[PATCH bpf-next v1 11/14] bpf: Preserve source attribution without source text

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

GCC emits BTF line records with a file name and line number, but leaves the
source line string empty. bpf_diag_source() currently treats that empty string
as if the complete line record were unavailable, so diagnostics fall back to
an instruction number and discard the function, file, and line attribution.

Print the available source location before deciding whether source context can
be rendered. When source text is absent, omit only the source context and retain
the diagnostic annotation and instruction context.

Fixes: b9c5d822f677 ("bpf: Add source and instruction diagnostic context")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/diagnostics.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index df9259fa0ea7..44d0b7c5f05f 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -833,11 +833,9 @@ static void bpf_diag_source(struct bpf_verifier_env *env, u32 insn_idx, const ch
 	linfo = bpf_find_linfo(env->prog, insn_idx);
 	if (btf && linfo)
 		bpf_get_linfo_source(btf, linfo, &src);
-	if (!src.file || !*src.file || !src.line || !*src.line) {
+	if (!src.file || !*src.file) {
 		diag_write(env, "  insn %u\n", insn_idx);
-		diag_print_source_annotation(env, 0, 0, label, msg);
-		diag_print_insn_context(env, insn_idx, disasm_lines);
-		goto out_restore;
+		goto out_annotation;
 	}
 
 	subprog = bpf_find_containing_subprog(env, insn_idx);
@@ -847,6 +845,8 @@ static void bpf_diag_source(struct bpf_verifier_env *env, u32 insn_idx, const ch
 		diag_write(env, "  %s @ %s:%d:%d\n", func, src.file, src.line_num, src.line_col);
 	else
 		diag_write(env, "  %s:%d:%d\n", src.file, src.line_num, src.line_col);
+	if (!src.line || !*src.line)
+		goto out_annotation;
 
 	start_line = src.line_num - BPF_DIAG_CONTEXT;
 	end_line = src.line_num + BPF_DIAG_CONTEXT;
@@ -889,7 +889,11 @@ static void bpf_diag_source(struct bpf_verifier_env *env, u32 insn_idx, const ch
 			diag_print_source_annotation(env, width, indent, label, msg);
 	}
 	diag_print_insn_context(env, insn_idx, disasm_lines);
+	goto out_restore;
 
+out_annotation:
+	diag_print_source_annotation(env, 0, 0, label, msg);
+	diag_print_insn_context(env, insn_idx, disasm_lines);
 out_restore:
 	diag_fmt_restore(env, mark);
 }
-- 
2.53.0