Commit 21a56fc5 authored by Eduard Zingerman's avatar Eduard Zingerman Committed by Alexei Starovoitov
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selftests/bpf: #define LOCAL_LABEL_LEN for jit_disasm_helpers.c 



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: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240823080644.263943-4-eddyz87@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent c52a1e6e

tools/testing/selftests/bpf/jit_disasm_helpers.c

+14 −3
Original line number Diff line number Diff line
@@ -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;