1 /*
2 * SRAM protect-exec region helper functions
3 *
4 * Copyright (C) 2017 Texas Instruments Incorporated - https://www.ti.com/
5 * Dave Gerlach
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
12 * kind, whether express or implied; without even the implied warranty
13 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 */
16
17 #include <linux/device.h>
18 #include <linux/genalloc.h>
19 #include <linux/mm.h>
20 #include <linux/sram.h>
21
22 #include <asm/fncpy.h>
23 #include <asm/set_memory.h>
24
25 #include "sram.h"
26
27 static DEFINE_MUTEX(exec_pool_list_mutex);
28 static LIST_HEAD(exec_pool_list);
29
sram_check_protect_exec(struct sram_dev * sram,struct sram_reserve * block,struct sram_partition * part)30 int sram_check_protect_exec(struct sram_dev *sram, struct sram_reserve *block,
31 struct sram_partition *part)
32 {
33 unsigned long base = (unsigned long)part->base;
34 unsigned long end = base + block->size;
35
36 if (!PAGE_ALIGNED(base) || !PAGE_ALIGNED(end)) {
37 dev_err(sram->dev,
38 "SRAM pool marked with 'protect-exec' is not page aligned and will not be created.\n");
39 return -ENOMEM;
40 }
41
42 return 0;
43 }
44
sram_add_protect_exec(struct sram_partition * part)45 int sram_add_protect_exec(struct sram_partition *part)
46 {
47 mutex_lock(&exec_pool_list_mutex);
48 list_add_tail(&part->list, &exec_pool_list);
49 mutex_unlock(&exec_pool_list_mutex);
50
51 return 0;
52 }
53
54 /**
55 * sram_exec_copy - copy data to a protected executable region of sram
56 *
57 * @pool: struct gen_pool retrieved that is part of this sram
58 * @dst: Destination address for the copy, that must be inside pool
59 * @src: Source address for the data to copy
60 * @size: Size of copy to perform, which starting from dst, must reside in pool
61 *
62 * Return: Address for copied data that can safely be called through function
63 * pointer, or NULL if problem.
64 *
65 * This helper function allows sram driver to act as central control location
66 * of 'protect-exec' pools which are normal sram pools but are always set
67 * read-only and executable except when copying data to them, at which point
68 * they are set to read-write non-executable, to make sure no memory is
69 * writeable and executable at the same time. This region must be page-aligned
70 * and is checked during probe, otherwise page attribute manipulation would
71 * not be possible. Care must be taken to only call the returned address as
72 * dst address is not guaranteed to be safely callable.
73 *
74 * NOTE: This function uses the fncpy macro to move code to the executable
75 * region. Some architectures have strict requirements for relocating
76 * executable code, so fncpy is a macro that must be defined by any arch
77 * making use of this functionality that guarantees a safe copy of exec
78 * data and returns a safe address that can be called as a C function
79 * pointer.
80 */
sram_exec_copy(struct gen_pool * pool,void * dst,void * src,size_t size)81 void *sram_exec_copy(struct gen_pool *pool, void *dst, void *src,
82 size_t size)
83 {
84 struct sram_partition *part = NULL, *p;
85 unsigned long base;
86 int pages;
87 void *dst_cpy;
88 int ret;
89
90 mutex_lock(&exec_pool_list_mutex);
91 list_for_each_entry(p, &exec_pool_list, list) {
92 if (p->pool == pool)
93 part = p;
94 }
95 mutex_unlock(&exec_pool_list_mutex);
96
97 if (!part)
98 return NULL;
99
100 if (!gen_pool_has_addr(pool, (unsigned long)dst, size))
101 return NULL;
102
103 base = (unsigned long)part->base;
104 pages = PAGE_ALIGN(size) / PAGE_SIZE;
105
106 mutex_lock(&part->lock);
107
108 ret = set_memory_nx((unsigned long)base, pages);
109 if (ret)
110 goto error_out;
111 ret = set_memory_rw((unsigned long)base, pages);
112 if (ret)
113 goto error_out;
114
115 dst_cpy = fncpy(dst, src, size);
116
117 ret = set_memory_ro((unsigned long)base, pages);
118 if (ret)
119 goto error_out;
120 ret = set_memory_x((unsigned long)base, pages);
121 if (ret)
122 goto error_out;
123
124 mutex_unlock(&part->lock);
125
126 return dst_cpy;
127
128 error_out:
129 mutex_unlock(&part->lock);
130 return NULL;
131 }
132 EXPORT_SYMBOL_GPL(sram_exec_copy);
133
