A simple linker script question

A simple linker script question

[Tao Zhang]

Hi,

I am new to linker script. I just want to write one to place all system
library code before the user code. Could anybody give me some hint on
that?

Thanks a lot

Tao


			-Tao Zhang (zhangtao@cc.gatech.edu)

Re: A simple linker script question

[Nick Clifton]

Hi Tao,

> I am new to linker script. I just want to write one to place all system
> library code before the user code. Could anybody give me some hint on
> that?

First of all - why do you need to do this ?

Secondly do you mean that you want to put the contents of the sections 
in the system libraries before similarly named sections in the user 
code, or do you want to put the entire contents of the system libraries 
before the user code ?

For example given a system library sys.a containing a .text section and 
a .data section and a user file user.o also containing a .text and a 
.data section, how do you want the final executable to appear ?  Should 
it have one .text section containing the contents of the .text section 
from sys.a and then the contents of the .text section from user.o, and 
followed by a single .data section containing the contents of the .data 
sections from sys.a and user.o.  Or, should the output file have two 
.text sections, one from sys.a and one from user.o, with the one from 
sys.a occurring first in the memory map, and similarly two .data sections ?

Assuming you want a single .text section and a single .data section then 
you can do something like this in your linker script:

   SECTIONS {
      .text : { *(EXCLUDE_FILE (user.o).text)
                *(.text) }
      .data : { *(EXCLUDE_FILE (user.o).data)
                *(.data) }
   }

Cheers
   Nick

Re: A simple linker script question

[Tao Zhang]

Hi, Nick

Thanks a lot for your reply. I am working on a weird problem and I need
to play with the program binary layout a little bit.

I understand the piece of linker script you wrote in your email, it will
place non-user code and data before user code and data. What if I want
more fine grained control?  Say I want to place libfoo.a before libbar.a,
I need to do some patten matching. That's my current problem. I think the
names of the input libraries have full path with them, for example,
/usr/lib/libfoo.a(foo1.o). I don't know how to pattern match those '/' and
'(' and ')' in linker script. I tried single and double quote and it looks
not working. Could anybody give some help?

Thanks so much

Tao



			-Tao Zhang (zhangtao@cc.gatech.edu)

On Mon, 21 Jun 2004, Nick Clifton wrote:

> Hi Tao,
>
> > I am new to linker script. I just want to write one to place all system
> > library code before the user code. Could anybody give me some hint on
> > that?
>
> First of all - why do you need to do this ?
>
> Secondly do you mean that you want to put the contents of the sections
> in the system libraries before similarly named sections in the user
> code, or do you want to put the entire contents of the system libraries
> before the user code ?
>
> For example given a system library sys.a containing a .text section and
> a .data section and a user file user.o also containing a .text and a
> .data section, how do you want the final executable to appear ?  Should
> it have one .text section containing the contents of the .text section
> from sys.a and then the contents of the .text section from user.o, and
> followed by a single .data section containing the contents of the .data
> sections from sys.a and user.o.  Or, should the output file have two
> .text sections, one from sys.a and one from user.o, with the one from
> sys.a occurring first in the memory map, and similarly two .data sections ?
>
> Assuming you want a single .text section and a single .data section then
> you can do something like this in your linker script:
>
>    SECTIONS {
>       .text : { *(EXCLUDE_FILE (user.o).text)
>                 *(.text) }
>       .data : { *(EXCLUDE_FILE (user.o).data)
>                 *(.data) }
>    }
>
> Cheers
>    Nick
>
>
>

Re: A simple linker script question

[Nick Clifton]

Hi Tao,

> I understand the piece of linker script you wrote in your email, it will
> place non-user code and data before user code and data. What if I want
> more fine grained control?  Say I want to place libfoo.a before libbar.a,
> I need to do some patten matching. That's my current problem. I think the
> names of the input libraries have full path with them, for example,
> /usr/lib/libfoo.a(foo1.o). I don't know how to pattern match those '/' and
> '(' and ')' in linker script. I tried single and double quote and it looks
> not working. Could anybody give some help?

I am sorry, but I just do not think that this is possible with the 
current implementation of the linker.  Can you give us more information 
about what you are trying to do ?  Perhaps there is a different way that 
the same results can be achieved.

Cheers
   Nick