diff --git a/Documentation/nommu-mmap.txt b/Documentation/nommu-mmap.txt
index b565e8279d1..8e1ddec2c78 100644
--- a/Documentation/nommu-mmap.txt
+++ b/Documentation/nommu-mmap.txt
@@ -119,6 +119,32 @@ FURTHER NOTES ON NO-MMU MMAP
      granule but will only discard the excess if appropriately configured as
      this has an effect on fragmentation.
 
+ (*) The memory allocated by a request for an anonymous mapping will normally
+     be cleared by the kernel before being returned in accordance with the
+     Linux man pages (ver 2.22 or later).
+
+     In the MMU case this can be achieved with reasonable performance as
+     regions are backed by virtual pages, with the contents only being mapped
+     to cleared physical pages when a write happens on that specific page
+     (prior to which, the pages are effectively mapped to the global zero page
+     from which reads can take place).  This spreads out the time it takes to
+     initialize the contents of a page - depending on the write-usage of the
+     mapping.
+
+     In the no-MMU case, however, anonymous mappings are backed by physical
+     pages, and the entire map is cleared at allocation time.  This can cause
+     significant delays during a userspace malloc() as the C library does an
+     anonymous mapping and the kernel then does a memset for the entire map.
+
+     However, for memory that isn't required to be precleared - such as that
+     returned by malloc() - mmap() can take a MAP_UNINITIALIZED flag to
+     indicate to the kernel that it shouldn't bother clearing the memory before
+     returning it.  Note that CONFIG_MMAP_ALLOW_UNINITIALIZED must be enabled
+     to permit this, otherwise the flag will be ignored.
+
+     uClibc uses this to speed up malloc(), and the ELF-FDPIC binfmt uses this
+     to allocate the brk and stack region.
+
  (*) A list of all the private copy and anonymous mappings on the system is
      visible through /proc/maps in no-MMU mode.
 
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 38502c67987..79d2b1aa389 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -380,7 +380,8 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm,
 	down_write(&current->mm->mmap_sem);
 	current->mm->start_brk = do_mmap(NULL, 0, stack_size,
 					 PROT_READ | PROT_WRITE | PROT_EXEC,
-					 MAP_PRIVATE | MAP_ANONYMOUS | MAP_GROWSDOWN,
+					 MAP_PRIVATE | MAP_ANONYMOUS |
+					 MAP_UNINITIALIZED | MAP_GROWSDOWN,
 					 0);
 
 	if (IS_ERR_VALUE(current->mm->start_brk)) {
diff --git a/include/asm-generic/mman-common.h b/include/asm-generic/mman-common.h
index 5ee13b2fd22..20111265afd 100644
--- a/include/asm-generic/mman-common.h
+++ b/include/asm-generic/mman-common.h
@@ -19,6 +19,11 @@
 #define MAP_TYPE	0x0f		/* Mask for type of mapping */
 #define MAP_FIXED	0x10		/* Interpret addr exactly */
 #define MAP_ANONYMOUS	0x20		/* don't use a file */
+#ifdef CONFIG_MMAP_ALLOW_UNINITIALIZED
+# define MAP_UNINITIALIZED 0x4000000	/* For anonymous mmap, memory could be uninitialized */
+#else
+# define MAP_UNINITIALIZED 0x0		/* Don't support this flag */
+#endif
 
 #define MS_ASYNC	1		/* sync memory asynchronously */
 #define MS_INVALIDATE	2		/* invalidate the caches */
diff --git a/init/Kconfig b/init/Kconfig
index 54c655ce9c0..a23da9f0180 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1079,6 +1079,28 @@ config SLOB
 
 endchoice
 
+config MMAP_ALLOW_UNINITIALIZED
+	bool "Allow mmapped anonymous memory to be uninitialized"
+	depends on EMBEDDED && !MMU
+	default n
+	help
+	  Normally, and according to the Linux spec, anonymous memory obtained
+	  from mmap() has it's contents cleared before it is passed to
+	  userspace.  Enabling this config option allows you to request that
+	  mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
+	  providing a huge performance boost.  If this option is not enabled,
+	  then the flag will be ignored.
+
+	  This is taken advantage of by uClibc's malloc(), and also by
+	  ELF-FDPIC binfmt's brk and stack allocator.
+
+	  Because of the obvious security issues, this option should only be
+	  enabled on embedded devices where you control what is run in
+	  userspace.  Since that isn't generally a problem on no-MMU systems,
+	  it is normally safe to say Y here.
+
+	  See Documentation/nommu-mmap.txt for more information.
+
 config PROFILING
 	bool "Profiling support (EXPERIMENTAL)"
 	help
diff --git a/mm/nommu.c b/mm/nommu.c
index 9876fa0c3ad..8687973462b 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1143,9 +1143,6 @@ static int do_mmap_private(struct vm_area_struct *vma,
 		if (ret < rlen)
 			memset(base + ret, 0, rlen - ret);
 
-	} else {
-		/* if it's an anonymous mapping, then just clear it */
-		memset(base, 0, rlen);
 	}
 
 	return 0;
@@ -1343,6 +1340,11 @@ unsigned long do_mmap_pgoff(struct file *file,
 		goto error_just_free;
 	add_nommu_region(region);
 
+	/* clear anonymous mappings that don't ask for uninitialized data */
+	if (!vma->vm_file && !(flags & MAP_UNINITIALIZED))
+		memset((void *)region->vm_start, 0,
+		       region->vm_end - region->vm_start);
+
 	/* okay... we have a mapping; now we have to register it */
 	result = vma->vm_start;