Re: [PATCH AUTOSEL 5.4 316/350] int128: move __uint128_t compiler test to Kconfig

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On Tue, 10 Dec 2019 at 22:13, Sasha Levin <sashal@kernel.org> wrote:
>
> From: Ard Biesheuvel <ardb@kernel.org>
>
> [ Upstream commit c12d3362a74bf0cd9e1d488918d40607b62a3104 ]
>
> In order to use 128-bit integer arithmetic in C code, the architecture
> needs to have declared support for it by setting ARCH_SUPPORTS_INT128,
> and it requires a version of the toolchain that supports this at build
> time. This is why all existing tests for ARCH_SUPPORTS_INT128 also test
> whether __SIZEOF_INT128__ is defined, since this is only the case for
> compilers that can support 128-bit integers.
>
> Let's fold this additional test into the Kconfig declaration of
> ARCH_SUPPORTS_INT128 so that we can also use the symbol in Makefiles,
> e.g., to decide whether a certain object needs to be included in the
> first place.
>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

This does not fix a bug so no need to put it in -stable

> ---
>  arch/arm64/Kconfig | 2 +-
>  arch/riscv/Kconfig | 2 +-
>  arch/x86/Kconfig   | 2 +-
>  crypto/ecc.c       | 2 +-
>  init/Kconfig       | 4 ++++
>  lib/ubsan.c        | 2 +-
>  lib/ubsan.h        | 2 +-
>  7 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 3f047afb982c8..54c38c9cab88a 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -67,7 +67,7 @@ config ARM64
>         select ARCH_USE_QUEUED_SPINLOCKS
>         select ARCH_SUPPORTS_MEMORY_FAILURE
>         select ARCH_SUPPORTS_ATOMIC_RMW
> -       select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000 || CC_IS_CLANG
> +       select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && (GCC_VERSION >= 50000 || CC_IS_CLANG)
>         select ARCH_SUPPORTS_NUMA_BALANCING
>         select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
>         select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 8eebbc8860bbd..75a6c91176221 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -164,7 +164,7 @@ config ARCH_RV32I
>  config ARCH_RV64I
>         bool "RV64I"
>         select 64BIT
> -       select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000
> +       select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && GCC_VERSION >= 50000
>         select HAVE_FUNCTION_TRACER
>         select HAVE_FUNCTION_GRAPH_TRACER
>         select HAVE_FTRACE_MCOUNT_RECORD
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 8ef85139553f5..f2aed8012e9c0 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -24,7 +24,7 @@ config X86_64
>         depends on 64BIT
>         # Options that are inherently 64-bit kernel only:
>         select ARCH_HAS_GIGANTIC_PAGE
> -       select ARCH_SUPPORTS_INT128
> +       select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
>         select ARCH_USE_CMPXCHG_LOCKREF
>         select HAVE_ARCH_SOFT_DIRTY
>         select MODULES_USE_ELF_RELA
> diff --git a/crypto/ecc.c b/crypto/ecc.c
> index dfe114bc0c4af..6e6aab6c987c2 100644
> --- a/crypto/ecc.c
> +++ b/crypto/ecc.c
> @@ -336,7 +336,7 @@ static u64 vli_usub(u64 *result, const u64 *left, u64 right,
>  static uint128_t mul_64_64(u64 left, u64 right)
>  {
>         uint128_t result;
> -#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
> +#if defined(CONFIG_ARCH_SUPPORTS_INT128)
>         unsigned __int128 m = (unsigned __int128)left * right;
>
>         result.m_low  = m;
> diff --git a/init/Kconfig b/init/Kconfig
> index b4daad2bac233..020526f681c03 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -785,6 +785,10 @@ config ARCH_SUPPORTS_NUMA_BALANCING
>  config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
>         bool
>
> +config CC_HAS_INT128
> +       def_bool y
> +       depends on !$(cc-option,-D__SIZEOF_INT128__=0)
> +
>  #
>  # For architectures that know their GCC __int128 support is sound
>  #
> diff --git a/lib/ubsan.c b/lib/ubsan.c
> index 0c4681118fcd2..fc552d524ef77 100644
> --- a/lib/ubsan.c
> +++ b/lib/ubsan.c
> @@ -119,7 +119,7 @@ static void val_to_string(char *str, size_t size, struct type_descriptor *type,
>  {
>         if (type_is_int(type)) {
>                 if (type_bit_width(type) == 128) {
> -#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
> +#if defined(CONFIG_ARCH_SUPPORTS_INT128)
>                         u_max val = get_unsigned_val(type, value);
>
>                         scnprintf(str, size, "0x%08x%08x%08x%08x",
> diff --git a/lib/ubsan.h b/lib/ubsan.h
> index b8fa83864467f..7b56c09473a98 100644
> --- a/lib/ubsan.h
> +++ b/lib/ubsan.h
> @@ -78,7 +78,7 @@ struct invalid_value_data {
>         struct type_descriptor *type;
>  };
>
> -#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
> +#if defined(CONFIG_ARCH_SUPPORTS_INT128)
>  typedef __int128 s_max;
>  typedef unsigned __int128 u_max;
>  #else
> --
> 2.20.1
>