Re: perl-5.14.4

[Achim Gratz <Stromeko at nexgo dot de>]

Corinna Vinschen writes:
> Hang on.  Perhaps I just missed the crucial point here, but it just
> occured to me that the DLLs are rebased as part of the autorebase
> script.

Yes, they routinely are.  Even on 64bit when they have been
auto-image-based originally.

> So what you have is a DLL which gets some automatic address at build
> time.  Then the debug information is split off.  At this point, is the
> debug information usable?

I assume yes, but I don't really know how to check.  In any case, that's
the way it has been for quite some time.


/usr/bin/cygperl5_14.dll:     file format pei-x86-64

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .text         0014b2a0  00000003ed741000  00000003ed741000  00000400  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
  1 .data         00003028  00000003ed88d000  00000003ed88d000  0014b800  2**6
                  CONTENTS, ALLOC, LOAD, DATA
  2 .rdata        00021a24  00000003ed891000  00000003ed891000  0014ea00  2**6
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .buildid      00000035  00000003ed8b3000  00000003ed8b3000  00170600  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .pdata        00005364  00000003ed8b4000  00000003ed8b4000  00170800  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  5 .xdata        000064c0  00000003ed8ba000  00000003ed8ba000  00175c00  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  6 .bss          000002b0  00000003ed8c1000  00000003ed8c1000  00000000  2**6
                  ALLOC
  7 .edata        0000b3e9  00000003ed8c2000  00000003ed8c2000  0017c200  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  8 .idata        00002008  00000003ed8ce000  00000003ed8ce000  00187600  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  9 .reloc        00001464  00000003ed8d1000  00000003ed8d1000  00189800  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
 10 .gnu_debuglink 00000018  00000003ed8d3000  00000003ed8d3000  0018ae00  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA

/usr/lib/debug/usr/bin/cygperl5_14.dll.dbg:     file format pei-x86-64

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .text         0014b2a0  00000004d1891000  00000004d1891000  00000000  2**4
                  ALLOC, LOAD, READONLY, CODE, DATA
  1 .data         00003028  00000004d19dd000  00000004d19dd000  00000000  2**6
                  ALLOC, LOAD, DATA
  2 .rdata        00021a24  00000004d19e1000  00000004d19e1000  00000000  2**6
                  ALLOC, LOAD, READONLY, DATA
  3 .buildid      00000035  00000004d1a03000  00000004d1a03000  00000600  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .pdata        00005364  00000004d1a04000  00000004d1a04000  00000000  2**2
                  ALLOC, LOAD, READONLY, DATA
  5 .xdata        000064c0  00000004d1a0a000  00000004d1a0a000  00000000  2**2
                  ALLOC, LOAD, READONLY, DATA
  6 .bss          000002b0  00000004d1a11000  00000004d1a11000  00000000  2**6
                  ALLOC
  7 .edata        0000b3e9  00000004d1a12000  00000004d1a12000  00000000  2**2
                  ALLOC, LOAD, READONLY, DATA
  8 .idata        00002008  00000004d1a1e000  00000004d1a1e000  00000000  2**2
                  ALLOC, LOAD, DATA
  9 .reloc        00001464  00000004d1a21000  00000004d1a21000  00000000  2**2
                  ALLOC, LOAD, READONLY, DATA
 10 .debug_aranges 000009b0  00000004d1a23000  00000004d1a23000  00000800  2**4
                  CONTENTS, READONLY, DEBUGGING
 11 .debug_info   00261e08  00000004d1a24000  00000004d1a24000  00001200  2**0
                  CONTENTS, READONLY, DEBUGGING
 12 .debug_abbrev 0000ddc9  00000004d1c86000  00000004d1c86000  00263200  2**0
                  CONTENTS, READONLY, DEBUGGING
 13 .debug_line   0004ed6e  00000004d1c94000  00000004d1c94000  00271000  2**0
                  CONTENTS, READONLY, DEBUGGING
 14 .debug_frame  00022378  00000004d1ce3000  00000004d1ce3000  002bfe00  2**3
                  CONTENTS, READONLY, DEBUGGING
 15 .debug_str    00004ebb  00000004d1d06000  00000004d1d06000  002e2200  2**0
                  CONTENTS, READONLY, DEBUGGING
 16 .debug_loc    00289775  00000004d1d0b000  00000004d1d0b000  002e7200  2**0
                  CONTENTS, READONLY, DEBUGGING
 17 .debug_ranges 000568b0  00000004d1f95000  00000004d1f95000  00570a00  2**0
                  CONTENTS, READONLY, DEBUGGING
 18 .gnu_debuglink 0000000c  00000004d1fec000  00000004d1fec000  005c7400  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA

> Then somebody installs the package and autorebase rebases the DLL 
> /usr/bin/foo.dll.  But it does not rebase the debug info for the DLL
> /usr/lib/debug/usr/bin/foo.dll.dbg.

Again, my impression so far had been that there is nothing to rebase
there.  Even if you did, rebase doesn't touch the data in those
sections, it just changes the image base.

> If the /usr/lib/debug/usr/bin/foo.dll.dbg file is rebased to the same
> address as /usr/bin/foo.dll, shouldn't that "fix" the issue?

I would rather suspect it produces exactly the same problem it does with
the full DLL.

> If that's really the issue, I'm wondering if that can be fixed or
> worked around in GDB.  If that's too much hassle, we should probably
> start rebasing the debug info in /usr/lib/debug as well.  That
> only requires some small hacking of rebase.

As long as the debug information is made unuseable by doing the rebase,
I don't see why we should start rebasing the debug files.  AFAIK, if we
keep them non-rebased then everything works fine or we'd have heard
complaints by now.  I only recognized that there was something going on
because I need to rebase the DLL for Perl modules before I can test them
(on 32bit at least) and when cygport later packaged the files it didn't
find any debug information in them anymore (again the information is
still there and has indeed not been altered, but nm doesn't output it
along with the symbols and so cygport assumes they aren't there).


Regards,
Achim.
-- 
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