When I run objdump -D on my file, I get the assembly code I expect.
kernel.elf: file format elf32-i386
Disassembly of section .text:
00100000 <__code>:
100000: 02 b0 ad 1b 03 00 add 0x31bad(%eax),%dh
100006: 00 00 add %al,(%eax)
100008: fb sti
100009: 4f dec %edi
10000a: 52 push %edx
10000b: e4 00 in $0x0,%al
10000d: 00 10 add %dl,(%eax)
10000f: 00 00 add %al,(%eax)
100011: 00 10 add %dl,(%eax)
100013: 00 00 add %al,(%eax)
100015: 20 10 and %dl,(%eax)
100017: 00 00 add %al,(%eax)
100019: 40 inc %eax
10001a: 10 00 adc %al,(%eax)
10001c: 20 00 and %al,(%eax)
10001e: 10 00 adc %al,(%eax)
00100020 <start>:
100020: fa cli
100021: bc 00 40 10 00 mov $0x104000,%esp
100026: 53 push %ebx
100027: e8 02 00 00 00 call 10002e <main>
10002c: eb fe jmp 10002c <start+0xc>
0010002e <main>:
10002e: 55 push %ebp
10002f: 89 e5 mov %esp,%ebp
100031: 83 ec 10 sub $0x10,%esp
100034: c7 45 fc 28 23 00 00 movl $0x2328,-0x4(%ebp)
10003b: b8 ef be ad de mov $0xdeadbeef,%eax
100040: c9 leave
100041: c3 ret
100042: 66 90 xchg %ax,%ax
100044: 66 90 xchg %ax,%ax
100046: 66 90 xchg %ax,%ax
100048: 66 90 xchg %ax,%ax
...
However, when I open the file on GDB (via QEMU and target remote) and run (gdb) disassemble, the same locations hold null values instead of the expected instructions (add %al,(%eax) is equivalent to 00 00).
(gdb) set $pc = mboot
(gdb) disas
Dump of assembler code for function mboot:
=> 0x00100000 <+0>: add %al,(%eax)
0x00100002 <+2>: add %al,(%eax)
0x00100004 <+4>: add %al,(%eax)
0x00100006 <+6>: add %al,(%eax)
0x00100008 <+8>: add %al,(%eax)
0x0010000a <+10>: add %al,(%eax)
0x0010000c <+12>: add %al,(%eax)
0x0010000e <+14>: add %al,(%eax)
0x00100010 <+16>: add %al,(%eax)
0x00100012 <+18>: add %al,(%eax)
0x00100014 <+20>: add %al,(%eax)
0x00100016 <+22>: add %al,(%eax)
0x00100018 <+24>: add %al,(%eax)
0x0010001a <+26>: add %al,(%eax)
0x0010001c <+28>: add %al,(%eax)
0x0010001e <+30>: add %al,(%eax)
End of assembler dump.
(gdb) set $pc = start
(gdb) disas
Dump of assembler code for function start:
=> 0x00100020 <+0>: add %al,(%eax)
0x00100022 <+2>: add %al,(%eax)
0x00100024 <+4>: add %al,(%eax)
0x00100026 <+6>: add %al,(%eax)
0x00100028 <+8>: add %al,(%eax)
0x0010002a <+10>: add %al,(%eax)
0x0010002c <+12>: add %al,(%eax)
End of assembler dump.
(gdb) set $pc = main
(gdb) disas
Dump of assembler code for function main:
=> 0x0010002e <+0>: add %al,(%eax)
0x00100030 <+2>: add %al,(%eax)
0x00100032 <+4>: add %al,(%eax)
0x00100034 <+6>: add %al,(%eax)
0x00100036 <+8>: add %al,(%eax)
0x00100038 <+10>: add %al,(%eax)
0x0010003a <+12>: add %al,(%eax)
0x0010003c <+14>: add %al,(%eax)
0x0010003e <+16>: add %al,(%eax)
0x00100040 <+18>: add %al,(%eax)
End of assembler dump.
Why is this happening? Why doesn't GDB read (load?) the correct values?
