Re: x86: PIE support and option to extend KASLR randomization

* Thomas Garnier [off-list ref] wrote:

Changes:
 - v2:
   - Add support for global stack cookie while compiler default to fs without
     mcmodel=kernel
   - Change patch 7 to correctly jump out of the identity mapping on kexec load
     preserve.

These patches make the changes necessary to build the kernel as Position
Independent Executable (PIE) on x86_64. A PIE kernel can be relocated below
the top 2G of the virtual address space. It allows to optionally extend the
KASLR randomization range from 1G to 3G.

So this:

 61 files changed, 923 insertions(+), 299 deletions(-)

... is IMHO an _awful_ lot of churn and extra complexity in pretty fragile pieces 
of code, to gain what appears to be only ~1.5 more bits of randomization!

Do these changes get us closer to being able to build the kernel as truly position 
independent, i.e. to place it anywhere in the valid x86-64 address space? Or any 
other advantages?

Thanks,

	Ingo