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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * SRAM protect-exec region helper functions4 *5 * Copyright (C) 2017 Texas Instruments Incorporated - https://www.ti.com/6 * Dave Gerlach7 */8 9#include <linux/device.h>10#include <linux/genalloc.h>11#include <linux/mm.h>12#include <linux/sram.h>13#include <linux/set_memory.h>14 15#include <asm/fncpy.h>16 17#include "sram.h"18 19static DEFINE_MUTEX(exec_pool_list_mutex);20static LIST_HEAD(exec_pool_list);21 22int sram_check_protect_exec(struct sram_dev *sram, struct sram_reserve *block,23 struct sram_partition *part)24{25 unsigned long base = (unsigned long)part->base;26 unsigned long end = base + block->size;27 28 if (!PAGE_ALIGNED(base) || !PAGE_ALIGNED(end)) {29 dev_err(sram->dev,30 "SRAM pool marked with 'protect-exec' is not page aligned and will not be created.\n");31 return -ENOMEM;32 }33 34 return 0;35}36 37int sram_add_protect_exec(struct sram_partition *part)38{39 mutex_lock(&exec_pool_list_mutex);40 list_add_tail(&part->list, &exec_pool_list);41 mutex_unlock(&exec_pool_list_mutex);42 43 return 0;44}45 46/**47 * sram_exec_copy - copy data to a protected executable region of sram48 *49 * @pool: struct gen_pool retrieved that is part of this sram50 * @dst: Destination address for the copy, that must be inside pool51 * @src: Source address for the data to copy52 * @size: Size of copy to perform, which starting from dst, must reside in pool53 *54 * Return: Address for copied data that can safely be called through function55 * pointer, or NULL if problem.56 *57 * This helper function allows sram driver to act as central control location58 * of 'protect-exec' pools which are normal sram pools but are always set59 * read-only and executable except when copying data to them, at which point60 * they are set to read-write non-executable, to make sure no memory is61 * writeable and executable at the same time. This region must be page-aligned62 * and is checked during probe, otherwise page attribute manipulation would63 * not be possible. Care must be taken to only call the returned address as64 * dst address is not guaranteed to be safely callable.65 *66 * NOTE: This function uses the fncpy macro to move code to the executable67 * region. Some architectures have strict requirements for relocating68 * executable code, so fncpy is a macro that must be defined by any arch69 * making use of this functionality that guarantees a safe copy of exec70 * data and returns a safe address that can be called as a C function71 * pointer.72 */73void *sram_exec_copy(struct gen_pool *pool, void *dst, void *src,74 size_t size)75{76 struct sram_partition *part = NULL, *p;77 unsigned long base;78 int pages;79 void *dst_cpy;80 int ret;81 82 mutex_lock(&exec_pool_list_mutex);83 list_for_each_entry(p, &exec_pool_list, list) {84 if (p->pool == pool)85 part = p;86 }87 mutex_unlock(&exec_pool_list_mutex);88 89 if (!part)90 return NULL;91 92 if (!gen_pool_has_addr(pool, (unsigned long)dst, size))93 return NULL;94 95 base = (unsigned long)part->base;96 pages = PAGE_ALIGN(size) / PAGE_SIZE;97 98 mutex_lock(&part->lock);99 100 ret = set_memory_nx((unsigned long)base, pages);101 if (ret)102 goto error_out;103 ret = set_memory_rw((unsigned long)base, pages);104 if (ret)105 goto error_out;106 107 dst_cpy = fncpy(dst, src, size);108 109 ret = set_memory_rox((unsigned long)base, pages);110 if (ret)111 goto error_out;112 113 mutex_unlock(&part->lock);114 115 return dst_cpy;116 117error_out:118 mutex_unlock(&part->lock);119 return NULL;120}121EXPORT_SYMBOL_GPL(sram_exec_copy);122