1 files changed, 173 insertions, 24 deletions

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index ae3c20a..302d779 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -6,32 +6,77 @@
  * Copyright (C) 2011 Wind River Systems,
  *   written by Ralf Baechle <ralf@linux-mips.org>
  */
+#include <linux/compiler.h>
 #include <linux/errno.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/module.h>
+#include <linux/personality.h>
 #include <linux/random.h>
 #include <linux/sched.h>
 
 unsigned long shm_align_mask = PAGE_SIZE - 1;	/* Sane caches */
-
 EXPORT_SYMBOL(shm_align_mask);
 
-#define COLOUR_ALIGN(addr,pgoff)				\
+/* gap between mmap and stack */
+#define MIN_GAP (128*1024*1024UL)
+#define MAX_GAP ((TASK_SIZE)/6*5)
+
+static int mmap_is_legacy(void)
+{
+	if (current->personality & ADDR_COMPAT_LAYOUT)
+		return 1;
+
+	if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
+		return 1;
+
+	return sysctl_legacy_va_layout;
+}
+
+static unsigned long mmap_base(unsigned long rnd)
+{
+	unsigned long gap = rlimit(RLIMIT_STACK);
+
+	if (gap < MIN_GAP)
+		gap = MIN_GAP;
+	else if (gap > MAX_GAP)
+		gap = MAX_GAP;
+
+	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+}
+
+static inline unsigned long COLOUR_ALIGN_DOWN(unsigned long addr,
+					      unsigned long pgoff)
+{
+	unsigned long base = addr & ~shm_align_mask;
+	unsigned long off = (pgoff << PAGE_SHIFT) & shm_align_mask;
+
+	if (base + off <= addr)
+		return base + off;
+
+	return base - off;
+}
+
+#define COLOUR_ALIGN(addr, pgoff)				\
 	((((addr) + shm_align_mask) & ~shm_align_mask) +	\
 	 (((pgoff) << PAGE_SHIFT) & shm_align_mask))
 
-unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
-	unsigned long len, unsigned long pgoff, unsigned long flags)
+enum mmap_allocation_direction {UP, DOWN};
+
+static unsigned long arch_get_unmapped_area_common(struct file *filp,
+	unsigned long addr0, unsigned long len, unsigned long pgoff,
+	unsigned long flags, enum mmap_allocation_direction dir)
 {
-	struct vm_area_struct * vmm;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	unsigned long addr = addr0;
 	int do_color_align;
 
-	if (len > TASK_SIZE)
+	if (unlikely(len > TASK_SIZE))
 		return -ENOMEM;
 
 	if (flags & MAP_FIXED) {
-		/* Even MAP_FIXED mappings must reside within TASK_SIZE.  */
+		/* Even MAP_FIXED mappings must reside within TASK_SIZE */
 		if (TASK_SIZE - len < addr)
 			return -EINVAL;
 
@@ -48,34 +93,132 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
 	do_color_align = 0;
 	if (filp || (flags & MAP_SHARED))
 		do_color_align = 1;
+
+	/* requesting a specific address */
 	if (addr) {
 		if (do_color_align)
 			addr = COLOUR_ALIGN(addr, pgoff);
 		else
 			addr = PAGE_ALIGN(addr);
-		vmm = find_vma(current->mm, addr);
+
+		vma = find_vma(mm, addr);
 		if (TASK_SIZE - len >= addr &&
-		    (!vmm || addr + len <= vmm->vm_start))
+		    (!vma || addr + len <= vma->vm_start))
 			return addr;
 	}
-	addr = current->mm->mmap_base;
-	if (do_color_align)
-		addr = COLOUR_ALIGN(addr, pgoff);
-	else
-		addr = PAGE_ALIGN(addr);
 
