bpf: Make find_linfo widely available

Move find_linfo() as bpf_find_linfo() into core.c to allow for its use
in the verifier in subsequent patches.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20260408021359.3786905-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 39 insertions, 42 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d8fb9d61f5ce..0136a108d083 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3945,6 +3945,7 @@ static inline bool bpf_is_subprog(const struct bpf_prog *prog)
 	return prog->aux->func_idx != 0;
 }
 
+const struct bpf_line_info *bpf_find_linfo(const struct bpf_prog *prog, u32 insn_off);
 void bpf_get_linfo_file_line(struct btf *btf, const struct bpf_line_info *linfo,
 			     const char **filep, const char **linep, int *nump);
 int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char **filep,
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index ada76f997177..066b86e7233c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -3335,6 +3335,43 @@ void bpf_get_linfo_file_line(struct btf *btf, const struct bpf_line_info *linfo,
 		*nump = BPF_LINE_INFO_LINE_NUM(linfo->line_col);
 }
 
+const struct bpf_line_info *bpf_find_linfo(const struct bpf_prog *prog, u32 insn_off)
+{
+	const struct bpf_line_info *linfo;
+	u32 nr_linfo;
+	int l, r, m;
+
+	nr_linfo = prog->aux->nr_linfo;
+	if (!nr_linfo || insn_off >= prog->len)
+		return NULL;
+
+	linfo = prog->aux->linfo;
+	/* Loop invariant: linfo[l].insn_off <= insns_off.
+	 * linfo[0].insn_off == 0 which always satisfies above condition.
+	 * Binary search is searching for rightmost linfo entry that satisfies
+	 * the above invariant, giving us the desired record that covers given
+	 * instruction offset.
+	 */
+	l = 0;
+	r = nr_linfo - 1;
+	while (l < r) {
+		/* (r - l + 1) / 2 means we break a tie to the right, so if:
+		 * l=1, r=2, linfo[l].insn_off <= insn_off, linfo[r].insn_off > insn_off,
+		 * then m=2, we see that linfo[m].insn_off > insn_off, and so
+		 * r becomes 1 and we exit the loop with correct l==1.
+		 * If the tie was broken to the left, m=1 would end us up in
+		 * an endless loop where l and m stay at 1 and r stays at 2.
+		 */
+		m = l + (r - l + 1) / 2;
+		if (linfo[m].insn_off <= insn_off)
+			l = m;
+		else
+			r = m - 1;
+	}
+
+	return &linfo[l];
+}
+
 int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char **filep,
 			   const char **linep, int *nump)
 {
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 37d72b052192..6fd030fd6eeb 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -329,47 +329,6 @@ __printf(2, 3) void bpf_log(struct bpf_verifier_log *log,
 }
 EXPORT_SYMBOL_GPL(bpf_log);
 
-static const struct bpf_line_info *
-find_linfo(const struct bpf_verifier_env *env, u32 insn_off)
-{
-	const struct bpf_line_info *linfo;
-	const struct bpf_prog *prog;
-	u32 nr_linfo;
-	int l, r, m;
-
-	prog = env->prog;
-	nr_linfo = prog->aux->nr_linfo;
-
-	if (!nr_linfo || insn_off >= prog->len)
-		return NULL;
-
-	linfo = prog->aux->linfo;
-	/* Loop invariant: linfo[l].insn_off <= insns_off.
-	 * linfo[0].insn_off == 0 which always satisfies above condition.
-	 * Binary search is searching for rightmost linfo entry that satisfies
-	 * the above invariant, giving us the desired record that covers given
-	 * instruction offset.
-	 */
-	l = 0;
-	r = nr_linfo - 1;
-	while (l < r) {
-		/* (r - l + 1) / 2 means we break a tie to the right, so if:
-		 * l=1, r=2, linfo[l].insn_off <= insn_off, linfo[r].insn_off > insn_off,
-		 * then m=2, we see that linfo[m].insn_off > insn_off, and so
-		 * r becomes 1 and we exit the loop with correct l==1.
-		 * If the tie was broken to the left, m=1 would end us up in
-		 * an endless loop where l and m stay at 1 and r stays at 2.
-		 */
-		m = l + (r - l + 1) / 2;
-		if (linfo[m].insn_off <= insn_off)
-			l = m;
-		else
-			r = m - 1;
-	}
-
-	return &linfo[l];
-}
-
 static const char *ltrim(const char *s)
 {
 	while (isspace(*s))
@@ -390,7 +349,7 @@ __printf(3, 4) void verbose_linfo(struct bpf_verifier_env *env,
 		return;
 
 	prev_linfo = env->prev_linfo;
-	linfo = find_linfo(env, insn_off);
+	linfo = bpf_find_linfo(env->prog, insn_off);
 	if (!linfo || linfo == prev_linfo)
 		return;