Disable ARM configs with BPF enabled in -next with clang-13 #807
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After commit 9aa0ebde0014 ("bpf, verifier: Improve precision of
BPF_MUL") [1], there is an error in certain ARM configurations that
enable CONFIG_BPF_SYSCALL:
ld.lld: error: undefined symbol: __mulodi4
>>> referenced by verifier.c:14221 (/builds/linux/kernel/bpf/verifier.c:14221)
>>> kernel/bpf/verifier.o:(adjust_reg_min_max_vals) in archive vmlinux.a
>>> referenced by verifier.c:14222 (/builds/linux/kernel/bpf/verifier.c:14222)
>>> kernel/bpf/verifier.o:(adjust_reg_min_max_vals) in archive vmlinux.a
>>> referenced by verifier.c:14223 (/builds/linux/kernel/bpf/verifier.c:14223)
>>> kernel/bpf/verifier.o:(adjust_reg_min_max_vals) in archive vmlinux.a
>>> referenced 1 more times
This was encountered previously [2], where it was fixed in clang-14 and
avoided in the kernel with a source code workaround (that ended up being
cleaner anyways).
This time around, inserting a source code workaround would not be as
clean, as it may involve disabling a core part of the kernel on a
limited condition (as it only impacts one supported LLVM version and
architecture combination) or having a separate code path for this
situation.
For now, just disable the builds that are impacted by this. If more
people notice this problem, we can explore bumping the minimum supported
version of LLVM for building `ARCH=arm` to 14.
Link: https://git.kernel.org/bpf/bpf-next/c/9aa0ebde0014f01a8ca82adcbf43b92345da0d50 [1]
Link: ClangBuiltLinux/linux#1438 [2]
Signed-off-by: Nathan Chancellor <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
nathanchance
requested review from
nickdesaulniers,
JustinStitt and
bwendling
as code owners
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After commit 9aa0ebde0014 ("bpf, verifier: Improve precision of BPF_MUL"), there is an error in certain ARM configurations that enable
CONFIG_BPF_SYSCALL:This was encountered previously, where it was fixed in clang-14 and avoided in the kernel with a source code workaround (that ended up being cleaner anyways).
This time around, inserting a source code workaround would not be as clean, as it may involve disabling a core part of the kernel on a limited condition (as it only impacts one supported LLVM version and architecture combination) or having a separate code path for this situation.
For now, just disable the builds that are impacted by this. If more people notice this problem, we can explore bumping the minimum supported version of LLVM for building
ARCH=armto 14.