/****************************************************************************
* arch/arm/src/armv7-a/arm_fullcontextrestore.S
*
* Copyright (C) 2013 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 <nuttx/irq.h>
#include "up_internal.h"
#include "svcall.h"
.file "arm_fullcontextrestore.S"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Public Symbols
****************************************************************************/
.globl up_fullcontextrestore
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_fullcontextrestore
*
* Description:
* Restore the specified task context. Full prototype is:
*
* void up_fullcontextrestore(uint32_t *restoreregs) noreturn_function;
*
* Return:
* None
*
****************************************************************************/
.globl up_fullcontextrestore
.type up_fullcontextrestore, function
up_fullcontextrestore:
/* On entry, a1 (r0) holds address of the register save area. All other
* registers are available for use.
*/
#ifdef CONFIG_ARCH_FPU
/* First, restore the floating point registers. Lets do this before we
* restore the ARM registers so that we have plenty of registers to
* work with.
*/
add r1, r0, #(4*REG_S0) /* r1=Address of FP register storage */
/* Load all floating point registers. Registers are loaded in numeric order,
* s0, s1, ... in increasing address order.
*/
vldmia r1!, {s0-s31} /* Restore the full FP context */
/* Load the floating point control and status register. At the end of the
* vstmia, r1 will point to the FPCSR storage location.
*/
ldr r2, [r1], #4 /* Fetch the floating point control and status register */
vmsr fpscr, r2 /* Restore the FPCSR */
#endif
#ifdef CONFIG_BUILD_KERNEL
/* For the kernel build, we need to be able to transition gracefully
* between kernel- and user-mode tasks. Here we do that with a system
* call; the system call will execute in kernel mode and but can return
* to either user or kernel mode.
*/
/* Perform the System call with R0=SYS_context_restore, R1=restoreregs */
mov r1, r0 /* R1: restoreregs */
mov r0, #SYS_context_restore /* R0: SYS_context_restore syscall */
svc #0x900001 /* Perform the system call */
/* This call should not return */
bx lr /* Unnecessary ... will not return */
#else
/* For a flat build, we can do all of this here... Just think of this as
* a longjmp() all on steriods.
*/
/* Recover all registers except for r0, r1, R15, and CPSR */
add r1, r0, #(4*REG_R2) /* Offset to REG_R2 storage */
ldmia r1, {r2-r14} /* Recover registers */
/* Create a stack frame to hold the some registers */
sub sp, sp, #(3*4) /* Frame for three registers */
ldr r1, [r0, #(4*REG_R0)] /* Fetch the stored r0 value */
str r1, [sp] /* Save it at the top of the stack */
ldr r1, [r0, #(4*REG_R1)] /* Fetch the stored r1 value */
str r1, [sp, #4] /* Save it in the stack */
ldr r1, [r0, #(4*REG_PC)] /* Fetch the stored pc value */
str r1, [sp, #8] /* Save it at the bottom of the frame */
/* Now we can restore the CPSR. We wait until we are completely
* finished with the context save data to do this. Restore the CPSR
* may re-enable and interrupts and we could be in a context
* where the save structure is only protected by interrupts being
* disabled.
*/
ldr r1, [r0, #(4*REG_CPSR)] /* Fetch the stored CPSR value */
msr cpsr, r1 /* Set the CPSR */
/* Now recover r0 and r1 */
ldr r0, [sp]
ldr r1, [sp, #4]
add sp, sp, #(2*4)
/* Then return to the address at the stop of the stack,
* destroying the stack frame
*/
ldr pc, [sp], #4
#endif
.size up_fullcontextrestore, . - up_fullcontextrestore
