linux_compat: handle __GFP_ZERO in kmalloc()

Currently, kzalloc() returns zero-filled memory, while kmalloc()
simply ignores the second argument and never fills the memory
area with zeros.

I want kmalloc(size, __GFP_ZERO) to behave as kzalloc() does,
which will make it easier to add more memory allocator variants.

With the introduction of __GFP_ZERO flag, going forward, kzmalloc()
variants can fall back to kmalloc() enabling the __GFP_ZERO flag.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Acked-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>

include/linux/compat.h

@@ -36,8 +36,19 @@ extern struct p_current *current;
 #define KERN_INFO
 #define KERN_DEBUG
 
+#define GFP_ATOMIC ((gfp_t) 0)
+#define GFP_KERNEL ((gfp_t) 0)
+#define GFP_NOFS ((gfp_t) 0)
+#define GFP_USER ((gfp_t) 0)
+#define __GFP_NOWARN ((gfp_t) 0)
+#define __GFP_ZERO	((__force gfp_t)0x8000u)	/* Return zeroed page on success */
+
 void *kmalloc(size_t size, int flags);
-void *kzalloc(size_t size, int flags);
+
+static inline void *kzalloc(size_t size, gfp_t flags)
+{
+	return kmalloc(size, flags | __GFP_ZERO);
+}
 #define vmalloc(size)	kmalloc(size, 0)
 #define __vmalloc(size, flags, pgsz)	kmalloc(size, flags)
 static inline void *vzalloc(unsigned long size)
@@ -77,13 +88,6 @@ void *kmem_cache_alloc(struct kmem_cache *obj, int flag);
 /* drivers/char/random.c */
 #define get_random_bytes(...)
 
-/* idr.c */
-#define GFP_ATOMIC ((gfp_t) 0)
-#define GFP_KERNEL ((gfp_t) 0)
-#define GFP_NOFS ((gfp_t) 0)
-#define GFP_USER ((gfp_t) 0)
-#define __GFP_NOWARN ((gfp_t) 0)
-
 /* include/linux/leds.h */
 struct led_trigger {};
 

lib/linux_compat.c

@@ -16,14 +16,13 @@ unsigned long copy_from_user(void *dest, const void *src,
 
 void *kmalloc(size_t size, int flags)
 {
-	return memalign(ARCH_DMA_MINALIGN, size);
-}
+	void *p;
 
-void *kzalloc(size_t size, int flags)
-{
-	void *ptr = kmalloc(size, flags);
-	memset(ptr, 0, size);
-	return ptr;
+	p = memalign(ARCH_DMA_MINALIGN, size);
+	if (flags & __GFP_ZERO)
+		memset(p, 0, size);
+
+	return p;
 }
 
 struct kmem_cache *get_mem(int element_sz)