/****************************************************************************
* arch/avr32/src/avr32/up_fullcontextrestore.S
*
* Copyright (C) 2010 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <arch/avr32/avr32.h>
/****************************************************************************
* External Symbols
****************************************************************************/
.file "up_fullcontextrestore.S"
/****************************************************************************
* Macros
****************************************************************************/
/****************************************************************************
* Name: up_fullcontextrestore
*
* Descripion:
* Restore the full-running contex of a thread.
*
* NOTE: Thus function must handle one very strange case. That is when
* this function is called with up_sigdeliver(). That case is strange in
* two ways:
*
* 1. It is not a context switch between threads. Rather, up_fullcontextrestore
* must behave more it more like a longjmp within the same task, using the
* same stack.
* 2. In this case, this function is called with r12 pointing to a register
* save area on the stack to be destroyed. This is dangerous for two
* reasons: (a) there is a period of time where the stack contents still
* contain valid data, but are outside of range protected by the stack
* pointer (hence, interrupts must be disabled), and (b) there is the
* very real possibility that the new stack pointer might overlap with
* the register save area and stack usage in this function might corrupt
* the register save data before the state is restored.
*
* Input Parameters:
* r12 = A pointer to the register save area of the thread to be restored.
*
* C Prototype:
* void up_fullcontextrestore(uint32_t *regs);
*
* Assumptions:
* Interrupts are disabled.
*
****************************************************************************/
.text
.global up_fullcontextrestore
.type up_fullcontextrestore, @function
up_fullcontextrestore:
/* Initially, r12 points to the r7 save area. Restore r0-r7. */
/* regs: 07 06 05 04 03 02 01 00 xx xx xx xx xx xx xx xx xx */
/* ^r12 */
ldm r12++, r0-r7
/* Now, r12 points to the SP (r13) save area. Recover the value of */
/* the stack pointer (r13). We will need to save some temporaries on */
/* the final stack. */
/* regs: 07 06 05 04 03 02 01 00 SP xx xx xx xx xx xx xx xx */
/* ^r12 */
ld.w sp, r12++
/* Now r12 points to the SR save area. Skip over the SR for now. */
/* regs: 07 06 05 04 03 02 01 00 SP xx xx xx xx xx xx xx xx */
/* ^r12 */
sub r12, -1*4
/* Get the pc, lr, and r12 (in r10, r9, and r8) and move them to the */
/* stack. We can now use r12 and lr as scratch registers. */
/* regs: 07 06 05 04 03 02 01 00 SP xx PC LR 12 xx xx xx xx */
/* ^r12 */
/* stack: lr, r12, pc */
/* ^sp */
ldm r12++, r8-r10 /* Get r10=pc, r9=lr, r8=r12 */
#if 0 /* See comments below */
stm --sp, r8-r10 /* Save r12, lr, and pc from the stack */
#else
st.w --sp, r10 /* Save R10=PC on the stack */
st.w --sp, r8 /* Save R8=r12 on the stack */
st.w --sp, r9 /* Save R9=lr on the stack */
#endif
/* Now r12 now points to the r11 save area. Restore r8-r11. */
/* regs: 07 06 05 04 03 02 01 00 SP xx PC LR 12 11 10 09 08 */
/* ^r12 */
ldm r12++, r8-r11
/* r12 now points +4 beyond the end of the register save area. Restore */
/* SR. NOTE: This may enable interrupts! */
/* regs: 07 06 05 04 03 02 01 00 SP SR PC LR 12 11 10 09 08 */
/* ^r12-4*8 ^r12 */
ld.w lr, r12[-4*8]
mtsr AVR32_SR, lr
/* Restore PC, LR and r12. Hmmm.. I need to study the behaviour of ldm */
/* when r12,lr, and pc on in ldm reglist16. I'm not sure that I want */
/* that behavior. */
/* stack: lr, r12, pc */
/* ^sp */
#if 0
ldm sp++, r12, lr, pc /* Restore r12, lr, and pc from the stack */
#else
ld.w lr, sp++ /* Recover lr from the stack */
ld.w r12, sp++ /* Recover r12 from the stack */
ld.w pc, sp++ /* Jump to the address on the stack */
#endif
.end
