perf: Add ability to sample machine state on interrupt

Enable capture of interrupted machine state for each sample.

Registers to sample are passed per event in the sample_regs_intr bitmask.

To sample interrupt machine state, the PERF_SAMPLE_INTR_REGS must be passed in
sample_type.

The list of available registers is arch dependent and provided by asm/perf_regs.h

Registers are laid out as u64 in the order of the bit order of sample_intr_regs.

This patch also adds a new ABI version PERF_ATTR_SIZE_VER4 because we extend
the perf_event_attr struct with a new u64 field.

Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: cebbert.lkml@gmail.com
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-api@vger.kernel.org
Link: http://lkml.kernel.org/r/1411559322-16548-2-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 63 insertions, 5 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 893a0d07986f..68d46d536e24 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -79,7 +79,7 @@ struct perf_branch_stack {
         struct perf_branch_entry        entries[0];
 };
 
-struct perf_regs_user {
+struct perf_regs {
         __u64           abi;
         struct pt_regs  *regs;
 };
@@ -600,7 +600,8 @@ struct perf_sample_data {
         struct perf_callchain_entry     *callchain;
         struct perf_raw_record          *raw;
         struct perf_branch_stack        *br_stack;
-        struct perf_regs_user           regs_user;
+        struct perf_regs                regs_user;
+        struct perf_regs                regs_intr;
         u64                             stack_user_size;
         u64                             weight;
         /*
@@ -630,6 +631,8 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
         data->weight = 0;
         data->data_src.val = PERF_MEM_NA;
         data->txn = 0;
+        data->regs_intr.abi = PERF_SAMPLE_REGS_ABI_NONE;
+        data->regs_intr.regs = NULL;
 }
 
 extern void perf_output_sample(struct perf_output_handle *handle,
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 9d845404d875..9b79abbd1ab8 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -137,8 +137,9 @@ enum perf_event_sample_format {
         PERF_SAMPLE_DATA_SRC                    = 1U << 15,
         PERF_SAMPLE_IDENTIFIER                  = 1U << 16,
         PERF_SAMPLE_TRANSACTION                 = 1U << 17,
+        PERF_SAMPLE_REGS_INTR                   = 1U << 18,
 
-        PERF_SAMPLE_MAX = 1U << 18,             /* non-ABI */
+        PERF_SAMPLE_MAX = 1U << 19,             /* non-ABI */
 };
 
 /*
@@ -238,6 +239,7 @@ enum perf_event_read_format {
 #define PERF_ATTR_SIZE_VER2     80      /* add: branch_sample_type */
 #define PERF_ATTR_SIZE_VER3     96      /* add: sample_regs_user */
                                         /* add: sample_stack_user */
+#define PERF_ATTR_SIZE_VER4     104     /* add: sample_regs_intr */
 
 /*
  * Hardware event_id to monitor via a performance monitoring event:
@@ -334,6 +336,15 @@ struct perf_event_attr {
 
         /* Align to u64. */
         __u32   __reserved_2;
+        /*
+         * Defines set of regs to dump for each sample
+         * state captured on:
+         *  - precise = 0: PMU interrupt
+         *  - precise > 0: sampled instruction
+         *
+         * See asm/perf_regs.h for details.
+         */
+        __u64   sample_regs_intr;
 };
 
 #define perf_flags(attr)        (*(&(attr)->read_format + 1))
@@ -686,6 +697,8 @@ enum perf_event_type {
          *      { u64                   weight;   } && PERF_SAMPLE_WEIGHT
          *      { u64                   data_src; } && PERF_SAMPLE_DATA_SRC
          *      { u64                   transaction; } && PERF_SAMPLE_TRANSACTION
+         *      { u64                   abi; # enum perf_sample_regs_abi
+         *        u64                   regs[weight(mask)]; } && PERF_SAMPLE_REGS_INTR
          * };
          */
         PERF_RECORD_SAMPLE                      = 9,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1cd5eef1fcdd..c2be1597ece7 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4460,7 +4460,7 @@ perf_output_sample_regs(struct perf_output_handle *handle,
         }
 }
 
-static void perf_sample_regs_user(struct perf_regs_user *regs_user,
+static void perf_sample_regs_user(struct perf_regs *regs_user,
                                   struct pt_regs *regs)
 {
         if (!user_mode(regs)) {
@@ -4476,6 +4476,14 @@ static void perf_sample_regs_user(struct perf_regs_user *regs_user,
         }
 }
 
+static void perf_sample_regs_intr(struct perf_regs *regs_intr,
+                                  struct pt_regs *regs)
+{
+        regs_intr->regs = regs;
+        regs_intr->abi  = perf_reg_abi(current);
+}
+
+
 /*
  * Get remaining task size from user stack pointer.
  *
@@ -4857,6 +4865,23 @@ void perf_output_sample(struct perf_output_handle *handle,
         if (sample_type & PERF_SAMPLE_TRANSACTION)
                 perf_output_put(handle, data->txn);
 
+        if (sample_type & PERF_SAMPLE_REGS_INTR) {
+                u64 abi = data->regs_intr.abi;
+                /*
+                 * If there are no regs to dump, notice it through
+                 * first u64 being zero (PERF_SAMPLE_REGS_ABI_NONE).
+                 */
+                perf_output_put(handle, abi);
+
+                if (abi) {
+                        u64 mask = event->attr.sample_regs_intr;
+
+                        perf_output_sample_regs(handle,
+                                                data->regs_intr.regs,
+                                                mask);
+                }
+        }
+
         if (!event->attr.watermark) {
                 int wakeup_events = event->attr.wakeup_events;
 
@@ -4943,7 +4968,7 @@ void perf_prepare_sample(struct perf_event_header *header,
                  * in case new sample type is added, because we could eat
                  * up the rest of the sample size.
                  */
-                struct perf_regs_user *uregs = &data->regs_user;
+                struct perf_regs *uregs = &data->regs_user;
                 u16 stack_size = event->attr.sample_stack_user;
                 u16 size = sizeof(u64);
 
@@ -4964,6 +4989,21 @@ void perf_prepare_sample(struct perf_event_header *header,
                 data->stack_user_size = stack_size;
                 header->size += size;
         }
+
+        if (sample_type & PERF_SAMPLE_REGS_INTR) {
+                /* regs dump ABI info */
+                int size = sizeof(u64);
+
+                perf_sample_regs_intr(&data->regs_intr, regs);
+
+                if (data->regs_intr.regs) {
+                        u64 mask = event->attr.sample_regs_intr;
+
+                        size += hweight64(mask) * sizeof(u64);
+                }
+
+                header->size += size;
+        }
 }
 
 static void perf_event_output(struct perf_event *event,
@@ -7151,6 +7191,8 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
                         ret = -EINVAL;
         }
 
+        if (attr->sample_type & PERF_SAMPLE_REGS_INTR)
+                ret = perf_reg_validate(attr->sample_regs_intr);
 out:
         return ret;