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scm.c

/* 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 - one SCM command buffer
 * @len: total available memory for command and response
 * @buf_offset: start of command buffer
 * @resp_hdr_offset: start of response buffer
 * @id: command to be executed
 * @buf: buffer returned from scm_get_command_buffer()
 *
 * An SCM command is layed out in memory as follows:
 *
 *    ------------------- <--- struct scm_command
 *    | command header  |
 *    ------------------- <--- scm_get_command_buffer()
 *    | command buffer  |
 *    ------------------- <--- struct scm_response and
 *    | response header |      scm_command_to_response()
 *    ------------------- <--- scm_get_response_buffer()
 *    | response buffer |
 *    -------------------
 *
 * There can be arbitrary padding between the headers and buffers so
 * you should always use the appropriate scm_get_*_buffer() routines
 * to access the buffers in a safe manner.
 */
00065 struct scm_command {
      u32   len;
      u32   buf_offset;
      u32   resp_hdr_offset;
      u32   id;
      u32   buf[0];
};

/**
 * struct scm_response - one SCM response buffer
 * @len: total available memory for response
 * @buf_offset: start of response data relative to start of scm_response
 * @is_complete: indicates if the command has finished processing
 */
00079 struct scm_response {
      u32   len;
      u32   buf_offset;
      u32   is_complete;
};

/**
 * alloc_scm_command() - Allocate an SCM command
 * @cmd_size: size of the command buffer
 * @resp_size: size of the response buffer
 *
 * Allocate an SCM command, including enough room for the command
 * and response headers as well as the command and response buffers.
 *
 * Returns a valid &scm_command on success or %NULL if the allocation fails.
 */
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;
}

/**
 * free_scm_command() - Free an SCM command
 * @cmd: command to free
 *
 * Free an SCM command.
 */
static inline void free_scm_command(struct scm_command *cmd)
{
      kfree(cmd);
}

/**
 * scm_command_to_response() - Get a pointer to a scm_response
 * @cmd: command
 *
 * Returns a pointer to a response for a command.
 */
static inline struct scm_response *scm_command_to_response(
            const struct scm_command *cmd)
{
      return (void *)cmd + cmd->resp_hdr_offset;
}

/**
 * scm_get_command_buffer() - Get a pointer to a command buffer
 * @cmd: command
 *
 * Returns a pointer to the command buffer of a command.
 */
static inline void *scm_get_command_buffer(const struct scm_command *cmd)
{
      return (void *)cmd->buf;
}

/**
 * scm_get_response_buffer() - Get a pointer to a response buffer
 * @rsp: response
 *
 * Returns a pointer to a response buffer of a response.
 */
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;
      asm(
            __asmeq("%0", "r0")
            __asmeq("%1", "r0")
            __asmeq("%2", "r1")
            __asmeq("%3", "r2")
            "smc  #0    @ switch to secure world\n"
            : "=r" (r0)
            : "r" (r0), "r" (r1), "r" (r2)
            : "r3");
      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();
      do {
            ret = smc(cmd_addr);
            if (ret < 0) {
                  ret = scm_remap_error(ret);
                  break;
            }
      } while (ret == SCM_INTERRUPTED);

      return ret;
}

/**
 * scm_call() - Send an SCM command
 * @svc_id: service identifier
 * @cmd_id: command identifier
 * @cmd_buf: command buffer
 * @cmd_len: length of the command buffer
 * @resp_buf: response buffer
 * @resp_len: length of the response buffer
 *
 * Sends a command to the SCM and waits for the command to finish processing.
 */
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") = 0x1 << 8;
      register u32 r1 asm("r1") = (u32)&context_id;

      if (version != -1)
            return version;

      mutex_lock(&scm_lock);
      asm(
            __asmeq("%0", "r1")
            __asmeq("%1", "r0")
            __asmeq("%2", "r1")
            "smc  #0    @ switch to secure world\n"
            : "=r" (r1)
            : "r" (r0), "r" (r1)
            : "r2", "r3");
      version = r1;
      mutex_unlock(&scm_lock);

      return version;
}
EXPORT_SYMBOL(scm_get_version);

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