From: Henio Paszczak <blurrpp@yahoo.com>
To: linux-assembly@vger.kernel.org
Subject: self modyfing code and GDT
Date: Sun, 18 Mar 2007 04:41:21 -0700 (PDT) [thread overview]
Message-ID: <739235.52208.qm@web50310.mail.re2.yahoo.com> (raw)
Hi.
1) I want to write self modyfing code. I'm using 125
finction (sys_mprotect )
.section .text
.global _start
_start:
nop
movl $125,%eax
movl $smc_address,%ebx
movl $4096,%ecx
movl $7,%edx
int $0x80
orl %eax, %eax
jnz .error # if something wrong
movl $0xaabbccdd,smc_address
movl $0x0000000000,%eax
.equ smc_address, .-4
# eax==0xaabbccdd
.error:
movl $1,%eax
movl $0,%ebx
int $0x80
but it doesn't work ( %eax=0 ).
Is there any other way by changing segment descriptor
in GDT ?, and how to do this ( i have no rights to
write it ).
2) How to read 8-bytes of segment descriptor, how to
get current segment selector and the same question
about task-state segment ( selector is easy to obtain
by 'str' instruction )
Thank You in advice for help
Lukas
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next reply other threads:[~2007-03-18 11:41 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-18 11:41 Henio Paszczak [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-03-18 17:48 self modyfing code and GDT Henio Paszczak
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