[PATCH bpf-next 2/3] bpf: Add bpf_perf_event_read_sample() helper

[Namhyung Kim]

The bpf_perf_event_read_sample() helper is to get the specified sample
data (by using PERF_SAMPLE_* flag in the argument) from BPF to make a
decision for filtering on samples.  Currently PERF_SAMPLE_IP and
PERF_SAMPLE_DATA flags are supported only.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 include/uapi/linux/bpf.h       | 23 ++++++++++++++++
 kernel/trace/bpf_trace.c       | 49 ++++++++++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h | 23 ++++++++++++++++
 3 files changed, 95 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 94659f6b3395..cba501de9373 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5481,6 +5481,28 @@ union bpf_attr {
  *		0 on success.
  *
  *		**-ENOENT** if the bpf_local_storage cannot be found.
+ *
+ * long bpf_perf_event_read_sample(struct bpf_perf_event_data *ctx, void *buf, u32 size, u64 sample_flags)
+ *	Description
+ *		For an eBPF program attached to a perf event, retrieve the
+ *		sample data associated to *ctx*	and store it in the buffer
+ *		pointed by *buf* up to size *size* bytes.
+ *
+ *		The *sample_flags* should contain a single value in the
+ *		**enum perf_event_sample_format**.
+ *	Return
+ *		On success, number of bytes written to *buf*. On error, a
+ *		negative value.
+ *
+ *		The *buf* can be set to **NULL** to return the number of bytes
+ *		required to store the requested sample data.
+ *
+ *		**-EINVAL** if *sample_flags* is not a PERF_SAMPLE_* flag.
+ *
+ *		**-ENOENT** if the associated perf event doesn't have the data.
+ *
+ *		**-ENOSYS** if system doesn't support the sample data to be
+ *		retrieved.
  */
 #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
 	FN(unspec, 0, ##ctx)				\
@@ -5695,6 +5717,7 @@ union bpf_attr {
 	FN(user_ringbuf_drain, 209, ##ctx)		\
 	FN(cgrp_storage_get, 210, ##ctx)		\
 	FN(cgrp_storage_delete, 211, ##ctx)		\
+	FN(perf_event_read_sample, 212, ##ctx)		\
 	/* */
 
 /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index ce0228c72a93..befd937afa3c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -28,6 +28,7 @@
 
 #include <uapi/linux/bpf.h>
 #include <uapi/linux/btf.h>
+#include <uapi/linux/perf_event.h>
 
 #include <asm/tlb.h>
 
@@ -1743,6 +1744,52 @@ static const struct bpf_func_proto bpf_read_branch_records_proto = {
 	.arg4_type      = ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_perf_event_read_sample, struct bpf_perf_event_data_kern *, ctx,
+	   void *, buf, u32, size, u64, flags)
+{
+	struct perf_sample_data *sd = ctx->data;
+	void *data;
+	u32 to_copy = sizeof(u64);
+
+	/* only allow a single sample flag */
+	if (!is_power_of_2(flags))
+		return -EINVAL;
+
+	/* support reading only already populated info */
+	if (flags & ~sd->sample_flags)
+		return -ENOENT;
+
+	switch (flags) {
+	case PERF_SAMPLE_IP:
+		data = &sd->ip;
+		break;
+	case PERF_SAMPLE_ADDR:
+		data = &sd->addr;
+		break;
+	default:
+		return -ENOSYS;
+	}
+
+	if (!buf)
+		return to_copy;
+
+	if (size < to_copy)
+		to_copy = size;
+
+	memcpy(buf, data, to_copy);
+	return to_copy;
+}
+
+static const struct bpf_func_proto bpf_perf_event_read_sample_proto = {
+	.func           = bpf_perf_event_read_sample,
+	.gpl_only       = true,
+	.ret_type       = RET_INTEGER,
+	.arg1_type      = ARG_PTR_TO_CTX,
+	.arg2_type      = ARG_PTR_TO_MEM_OR_NULL,
+	.arg3_type      = ARG_CONST_SIZE_OR_ZERO,
+	.arg4_type      = ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *
 pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -1759,6 +1806,8 @@ pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_read_branch_records_proto;
 	case BPF_FUNC_get_attach_cookie:
 		return &bpf_get_attach_cookie_proto_pe;
+	case BPF_FUNC_perf_event_read_sample:
+		return &bpf_perf_event_read_sample_proto;
 	default:
 		return bpf_tracing_func_proto(func_id, prog);
 	}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 94659f6b3395..cba501de9373 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5481,6 +5481,28 @@ union bpf_attr {
  *		0 on success.
  *
  *		**-ENOENT** if the bpf_local_storage cannot be found.
+ *
+ * long bpf_perf_event_read_sample(struct bpf_perf_event_data *ctx, void *buf, u32 size, u64 sample_flags)
+ *	Description
+ *		For an eBPF program attached to a perf event, retrieve the
+ *		sample data associated to *ctx*	and store it in the buffer
+ *		pointed by *buf* up to size *size* bytes.
+ *
+ *		The *sample_flags* should contain a single value in the
+ *		**enum perf_event_sample_format**.
+ *	Return
+ *		On success, number of bytes written to *buf*. On error, a
+ *		negative value.
+ *
+ *		The *buf* can be set to **NULL** to return the number of bytes
+ *		required to store the requested sample data.
+ *
+ *		**-EINVAL** if *sample_flags* is not a PERF_SAMPLE_* flag.
+ *
+ *		**-ENOENT** if the associated perf event doesn't have the data.
+ *
+ *		**-ENOSYS** if system doesn't support the sample data to be
+ *		retrieved.
  */
 #define ___BPF_FUNC_MAPPER(FN, ctx...)			\
 	FN(unspec, 0, ##ctx)				\
@@ -5695,6 +5717,7 @@ union bpf_attr {
 	FN(user_ringbuf_drain, 209, ##ctx)		\
 	FN(cgrp_storage_get, 210, ##ctx)		\
 	FN(cgrp_storage_delete, 211, ##ctx)		\
+	FN(perf_event_read_sample, 212, ##ctx)		\
 	/* */
 
 /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
-- 
2.38.1.273.g43a17bfeac-goog