s390/perf: add callback to perf to enable using AUX buffer

Perf tool need implement a callback to enable using AUX buffer. Perf
will do another mmap() to trigger the setup of AUX buffer in kernel
if there is such callback. The default size of the AUX buffer is set
properly according to the sampling frequency to avoid overflow. It
could also be manually set by -m option of perf.

The interface of perf is not changed. Diagnostic mode sampling
could be started by `perf record -e rBD000` like before.
Signed-off-by: Pu Hou <bjhoupu@linux.vnet.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

tools/perf/arch/s390/util/Build

@@ -4,3 +4,5 @@ libperf-y += kvm-stat.o
 libperf-$(CONFIG_DWARF) += dwarf-regs.o
 
 libperf-y += machine.o
+
+libperf-$(CONFIG_AUXTRACE) += auxtrace.o

tools/perf/arch/s390/util/auxtrace.c

+#include <stdbool.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/bitops.h>
+#include <linux/log2.h>
+
+#include "../../util/evlist.h"
+#include "../../util/auxtrace.h"
+#include "../../util/evsel.h"
+
+#define PERF_EVENT_CPUM_SF		0xB0000 /* Event: Basic-sampling */
+#define PERF_EVENT_CPUM_SF_DIAG		0xBD000 /* Event: Combined-sampling */
+#define DEFAULT_AUX_PAGES		128
+#define DEFAULT_FREQ			4000
+
+static void cpumsf_free(struct auxtrace_record *itr)
+{
+	free(itr);
+}
+
+static size_t cpumsf_info_priv_size(struct auxtrace_record *itr __maybe_unused,
+				    struct perf_evlist *evlist __maybe_unused)
+{
+	return 0;
+}
+
+static int
+cpumsf_info_fill(struct auxtrace_record *itr __maybe_unused,
+		 struct perf_session *session __maybe_unused,
+		 struct auxtrace_info_event *auxtrace_info __maybe_unused,
+		 size_t priv_size __maybe_unused)
+{
+	return 0;
+}
+
+static unsigned long
+cpumsf_reference(struct auxtrace_record *itr __maybe_unused)
+{
+	return 0;
+}
+
+static int
+cpumsf_recording_options(struct auxtrace_record *ar __maybe_unused,
+			 struct perf_evlist *evlist __maybe_unused,
+			 struct record_opts *opts)
+{
+	unsigned int factor = 1;
+	unsigned int pages;
+
+	opts->full_auxtrace = true;
+
+	/*
+	 * The AUX buffer size should be set properly to avoid
+	 * overflow of samples if it is not set explicitly.
+	 * DEFAULT_AUX_PAGES is an proper size when sampling frequency
+	 * is DEFAULT_FREQ. It is expected to hold about 1/2 second
+	 * of sampling data. The size used for AUX buffer will scale
+	 * according to the specified frequency and DEFAULT_FREQ.
+	 */
+	if (!opts->auxtrace_mmap_pages) {
+		if (opts->user_freq != UINT_MAX)
+			factor = (opts->user_freq + DEFAULT_FREQ
+				  - 1) / DEFAULT_FREQ;
+		pages = DEFAULT_AUX_PAGES * factor;
+		opts->auxtrace_mmap_pages = roundup_pow_of_two(pages);
+	}
+
+	return 0;
+}
+
+static int
+cpumsf_parse_snapshot_options(struct auxtrace_record *itr __maybe_unused,
+			      struct record_opts *opts __maybe_unused,
+			      const char *str __maybe_unused)
+{
+	return 0;
+}
+
+/*
+ * auxtrace_record__init is called when perf record
+ * check if the event really need auxtrace
+ */
+struct auxtrace_record *auxtrace_record__init(struct perf_evlist *evlist,
+					      int *err)
+{
+	struct auxtrace_record *aux;
+	struct perf_evsel *pos;
+	int diagnose = 0;
+
+	if (evlist->nr_entries == 0)
+		return NULL;
+
+	evlist__for_each_entry(evlist, pos) {
+		if (pos->attr.config == PERF_EVENT_CPUM_SF_DIAG) {
+			diagnose = 1;
+			break;
+		}
+	}
+
+	if (!diagnose)
+		return NULL;
+
+	/* sampling in diagnose mode. alloc aux buffer */
+	aux = zalloc(sizeof(*aux));
+	if (aux == NULL) {
+		*err = -ENOMEM;
+		return NULL;
+	}
+
+	aux->parse_snapshot_options = cpumsf_parse_snapshot_options;
+	aux->recording_options = cpumsf_recording_options;
+	aux->info_priv_size = cpumsf_info_priv_size;
+	aux->info_fill = cpumsf_info_fill;
+	aux->free = cpumsf_free;
+	aux->reference = cpumsf_reference;
+
+	return aux;
+}