linux-kernel - [PATCH 1/2] [v3] bpf: hide unused bpf_patch_call

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Message-Id: <20230602135128.1498362-1-arnd@kernel.org>
Date:   Fri,  2 Jun 2023 15:50:18 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Yonghong Song <yhs@...a.com>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        John Fastabend <john.fastabend@...il.com>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] [v3] bpf: hide unused bpf_patch_call_args

From: Arnd Bergmann <arnd@...db.de>

This function is only used when CONFIG_BPF_JIT_ALWAYS_ON is disabled,
but CONFIG_BPF_SYSCALL is enabled. When both are turned off, the
prototype is missing but the unused function is still compiled,
as seen from this W=1 warning:

kernel/bpf/core.c:2075:6: error: no previous prototype for 'bpf_patch_call_args' [-Werror=missing-prototypes]

Add a matching #ifdef for the definition to leave it out.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
v3: fix incorrect changelog text
v2: change indentation to align arguments better. Still not great
as the line is just too long
---
 kernel/bpf/core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 7421487422d48..0926714641eb5 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2064,14 +2064,16 @@ EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
 };
 #undef PROG_NAME_LIST
 #define PROG_NAME_LIST(stack_size) PROG_NAME_ARGS(stack_size),
-static u64 (*interpreters_args[])(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5,
-				  const struct bpf_insn *insn) = {
+static __maybe_unused
+u64 (*interpreters_args[])(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5,
+			   const struct bpf_insn *insn) = {
 EVAL6(PROG_NAME_LIST, 32, 64, 96, 128, 160, 192)
 EVAL6(PROG_NAME_LIST, 224, 256, 288, 320, 352, 384)
 EVAL4(PROG_NAME_LIST, 416, 448, 480, 512)
 };
 #undef PROG_NAME_LIST
 
+#ifdef CONFIG_BPF_SYSCALL
 void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth)
 {
 	stack_depth = max_t(u32, stack_depth, 1);
@@ -2080,6 +2082,7 @@ void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth)
 		__bpf_call_base_args;
 	insn->code = BPF_JMP | BPF_CALL_ARGS;
 }
+#endif
 
 #else
 static unsigned int __bpf_prog_ret0_warn(const void *ctx,
-- 
2.39.2