On Tue, May 6, 2008 at 7:34 AM, Peter Teoh <htmldeveloper@xxxxxxxxx> wrote:
I am working on a 32-bit BIOS that is running on 32-bit hardware and as further development we want to test 64-bit processors (new Xeon chips). The problem is, I cannot recompile BIOS to 64-bit mode due to compatibility reasons. So the requirement is to call 64-bit code from a 32-bit code. There were 3 ways I could have made this work:
1) Compile 32-bit BIOS and 64-bit code separately and try to link them with some modification (if any) I asked earlier in this forum.
2) Call an assembly file from 32-bit code. This assembly file will make transition from 32-bit to 32e (64-bit) mode and call the function in 64-bit code, comes back and makes the transition back to 32-bit mode. Here, again the problem remains the same. The assembly file will be compiled either 32-bit or 64-bit and there's no way I can link all 3 files together.
3) Compile and lijnk 32-bit C and asm files as one file; compile 64-bit C file separately and put the object code into a file at known addresses. Make the 32-bit linked file jump to the address of 64-bit file and come back.
Though, I haven't tried but I think I can make 3) work but that is my last resort and I want to find out some way to be able to compile and link 32-bit and 64-bit mode code together or be able to call 64-bit code (64 or 32-bit ELF header) from 32-bit code (32-bit ELF header).
Please help me with this and correct me if I have some misunderstanding about ELF headers.
/tejas
First at the hardware level: AMD64 has a few mode, among them pure
64-bit, pure 32bit, mixed 64-32-bit, and etc. So theoretically at
the assembly level, u can still run 32bit assembly a 64-bit CPU.
2nd, at the software level (essentially: it is possible to run 32bit
in 64bit environment.....done by the different distros as below):
http://www.redhat.com/magazine/009jul05/features/multilib/
http://www.debian-administration.org/articles/534
http://www-uxsup.csx.cam.ac.uk/pub/doc/suse/suse9.2/suselinux-adminguide_en/ch06.html
http://www.scribd.com/doc/363677/Benchmarks-AMD64-in-32bit-mode-vs-64bit-mode-Ubuntu
https://help.ubuntu.com/community/32bit_and_64bit
How all these work (*I think*) is basically having a 64-bit shell
(windows is called WOW64 http://en.wikipedia.org/wiki/WOW64) that can
switch to 32 bit mode to run the program, and therefore everything
inside that process are running at 32bit, and vice versa. Some
binary-only applications (like Flash) may not have 64-bit version, and
therefore the browser have to be 32bit.
But all kernel modules/kernel development (*I think*) must be done in
a 64bit environment....unless there exists a 32bit kernel wrapper in
64bit kernel which i am not aware of.
I suspect I may have misunderstood u...in view of what is written
above please elaborate your requirements????
I am working on a 32-bit BIOS that is running on 32-bit hardware and as further development we want to test 64-bit processors (new Xeon chips). The problem is, I cannot recompile BIOS to 64-bit mode due to compatibility reasons. So the requirement is to call 64-bit code from a 32-bit code. There were 3 ways I could have made this work:
1) Compile 32-bit BIOS and 64-bit code separately and try to link them with some modification (if any) I asked earlier in this forum.
2) Call an assembly file from 32-bit code. This assembly file will make transition from 32-bit to 32e (64-bit) mode and call the function in 64-bit code, comes back and makes the transition back to 32-bit mode. Here, again the problem remains the same. The assembly file will be compiled either 32-bit or 64-bit and there's no way I can link all 3 files together.
3) Compile and lijnk 32-bit C and asm files as one file; compile 64-bit C file separately and put the object code into a file at known addresses. Make the 32-bit linked file jump to the address of 64-bit file and come back.
Though, I haven't tried but I think I can make 3) work but that is my last resort and I want to find out some way to be able to compile and link 32-bit and 64-bit mode code together or be able to call 64-bit code (64 or 32-bit ELF header) from 32-bit code (32-bit ELF header).
Please help me with this and correct me if I have some misunderstanding about ELF headers.
/tejas
--
On Tue, May 6, 2008 at 2:14 AM, tejas khatiwala <socretez@xxxxxxxxx> wrote:
> Hello,
>
> This is not exactly relevant to Linux kernel but I'm gonna ask any way.
>
> Is there any way I can modify a 64-bit ELF object file to make it look like
> 32-bit ELF object file and link it (using `ld`) with 32-bit ELF file?
>
> I tried libelf but was unsuccessful. I had this pretty link
> http://people.freebsd.org/~jkoshy/download/libelf/article.html from Freebsd
> website and it seems like the libelf library on Freebsd system is not
> similar to that on Linux system as it complained for "vis.h" headerfile and
> few library calls such as `elf_setshstrndx()`
>
> Any suggestions?
>
> Thanks :-)
>
> /tejas
>
Regards,
Peter Teoh
