,
 
-	PERF_SAMPLE_MAX = 1U << 19,		/* non-ABI */
+	PERF_SAMPLE_MAX = 1U << 20,		/* non-ABI */
 };
 
 /*
@@ -228,6 +229,16 @@ enum {
 };
 
 /*
+ * Values to determine clock to sample.
+ */
+enum perf_sample_clock_type {
+	/* Architecture-specific clock (TSC on x86) */
+	PERF_SAMPLE_CLOCK_ARCH        = 0,
+
+	PERF_SAMPLE_CLOCK_MAX               /* non-ABI */
+};
+
+/*
  * The format of the data returned by read() on a perf event fd,
  * as specified by attr.read_format:
  *
@@ -328,7 +339,9 @@ struct perf_event_attr {
 				exclude_callchain_user   : 1, /* exclude user callchains */
 				mmap2          :  1, /* include mmap with inode data     */
 				comm_exec      :  1, /* flag comm events that are due to an exec */
-				__reserved_1   : 39;
+				/* clock: see enum perf_sample_clock_type */
+				clock          :  4, /* which clock */
+				__reserved_1   : 35;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
@@ -601,6 +614,7 @@ enum perf_event_type {
 	 * 	{ u64			id;       } && PERF_SAMPLE_ID
 	 * 	{ u64			stream_id;} && PERF_SAMPLE_STREAM_ID
 	 * 	{ u32			cpu, res; } && PERF_SAMPLE_CPU
+	 *	{ u64			clock;    } && PERF_SAMPLE_CLOCK
 	 *	{ u64			id;	  } && PERF_SAMPLE_IDENTIFIER
 	 * } && perf_event_attr::sample_id_all
 	 *
@@ -746,6 +760,7 @@ enum perf_event_type {
 	 *	{ u64			transaction; } && PERF_SAMPLE_TRANSACTION
 	 *	{ u64			abi; # enum perf_sample_regs_abi
 	 *	  u64			regs[weight(mask)]; } && PERF_SAMPLE_REGS_INTR
+	 *	{ u64			clock;    } && PERF_SAMPLE_CLOCK
 	 * };
 	 */
 	PERF_RECORD_SAMPLE			= 9,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 799f034..0f6e7c8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1323,6 +1323,9 @@ static void perf_event__id_header_size(struct perf_event *event)
 	if (sample_type & PERF_SAMPLE_CPU)
 		size += sizeof(data->cpu_entry);
 
+	if (sample_type & PERF_SAMPLE_CLOCK)
+		size += sizeof(data->clock);
+
 	event->id_header_size = size;
 }
 
@@ -4915,6 +4918,11 @@ perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size,
 	}
 }
 
+u64 __weak perf_sample_clock_arch(void)
+{
+	return 0;
+}
+
 static void __perf_event_header__init_id(struct perf_event_header *header,
 					 struct perf_sample_data *data,
 					 struct perf_event *event)
@@ -4943,6 +4951,16 @@ static void __perf_event_header__init_id(struct perf_event_header *header,
 		data->cpu_entry.cpu	 = raw_smp_processor_id();
 		data->cpu_entry.reserved = 0;
 	}
+
+	if (sample_type & PERF_SAMPLE_CLOCK) {
+		switch (event->attr.clock) {
+		case PERF_SAMPLE_CLOCK_ARCH:
+			data->clock = perf_sample_clock_arch();
+			break;
+		default:
+			data->clock = 0;
+		}
+	}
 }
 
 void perf_event_header__init_id(struct perf_event_header *header,
@@ -4973,6 +4991,9 @@ static void __perf_event__output_id_sample(struct perf_output_handle *handle,
 	if (sample_type & PERF_SAMPLE_CPU)
 		perf_output_put(handle, data->cpu_entry);
 
+	if (sample_type & PERF_SAMPLE_CLOCK)
+		perf_output_put(handle, data->clock);
+
 	if (sample_type & PERF_SAMPLE_IDENTIFIER)
 		perf_output_put(handle, data->id);
 }
@@ -5218,6 +5239,9 @@ void perf_output_sample(struct perf_output_handle *handle,
 		}
 	}
 
+	if (sample_type & PERF_SAMPLE_CLOCK)
+		perf_output_put(handle, data->clock);
+
 	if (!event->attr.watermark) {
 		int wakeup_events = event->attr.wakeup_events;
 
@@ -7632,6 +7656,12 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
 
 	if (attr->sample_type & PERF_SAMPLE_REGS_INTR)
 		ret = perf_reg_validate(attr->sample_regs_intr);
+
+	if ((attr->sample_type & PERF_SAMPLE_CLOCK) &&
+	    (attr->clock >= PERF_SAMPLE_CLOCK_MAX ||
+	     (!HAVE_PERF_SAMPLE_CLOCK_ARCH &&
+	      attr->clock == PERF_SAMPLE_CLOCK_ARCH)))
+		return -EINVAL;
 out:
 	return ret;
 
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 9f6ce9b..c3dca1e 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -228,4 +228,8 @@ static inline bool arch_perf_have_user_stack_dump(void)
 #define perf_user_stack_pointer(regs) 0
 #endif /* CONFIG_HAVE_PERF_USER_STACK_DUMP */
 
+#ifndef HAVE_PERF_SAMPLE_CLOCK_ARCH
+#define HAVE_PERF_SAMPLE_CLOCK_ARCH 0
+#endif
+
 #endif /* _KERNEL_EVENTS_INTERNAL_H */
-- 
1.9.1