On Tue, 1 Sep 2026 09:47:17 +0900 "Masami Hiramatsu (Google)" <[email protected]> wrote:
> From: Masami Hiramatsu (Google) <[email protected]> > > btf_find_struct_member() traverses into nested anonymous structures and > unions to find a struct member. However, get_bitoffset_of_field() in > trace_probe.c checked btf_type_kflag(type) using the outer parent type > instead of the actual anonymous structure/union that directly contains > the found member. > > If the parent structure and anonymous structure have mismatched kflags > (e.g., the parent has kflag=0 while the anonymous structure has kflag=1 > because it contains bitfields), the bitfield size encoded in the upper > 8 bits of member->offset is erroneously treated as part of the byte/bit > offset, corrupting the resolved offset and failing to set last_bitsize. > Similarly, btf_find_struct_member() pushed anonymous member offsets > onto anon_stack without masking BTF_MEMBER_BIT_OFFSET() when kflag is set. > > To fix this problem, update btf_find_struct_member() to return actual > containing structure/union type via member_type, use appropriate > __btf_member_bit_offset() to get bit offset, and use member_type for > btf_type_kflag() in get_bitoffset_of_field(). > > Fixes: c440adfbe302 ("tracing/probes: Support BTF based data structure field > access") > Cc: [email protected] > Reported-by: Sashiko <[email protected]> > Closes: > https://lore.kernel.org/all/[email protected]/ > Assisted-by: Antigravity:gemini-3.7-flash > Signed-off-by: Masami Hiramatsu (Google) <[email protected]> > --- > @@ -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; > + } Is this just to fix the indentation? If so, can you make this a separate patch? We don't need it to be part of a patch that gets backported. It may make it more difficult to do so. -- Steve > > if (next) > ctx->offset += next - fieldname;
