/* * SRAM protect-exec region helper functions * * Copyright (C) 2017 Texas Instruments Incorporated - http://www.ti.com/ * Dave Gerlach * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * This program is distributed "as is" WITHOUT ANY WARRANTY of any * kind, whether express or implied; without even the implied warranty * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #include <linux/device.h> #include <linux/genalloc.h> #include <linux/mm.h> #include <linux/sram.h> #include <asm/fncpy.h> #include <asm/set_memory.h> #include "sram.h" static DEFINE_MUTEX(exec_pool_list_mutex); static LIST_HEAD(exec_pool_list); int sram_check_protect_exec(struct sram_dev *sram, struct sram_reserve *block, struct sram_partition *part) { unsigned long base = (unsigned long)part->base; unsigned long end = base + block->size; if (!PAGE_ALIGNED(base) || !PAGE_ALIGNED(end)) { dev_err(sram->dev, "SRAM pool marked with 'protect-exec' is not page aligned and will not be created.\n"); return -ENOMEM; } return 0; } int sram_add_protect_exec(struct sram_partition *part) { mutex_lock(&exec_pool_list_mutex); list_add_tail(&part->list, &exec_pool_list); mutex_unlock(&exec_pool_list_mutex); return 0; } /** * sram_exec_copy - copy data to a protected executable region of sram * * @pool: struct gen_pool retrieved that is part of this sram * @dst: Destination address for the copy, that must be inside pool * @src: Source address for the data to copy * @size: Size of copy to perform, which starting from dst, must reside in pool * * Return: Address for copied data that can safely be called through function * pointer, or NULL if problem. * * This helper function allows sram driver to act as central control location * of 'protect-exec' pools which are normal sram pools but are always set * read-only and executable except when copying data to them, at which point * they are set to read-write non-executable, to make sure no memory is * writeable and executable at the same time. This region must be page-aligned * and is checked during probe, otherwise page attribute manipulation would * not be possible. Care must be taken to only call the returned address as * dst address is not guaranteed to be safely callable. * * NOTE: This function uses the fncpy macro to move code to the executable * region. Some architectures have strict requirements for relocating * executable code, so fncpy is a macro that must be defined by any arch * making use of this functionality that guarantees a safe copy of exec * data and returns a safe address that can be called as a C function * pointer. */ void *sram_exec_copy(struct gen_pool *pool, void *dst, void *src, size_t size) { struct sram_partition *part = NULL, *p; unsigned long base; int pages; void *dst_cpy; mutex_lock(&exec_pool_list_mutex); list_for_each_entry(p, &exec_pool_list, list) { if (p->pool == pool) part = p; } mutex_unlock(&exec_pool_list_mutex); if (!part) return NULL; if (!addr_in_gen_pool(pool, (unsigned long)dst, size)) return NULL; base = (unsigned long)part->base; pages = PAGE_ALIGN(size) / PAGE_SIZE; mutex_lock(&part->lock); set_memory_nx((unsigned long)base, pages); set_memory_rw((unsigned long)base, pages); dst_cpy = fncpy(dst, src, size); set_memory_ro((unsigned long)base, pages); set_memory_x((unsigned long)base, pages); mutex_unlock(&part->lock); return dst_cpy; } EXPORT_SYMBOL_GPL(sram_exec_copy);