perf: Add build id data in mmap2 event

Adding support to carry build id data in mmap2 event.

The build id data replaces maj/min/ino/ino_generation
fields, which are also used to identify map's binary,
so it's ok to replace them with build id data:

  union {
          struct {
                  u32       maj;
                  u32       min;
                  u64       ino;
                  u64       ino_generation;
          };
          struct {
                  u8        build_id_size;
                  u8        __reserved_1;
                  u16       __reserved_2;
                  u8        build_id[20];
          };
  };

Replaced maj/min/ino/ino_generation fields give us size
of 24 bytes. We use 20 bytes for build id data, 1 byte
for size and rest is unused.

There's new misc bit for mmap2 to signal there's build
id data in it:

  #define PERF_RECORD_MISC_MMAP_BUILD_ID   (1 << 14)

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20210114134044.1418404-4-jolsa@kernel.org

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index b15e3447cd9fead851a8ec2e672ec581b80cbdee..cb6f841035608e9b126bffc61d4cd8624220eb27 100644 (file)
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -386,7 +386,8 @@ struct perf_event_attr {
                                aux_output     :  1, /* generate AUX records instead of events */
                                cgroup         :  1, /* include cgroup events */
                                text_poke      :  1, /* include text poke events */
-                               __reserved_1   : 30;
+                               build_id       :  1, /* use build id in mmap2 events */
+                               __reserved_1   : 29;
 
        union {
                __u32           wakeup_events;    /* wakeup every n events */
@@ -659,6 +660,22 @@ struct perf_event_mmap_page {
        __u64   aux_size;
 };
 
+/*
+ * The current state of perf_event_header::misc bits usage:
+ * ('|' used bit, '-' unused bit)
+ *
+ *  012         CDEF
+ *  |||---------||||
+ *
+ *  Where:
+ *    0-2     CPUMODE_MASK
+ *
+ *    C       PROC_MAP_PARSE_TIMEOUT
+ *    D       MMAP_DATA / COMM_EXEC / FORK_EXEC / SWITCH_OUT
+ *    E       MMAP_BUILD_ID / EXACT_IP / SCHED_OUT_PREEMPT
+ *    F       (reserved)
+ */
+
 #define PERF_RECORD_MISC_CPUMODE_MASK          (7 << 0)
 #define PERF_RECORD_MISC_CPUMODE_UNKNOWN       (0 << 0)
 #define PERF_RECORD_MISC_KERNEL                        (1 << 0)
@@ -690,6 +707,7 @@ struct perf_event_mmap_page {
  *
  *   PERF_RECORD_MISC_EXACT_IP           - PERF_RECORD_SAMPLE of precise events
  *   PERF_RECORD_MISC_SWITCH_OUT_PREEMPT - PERF_RECORD_SWITCH* events
+ *   PERF_RECORD_MISC_MMAP_BUILD_ID      - PERF_RECORD_MMAP2 event
  *
  *
  * PERF_RECORD_MISC_EXACT_IP:
@@ -699,9 +717,13 @@ struct perf_event_mmap_page {
  *
  * PERF_RECORD_MISC_SWITCH_OUT_PREEMPT:
  *   Indicates that thread was preempted in TASK_RUNNING state.
+ *
+ * PERF_RECORD_MISC_MMAP_BUILD_ID:
+ *   Indicates that mmap2 event carries build id data.
  */
 #define PERF_RECORD_MISC_EXACT_IP              (1 << 14)
 #define PERF_RECORD_MISC_SWITCH_OUT_PREEMPT    (1 << 14)
+#define PERF_RECORD_MISC_MMAP_BUILD_ID         (1 << 14)
 /*
  * Reserve the last bit to indicate some extended misc field
  */
@@ -915,10 +937,20 @@ enum perf_event_type {
         *      u64                             addr;
         *      u64                             len;
         *      u64                             pgoff;
-        *      u32                             maj;
-        *      u32                             min;
-        *      u64                             ino;
-        *      u64                             ino_generation;
+        *      union {
+        *              struct {
+        *                      u32             maj;
+        *                      u32             min;
+        *                      u64             ino;
+        *                      u64             ino_generation;
+        *              };
+        *              struct {
+        *                      u8              build_id_size;
+        *                      u8              __reserved_1;
+        *                      u16             __reserved_2;
+        *                      u8              build_id[20];
+        *              };
+        *      };
         *      u32                             prot, flags;
         *      char                            filename[];
         *      struct sample_id                sample_id;

