From: Fangrui Song <maskray@google.com>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Michael Matz <matz@suse.de>, Borislav Petkov <bp@alien8.de>,
Nathan Chancellor <natechancellor@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH 2/2] x86/boot/compressed: Remove unnecessary sections from bzImage
Date: Mon, 24 Feb 2020 14:50:59 -0800 [thread overview]
Message-ID: <20200224225059.2scjklfi4g7wwdkp@google.com> (raw)
In-Reply-To: <20200224224343.GA572699@rani.riverdale.lan>
On 2020-02-24, Arvind Sankar wrote:
>On Mon, Feb 24, 2020 at 02:17:03PM -0800, Fangrui Song wrote:
>> On 2020-02-24, Arvind Sankar wrote:
>> >On Mon, Feb 24, 2020 at 01:28:28PM -0800, Fangrui Song wrote:
>> >> Hi Michael, please see my other reply on this thread: https://lkml.org/lkml/2020/2/24/47
>> >>
>> >> Synthesized sections can be matched as well. For example, SECTIONS { .pltfoo : { *(.plt) }} can rename the output section .plt to .pltfoo
>> >> It seems that in GNU ld, the synthesized section is associated with the
>> >> original object file, so it can be written as:
>> >>
>> >> SECTIONS { .pltfoo : { a.o(.plt) }}
>> >>
>> >> In lld, you need a wildcard to match the synthesized section *(.plt)
>> >>
>> >> .rela.dyn is another example.
>> >>
>> >
>> >With the BFD toolchain, file matching doesn't actually seem to work at
>> >least for .rela.dyn. I've tried playing around with it in the past and
>> >if you try to use file-matching to capture relocations from a particular
>> >input file, it just doesn't work sensibly.
>>
>> I think most things are working in GNU ld...
>>
>> /* a.x */
>> SECTIONS {
>> .rela.pltfoo : { a.o(.rela.plt) } /* *(.rela.plt) with lld */
>> .rela.dynfoo : { a.o(.rela.data) } /* *(.rela.dyn) with lld */
>> }
>
>The file matching doesn't do anything sensible. If you split your .data
>section out into b.s, and update the linker script so it filters for
>b.o(.rela.data), .rela.dynfoo doesn't get created, instead the default
>.rela.dyn will contains the .data section relocation. If you keep the
>filter as a.o(.rela.data), you get .rela.dynfoo, even though a.o doesn't
>actually contain any .rela.data section any more.
I raised the examples to support my viewpoint "synthesized sections can
be matched, as well as input sections."
If there is really a need (rare, not recommended) to rename output
sections only consisting of synthesized sections (e.g. .plt .rela.dyn),
for linker portability, it is better using a wildcard for the input
filename pattern.
