mmap.c

 1// SPDX-License-Identifier: GPL-2.0
 2// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
 3
 4#include <linux/fs.h>
 5#include <linux/mm.h>
 6#include <linux/mman.h>
 7#include <linux/shm.h>
 8#include <linux/sched.h>
 9#include <linux/random.h>
10#include <linux/io.h>
11
12#define COLOUR_ALIGN(addr,pgoff)		\
13	((((addr)+SHMLBA-1)&~(SHMLBA-1)) +	\
14	 (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
15
16/*
17 * We need to ensure that shared mappings are correctly aligned to
18 * avoid aliasing issues with VIPT caches.  We need to ensure that
19 * a specific page of an object is always mapped at a multiple of
20 * SHMLBA bytes.
21 *
22 * We unconditionally provide this function for all cases.
23 */
24unsigned long
25arch_get_unmapped_area(struct file *filp, unsigned long addr,
26		unsigned long len, unsigned long pgoff,
27		unsigned long flags, vm_flags_t vm_flags)
28{
29	struct mm_struct *mm = current->mm;
30	struct vm_area_struct *vma;
31	int do_align = 0;
32	struct vm_unmapped_area_info info = {
33		.length = len,
34		.low_limit = mm->mmap_base,
35		.high_limit = TASK_SIZE,
36		.align_offset = pgoff << PAGE_SHIFT
37	};
38
39	/*
40	 * We only need to do colour alignment if either the I or D
41	 * caches alias.
42	 */
43	do_align = filp || (flags & MAP_SHARED);
44
45	/*
46	 * We enforce the MAP_FIXED case.
47	 */
48	if (flags & MAP_FIXED) {
49		if (flags & MAP_SHARED &&
50		    (addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1))
51			return -EINVAL;
52		return addr;
53	}
54
55	if (len > TASK_SIZE)
56		return -ENOMEM;
57
58	if (addr) {
59		if (do_align)
60			addr = COLOUR_ALIGN(addr, pgoff);
61		else
62			addr = PAGE_ALIGN(addr);
63
64		vma = find_vma(mm, addr);
65		if (TASK_SIZE - len >= addr &&
66		    (!vma || addr + len <= vm_start_gap(vma)))
67			return addr;
68	}
69
70	info.align_mask = do_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
71	return vm_unmapped_area(&info);
72}