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From: Nick Desaulniers <ndesaulniers@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Nathan Chancellor <nathan@kernel.org>,
	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,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: [PATCH 01/10] Documentation: raise minimum supported version of GCC to 5.1
Date: Fri, 10 Sep 2021 16:40:38 -0700	[thread overview]
Message-ID: <20210910234047.1019925-2-ndesaulniers@google.com> (raw)
In-Reply-To: <20210910234047.1019925-1-ndesaulniers@google.com>

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.

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>
---
 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
-- 
2.33.0.309.g3052b89438-goog


  reply	other threads:[~2021-09-10 23:41 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-10 23:40 [PATCH 00/10] raise minimum GCC version " Nick Desaulniers
2021-09-10 23:40 ` Nick Desaulniers [this message]
2021-09-10 23:55   ` [PATCH 01/10] Documentation: raise minimum supported version of GCC " Nathan Chancellor
2021-09-11  0:16     ` Nick Desaulniers
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
2021-09-10 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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