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tracing/probes: Fix tracepoint event with $arg* to fetch correct argu…
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…ment

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>
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Masami Hiramatsu (Google) committed Jun 23, 2023
1 parent a2bd0c0 commit 5343179
Showing 1 changed file with 8 additions and 2 deletions.
10 changes: 8 additions & 2 deletions kernel/trace/trace_probe.c
Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
}
Expand All @@ -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);
}
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