rst-malloc: return aligned pointers to sizeof(void *) (v4)

Stas found that if we don't align a pointer,
futex and atomic operations can fail.

v2: don't hard-code the size of void *
v3: add a function to allocate memory without gaps with
    a privious slice. It's used to allocate arrays.
v4: don't change rst_mem_cpos

Cc: Stanislav Kinsburskiy <skinsbursky@virtuozzo.com>
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

include/rst-malloc.h

@@ -58,6 +58,7 @@ extern void *rst_mem_remap_ptr(unsigned long pos, int type);
  * last object can be freed (pop-ed from buffer).
  */
 extern void *rst_mem_alloc(unsigned long size, int type);
+extern void *rst_mem_alloc_cont(unsigned long size, int type);
 extern void rst_mem_free_last(int type);
 /*
  * Routines to remap SHREMAP and PRIVATE into restorer address space

rst-malloc.c

@@ -138,7 +138,7 @@ void *rst_mem_remap_ptr(unsigned long pos, int type)
 	return t->buf + pos;
 }
 
-void *rst_mem_alloc(unsigned long size, int type)
+static void *__rst_mem_alloc(unsigned long size, int type)
 {
 	struct rst_mem_type_s *t = &rst_mems[type];
 	void *ret;
@@ -158,6 +158,24 @@ void *rst_mem_alloc(unsigned long size, int type)
 	return ret;
 }
 
+void *rst_mem_alloc(unsigned long size, int type)
+{
+	struct rst_mem_type_s *t = &rst_mems[type];
+
+	t->free_mem = (void *) round_up((unsigned long)t->free_mem, sizeof(void *));
+
+	return __rst_mem_alloc(size, type);
+}
+
+/* Allocate memory without gaps with a previous slice */
+void *rst_mem_alloc_cont(unsigned long size, int type)
+{
+	struct rst_mem_type_s *t = &rst_mems[type];
+	BUG_ON(!t->remapable);
+
+	return __rst_mem_alloc(size, type);
+}
+
 void rst_mem_free_last(int type)
 {
 	struct rst_mem_type_s *t = &rst_mems[type];