sharepool: Fix ASLR broken

ascend inclusion
category: bugfix
bugzilla: NA
CVE: NA

---------------------------

To avoid mmap vspace reserved for sharepool, we currently change the
high_limit to MMAP_SHARE_POOL_START in arch_get_unmapped_area() and
arch_get_unmapped_area_topdown(). In mmap-topdown scene, this make the
start address of mmap being always MMAP_SHARE_POOL_START. ASLR got
broken.

To fix this, this patch set the mm->mmap_base based on
MMAP_SHARE_POOL_START instead of STACK_TOP in topdown scene.

Fixes: 4bdd5c21793e ("ascend: memory: introduce do_mm_populate and hugetlb_insert_hugepage")
Signed-off-by: NWang Wensheng <wangwensheng4@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Reviewed-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/arm64/mm/mmap.c

@@ -28,6 +28,7 @@
 #include <linux/io.h>
 #include <linux/personality.h>
 #include <linux/random.h>
+#include <linux/share_pool.h>
 
 #include <asm/cputype.h>
 
@@ -80,7 +81,10 @@ static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
 
-	return PAGE_ALIGN(STACK_TOP - gap - rnd);
+	if (sp_is_enabled())
+		return ALIGN_DOWN(MMAP_SHARE_POOL_START - rnd, PAGE_SIZE);
+	else
+		return PAGE_ALIGN(STACK_TOP - gap - rnd);
 }
 
 /*

include/linux/share_pool.h

@@ -130,8 +130,6 @@ struct sp_proc_stat {
 	atomic64_t k2u_size;
 };
 
-#ifdef CONFIG_ASCEND_SHARE_POOL
-
 #define MAP_SHARE_POOL			0x100000
 
 #define MMAP_TOP_4G_SIZE		0x100000000UL
@@ -148,6 +146,8 @@ struct sp_proc_stat {
 #define MMAP_SHARE_POOL_START		(MMAP_SHARE_POOL_END - MMAP_SHARE_POOL_SIZE)
 #define MMAP_SHARE_POOL_16G_START	(MMAP_SHARE_POOL_END - MMAP_SHARE_POOL_DVPP_SIZE)
 
+#ifdef CONFIG_ASCEND_SHARE_POOL
+
 static inline void sp_init_mm(struct mm_struct *mm)
 {
 	mm->sp_group = NULL;