debug doesnt work

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a115433

Joined: 05 Mar 2010
Posts: 144

a115433 26 Apr 2010, 07:34

code is in protected nonpaged mode:

Code:

mov eax,dbb
mov dr0,eax


mov eax,dr7
bts eax,1 ;global enable

btr eax,16 ;execution
btr eax,17 ;


btr eax,18 ;length 1
btr eax,19 ;
mov dr7,eax



dbb: jmp $

doesnt work.
why? jmp $ is executed without debug exception.
when i change r/w and length effect is same, debug do not happen.
trap flag works fine.[/code]

26 Apr 2010, 07:34

a115433

Joined: 05 Mar 2010
Posts: 144

a115433 26 Apr 2010, 19:50

ok it DOESNT work, and i have no clue whats wrong with it.
like its ignored! maybe i have to set some flags in CRX/MSR???

26 Apr 2010, 19:50

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20634
Location: In your JS exploiting you and your system

revolution 26 Apr 2010, 21:12

One minute reading the doc would have saved you eight hours of needless effort.

Intel doc:

MOV—Move to/from Debug Registers wrote:

#GP(0) If the current privilege level is not 0.
#DB If any debug register is accessed while the DR7.GD[bit 13] = 1.

26 Apr 2010, 21:12

a115433

Joined: 05 Mar 2010
Posts: 144

a115433 27 Apr 2010, 06:30

Quote:

#GP(0) If the current privilege level is not 0.
#DB If any debug register is accessed while the DR7.GD[bit 13] = 1.

im in cpl = 0
and this bit is clear.

im not getting any interrupt, its just ignoring it.
and yes, all drs are successfully set. breakpoint instead of triggering int 1 is IGNORED.

27 Apr 2010, 06:30

a115433

Joined: 05 Mar 2010
Posts: 144

a115433 28 Apr 2010, 08:54

Code:

pm_start:


mov ax,0x10
mov ds,ax



mov ecx,dr7

mov eax,dbb
mov dr0,eax


mov eax,dr7
bts eax,1

bts eax,9



bts eax,16
bts eax,17


bts eax,18
bts eax,19

mov dr7,eax


mov dword eax,[dbb]
mov dword [dbb],eax



jmp $

align 4
dbb dd 0

it DOES NOT work.
im doing everything exactly as written in manual, and it doesnt work!
jmp $ is executed instead of error indicating lack of idt vector (wich happens with trap flag, or GD bit).

28 Apr 2010, 08:54

a115433

Joined: 05 Mar 2010
Posts: 144

a115433 28 Apr 2010, 09:37

--enable-x86-debugger no X86 debugger support. If the software you run in bochs needs to use the x86 hardware debugging facilities such as DR0..DR7, instruction and data breakpoints etc., then you should use this option. Otherwise don't use it, as it will slow down the emulation.

FUUUUUUUUUUUUUUUU

28 Apr 2010, 09:37

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20634
Location: In your JS exploiting you and your system

revolution 28 Apr 2010, 09:39

Well if you had mentioned at the start that you were using bochs then the answer would have been easy.

bochs != real CPU or mobo

28 Apr 2010, 09:39

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