From: Nick Desaulniers <ndesaulniers@google.com>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Masahiro Yamada <masahiroy@kernel.org>,
Joe Perches <joe@perches.com>, Arnd Bergmann <arnd@kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
llvm@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 01/10] Documentation: raise minimum supported version of GCC to 5.1
Date: Fri, 10 Sep 2021 17:16:29 -0700 [thread overview]
Message-ID: <CAKwvOd=m1bUZwyV53k2+d+M6rOL04A0WPhH_wOUFU-ZK1BOWFg@mail.gmail.com> (raw)
In-Reply-To: <cb42c578-d037-3297-d0c2-ab107b7a838f@kernel.org>
On Fri, Sep 10, 2021 at 4:56 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> On 9/10/2021 4:40 PM, Nick Desaulniers wrote:
> > commit fad7cd3310db ("nbd: add the check to prevent overflow in
> > __nbd_ioctl()")
> >
> > raised an issue from the fallback helpers added in
> >
> > commit f0907827a8a9 ("compiler.h: enable builtin overflow checkers and add fallback code")
> >
> > Specifically, the helpers for checking whether the results of a
> > multiplication overflowed (__unsigned_mul_overflow,
> > __signed_add_overflow) use the division operator when
> > !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW. This is problematic for 64b
> > operands on 32b hosts.
>
> "hosts" -> "targets" or "architectures"?
Yes, will revise to "targets."
>
> It might be worth putting the error that Stephen found here?
Doh! Yes, in v2, I'll include the following additional context:
```
The following error is observed when building for 32b powerpc:
> ERROR: modpost: "__divdi3" [drivers/block/nbd.ko] undefined!
As Stephen Rothwell notes:
> The added check_mul_overflow() call is being passed 64 bit values.
> COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW is not set for this build (see
> include/linux/overflow.h).
```
>
> > Also, because the macro is type agnostic, it is very difficult to write
> > a similarly type generic macro that dispatches to one of:
> > * div64_s64
> > * div64_u64
> > * div_s64
> > * div_u64
> >
> > Raising the minimum supported versions allows us to remove all of the
> > fallback helpers for !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW, instead
> > dispatching the compiler builtins.
> >
> > arm64 has already raised the minimum supported GCC version to 5.1, do
> > this for all targets now. See the link below for the previous
> > discussion.
> >
> > Link: https://lore.kernel.org/all/20210909182525.372ee687@canb.auug.org.au/
> > Link: https://lore.kernel.org/lkml/CAK7LNASs6dvU6D3jL2GG3jW58fXfaj6VNOe55NJnTB8UPuk2pA@mail.gmail.com/
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1438
> > Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> > Reported-by: Nathan Chancellor <nathan@kernel.org>
> > Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
>
> > ---
> > Documentation/process/changes.rst | 2 +-
> > scripts/min-tool-version.sh | 8 +-------
> > 2 files changed, 2 insertions(+), 8 deletions(-)
> >
> > diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
> > index d3a8557b66a1..e35ab74a0f80 100644
> > --- a/Documentation/process/changes.rst
> > +++ b/Documentation/process/changes.rst
> > @@ -29,7 +29,7 @@ you probably needn't concern yourself with pcmciautils.
