Re: [Elftoolchain-developers] Multiple archs and platforms.

[Joseph K. <jk...@us...>]

> I am developing a linker for the RTEMS project to support dynamic
> loading. ... I am pleased to report there are no problems with the
> testing I have done.

That's great to know.

> You can find the RTEMS project at http://www.rtems.org/ and the linker's
> code is: [snip]

I will take a look.

> Windows is a little more difficult to support. The couple of issues I
> have so far are:

> 1. Includes such as "#include <sys/errno.h>", and "#include
> <sys/cdefs.h>" are not supported. I have worked around this issue with a
> win32 specific include directory that maps to the standard headers in my
> application.

I lack clue about program development under Windows.

> 2. There is no mmap call. I see:
>
>   LIBELF_F_RAWFILE_MALLOC | LIBELF_F_SPECIAL_FILE
>
> could be used but I am not sure about a couple of things. Does this read
> the whole ELF file into memory ?

Yes, the RAWFILE_MALLOC case will read the whole ELF object into
memory.  The motivation for the code was to support reading of an ELF
object from device files ("/dev/ksyms" in {Free,Net}BSD) and from
streams (e.g., from sockets and pipes).  Such file descriptors usually
do not support mmap() or seek(), so ELF object needs to be read in
sequentially.

One optimization for the RAWFILE_MALLOC case could be to have libelf
read in portions of the ELF object "on demand".  That said, further
study would be needed to determine the tradeoffs involved---IIRC the
default layout puts the section header table at the very end of an ELF
object, so use cases that access sections could end up reading the
entire ELF object into memory, even if such an optmization were
implemented.

> Secondly, I really do not like the idea
> of __WIN32__ all over the place. I can support "HAVE_CONFIG_H" and
> "HAVE_MMAP" etc. How should I handle this ?

IMHO, an ELFTC_HAVE_MMAP configuration option would be the way to go.

FYI, I have created ticket #366 to track this item:

  http://sourceforge.net/apps/trac/elftoolchain/ticket/366.

Regards,
Koshy