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

[Teng Qin]

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 <qint...@fb.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