[PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Fangrui Song]

lld does not dump a linker script with --verbose (it does not use a
linker script driven design and lots of linker processing is not
serializable as a linker script anyway).  With the default
--with-default-link=no build, $@T is empty and makes `test -s $@T` fail.

Just dump the linker script with -fuse-ld=bfd.  lld since 15
(https://reviews.llvm.org/D124656) supports custom RELRO sections in the
GNU ld dumped linker script.
---
 Makerules | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makerules b/Makerules
index 09c0cf8357..2edc6ee4e1 100644
--- a/Makerules
+++ b/Makerules
@@ -553,7 +553,7 @@ else
 # not for shared objects
 $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
 	$(LINK.o) -shared -Wl,-O1 \
-		  -nostdlib -nostartfiles \
+		  -nostdlib -nostartfiles -fuse-ld=bfd \
 		  $(sysdep-LDFLAGS) $(rtld-LDFLAGS) $(LDFLAGS.so) \
 		  -Wl,--verbose 2>/dev/null | \
 	  sed > $@T \
-- 
2.38.1.431.g37b22c650d-goog

Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Sam James]

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> On 6 Nov 2022, at 18:17, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
> 
> lld does not dump a linker script with --verbose (it does not use a
> linker script driven design and lots of linker processing is not
> serializable as a linker script anyway).  With the default
> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
> 
> Just dump the linker script with -fuse-ld=bfd.  lld since 15
> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
> GNU ld dumped linker script.
> ---

What if bfd isn't installed?

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Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Fangrui Song]

On 2022-11-06, Sam James wrote:
>
>
>> On 6 Nov 2022, at 18:17, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>
>> lld does not dump a linker script with --verbose (it does not use a
>> linker script driven design and lots of linker processing is not
>> serializable as a linker script anyway).  With the default
>> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>>
>> Just dump the linker script with -fuse-ld=bfd.  lld since 15
>> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
>> GNU ld dumped linker script.
>> ---
>
>What if bfd isn't installed?

Then --with-default-link=yes has to be used:)

Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Sam James]

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> On 6 Nov 2022, at 23:06, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
> 
> On 2022-11-06, Sam James wrote:
>> 
>> 
>>> On 6 Nov 2022, at 18:17, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>> 
>>> lld does not dump a linker script with --verbose (it does not use a
>>> linker script driven design and lots of linker processing is not
>>> serializable as a linker script anyway).  With the default
>>> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>>> 
>>> Just dump the linker script with -fuse-ld=bfd.  lld since 15
>>> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
>>> GNU ld dumped linker script.
>>> ---
>> 
>> What if bfd isn't installed?
> 
> Then --with-default-link=yes has to be used:)

Configure should check in that case.

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Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Fangrui Song]

On 2022-11-06, Sam James wrote:
>
>
>> On 6 Nov 2022, at 23:06, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>
>> On 2022-11-06, Sam James wrote:
>>>
>>>
>>>> On 6 Nov 2022, at 18:17, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>>>
>>>> lld does not dump a linker script with --verbose (it does not use a
>>>> linker script driven design and lots of linker processing is not
>>>> serializable as a linker script anyway).  With the default
>>>> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>>>>
>>>> Just dump the linker script with -fuse-ld=bfd.  lld since 15
>>>> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
>>>> GNU ld dumped linker script.
>>>> ---
>>>
>>> What if bfd isn't installed?
>>
>> Then --with-default-link=yes has to be used:)
>
>Configure should check in that case.

The patch isn't worse than the current state: if ld => lld, the build
will just fail due to `test -s $@T` (the linker script is empty).

Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Sam James]

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> On 6 Nov 2022, at 23:15, Fangrui Song <maskray@google.com> wrote:
> 
> On 2022-11-06, Sam James wrote:
>> 
>> 
>>> On 6 Nov 2022, at 23:06, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>> 
>>> On 2022-11-06, Sam James wrote:
>>>> 
>>>> 
>>>>> On 6 Nov 2022, at 18:17, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>>>> 
>>>>> lld does not dump a linker script with --verbose (it does not use a
>>>>> linker script driven design and lots of linker processing is not
>>>>> serializable as a linker script anyway).  With the default
>>>>> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>>>>> 
>>>>> Just dump the linker script with -fuse-ld=bfd.  lld since 15
>>>>> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
>>>>> GNU ld dumped linker script.
>>>>> ---
>>>> 
>>>> What if bfd isn't installed?
>>> 
>>> Then --with-default-link=yes has to be used:)
>> 
>> Configure should check in that case.
> 
> The patch isn't worse than the current state: if ld => lld, the build
> will just fail due to `test -s $@T` (the linker script is empty).

Sure, but could you add a quick configure check while you're here?

