1 files changed, 122 insertions, 0 deletions
diff --git a/kernel/trace/trace_btf.c b/kernel/trace/trace_btf.c
new file mode 100644
index 000000000000..ca224d53bfdc
--- /dev/null
+++ b/kernel/trace/trace_btf.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/btf.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include "trace_btf.h"
+
+/*
+ * Find a function proto type by name, and return the btf_type with its btf
+ * in *@btf_p. Return NULL if not found.
+ * Note that caller has to call btf_put(*@btf_p) after using the btf_type.
+ */
+const struct btf_type *btf_find_func_proto(const char *func_name, struct btf **btf_p)
+{
+	const struct btf_type *t;
+	s32 id;
+
+	id = bpf_find_btf_id(func_name, BTF_KIND_FUNC, btf_p);
+	if (id < 0)
+		return NULL;
+
+	/* Get BTF_KIND_FUNC type */
+	t = btf_type_by_id(*btf_p, id);
+	if (!t || !btf_type_is_func(t))
+		goto err;
+
+	/* The type of BTF_KIND_FUNC is BTF_KIND_FUNC_PROTO */
+	t = btf_type_by_id(*btf_p, t->type);
+	if (!t || !btf_type_is_func_proto(t))
+		goto err;
+
+	return t;
+err:
+	btf_put(*btf_p);
+	return NULL;
+}
+
+/*
+ * Get function parameter with the number of parameters.
+ * This can return NULL if the function has no parameters.
+ * It can return -EINVAL if the @func_proto is not a function proto type.
+ */
+const struct btf_param *btf_get_func_param(const struct btf_type *func_proto, s32 *nr)
+{
+	if (!btf_type_is_func_proto(func_proto))
+		return ERR_PTR(-EINVAL);
+
+	*nr = btf_type_vlen(func_proto);
+	if (*nr > 0)
+		return (const struct btf_param *)(func_proto + 1);
+	else
+		return NULL;
+}
+
+#define BTF_ANON_STACK_MAX	16
+
+struct btf_anon_stack {
+	u32 tid;
+	u32 offset;
+};
+
+/*
+ * Find a member of data structure/union by name and return it.
+ * Return NULL if not found, or -EINVAL if parameter is invalid.
+ * If the member is an member of anonymous union/structure, the offset
+ * of that anonymous union/structure is stored into @anon_offset. Caller
+ * can calculate the correct offset from the root data structure by
+ * adding anon_offset to the member's offset.
+ */
+const struct btf_member *btf_find_struct_member(struct btf *btf,
+						const struct btf_type *type,
+						const char *member_name,
+						u32 *anon_offset)
+{
+	struct btf_anon_stack *anon_stack;
+	const struct btf_member *member;
+	u32 tid, cur_offset = 0;
+	const char *name;
+	int i, top = 0;
+
+	anon_stack = kcalloc(BTF_ANON_STACK_MAX, sizeof(*anon_stack), GFP_KERNEL);
+	if (!anon_stack)
+		return ERR_PTR(-ENOMEM);
+
+retry:
+	if (!btf_type_is_struct(type)) {
+		member = ERR_PTR(-EINVAL);
+		goto out;
+	}
+
+	for_each_member(i, type, member) {
+		if (!member->name_off) {
+			/* Anonymous union/struct: push it for later use */
+			type = btf_type_skip_modifiers(btf, member->type, &tid);
+			if (type && top < BTF_ANON_STACK_MAX) {
+				anon_stack[top].tid = tid;
+				anon_stack[top++].offset =
+					cur_offset + member->offset;
+			}
+		} else {
+			name = btf_name_by_offset(btf, member->name_off);
+			if (name && !strcmp(member_name, name)) {
+				if (anon_offset)
+					*anon_offset = cur_offset;
+				goto out;
+			}
+		}
+	}
+	if (top > 0) {
+		/* Pop from the anonymous stack and retry */
+		tid = anon_stack[--top].tid;
+		cur_offset = anon_stack[top].offset;
+		type = btf_type_by_id(btf, tid);
+		goto retry;
+	}
+	member = NULL;
+
+out:
+	kfree(anon_stack);
+	return member;
+}
+