[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/kernel/skas/include/skas.h

@@ -33,7 +33,7 @@ extern int protect(struct mm_id * mm_idp, unsigned long addr,
 		   unsigned long len, int r, int w, int x, int done,
 		   void **data);
 extern void user_signal(int sig, union uml_pt_regs *regs, int pid);
-extern int new_mm(int from, unsigned long stack);
+extern int new_mm(unsigned long stack);
 extern int start_userspace(unsigned long stub_stack);
 extern int copy_context_skas0(unsigned long stack, int pid);
 extern void get_skas_faultinfo(int pid, struct faultinfo * fi);

arch/um/kernel/skas/mmu.c

@@ -78,7 +78,7 @@ int init_new_context_skas(struct task_struct *task, struct mm_struct *mm)
  	struct mmu_context_skas *from_mm = NULL;
 	struct mmu_context_skas *to_mm = &mm->context.skas;
 	unsigned long stack = 0;
-	int from_fd, ret = -ENOMEM;
+	int ret = -ENOMEM;
 
 	if(skas_needs_stub){
 		stack = get_zeroed_page(GFP_KERNEL);
@@ -108,11 +108,7 @@ int init_new_context_skas(struct task_struct *task, struct mm_struct *mm)
 		from_mm = &current->mm->context.skas;
 
 	if(proc_mm){
-		if(from_mm)
-			from_fd = from_mm->id.u.mm_fd;
-		else from_fd = -1;
-
-		ret = new_mm(from_fd, stack);
+		ret = new_mm(stack);
 		if(ret < 0){
 			printk("init_new_context_skas - new_mm failed, "
 			       "errno = %d\n", ret);

arch/um/kernel/skas/process_kern.c

@@ -20,7 +20,6 @@
 #include "tlb.h"
 #include "kern.h"
 #include "mode.h"
-#include "proc_mm.h"
 #include "registers.h"
 
 void switch_to_skas(void *prev, void *next)
@@ -125,25 +124,14 @@ int copy_thread_skas(int nr, unsigned long clone_flags, unsigned long sp,
 
 extern void map_stub_pages(int fd, unsigned long code,
 			   unsigned long data, unsigned long stack);
-int new_mm(int from, unsigned long stack)
+int new_mm(unsigned long stack)
 {
-	struct proc_mm_op copy;
-	int n, fd;
+	int fd;
 
 	fd = os_open_file("/proc/mm", of_cloexec(of_write(OPENFLAGS())), 0);
 	if(fd < 0)
 		return(fd);
 
-	if(from != -1){
-		copy = ((struct proc_mm_op) { .op 	= MM_COPY_SEGMENTS,
-					      .u 	=
-					      { .copy_segments	= from } } );
-		n = os_write_file(fd, &copy, sizeof(copy));
-		if(n != sizeof(copy))
-			printk("new_mm : /proc/mm copy_segments failed, "
-			       "err = %d\n", -n);
-	}
-
 	if(skas_needs_stub)
 		map_stub_pages(fd, CONFIG_STUB_CODE, CONFIG_STUB_DATA, stack);
 

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;
 }