uml: clean up TASK_SIZE usage

Clean up the calculation and use of the usable address space size on the host.

task_size is gone, replaced with TASK_SIZE, which is calculated from
CONFIG_TOP_ADDR.  get_kmem_end and set_task_sizes_skas are also gone.

host_task_size, which refers to the entire address space usable by the UML
kernel and which may be larger than the address space usable by a UML process,
since that has to end on a pgdir boundary, is replaced by CONFIG_TOP_ADDR.

STACK_TOP is now TASK_SIZE minus the two stub pages.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 16 insertions, 6 deletions

diff --git a/arch/um/include/as-layout.h b/arch/um/include/as-layout.h
index 2b859e020ac6..a2008f550fee 100644
--- a/arch/um/include/as-layout.h
+++ b/arch/um/include/as-layout.h
@@ -29,9 +29,20 @@
 #define _AC(X, Y)       __AC(X, Y)
 #endif
 
+/*
+ * The "- 1"'s are to avoid gcc complaining about integer overflows
+ * and unrepresentable decimal constants.  With 3-level page tables,
+ * TASK_SIZE is 0x80000000, which gets turned into its signed decimal
+ * equivalent in asm-offsets.s.  gcc then complains about that being
+ * unsigned only in C90.  To avoid that, UM_TASK_SIZE is defined as
+ * TASK_SIZE - 1.  To compensate, we need to add the 1 back here.
+ * However, adding it back to UM_TASK_SIZE produces more gcc
+ * complaints.  So, I adjust the thing being subtracted from
+ * UM_TASK_SIZE instead.  Bah.
+ */
 #define STUB_CODE _AC((unsigned long), \
-                      UML_CONFIG_TOP_ADDR - 2 * UM_KERN_PAGE_SIZE)
-#define STUB_DATA _AC((unsigned long), UML_CONFIG_TOP_ADDR - UM_KERN_PAGE_SIZE)
+                      UM_TASK_SIZE - (2 * UM_KERN_PAGE_SIZE - 1))
+#define STUB_DATA _AC((unsigned long), UM_TASK_SIZE - (UM_KERN_PAGE_SIZE - 1))
 #define STUB_START _AC(, STUB_CODE)
 
 #ifndef __ASSEMBLY__
diff --git a/arch/um/include/common-offsets.h b/arch/um/include/common-offsets.h
index b54bd35585c2..5b67d7ced2a7 100644
--- a/arch/um/include/common-offsets.h
+++ b/arch/um/include/common-offsets.h
@@ -39,3 +39,6 @@ DEFINE(UM_HZ, HZ);
 DEFINE(UM_USEC_PER_SEC, USEC_PER_SEC);
 DEFINE(UM_NSEC_PER_SEC, NSEC_PER_SEC);
 DEFINE(UM_NSEC_PER_USEC, NSEC_PER_USEC);
+
+/* See as-layout.h for an explanation of the "- 1".  Bah. */
+DEFINE(UM_TASK_SIZE, TASK_SIZE - 1);
diff --git a/arch/um/include/mem_user.h b/arch/um/include/mem_user.h
index a54514d2cc3a..4e6707bd0a08 100644
--- a/arch/um/include/mem_user.h
+++ b/arch/um/include/mem_user.h
@@ -46,9 +46,6 @@ extern int iomem_size;
 
 #define ROUND_4M(n) ((((unsigned long) (n)) + (1 << 22)) & ~((1 << 22) - 1))
 
-extern unsigned long host_task_size;
-extern unsigned long task_size;
-
 extern int init_mem_user(void);
 extern void setup_memory(void *entry);
 extern unsigned long find_iomem(char *driver, unsigned long *len_out);
@@ -62,6 +59,5 @@ extern unsigned long phys_offset(unsigned long phys);
 extern void unmap_physmem(void);
 extern void map_memory(unsigned long virt, unsigned long phys,
                        unsigned long len, int r, int w, int x);
-extern unsigned long get_kmem_end(void);
 
 #endif