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a115433



Joined: 05 Mar 2010
Posts: 144
a115433
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]
Post 26 Apr 2010, 07:34
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a115433



Joined: 05 Mar 2010
Posts: 144
a115433
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???
Post 26 Apr 2010, 19:50
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17474
Location: In your JS exploiting you and your system
revolution
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.
Post 26 Apr 2010, 21:12
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a115433



Joined: 05 Mar 2010
Posts: 144
a115433
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.
Post 27 Apr 2010, 06:30
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a115433



Joined: 05 Mar 2010
Posts: 144
a115433
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).
Post 28 Apr 2010, 08:54
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a115433



Joined: 05 Mar 2010
Posts: 144
a115433
--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
Post 28 Apr 2010, 09:37
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17474
Location: In your JS exploiting you and your system
revolution
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
Post 28 Apr 2010, 09:39
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