2023-09-15 20:27:39

by Nick Desaulniers

[permalink] [raw]
Subject: [PATCH bpf v3 2/2] bpf: Fix BTF_ID symbol generation collision in tools/

Marcus and Satya reported an issue where BTF_ID macro generates same
symbol in separate objects and that breaks final vmlinux link.

ld.lld: error: ld-temp.o <inline asm>:14577:1: symbol
'__BTF_ID__struct__cgroup__624' is already defined

This can be triggered under specific configs when __COUNTER__ happens to
be the same for the same symbol in two different translation units,
which is already quite unlikely to happen.

Add __LINE__ number suffix to make BTF_ID symbol more unique, which is
not a complete fix, but it would help for now and meanwhile we can work
on better solution as suggested by Andrii.

Cc: [email protected]
Reported-by: Satya Durga Srinivasu Prabhala <[email protected]>
Reported-by: Marcus Seyfarth <[email protected]>
Closes: https://github.com/ClangBuiltLinux/linux/issues/1913
Debugged-by: Nathan Chancellor <[email protected]>
Co-developed-by: Jiri Olsa <[email protected]>
Link: https://lore.kernel.org/bpf/CAEf4Bzb5KQ2_LmhN769ifMeSJaWfebccUasQOfQKaOd0nQ51tw@mail.gmail.com/
Signed-off-by: Nick Desaulniers <[email protected]>
---
tools/include/linux/btf_ids.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/include/linux/btf_ids.h b/tools/include/linux/btf_ids.h
index 71e54b1e3796..2f882d5cb30f 100644
--- a/tools/include/linux/btf_ids.h
+++ b/tools/include/linux/btf_ids.h
@@ -38,7 +38,7 @@ asm( \
____BTF_ID(symbol)

#define __ID(prefix) \
- __PASTE(prefix, __COUNTER__)
+ __PASTE(__PASTE(prefix, __COUNTER__), __LINE__)

/*
* The BTF_ID defines unique symbol for each ID pointing

--
2.42.0.459.ge4e396fd5e-goog