Yasm and bad Windows executables using Mingw/ld

[Peter Tanski]

Hello Peter,

Maybe I was wrong about the original problem--it may not be due to  
the presence or absence of the .stab and .stabstr sections.  Instead,  
the .comment section seems to be the real difference:

output from objdump -h [file]:

--output from yasm-r1705
hello.obj:     file format pe-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
   0 .text         0000013a  00000000  00000000  000000b4  2**4
                   CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
   1 .rodata       00000020  00000000  00000000  000002de  2**3
                   CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
   2 .data         00000030  00000000  00000000  00000330  2**2
                   CONTENTS, ALLOC, LOAD, RELOC, DATA
   3 .comment      00000009  00000000  00000000  0000037e  2**2
                   CONTENTS, READONLY, DEBUGGING

--output from mingw/as
hello.o:     file format pe-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
   0 .text         00000140  00000000  00000000  000000dc  2**4
                   CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
   1 .data         00000030  00000000  00000000  0000021c  2**4
                   CONTENTS, ALLOC, LOAD, RELOC, DATA
   2 .bss          00000000  00000000  00000000  00000000  2**4
                   ALLOC
   3 .rodata       00000020  00000000  00000000  0000024c  2**2
                   CONTENTS, ALLOC, LOAD, RELOC, DATA
   4 .rdata$zzz    00000008  00000000  00000000  0000026c  2**2
                   CONTENTS, ALLOC, LOAD, READONLY, DATA

The big difference between these two is the .comment and the PE-COFF  
read-only data section, .rdata$zzz.  Yasm seems to follow the Nasm  
model for putting the section header table into the .comment section  
(at the top, following the ELF format), correct?.

The objdump of the bad executable, the good executable and another  
good executable from mingw/as shows that the .stab and .stabstr  
sections do not hurt:

--ghc executable using 'ld' without stripping symbols:
hello_badexec.exe:     file format pei-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
   0 .comment      00000009  00000000  00000000  00000358  2**2
                   CONTENTS, READONLY, DEBUGGING
   1 .text         00032f34  00401000  00401000  00000600  2**4
                   CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
   2 .data         00002980  00434000  00434000  00033600  2**4
                   CONTENTS, ALLOC, LOAD, DATA
   3 .rdata        00007120  00437000  00437000  00036000  2**4
                   CONTENTS, ALLOC, LOAD, READONLY, DATA
   4 .rodata       00000020  0043f000  0043f000  0003d200  2**2
                   CONTENTS, ALLOC, LOAD, READONLY, DATA
   5 .bss          00002460  00440000  00440000  00000000  2**4
                   ALLOC
   6 .idata        00000fd0  00443000  00443000  0003d400  2**2
                   CONTENTS, ALLOC, LOAD, DATA
   7 .stab         00016308  00444000  00444000  0003e400  2**2
                   CONTENTS, READONLY, DEBUGGING, NEVER_LOAD, EXCLUDE
   8 .stabstr      00002959  0045b000  0045b000  00054800  2**0
                   CONTENTS, READONLY, DEBUGGING, NEVER_LOAD, EXCLUDE

--ghc executable using 'ld' and stripping all symbols:
hello_good.exe:     file format pei-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
   0 .text         00032f34  00401000  00401000  00000400  2**4
                   CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
   1 .data         00002980  00434000  00434000  00033400  2**4
                   CONTENTS, ALLOC, LOAD, DATA
   2 .rdata        00007120  00437000  00437000  00035e00  2**4
                   CONTENTS, ALLOC, LOAD, READONLY, DATA
   3 .rodata       00000020  0043f000  0043f000  0003d000  2**2
                   CONTENTS, ALLOC, LOAD, READONLY, DATA
   4 .bss          00002460  00440000  00440000  00000000  2**4
                   ALLOC
   5 .idata        00000fd0  00443000  00443000  0003d200  2**2
                   CONTENTS, ALLOC, LOAD, DATA

--ghc executable using mingw/as, no symbols stripped:
hello_tst.exe:     file format pei-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
   0 .text         00032f34  00401000  00401000  00000400  2**4
                   CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
   1 .data         00002980  00434000  00434000  00033400  2**4
                   CONTENTS, ALLOC, LOAD, DATA
   2 .rodata       00000020  00437000  00437000  00035e00  2**2
                   CONTENTS, ALLOC, LOAD, DATA
   3 .rdata        00007128  00438000  00438000  00036000  2**4
                   CONTENTS, ALLOC, LOAD, READONLY, DATA
   4 .bss          00002460  00440000  00440000  00000000  2**4
                   ALLOC
   5 .idata        00000fd0  00443000  00443000  0003d200  2**2
                   CONTENTS, ALLOC, LOAD, DATA
   6 .stab         00016308  00444000  00444000  0003e200  2**2
                   CONTENTS, READONLY, DEBUGGING, NEVER_LOAD, EXCLUDE
   7 .stabstr      00002959  0045b000  0045b000  00054600  2**0
                   CONTENTS, READONLY, DEBUGGING, NEVER_LOAD, EXCLUDE

The only difference between the bad executable and the mingw/as  
executable (aside from section ordering) is the .comment section at  
the top.

I am also looking at the GNU-binutils (gas) source code, particularly  
the Binary File Descriptor files (bfd/peXXigen.c, etc.)  to see their  
solution to the problem.  (I am a bit curious about the .rdata$zzz  
section.)

Cheers,
Pete