Aggressively randomize the location of the stack on all 64-bit architectures
except alpha. This will put the stack at a random location in the upper
1/4th of the userland virtual address space provi

Aggressively randomize the location of the stack on all 64-bit architectures
except alpha. This will put the stack at a random location in the upper
1/4th of the userland virtual address space providing up to 26 additional
bits of randomness in the address. Skip alpha for now since it currently
puts the stack at a (for a 64-bit architecture) very low address. Skip
32-bit architectures for now as well since those have a much smaller
virtual address space and we need more time to figure out what a safe
amount of extra randomizations is. These architectures will continue to
use a mildly randomized stack address through the existing stackgap random
mechanism. We will revisit this after 7.3 is released.

This should make it harder for an attacker to find the stack.

ok deraadt@, miod@

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Double the maximum data size limit on powerpc64. Now it is 32 GB
and the same as amd64. The machines have large amounts of memory.
discussed with kettenis@

Implement spilling of kernel SLB entries. Mostly from FreeBSD.

This makes it possible to use more SLB entries for the kernel than the
hardware supports. The design is such that a subset of the har

Implement spilling of kernel SLB entries. Mostly from FreeBSD.

This makes it possible to use more SLB entries for the kernel than the
hardware supports. The design is such that a subset of the hardware SLB
entries can be replaced when needed. This makes sure the entries
mapping kernel code and data and the page tables ar always present.
Traps for missing SLB entries are handled in real-mode and on a special
stack such that it doesn't have to rely on SLB entires mapping kernel
stacks.

With this in place we can increase KVA to 32GB. Hopefully that's enough
to support large memory configurations.

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Make the kernel address space a bit bigger.

Set up exec_map and phys_map.

VM_MAXUSER_ADDRESS needs to be page-aligned.

Bootstrap a kernel pmap and enable translations.

Hand those pages over to uvm.

Planting the first seed for OpenBSD/powerpc64.