As another example, SECTIONS { /DISCARD/ : { *(.rela.*) } } discards synthesized .rela.*
>>
>> % cat <<e > a.s
>> .globl foo
>> foo:
>> call bar
>> .data
>> .quad quz
>> e
>> % as a.s -o a.o
>> % ld.bfd -T a.x a.o -shared -o a.so
next prev parent reply other threads:[~2020-02-24 22:51 UTC|newest]
Thread overview: 115+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-09 15:02 [PATCH 1/2] x86/boot/compressed/64: Remove .bss/.pgtable from bzImage Arvind Sankar
2020-01-09 15:02 ` [PATCH 2/2] x86/boot/compressed: Remove unnecessary sections " Arvind Sankar
2020-02-06 11:44 ` Kees Cook
2020-02-19 16:55 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar
2020-02-22 5:08 ` [PATCH 2/2] " Nathan Chancellor
2020-02-22 6:55 ` Borislav Petkov
2020-02-22 7:02 ` Nathan Chancellor
2020-02-22 7:21 ` Fangrui Song
2020-02-22 7:42 ` Nathan Chancellor
2020-02-22 15:37 ` Arvind Sankar
2020-02-22 16:44 ` Arvind Sankar
2020-02-22 17:18 ` [PATCH] x86/boot/compressed: Fix compressed kernel linking with lld Arvind Sankar
2020-02-22 18:14 ` Nathan Chancellor
2020-02-22 18:58 ` Fangrui Song
2020-02-22 20:17 ` Arvind Sankar
2020-02-22 21:01 ` Fangrui Song
2020-02-22 23:33 ` Nick Desaulniers
2020-02-22 23:57 ` Arvind Sankar
2020-02-23 19:37 ` [PATCH 0/2] Stop generating .eh_frame sections Arvind Sankar
2020-02-24 4:15 ` Nathan Chancellor
2020-02-24 20:49 ` Nick Desaulniers
2020-02-24 21:53 ` Arvind Sankar
2020-02-24 22:01 ` Nick Desaulniers
2020-02-23 19:37 ` [PATCH 1/2] arch/x86: Use -fno-asynchronous-unwind-tables to suppress " Arvind Sankar
2020-02-24 20:33 ` Nick Desaulniers
2020-02-24 21:05 ` Arvind Sankar
2020-02-24 21:12 ` Fangrui Song
2020-02-24 21:17 ` Nick Desaulniers
2020-02-24 21:22 ` Nick Desaulniers
2020-02-23 19:37 ` [PATCH 2/2] arch/x86: Drop unneeded linker script discard of .eh_frame Arvind Sankar
2020-02-24 20:45 ` Nick Desaulniers
2020-02-24 21:33 ` Arvind Sankar
2020-02-24 21:58 ` Nick Desaulniers
2020-02-24 23:21 ` [PATCH v2 0/2] Stop generating .eh_frame sections Arvind Sankar
2020-02-24 23:21 ` [PATCH v2 1/2] arch/x86: Use -fno-asynchronous-unwind-tables to suppress " Arvind Sankar
2020-02-24 23:28 ` Nathan Chancellor
2020-02-24 23:30 ` Nick Desaulniers
2020-02-25 4:10 ` Kees Cook
2020-02-25 16:53 ` [tip: x86/boot] x86/*/Makefile: " tip-bot2 for Arvind Sankar
2020-02-24 23:21 ` [PATCH v2 2/2] arch/x86: Drop unneeded linker script discard of .eh_frame Arvind Sankar
2020-02-24 23:28 ` Nathan Chancellor
2020-02-24 23:33 ` Nick Desaulniers
2020-02-25 4:11 ` Kees Cook
2020-02-25 16:53 ` [tip: x86/boot] x86/vmlinux: " tip-bot2 for Arvind Sankar
2020-02-23 22:00 ` [PATCH] x86/boot/compressed: Fix compressed kernel linking with lld Kees Cook
2020-02-24 6:06 ` Fangrui Song
2020-02-22 17:29 ` [PATCH 2/2] x86/boot/compressed: Remove unnecessary sections from bzImage Borislav Petkov
2020-02-22 17:53 ` Arvind Sankar
2020-02-22 7:42 ` Borislav Petkov
2020-02-22 16:22 ` Arvind Sankar
2020-02-22 23:20 ` Nick Desaulniers
2020-02-24 13:28 ` Michael Matz
