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authorMartin KaFai Lau <kafai@fb.com>2021-05-07 17:50:11 -0700
committerDaniel Borkmann <daniel@iogearbox.net>2021-05-11 23:23:07 +0200
commit569c484f9995f489f2b80dd134269fe07d2b900d (patch)
tree9d03bf753a09cbc9d555097070e3a201b4f2b37b /samples
parent096eccdef0b32f47e9354231ddc3aaaf9527d51c (diff)
bpf: Limit static tcp-cc functions in the .BTF_ids list to x86
During the discussion in [0]. It was pointed out that static functions in ppc64 is prefixed with ".". For example, the 'readelf -s vmlinux.ppc': 89326: c000000001383280 24 NOTYPE LOCAL DEFAULT 31 cubictcp_init 89327: c000000000c97c50 168 FUNC LOCAL DEFAULT 2 .cubictcp_init The one with FUNC type is ".cubictcp_init" instead of "cubictcp_init". The "." seems to be done by arch/powerpc/include/asm/ppc_asm.h. This caused that pahole cannot generate the BTF for these tcp-cc kernel functions because pahole only captures the FUNC type and "cubictcp_init" is not. It then failed the kernel compilation in ppc64. This behavior is only reported in ppc64 so far. I tried arm64, s390, and sparc64 and did not observe this "." prefix and NOTYPE behavior. Since the kfunc call is only supported in the x86_64 and x86_32 JIT, this patch limits those tcp-cc functions to x86 only to avoid unnecessary compilation issue in other ARCHs. In the future, we can examine if it is better to change all those functions from static to extern. [0] https://lore.kernel.org/bpf/4e051459-8532-7b61-c815-f3435767f8a0@kernel.org/ Fixes: e78aea8b2170 ("bpf: tcp: Put some tcp cong functions in allowlist for bpf-tcp-cc") Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Michal Suchánek <msuchanek@suse.de> Cc: Jiri Slaby <jslaby@suse.com> Cc: Jiri Olsa <jolsa@redhat.com> Link: https://lore.kernel.org/bpf/20210508005011.3863757-1-kafai@fb.com
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