/****************************************************************************
* arch/arm/src/armv6-m/up_svcall.c
*
* 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 <stdint.h>
#include <string.h>
#include <assert.h>
#include <debug.h>
#include <arch/irq.h>
#include <nuttx/sched.h>
#ifdef CONFIG_NUTTX_KERNEL
# include <syscall.h>
#endif
#include "svcall.h"
#include "exc_return.h"
#include "os_internal.h"
#include "up_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Configuration ************************************************************/
/* Debug ********************************************************************/
/* Debug output from this file may interfere with context switching! To get
* debug output you must enabled the following in your NuttX configuration:
*
* CONFIG_DEBUG and CONFIG_DEBUG_SYSCALL
*/
#ifdef CONFIG_DEBUG_SYSCALL
# define svcdbg(format, arg...) lldbg(format, ##arg)
#else
# define svcdbg(x...)
#endif
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Public Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: dispatch_syscall
*
* Description:
* Call the stub function corresponding to the system call.
*
* R0 - Need not be preserved until after the stub is called.
* R1-R3 - Need to be preserved until the stub is called. The values of
* R0 and R1 returned by the stub must be preserved.
* R4-R11 must be preserved to support the expectations of the user-space
* callee
* R12 - Need not be preserved
* R13 - (stack pointer)
* R14 - Need not be preserved
* R15 - (PC)
*
****************************************************************************/
#ifdef CONFIG_NUTTX_KERNEL
static void dispatch_syscall(void) naked_function;
static void dispatch_syscall(void)
{
__asm__ __volatile__
(
" push {r4, r5}\n" /* Save R4 and R5 */
" mov r5, lr\n" /* Save lr in R5 */
" ldr r4, =g_stublookup\n" /* R4=The base of the stub lookup table */
" lsl r0, r0, #2\n" /* R0=Offset of the stub for this syscall */
" ldr r4, [r4, r0]\n" /* R4=Address of the stub for this syscall */
" blx r5\n" /* Call the stub (modifies lr) */
" mov lr, r5\n" /* Restore lr */
" pop {r4, r5}\n" /* Restore R4 and R5*/
" mov r2, r0\n" /* R2=Saves return value in R0 */
" mov r0, #3\n" /* R0=SYS_syscall_return */
" svc 0" /* Return from the syscall */
);
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_svcall
*
* Description:
* This is SVCall exception handler that performs context switching
*
****************************************************************************/
int up_svcall(int irq, FAR void *context)
{
uint32_t *regs = (uint32_t*)context;
DEBUGASSERT(regs && regs == current_regs);
/* The SVCall software interrupt is called with R0 = system call command
* and R1..R7 = variable number of arguments depending on the system call.
*/
svcdbg("SVCALL Entry: regs: %p cmd: %d\n", regs, regs[REG_R0]);
svcdbg(" R0: %08x %08x %08x %08x %08x %08x %08x %08x\n",
regs[REG_R0], regs[REG_R1], regs[REG_R2], regs[REG_R3],
regs[REG_R4], regs[REG_R5], regs[REG_R6], regs[REG_R7]);
svcdbg(" R8: %08x %08x %08x %08x %08x %08x %08x %08x\n",
regs[REG_R8], regs[REG_R9], regs[REG_R10], regs[REG_R11],
regs[REG_R12], regs[REG_R13], regs[REG_R14], regs[REG_R15]);
#ifdef CONFIG_NUTTX_KERNEL
svcdbg("xPSR: %08x BASEPRI: %08x EXEC_RETURN: %08x\n",
regs[REG_XPSR], regs[REG_BASEPRI], regs[REG_EXC_RETURN]);
#else
svcdbg("xPSR: %08x BASEPRI: %08x\n",
regs[REG_XPSR], regs[REG_BASEPRI]);
#endif
/* Handle the SVCall according to the command in R0 */
switch (regs[REG_R0])
{
/* R0=SYS_save_context: This is a save context command:
*
* int up_saveusercontext(uint32_t *saveregs);
*
* At this point, the following values are saved in context:
*
* R0 = SYS_save_context
* R1 = saveregs
*
* In this case, we simply need to copy the current regsters to the
* save register space references in the saved R1 and return.
*/
case SYS_save_context:
{
DEBUGASSERT(regs[REG_R1] != 0);
memcpy((uint32_t*)regs[REG_R1], regs, XCPTCONTEXT_SIZE);
}
break;
/* R0=SYS_restore_context: This a restore context command:
*
* void up_fullcontextrestore(uint32_t *restoreregs) noreturn_function;
*
* At this point, the following values are saved in context:
*
* R0 = SYS_restore_context
* R1 = restoreregs
*
* In this case, we simply need to set current_regs to restore register
* area referenced in the saved R1. context == current_regs is the normal
* exception return. By setting current_regs = context[R1], we force
* the return to the saved context referenced in R1.
*/
case SYS_restore_context:
{
DEBUGASSERT(regs[REG_R1] != 0);
current_regs = (uint32_t*)regs[REG_R1];
}
break;
/* R0=SYS_switch_context: This a switch context command:
*
* void up_switchcontext(uint32_t *saveregs, uint32_t *restoreregs);
*
* At this point, the following values are saved in context:
*
* R0 = SYS_switch_context
* R1 = saveregs
* R2 = restoreregs
*
* In this case, we do both: We save the context registers to the save
* register area reference by the saved contents of R1 and then set
* current_regs to to the save register area referenced by the saved
* contents of R2.