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Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Fangrui Song]

On 2022-11-06, Sam James wrote:
>
>
>> On 6 Nov 2022, at 23:06, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>
>> On 2022-11-06, Sam James wrote:
>>>
>>>
>>>> On 6 Nov 2022, at 18:17, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>>>
>>>> lld does not dump a linker script with --verbose (it does not use a
>>>> linker script driven design and lots of linker processing is not
>>>> serializable as a linker script anyway).  With the default
>>>> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>>>>
>>>> Just dump the linker script with -fuse-ld=bfd.  lld since 15
>>>> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
>>>> GNU ld dumped linker script.
>>>> ---
>>>
>>> What if bfd isn't installed?
>>
>> Then --with-default-link=yes has to be used:)
>
>Configure should check in that case.

I am unsure whether the additioinal complexity is worthwhile (and how?).

The patch is a follow-up to my comment in April:
https://sourceware.org/pipermail/libc-alpha/2022-April/138278.html
where the changed --with-default-link default required my lld build to specify --with-default-link=yes explicitly.

Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Florian Weimer]

* Fangrui Song:

> lld does not dump a linker script with --verbose (it does not use a
> linker script driven design and lots of linker processing is not
> serializable as a linker script anyway).  With the default
> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>
> Just dump the linker script with -fuse-ld=bfd.  lld since 15
> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
> GNU ld dumped linker script.
> ---
>  Makerules | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makerules b/Makerules
> index 09c0cf8357..2edc6ee4e1 100644
> --- a/Makerules
> +++ b/Makerules
> @@ -553,7 +553,7 @@ else
>  # not for shared objects
>  $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
>  	$(LINK.o) -shared -Wl,-O1 \
> -		  -nostdlib -nostartfiles \
> +		  -nostdlib -nostartfiles -fuse-ld=bfd \
>  		  $(sysdep-LDFLAGS) $(rtld-LDFLAGS) $(LDFLAGS.so) \
>  		  -Wl,--verbose 2>/dev/null | \
>  	  sed > $@T \

Would you please add the comment?

I'm not sure if a configure check is required.  We have a path towards
removal of the custom linker script; the vfprintf refactor I posted is a
first step.

Thanks,
Florian

Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Sam James]

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> On 7 Nov 2022, at 08:31, Florian Weimer via Libc-alpha <libc-alpha@sourceware.org> wrote:
> 
> * Fangrui Song:
> 
>> lld does not dump a linker script with --verbose (it does not use a
>> linker script driven design and lots of linker processing is not
>> serializable as a linker script anyway).  With the default
>> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>> 
>> Just dump the linker script with -fuse-ld=bfd.  lld since 15
>> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
>> GNU ld dumped linker script.
>> ---
>> Makerules | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/Makerules b/Makerules
>> index 09c0cf8357..2edc6ee4e1 100644
>> --- a/Makerules
>> +++ b/Makerules
>> @@ -553,7 +553,7 @@ else
>> # not for shared objects
>> $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
>> $(LINK.o) -shared -Wl,-O1 \
>> -   -nostdlib -nostartfiles \
>> +   -nostdlib -nostartfiles -fuse-ld=bfd \
>>   $(sysdep-LDFLAGS) $(rtld-LDFLAGS) $(LDFLAGS.so) \
>>   -Wl,--verbose 2>/dev/null | \
>>   sed > $@T \
> 
> Would you please add the comment?
> 
> I'm not sure if a configure check is required.  We have a path towards
> removal of the custom linker script; the vfprintf refactor I posted is a
> first step.
> 

That works for me.



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Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Fangrui Song]

On 2022-11-08, Sam James wrote:
>
>
>> On 7 Nov 2022, at 08:31, Florian Weimer via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>
>> * Fangrui Song:
>>
>>> lld does not dump a linker script with --verbose (it does not use a
>>> linker script driven design and lots of linker processing is not
>>> serializable as a linker script anyway).  With the default
>>> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>>>
>>> Just dump the linker script with -fuse-ld=bfd.  lld since 15
>>> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
>>> GNU ld dumped linker script.
>>> ---
>>> Makerules | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/Makerules b/Makerules
>>> index 09c0cf8357..2edc6ee4e1 100644
>>> --- a/Makerules
>>> +++ b/Makerules
>>> @@ -553,7 +553,7 @@ else
>>> # not for shared objects
>>> $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
>>> $(LINK.o) -shared -Wl,-O1 \
>>> -   -nostdlib -nostartfiles \
>>> +   -nostdlib -nostartfiles -fuse-ld=bfd \
>>>   $(sysdep-LDFLAGS) $(rtld-LDFLAGS) $(LDFLAGS.so) \
>>>   -Wl,--verbose 2>/dev/null | \
>>>   sed > $@T \
>>
>> Would you please add the comment?
>>
>> I'm not sure if a configure check is required.  We have a path towards
>> removal of the custom linker script; the vfprintf refactor I posted is a
>> first step.
>>
>
>That works for me.
>
>

Added comments...