> > ====================== =============== ========================================
> > Program Minimal version Command to check the version
> > ====================== =============== ========================================
> > -GNU C 4.9 gcc --version
> > +GNU C 5.1 gcc --version
> > Clang/LLVM (optional) 10.0.1 clang --version
> > GNU make 3.81 make --version
> > binutils 2.23 ld -v
> > diff --git a/scripts/min-tool-version.sh b/scripts/min-tool-version.sh
> > index 319f92104f56..4edc708baa63 100755
> > --- a/scripts/min-tool-version.sh
> > +++ b/scripts/min-tool-version.sh
> > @@ -17,13 +17,7 @@ binutils)
> > echo 2.23.0
> > ;;
> > gcc)
> > - # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63293
> > - # https://lore.kernel.org/r/20210107111841.GN1551@shell.armlinux.org.uk
> > - if [ "$SRCARCH" = arm64 ]; then
> > - echo 5.1.0
> > - else
> > - echo 4.9.0
> > - fi
> > + echo 5.1.0
> > ;;
> > icc)
> > # temporary
> >
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2021-09-11 0:18 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-10 23:40 [PATCH 00/10] raise minimum GCC version to 5.1 Nick Desaulniers
2021-09-10 23:40 ` [PATCH 01/10] Documentation: raise minimum supported version of GCC " Nick Desaulniers
2021-09-10 23:55 ` Nathan Chancellor
2021-09-11 0:16 ` Nick Desaulniers [this message]
2021-09-13 16:22 ` Kees Cook
2021-09-10 23:40 ` [PATCH 02/10] compiler.h: drop fallback overflow checkers Nick Desaulniers
2021-09-11 0:04 ` Nathan Chancellor
2021-09-14 15:33 ` Nick Desaulniers
2021-09-14 16:04 ` Nathan Chancellor
2021-09-13 16:21 ` Kees Cook
2021-09-10 23:40 ` [PATCH 03/10] mm/ksm: remove old GCC 4.9+ check Nick Desaulniers
2021-09-11 0:07 ` Nathan Chancellor
2021-09-13 16:22 ` Kees Cook
2021-09-10 23:40 ` [PATCH 04/10] Kconfig.debug: drop GCC 5+ version check for DWARF5 Nick Desaulniers
2021-09-11 0:08 ` Nathan Chancellor
2021-09-13 16:23 ` Kees Cook
2021-09-10 23:40 ` [PATCH 05/10] riscv: remove Kconfig check for GCC version for ARCH_RV64I Nick Desaulniers
2021-09-11 0:09 ` Nathan Chancellor
2021-09-13 16:23 ` Kees Cook
2021-10-05 0:40 ` Palmer Dabbelt
2021-10-05 0:50 ` Kees Cook
2021-10-05 0:57 ` Palmer Dabbelt
2021-09-10 23:40 ` [PATCH 06/10] powerpc: remove GCC version check for UPD_CONSTR Nick Desaulniers
2021-09-10 23:48 ` Nathan Chancellor
2021-09-11 10:43 ` Michael Ellerman
2021-09-11 15:34 ` Christophe Leroy
2021-09-10 23:40 ` [PATCH 07/10] arm64: remove GCC version check for ARCH_SUPPORTS_INT128 Nick Desaulniers
2021-09-11 0:10 ` Nathan Chancellor
2021-09-13 16:25 ` Kees Cook
2021-09-16 13:23 ` Catalin Marinas
2021-09-10 23:40 ` [PATCH 08/10] Makefile: drop GCC < 5 -fno-var-tracking-assignments workaround Nick Desaulniers
2021-09-11 0:11 ` Nathan Chancellor
2021-09-13 16:25 ` Kees Cook
2021-09-10 23:40 ` [PATCH 09/10] compiler-gcc.h: drop checks for older GCC versions Nick Desaulniers
2021-09-11 0:12 ` Nathan Chancellor
2021-09-13 16:26 ` Kees Cook
2021-09-10 23:40 ` [PATCH 10/10] vmlinux.lds.h: remove old check for GCC 4.9 Nick Desaulniers
2021-09-10 23:50 ` Nathan Chancellor
2021-09-14 15:21 ` Nick Desaulniers
2021-09-13 16:28 ` Kees Cook
2021-09-11 2:19 ` [PATCH 00/10] raise minimum GCC version to 5.1 Kees Cook
2021-09-11 10:42 ` Michael Ellerman
2021-09-13 9:49 ` Pavel Machek
2021-09-13 16:20 ` Kees Cook
2021-09-13 11:27 ` Arnd Bergmann
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