NEED_REGISTER_FRAME_INFO can be replaced by -static-libgcc

NEED_REGISTER_FRAME_INFO can be replaced by -static-libgcc

[Christian Franke]

Hi,

a note regarding this fix:

2010-04-11  Vladimir Serbinenko <...>

         Fix cygwin compilation.

         * configure.ac: Define NEED_REGISTER_FRAME_INFO.
         * include/grub/misc.h (__register_frame_info)
         [NEED_REGISTER_FRAME_INFO && !UTIL]: New export.
         (__deregister_frame_info) [NEED_REGISTER_FRAME_INFO && !UTIL]: 
Likewise.
         * kern/misc.c (__register_frame_info)
         [NEED_REGISTER_FRAME_INFO && !UTIL]: New empty function.
         (__deregister_frame_info) [NEED_REGISTER_FRAME_INFO && !UTIL]: 
Likewise.


--- configure.ac    2010-04-11 14:14:51 +0000
+++ configure.ac    2010-04-12 14:58:44 +0000
@@ -376,7 +376,11 @@
  # For platforms where ELF is not the default link format.
  AC_MSG_CHECKING([for command to convert module to ELF format])
  case "${host_os}" in
-  cygwin) TARGET_OBJ2ELF='grub-pe2elf' ;;
+  cygwin) TARGET_OBJ2ELF='grub-pe2elf';
+# FIXME: put proper test here
+  AC_DEFINE([NEED_REGISTER_FRAME_INFO], 1,
+        [Define to 1 if GCC generates calls to __register_frame_info()])
+  ;;
    *) ;;


The *_frame_info symbols are set undefined to force linkage of the 
libgcc_s shared library or dll.

This can be prevented by TARGET_LDFLAGS=-static-libgcc. To build from 
grub-1.98 tarball on Cygwin, run configure with this argument.

May also be necessary on other build platforms when -shared-libgcc is 
the default. It may be possible simply set -static-libgcc unconditionally.

-- 
Regards,
Christian Franke

Re: NEED_REGISTER_FRAME_INFO can be replaced by -static-libgcc

[Vladimir 'φ-coder/phcoder' Serbinenko]

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Christian Franke wrote:
> Hi,
>
> a note regarding this fix:
>

>
> The *_frame_info symbols are set undefined to force linkage of the
> libgcc_s shared library or dll.
>
> This can be prevented by TARGET_LDFLAGS=-static-libgcc. To build from
> grub-1.98 tarball on Cygwin, run configure with this argument.
>
> May also be necessary on other build platforms when -shared-libgcc is
> the default. It may be possible simply set -static-libgcc
> unconditionally.
>
We already supply -lgcc --static-libgcc. Do you know why it still had
issues?
And I also doubt usefullness of pulling these functions since reference
to them is purely dummy: no relocation uses it so it will only increase
code size. Another concern is the behviour of these functions in grub
environment if they ever get called.

-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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Re: NEED_REGISTER_FRAME_INFO can be replaced by -static-libgcc

[Christian Franke]

[-- Attachment #1: Type: text/plain, Size: 1615 bytes --]

Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> Christian Franke wrote:
>    
>
>> The *_frame_info symbols are set undefined to force linkage of the
>> libgcc_s shared library or dll.
>>
>> This can be prevented by TARGET_LDFLAGS=-static-libgcc. To build from
>> grub-1.98 tarball on Cygwin, run configure with this argument.
>>
>> May also be necessary on other build platforms when -shared-libgcc is
>> the default. It may be possible simply set -static-libgcc
>> unconditionally.
>>
>>      
> We already supply -lgcc --static-libgcc. Do you know why it still had
> issues?
>    

The above is only set when linking the kernel image.

According to 'gcc -dumpspecs' of Cygwin gcc 4.3.4-3, options '-u 
___[de]register_frame_info' are always passed to the linker if 
-static-libgcc is not specified. This is Cygwin and MinGW specific: In 
the exe startup code these symbols are loaded only if present, so the 
DLL must be forced to load first.

As a consequence, the symbols are also set undefined when the GRUB 
pre-*.o files are generated with 'ld -r'.

The attached patch works for me with the bzr revision preceding the 
NEED_REGISTER_FRAME_INFO fix.


> And I also doubt usefullness of pulling these functions since reference
> to them is purely dummy: no relocation uses it so it will only increase
> code size. Another concern is the behviour of these functions in grub
> environment if they ever get called.
>
>    

AFAICS from the gcc source, the functions are used in EH stack unwinding 
code in libgcc. The compiler itself does not generate calls to these 
functions.


-- 
Regards,
Christian Franke


[-- Attachment #2: grub2-static-libgcc.patch --]
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=== modified file 'Makefile.in'
--- Makefile.in	2010-04-10 23:14:31 +0000
+++ Makefile.in	2010-04-14 08:04:34 +0000
@@ -98,12 +98,12 @@
 OBJCONV = @OBJCONV@
 TARGET_CPPFLAGS = @TARGET_CPPFLAGS@ -I$(srcdir)/include -I$(builddir) -I$(builddir)/include \
 	-Wall -W
-TARGET_LDFLAGS = -nostdlib @TARGET_LDFLAGS@
+TARGET_LDFLAGS = -nostdlib -static-libgcc @TARGET_LDFLAGS@
 TARGET_IMG_LDSCRIPT = @TARGET_IMG_LDSCRIPT@
 TARGET_IMG_LDFLAGS = -nostdlib @TARGET_IMG_LDFLAGS@
 TARGET_IMG_CFLAGS = @TARGET_IMG_CFLAGS@
 TARGET_OBJ2ELF = @TARGET_OBJ2ELF@
-kernel_img_LDFLAGS = -static-libgcc -lgcc
+kernel_img_LDFLAGS = -lgcc
 EXEEXT = @EXEEXT@
 OBJCOPY = @OBJCOPY@
 STRIP = @STRIP@