-	for (vmm = find_vma(current->mm, addr); ; vmm = vmm->vm_next) {
-		/* At this point:  (!vmm || addr < vmm->vm_end). */
-		if (TASK_SIZE - len < addr)
-			return -ENOMEM;
-		if (!vmm || addr + len <= vmm->vm_start)
-			return addr;
-		addr = vmm->vm_end;
+	if (dir == UP) {
+		addr = mm->mmap_base;
 		if (do_color_align)
 			addr = COLOUR_ALIGN(addr, pgoff);
+		else
+			addr = PAGE_ALIGN(addr);
+
+		for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
+			/* At this point:  (!vma || addr < vma->vm_end). */
+			if (TASK_SIZE - len < addr)
+				return -ENOMEM;
+			if (!vma || addr + len <= vma->vm_start)
+				return addr;
+			addr = vma->vm_end;
+			if (do_color_align)
+				addr = COLOUR_ALIGN(addr, pgoff);
+		 }
+	 } else {
+		/* check if free_area_cache is useful for us */
+		if (len <= mm->cached_hole_size) {
+			mm->cached_hole_size = 0;
+			mm->free_area_cache = mm->mmap_base;
+		}
+
+		/*
+		 * either no address requested, or the mapping can't fit into
+		 * the requested address hole
+		 */
+		addr = mm->free_area_cache;
+		if (do_color_align) {
+			unsigned long base =
+				COLOUR_ALIGN_DOWN(addr - len, pgoff);
+			addr = base + len;
+		}
+
+		/* make sure it can fit in the remaining address space */
+		if (likely(addr > len)) {
+			vma = find_vma(mm, addr - len);
+			if (!vma || addr <= vma->vm_start) {
+				/* cache the address as a hint for next time */
+				return mm->free_area_cache = addr - len;
+			}
+		}
+
+		if (unlikely(mm->mmap_base < len))
+			goto bottomup;
+
+		addr = mm->mmap_base - len;
+		if (do_color_align)
+			addr = COLOUR_ALIGN_DOWN(addr, pgoff);
+
+		do {
+			/*
+			 * Lookup failure means no vma is above this address,
+			 * else if new region fits below vma->vm_start,
+			 * return with success:
+			 */
+			vma = find_vma(mm, addr);
+			if (likely(!vma || addr + len <= vma->vm_start)) {
+				/* cache the address as a hint for next time */
+				return mm->free_area_cache = addr;
+			}
+
+			/* remember the largest hole we saw so far */
+			if (addr + mm->cached_hole_size < vma->vm_start)
+				mm->cached_hole_size = vma->vm_start - addr;
+
+			/* try just below the current vma->vm_start */
+			addr = vma->vm_start - len;
+			if (do_color_align)
+				addr = COLOUR_ALIGN_DOWN(addr, pgoff);
+		} while (likely(len < vma->vm_start));
+
+bottomup:
+		/*
+		 * A failed mmap() very likely causes application failure,
+		 * so fall back to the bottom-up function here. This scenario
+		 * can happen with large stack limits and large mmap()
+		 * allocations.
+		 */
+		mm->cached_hole_size = ~0UL;
+		mm->free_area_cache = TASK_UNMAPPED_BASE;
+		addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
+		/*
+		 * Restore the topdown base:
+		 */
+		mm->free_area_cache = mm->mmap_base;
+		mm->cached_hole_size = ~0UL;
+
+		return addr;
 	}
 }
 
+unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr0,
+	unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+	return arch_get_unmapped_area_common(filp,
+			addr0, len, pgoff, flags, UP);
+}
+
+/*
+ * There is no need to export this but sched.h declares the function as
+ * extern so making it static here results in an error.
+ */
+unsigned long arch_get_unmapped_area_topdown(struct file *filp,
+	unsigned long addr0, unsigned long len, unsigned long pgoff,
+	unsigned long flags)
+{
+	return arch_get_unmapped_area_common(filp,
+			addr0, len, pgoff, flags, DOWN);
+}
+
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
 	unsigned long random_factor = 0UL;
@@ -89,9 +232,15 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 			random_factor &= 0xffffffful;
 	}
 
-	mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
-	mm->get_unmapped_area = arch_get_unmapped_area;
-	mm->unmap_area = arch_unmap_area;
+	if (mmap_is_legacy()) {
+		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
+		mm->get_unmapped_area = arch_get_unmapped_area;
+		mm->unmap_area = arch_unmap_area;
+	} else {
+		mm->mmap_base = mmap_base(random_factor);
+		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+		mm->unmap_area = arch_unmap_area_topdown;
+	}
 }
 
 static inline unsigned long brk_rnd(void)