Rewrite/fix cygwin1.dbg generation
Pedro Alves
pedro_alves@portugalmail.pt
Sat Nov 3 17:32:00 GMT 2007
Hi guys,
As was being discussed at gdb-patches@ [1], the cygwin1.dbg
(the debug info of cygwin1.dll) file misses the section
info of the non-debug sections. Gdb doesn't like that
so much, and issues a few annoying warnings. Previous
versions of gdb had those warnings suppressed at all
times, but since current gdb had its dll support
rewritten, those warnings resurfaced again.
[1] http://sourceware.org/ml/gdb-patches/2007-10/msg00325.html
This patch simplifies/standardises the cygwin1.dbg generation
by using the --strip-debug/--only-keep-debug facilities of
gnu strip, which already know how to keep the section info,
and remove the contents of non-debug sections.
Old/current version:
>objdump.exe -h oldver/cygwin1.dbg
oldver/cygwin1.dbg: file format pei-i386
Sections:
Idx Name Size VMA LMA File off Algn
0 .stab 00212cd0 61280000 61280000 000001c8 2**2
CONTENTS, READONLY, DEBUGGING, EXCLUDE
1 .stabstr 006b00a4 61493000 61493000 00212fc8 2**0
CONTENTS, READONLY, DEBUGGING, EXCLUDE
New version:
>objdump.exe -h newver/cygwin1.dbg
newver/cygwin1.dbg: file format pei-i386
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 001350c4 61001000 61001000 00000000 2**4
ALLOC, LOAD, READONLY, CODE, DATA
1 .autoload_text 000013d8 61137000 61137000 00000000 2**2
ALLOC, LOAD, CODE
2 .data 0000b51c 61139000 61139000 00000000 2**4
ALLOC, LOAD, DATA
3 .rdata 0004fb80 61145000 61145000 00000000 2**4
ALLOC, LOAD, READONLY, DATA
4 .bss 00009530 61195000 61195000 00000000 2**4
ALLOC
5 .edata 00008487 6119f000 6119f000 00000000 2**2
ALLOC, LOAD, READONLY, DATA
6 .rsrc 00000420 611a8000 611a8000 00000000 2**2
ALLOC, LOAD, DATA
7 .reloc 00013424 611a9000 611a9000 00000000 2**2
ALLOC, LOAD, READONLY, DATA
8 .cygwin_dll_common 00017ae4 611bd000 611bd000 00000000 2**2
ALLOC, LOAD, DATA, SHARED
9 .idata 0000b000 611d5000 611d5000 00000000 2**2
ALLOC, LOAD, DATA
10 .cygheap 000a0000 611e0000 611e0000 00000000 2**2
ALLOC
11 .stab 00212cd0 61280000 61280000 00000380 2**2
CONTENTS, READONLY, DEBUGGING, EXCLUDE
12 .stabstr 006b00a4 61493000 61493000 00213180 2**0
CONTENTS, READONLY, DEBUGGING, EXCLUDE
---------------------------------------------------------
Since the .gnu_debuglink_overlay matching is now done,
this produces one difference in cygwin1.dll. The
.gnu_debuglink section is now the last section,
after .cygheap. This is not a problem, since
.gnu_debuglink is not mapped into memory by the OS loader.
The patch also removed __cygwin_debug_size, which
seems was a leftover from earlier experiences (?).
For reference, the old and new section info of cygwin1.dll.
>objdump.exe -h oldver/new-cygwin1.dll
oldver/new-cygwin1.dll: file format pei-i386
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 001350c4 61001000 61001000 00000400 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
1 .autoload_text 000013d8 61137000 61137000 00135600 2**2
CONTENTS, ALLOC, LOAD, CODE
2 .data 0000b51c 61139000 61139000 00136a00 2**4
CONTENTS, ALLOC, LOAD, DATA
3 .rdata 0004fb80 61145000 61145000 00142000 2**4
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .bss 00009530 61195000 61195000 00000000 2**4
ALLOC
5 .edata 00008487 6119f000 6119f000 00191c00 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
6 .rsrc 00000420 611a8000 611a8000 0019a200 2**2
CONTENTS, ALLOC, LOAD, DATA
7 .reloc 00013424 611a9000 611a9000 0019a800 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
8 .cygwin_dll_common 00017ae4 611bd000 611bd000 001ade00 2**2
CONTENTS, ALLOC, LOAD, DATA, SHARED
9 .gnu_debuglink 00000010 611d5000 611d5000 001c5a00 2**2
CONTENTS, READONLY, DEBUGGING, EXCLUDE
10 .idata 0000a000 611d6000 611d6000 001c5c00 2**2
CONTENTS, ALLOC, LOAD, DATA
11 .cygheap 000a0000 611e0000 611e0000 00000000 2**2
ALLOC
>objdump.exe -h newver/new-cygwin1.dll
newver/new-cygwin1.dll: file format pei-i386
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 001350c4 61001000 61001000 00000400 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
1 .autoload_text 000013d8 61137000 61137000 00135600 2**2
CONTENTS, ALLOC, LOAD, CODE
2 .data 0000b51c 61139000 61139000 00136a00 2**4
CONTENTS, ALLOC, LOAD, DATA
3 .rdata 0004fb80 61145000 61145000 00142000 2**4
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .bss 00009530 61195000 61195000 00000000 2**4
ALLOC
5 .edata 00008487 6119f000 6119f000 00191c00 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
6 .rsrc 00000420 611a8000 611a8000 0019a200 2**2
CONTENTS, ALLOC, LOAD, DATA
7 .reloc 00013424 611a9000 611a9000 0019a800 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
8 .cygwin_dll_common 00017ae4 611bd000 611bd000 001ade00 2**2
CONTENTS, ALLOC, LOAD, DATA, SHARED
9 .idata 0000b000 611d5000 611d5000 001c5a00 2**2
CONTENTS, ALLOC, LOAD, DATA
10 .cygheap 000a0000 611e0000 611e0000 00000000 2**2
ALLOC
11 .gnu_debuglink 00000010 61280000 61280000 001d0a00 2**2
CONTENTS, READONLY, DEBUGGING
The winsup testsuite shows no changes.
I've bootstrapped winsup with gcc 3.4.4 and this
new cygwin1.dll. I can step into cygwin1.dll code just
fine with both gdb head, and with the gdb from the distro.
This change should also make it possible to debug
cygwin1.dll correctly if it wasn't loaded at its
prefered load base - although I haven't tested that.
The dllfixdbg hunk looks hard to read. Here's what is looks
like after patching:
#!/bin/sh
# Copyright 2007 Red Hat, Inc.
#
# This file is part of Cygwin.
#
# This software is a copyrighted work licensed under the terms of the
# Cygwin license. Please consult the file "CYGWIN_LICENSE" for
# details.
#
set -x
STRIP=$1
OBJCOPY=$2
DLL=$3
DBG=$4
${STRIP} --strip-debug ${DLL} -o stripped-${DLL}
${STRIP} --only-keep-debug ${DLL} -o ${DBG}
${OBJCOPY} --add-gnu-debuglink=${DBG} stripped-${DLL} ${DLL}
rm -f stripped-${DLL}
Is the patch OK?
Cheers,
Pedro Alves
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