Re: Segfault on the i386 enter instruction

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Fri, 12 May 2006, Denis Vlasenko wrote:

> On Friday 12 May 2006 17:07, linux-os (Dick Johnson) wrote:
>>> 	.file	"a.c"
>>> 	.version	"01.01"
>>> gcc2_compiled.:
>>> .section	.rodata
>>> .LC0:
>>> 	.string	"asdf\n"
>>> .text
>>> 	.align 4
>>> .globl main
>>> 	.type	 main,@function
>>> main:
>>> 	enter $10008, $0
>>> #	pushl %ebp
>>> #	movl %esp,%ebp
>>> #	subl $10008,%esp
>>> 	addl $-12,%esp
>>          ^^^^^^^^^^^^^^____________ WTF
>>          adding a negative number is subtracting that positive value.
>>          You just subtracted 0xfffffff3 (on a 32-bit machine) from
>>          the stack pointer. It damn-well better seg-fault!
>
> No. Try it yourself.
> --
> vda

It doesn't matter. It means that you still own the space there
(it's mapped into your process). The code is bogus, broken beyond
all repair. It has nothing to do with 'enter' it has to do with
putting the stack pointer (wrapping it) to somewhere it shouldn't
be. The stack pointer is normally around 0xafff0000. It just got
wrapped down past zero up to fafff00d, then stuff got pushed
onto it for the call.

>

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
New book: http://www.lymanschool.com
_


****************************************************************
The information transmitted in this message is confidential and may be privileged.  Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited.  If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to [email protected] - and destroy all copies of this information, including any attachments, without reading or disclosing them.

Thank you.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux