tracing/probes: Fix tracepoint event with $arg* to fetch correct argument

To hide the first dummy 'data' argument on the tracepoint probe events,
the BTF argument array was modified (skip the first argument for tracepoint),
but the '$arg*' meta argument parser missed that.

Fix to increment the argument index if it is tracepoint probe. And decrement
the index when searching the type of the argument.

Link: https://lore.kernel.org/all/168657113778.3038017.12245893750241701312.stgit@mhiramat.roam.corp.google.com/
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 473e1c43bc57a3ed593e5aec20f9aee816fcfe12..643aa3a51d5a739f11312bc7455f4b99d2fe3368 100644 (file)
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -456,7 +456,10 @@ static int parse_btf_arg(const char *varname, struct fetch_insn *code,
 
                if (name && !strcmp(name, varname)) {
                        code->op = FETCH_OP_ARG;
-                       code->param = i;
+                       if (ctx->flags & TPARG_FL_TPOINT)
+                               code->param = i + 1;
+                       else
+                               code->param = i;
                        return 0;
                }
        }
@@ -470,8 +473,11 @@ static const struct fetch_type *parse_btf_arg_type(int arg_idx,
        struct btf *btf = traceprobe_get_btf();
        const char *typestr = NULL;
 
-       if (btf && ctx->params)
+       if (btf && ctx->params) {
+               if (ctx->flags & TPARG_FL_TPOINT)
+                       arg_idx--;
                typestr = type_from_btf_id(btf, ctx->params[arg_idx].type);
+       }
 
        return find_fetch_type(typestr, ctx->flags);
 }