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  1. /*
  2.  * Copyright (c) 2007 Petr Stepan, Pavel Jancik
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup arm32
  30.  * @{
  31.  */
  32. /** @file
  33.  *  @brief Userspace switch.
  34.  */
  35.  
  36. #include <userspace.h>
  37.  
  38. /** Struct for holding all general purpose registers.
  39.  *  
  40.  *  Used to set registers when going to userspace.
  41.  */
  42. typedef struct {
  43.     uint32_t r0;
  44.     uint32_t r1;
  45.     uint32_t r2;
  46.     uint32_t r3;
  47.     uint32_t r4;
  48.     uint32_t r5;
  49.     uint32_t r6;
  50.     uint32_t r7;
  51.     uint32_t r8;
  52.     uint32_t r9;
  53.     uint32_t r10;
  54.     uint32_t r11;
  55.     uint32_t r12;
  56.     uint32_t sp;
  57.     uint32_t lr;
  58.     uint32_t pc;
  59. } ustate_t;
  60.  
  61. /** Changes processor mode and jumps to the address specified in the first
  62.  * parameter.
  63.  *
  64.  *  @param kernel_uarg   Userspace settings (entry point, stack, ...).
  65.  */
  66. void userspace(uspace_arg_t *kernel_uarg)
  67. {
  68.     volatile ustate_t ustate;
  69.  
  70.     /* set first parameter */
  71.     ustate.r0 = (uintptr_t) kernel_uarg->uspace_uarg;
  72.  
  73.     /* %r1 is defined to hold pcb_ptr - set it to 0 */
  74.     ustate.r1 = 0;
  75.  
  76.     /* clear other registers */
  77.     ustate.r2 = ustate.r3  = ustate.r4  = ustate.r5 =
  78.         ustate.r6  = ustate.r7  = ustate.r8  = ustate.r9 = ustate.r10 =
  79.         ustate.r11 = ustate.r12 = ustate.lr = 0;
  80.  
  81.     /* set user stack */
  82.     ustate.sp = ((uint32_t)kernel_uarg->uspace_stack) + PAGE_SIZE;
  83.  
  84.     /* set where uspace execution starts */
  85.     ustate.pc = (uintptr_t) kernel_uarg->uspace_entry;
  86.  
  87.     /* status register in user mode */
  88.     ipl_t user_mode = current_status_reg_read() &
  89.         (~STATUS_REG_MODE_MASK | USER_MODE);
  90.  
  91.     /* set user mode, set registers, jump */
  92.     asm volatile (
  93.         "mov sp, %0         \n"
  94.         "msr spsr_c, %1         \n"
  95.         "ldmfd sp!, {r0-r12, sp, lr}^   \n"
  96.         "ldmfd sp!, {pc}^\n"
  97.         :
  98.         : "r" (&ustate), "r" (user_mode)
  99.     );
  100.  
  101.     /* unreachable */
  102.     while(1)
  103.         ;
  104. }
  105.  
  106. /** @}
  107.  */
  108.