linux-kernel - [PATCH] bpf: Constify struct btf_kind

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Message-ID: <9192ab72b2e9c66aefd6520f359a20297186327f.1726417289.git.christophe.jaillet@wanadoo.fr>
Date: Sun, 15 Sep 2024 18:21:54 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Martin KaFai Lau <martin.lau@...ux.dev>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	bpf@...r.kernel.org
Subject: [PATCH] bpf: Constify struct btf_kind_operations

'struct btf_kind_operations' are not modified in this driver.

Constifying this structures moves some data to a read-only section, so
increase overall security, especially when the structure holds some
function pointers.

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
 184320	   7091	    548	 191959	  2edd7	kernel/bpf/btf.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
 184896	   6515	    548	 191959	  2edd7	kernel/bpf/btf.o

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
Compile tested-only.
---
 kernel/bpf/btf.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index d2f87db9131e..432eda0f6550 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -2808,7 +2808,7 @@ static void btf_ref_type_log(struct btf_verifier_env *env,
 	btf_verifier_log(env, "type_id=%u", t->type);
 }
 
-static struct btf_kind_operations modifier_ops = {
+static const struct btf_kind_operations modifier_ops = {
 	.check_meta = btf_ref_type_check_meta,
 	.resolve = btf_modifier_resolve,
 	.check_member = btf_modifier_check_member,
@@ -2817,7 +2817,7 @@ static struct btf_kind_operations modifier_ops = {
 	.show = btf_modifier_show,
 };
 
-static struct btf_kind_operations ptr_ops = {
+static const struct btf_kind_operations ptr_ops = {
 	.check_meta = btf_ref_type_check_meta,
 	.resolve = btf_ptr_resolve,
 	.check_member = btf_ptr_check_member,
@@ -2858,7 +2858,7 @@ static void btf_fwd_type_log(struct btf_verifier_env *env,
 	btf_verifier_log(env, "%s", btf_type_kflag(t) ? "union" : "struct");
 }
 
-static struct btf_kind_operations fwd_ops = {
+static const struct btf_kind_operations fwd_ops = {
 	.check_meta = btf_fwd_check_meta,
 	.resolve = btf_df_resolve,
 	.check_member = btf_df_check_member,
@@ -3109,7 +3109,7 @@ static void btf_array_show(const struct btf *btf, const struct btf_type *t,
 	__btf_array_show(btf, t, type_id, data, bits_offset, show);
 }
 
-static struct btf_kind_operations array_ops = {
+static const struct btf_kind_operations array_ops = {
 	.check_meta = btf_array_check_meta,
 	.resolve = btf_array_resolve,
 	.check_member = btf_array_check_member,
@@ -4185,7 +4185,7 @@ static void btf_struct_show(const struct btf *btf, const struct btf_type *t,
 	__btf_struct_show(btf, t, type_id, data, bits_offset, show);
 }
 
-static struct btf_kind_operations struct_ops = {
+static const struct btf_kind_operations struct_ops = {
 	.check_meta = btf_struct_check_meta,
 	.resolve = btf_struct_resolve,
 	.check_member = btf_struct_check_member,
@@ -4353,7 +4353,7 @@ static void btf_enum_show(const struct btf *btf, const struct btf_type *t,
 	btf_show_end_type(show);
 }
 
-static struct btf_kind_operations enum_ops = {
+static const struct btf_kind_operations enum_ops = {
 	.check_meta = btf_enum_check_meta,
 	.resolve = btf_df_resolve,
 	.check_member = btf_enum_check_member,
@@ -4456,7 +4456,7 @@ static void btf_enum64_show(const struct btf *btf, const struct btf_type *t,
 	btf_show_end_type(show);
 }
 
-static struct btf_kind_operations enum64_ops = {
+static const struct btf_kind_operations enum64_ops = {
 	.check_meta = btf_enum64_check_meta,
 	.resolve = btf_df_resolve,
 	.check_member = btf_enum_check_member,
@@ -4534,7 +4534,7 @@ static void btf_func_proto_log(struct btf_verifier_env *env,
 	btf_verifier_log(env, ")");
 }
 
-static struct btf_kind_operations func_proto_ops = {
+static const struct btf_kind_operations func_proto_ops = {
 	.check_meta = btf_func_proto_check_meta,
 	.resolve = btf_df_resolve,
 	/*
@@ -4592,7 +4592,7 @@ static int btf_func_resolve(struct btf_verifier_env *env,
 	return 0;
 }
 
-static struct btf_kind_operations func_ops = {
+static const struct btf_kind_operations func_ops = {
 	.check_meta = btf_func_check_meta,
 	.resolve = btf_func_resolve,
 	.check_member = btf_df_check_member,
-- 
2.46.0