uml: move um_virt_to_phys

This patchset makes UML build and run with three-level page tables on
32-bit hosts.  This is an uncommon use case, but the code here needed
fixing and cleaning up, so 32-bit three-level pages tables were tested
to make sure the changes are good.

Patch 1 - code movement
Patch 2 - header untangling
Patch 3 - style fixups in files affected so far
Patch 4 - clean up use of current.h
Patch 5 - fix sizes of types that are different between 2 and 3-level
	page tables - three-level page table support should build at
	this point
Patch 6 - tidy (i.e. eliminate much of) the code that figures out how
	big the address space is
Patch 7 - change um_virt_to_phys into virt_to_pte, clean its
	interface, and clean its (so far) one caller
Patch 8 - the stub pages are covered with a VMA, allowing some nasty
	code to be thrown out - three-level page tables now work

This patch:

um_virt_to_phys only has one user, so it can be moved to the same file
and made static.  Its declarations in pgtable.h and ksyms.c are also
gone.

current_cmd was another apparent user, but it itself isn't used, so it
is deleted.

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>

1 files changed, 32 insertions, 2 deletions

diff --git a/arch/um/kernel/skas/uaccess.c b/arch/um/kernel/skas/uaccess.c
index 1d8b119f2d0e..302425b03d49 100644
--- a/arch/um/kernel/skas/uaccess.c
+++ b/arch/um/kernel/skas/uaccess.c
@@ -12,8 +12,38 @@
 #include "kern_util.h"
 #include "os.h"
 
-extern void *um_virt_to_phys(struct task_struct *task, unsigned long addr,
-			     pte_t *pte_out);
+static void *um_virt_to_phys(struct task_struct *task, unsigned long addr,
+			     pte_t *pte_out)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	pte_t ptent;
+
+	if (task->mm == NULL)
+		return ERR_PTR(-EINVAL);
+	pgd = pgd_offset(task->mm, addr);
+	if (!pgd_present(*pgd))
+		return ERR_PTR(-EINVAL);
+
+	pud = pud_offset(pgd, addr);
+	if (!pud_present(*pud))
+		return ERR_PTR(-EINVAL);
+
+	pmd = pmd_offset(pud, addr);
+	if (!pmd_present(*pmd))
+		return ERR_PTR(-EINVAL);
+
+	pte = pte_offset_kernel(pmd, addr);
+	ptent = *pte;
+	if (!pte_present(ptent))
+		return ERR_PTR(-EINVAL);
+
+	if (pte_out != NULL)
+		*pte_out = ptent;
+	return (void *) (pte_val(ptent) & PAGE_MASK) + (addr & ~PAGE_MASK);
+}
 
 static unsigned long maybe_map(unsigned long virt, int is_write)
 {