scm.c

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/* Copyright (c) 2010, Code Aurora Forum. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/slab.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/errno.h>
#include <linux/err.h>

#include <asm/cacheflush.h>

#include "scm.h"

/* Cache line size for msm8x60 */
#define CACHELINESIZE 32

#define SCM_ENOMEM      -5
#define SCM_EOPNOTSUPP      -4
#define SCM_EINVAL_ADDR     -3
#define SCM_EINVAL_ARG      -2
#define SCM_ERROR       -1
#define SCM_INTERRUPTED     1

static DEFINE_MUTEX(scm_lock);

struct scm_command {
    u32 len;
    u32 buf_offset;
    u32 resp_hdr_offset;
    u32 id;
    u32 buf[0];
};

struct scm_response {
    u32 len;
    u32 buf_offset;
    u32 is_complete;
};

static struct scm_command *alloc_scm_command(size_t cmd_size, size_t resp_size)
{
    struct scm_command *cmd;
    size_t len = sizeof(*cmd) + sizeof(struct scm_response) + cmd_size +
        resp_size;

    cmd = kzalloc(PAGE_ALIGN(len), GFP_KERNEL);
    if (cmd) {
        cmd->len = len;
        cmd->buf_offset = offsetof(struct scm_command, buf);
        cmd->resp_hdr_offset = cmd->buf_offset + cmd_size;
    }
    return cmd;
}

static inline void free_scm_command(struct scm_command *cmd)
{
    kfree(cmd);
}

static inline struct scm_response *scm_command_to_response(
        const struct scm_command *cmd)
{
    return (void *)cmd + cmd->resp_hdr_offset;
}

static inline void *scm_get_command_buffer(const struct scm_command *cmd)
{
    return (void *)cmd->buf;
}

static inline void *scm_get_response_buffer(const struct scm_response *rsp)
{
    return (void *)rsp + rsp->buf_offset;
}

static int scm_remap_error(int err)
{
    switch (err) {
    case SCM_ERROR:
        return -EIO;
    case SCM_EINVAL_ADDR:
    case SCM_EINVAL_ARG:
        return -EINVAL;
    case SCM_EOPNOTSUPP:
        return -EOPNOTSUPP;
    case SCM_ENOMEM:
        return -ENOMEM;
    }
    return -EINVAL;
}

static u32 smc(u32 cmd_addr)
{
    int context_id;
    register u32 r0 asm("r0") = 1;
    register u32 r1 asm("r1") = (u32)&context_id;
    register u32 r2 asm("r2") = cmd_addr;
    do {
        asm volatile(
            __asmeq("%0", "r0")
            __asmeq("%1", "r0")
            __asmeq("%2", "r1")
            __asmeq("%3", "r2")
#ifdef REQUIRES_SEC
            ".arch_extension sec\n"
#endif
            "smc    #0  @ switch to secure world\n"
            : "=r" (r0)
            : "r" (r0), "r" (r1), "r" (r2)
            : "r3");
    } while (r0 == SCM_INTERRUPTED);

    return r0;
}

static int __scm_call(const struct scm_command *cmd)
{
    int ret;
    u32 cmd_addr = virt_to_phys(cmd);

    /*
     * Flush the entire cache here so callers don't have to remember
     * to flush the cache when passing physical addresses to the secure
     * side in the buffer.
     */
    flush_cache_all();
    ret = smc(cmd_addr);
    if (ret < 0)
        ret = scm_remap_error(ret);

    return ret;
}

int scm_call(u32 svc_id, u32 cmd_id, const void *cmd_buf, size_t cmd_len,
        void *resp_buf, size_t resp_len)
{
    int ret;
    struct scm_command *cmd;
    struct scm_response *rsp;

    cmd = alloc_scm_command(cmd_len, resp_len);
    if (!cmd)
        return -ENOMEM;

    cmd->id = (svc_id << 10) | cmd_id;
    if (cmd_buf)
        memcpy(scm_get_command_buffer(cmd), cmd_buf, cmd_len);

    mutex_lock(&scm_lock);
    ret = __scm_call(cmd);
    mutex_unlock(&scm_lock);
    if (ret)
        goto out;

    rsp = scm_command_to_response(cmd);
    do {
        u32 start = (u32)rsp;
        u32 end = (u32)scm_get_response_buffer(rsp) + resp_len;
        start &= ~(CACHELINESIZE - 1);
        while (start < end) {
            asm ("mcr p15, 0, %0, c7, c6, 1" : : "r" (start)
                 : "memory");
            start += CACHELINESIZE;
        }
    } while (!rsp->is_complete);

    if (resp_buf)
        memcpy(resp_buf, scm_get_response_buffer(rsp), resp_len);
out:
    free_scm_command(cmd);
    return ret;
}
EXPORT_SYMBOL(scm_call);

u32 scm_get_version(void)
{
    int context_id;
    static u32 version = -1;
    register u32 r0 asm("r0");
    register u32 r1 asm("r1");

    if (version != -1)
        return version;

    mutex_lock(&scm_lock);

    r0 = 0x1 << 8;
    r1 = (u32)&context_id;
    do {
        asm volatile(
            __asmeq("%0", "r0")
            __asmeq("%1", "r1")
            __asmeq("%2", "r0")
            __asmeq("%3", "r1")
#ifdef REQUIRES_SEC
            ".arch_extension sec\n"
#endif
            "smc    #0  @ switch to secure world\n"
            : "=r" (r0), "=r" (r1)
            : "r" (r0), "r" (r1)
            : "r2", "r3");
    } while (r0 == SCM_INTERRUPTED);

    version = r1;
    mutex_unlock(&scm_lock);

    return version;
}
EXPORT_SYMBOL(scm_get_version);