linux/arch/um/Kconfig.i386
Jeff Dike 536788fe2d uml: runtime host VMSPLIT detection
Calculate TASK_SIZE at run-time by figuring out the host's VMSPLIT - this is
needed on i386 if UML is to run on hosts with varying VMSPLITs without
recompilation.

TASK_SIZE is now defined in terms of a variable, task_size.  This gets rid of
an include of pgtable.h from processor.h, which can cause include loops.

On i386, task_size is calculated early in boot by probing the address space in
a binary search to figure out where the boundary between usable and non-usable
memory is.  This tries to make sure that a page that is considered to be in
userspace is, or can be made, read-write.  I'm concerned about a system-global
VDSO page in kernel memory being hit and considered to be a userspace page.

On x86_64, task_size is just the old value of CONFIG_TOP_ADDR.

A bunch of config variable are gone now.  CONFIG_TOP_ADDR is directly replaced
by TASK_SIZE.  NEST_LEVEL is gone since the relocation of the stubs makes it
irrelevant.  All the HOST_VMSPLIT stuff is gone.  All references to these in
arch/um/Makefile are also gone.

I noticed and fixed a missing extern in os.h when adding os_get_task_size.

Note: This has been revised to fix the 32-bit UML on 64-bit host bug that
Miklos ran into.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:42 -08:00

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menu "Host processor type and features"
source "arch/x86/Kconfig.cpu"
endmenu
config UML_X86
bool
default y
config X86_32
bool
default y
config RWSEM_XCHGADD_ALGORITHM
def_bool y
config 64BIT
bool
default n
config SEMAPHORE_SLEEPERS
bool
default y
config 3_LEVEL_PGTABLES
bool "Three-level pagetables (EXPERIMENTAL)"
default n
depends on EXPERIMENTAL
help
Three-level pagetables will let UML have more than 4G of physical
memory. All the memory that can't be mapped directly will be treated
as high memory.
However, this it experimental on 32-bit architectures, so if unsure say
N (on x86-64 it's automatically enabled, instead, as it's safe there).
config ARCH_HAS_SC_SIGNALS
bool
default y
config ARCH_REUSE_HOST_VSYSCALL_AREA
bool
default y
config GENERIC_HWEIGHT
bool
default y
config ARCH_SUPPORTS_AOUT
def_bool y