From: Fangrui Song <maskray@google.com>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Nick Desaulniers <ndesaulniers@google.com>,
Dmitry Golovin <dima@golovin.in>,
clang-built-linux@googlegroups.com,
Ard Biesheuvel <ardb@kernel.org>,
Masahiro Yamada <masahiroy@kernel.org>,
Daniel Kiper <daniel.kiper@oracle.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] x86/boot: Add .text.startup to setup.ld
Date: Sun, 24 May 2020 15:13:26 -0700 [thread overview]
Message-ID: <20200524221326.zo6zthdqecm2ke5t@google.com> (raw)
In-Reply-To: <20200524212816.243139-2-nivedita@alum.mit.edu>
On 2020-05-24, Arvind Sankar wrote:
>gcc puts the main function into .text.startup when compiled with -Os (or
>-O2). This results in arch/x86/boot/main.c having a .text.startup
>section which is currently not included explicitly in the linker script
>setup.ld in the same directory.
>
>The BFD linker places this orphan section immediately after .text, so
>this still works. However, LLD git, since [1], is choosing to place it
>immediately after the .bstext section instead (this is the first code
>section). This plays havoc with the section layout that setup.elf
>requires to create the setup header, for eg on 64-bit:
>
> LD arch/x86/boot/setup.elf
> ld.lld: error: section .text.startup file range overlaps with .header
> >>> .text.startup range is [0x200040, 0x2001FE]
> >>> .header range is [0x2001EF, 0x20026B]
>
> ld.lld: error: section .header file range overlaps with .bsdata
> >>> .header range is [0x2001EF, 0x20026B]
> >>> .bsdata range is [0x2001FF, 0x200398]
>
> ld.lld: error: section .bsdata file range overlaps with .entrytext
> >>> .bsdata range is [0x2001FF, 0x200398]
> >>> .entrytext range is [0x20026C, 0x2002D3]
>
> ld.lld: error: section .text.startup virtual address range overlaps
> with .header
> >>> .text.startup range is [0x40, 0x1FE]
> >>> .header range is [0x1EF, 0x26B]
>
> ld.lld: error: section .header virtual address range overlaps with
> .bsdata
> >>> .header range is [0x1EF, 0x26B]
> >>> .bsdata range is [0x1FF, 0x398]
>
> ld.lld: error: section .bsdata virtual address range overlaps with
> .entrytext
> >>> .bsdata range is [0x1FF, 0x398]
> >>> .entrytext range is [0x26C, 0x2D3]
>
> ld.lld: error: section .text.startup load address range overlaps with
> .header
> >>> .text.startup range is [0x40, 0x1FE]
> >>> .header range is [0x1EF, 0x26B]
>
> ld.lld: error: section .header load address range overlaps with
> .bsdata
> >>> .header range is [0x1EF, 0x26B]
> >>> .bsdata range is [0x1FF, 0x398]
>
> ld.lld: error: section .bsdata load address range overlaps with
> .entrytext
> >>> .bsdata range is [0x1FF, 0x398]
> >>> .entrytext range is [0x26C, 0x2D3]
>
>Explicitly pull .text.startup into the .text output section to avoid
>this.