2020-02-24 20:51 ` Nick Desaulniers
2020-02-24 21:28 ` Fangrui Song
2020-02-24 21:48 ` Arvind Sankar
2020-02-24 22:17 ` Fangrui Song
2020-02-24 22:43 ` Arvind Sankar
2020-02-24 22:50 ` Fangrui Song [this message]
2020-02-24 23:08 ` Arvind Sankar
2020-02-25 5:35 ` --orphan-handling=warn (was Re: [PATCH 2/2] x86/boot/compressed: Remove unnecessary sections) " Kees Cook
2020-02-25 16:42 ` --orphan-handling=warn Arvind Sankar
2020-02-25 18:29 ` --orphan-handling=warn Arvind Sankar
2020-02-25 19:42 ` --orphan-handling=warn Kees Cook
2020-02-25 20:37 ` --orphan-handling=warn Nick Desaulniers
2020-02-25 22:02 ` --orphan-handling=warn Kees Cook
2020-02-26 1:56 ` --orphan-handling=warn Fangrui Song
2020-02-26 5:35 ` --orphan-handling=warn Kees Cook
2020-02-26 19:11 ` --orphan-handling=warn Kristen Carlson Accardi
2020-02-26 19:26 ` --orphan-handling=warn Nick Desaulniers
2020-02-24 11:37 ` [tip: x86/boot] x86/boot/compressed: Remove .eh_frame section from bzImage tip-bot2 for Arvind Sankar
2020-02-24 16:41 ` Arvind Sankar
2020-02-24 17:16 ` Borislav Petkov
2020-02-24 17:28 ` Arvind Sankar
2020-02-05 16:29 ` [PATCH 1/2] x86/boot/compressed/64: Remove .bss/.pgtable " Arvind Sankar
2020-02-18 18:03 ` Arvind Sankar
2020-02-19 12:09 ` Borislav Petkov
2020-02-19 17:57 ` Arvind Sankar
2020-02-19 18:22 ` Borislav Petkov
2020-02-19 19:06 ` Arvind Sankar
2020-02-06 11:18 ` Kees Cook
2020-02-19 16:55 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar
2020-04-05 15:42 ` [PATCH 1/2] " Sergey Shatunov
2020-04-05 23:18 ` Arvind Sankar
2020-04-06 0:00 ` Sergey Shatunov
2020-04-06 3:51 ` Arvind Sankar
2020-04-06 7:32 ` Ard Biesheuvel
2020-04-06 8:47 ` Borislav Petkov
2020-04-06 9:11 ` Ard Biesheuvel
2020-04-06 11:20 ` Borislav Petkov
2020-04-06 13:22 ` Arvind Sankar
2020-04-06 13:29 ` Ard Biesheuvel
2020-04-06 16:01 ` Arvind Sankar
2020-04-06 16:22 ` Ard Biesheuvel
2020-04-06 16:52 ` Arvind Sankar
2020-04-06 16:59 ` Ard Biesheuvel
2020-04-06 18:06 ` [PATCH 1/2] efi/x86: Move efi stub globals from .bss to .data Arvind Sankar
2020-04-06 18:06 ` [PATCH 2/2] efi/x86: Always relocate the kernel for EFI handover entry Arvind Sankar
2020-04-14 8:20 ` [tip: efi/urgent] " tip-bot2 for Arvind Sankar
2020-04-06 18:29 ` [PATCH 1/2] efi/x86: Move efi stub globals from .bss to .data Ard Biesheuvel
2020-04-08 7:43 ` Dave Young
2020-04-08 7:49 ` Ard Biesheuvel
2020-04-09 14:39 ` Arvind Sankar
2020-04-09 14:47 ` Ard Biesheuvel
2020-04-09 16:35 ` Arvind Sankar
2020-04-10 14:47 ` Arvind Sankar
2020-04-10 15:26 ` Ard Biesheuvel
2020-04-14 14:57 ` Daniel Kiper
2020-04-10 11:26 ` Thomas Meyer
2020-04-10 14:38 ` Arvind Sankar
2020-04-11 8:50 ` Thomas Meyer
2020-04-14 8:20 ` [tip: efi/urgent] " tip-bot2 for Arvind Sankar
2020-04-06 17:21 ` [PATCH 1/2] x86/boot/compressed/64: Remove .bss/.pgtable from bzImage Borislav Petkov
2020-04-06 8:44 ` Ard Biesheuvel
2020-04-06 12:36 ` Sergey Shatunov
2020-04-06 13:20 ` Ard Biesheuvel
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