nommu: use MAP_UNINITIALIZE for mallocs

Now that the kernel supports MAP_UNINITIALIZE, have the malloc places use
it to get real uninitialized memory on no-mmu systems.  This avoids a lot
of normally useless overhead involved in zeroing out all of the memory
(sometimes multiple times).

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

9 files changed, 15 insertions, 3 deletions

diff --git a/libc/stdlib/malloc-simple/alloc.c b/libc/stdlib/malloc-simple/alloc.c
index 36355c1e9..51da14ac8 100644
--- a/libc/stdlib/malloc-simple/alloc.c
+++ b/libc/stdlib/malloc-simple/alloc.c
@@ -36,7 +36,7 @@ void *malloc(size_t size)
 #ifdef __ARCH_USE_MMU__
 # define MMAP_FLAGS MAP_PRIVATE | MAP_ANONYMOUS
 #else
-# define MMAP_FLAGS MAP_SHARED | MAP_ANONYMOUS
+# define MMAP_FLAGS MAP_SHARED | MAP_ANONYMOUS | MAP_UNINITIALIZE
 #endif
 
 	result = mmap((void *) 0, size + sizeof(size_t), PROT_READ | PROT_WRITE,
diff --git a/libc/stdlib/malloc-standard/malloc.h b/libc/stdlib/malloc-standard/malloc.h
index 90c9fd14d..7a2e66d16 100644
--- a/libc/stdlib/malloc-standard/malloc.h
+++ b/libc/stdlib/malloc-standard/malloc.h
@@ -356,7 +356,7 @@ __UCLIBC_MUTEX_EXTERN(__malloc_lock);
 #else
 
 #define MMAP(addr, size, prot) \
- (mmap((addr), (size), (prot), MAP_SHARED|MAP_ANONYMOUS, 0, 0))
+ (mmap((addr), (size), (prot), MAP_SHARED|MAP_ANONYMOUS|MAP_UNINITIALIZE, 0, 0))
 
 #endif
 
diff --git a/libc/stdlib/malloc/malloc.c b/libc/stdlib/malloc/malloc.c
index f4bbc71a2..337206f09 100644
--- a/libc/stdlib/malloc/malloc.c
+++ b/libc/stdlib/malloc/malloc.c
@@ -124,7 +124,7 @@ __malloc_from_heap (size_t size, struct heap_free_area **heap
 		    MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
 #else
       block = mmap ((void *)0, block_size, PROT_READ | PROT_WRITE,
-		    MAP_SHARED | MAP_ANONYMOUS, 0, 0);
+		    MAP_SHARED | MAP_ANONYMOUS | MAP_UNINITIALIZE, 0, 0);
 #endif
 
 #endif /* MALLOC_USE_SBRK */
diff --git a/libc/sysdeps/linux/alpha/bits/mman.h b/libc/sysdeps/linux/alpha/bits/mman.h
index 2f0e56491..cafad4a24 100644
--- a/libc/sysdeps/linux/alpha/bits/mman.h
+++ b/libc/sysdeps/linux/alpha/bits/mman.h
@@ -71,6 +71,8 @@
 # define MAP_NORESERVE	  0x10000	/* Don't check for reservations.  */
 # define MAP_POPULATE	  0x20000	/* Populate (prefault) pagetables.  */
 # define MAP_NONBLOCK	  0x40000	/* Do not block on IO.  */
+# define MAP_UNINITIALIZE 0x4000000     /* For anonymous mmap, memory could
+					   be uninitialized. */
 #endif
 
 /* Flags to `msync'.  */
diff --git a/libc/sysdeps/linux/hppa/bits/mman.h b/libc/sysdeps/linux/hppa/bits/mman.h
index 54531ecf2..7f9bf4ed6 100644
--- a/libc/sysdeps/linux/hppa/bits/mman.h
+++ b/libc/sysdeps/linux/hppa/bits/mman.h
@@ -45,6 +45,8 @@
 #define MAP_GROWSDOWN	0x8000		/* stack-like segment */
 #define MAP_POPULATE	0x10000		/* populate (prefault) pagetables */
 #define MAP_NONBLOCK	0x20000		/* do not block on IO */
+#define MAP_UNINITIALIZE 0x4000000     /* For anonymous mmap, memory could
+					  be uninitialized. */
 
 #define MS_SYNC		1		/* synchronous memory sync */
 #define MS_ASYNC	2		/* sync memory asynchronously */
diff --git a/libc/sysdeps/linux/mips/bits/mman.h b/libc/sysdeps/linux/mips/bits/mman.h
index 47d33933a..c480be46e 100644
--- a/libc/sysdeps/linux/mips/bits/mman.h
+++ b/libc/sysdeps/linux/mips/bits/mman.h
@@ -66,6 +66,8 @@
 # define MAP_LOCKED	0x8000		/* pages are locked */
 # define MAP_POPULATE   0x10000         /* populate (prefault) pagetables */
 # define MAP_NONBLOCK   0x20000         /* do not block on IO */
+# define MAP_UNINITIALIZE 0x4000000     /* For anonymous mmap, memory could
+					   be uninitialized. */
 #endif
 
 /* Flags to `msync'.  */
diff --git a/libc/sysdeps/linux/powerpc/bits/mman.h b/libc/sysdeps/linux/powerpc/bits/mman.h
index e03ab7ff8..2d234c5fc 100644
--- a/libc/sysdeps/linux/powerpc/bits/mman.h
+++ b/libc/sysdeps/linux/powerpc/bits/mman.h
@@ -63,6 +63,8 @@
 # define MAP_NORESERVE	0x00040		/* Don't check for reservations.  */
 # define MAP_POPULATE	0x08000		/* Populate (prefault) pagetables.  */
 # define MAP_NONBLOCK	0x10000		/* Do not block on IO.  */
+# define MAP_UNINITIALIZE 0x4000000     /* For anonymous mmap, memory could
+					   be uninitialized. */
 #endif
 
 /* Flags to `msync'.  */
diff --git a/libc/sysdeps/linux/sparc/bits/mman.h b/libc/sysdeps/linux/sparc/bits/mman.h
index be2b7eb28..74921e4c5 100644
--- a/libc/sysdeps/linux/sparc/bits/mman.h
+++ b/libc/sysdeps/linux/sparc/bits/mman.h
@@ -65,6 +65,8 @@
 # define _MAP_NEW	0x80000000	/* Binary compatibility with SunOS.  */
 # define MAP_POPULATE	0x8000		/* Populate (prefault) pagetables.  */
 # define MAP_NONBLOCK	0x10000		/* Do not block on IO.  */
+# define MAP_UNINITIALIZE 0x4000000     /* For anonymous mmap, memory could
+					   be uninitialized. */
 #endif
 
 /* Flags to `msync'.  */
diff --git a/libc/sysdeps/linux/xtensa/bits/mman.h b/libc/sysdeps/linux/xtensa/bits/mman.h
index d3beae6aa..fead3ac20 100644
--- a/libc/sysdeps/linux/xtensa/bits/mman.h
+++ b/libc/sysdeps/linux/xtensa/bits/mman.h
@@ -64,6 +64,8 @@
 # define MAP_NORESERVE	0x0400		/* Don't check for reservations.  */
 # define MAP_POPULATE	0x10000		/* Populate (prefault) pagetables.  */
 # define MAP_NONBLOCK	0x20000		/* Do not block on IO.  */
+# define MAP_UNINITIALIZE 0x4000000     /* For anonymous mmap, memory could
+					   be uninitialized. */
 #endif
 
 /* Flags to `msync'.  */