On Mon, 31 Aug 2026 13:14:29 -0400 Steven Rostedt <[email protected]> wrote:
> On Tue, 1 Sep 2026 00:06:16 +0900 > "Masami Hiramatsu (Google)" <[email protected]> wrote: > > diff --git a/kernel/trace/trace_btf.h b/kernel/trace/trace_btf.h > > index 4bc44bc261e6..4bd26bceae23 100644 > > --- a/kernel/trace/trace_btf.h > > +++ b/kernel/trace/trace_btf.h > > @@ -8,4 +8,5 @@ const struct btf_param *btf_get_func_param(const struct > > btf_type *func_proto, > > const struct btf_member *btf_find_struct_member(struct btf *btf, > > const struct btf_type *type, > > const char *member_name, > > - u32 *anon_offset); > > + u32 *anon_offset, > > + const struct btf_type > > **member_type); > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > > index c4163904ba74..ce2a7bb00d28 100644 > > --- a/kernel/trace/trace_probe.c > > +++ b/kernel/trace/trace_probe.c > > @@ -625,6 +625,7 @@ static int get_bitoffset_of_field(char **pfieldname, > > const struct btf_type **pty > > { > > const struct btf_type *type = *ptype; > > const struct btf_member *field; > > + const struct btf_type *mtype = NULL; > > Why initialize mtype to NULL? > > > struct btf *btf = ctx_btf(ctx); > > char *fieldname = *pfieldname; > > int bitoffs = 0; > > @@ -640,7 +641,7 @@ static int get_bitoffset_of_field(char **pfieldname, > > const struct btf_type **pty > > > > anon_offs = 0; > > field = btf_find_struct_member(btf, type, fieldname, > > - &anon_offs); > > + &anon_offs, &mtype); > > If mtype is not set here, then field would be either an error or NULL. > > > if (IS_ERR(field)) { > > trace_probe_log_err(ctx->offset, BAD_BTF_TID); > > return PTR_ERR(field); > > If field is an error or NULL, it exits out early. > > > @@ -653,7 +654,7 @@ static int get_bitoffset_of_field(char **pfieldname, > > const struct btf_type **pty > > bitoffs += anon_offs; > > > > /* Accumulate the bit-offsets of the dot-connected fields */ > > - if (btf_type_kflag(type)) { > > + if (btf_type_kflag(mtype)) { > > mtype should be guaranteed as set here (maybe set to NULL, but set regardless) > > Now, if btf_find_struct_member() did not set mtype, because this is in a > loop, in a second iteration, mtype would be stale. Ah, indeed! > > So either set it to NULL at the top of the loop, or don't set it at all. > > Or am I missing something? OK, let me just drop NULL initialization because it is a kind of hardening. (Since anon_offs is left uninitialized, mtype = NULL seems somewhat unbalanced.) Thanks! > > -- Steve > > > > > bitoffs += BTF_MEMBER_BIT_OFFSET(field->offset); > > ctx->last_bitsize = > > BTF_MEMBER_BITFIELD_SIZE(field->offset); > > } else { > > @@ -661,11 +662,11 @@ static int get_bitoffset_of_field(char **pfieldname, > > const struct btf_type **pty > > ctx->last_bitsize = 0; > > } > > > > - type = btf_type_skip_modifiers(btf, field->type, NULL); > > - if (!type) { > > - trace_probe_log_err(ctx->offset, BAD_BTF_TID); > > - return -EINVAL; > > - } > > + type = btf_type_skip_modifiers(btf, field->type, NULL); > > + if (!type) { > > + trace_probe_log_err(ctx->offset, BAD_BTF_TID); > > + return -EINVAL; > > + } > > > > if (next) > > ctx->offset += next - fieldname; > -- Masami Hiramatsu (Google) <[email protected]>
