arm64 module: remove (NOLOAD)

[PATCH] arm64 module: remove (NOLOAD)

Posted by Fangrui Song 4 years, 4 months ago

On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
inappropriate for .plt and .text.* sections which are always
SHT_PROGBITS.

In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
and (NOLOAD) will be essentially ignored. In ld.lld, since
https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
customize the output section type"), ld.lld will report a `section type
mismatch` error. Just remove (NOLOAD) to fix the error.

[1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
section should be marked as not loadable" on
https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
outdated for ELF.
---
 arch/arm64/include/asm/module.lds.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
index a11ccadd47d2..094701ec5500 100644
--- a/arch/arm64/include/asm/module.lds.h
+++ b/arch/arm64/include/asm/module.lds.h
@@ -1,8 +1,8 @@
 SECTIONS {
 #ifdef CONFIG_ARM64_MODULE_PLTS
-	.plt 0 (NOLOAD) : { BYTE(0) }
-	.init.plt 0 (NOLOAD) : { BYTE(0) }
-	.text.ftrace_trampoline 0 (NOLOAD) : { BYTE(0) }
+	.plt 0 : { BYTE(0) }
+	.init.plt 0 : { BYTE(0) }
+	.text.ftrace_trampoline 0 : { BYTE(0) }
 #endif
 
 #ifdef CONFIG_KASAN_SW_TAGS
-- 
2.35.1.265.g69c8d7142f-goog

Re: [PATCH] arm64 module: remove (NOLOAD)

Posted by Ard Biesheuvel 4 years, 4 months ago

On Fri, 18 Feb 2022 at 09:12, Fangrui Song <maskray@google.com> wrote:
>
> On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
> inappropriate for .plt and .text.* sections which are always
> SHT_PROGBITS.
>
> In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
> and (NOLOAD) will be essentially ignored. In ld.lld, since
> https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
> customize the output section type"), ld.lld will report a `section type
> mismatch` error. Just remove (NOLOAD) to fix the error.
>
> [1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
> section should be marked as not loadable" on
> https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
> outdated for ELF.

This patch lacks a SOB line.

With one added,

Acked-by: Ard Biesheuvel <ardb@kernel.org>

> ---
>  arch/arm64/include/asm/module.lds.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
> index a11ccadd47d2..094701ec5500 100644
> --- a/arch/arm64/include/asm/module.lds.h
> +++ b/arch/arm64/include/asm/module.lds.h
> @@ -1,8 +1,8 @@
>  SECTIONS {
>  #ifdef CONFIG_ARM64_MODULE_PLTS
> -       .plt 0 (NOLOAD) : { BYTE(0) }
> -       .init.plt 0 (NOLOAD) : { BYTE(0) }
> -       .text.ftrace_trampoline 0 (NOLOAD) : { BYTE(0) }
> +       .plt 0 : { BYTE(0) }
> +       .init.plt 0 : { BYTE(0) }
> +       .text.ftrace_trampoline 0 : { BYTE(0) }
>  #endif
>
>  #ifdef CONFIG_KASAN_SW_TAGS
> --
> 2.35.1.265.g69c8d7142f-goog
>

Re: [PATCH] arm64 module: remove (NOLOAD)

Posted by Fangrui Song 4 years, 4 months ago

On 2022-02-18, Ard Biesheuvel wrote:
>On Fri, 18 Feb 2022 at 09:12, Fangrui Song <maskray@google.com> wrote:
>>
>> On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
>> inappropriate for .plt and .text.* sections which are always
>> SHT_PROGBITS.
>>
>> In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
>> and (NOLOAD) will be essentially ignored. In ld.lld, since
>> https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
>> customize the output section type"), ld.lld will report a `section type
>> mismatch` error. Just remove (NOLOAD) to fix the error.
>>
>> [1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
>> section should be marked as not loadable" on
>> https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
>> outdated for ELF.
>
>This patch lacks a SOB line.
>
>With one added,
>
>Acked-by: Ard Biesheuvel <ardb@kernel.org>

Ah, yes. Sorry, I haven't sent a kernel patch for a while...

Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Fangrui Song <maskray@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>

>> ---
>>  arch/arm64/include/asm/module.lds.h | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
>> index a11ccadd47d2..094701ec5500 100644
>> --- a/arch/arm64/include/asm/module.lds.h
>> +++ b/arch/arm64/include/asm/module.lds.h
>> @@ -1,8 +1,8 @@
>>  SECTIONS {
>>  #ifdef CONFIG_ARM64_MODULE_PLTS
>> -       .plt 0 (NOLOAD) : { BYTE(0) }
>> -       .init.plt 0 (NOLOAD) : { BYTE(0) }
>> -       .text.ftrace_trampoline 0 (NOLOAD) : { BYTE(0) }
>> +       .plt 0 : { BYTE(0) }
>> +       .init.plt 0 : { BYTE(0) }
>> +       .text.ftrace_trampoline 0 : { BYTE(0) }
>>  #endif
>>
>>  #ifdef CONFIG_KASAN_SW_TAGS
>> --
>> 2.35.1.265.g69c8d7142f-goog
>>

Re: [PATCH] arm64 module: remove (NOLOAD)

Posted by Will Deacon 4 years, 4 months ago

On Fri, 18 Feb 2022 00:12:09 -0800, Fangrui Song wrote:
> On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
> inappropriate for .plt and .text.* sections which are always
> SHT_PROGBITS.
> 
> In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
> and (NOLOAD) will be essentially ignored. In ld.lld, since
> https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
> customize the output section type"), ld.lld will report a `section type
> mismatch` error. Just remove (NOLOAD) to fix the error.
> 
> [...]

Applied to arm64 (for-next/linkage), thanks!

[1/1] arm64: module: remove (NOLOAD) from linker script
      https://git.kernel.org/arm64/c/4013e26670c5

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

[tip: x86/core] arm64: module: remove (NOLOAD) from linker script

Posted by tip-bot2 for Fangrui Song 4 years, 3 months ago

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     4013e26670c590944abdab56c4fa797527b74325
Gitweb:        https://git.kernel.org/tip/4013e26670c590944abdab56c4fa797527b74325
Author:        Fangrui Song <maskray@google.com>
AuthorDate:    Fri, 18 Feb 2022 00:12:09 -08:00
Committer:     Will Deacon <will@kernel.org>
CommitterDate: Fri, 25 Feb 2022 14:06:50 

arm64: module: remove (NOLOAD) from linker script

On ELF, (NOLOAD) sets the section type to SHT_NOBITS[1]. It is conceptually
inappropriate for .plt and .text.* sections which are always
SHT_PROGBITS.

In GNU ld, if PLT entries are needed, .plt will be SHT_PROGBITS anyway
and (NOLOAD) will be essentially ignored. In ld.lld, since
https://reviews.llvm.org/D118840 ("[ELF] Support (TYPE=<value>) to
customize the output section type"), ld.lld will report a `section type
mismatch` error. Just remove (NOLOAD) to fix the error.

[1] https://lld.llvm.org/ELF/linker_script.html As of today, "The
section should be marked as not loadable" on
https://sourceware.org/binutils/docs/ld/Output-Section-Type.html is
outdated for ELF.

Tested-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Fangrui Song <maskray@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220218081209.354383-1-maskray@google.com
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/include/asm/module.lds.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/module.lds.h b/arch/arm64/include/asm/module.lds.h
index a11ccad..094701e 100644
--- a/arch/arm64/include/asm/module.lds.h
+++ b/arch/arm64/include/asm/module.lds.h
@@ -1,8 +1,8 @@
 SECTIONS {
 #ifdef CONFIG_ARM64_MODULE_PLTS
-	.plt 0 (NOLOAD) : { BYTE(0) }
-	.init.plt 0 (NOLOAD) : { BYTE(0) }
-	.text.ftrace_trampoline 0 (NOLOAD) : { BYTE(0) }
+	.plt 0 : { BYTE(0) }
+	.init.plt 0 : { BYTE(0) }
+	.text.ftrace_trampoline 0 : { BYTE(0) }
 #endif
 
 #ifdef CONFIG_KASAN_SW_TAGS