4 files changed, 26 insertions, 88 deletions

diff --git a/arch/arm/oprofile/backtrace.c b/arch/arm/oprofile/backtrace.c
index df35c452a8bf..7c22c12618cc 100644
--- a/arch/arm/oprofile/backtrace.c
+++ b/arch/arm/oprofile/backtrace.c
@@ -49,42 +49,22 @@ static struct frame_tail* kernel_backtrace(struct frame_tail *tail)
 
 static struct frame_tail* user_backtrace(struct frame_tail *tail)
 {
-        struct frame_tail buftail;
+        struct frame_tail buftail[2];
 
-        /* hardware pte might not be valid due to dirty/accessed bit emulation
-         * so we use copy_from_user and benefit from exception fixups */
-        if (copy_from_user(&buftail, tail, sizeof(struct frame_tail)))
+        /* Also check accessibility of one struct frame_tail beyond */
+        if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
+                return NULL;
+        if (__copy_from_user_inatomic(buftail, tail, sizeof(buftail)))
                 return NULL;
 
-        oprofile_add_trace(buftail.lr);
+        oprofile_add_trace(buftail[0].lr);
 
         /* frame pointers should strictly progress back up the stack
          * (towards higher addresses) */
-        if (tail >= buftail.fp)
+        if (tail >= buftail[0].fp)
                 return NULL;
 
-        return buftail.fp-1;
-}
-
-/* Compare two addresses and see if they're on the same page */
-#define CMP_ADDR_EQUAL(x,y,offset) ((((unsigned long) x) >> PAGE_SHIFT) \
-        == ((((unsigned long) y) + offset) >> PAGE_SHIFT))
-
-/* check that the page(s) containing the frame tail are present */
-static int pages_present(struct frame_tail *tail)
-{
-        struct mm_struct * mm = current->mm;
-
-        if (!check_user_page_readable(mm, (unsigned long)tail))
-                return 0;
-
-        if (CMP_ADDR_EQUAL(tail, tail, 8))
-                return 1;
-
-        if (!check_user_page_readable(mm, ((unsigned long)tail) + 8))
-                return 0;
-
-        return 1;
+        return buftail[0].fp-1;
 }
 
 /*
@@ -118,7 +98,6 @@ static int valid_kernel_stack(struct frame_tail *tail, struct pt_regs *regs)
 void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
 {
         struct frame_tail *tail;
-        unsigned long last_address = 0;
 
         tail = ((struct frame_tail *) regs->ARM_fp) - 1;
 
@@ -132,13 +111,6 @@ void arm_backtrace(struct pt_regs * const regs, unsigned int depth)
                 return;
         }
 
-        while (depth-- && tail && !((unsigned long) tail & 3)) {
-                if ((!CMP_ADDR_EQUAL(last_address, tail, 0)
-                        || !CMP_ADDR_EQUAL(last_address, tail, 8))
-                                && !pages_present(tail))
-                        return;
-                last_address = (unsigned long) tail;
+        while (depth-- && tail && !((unsigned long) tail & 3))
                 tail = user_backtrace(tail);
-        }
 }
-
diff --git a/arch/i386/oprofile/backtrace.c b/arch/i386/oprofile/backtrace.c
index 65dfd2edb671..21654be3f73f 100644
--- a/arch/i386/oprofile/backtrace.c
+++ b/arch/i386/oprofile/backtrace.c
@@ -12,6 +12,7 @@
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <asm/ptrace.h>
+#include <asm/uaccess.h>
 
 struct frame_head {
         struct frame_head * ebp;
@@ -21,26 +22,22 @@ struct frame_head {
 static struct frame_head *
 dump_backtrace(struct frame_head * head)
 {
-        oprofile_add_trace(head->ret);
+        struct frame_head bufhead[2];
 
-        /* frame pointers should strictly progress back up the stack
-         * (towards higher addresses) */
-        if (head >= head->ebp)
+        /* Also check accessibility of one struct frame_head beyond */
+        if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
+                return NULL;
+        if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
                 return NULL;
 
