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Subject[PATCH 1/4] perf: add ability to sample machine state on interrupt
Date
Enable capture of interrupted machine state in 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.

Signed-off-by: Stephane Eranian <eranian@google.com>
---
include/linux/perf_event.h | 7 +++++--
include/uapi/linux/perf_event.h | 14 ++++++++++++-
kernel/events/core.c | 44 +++++++++++++++++++++++++++++++++++++++--
3 files changed, 60 insertions(+), 5 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 707617a..4970c1d 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -78,7 +78,7 @@ struct perf_branch_stack {
struct perf_branch_entry entries[0];
};

-struct perf_regs_user {
+struct perf_regs {
__u64 abi;
struct pt_regs *regs;
};
@@ -595,7 +595,8 @@ 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;
/*
@@ -618,6 +619,8 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
data->weight = 0;
data->data_src.val = 0;
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 9269de2..543cc19 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 */
};

/*
@@ -334,6 +335,15 @@ struct perf_event_attr {

/* Align to u64. */
__u32 __reserved_2;
+ /*
+ * Defines set of user regs to dump on samples.
+ * state capture 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 +696,8 @@ 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 57e9190..018939c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4296,7 +4296,7 @@ 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)) {
@@ -4312,6 +4312,14 @@ static void perf_sample_regs_user(struct perf_regs_user *regs_user,
}
}

+static void perf_sample_regs_intr(struct perf_regs *regs_user,
+ struct pt_regs *regs)
+{
+ regs_user->regs = regs;
+ regs_user->abi = perf_reg_abi(current);
+}
+
+
/*
* Get remaining task size from user stack pointer.
*
@@ -4693,6 +4701,22 @@ 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;

@@ -4779,7 +4803,7 @@ 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);

@@ -4800,6 +4824,20 @@ 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,
@@ -6994,6 +7032,8 @@ 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;

--
1.8.3.2


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