The Place to Start for Operating System Developers
http://f.osdev.org/
siiansjack wrote:What gdb instruction are you using to single-step your code?
This is not a Linux assembly.stevewoods1986 wrote:Hello.
If this is Linux Assembly, please can I have the code where it doesn't work.
Thanks
Steve.
Code: Select all
0: e8 02 00 call 0x5
3: 00 00 add %al,(%bx,%si)
5: eb fe jmp 0x5
7: 55 push %bp
8: 89 e5 mov %sp,%bp
a: cd 80 int $0x80
c: b8 00 00 mov $0x0,%ax
f: 00 00 add %al,(%bx,%si)
11: 5d pop %bp
12: c3 ret
13: 00 14 add %dl,(%si)
15: 00 00 add %al,(%bx,%si)
17: 00 00 add %al,(%bx,%si)
19: 00 00 add %al,(%bx,%si)
1b: 00 01 add %al,(%bx,%di)
1d: 7a 52 jp 0x71
1f: 00 01 add %al,(%bx,%di)
21: 7c 08 jl 0x2b
23: 01 1b add %bx,(%bp,%di)
25: 0c 04 or $0x4,%al
27: 04 88 add $0x88,%al
29: 01 00 add %ax,(%bx,%si)
2b: 00 1c add %bl,(%si)
2d: 00 00 add %al,(%bx,%si)
2f: 00 1c add %bl,(%si)
31: 00 00 add %al,(%bx,%si)
33: 00 d3 add %dl,%bl
35: ff (bad)
36: ff (bad)
37: ff 0c decw (%si)
39: 00 00 add %al,(%bx,%si)
3b: 00 00 add %al,(%bx,%si)
3d: 41 inc %cx
3e: 0e push %cs
3f: 08 85 02 42 or %al,0x4202(%di)
43: 0d 05 48 or $0x4805,%ax
46: c5 0c lds (%si),%cx
48: 04 04 add $0x4,%al
I see a contradiction here.stdcall wrote: The code for it:Code: Select all
00000000 <.data>:
True, it could be an exception (fault). What platform is he/she using? Int 0x80 is Linux.iansjack wrote:BTW, note that the interrupt flag has no connection with a software interrupt.
This is no Linux, this is my OS. there's a dedicated isr 0x80 handler I've written and placed in the IDT. and event if there wasn't I would expect to see a general exception fault.stevewoods1986 wrote:True, it could be an exception (fault). What platform is he/she using? Int 0x80 is Linux.iansjack wrote:BTW, note that the interrupt flag has no connection with a software interrupt.
That's not a contradiction, the format I use for executable is just plain binrary, there are no sections like in ELF.XenOS wrote:I see a contradiction here.stdcall wrote: The code for it:Code: Select all
00000000 <.data>:
Code: Select all
objdump -D -b binary -mi386 -Maddr16,data16 ./binary_code
program: file format binary
Disassembly of section .data:
00000000 <.data>:
0: e8 02 00 call 0x5
....
You haven't really said anything about the context of your issue.stdcall wrote:I found a workaround around this but I don't seem to understand why it didn't work.
I changed the int number to 0x40 instead of 0x80 and now it works perfectly.
I don't get it.
I'm Running Linux, on top of that I run Qemu and I'm connecting to the os using remote GDB protocol and Qemu offers.LtG wrote:You haven't really said anything about the context of your issue.stdcall wrote:I found a workaround around this but I don't seem to understand why it didn't work.
I changed the int number to 0x40 instead of 0x80 and now it works perfectly.
I don't get it.
Are you running Linux, on which you run Qemu, on which you run your own OS, on which you run some test app you compiler that tries to use int 0x80? And you are using gdb from the host Linux to connect to Qemu and single stepping over said int 0x80?
Are you using a recent version of Qemu or something ancient? Did you compile it or use a packaged one? Are you using KVM with Qemu or..?