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From: Kees Cook <keescook@chromium.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Ard Biesheuvel <ardb@kernel.org>, Will Deacon <will@kernel.org>,
	Dave Martin <Dave.Martin@arm.com>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Peter Collingbourne <pcc@google.com>,
	James Morse <james.morse@arm.com>, Borislav Petkov <bp@suse.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Russell King <linux@armlinux.org.uk>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>, X86 ML <x86@kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	linux-efi <linux-efi@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v4 05/17] ctype: Work around Clang -mbranch-protection=none bug
Date: Mon, 29 Jun 2020 11:37:16 -0700	[thread overview]
Message-ID: <202006291136.E6DF8242@keescook> (raw)
In-Reply-To: <CAKwvOd=DMfmvfiEX7KDPLs75SbNz+LAGSwC3V_=LgGH3kjtE=g@mail.gmail.com>

On Mon, Jun 29, 2020 at 11:02:51AM -0700, Nick Desaulniers wrote:
> This is definitely better than the empty function.  Though a patch is
> posted for fixing this in LLVM. Assuming that lands before this, we
> might not actually need this workaround?
> 
> arch/arm64/Kconfig
> 1625 config ARM64_BTI_KERNEL
> ...
> 1633   # https://reviews.llvm.org/rGb8ae3fdfa579dbf366b1bb1cbfdbf8c51db7fa55
> 1634   depends on !CC_IS_CLANG || CLANG_VERSION >= 100001
> 
> So if Daniel's patch lands AND is backported into the clang 10.0.1
> release, then we might not need to carry this workaround?  Either way,

True, though as I mentioned in the review, I don't think it's quite
right -- the warning getting removed is actually quite valuable.

> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

Thanks!

-- 
Kees Cook

WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Ard Biesheuvel <ardb@kernel.org>, Will Deacon <will@kernel.org>,
	Dave Martin <Dave.Martin@arm.com>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Peter Collingbourne <pcc@google.com>,
	James Morse <james.morse@arm.com>, Borislav Petkov <bp@suse.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Russell King <linux@armlinux.org.uk>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>, X86 ML <x86@kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	linux-efi <linux-efi@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Daniel Kiss <daniel.kiss@arm.com>
Subject: Re: [PATCH v4 05/17] ctype: Work around Clang -mbranch-protection=none bug
Date: Mon, 29 Jun 2020 11:37:16 -0700	[thread overview]
Message-ID: <202006291136.E6DF8242@keescook> (raw)
Message-ID: <20200629183716.1iXAxw4HPcvdYaX8Gw9yKwGGLS3asaVFATTWLDQYJLs@z> (raw)
In-Reply-To: <CAKwvOd=DMfmvfiEX7KDPLs75SbNz+LAGSwC3V_=LgGH3kjtE=g@mail.gmail.com>

On Mon, Jun 29, 2020 at 11:02:51AM -0700, Nick Desaulniers wrote:
> This is definitely better than the empty function.  Though a patch is
> posted for fixing this in LLVM. Assuming that lands before this, we
> might not actually need this workaround?
> 
> arch/arm64/Kconfig
> 1625 config ARM64_BTI_KERNEL
> ...
> 1633   # https://reviews.llvm.org/rGb8ae3fdfa579dbf366b1bb1cbfdbf8c51db7fa55
> 1634   depends on !CC_IS_CLANG || CLANG_VERSION >= 100001
> 
> So if Daniel's patch lands AND is backported into the clang 10.0.1
> release, then we might not need to carry this workaround?  Either way,

True, though as I mentioned in the review, I don't think it's quite
right -- the warning getting removed is actually quite valuable.

> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

Thanks!

-- 
Kees Cook

  parent reply	other threads:[~2020-06-29 18:42 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-29  6:18 [PATCH v4 00/17] Warn on orphan section placement Kees Cook
2020-06-29  6:18 ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 01/17] vmlinux.lds.h: Add .gnu.version* to DISCARDS Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 02/17] vmlinux.lds.h: Avoid KASAN and KCSAN's unwanted sections Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 03/17] vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 04/17] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to ELF_DETAILS Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 05/17] ctype: Work around Clang -mbranch-protection=none bug Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  8:15   ` Ard Biesheuvel
2020-06-29  8:15     ` Ard Biesheuvel
2020-06-29 14:43     ` Kees Cook
2020-06-29 14:43       ` Kees Cook
2020-06-29 15:06     ` Kees Cook
2020-06-29 15:06       ` Kees Cook
2020-06-29 15:08       ` Ard Biesheuvel
2020-06-29 15:08         ` Ard Biesheuvel
2020-06-29 15:16         ` Kees Cook
2020-06-29 15:16           ` Kees Cook
2020-06-29 18:02       ` Nick Desaulniers
2020-06-29 18:02         ` Nick Desaulniers
2020-06-29 18:37         ` Kees Cook [this message]
2020-06-29 18:37           ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 06/17] efi/libstub: Disable -mbranch-protection Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 07/17] arm64/build: Use common DISCARDS in linker script Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 08/17] arm64/mm: Remove needless section quotes Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29 19:53   ` Nick Desaulniers
2020-06-29 19:53     ` Nick Desaulniers
2020-06-29 20:03     ` Joe Perches
2020-06-29 20:03       ` Joe Perches
2020-06-29 20:29       ` Nick Desaulniers
2020-06-29 20:29         ` Nick Desaulniers
2020-06-29 20:04     ` Kees Cook
2020-06-29 20:04       ` Kees Cook
2020-06-29 20:54       ` Arvind Sankar
2020-06-29 20:54         ` Arvind Sankar
2020-06-29 21:06         ` Arvind Sankar
2020-06-29 21:06           ` Arvind Sankar
2020-06-29  6:18 ` [PATCH v4 09/17] arm64/build: Remove .eh_frame* sections due to unwind tables Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 10/17] arm64/kernel: Remove needless Call Frame Information annotations Kees Cook
2020-06-29  6:18 ` [PATCH v4 11/17] arm64/build: Warn on orphan section placement Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 12/17] arm/build: Refactor linker script headers Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 13/17] arm/build: Explicitly keep .ARM.attributes sections Kees Cook
2020-06-29  6:18 ` [PATCH v4 14/17] arm/build: Warn on orphan section placement Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29 15:54   ` Arvind Sankar
2020-06-29 15:54     ` Arvind Sankar
2020-06-29 18:07     ` Russell King - ARM Linux admin
2020-06-29 18:07       ` Russell King - ARM Linux admin
2020-06-29 18:15       ` Arvind Sankar
2020-06-29 18:15         ` Arvind Sankar
2020-06-29 19:03         ` Russell King - ARM Linux admin
2020-06-29 19:47   ` Nick Desaulniers
2020-06-29 19:47     ` Nick Desaulniers
2020-06-29  6:18 ` [PATCH v4 15/17] arm/boot: " Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-06-29  6:18 ` [PATCH v4 16/17] x86/build: " Kees Cook
2020-06-29  6:18 ` [PATCH v4 17/17] x86/boot: " Kees Cook
2020-06-29  6:18   ` Kees Cook
2020-08-21 16:02 ` [PATCH v4 00/17] " Will Deacon
2020-08-21 17:36   ` Kees Cook

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