From: Henio Paszczak <blurrpp@yahoo.com>
To: linux-assembly@vger.kernel.org
Subject: self modyfing code and GDT
Date: Sun, 18 Mar 2007 10:48:48 -0700 (PDT) [thread overview]
Message-ID: <186179.43467.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 17:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-18 17:48 Henio Paszczak [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-03-18 11:41 self modyfing code and GDT Henio Paszczak
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