* calculating byte
@ 2003-07-23 22:15 ssams
2003-07-24 6:13 ` Anticipating a Reply
2003-07-24 7:54 ` hp
0 siblings, 2 replies; 7+ messages in thread
From: ssams @ 2003-07-23 22:15 UTC (permalink / raw)
To: linux-assembly
hi all
if u have time, please answer my following question
i try to learn more about assembly. in a time i'found some
article that explain about exploit, and i get this
following code. My question is.. how to calculate byte at
each line..?
thnaks before
regard
ssams
.....
.....
movl %esi,array-offset(%esi) # 3 bytes
movb $0x0,nullbyteoffset(%esi)# 4 bytes
movl $0x0,null-offset(%esi) # 7 bytes
movl $0xb,%eax # 5 bytes
movl %esi,%ebx # 2 bytes
leal array-offset,(%esi),%ecx # 3 bytes
leal null-offset(%esi),%edx # 3 bytes
int $0x80 # 2 bytes
....
....
===========================================================================================
"TELKOMNet Instan Divre VI Kalimantan memberikan DISKON PROGRESSIVE kepada para pengguna
TELKOMNet-Instan hingga 50% mulai bulan Juli hingga September 2003."
===========================================================================================
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: calculating byte
2003-07-23 22:15 calculating byte ssams
@ 2003-07-24 6:13 ` Anticipating a Reply
2003-07-24 7:54 ` hp
1 sibling, 0 replies; 7+ messages in thread
From: Anticipating a Reply @ 2003-07-24 6:13 UTC (permalink / raw)
To: ssams, linux-assembly
Hi ,
You can find this by looking at the
Machine Opcodes required for each instruction .
Bye
--- ssams <ssams@telkom.net> wrote: > hi all
> if u have time, please answer my following question
> i try to learn more about assembly. in a time
> i'found some
> article that explain about exploit, and i get this
> following code. My question is.. how to calculate
> byte at
> each line..?
> thnaks before
> regard
> ssams
> .....
> .....
> movl %esi,array-offset(%esi) # 3 bytes
> movb $0x0,nullbyteoffset(%esi)# 4 bytes
> movl $0x0,null-offset(%esi) # 7 bytes
> movl $0xb,%eax # 5 bytes
> movl %esi,%ebx # 2 bytes
> leal array-offset,(%esi),%ecx # 3 bytes
> leal null-offset(%esi),%edx # 3 bytes
> int $0x80 # 2 bytes
> ....
> ....
>
===========================================================================================
> "TELKOMNet Instan Divre VI Kalimantan memberikan
> DISKON PROGRESSIVE kepada para pengguna
> TELKOMNet-Instan hingga 50% mulai bulan Juli hingga
> September 2003."
>
===========================================================================================
> -
> To unsubscribe from this list: send the line
> "unsubscribe linux-assembly" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at
http://vger.kernel.org/majordomo-info.html
________________________________________________________________________
Send free SMS using the Yahoo! Messenger. Go to http://in.mobile.yahoo.com/new/pc/
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: calculating byte
2003-07-23 22:15 calculating byte ssams
2003-07-24 6:13 ` Anticipating a Reply
@ 2003-07-24 7:54 ` hp
2003-07-25 13:38 ` switching to real mode? Wolfgang Huber
1 sibling, 1 reply; 7+ messages in thread
From: hp @ 2003-07-24 7:54 UTC (permalink / raw)
To: ssams, linux-assembly
ssams am Mittwoch, 23. Juli 2003 23:15:
> hi all
> if u have time, please answer my following question
> i try to learn more about assembly. in a time i'found some
> article that explain about exploit, and i get this
> following code. My question is.. how to calculate byte at
> each line..?
for a rough calculation, as a rule of thumb:
simple opcode 1 byte (very few such opcodes, e.g. push/pop)
opcode w. addressing modifier 2 bytes
mov immediate data + 4 bytes
signed byte displacement + 1 byte
'other' addressing size + 1 byte (16/32bit)
'other' data item size + 1 byte (word/dword)
'exotic operations praefix' + 1byte (e.g. "0F")
hp
--
Linux,Assembly,Forth: http://www.lxhp.in-berlin.de/index-lx.shtml en/de
FAQ(s) + DOCs at http://linuxassembly.org
pse, reply to << lx -at- lxhp -dot- in-berlin -dot- de >>
^ permalink raw reply [flat|nested] 7+ messages in thread
* switching to real mode?
