Messages in this thread Patch in this message | | | Date | Thu, 27 Aug 2020 21:02:17 +0200 | From | Marco Elver <> | Subject | Re: [PATCH] compiler-clang: add build check for clang 10.0.1 |
| |
On Wed, Aug 26, 2020 at 02:42PM -0700, Nathan Chancellor wrote: > On Wed, Aug 26, 2020 at 01:14:19PM -0700, Nick Desaulniers wrote: > > During Plumbers 2020, we voted to just support the latest release of > > Clang for now. Add a compile time check for this. > > > > Older clang's may work, but we will likely drop workarounds for older > > versions. > > I think this part of the commit message is a little wishy-washy. If we > are breaking the build for clang < 10.0.1, we are not saying "may work", > we are saying "won't work". Because of this, we should take the > opportunity to clean up behind us and revert/remove parts of: > > 87e0d4f0f37f ("kbuild: disable clang's default use of -fmerge-all-constants") > b0fe66cf0950 ("ARM: 8905/1: Emit __gnu_mcount_nc when using Clang 10.0.0 or newer") > b9249cba25a5 ("arm64: bti: Require clang >= 10.0.1 for in-kernel BTI support") > 3acf4be23528 ("arm64: vdso: Fix compilation with clang older than 8") > > This could be a series or a part of this commit, I do not have a > strong preference. If we are not going to clean up behind us, this > should be a warning and not an error.
There are also some other documentation that would go stale. We probably have to change KASAN docs to look something like the below.
I wish we could also remove the "but detection of out-of-bounds accesses for global variables is only supported since Clang 11", but Clang 10 is a vast improvement so I'm not complaining. :-)
Acked-by: Marco Elver <elver@google.com>
Thanks, -- Marco
------ >8 ------
From 13d03b55c69dec813d94c1481dcb294971f164ef Mon Sep 17 00:00:00 2001 From: Marco Elver <elver@google.com> Date: Thu, 27 Aug 2020 20:56:34 +0200 Subject: [PATCH] kasan: Remove mentions of unsupported Clang versions
Since the kernel now requires at least Clang 10.0.1, remove any mention of old Clang versions and simplify the documentation.
Signed-off-by: Marco Elver <elver@google.com> --- Documentation/dev-tools/kasan.rst | 4 ++-- lib/Kconfig.kasan | 9 ++++----- 2 files changed, 6 insertions(+), 7 deletions(-)
diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index 38fd5681fade..4abc84b1798c 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -13,10 +13,10 @@ KASAN uses compile-time instrumentation to insert validity checks before every memory access, and therefore requires a compiler version that supports that. Generic KASAN is supported in both GCC and Clang. With GCC it requires version -8.3.0 or later. With Clang it requires version 7.0.0 or later, but detection of +8.3.0 or later. Any supported Clang version is compatible, but detection of out-of-bounds accesses for global variables is only supported since Clang 11. -Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later. +Tag-based KASAN is only supported in Clang. Currently generic KASAN is supported for the x86_64, arm64, xtensa, s390 and riscv architectures, and tag-based KASAN is supported only for arm64. diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan index 047b53dbfd58..033a5bc67ac4 100644 --- a/lib/Kconfig.kasan +++ b/lib/Kconfig.kasan @@ -54,9 +54,9 @@ config KASAN_GENERIC Enables generic KASAN mode. This mode is supported in both GCC and Clang. With GCC it requires - version 8.3.0 or later. With Clang it requires version 7.0.0 or - later, but detection of out-of-bounds accesses for global variables - is supported only since Clang 11. + version 8.3.0 or later. Any supported Clang version is compatible, + but detection of out-of-bounds accesses for global variables is + supported only since Clang 11. This mode consumes about 1/8th of available memory at kernel start and introduces an overhead of ~x1.5 for the rest of the allocations. @@ -78,8 +78,7 @@ config KASAN_SW_TAGS Enables software tag-based KASAN mode. This mode requires Top Byte Ignore support by the CPU and therefore - is only supported for arm64. This mode requires Clang version 7.0.0 - or later. + is only supported for arm64. This mode requires Clang. This mode consumes about 1/16th of available memory at kernel start and introduces an overhead of ~20% for the rest of the allocations. -- 2.28.0.297.g1956fa8f8d-goog
| |