-        return head->ebp;
-}
-
-/* check that the page(s) containing the frame head are present */
-static int pages_present(struct frame_head * head)
-{
-        struct mm_struct * mm = current->mm;
+        oprofile_add_trace(bufhead[0].ret);
 
-        /* FIXME: only necessary once per page */
-        if (!check_user_page_readable(mm, (unsigned long)head))
-                return 0;
+        /* frame pointers should strictly progress back up the stack
+         * (towards higher addresses) */
+        if (head >= bufhead[0].ebp)
+                return NULL;
 
-        return check_user_page_readable(mm, (unsigned long)(head + 1));
+        return bufhead[0].ebp;
 }
 
 /*
@@ -97,15 +94,6 @@ x86_backtrace(struct pt_regs * const regs, unsigned int depth)
                 return;
         }
 
-#ifdef CONFIG_SMP
-        if (!spin_trylock(&current->mm->page_table_lock))
-                return;
-#endif
-
-        while (depth-- && head && pages_present(head))
+        while (depth-- && head)
                 head = dump_backtrace(head);
-
-#ifdef CONFIG_SMP
-        spin_unlock(&current->mm->page_table_lock);
-#endif
 }
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 972e2ce8e07c..aa8de20e2e80 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -944,7 +944,6 @@ extern struct page * vmalloc_to_page(void *addr);
 extern unsigned long vmalloc_to_pfn(void *addr);
 extern struct page * follow_page(struct mm_struct *mm, unsigned long address,
                 int write);
-extern int check_user_page_readable(struct mm_struct *mm, unsigned long address);
 int remap_pfn_range(struct vm_area_struct *, unsigned long,
                 unsigned long, unsigned long, pgprot_t);
 
diff --git a/mm/memory.c b/mm/memory.c
index 622a4ef5409f..51f7c0a220d4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -809,8 +809,7 @@ unsigned long zap_page_range(struct vm_area_struct *vma, unsigned long address,
  * Do a quick page-table lookup for a single page.
  * mm->page_table_lock must be held.
  */
-static struct page *__follow_page(struct mm_struct *mm, unsigned long address,
-                        int read, int write, int accessed)
+struct page *follow_page(struct mm_struct *mm, unsigned long address, int write)
 {
         pgd_t *pgd;
         pud_t *pud;
@@ -846,16 +845,12 @@ static struct page *__follow_page(struct mm_struct *mm, unsigned long address,
         if (pte_present(pte)) {
                 if (write && !pte_write(pte))
                         goto out;
-                if (read && !pte_read(pte))
-                        goto out;
                 pfn = pte_pfn(pte);
                 if (pfn_valid(pfn)) {
                         page = pfn_to_page(pfn);
-                        if (accessed) {
-                                if (write && !pte_dirty(pte) &&!PageDirty(page))
-                                        set_page_dirty(page);
-                                mark_page_accessed(page);
-                        }
+                        if (write && !pte_dirty(pte) &&!PageDirty(page))
+                                set_page_dirty(page);
+                        mark_page_accessed(page);
                         return page;
                 }
         }
@@ -864,22 +859,6 @@ out:
         return NULL;
 }
 
-inline struct page *
-follow_page(struct mm_struct *mm, unsigned long address, int write)
-{
-        return __follow_page(mm, address, 0, write, 1);
-}
-
-/*
- * check_user_page_readable() can be called frm niterrupt context by oprofile,
- * so we need to avoid taking any non-irq-safe locks
- */
-int check_user_page_readable(struct mm_struct *mm, unsigned long address)
-{
-        return __follow_page(mm, address, 1, 0, 0) != NULL;
-}
-EXPORT_SYMBOL(check_user_page_readable);
-
 static inline int
 untouched_anonymous_page(struct mm_struct* mm, struct vm_area_struct *vma,
                          unsigned long address)