Hi, to debug the work of a boot sector, you can use dosemu (with a
diskimage drive) and dosdebug (for dosemu) or, better, Bochs, and
the built-in debugger of Bochs. Versions of Bochs which have the
debugger enabled start in "halted in debugger" state, so your next
step will be to set a linear address (or anything similar, as long
as it is not int3-style) breakpoint at 7c00 and hit "continue".
Then the debugger will halt the simulated PC as soon as the boot
sector starts. Happy debugging :-).
> bochs
> help
help - show list of debugger commands
help 'command'- show short command description
...
-*- Execution control -*-
c|cont, s|step|stepi, p|n|next, modebp
-*- Breakpoint management -*-
vb|vbreak, lb|lbreak, pb|pbreak|b|break, sb, sba, blist,
...
<bochs:4> lb 0x7c00
<bochs:5> c
(0) Breakpoint 1, 0x7c00 in ?? ()
Next at t=767846
(0) [0x00007c00] 0000:7c00 (unk. ctxt): jmp .+0x7c3e ; eb3c
<bochs:8> s
Next at t=767847
(0) [0x00007c3e] 0000:7c3e (unk. ctxt): cli ; fa
<bochs:9> u/10
00007c3e: ( ): cli ; fa
00007c3f: ( ): cld ; fc
00007c40: ( ): xor ax, ax ; 31c0
...
You get the idea :-).
Eric
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