 From 00ee52ee0753a8d849c23d4e051f10aa8a4e2074 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
Date: Mon, 7 Nov 2022 16:21:13 -0800
Subject: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

lld does not dump a linker script with --verbose (it does not use a
linker script driven design and lots of linker processing is not
serializable as a linker script anyway).  With the default
--with-default-link=no build, $@T is empty and makes `test -s $@T` fail.

Just dump the linker script with -fuse-ld=bfd.  lld since 15
(https://reviews.llvm.org/D124656) supports custom RELRO sections in the
GNU ld dumped linker script.
---
  Makerules | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Makerules b/Makerules
index 09c0cf8357..ed6873a1a8 100644
--- a/Makerules
+++ b/Makerules
@@ -546,14 +546,16 @@ endef
  
  ifeq (yes,$(use-default-link))
  # If the linker is good enough, we can let it use its default linker script.
+# In the long term the custom linker script will be removed.
  shlib-lds =
  shlib-lds-flags =
  else
  # binutils only position loadable notes into the first page for binaries,
  # not for shared objects
+# lld --verbose does not dump a linker script.  Use -fuse-ld=bfd.
  $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
  	$(LINK.o) -shared -Wl,-O1 \
-		  -nostdlib -nostartfiles \
+		  -nostdlib -nostartfiles -fuse-ld=bfd \
  		  $(sysdep-LDFLAGS) $(rtld-LDFLAGS) $(LDFLAGS.so) \
  		  -Wl,--verbose 2>/dev/null | \
  	  sed > $@T \
-- 
2.38.1.431.g37b22c650d-goog

Re: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd

[Sam James]

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> On 8 Nov 2022, at 00:22, Fangrui Song via Libc-alpha <libc-alpha@sourceware.org> wrote:
> 
> On 2022-11-08, Sam James wrote:
>> 
>> 
>>> On 7 Nov 2022, at 08:31, Florian Weimer via Libc-alpha <libc-alpha@sourceware.org> wrote:
>>> 
>>> * Fangrui Song:
>>> 
>>>> lld does not dump a linker script with --verbose (it does not use a
>>>> linker script driven design and lots of linker processing is not
>>>> serializable as a linker script anyway).  With the default
>>>> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
>>>> 
>>>> Just dump the linker script with -fuse-ld=bfd.  lld since 15
>>>> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
>>>> GNU ld dumped linker script.
>>>> ---
>>>> Makerules | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>> 
>>>> diff --git a/Makerules b/Makerules
>>>> index 09c0cf8357..2edc6ee4e1 100644
>>>> --- a/Makerules
>>>> +++ b/Makerules
>>>> @@ -553,7 +553,7 @@ else
>>>> # not for shared objects
>>>> $(common-objpfx)shlib.lds: $(common-objpfx)config.make $(..)Makerules
>>>> $(LINK.o) -shared -Wl,-O1 \
>>>> -   -nostdlib -nostartfiles \
>>>> +   -nostdlib -nostartfiles -fuse-ld=bfd \
>>>>  $(sysdep-LDFLAGS) $(rtld-LDFLAGS) $(LDFLAGS.so) \
>>>>  -Wl,--verbose 2>/dev/null | \
>>>>  sed > $@T \
>>> 
>>> Would you please add the comment?
>>> 
>>> I'm not sure if a configure check is required.  We have a path towards
>>> removal of the custom linker script; the vfprintf refactor I posted is a
>>> first step.
>>> 
>> 
>> That works for me.
>> 
>> 
> 
> Added comments...
> 
> 
> From 00ee52ee0753a8d849c23d4e051f10aa8a4e2074 Mon Sep 17 00:00:00 2001
> From: Fangrui Song <maskray@google.com>
> Date: Mon, 7 Nov 2022 16:21:13 -0800
> Subject: [PATCH] Makerules: Generate shlib.lds with -fuse-ld=bfd
> 
> lld does not dump a linker script with --verbose (it does not use a
> linker script driven design and lots of linker processing is not
> serializable as a linker script anyway).  With the default
> --with-default-link=no build, $@T is empty and makes `test -s $@T` fail.
> 
> Just dump the linker script with -fuse-ld=bfd.  lld since 15
> (https://reviews.llvm.org/D124656) supports custom RELRO sections in the
> GNU ld dumped linker script.
> ---

Thanks!

Reviewed-by: Sam James <sam@gentoo.org <mailto:sam@gentoo.org>>


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