4 files changed, 26 insertions, 88 deletions

diff --git a/arch/arm/oprofile/backtrace.c b/arch/arm/oprofile/backtrace.c
index df35c452a8b..7c22c12618c 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 65dfd2edb67..21654be3f73 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 972e2ce8e07..aa8de20e2e8 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 622a4ef5409..51f7c0a220d 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)