*/
case SYS_switch_context:
{
DEBUGASSERT(regs[REG_R1] != 0 && regs[REG_R2] != 0);
memcpy((uint32_t*)regs[REG_R1], regs, XCPTCONTEXT_SIZE);
current_regs = (uint32_t*)regs[REG_R2];
}
break;
/* R0=SYS_syscall_return: This a syscall return command:
*
* void up_syscall_return(void);
*
* At this point, the following values are saved in context:
*
* R0 = SYS_syscall_return
*
* We need to restore the saved return address and return in
* unprivileged thread mode.
*/
#ifdef CONFIG_NUTTX_KERNEL
case SYS_syscall_return:
{
struct tcb_s *rtcb = sched_self();
/* Make sure that we got here from a privileged thread and
* that there is a saved syscall return address.
*/
DEBUGASSERT(rtcb->xcp.sysreturn != 0 &&
regs[REG_EXC_RETURN] == EXC_RETURN_PRIVTHR);
/* Setup to return to the saved syscall return address in
* unprivileged mode.
*/
regs[REG_PC] = rtcb->xcp.sysreturn;
regs[REG_EXC_RETURN] = EXC_RETURN_UNPRIVTHR;
rtcb->xcp.sysreturn = 0;
/* The return value must be in R0-R1. dispatch_syscall() temporarily
* moved the value to R2.
*/
regs[REG_R0] = regs[REG_R2];
}
break;
#endif
/* R0=SYS_task_start: This a user task start
*
* void up_task_start(main_t taskentry, int argc, FAR char *argv[]) noreturn_function;
*
* At this point, the following values are saved in context:
*
* R0 = SYS_task_start
* R1 = taskentry
* R2 = argc
* R3 = argv
*/
#ifdef CONFIG_NUTTX_KERNEL
case SYS_task_start:
{
/* Set up to return to the user-space task start-up function in
* unprivileged mode.
*/
regs[REG_PC] = (uint32_t)USERSPACE->task_startup;
regs[REG_EXC_RETURN] = EXC_RETURN_UNPRIVTHR;
/* Change the paramter ordering to match the expection of struct
* userpace_s task_startup:
*/
regs[REG_R0] = regs[REG_R1]; /* Task entry */
regs[REG_R1] = regs[REG_R2]; /* argc */
regs[REG_R2] = regs[REG_R3]; /* argv */
}
break;
#endif
/* This is not an architecture-specific system call. If NuttX is built
* as a standalone kernel with a system call interface, then all of the
* additional system calls must be handled as in the default case.
*/
default:
{
#ifdef CONFIG_NUTTX_KERNEL
FAR struct tcb_s *rtcb = sched_self();
/* Verify the the SYS call number is within range */
DEBUGASSERT(regs[REG_R0] < SYS_maxsyscall);
/* Make sure that we got here from an unprivileged thread and that
* there is a no saved syscall return address.
*/
DEBUGASSERT(rtcb->xcp.sysreturn == 0 &&
regs[REG_EXC_RETURN] == EXC_RETURN_UNPRIVTHR);
/* Setup to return to dispatch_syscall in privileged mode. */
rtcb->xcp.sysreturn = regs[REG_PC];
regs[REG_PC] = (uint32_t)dispatch_syscall;
regs[REG_EXC_RETURN] = EXC_RETURN_PRIVTHR;
/* Offset R0 to account for the reserved values */
regs[REG_R0] -= CONFIG_SYS_RESERVED;
#else
slldbg("ERROR: Bad SYS call: %d\n", regs[REG_R0]);
#endif
}
break;
}
/* Report what happened. That might difficult in the case of a context switch */
if (regs != current_regs)
{
svcdbg("SVCall Return: Context switch!\n");
svcdbg(" R0: %08x %08x %08x %08x %08x %08x %08x %08x\n",
current_regs[REG_R0], current_regs[REG_R1], current_regs[REG_R2], current_regs[REG_R3],
current_regs[REG_R4], current_regs[REG_R5], current_regs[REG_R6], current_regs[REG_R7]);
svcdbg(" R8: %08x %08x %08x %08x %08x %08x %08x %08x\n",
current_regs[REG_R8], current_regs[REG_R9], current_regs[REG_R10], current_regs[REG_R11],
current_regs[REG_R12], current_regs[REG_R13], current_regs[REG_R14], current_regs[REG_R15]);
#ifdef CONFIG_NUTTX_KERNEL
svcdbg("xPSR: %08x BASEPRI: %08x EXEC_RETURN: %08x\n",
current_regs[REG_XPSR], current_regs[REG_BASEPRI],
current_regs[REG_EXC_RETURN]);
#else
svcdbg("xPSR: %08x BASEPRI: %08x\n",
current_regs[REG_XPSR], current_regs[REG_BASEPRI]);
#endif
}
else
{
svcdbg("SVCall Return: %d\n", regs[REG_R0]);
}
return OK;
}
