[PATCH v2] MIPS: Make MIPS32_O32 depends on !CC_IS_CLANG

When build kernel with Clang [1]:

$ make CC=clang loongson3_defconfig
$ make CC=clang

there exists the following error:

  Checking missing-syscalls for O32
  CALL    scripts/checksyscalls.sh
error: ABI 'o32' is not supported on CPU 'mips64r2'
make[1]: *** [Kbuild:48: missing-syscalls] Error 1
make: *** [arch/mips/Makefile:419: archprepare] Error 2

This is a known bug [2] with Clang, as Simon Atanasyan said,
"There is no plan on support O32 for MIPS64 due to lack of
resources".

It is not a good idea to remove CONFIG_MIPS32_O32=y directly
in defconfig due to GCC works well, as Nathan said, the config
should not even be selectable when build kernel with Clang, so
just make MIPS32_O32 depends on !CC_IS_CLANG.

[1] https://www.kernel.org/doc/html/latest/kbuild/llvm.html
[2] https://bugs.llvm.org/show_bug.cgi?id=38063

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/mips/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 3a38d27..f6ba59f 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig

@@ -3318,6 +3318,8 @@ config SYSVIPC_COMPAT
 config MIPS32_O32
 	bool "Kernel support for o32 binaries"
 	depends on 64BIT
+	# https://bugs.llvm.org/show_bug.cgi?id=38063
+	depends on !CC_IS_CLANG
 	select ARCH_WANT_OLD_COMPAT_IPC
 	select COMPAT
 	select MIPS32_COMPAT

-- 
2.1.0

On Thu, Mar 04, 2021 at 02:19:38PM +0800, Tiezhu Yang wrote:

When build kernel with Clang [1]:

Sorry I did not catch this in the first revision but I think this would
sound better as:

When building with Clang [1]:

I think the kernel part is obvious :) couple more comments about the
commit message inline.

$ make CC=clang loongson3_defconfig
$ make CC=clang

there exists the following error:

  Checking missing-syscalls for O32
  CALL    scripts/checksyscalls.sh
error: ABI 'o32' is not supported on CPU 'mips64r2'
make[1]: *** [Kbuild:48: missing-syscalls] Error 1
make: *** [arch/mips/Makefile:419: archprepare] Error 2

This is a known bug [2] with Clang, as Simon Atanasyan said,
"There is no plan on support O32 for MIPS64 due to lack of
resources".

It is not a good idea to remove CONFIG_MIPS32_O32=y directly
in defconfig due to GCC works well, as Nathan said, the config

in defconfig because GCC works, as...

should not even be selectable when build kernel with Clang, so

                                     building with Clang

just make MIPS32_O32 depends on !CC_IS_CLANG.

[1] https://www.kernel.org/doc/html/latest/kbuild/llvm.html
[2] https://bugs.llvm.org/show_bug.cgi?id=38063

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>

I don't know if Nick will have any comments but for me:

Acked-by: Nathan Chancellor <nathan@kernel.org>

I have added this patch and the LLVM bug to our issue tracker:

https://github.com/ClangBuiltLinux/linux/issues/884