generator: Disable ARM configs with BPF enabled in -next with clang-13

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]>

Author: nathanchance

generator/yml/0009-llvm-13.yml

@@ -64,17 +64,23 @@
   #  Next  #
   ##########
   - {<< : *arm32_v5,          << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
-  - {<< : *arm32_v6,          << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
+  # BPF uses check_mul_overflow() with a 'long long' value, which is broken prior to clang-14:
+  # https://github.com/llvm/llvm-project/commit/5c91b98c5d45243352bf10262454bcac77cd3fed
+  # - {<< : *arm32_v6,          << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
   - {<< : *arm32_v7,          << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
   - {<< : *arm32_v7_t,        << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
   - {<< : *arm32_imx,         << : *next,             << : *llvm_full,       boot: false, << : *llvm_13}
   - {<< : *arm32_omap,        << : *next,             << : *llvm_full,       boot: false, << : *llvm_13}
   - {<< : *arm32_lpae_fp,     << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
-  - {<< : *arm32_allmod,      << : *next,             << : *llvm_full,       boot: false, << : *llvm_13}
+  # BPF uses check_mul_overflow() with a 'long long' value, which is broken prior to clang-14:
+  # https://github.com/llvm/llvm-project/commit/5c91b98c5d45243352bf10262454bcac77cd3fed
+  # - {<< : *arm32_allmod,      << : *next,             << : *llvm_full,       boot: false, << : *llvm_13}
   - {<< : *arm32_allno,       << : *next,             << : *llvm_full,       boot: false, << : *llvm_13}
-  - {<< : *arm32_allyes,      << : *next,             << : *llvm_full,       boot: false, << : *llvm_13}
-  - {<< : *arm32_alpine,      << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
-  - {<< : *arm32_suse,        << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
+  # BPF uses check_mul_overflow() with a 'long long' value, which is broken prior to clang-14:
+  # https://github.com/llvm/llvm-project/commit/5c91b98c5d45243352bf10262454bcac77cd3fed
+  # - {<< : *arm32_allyes,      << : *next,             << : *llvm_full,       boot: false, << : *llvm_13}
+  # - {<< : *arm32_alpine,      << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
+  # - {<< : *arm32_suse,        << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
   - {<< : *arm64,             << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
   - {<< : *arm64_lto_full,    << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}
   - {<< : *arm64_lto_thin,    << : *next,             << : *llvm_full,       boot: true,  << : *llvm_13}