New Features and APIs (fixmap support)

fixmap allows for reserving fixed virtual addresses at compile time.

Implemented in include/asm-sh/fixmap.h.
Prerequisite for vsyscall support.
Used by kmap PTEs for highmem support.
Fixmap space begins 1 page below P4SEG.
Fixmap grows down, while vmalloc grows up.
VMALLOC_END determined at compile time based on number of fixmap addresses.
Planned addition of _PAGE_WIRED flag.
Preserve fixmap translations across a context switch or TLB flush (at the cost of a TLB entry).
Implement similar wired entry API as sh64 (using memory mapped UTLB access).
Performance benefit for vsyscall page.

21-09-2004
Non confidential