Extract local label length as a #define directive and
elaborate why 'i % MAX_LOCAL_LABELS' expression is needed
for local labels array initialization.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
.../testing/selftests/bpf/jit_disasm_helpers.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/bpf/jit_disasm_helpers.c b/tools/testing/selftests/bpf/jit_disasm_helpers.c
index 1b0f1fd267c0..febd6b12e372 100644
--- a/tools/testing/selftests/bpf/jit_disasm_helpers.c
+++ b/tools/testing/selftests/bpf/jit_disasm_helpers.c
@@ -16,6 +16,11 @@
*/
#define MAX_LOCAL_LABELS 32
+/* Local labels are encoded as 'L42', this requires 4 bytes of storage:
+ * 3 characters + zero byte
+ */
+#define LOCAL_LABEL_LEN 4
+
static bool llvm_initialized;
struct local_labels {
@@ -23,7 +28,7 @@ struct local_labels {
__u32 prog_len;
__u32 cnt;
__u32 pcs[MAX_LOCAL_LABELS];
- char names[MAX_LOCAL_LABELS][4];
+ char names[MAX_LOCAL_LABELS][LOCAL_LABEL_LEN];
};
static const char *lookup_symbol(void *data, uint64_t ref_value, uint64_t *ref_type,
@@ -118,8 +123,14 @@ static int disasm_one_func(FILE *text_out, uint8_t *image, __u32 len)
}
qsort(labels.pcs, labels.cnt, sizeof(*labels.pcs), cmp_u32);
for (i = 0; i < labels.cnt; ++i)
- /* use (i % 100) to avoid format truncation warning */
- snprintf(labels.names[i], sizeof(labels.names[i]), "L%d", i % 100);
+ /* gcc is unable to infer upper bound for labels.cnt and assumes
+ * it to be U32_MAX. U32_MAX takes 10 decimal digits.
+ * snprintf below prints into labels.names[*],
+ * which has space only for two digits and a letter.
+ * To avoid truncation warning use (i % MAX_LOCAL_LABELS),
+ * which informs gcc about printed value upper bound.
+ */
+ snprintf(labels.names[i], sizeof(labels.names[i]), "L%d", i % MAX_LOCAL_LABELS);
/* now print with labels */
labels.print_phase = true;
--
2.46.0
