Thread (8 messages) 8 messages, 2 authors, 2021-10-01

Re: [PATCH bpf-next v4 2/3] libbpf: support detecting and attaching of writable tracepoint program

From: Andrii Nakryiko <hidden>
Date: 2021-10-01 22:21:17
Also in: bpf

On Thu, Sep 30, 2021 at 2:00 AM Hou Tao [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Program on writable tracepoint is BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
but its attachment is the same as BPF_PROG_TYPE_RAW_TRACEPOINT.

Signed-off-by: Hou Tao <redacted>
---
 tools/lib/bpf/libbpf.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7544d7d09160..80faa53dff35 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -8005,6 +8005,8 @@ static const struct bpf_sec_def section_defs[] = {
        SEC_DEF("tp/",                  TRACEPOINT, 0, SEC_NONE, attach_tp),
        SEC_DEF("raw_tracepoint/",      RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),
        SEC_DEF("raw_tp/",              RAW_TRACEPOINT, 0, SEC_NONE, attach_raw_tp),
+       SEC_DEF("raw_tracepoint.w/",    RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),
+       SEC_DEF("raw_tp.w/",            RAW_TRACEPOINT_WRITABLE, 0, SEC_NONE, attach_raw_tp),
        SEC_DEF("tp_btf/",              TRACING, BPF_TRACE_RAW_TP, SEC_ATTACH_BTF, attach_trace),
        SEC_DEF("fentry/",              TRACING, BPF_TRACE_FENTRY, SEC_ATTACH_BTF, attach_trace),
        SEC_DEF("fmod_ret/",            TRACING, BPF_MODIFY_RETURN, SEC_ATTACH_BTF, attach_trace),
@@ -9762,12 +9764,21 @@ struct bpf_link *bpf_program__attach_raw_tracepoint(const struct bpf_program *pr

 static struct bpf_link *attach_raw_tp(const struct bpf_program *prog, long cookie)
 {
-       const char *tp_name;
+       static const char *prefixes[] = {
+               "raw_tp/",
+               "raw_tracepoint/",
+               "raw_tp.w/",
+               "raw_tracepoint.w/",
+       };
+       size_t i;
+       const char *tp_name = NULL;

-       if (str_has_pfx(prog->sec_name, "raw_tp/"))
-               tp_name = prog->sec_name + sizeof("raw_tp/") - 1;
-       else
-               tp_name = prog->sec_name + sizeof("raw_tracepoint/") - 1;
+       for (i = 0; i < ARRAY_SIZE(prefixes); i++) {
+               if (str_has_pfx(prog->sec_name, prefixes[i])) {
+                       tp_name = prog->sec_name + strlen(prefixes[i]);
+                       break;
+               }
+       }
Let's add if (!tp_name) check here for the future if we forget to
update this prefixes list. It's going to be a really unpleasant
SIGSEGV otherwise.
        return bpf_program__attach_raw_tracepoint(prog, tp_name);
 }
--
2.29.2
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