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Kernel address randomization

Kernel address randomization

Posted May 26, 2011 7:14 UTC (Thu) by dlang (subscriber, #313)
In reply to: Kernel address randomization by jonabbey
Parent article: Kernel address randomization

no, 32 bit has very little flexibility, this is the gains for 64 bit systems


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Kernel address randomization

Posted May 27, 2011 22:38 UTC (Fri) by PaXTeam (guest, #24616) [Link]

i386 kernels have 1/2/3GB of kernel space to play with (minus vmalloc/fixmap/gaps/etc), amd64 kernels have 2GB (minus vsyscall/module area/etc). so for practical purposes, you could get the same amount of entropy for both cases.

Kernel address randomization

Posted May 27, 2011 22:49 UTC (Fri) by dlang (subscriber, #313) [Link]

the issue is that that 1/2/3G of kernel space is in a total of 4G of address space, and given the size of the kernel and the alignment requirements, things are a bit limited

on amd64 you have much more address space to work with, so that 2G of kernel space can be moved to far more locations

Kernel address randomization

Posted May 28, 2011 22:13 UTC (Sat) by PaXTeam (guest, #24616) [Link]

> the issue is that that 1/2/3G of kernel space is in a total of 4G of
> address space, and given the size of the kernel and the alignment
> requirements, things are a bit limited

the exact same limits apply to amd64 kernels as well.

> on amd64 you have much more address space to work with, so that 2G of
> kernel space can be moved to far more locations

you're wrong, the kernel image cannot be at arbitrary addresses, it *must* be in the top 2GB of the 64 bit virtual address space. i suggest you study the amd64 ABI and in particular -mcmodel=kernel.


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