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Message-ID: <CA+icZUVXP9D+EtXrNSTUPBdYKhkQBX-+CUP6ocg4cLRpFcfP9Q@mail.gmail.com>
Date: Mon, 19 Aug 2019 20:18:44 +0200
From: Sedat Dilek <sedat.dilek@...il.com>
To: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: akpm@...ux-foundation.org, jpoimboe@...hat.com, yhs@...com,
Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
Clang-Built-Linux ML <clang-built-linux@...glegroups.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, netdev@...r.kernel.org,
bpf@...r.kernel.org
Subject: Re: [PATCH 00/16] treewide: prefer __section from compiler_attributes.h
On Mon, Aug 12, 2019 at 11:53 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> GCC unescapes escaped string section names while Clang does not. Because
> __section uses the `#` stringification operator for the section name, it
> doesn't need to be escaped.
>
> This fixes an Oops observed in distro's that use systemd and not
> net.core.bpf_jit_enable=1, when their kernels are compiled with Clang.
>
> Instead, we should:
> 1. Prefer __section(.section_name_no_quotes).
> 2. Only use __attribute__((__section(".section"))) when creating the
> section name via C preprocessor (see the definition of __define_initcall
> in arch/um/include/shared/init.h).
>
> This antipattern was found with:
> $ grep -e __section\(\" -e __section__\(\" -r
>
> See the discussions in:
> https://bugs.llvm.org/show_bug.cgi?id=42950
> https://marc.info/?l=linux-netdev&m=156412960619946&w=2
>
> Nick Desaulniers (16):
> s390/boot: fix section name escaping
> arc: prefer __section from compiler_attributes.h
> parisc: prefer __section from compiler_attributes.h
> um: prefer __section from compiler_attributes.h
> sh: prefer __section from compiler_attributes.h
> ia64: prefer __section from compiler_attributes.h
> arm: prefer __section from compiler_attributes.h
> mips: prefer __section from compiler_attributes.h
> sparc: prefer __section from compiler_attributes.h
> powerpc: prefer __section and __printf from compiler_attributes.h
> x86: prefer __section from compiler_attributes.h
> arm64: prefer __section from compiler_attributes.h
> include/asm-generic: prefer __section from compiler_attributes.h
> include/linux: prefer __section from compiler_attributes.h
> include/linux/compiler.h: remove unused KENTRY macro
> compiler_attributes.h: add note about __section
>
Hi Nick,
thanks for this patchset and the nice section names cleanup and simplification.
I have tested 5 relevant patches for my x86-64 Debian/buster system.
Patchset "for-5.3/x86-section-name-escaping" (5 patches):
compiler_attributes.h: add note about __section
include/linux/compiler.h: remove unused KENTRY macro
include/linux: prefer __section from compiler_attributes.h
include/asm-generic: prefer __section from compiler_attributes.h
x86: prefer __section from compiler_attributes.h
Toolchain: LLVM/Clang compiler and LLD linker version 9.0.0-rc2 (from
Debian/experimental)
I can boot on bare metal.
$ cat /proc/version
Linux version 5.3.0-rc5-1-amd64-cbl-asmgoto
(sedat.dilek@...il.com@...za) (clang version 9.0.0-+rc2-1~exp1
(tags/RELEASE_900/rc2)) #1~buster+dileks1 SMP 2019-08-19
I have sent by Tested-by to the single patches.
Have a nice day,
- Sedat -
> arch/arc/include/asm/linkage.h | 8 +++----
> arch/arc/include/asm/mach_desc.h | 3 +--
> arch/arm/include/asm/cache.h | 2 +-
> arch/arm/include/asm/mach/arch.h | 4 ++--
> arch/arm/include/asm/setup.h | 2 +-
> arch/arm64/include/asm/cache.h | 2 +-
> arch/arm64/kernel/smp_spin_table.c | 2 +-
> arch/ia64/include/asm/cache.h | 2 +-
> arch/mips/include/asm/cache.h | 2 +-
> arch/parisc/include/asm/cache.h | 2 +-
> arch/parisc/include/asm/ldcw.h | 2 +-
> arch/powerpc/boot/main.c | 3 +--
> arch/powerpc/boot/ps3.c | 6 ++----
> arch/powerpc/include/asm/cache.h | 2 +-
> arch/powerpc/kernel/btext.c | 2 +-
> arch/s390/boot/startup.c | 2 +-
> arch/sh/include/asm/cache.h | 2 +-
> arch/sparc/include/asm/cache.h | 2 +-
> arch/sparc/kernel/btext.c | 2 +-
> arch/um/kernel/um_arch.c | 6 +++---
> arch/x86/include/asm/cache.h | 2 +-
> arch/x86/include/asm/intel-mid.h | 2 +-
> arch/x86/include/asm/iommu_table.h | 5 ++---
> arch/x86/include/asm/irqflags.h | 2 +-
> arch/x86/include/asm/mem_encrypt.h | 2 +-
> arch/x86/kernel/cpu/cpu.h | 3 +--
> include/asm-generic/error-injection.h | 2 +-
> include/asm-generic/kprobes.h | 5 ++---
> include/linux/cache.h | 6 +++---
> include/linux/compiler.h | 31 ++++-----------------------
> include/linux/compiler_attributes.h | 10 +++++++++
> include/linux/cpu.h | 2 +-
> include/linux/export.h | 2 +-
> include/linux/init_task.h | 4 ++--
> include/linux/interrupt.h | 5 ++---
> include/linux/sched/debug.h | 2 +-
> include/linux/srcutree.h | 2 +-
> 37 files changed, 62 insertions(+), 83 deletions(-)
>
> --
> 2.23.0.rc1.153.gdeed80330f-goog
>
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