1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * SRAM protect-exec region helper functions
  4 *
  5 * Copyright (C) 2017 Texas Instruments Incorporated - https://www.ti.com/
  6 *	Dave Gerlach
  7 */
  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 sram
 48 *
 49 * @pool: struct gen_pool retrieved that is part of this sram
 50 * @dst: Destination address for the copy, that must be inside pool
 51 * @src: Source address for the data to copy
 52 * @size: Size of copy to perform, which starting from dst, must reside in pool
 53 *
 54 * Return: Address for copied data that can safely be called through function
 55 *	   pointer, or NULL if problem.
 56 *
 57 * This helper function allows sram driver to act as central control location
 58 * of 'protect-exec' pools which are normal sram pools but are always set
 59 * read-only and executable except when copying data to them, at which point
 60 * they are set to read-write non-executable, to make sure no memory is
 61 * writeable and executable at the same time. This region must be page-aligned
 62 * and is checked during probe, otherwise page attribute manipulation would
 63 * not be possible. Care must be taken to only call the returned address as
 64 * dst address is not guaranteed to be safely callable.
 65 *
 66 * NOTE: This function uses the fncpy macro to move code to the executable
 67 * region. Some architectures have strict requirements for relocating
 68 * executable code, so fncpy is a macro that must be defined by any arch
 69 * making use of this functionality that guarantees a safe copy of exec
 70 * data and returns a safe address that can be called as a C function
 71 * 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);