arm64: place kernel in its own L0 page table entry

Kernel text replication needs to maintain separate per-node page
tables for the kernel text. In order to do this without affecting
other kernel memory mappings, placing the kernel such that it does
not share a L0 page table entry with any other mapping is desirable.

Prior to this commit, the layout without KASLR was:

+----------+
|  vmalloc |
+----------+
|  Kernel  |
+----------+ MODULES_END, VMALLOC_START, KIMAGE_VADDR =
|  Modules |                 MODULES_VADDR + MODULES_VSIZE
+----------+ MODULES_VADDR = _PAGE_END(VA_BITS_MIN)
| VA space |
+----------+ 0

This becomes:

+----------+
|  vmalloc |
+----------+ VMALLOC_START = MODULES_END + PGDIR_SIZE
|  Kernel  |
+----------+ MODULES_END, KIMAGE_VADDR = _PAGE_END(VA_BITS_MIN) + PGDIR_SIZE
|  Modules |
+----------+ MODULES_VADDR = MODULES_END - MODULES_VSIZE
| VA space |
+----------+ 0

This assumes MODULES_VSIZE (128M) <= PGDIR_SIZE.

One side effect of this change is that KIMAGE_VADDR's definition now
includes PGDIR_SIZE (to leave room for the modules) but this is not
defined when asm/memory.h is included. This means KIMAGE_VADDR can
not be used in inline functions within this file, so we convert
kaslr_offset() and kaslr_enabled() to be macros instead.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

0 files changed, 0 insertions, 0 deletions