>
>[1] https://reviews.llvm.org/D75225
>
>Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
>Reviewed-by: Fangrui Song <maskray@google.com>
>---
> arch/x86/boot/setup.ld | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
>index 24c95522f231..ed60abcdb089 100644
>--- a/arch/x86/boot/setup.ld
>+++ b/arch/x86/boot/setup.ld
>@@ -20,7 +20,7 @@ SECTIONS
> .initdata : { *(.initdata) }
> __end_init = .;
>
>- .text : { *(.text) }
>+ .text : { *(.text.startup) *(.text) }
> .text32 : { *(.text32) }
>
> . = ALIGN(16);
>--
>2.26.2
Should .text.startup* be used instead? If -ffunction-sections is used,
// a.c
int main() {}
gcc -O2 a.c # .text.startup
gcc -Os a.c # .text.startup
gcc -O2 -ffunction-sections a.c # .text.startup.main
gcc -Os -ffunction-sections a.c # .text.startup.main
-----
In case anyone wants to CC a GCC dev for the citation that
main compiles to `.text.startup` in -Os or -O2 mode, I have a small request
that `.text.startup.` probably makes more sense. See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95095
I made an llvm change recently https://reviews.llvm.org/D79600
next prev parent reply other threads:[~2020-05-24 22:13 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-01 8:42 [PATCH] x86/boot: allow a relocatable kernel to be linked with lld Dmitry Golovin
2020-05-02 3:43 ` Nathan Chancellor
2020-05-15 18:50 ` Borislav Petkov
[not found] ` <602331589572661@mail.yandex.ru>
2020-05-17 19:44 ` Fangrui Song
2020-05-17 20:25 ` Arvind Sankar
2020-05-18 19:10 ` Nick Desaulniers
2020-05-24 21:28 ` [PATCH 0/4] x86/boot: Remove runtime relocations from compressed kernel Arvind Sankar
2020-05-25 7:10 ` Ard Biesheuvel
2020-05-25 22:59 ` [PATCH v2 " Arvind Sankar
2020-05-26 12:29 ` Sedat Dilek
2020-05-26 12:30 ` Ard Biesheuvel
2020-05-26 12:33 ` Sedat Dilek
2020-05-26 12:44 ` Sedat Dilek
2020-05-26 14:47 ` Arvind Sankar
2020-05-26 14:50 ` Sedat Dilek
2020-05-26 15:36 ` Arvind Sankar
2020-05-26 15:38 ` Sedat Dilek
2020-05-27 6:26 ` Sedat Dilek
2020-05-26 14:48 ` Sedat Dilek
2020-05-26 14:55 ` Sedat Dilek
2020-05-26 15:07 ` Sedat Dilek
2020-05-26 15:31 ` Arvind Sankar
2020-05-27 6:24 ` Sedat Dilek
2020-05-26 16:18 ` Sedat Dilek
2020-05-25 22:59 ` [PATCH v2 1/4] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-05-25 22:59 ` [PATCH v2 2/4] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-05-25 22:59 ` [PATCH v2 3/4] x86/boot: Remove runtime relocations from head_{32,64}.S Arvind Sankar
2020-05-25 22:59 ` [PATCH v2 4/4] x86/boot: Check that there are no runtime relocations Arvind Sankar
2020-05-26 6:11 ` Ard Biesheuvel
2020-05-26 15:16 ` Arvind Sankar
2020-05-26 17:13 ` Fangrui Song
2020-05-26 19:14 ` Arvind Sankar
2020-08-06 11:19 ` Andy Shevchenko
2020-08-06 16:12 ` Arvind Sankar
2020-05-26 0:37 ` [PATCH 0/4] x86/boot: Remove runtime relocations from compressed kernel Fangrui Song
2020-05-24 21:28 ` [PATCH 1/4] x86/boot: Add .text.startup to setup.ld Arvind Sankar
2020-05-24 22:13 ` Fangrui Song [this message]
2020-05-24 23:00 ` Arvind Sankar
2020-05-24 23:49 ` Fangrui Song
2020-05-24 22:48 ` Brian Gerst
2020-05-24 21:28 ` [PATCH 2/4] x86/boot: Remove runtime relocations from .head.text code Arvind Sankar
2020-05-24 22:53 ` Fangrui Song
2020-05-24 23:44 ` Arvind Sankar
2020-05-25 0:55 ` Fangrui Song
2020-05-24 21:28 ` [PATCH 3/4] x86/boot: Remove runtime relocations from head_{32,64}.S Arvind Sankar
2020-05-24 23:22 ` Fangrui Song
2020-05-24 23:58 ` Arvind Sankar
2020-05-24 21:28 ` [PATCH 4/4] x86/boot: Check that there are no runtime relocations Arvind Sankar
2020-05-24 23:36 ` Fangrui Song
2020-05-24 23:57 ` Arvind Sankar
2020-05-25 6:10 ` Ard Biesheuvel
2020-05-25 16:26 ` Fangrui Song
2020-05-25 19:22 ` Arvind Sankar
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