1 files changed, 114 insertions, 22 deletions

diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index 6cb9a6d028a9..511a855c9ec0 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -3,46 +3,138 @@
  * Licensed under the GPL
  */
 
+#include "linux/config.h"
 #include "linux/sched.h"
 #include "linux/list.h"
 #include "linux/spinlock.h"
 #include "linux/slab.h"
+#include "linux/errno.h"
+#include "linux/mm.h"
 #include "asm/current.h"
 #include "asm/segment.h"
 #include "asm/mmu.h"
+#include "asm/pgalloc.h"
+#include "asm/pgtable.h"
 #include "os.h"
 #include "skas.h"
 
+extern int __syscall_stub_start;
+
+static int init_stub_pte(struct mm_struct *mm, unsigned long proc,
+			 unsigned long kernel)
+{
+	pgd_t *pgd;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+
+	spin_lock(&mm->page_table_lock);
+	pgd = pgd_offset(mm, proc);
+	pud = pud_alloc(mm, pgd, proc);
+	if (!pud)
+		goto out;
+
+	pmd = pmd_alloc(mm, pud, proc);
+	if (!pmd)
+		goto out_pmd;
+
+	pte = pte_alloc_map(mm, pmd, proc);
+	if (!pte)
+		goto out_pte;
+
+	/* There's an interaction between the skas0 stub pages, stack
+	 * randomization, and the BUG at the end of exit_mmap.  exit_mmap
+         * checks that the number of page tables freed is the same as had
+         * been allocated.  If the stack is on the last page table page,
+	 * then the stack pte page will be freed, and if not, it won't.  To
+	 * avoid having to know where the stack is, or if the process mapped
+	 * something at the top of its address space for some other reason,
+	 * we set TASK_SIZE to end at the start of the last page table.
+	 * This keeps exit_mmap off the last page, but introduces a leak
+	 * of that page.  So, we hang onto it here and free it in
+	 * destroy_context_skas.
+	 */
+
+        mm->context.skas.last_page_table = pmd_page_kernel(*pmd);
+
+	*pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
+	*pte = pte_mkexec(*pte);
+	*pte = pte_wrprotect(*pte);
+	spin_unlock(&mm->page_table_lock);
+	return(0);
+
+ out_pmd:
+	pud_free(pud);
+ out_pte:
+	pmd_free(pmd);
+ out:
+	spin_unlock(&mm->page_table_lock);
+	return(-ENOMEM);
+}
+
 int init_new_context_skas(struct task_struct *task, struct mm_struct *mm)
 {
-	int from;
+	struct mm_struct *cur_mm = current->mm;
+	struct mm_id *mm_id = &mm->context.skas.id;
+	unsigned long stack;
+	int from, ret;
 
-	if((current->mm != NULL) && (current->mm != &init_mm))
-		from = current->mm->context.skas.mm_fd;
-	else from = -1;
+	if(proc_mm){
+		if((cur_mm != NULL) && (cur_mm != &init_mm))
+			from = cur_mm->context.skas.id.u.mm_fd;
+		else from = -1;
 
-	mm->context.skas.mm_fd = new_mm(from);
-	if(mm->context.skas.mm_fd < 0){
-		printk("init_new_context_skas - new_mm failed, errno = %d\n",
-		       mm->context.skas.mm_fd);
-		return(mm->context.skas.mm_fd);
+		ret = new_mm(from);
+		if(ret < 0){
+			printk("init_new_context_skas - new_mm failed, "
+			       "errno = %d\n", ret);
+			return ret;
+		}
+		mm_id->u.mm_fd = ret;
 	}
+	else {
+		/* This zeros the entry that pgd_alloc didn't, needed since
+		 * we are about to reinitialize it, and want mm.nr_ptes to
+		 * be accurate.
+		 */
+		mm->pgd[USER_PTRS_PER_PGD] = __pgd(0);
 
-	return(0);
+		ret = init_stub_pte(mm, CONFIG_STUB_CODE,
+				    (unsigned long) &__syscall_stub_start);
+		if(ret)
+			goto out;
+
+		ret = -ENOMEM;
+		stack = get_zeroed_page(GFP_KERNEL);
+		if(stack == 0)
+			goto out;
+		mm_id->stack = stack;
+
+		ret = init_stub_pte(mm, CONFIG_STUB_DATA, stack);
+		if(ret)
+			goto out_free;
+
+		mm->nr_ptes--;
+		mm_id->u.pid = start_userspace(stack);
+	}
+
+	return 0;
+
+ out_free:
+	free_page(mm_id->stack);
+ out:
+	return ret;
 }
 
 void destroy_context_skas(struct mm_struct *mm)
 {
-	os_close_file(mm->context.skas.mm_fd);
-}
+	struct mmu_context_skas *mmu = &mm->context.skas;
 
-/*
- * Overrides for Emacs so that we follow Linus's tabbing style.
- * Emacs will notice this stuff at the end of the file and automatically
- * adjust the settings for this buffer only.  This must remain at the end
- * of the file.
- * ---------------------------------------------------------------------------
- * Local variables:
- * c-file-style: "linux"
- * End:
- */
+	if(proc_mm)
+		os_close_file(mmu->id.u.mm_fd);
+	else {
+		os_kill_ptraced_process(mmu->id.u.pid, 1);
+		free_page(mmu->id.stack);
+		free_page(mmu->last_page_table);
+	}
+}