[PATCH bpf-next] bpf: add support to read cpu_entry in bpf program

[Florian Lehner <dev@xxxxxxxxxxx>]

Add new field "cpu_entry" to bpf_perf_event_data which could be read by
bpf programs attached to perf events. The value contains the CPU value
recorded by specifying sample_type with PERF_SAMPLE_CPU when calling
perf_event_open().

Signed-off-by: Florian Lehner <dev@xxxxxxxxxxx>
---
 include/uapi/linux/bpf_perf_event.h       |  4 ++++
 kernel/trace/bpf_trace.c                  | 13 +++++++++++++
 tools/include/uapi/linux/bpf_perf_event.h |  4 ++++
 3 files changed, 21 insertions(+)

diff --git a/include/uapi/linux/bpf_perf_event.h b/include/uapi/linux/bpf_perf_event.h
index eb1b9d21250c..4856b4396ece 100644
--- a/include/uapi/linux/bpf_perf_event.h
+++ b/include/uapi/linux/bpf_perf_event.h
@@ -14,6 +14,10 @@ struct bpf_perf_event_data {
 	bpf_user_pt_regs_t regs;
 	__u64 sample_period;
 	__u64 addr;
+	struct {
+		u32	cpu;
+		u32	reserved;
+	}			cpu_entry;
 };
 
 #endif /* _UAPI__LINUX_BPF_PERF_EVENT_H__ */
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index afb232b1d7c2..2b303221af5c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2176,6 +2176,11 @@ static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type
 		if (!bpf_ctx_narrow_access_ok(off, size, size_u64))
 			return false;
 		break;
+	case bpf_ctx_range(struct bpf_perf_event_data, cpu_entry):
+		bpf_ctx_record_field_size(info, size_u64);
+		if (!bpf_ctx_narrow_access_ok(off, size, size_u64))
+			return false;
+		break;
 	default:
 		if (size != sizeof(long))
 			return false;
@@ -2208,6 +2213,14 @@ static u32 pe_prog_convert_ctx_access(enum bpf_access_type type,
 				      bpf_target_off(struct perf_sample_data, addr, 8,
 						     target_size));
 		break;
+	case offsetof(struct bpf_perf_event_data, cpu_entry):
+		*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, cpu_entry, 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,
diff --git a/tools/include/uapi/linux/bpf_perf_event.h b/tools/include/uapi/linux/bpf_perf_event.h
index eb1b9d21250c..4856b4396ece 100644
--- a/tools/include/uapi/linux/bpf_perf_event.h
+++ b/tools/include/uapi/linux/bpf_perf_event.h
@@ -14,6 +14,10 @@ struct bpf_perf_event_data {
 	bpf_user_pt_regs_t regs;
 	__u64 sample_period;
 	__u64 addr;
+	struct {
+		u32	cpu;
+		u32	reserved;
+	}			cpu_entry;
 };
 
 #endif /* _UAPI__LINUX_BPF_PERF_EVENT_H__ */
-- 
2.44.0