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tracing/probes: Add a function to search a member of a struct/union
Add btf_find_struct_member() API to search a member of a given data structure or union from the member's name. Link: https://lore.kernel.org/all/169272156248.160970.8868479822371129043.stgit@devnote2/ Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reviewed-by: Alan Maguire <alan.maguire@oracle.com> Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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@ -1,6 +1,7 @@
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/btf.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include "trace_btf.h"
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@ -51,3 +52,71 @@ const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s3
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return NULL;
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}
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#define BTF_ANON_STACK_MAX 16
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struct btf_anon_stack {
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u32 tid;
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u32 offset;
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};
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/*
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* Find a member of data structure/union by name and return it.
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* Return NULL if not found, or -EINVAL if parameter is invalid.
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* If the member is an member of anonymous union/structure, the offset
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* of that anonymous union/structure is stored into @anon_offset. Caller
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* can calculate the correct offset from the root data structure by
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* adding anon_offset to the member's offset.
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*/
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const struct btf_member *btf_find_struct_member(struct btf *btf,
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const struct btf_type *type,
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const char *member_name,
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u32 *anon_offset)
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{
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struct btf_anon_stack *anon_stack;
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const struct btf_member *member;
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u32 tid, cur_offset = 0;
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const char *name;
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int i, top = 0;
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anon_stack = kcalloc(BTF_ANON_STACK_MAX, sizeof(*anon_stack), GFP_KERNEL);
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if (!anon_stack)
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return ERR_PTR(-ENOMEM);
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retry:
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if (!btf_type_is_struct(type)) {
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member = ERR_PTR(-EINVAL);
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goto out;
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}
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for_each_member(i, type, member) {
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if (!member->name_off) {
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/* Anonymous union/struct: push it for later use */
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type = btf_type_skip_modifiers(btf, member->type, &tid);
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if (type && top < BTF_ANON_STACK_MAX) {
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anon_stack[top].tid = tid;
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anon_stack[top++].offset =
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cur_offset + member->offset;
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}
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} else {
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name = btf_name_by_offset(btf, member->name_off);
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if (name && !strcmp(member_name, name)) {
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if (anon_offset)
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*anon_offset = cur_offset;
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goto out;
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}
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}
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}
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if (top > 0) {
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/* Pop from the anonymous stack and retry */
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tid = anon_stack[--top].tid;
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cur_offset = anon_stack[top].offset;
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type = btf_type_by_id(btf, tid);
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goto retry;
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}
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member = NULL;
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out:
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kfree(anon_stack);
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return member;
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}
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@ -5,3 +5,7 @@ const struct btf_type *btf_find_func_proto(const char *func_name,
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struct btf **btf_p);
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const struct btf_param *btf_get_func_param(const struct btf_type *func_proto,
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s32 *nr);
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const struct btf_member *btf_find_struct_member(struct btf *btf,
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const struct btf_type *type,
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const char *member_name,
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u32 *anon_offset);
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