// SPDX-License-Identifier: GPL-2.0-only
/*
 * SRAM protect-exec region helper functions
 *
 * Copyright (C) 2017 Texas Instruments Incorporated - https://www.ti.com/
 *      Dave Gerlach
 */

#include <linux/device.h>
#include <linux/genalloc.h>
#include <linux/mm.h>
#include <linux/sram.h>
#include <linux/set_memory.h>

#include <asm/fncpy.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_rox((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);