linux-kernel - [PATCH bpf-next] bpf: Increase size of BTF_ID_LIST without CONFIG_DEBUG_INFO

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Message-Id: <20230307-bpf-kfuncs-warray-bounds-v1-1-00ad3191f3a6@kernel.org>
Date:   Tue, 07 Mar 2023 08:14:06 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org
Cc:     martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, ndesaulniers@...gle.com,
        trix@...hat.com, bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, patches@...ts.linux.dev,
        Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH bpf-next] bpf: Increase size of BTF_ID_LIST without
 CONFIG_DEBUG_INFO_BTF again

After commit 66e3a13e7c2c ("bpf: Add bpf_dynptr_slice and
bpf_dynptr_slice_rdwr"), clang builds without CONFIG_DEBUG_INFO_BTF
warn:

  kernel/bpf/verifier.c:10298:24: warning: array index 16 is past the end of the array (that has type 'u32[16]' (aka 'unsigned int[16]')) [-Warray-bounds]
                                     meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice_rdwr]) {
                                                     ^                  ~~~~~~~~~~~~~~~~~~~~~~~~
  kernel/bpf/verifier.c:9150:1: note: array 'special_kfunc_list' declared here
  BTF_ID_LIST(special_kfunc_list)
  ^
  include/linux/btf_ids.h:207:27: note: expanded from macro 'BTF_ID_LIST'
  #define BTF_ID_LIST(name) static u32 __maybe_unused name[16];
                            ^
  1 warning generated.

A warning of this nature was previously addressed by
commit beb3d47d1d3d ("bpf: Fix a BTF_ID_LIST bug with
CONFIG_DEBUG_INFO_BTF not set") but there have been new kfuncs added
since then.

Quadruple the size of the CONFIG_DEBUG_INFO_BTF=n definition so that
this problem is unlikely to show up for some time.

Link: https://github.com/ClangBuiltLinux/linux/issues/1810
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 include/linux/btf_ids.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
index 3a4f7cd882ca..00950cc03bff 100644
--- a/include/linux/btf_ids.h
+++ b/include/linux/btf_ids.h
@@ -204,7 +204,7 @@ extern struct btf_id_set8 name;
 
 #else
 
-#define BTF_ID_LIST(name) static u32 __maybe_unused name[16];
+#define BTF_ID_LIST(name) static u32 __maybe_unused name[64];
 #define BTF_ID(prefix, name)
 #define BTF_ID_FLAGS(prefix, name, ...)
 #define BTF_ID_UNUSED

---
base-commit: 36e5e391a25af28dc1f4586f95d577b38ff4ed72
change-id: 20230307-bpf-kfuncs-warray-bounds-c2040e8ee7ee

Best regards,
-- 
Nathan Chancellor <nathan@...nel.org>