[PATCH] uml: move LDT creation

s390 doesn't have a LDT.  So MM_COPY_SEGMENTS will not be supported on s390.

The only user of MM_COPY_SEGMENTS is new_mm(), but that's no longer useful, as
arch/sys-i386/ldt.c defines init_new_ldt(), which is called immediately after
new_mm().  So we should copy host's LDT in init_new_ldt(), if /proc/mm is
available, to have this subarch specific call in subarch code.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/sys-i386/ldt.c

@@ -16,6 +16,8 @@
 #include "choose-mode.h"
 #include "kern.h"
 #include "mode_kern.h"
+#include "proc_mm.h"
+#include "os.h"
 
 extern int modify_ldt(int func, void *ptr, unsigned long bytecount);
 
@@ -456,13 +458,14 @@ long init_new_ldt(struct mmu_context_skas * new_mm,
 	int i;
 	long page, err=0;
 	void *addr = NULL;
+	struct proc_mm_op copy;
 
-	memset(&desc, 0, sizeof(desc));
 
 	if(!ptrace_ldt)
 		init_MUTEX(&new_mm->ldt.semaphore);
 
 	if(!from_mm){
+		memset(&desc, 0, sizeof(desc));
 		/*
 		 * We have to initialize a clean ldt.
 		 */
@@ -494,8 +497,26 @@ long init_new_ldt(struct mmu_context_skas * new_mm,
 			}
 		}
 		new_mm->ldt.entry_count = 0;
+
+		goto out;
 	}
-	else if (!ptrace_ldt) {
+
+	if(proc_mm){
+		/* We have a valid from_mm, so we now have to copy the LDT of
+		 * from_mm to new_mm, because using proc_mm an new mm with
+		 * an empty/default LDT was created in new_mm()
+		 */
+		copy = ((struct proc_mm_op) { .op 	= MM_COPY_SEGMENTS,
+					      .u 	=
+					      { .copy_segments =
+							from_mm->id.u.mm_fd } } );
+		i = os_write_file(new_mm->id.u.mm_fd, &copy, sizeof(copy));
+		if(i != sizeof(copy))
+			printk("new_mm : /proc/mm copy_segments failed, "
+			       "err = %d\n", -i);
+	}
+
+	if(!ptrace_ldt) {
 		/* Our local LDT is used to supply the data for
 		 * modify_ldt(READLDT), if PTRACE_LDT isn't available,
 		 * i.e., we have to use the stub for modify_ldt, which
@@ -524,6 +545,7 @@ long init_new_ldt(struct mmu_context_skas * new_mm,
 		up(&from_mm->ldt.semaphore);
 	}
 
+    out:
 	return err;
 }