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FromDenis Vlasenko <>
SubjectRe: 4k stacks
DateSat, 24 Dec 2005 14:03:38 +0200
On Thursday 22 December 2005 23:53, linux-os (Dick Johnson) wrote:
> > Yesterday I sent a patch to add stack-poison so the stack usage
> could be observed.> > Today I wrote a small program and tested the stack usage. Both
> the program and the patch is attached. The result is:
> > Offset : 2ec8f000	Available Stack bytes = 3104> Offset : 2ecb1000	Available Stack bytes = 3104> Offset : 2ee5f000	Available Stack bytes = 20> Offset : 2f36d000	Available Stack bytes = 3104> Offset : 2fd09000	Available Stack bytes = 3012> Offset : 2fd0b000	Available Stack bytes = 3312> Offset : 2fd0f000	Available Stack bytes = 2132> Offset : 2fd2f000	Available Stack bytes = 2744> Offset : 2fd57000	Available Stack bytes = 2900> Offset : 2fdd5000	Available Stack bytes = 1400> Offset : 2fe35000	Available Stack bytes = 2832> Offset : 2ff3f000	Available Stack bytes = 776> Offset : 2ff45000	Available Stack bytes = 3188> > This, after compiling the kernel. I did not have 4k stacks
> enabled for this test so any crashing of the stack beyond
> one page will not hurt the system. This was on linux-2.6.13.4.
> > Anyway, I tried to enable 4k stacks and the machine would
> not boot past trying to install the first module. It just
> stopped with the interrupts disabled. So, I am now rebuilding
> the kernel back as I write this. That's why I am using 2.6.13
> at the moment.> > Anyway, getting down to 20 bytes of stack-space available
> seems to be pretty scary.

+       movl    %esp, %edi
+       movl    %edi, %ecx
+       andl    $~0x1000, %edi
+       subl    %edi, %ecx

ecx will be equal to ?

+       movb    $'Q', %al
+       rep     stosb
--
vda
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