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* Copyright (c) 2007 Petr Stepan, Pavel Jancik
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* - The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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* @brief Userspace switch.
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#include <userspace.h>
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/** Struct for holding all general purpose registers.
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* Used to set registers when going to userspace.
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/** Changes processor mode and jumps to the address specified in the first
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* @param kernel_uarg Userspace settings (entry point, stack, ...).
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void userspace(uspace_arg_t *kernel_uarg)
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volatile ustate_t ustate;
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/* set first parameter */
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ustate.r0 = (uintptr_t) kernel_uarg->uspace_uarg;
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/* %r1 is defined to hold pcb_ptr - set it to 0 */
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/* clear other registers */
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ustate.r2 = ustate.r3 = ustate.r4 = ustate.r5 =
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ustate.r6 = ustate.r7 = ustate.r8 = ustate.r9 = ustate.r10 =
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ustate.r11 = ustate.r12 = ustate.lr = 0;
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ustate.sp = ((uint32_t)kernel_uarg->uspace_stack) + PAGE_SIZE;
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/* set where uspace execution starts */
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ustate.pc = (uintptr_t) kernel_uarg->uspace_entry;
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/* status register in user mode */
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ipl_t user_mode = current_status_reg_read() &
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(~STATUS_REG_MODE_MASK | USER_MODE);
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/* set user mode, set registers, jump */
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"msr spsr_c, %[user_mode]\n"
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"ldmfd sp!, {r0-r12, sp, lr}^\n"
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:: [ustate] "r" (&ustate), [user_mode] "r" (user_mode)