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);
+        }
+}