netdev - [PATCH bpf-next 1/2] bpf: add support to read sample address in bpf program

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Message-ID: <20180306185502.1948838-2-qinteng@fb.com>
Date:   Tue, 6 Mar 2018 10:55:01 -0800
From:   Teng Qin <qinteng@...com>
To:     <ast@...com>, <daniel@...earbox.net>, <netdev@...r.kernel.org>
CC:     <yhs@...com>, <qinteng@...com>, <kernel-team@...com>
Subject: [PATCH bpf-next 1/2] bpf: add support to read sample address in bpf program

This commit adds new field "addr" to bpf_perf_event_data which could be
read and used by bpf programs attached to perf events. The value of the
field is copied from bpf_perf_event_data_kern.addr and contains the
address value recorded by specifying sample_type with PERF_SAMPLE_ADDR
when calling perf_event_open.

Signed-off-by: Teng Qin <qinteng@...com>
---
 include/uapi/linux/bpf_perf_event.h |  1 +
 kernel/trace/bpf_trace.c            | 20 ++++++++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/bpf_perf_event.h b/include/uapi/linux/bpf_perf_event.h
index 8f95303..eb1b9d2 100644
--- a/include/uapi/linux/bpf_perf_event.h
+++ b/include/uapi/linux/bpf_perf_event.h
@@ -13,6 +13,7 @@
 struct bpf_perf_event_data {
 	bpf_user_pt_regs_t regs;
 	__u64 sample_period;
+	__u64 addr;
 };
 
 #endif /* _UAPI__LINUX_BPF_PERF_EVENT_H__ */
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index c0a9e31..c634e09 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -726,8 +726,7 @@ const struct bpf_prog_ops tracepoint_prog_ops = {
 static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
 				    struct bpf_insn_access_aux *info)
 {
-	const int size_sp = FIELD_SIZEOF(struct bpf_perf_event_data,
-					 sample_period);
+	const int size_u64 = sizeof(u64);
 
 	if (off < 0 || off >= sizeof(struct bpf_perf_event_data))
 		return false;
@@ -738,8 +737,13 @@ static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type
 
 	switch (off) {
 	case bpf_ctx_range(struct bpf_perf_event_data, sample_period):
-		bpf_ctx_record_field_size(info, size_sp);
-		if (!bpf_ctx_narrow_access_ok(off, size, size_sp))
+		bpf_ctx_record_field_size(info, size_u64);
+		if (!bpf_ctx_narrow_access_ok(off, size, size_u64))
+			return false;
+		break;
+	case bpf_ctx_range(struct bpf_perf_event_data, addr):
+		bpf_ctx_record_field_size(info, size_u64);
+		if (!bpf_ctx_narrow_access_ok(off, size, size_u64))
 			return false;
 		break;
 	default:
@@ -766,6 +770,14 @@ static u32 pe_prog_convert_ctx_access(enum bpf_access_type type,
 				      bpf_target_off(struct perf_sample_data, period, 8,
 						     target_size));
 		break;
+	case offsetof(struct bpf_perf_event_data, addr):
+		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
+						       data), si->dst_reg, si->src_reg,
+				      offsetof(struct bpf_perf_event_data_kern, data));
+		*insn++ = BPF_LDX_MEM(BPF_DW, si->dst_reg, si->dst_reg,
+				      bpf_target_off(struct perf_sample_data, addr, 8,
+						     target_size));
+		break;
 	default:
 		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
 						       regs), si->dst_reg, si->src_reg,
-- 
2.9.5