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tracing/probes: Clarify btf_find_struct_member() container parameter and add kernel-doc

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btf_find_struct_member() returns the containing structure or union type
(which can be an inner anonymous struct/union rather than the outer
passed type) via its last parameter. However, the parameter was named
@member_type, which easily confuses readers and static analyzers into
thinking it returns the member field's own datatype.

Rename @member_type to @container_type in the prototype, definition,
and callers to make the relationship explicit. Also convert the comment
above btf_find_struct_member() to standard kernel-doc format, documenting
all parameters and return values.

Link: https://lore.kernel.org/all/179030954365.77418.17193777972248047975.stgit@devnote2/

Assisted-by: LLM
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Masami Hiramatsu (Google) 2026-09-25 13:12:23 +09:00
parent 06e0d3b89d
commit 3ccfe2a1a8
3 changed files with 28 additions and 14 deletions
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34
kernel/trace/trace_btf.c
View File

@ -59,19 +59,33 @@ struct btf_anon_stack {
u32 offset;
};
/*
* Find a member of data structure/union by name and return it.
* Return NULL if not found, or ERR_PTR(-EINVAL) if parameter is invalid.
* If the member is a member of an anonymous union/structure, the bit offset
* of that anonymous union/structure is stored into @anon_offset.
* If @member_type is non-NULL, the actual containing structure/union type
* of the found member is stored into @member_type.
/**
* btf_find_struct_member() - Find a member of data structure/union by name
* @btf: Pointer to BTF object.
* @type: Pointer to the struct/union BTF type to search within.
* @member_name: Name of the member to find.
* @anon_offset: Pointer to store bit offset of enclosing anonymous union/struct.
* @container_type: Pointer to store the actual containing struct/union type.
*
* Find a member of data structure/union by name, traversing into anonymous
* unions and structures if necessary.
*
* If the member is inside an anonymous union/structure, the bit offset
* of that anonymous union/structure from @type is stored into @anon_offset.
* If @container_type is non-NULL, the actual struct/union BTF type that
* directly contains the found member is stored into @container_type.
*
* Return:
* * Pointer to &struct btf_member on success.
* * %NULL if the member was not found.
* * %ERR_PTR(-EINVAL) if @type is not a struct/union.
* * %ERR_PTR(-ENOMEM) if memory allocation failed.
*/
const struct btf_member *btf_find_struct_member(struct btf *btf,
const struct btf_type *type,
const char *member_name,
u32 *anon_offset,
const struct btf_type **member_type)
const struct btf_type **container_type)
{
struct btf_anon_stack *anon_stack;
const struct btf_member *member;
@ -103,8 +117,8 @@ const struct btf_member *btf_find_struct_member(struct btf *btf,
if (name && !strcmp(member_name, name)) {
if (anon_offset)
*anon_offset = cur_offset;
if (member_type)
*member_type = type;
if (container_type)
*container_type = type;
goto out;
}
}

2
kernel/trace/trace_btf.h
View File

@ -9,4 +9,4 @@ const struct btf_member *btf_find_struct_member(struct btf *btf,
const struct btf_type *type,
const char *member_name,
u32 *anon_offset,
const struct btf_type **member_type);
const struct btf_type **container_type);

6
kernel/trace/trace_probe.c
View File

@ -625,7 +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;
const struct btf_type *container_type;
struct btf *btf = ctx_btf(ctx);
char *fieldname = *pfieldname;
int bitoffs = 0;
@ -641,7 +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, &mtype);
&anon_offs, &container_type);
if (IS_ERR(field)) {
trace_probe_log_err(ctx->offset, BAD_BTF_TID);
return PTR_ERR(field);
@ -654,7 +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(mtype)) {
if (btf_type_kflag(container_type)) {
bitoffs += BTF_MEMBER_BIT_OFFSET(field->offset);
ctx->last_bitsize = BTF_MEMBER_BITFIELD_SIZE(field->offset);
} else {