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>
diff --git a/include/asm-um/processor-generic.h b/include/asm-um/processor-generic.h
index 7a1624c..bed6688 100644
--- a/include/asm-um/processor-generic.h
+++ b/include/asm-um/processor-generic.h
@@ -11,7 +11,6 @@
struct task_struct;
#include "asm/ptrace.h"
-#include "asm/pgtable.h"
#include "registers.h"
#include "sysdep/archsetjmp.h"
@@ -92,7 +91,9 @@
/*
* User space process size: 3GB (default).
*/
-#define TASK_SIZE (CONFIG_TOP_ADDR & PGDIR_MASK)
+extern unsigned long task_size;
+
+#define TASK_SIZE (task_size)
#undef STACK_TOP
#undef STACK_TOP_MAX