perf record: Add support for sampling taken branch

This patch adds a new option to enable taken branch stack
sampling, i.e., leverage the PERF_SAMPLE_BRANCH_STACK feature
of perf_events.

There is a new option to active this mode: -b.
It is possible to pass a set of filters to select the type of
branches to sample.

The following filters are available:

 - any : any type of branches
 - any_call : any function call or system call
 - any_ret : any function return or system call return
 - any_ind : any indirect branch
 - u:  only when the branch target is at the user level
 - k: only when the branch target is in the kernel
 - hv: only when the branch target is in the hypervisor

Filters can be combined by passing a comma separated list
to the option:

$ perf record -b any_call,u -e cycles:u branchy

Signed-off-by: Roberto Agostino Vitillo <ravitillo@lbl.gov>
Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: acme@redhat.com
Cc: robert.richter@amd.com
Cc: ming.m.lin@intel.com
Cc: andi@firstfloor.org
Cc: asharma@fb.com
Cc: vweaver1@eecs.utk.edu
Cc: khandual@linux.vnet.ibm.com
Cc: dsahern@gmail.com
Link: http://lkml.kernel.org/r/1328826068-11713-13-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

4 files changed, 104 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index a5766b4b0125..60bddaf0e5bd 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -152,6 +152,31 @@ an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must ha
 corresponding events, i.e., they always refer to events defined earlier on the command
 line.
 
+-b::
+--branch-stack::
+Enable taken branch stack sampling. Each sample captures a series of consecutive
+taken branches. The number of branches captured with each sample depends on the
+underlying hardware, the type of branches of interest, and the executed code.
+It is possible to select the types of branches captured by enabling filters. The
+following filters are defined:
+
+        -  any :  any type of branches
+        - any_call: any function call or system call
+        - any_ret: any function return or system call return
+        - any_ind: any indirect branch
+        - u:  only when the branch target is at the user level
+        - k: only when the branch target is in the kernel
+        - hv: only when the target is at the hypervisor level
+
++
+At least one of any, any_call, any_ret, any_ind must be provided. The privilege levels may
+be ommitted, in which case, the privilege levels of the associated event are applied to the
+branch filter. Both kernel (k) and hypervisor (hv) privilege levels are subject to
+permissions.  When sampling on multiple events, branch stack sampling is enabled for all
+the sampling events. The sampled branch type is the same for all events.
+Note that taken branch sampling may not be available on all processors.
+The various filters must be specified as a comma separated list: -b any_ret,u,k
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1]
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 75d230fef202..1c49d4e8767c 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -638,6 +638,77 @@ out_delete_session:
         return err;
 }
 
+#define BRANCH_OPT(n, m) \
+        { .name = n, .mode = (m) }
+
+#define BRANCH_END { .name = NULL }
+
+struct branch_mode {
+        const char *name;
+        int mode;
+};
+
+static const struct branch_mode branch_modes[] = {
+        BRANCH_OPT("u", PERF_SAMPLE_BRANCH_USER),
+        BRANCH_OPT("k", PERF_SAMPLE_BRANCH_KERNEL),
+        BRANCH_OPT("hv", PERF_SAMPLE_BRANCH_HV),
+        BRANCH_OPT("any", PERF_SAMPLE_BRANCH_ANY),
+        BRANCH_OPT("any_call", PERF_SAMPLE_BRANCH_ANY_CALL),
+        BRANCH_OPT("any_ret", PERF_SAMPLE_BRANCH_ANY_RETURN),
+        BRANCH_OPT("ind_call", PERF_SAMPLE_BRANCH_IND_CALL),
+        BRANCH_END
+};
+
+static int
+parse_branch_stack(const struct option *opt, const char *str, int unset __used)
+{
+#define ONLY_PLM \
+        (PERF_SAMPLE_BRANCH_USER        |\
+         PERF_SAMPLE_BRANCH_KERNEL      |\
+         PERF_SAMPLE_BRANCH_HV)
+
+        uint64_t *mode = (uint64_t *)opt->value;
+        const struct branch_mode *br;
+        char *s, *os, *p;
+        int ret = -1;
+
+        *mode = 0;
+
+        /* because str is read-only */
+        s = os = strdup(str);
+        if (!s)
+                return -1;
+
+        for (;;) {
+                p = strchr(s, ',');
+                if (p)
+                        *p = '\0';
+
+                for (br = branch_modes; br->name; br++) {
+                        if (!strcasecmp(s, br->name))
+                                break;
+                }
+                if (!br->name)
+                        goto error;
+
+                *mode |= br->mode;
+
+                if (!p)
+                        break;
+
+                s = p + 1;
+        }
+        ret = 0;
+
+        if ((*mode & ~ONLY_PLM) == 0) {
+                error("need at least one branch type with -b\n");
+                ret = -1;
+        }
+error:
+        free(os);
+        return ret;
+}
+
 static const char * const record_usage[] = {
         "perf record [<options>] [<command>]",
         "perf record [<options>] -- <command> [<options>]",
@@ -727,6 +798,9 @@ const struct option record_options[] = {
                      "monitor event in cgroup name only",
                      parse_cgroups),
         OPT_STRING('u', "uid", &record.uid_str, "user", "user to profile"),
+        OPT_CALLBACK('b', "branch-stack", &record.opts.branch_stack,
+                     "branch mode mask", "branch stack sampling modes",
+                     parse_branch_stack),
         OPT_END()
 };
 
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index 358f40135c4d..eec392e48067 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -222,6 +222,7 @@ struct perf_record_opts {
         unsigned int freq;
         unsigned int mmap_pages;
         unsigned int user_freq;
+        int          branch_stack;
         u64          default_interval;
         u64          user_interval;
         const char   *cpu_list;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index a1fd1cd2a5af..f421f7cbc0d3 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -126,6 +126,10 @@ void perf_evsel__config(struct perf_evsel *evsel, struct perf_record_opts *opts)
                 attr->watermark = 0;
                 attr->wakeup_events = 1;
         }
+        if (opts->branch_stack) {
+                attr->sample_type       |= PERF_SAMPLE_BRANCH_STACK;
+                attr->branch_sample_type = opts->branch_stack;
+        }
 
         attr->mmap = track;
         attr->comm = track;