linux-kernel - [PATCH v1 2/3] perf bpf-utils: Constify bpil_array

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Message-ID: <20250902181713.309797-3-irogers@google.com>
Date: Tue,  2 Sep 2025 11:17:12 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Blake Jones <blakejones@...gle.com>, 
	Zhongqiu Han <quic_zhonhan@...cinc.com>, Andrii Nakryiko <andrii@...nel.org>, 
	Song Liu <songliubraving@...com>, Dave Marchevsky <davemarchevsky@...com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org, Howard Chu <howardchu95@...il.com>, song@...nel.org, 
	Yonghong Song <yonghong.song@...ux.dev>
Subject: [PATCH v1 2/3] perf bpf-utils: Constify bpil_array_desc

The array's contents is a compile time constant. Constify to make the
code more intention revealing and avoid unintended errors.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/bpf-utils.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/bpf-utils.c b/tools/perf/util/bpf-utils.c
index 80b1d2b3729b..64a558344696 100644
--- a/tools/perf/util/bpf-utils.c
+++ b/tools/perf/util/bpf-utils.c
@@ -20,7 +20,7 @@ struct bpil_array_desc {
 				 */
 };
 
-static struct bpil_array_desc bpil_array_desc[] = {
+static const struct bpil_array_desc bpil_array_desc[] = {
 	[PERF_BPIL_JITED_INSNS] = {
 		offsetof(struct bpf_prog_info, jited_prog_insns),
 		offsetof(struct bpf_prog_info, jited_prog_len),
@@ -129,12 +129,10 @@ get_bpf_prog_info_linear(int fd, __u64 arrays)
 
 	/* step 2: calculate total size of all arrays */
 	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
 		bool include_array = (arrays & (1UL << i)) > 0;
-		struct bpil_array_desc *desc;
 		__u32 count, size;
 
-		desc = bpil_array_desc + i;
-
 		/* kernel is too old to support this field */
 		if (info_len < desc->array_offset + sizeof(__u32) ||
 		    info_len < desc->count_offset + sizeof(__u32) ||
@@ -163,13 +161,12 @@ get_bpf_prog_info_linear(int fd, __u64 arrays)
 	ptr = info_linear->data;
 
 	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
-		struct bpil_array_desc *desc;
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
 		__u32 count, size;
 
 		if ((arrays & (1UL << i)) == 0)
 			continue;
 
-		desc  = bpil_array_desc + i;
 		count = bpf_prog_info_read_offset_u32(&info, desc->count_offset);
 		size  = bpf_prog_info_read_offset_u32(&info, desc->size_offset);
 		bpf_prog_info_set_offset_u32(&info_linear->info,
@@ -192,13 +189,12 @@ get_bpf_prog_info_linear(int fd, __u64 arrays)
 
 	/* step 6: verify the data */
 	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
-		struct bpil_array_desc *desc;
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
 		__u32 v1, v2;
 
 		if ((arrays & (1UL << i)) == 0)
 			continue;
 
-		desc = bpil_array_desc + i;
 		v1 = bpf_prog_info_read_offset_u32(&info, desc->count_offset);
 		v2 = bpf_prog_info_read_offset_u32(&info_linear->info,
 						   desc->count_offset);
@@ -224,13 +220,12 @@ void bpil_addr_to_offs(struct perf_bpil *info_linear)
 	int i;
 
 	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
-		struct bpil_array_desc *desc;
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
 		__u64 addr, offs;
 
 		if ((info_linear->arrays & (1UL << i)) == 0)
 			continue;
 
-		desc = bpil_array_desc + i;
 		addr = bpf_prog_info_read_offset_u64(&info_linear->info,
 						     desc->array_offset);
 		offs = addr - ptr_to_u64(info_linear->data);
@@ -244,13 +239,12 @@ void bpil_offs_to_addr(struct perf_bpil *info_linear)
 	int i;
 
 	for (i = PERF_BPIL_FIRST_ARRAY; i < PERF_BPIL_LAST_ARRAY; ++i) {
-		struct bpil_array_desc *desc;
+		const struct bpil_array_desc *desc = &bpil_array_desc[i];
 		__u64 addr, offs;
 
 		if ((info_linear->arrays & (1UL << i)) == 0)
 			continue;
 
-		desc = bpil_array_desc + i;
 		offs = bpf_prog_info_read_offset_u64(&info_linear->info,
 						     desc->array_offset);
 		addr = offs + ptr_to_u64(info_linear->data);
-- 
2.51.0.355.g5224444f11-goog