[ros-kernel] Can someone give me a hand in here

[Waldo Alvarez]

On Wed, 17 Dec 2003, Skywing wrote:

> You must never read past the terminating null, *especially* in kernel mode.
> If the string is on a page boundary, that could cause a crash.

Then I suppose I have to check for such a case, using an extra register or 
intentionally putting a 0 at page boundaries saving in the stack that 
final data, and walking through pages in such a way. There will be just a 
very ligth performance degradation.
 
> The only registers that you don't need to save (on x86) are eax, ecx, and
> edx.

Yes I tested it saving ebx and still the same. Thanks for the info. But 
what's the reason? The compiler checks for it before the 
function is called everytime?

> -----Original Message-----
> From: ros-kernel-bounces at reactos.com [mailto:ros-kernel-bounces at reactos.com]
> On Behalf Of Waldo Alvarez
> Sent: Wednesday, December 17, 2003 1:21 PM
> To: ReactOS Kernel List
> Subject: [ros-kernel] Can someone give me a hand in here
> 
> Hello:
> 
> I was changing this file in ROS to speedup strlen but ReactOS 
> crashes with a page fault very quick since strlen is used almost 
> everywhere. But I'm not used to this kind of assembler format. Can someone 
> take a look at it. It could read at most 3 bytes beyond the ending 0 in 
> the string but i don't think it could be a problem since the page size is 
> 4 kb the other reason could be the ebx register I'm not saving. as opposed 
> to the previous function.
> 
> Thanks in advance
> Waldo Alvarez
> 
> 
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