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>

1 files changed, 0 insertions, 37 deletions

diff --git a/arch/um/Kconfig.i386 b/arch/um/Kconfig.i386
index e752646..3cd8a04 100644
--- a/arch/um/Kconfig.i386
+++ b/arch/um/Kconfig.i386
@@ -23,43 +23,6 @@ config SEMAPHORE_SLEEPERS
 	bool
 	default y
 
-choice
-	prompt "Host memory split"
-	default HOST_VMSPLIT_3G
-	help
-        This is needed when the host kernel on which you run has a non-default
-	(like 2G/2G) memory split, instead of the customary 3G/1G. If you did
-	not recompile your own kernel but use the default distro's one, you can
-	safely accept the "Default split" option.
-
-	It can be enabled on recent (>=2.6.16-rc2) vanilla kernels via
-	CONFIG_VM_SPLIT_*, or on previous kernels with special patches (-ck
-	patchset by Con Kolivas, or other ones) - option names match closely the
-	host CONFIG_VM_SPLIT_* ones.
-
-	A lower setting (where 1G/3G is lowest and 3G/1G is higher) will
-	tolerate even more "normal" host kernels, but an higher setting will be
-	stricter.
-
-	So, if you do not know what to do here, say 'Default split'.
-
-config HOST_VMSPLIT_3G
-	bool "Default split (3G/1G user/kernel host split)"
-config HOST_VMSPLIT_3G_OPT
-	bool "3G/1G user/kernel host split (for full 1G low memory)"
-config HOST_VMSPLIT_2G
-	bool "2G/2G user/kernel host split"
-config HOST_VMSPLIT_1G
-	bool "1G/3G user/kernel host split"
-endchoice
-
-config TOP_ADDR
-	hex
-	default 0xB0000000 if HOST_VMSPLIT_3G_OPT
-	default 0x78000000 if HOST_VMSPLIT_2G
-	default 0x40000000 if HOST_VMSPLIT_1G
-	default 0xC0000000
-
 config 3_LEVEL_PGTABLES
 	bool "Three-level pagetables (EXPERIMENTAL)"
 	default n