Re: NEED_REGISTER_FRAME_INFO can be replaced by -static-libgcc

[Vladimir 'φ-coder/phcoder' Serbinenko]

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Christian Franke wrote:
> Vladimir 'φ-coder/phcoder' Serbinenko wrote:
>> Christian Franke wrote:
>>   
>>> The *_frame_info symbols are set undefined to force linkage of the
>>> libgcc_s shared library or dll.
>>>
>>> This can be prevented by TARGET_LDFLAGS=-static-libgcc. To build from
>>> grub-1.98 tarball on Cygwin, run configure with this argument.
>>>
>>> May also be necessary on other build platforms when -shared-libgcc is
>>> the default. It may be possible simply set -static-libgcc
>>> unconditionally.
>>>
>>>      
>> We already supply -lgcc --static-libgcc. Do you know why it still had
>> issues?
>>    
>
> The above is only set when linking the kernel image.
>
> According to 'gcc -dumpspecs' of Cygwin gcc 4.3.4-3, options '-u
> ___[de]register_frame_info' are always passed to the linker if
> -static-libgcc is not specified. This is Cygwin and MinGW specific: In
> the exe startup code these symbols are loaded only if present, so the
> DLL must be forced to load first.
>
> As a consequence, the symbols are also set undefined when the GRUB
> pre-*.o files are generated with 'ld -r'.
>
> The attached patch works for me with the bzr revision preceding the
> NEED_REGISTER_FRAME_INFO fix.
>
Doesn't it risk linking e.g. __bswapsi2 into every module which uses it
during partial link? It would increase module size on RISC
>
>> And I also doubt usefullness of pulling these functions since reference
>> to them is purely dummy: no relocation uses it so it will only increase
>> code size. Another concern is the behviour of these functions in grub
>> environment if they ever get called.
>>
>>    
>
> AFAICS from the gcc source, the functions are used in EH stack
> unwinding code in libgcc. The compiler itself does not generate calls
> to these functions.
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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Re: NEED_REGISTER_FRAME_INFO can be replaced by -static-libgcc

[Christian Franke]

Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> Christian Franke wrote:
>    
>>
>> According to 'gcc -dumpspecs' of Cygwin gcc 4.3.4-3, options '-u
>> ___[de]register_frame_info' are always passed to the linker if
>> -static-libgcc is not specified. This is Cygwin and MinGW specific: In
>> the exe startup code these symbols are loaded only if present, so the
>> DLL must be forced to load first.
>>
>> As a consequence, the symbols are also set undefined when the GRUB
>> pre-*.o files are generated with 'ld -r'.
>>
>> The attached patch works for me with the bzr revision preceding the
>> NEED_REGISTER_FRAME_INFO fix.
>>
>>      
> Doesn't it risk linking e.g. __bswapsi2 into every module which uses it
> during partial link? It would increase module size on RISC
>    

Partial linking with '-Wl,-r' does never pull any code from libraries. 
Specifying '-lgcc' has no effect in this case.

Cannot test this on RISC, it is at least true on i686-linux, -freebsd 
and -cygwin.

-- 
Regards,
Christian Franke

Re: NEED_REGISTER_FRAME_INFO can be replaced by -static-libgcc

[Vladimir 'φ-coder/phcoder' Serbinenko]

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Applied.
Christian Franke wrote:
> Vladimir 'φ-coder/phcoder' Serbinenko wrote:
>> Christian Franke wrote:
>>   
>>> The *_frame_info symbols are set undefined to force linkage of the
>>> libgcc_s shared library or dll.
>>>
>>> This can be prevented by TARGET_LDFLAGS=-static-libgcc. To build from
>>> grub-1.98 tarball on Cygwin, run configure with this argument.
>>>
>>> May also be necessary on other build platforms when -shared-libgcc is
>>> the default. It may be possible simply set -static-libgcc
>>> unconditionally.
>>>
>>>      
>> We already supply -lgcc --static-libgcc. Do you know why it still had
>> issues?
>>    
>
> The above is only set when linking the kernel image.
>
> According to 'gcc -dumpspecs' of Cygwin gcc 4.3.4-3, options '-u
> ___[de]register_frame_info' are always passed to the linker if
> -static-libgcc is not specified. This is Cygwin and MinGW specific: In
> the exe startup code these symbols are loaded only if present, so the
> DLL must be forced to load first.
>
> As a consequence, the symbols are also set undefined when the GRUB
> pre-*.o files are generated with 'ld -r'.
>
> The attached patch works for me with the bzr revision preceding the
> NEED_REGISTER_FRAME_INFO fix.
>
>
>> And I also doubt usefullness of pulling these functions since reference
>> to them is purely dummy: no relocation uses it so it will only increase
>> code size. Another concern is the behviour of these functions in grub
>> environment if they ever get called.
>>
>>    
>
> AFAICS from the gcc source, the functions are used in EH stack
> unwinding code in libgcc. The compiler itself does not generate calls
> to these functions.
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/grub-devel


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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