2003-07-24 7:54 ` hp
@ 2003-07-25 13:38 ` Wolfgang Huber
2003-07-25 16:55 ` hp
2003-07-25 17:20 ` Maciej Hrebien
0 siblings, 2 replies; 7+ messages in thread
From: Wolfgang Huber @ 2003-07-25 13:38 UTC (permalink / raw)
To: linux-assembly
Hi!
I know this question sounds a bit silly...
How would one switch to real mode in Linux, are there any caveats?
Wolfgang
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: switching to real mode?
2003-07-25 13:38 ` switching to real mode? Wolfgang Huber
@ 2003-07-25 16:55 ` hp
2003-07-25 17:20 ` Maciej Hrebien
1 sibling, 0 replies; 7+ messages in thread
From: hp @ 2003-07-25 16:55 UTC (permalink / raw)
To: Wolfgang Huber, linux-assembly
Wolfgang Huber am Freitag, 25. Juli 2003 14:38:
> Hi!
>
> I know this question sounds a bit silly...
indeed...
> How would one switch to real mode in Linux, are there any caveats?
none - if you can.
DA => FAQ(s) + DOCs at http://linuxassembly.org
hp.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: switching to real mode?
2003-07-25 13:38 ` switching to real mode? Wolfgang Huber
2003-07-25 16:55 ` hp
@ 2003-07-25 17:20 ` Maciej Hrebien
2003-07-25 19:42 ` switching to real mode Rick A. Hohensee
1 sibling, 1 reply; 7+ messages in thread
From: Maciej Hrebien @ 2003-07-25 17:20 UTC (permalink / raw)
To: linux-assembly
Wolfgang Huber wrote:
>
> Hi!
>
> I know this question sounds a bit silly...
> How would one switch to real mode in Linux, are there any caveats?
>
> Wolfgang
For what purpose you need it? From linux x86 users point of view: you
just can't, or am i wrong? ;) Generally once you switch to protected
mode you don't need real one and if you want to run some code written
for real mode you just run it in vm86 mode rather than switching it back
(as i remember dosemu does something like this). If you are interested
in "hard" switch i suggest to read ie. intel's "software developers
manual vol. 3, system programming", chapter 8 "processor management and
initialization", point 8 "mode switching" (1999 version).
Correct me linux-assemblers if i'm wrong!
--
Maciej Hrebien
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: switching to real mode
2003-07-25 17:20 ` Maciej Hrebien
@ 2003-07-25 19:42 ` Rick A. Hohensee
0 siblings, 0 replies; 7+ messages in thread
From: Rick A. Hohensee @ 2003-07-25 19:42 UTC (permalink / raw)
To: m_hrebien; +Cc: linux-assembly
Linux has support for V86 mode, which switches to something closely
resembling Real Mode on IRET, and switches to pmode on an interrupt, so
that 8086 code can be run on a pmode paged OS, and the V86 task can be
paged, which allows numerous V86 tasks to think they have the low meg.
Otherwise, switching to Real Mode = Leaving Linux, or any other unix-alike.
You could do that too, and alternate between Linux and Real Mode, maybe.
Doing so would be a more twisted hack than Al Viro's namespaces.
Rick Hohensee
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2003-07-25 19:42 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2003-07-23 22:15 calculating byte ssams
2003-07-24 6:13 ` Anticipating a Reply
2003-07-24 7:54 ` hp
2003-07-25 13:38 ` switching to real mode? Wolfgang Huber
2003-07-25 16:55 ` hp
2003-07-25 17:20 ` Maciej Hrebien
2003-07-25 19:42 ` switching to real mode Rick A. Hohensee
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.