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 55d18791a72de38b77ae29440cf5b0a57b8db37d..c37401e3e5f7326b2dbbe1762f5150d0bc28d6e2 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -53,6 +53,7 @@
 #include <linux/min_heap.h>
 #include <linux/highmem.h>
 #include <linux/pgtable.h>
+#include <linux/buildid.h>
 
 #include "internal.h"
 
@@ -397,6 +398,7 @@ static atomic_t nr_ksymbol_events __read_mostly;
 static atomic_t nr_bpf_events __read_mostly;
 static atomic_t nr_cgroup_events __read_mostly;
 static atomic_t nr_text_poke_events __read_mostly;
+static atomic_t nr_build_id_events __read_mostly;
 
 static LIST_HEAD(pmus);
 static DEFINE_MUTEX(pmus_lock);
@@ -4673,6 +4675,8 @@ static void unaccount_event(struct perf_event *event)
                dec = true;
        if (event->attr.mmap || event->attr.mmap_data)
                atomic_dec(&nr_mmap_events);
+       if (event->attr.build_id)
+               atomic_dec(&nr_build_id_events);
        if (event->attr.comm)
                atomic_dec(&nr_comm_events);
        if (event->attr.namespaces)
@@ -8046,6 +8050,8 @@ struct perf_mmap_event {
        u64                     ino;
        u64                     ino_generation;
        u32                     prot, flags;
+       u8                      build_id[BUILD_ID_SIZE_MAX];
+       u32                     build_id_size;
 
        struct {
                struct perf_event_header        header;
@@ -8077,6 +8083,7 @@ static void perf_event_mmap_output(struct perf_event *event,
        struct perf_sample_data sample;
        int size = mmap_event->event_id.header.size;
        u32 type = mmap_event->event_id.header.type;
+       bool use_build_id;
        int ret;
 
        if (!perf_event_mmap_match(event, data))
@@ -8101,13 +8108,25 @@ static void perf_event_mmap_output(struct perf_event *event,
        mmap_event->event_id.pid = perf_event_pid(event, current);
        mmap_event->event_id.tid = perf_event_tid(event, current);
 
+       use_build_id = event->attr.build_id && mmap_event->build_id_size;
+
+       if (event->attr.mmap2 && use_build_id)
+               mmap_event->event_id.header.misc |= PERF_RECORD_MISC_MMAP_BUILD_ID;
+
        perf_output_put(&handle, mmap_event->event_id);
 
        if (event->attr.mmap2) {
-               perf_output_put(&handle, mmap_event->maj);
-               perf_output_put(&handle, mmap_event->min);
-               perf_output_put(&handle, mmap_event->ino);
-               perf_output_put(&handle, mmap_event->ino_generation);
+               if (use_build_id) {
+                       u8 size[4] = { (u8) mmap_event->build_id_size, 0, 0, 0 };
+
+                       __output_copy(&handle, size, 4);
+                       __output_copy(&handle, mmap_event->build_id, BUILD_ID_SIZE_MAX);
+               } else {
+                       perf_output_put(&handle, mmap_event->maj);
+                       perf_output_put(&handle, mmap_event->min);
+                       perf_output_put(&handle, mmap_event->ino);
+                       perf_output_put(&handle, mmap_event->ino_generation);
+               }
                perf_output_put(&handle, mmap_event->prot);
                perf_output_put(&handle, mmap_event->flags);
        }
@@ -8236,6 +8255,9 @@ got_name:
 
        mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
 
+       if (atomic_read(&nr_build_id_events))
+               build_id_parse(vma, mmap_event->build_id, &mmap_event->build_id_size);
+
        perf_iterate_sb(perf_event_mmap_output,
                       mmap_event,
                       NULL);
@@ -11172,6 +11194,8 @@ static void account_event(struct perf_event *event)
                inc = true;
        if (event->attr.mmap || event->attr.mmap_data)
                atomic_inc(&nr_mmap_events);
+       if (event->attr.build_id)
+               atomic_inc(&nr_build_id_events);
        if (event->attr.comm)
                atomic_inc(&nr_comm_events);
        if (event->attr.namespaces)