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/*
* SRAM protect-exec region helper functions
*
* Copyright (C) 2017 Texas Instruments Incorporated - https://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;
int ret;
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 (!gen_pool_has_addr(pool, (unsigned long)dst, size))
return NULL;
base = (unsigned long)part->base;
pages = PAGE_ALIGN(size) / PAGE_SIZE;
mutex_lock(&part->lock);
ret = set_memory_nx((unsigned long)base, pages);
if (ret)
goto error_out;
ret = set_memory_rw((unsigned long)base, pages);
if (ret)
goto error_out;
dst_cpy = fncpy(dst, src, size);
ret = set_memory_ro((unsigned long)base, pages);
if (ret)
goto error_out;
ret = set_memory_x((unsigned long)base, pages);
if (ret)
goto error_out;
mutex_unlock(&part->lock);
return dst_cpy;
error_out:
mutex_unlock(&part->lock);
return NULL;
}
EXPORT_SYMBOL_GPL(sram_exec_copy);
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