[Bug binutils/18087] New: objcopy --compress-debug-sections can produce broken debug sections in PE binaries

[jon.turney at dronecode dot org.uk]

https://sourceware.org/bugzilla/show_bug.cgi?id=18087

            Bug ID: 18087
           Summary: objcopy --compress-debug-sections can produce broken
                    debug sections in PE binaries
           Product: binutils
           Version: 2.26 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: jon.turney at dronecode dot org.uk

Created attachment 8177
  --> https://sourceware.org/bugzilla/attachment.cgi?id=8177&action=edit
Update section virtual size when it's compressed or decompressed

PE binary support for objcopy --compress-debug-sections added in bug #14067
(commit a29a8af8) seems to have a problem when compression makes sections
larger.

Examining the unstripped XWin.exe for which the problem was reported [1] (using
my own PE dumper as objdump -h transparently decompresses the compressed
sections for you.)

Section Name          Virtual Size   VMA        RawSize File Offset  
Characteristics
   .text                  0017df74   00001000   0017e000   00000600   60500060
   .data                  00004184   0017f000   00004200   0017e600   c0700040
  .rdata                  000321e0   00184000   00032200   00182800   40700040
.buildid                  00000035   001b7000   00000200   001b4a00   40300040
      /4        .eh_frame 00049240   001b8000   00049400   001b4c00   40300040
    .bss                  0000eae0   00202000   00000000   00000000   c0700080
  .edata                  0002a0a5   00211000   0002a200   001fe000   40300040
  .idata                  00004c70   0023c000   00004e00   00228200   c0300040
   .rsrc                  00007800   00241000   00007400   0022d000   c0300040
  .reloc                  0000d1bc   00249000   0000d200   00234800   42300040
     /14   .debug_aranges 00002fb0   00257000   00003000   00241a00   42400040
     /29      .debug_info 007c423e   0025a000   007c4400   00244a00   42100040
     /41    .debug_abbrev 00056487   00a1f000   00056600   00a08e00   42100040
     /55      .debug_line 0009576a   00a76000   00095800   00a5f400   42100040
     /67     .debug_frame 00000038   00b0c000   00000200   00af4c00   42300040
     /80       .debug_str 00026a8b   00b0d000   00026c00   00af4e00   42100040
     /91       .debug_loc 001799f0   00b34000   00179a00   00b1ba00   42100040
    /102    .debug_ranges 00038b88   00cae000   00038c00   00c95400   42100040

Compare with this after it's compressed using objcopy
-compressed-debug-sections

Section Name          Virtual Size   VMA        RawSize File Offset  
Characteristics
   .text                  0017df74   00001000   0017e000   00000600   60500060
   .data                  00004184   0017f000   00004200   0017e600   c0700040
  .rdata                  000321e0   00184000   00032200   00182800   40700040
.buildid                  00000035   001b7000   00000200   001b4a00   40300040
      /4        .eh_frame 00049240   001b8000   00049400   001b4c00   40300040
    .bss                  0000eae0   00202000   00000000   00000000   c0700080
  .edata                  0002a0a5   00211000   0002a200   001fe000   40300040
  .idata                  00004c70   0023c000   00004e00   00228200   c0300040
   .rsrc                  00007800   00241000   00007400   0022d000   c0300040
  .reloc                  0000d1bc   00249000   0000d200   00234400   42300040
     /14  .zdebug_aranges 00002fb0   00257000   00001200   00241600   42400040
     /30     .zdebug_info 007c423e   0025a000   00356200   00242800   42100040
     /43   .zdebug_abbrev 00056487   00a1f000   0000d600   00598a00   42100040
     /58     .zdebug_line 0009576a   00a76000   00040600   005a6000   42100040
     /71    .zdebug_frame 00000038   00b0c000   00000200   005e6600   42300040
     /85      .zdebug_str 00026a8b   00b0d000   00005c00   005e6800   42100040
     /97      .zdebug_loc 001799f0   00b34000   0007de00   005ec400   42100040
    /109   .zdebug_ranges 00038b88   00cae000   00013000   0066a200   42100040

It can be seen that the virtual size of the compressed sections is not updated,
although the raw size has decreased.

Normally this is not a problem, as nothing is accessing the section contents
after the raw size.

However, if the compressor has made the data bigger, it is truncated to the
virtual size and decompression fails.

Unfortunately, small .debug_frame sections seem to be quite normal on x86.

Attached is a patch which updates the virtual size, which seems to fix this
issue.

Section Name          Virtual Size   VMA        RawSize File Offset  
Characteristics
   .text                  0017df74   00001000   0017e000   00000600   60500060
   .data                  00004184   0017f000   00004200   0017e600   c0700040
  .rdata                  000321e0   00184000   00032200   00182800   40700040
.buildid                  00000035   001b7000   00000200   001b4a00   40300040
      /4        .eh_frame 00049240   001b8000   00049400   001b4c00   40300040
    .bss                  0000eae0   00202000   00000000   00000000   c0700080
  .edata                  0002a0a5   00211000   0002a200   001fe000   40300040
  .idata                  00004c70   0023c000   00004e00   00228200   c0300040
   .rsrc                  00007800   00241000   00007400   0022d000   c0300040
  .reloc                  0000d1bc   00249000   0000d200   00234400   42300040
     /14  .zdebug_aranges 0000103e   00257000   00001200   00241600   42400040
     /30     .zdebug_info 003561b2   0025a000   00356200   00242800   42100040
     /43   .zdebug_abbrev 0000d5aa   00a1f000   0000d600   00598a00   42100040
     /58     .zdebug_line 0004049b   00a76000   00040600   005a6000   42100040
     /71    .zdebug_frame 00000045   00b0c000   00000200   005e6600   42300040
     /85      .zdebug_str 00005b42   00b0d000   00005c00   005e6800   42100040
     /97      .zdebug_loc 0007dc89   00b34000   0007de00   005ec400   42100040
    /109   .zdebug_ranges 00012e79   00cae000   00013000   0066a200   42100040

Possibly related to bug #15350

[1] https://cygwin.com/ml/cygwin/2015-03/msg00080.html

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