kernel/arch/arm32/src/userspace.c

   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 kernel_arm32
  30  * @{
  31  */
  32 /** @file
  33  *  @brief Userspace switch.
  34  */
  35
  36 #include <stdbool.h>
  37 #include <userspace.h>
  38 #include <arch/ras.h>
  39
  40 /** Struct for holding all general purpose registers.
  41  *
  42  *  Used to set registers when going to userspace.
  43  */
  44 typedef struct {
  45         uint32_t r0;
  46         uint32_t r1;
  47         uint32_t r2;
  48         uint32_t r3;
  49         uint32_t r4;
  50         uint32_t r5;
  51         uint32_t r6;
  52         uint32_t r7;
  53         uint32_t r8;
  54         uint32_t r9;
  55         uint32_t r10;
  56         uint32_t r11;
  57         uint32_t r12;
  58         uint32_t sp;
  59         uint32_t lr;
  60         uint32_t pc;
  61 } ustate_t;
  62
  63 uintptr_t arch_get_initial_sp(uintptr_t stack_base, uintptr_t stack_size)
  64 {
  65         return stack_base + stack_size;
  66 }
  67
  68 /** Change processor mode
  69  *
  70  * @param kernel_uarg Userspace settings (entry point, stack, ...).
  71  *
  72  */
  73 void userspace(uintptr_t pc, uintptr_t sp)
  74 {
  75         volatile ustate_t ustate = { };
  76
  77         /* pass the RAS page address in %r2 */
  78         ustate.r2 = (uintptr_t) ras_page;
  79
  80         ustate.sp = sp;
  81         ustate.pc = pc;
  82
  83         /* status register in user mode */
  84         ipl_t user_mode = current_status_reg_read() &
  85             (~STATUS_REG_MODE_MASK | USER_MODE);
  86
  87         /* set user mode, set registers, jump */
  88         asm volatile (
  89             "mov sp, %[ustate]\n"
  90             "msr spsr_c, %[user_mode]\n"
  91             "ldmfd sp, {r0-r12, sp, lr}^\n"
  92             "nop\n"             /* Cannot access sp immediately after ldm(2) */
  93             "add sp, sp, #(15*4)\n"
  94             "ldmfd sp!, {pc}^\n"
  95             :: [ustate] "r" (&ustate), [user_mode] "r" (user_mode)
  96         );
  97
  98         unreachable();
  99 }
 100
 101 /** @}
 102  */