Re: [RFC PATCH 09/20] int128: move __uint128_t compiler test to Kconfig

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

On Mon, 30 Sep 2019 at 13:01, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> On Mon, Sep 30, 2019 at 2:41 AM Ard Biesheuvel
> <ard.biesheuvel@linaro.org> wrote:
> >
> > 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 <ard.biesheuvel@linaro.org>
>
>
> Do you still need CONFIG_ARCH_SUPPORTS_INT128 ?
>

arm64 needs GCC 5 or later for int128_t support, since older versions
emit support library function calls that we don't implement.

I guess we could fold that into the CC_HAS_INT128 test as well though

> I do not know which part in lib/ubsan.c or crypto/ecc.c
> is arch-dependent...
>
>
>
>
>
> > ---
> >  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 3adcec05b1f6..a0f764e2f299 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -69,7 +69,7 @@ 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_FRAME_POINTERS
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 59a4727ecd6c..99be78ac7b33 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -127,7 +127,7 @@ 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 222855cc0158..97f74a2e1cf3 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 dfe114bc0c4a..6e6aab6c987c 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 bd7d650d4a99..f5566a985b9e 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -780,6 +780,10 @@ 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 e7d31735950d..b652cc14dd60 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 b8fa83864467..7b56c09473a9 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
> > --
> > 2.17.1
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
>
>
> --
> Best Regards
> Masahiro Yamada