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From: Arvind Sankar <nivedita@alum.mit.edu>
To: Kees Cook <keescook@chromium.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	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>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	linux-arch <linux-arch@vger.kernel.org>,
	linux-efi <linux-efi@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Joe Perches <joe@perches.com>
Subject: Re: [PATCH v4 08/17] arm64/mm: Remove needless section quotes
Date: Mon, 29 Jun 2020 16:54:48 -0400
Message-ID: <20200629205448.GA1474367@rani.riverdale.lan> (raw)
In-Reply-To: <202006291301.46FEF3B7@keescook>

On Mon, Jun 29, 2020 at 01:04:31PM -0700, Kees Cook wrote:
> On Mon, Jun 29, 2020 at 12:53:47PM -0700, Nick Desaulniers wrote:
> > On Sun, Jun 28, 2020 at 11:18 PM Kees Cook <keescook@chromium.org> wrote:
> > >
> > > Fix a case of needless quotes in __section(), which Clang doesn't like.
> > >
> > > Acked-by: Will Deacon <will@kernel.org>
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > 
> > Yep, I remember bugs from this.  Probably should scan the kernel for
> > other instances of this.  +Joe for checkpatch.pl validation.
> 
> I think the others are safe because they're in macros:

Why does that make it safe -- the commit msg is a bit sparse, but I
assume the problem is that it generates
	__attribute__((__section__("\".foo\"")))
from
	__section(".foo")
after preprocessing, and clang keeps the quotes in the section name when
generating assembly, while gcc appears to strip them off.

It does that even if nested in another macro, no?

> 
> $ git grep -4 '__section("'
> include/linux/compiler.h-# define KENTRY(sym)                                           \

Am I missing something, or is KENTRY unused in the tree?

> include/linux/compiler.h-       extern typeof(sym) sym;                                 \
> include/linux/compiler.h-       static const unsigned long __kentry_##sym               \
> include/linux/compiler.h-       __used                                                  \
> include/linux/compiler.h:       __section("___kentry" "+" #sym )                        \
> include/linux/compiler.h-       = (unsigned long)&sym;
> --
> include/linux/export.h-#define __ksym_marker(sym)       \
> include/linux/export.h: static int __ksym_marker_##sym[0] __section(".discard.ksym") __used
> --
> include/linux/srcutree.h-# define __DEFINE_SRCU(name, is_static)                                \
> include/linux/srcutree.h-       is_static struct srcu_struct name;                              \
> include/linux/srcutree.h-       struct srcu_struct * const __srcu_struct_##name                 \
> include/linux/srcutree.h:               __section("___srcu_struct_ptrs") = &name
> 
> 
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> 
> Thanks!
> 
> -- 
> Kees Cook

  reply index

Thread overview: 36+ 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 ` [PATCH v4 01/17] vmlinux.lds.h: Add .gnu.version* to DISCARDS 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 ` [PATCH v4 03/17] vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG 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 ` [PATCH v4 05/17] ctype: Work around Clang -mbranch-protection=none bug Kees Cook
2020-06-29  8:15   ` Ard Biesheuvel
2020-06-29 14:43     ` Kees Cook
2020-06-29 15:06     ` Kees Cook
2020-06-29 15:08       ` Ard Biesheuvel
2020-06-29 15:16         ` Kees Cook
2020-06-29 18:02       ` Nick Desaulniers
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 ` [PATCH v4 07/17] arm64/build: Use common DISCARDS in linker script Kees Cook
2020-06-29  6:18 ` [PATCH v4 08/17] arm64/mm: Remove needless section quotes Kees Cook
2020-06-29 19:53   ` Nick Desaulniers
2020-06-29 20:03     ` Joe Perches
2020-06-29 20:29       ` Nick Desaulniers
2020-06-29 20:04     ` Kees Cook
2020-06-29 20:54       ` Arvind Sankar [this message]
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 ` [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 ` [PATCH v4 12/17] arm/build: Refactor linker script headers 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 15:54   ` Arvind Sankar
2020-06-29 18:07     ` Russell King - ARM Linux admin
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  6:18 ` [PATCH v4 15/17] arm/boot: " 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

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