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Re: [win32] wrong solib from/to addresses

Hi Joel,

Joel Brobecker wrote:
We are working on porting our product to Vista, and we have noticed
an issue that this version of the MS OS makes more apparent: The from/to
addresses printed in the "info shared" listing are correct only when
the DLL was loaded at the prefered load address (which is in the
ImageBase field of the COFF/PE header).

I collegue of mine told me that, for security reasons, system DLLs
on Vista are now always rebased, and thus, the information printed
by info based is off by a certain offset.

The core of the attached patch is to implement the target_so_ops
method relocate_section_addresses. For that, I needed to compute
the offset between the load address and the image_base, and store
it for later use (during the call of our routine above). There
were two challenges:

  1. Compute this image base. Rather than dig into the COFF/PE
     data, I took a simpler route that I think has already been
     taken: Use the start address of the .text section. I think
     this is already used to do the symbol relocation.

  2. Make that information available: I found that the lm_info
     field was not allocated, so I had to add its initialization.

With all these changes, the address are correct again.

I had a similar patch here, that I dumped in favor of a rewrite
of win32 solibs on top of Daniel's pending solib-target.c.  If
I remember correctly, if you are moving the relocation to
relocate_section_addresses, you should remove
get_relocated_section_addrs as it is doing the same work, albeit
bypassing gdb's solib mechanism.

In my version I didn't cache the image_base on lm_info, but computed
it inside relocate_section_addresses.

Tested on x86-windows, no regression. Dejagnu on Vista is not working
at all for me, so I ran the testsuite on XP instead.

Did you test this with a recent binutils/ld? With the binutils version distributed with Cygwin the dll tests fail, because of the use of the .so/.sl extension instead of .dll. Current ld from cvs recognizes dlls without looking at the file extension.

Eg, does gdb.base/shreloc.exp pass for you?

Pedro Alves

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