/****************************************************************************
* arch/arm/src/armv7-a/arm_syscall.c
*
* Copyright (C) 2013-2014 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>
/* Output debug info if stack dump is selected -- even if debug is not
* selected.
*/
#ifdef CONFIG_ARCH_STACKDUMP
# undef CONFIG_DEBUG
# undef CONFIG_DEBUG_VERBOSE
# define CONFIG_DEBUG 1
# define CONFIG_DEBUG_VERBOSE 1
#endif
#include <stdint.h>
#include <string.h>
#include <syscall.h>
#include <assert.h>
#include <debug.h>
#include <arch/irq.h>
#include <nuttx/sched.h>
#include <nuttx/addrenv.h>
#include "arm.h"
#include "svcall.h"
#include "addrenv.h"
#include "up_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Debug ********************************************************************/
#if defined(CONFIG_DEBUG_SYSCALL)
# define svcdbg(format, ...) lldbg(format, ##__VA_ARGS__)
#else
# define svcdbg(x...)
#endif
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Name: dispatch_syscall
*
* Description:
* Call the stub function corresponding to the system call. NOTE the non-
* standard parameter passing:
*
* R0 = SYS_ call number
* R1 = parm0
* R2 = parm1
* R3 = parm2
* R4 = parm3
* R5 = parm4
* R6 = parm5
*
* The values of R4-R5 may be preserved in the proxy called by the user
* code if they are used (but otherwise will not be).
*
* WARNING: There are hard-coded values in this logic!
*
* Register usage:
*
* R0 - Need not be preserved.
* 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. R4-R6 may have been preserved by the proxy, but don't know
* for sure.
* R12 - Need not be preserved
* R13 - (stack pointer)
* R14 - Need not be preserved
* R15 - (PC)
*
****************************************************************************/
#ifdef CONFIG_LIB_SYSCALL
static void dispatch_syscall(void) naked_function;
static void dispatch_syscall(void)
{
__asm__ __volatile__
(
" sub sp, sp, #16\n" /* Create a stack frame to hold 3 parms + lr */
" str r4, [sp, #0]\n" /* Move parameter 4 (if any) into position */
" str r5, [sp, #4]\n" /* Move parameter 5 (if any) into position */
" str r6, [sp, #8]\n" /* Move parameter 6 (if any) into position */
" str lr, [sp, #12]\n" /* Save lr in the stack frame */
" ldr ip, =g_stublookup\n" /* R12=The base of the stub lookup table */
" ldr ip, [ip, r0, lsl #2]\n" /* R12=The address of the stub for this SYSCALL */
" blx ip\n" /* Call the stub (modifies lr)*/
" ldr lr, [sp, #12]\n" /* Restore lr */
" add sp, sp, #16\n" /* Destroy the stack frame */
" mov r2, r0\n" /* R2=Save return value in R2 */
" mov r0, #0\n" /* R0=SYS_syscall_return */
" svc #0x900001\n" /* Return from the SYSCALL */
);
}
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: arm_syscall
*
* Description:
* SVC interrupts will vector here with insn=the SVC instruction and
* xcp=the interrupt context
*
* The handler may get the SVC number be de-referencing the return
* address saved in the xcp and decoding the SVC instruction
*
****************************************************************************/
#ifdef CONFIG_LIB_SYSCALL
uint32_t *arm_syscall(uint32_t *regs)
{
uint32_t cmd;
#ifdef CONFIG_BUILD_KERNEL
uint32_t cpsr;
#endif
/* Nested interrupts are not supported */
DEBUGASSERT(regs);
/* The SYSCALL command is in R0 on entry. Parameters follow in R1..R7 */
cmd = regs[REG_R0];
/* The SVCall software interrupt is called with R0 = system call command
* and R1..R7 = variable number of arguments depending on the system call.
*/
#if defined(CONFIG_DEBUG_SYSCALL)
svcdbg("SYSCALL Entry: regs: %p cmd: %d\n", regs, cmd);
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]);
svcdbg("CPSR: %08x\n", regs[REG_CPSR]);
#endif
/* Handle the SVCall according to the command in R0 */
switch (cmd)
{
/* 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.
*/
case SYS_syscall_return:
{
FAR struct tcb_s *rtcb = sched_self();
int index = (int)rtcb->xcp.nsyscalls - 1;
/* Make sure that there is a saved SYSCALL return address. */
DEBUGASSERT(index >= 0);
/* Setup to return to the saved SYSCALL return address in
* the original mode.
*/
regs[REG_PC] = rtcb->xcp.syscall[index].sysreturn;
#ifdef CONFIG_BUILD_KERNEL
regs[REG_CPSR] = rtcb->xcp.syscall[index].cpsr;
#endif
/* The return value must be in R0-R1. dispatch_syscall() temporarily
* moved the value for R0 into R2.
*/
regs[REG_R0] = regs[REG_R2];
#ifdef CONFIG_ARCH_KERNEL_STACK
/* If this is the outermost SYSCALL and if there is a saved user stack
* pointer, then restore the user stack pointer on this final return to
* user code.
*/
if (index == 0 && rtcb->xcp.ustkptr != NULL)
{
regs[REG_SP] = (uint32_t)rtcb->xcp.ustkptr;
rtcb->xcp.ustkptr = NULL;
}
#endif
/* Save the new SYSCALL nesting level */
rtcb->xcp.nsyscalls = index;
}
break;
/* R0=SYS_context_restore: Restore task context
*
* void up_fullcontextrestore(uint32_t *restoreregs) noreturn_function;
*
* At this point, the following values are saved in context:
*
* R0 = SYS_context_restore
* R1 = restoreregs
*/
#ifdef CONFIG_BUILD_KERNEL
case SYS_context_restore:
{
/* Replace 'regs' with the pointer to the register set in
* regs[REG_R1]. On return from the system call, that register
* set will determine the restored context.
*/
regs = (uint32_t *)regs[REG_R1];
DEBUGASSERT(regs);
}
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_BUILD_KERNEL
case SYS_task_start:
{
/* Set up to return to the user-space _start function in
* unprivileged mode. We need:
*
* R0 = argc
* R1 = argv
* PC = taskentry
* CSPR = user mode
*/
regs[REG_PC] = regs[REG_R1];
regs[REG_R0] = regs[REG_R2];
regs[REG_R1] = regs[REG_R3];
cpsr = regs[REG_CPSR] & ~PSR_MODE_MASK;
regs[REG_CPSR] = cpsr | PSR_MODE_USR;
}
break;
#endif
/* R0=SYS_pthread_start: This a user pthread start
*
* void up_pthread_start(pthread_startroutine_t entrypt, pthread_addr_t arg) noreturn_function;
*
* At this point, the following values are saved in context:
*
* R0 = SYS_pthread_start
* R1 = entrypt
* R2 = arg
*/
#if defined(CONFIG_BUILD_KERNEL) && !defined(CONFIG_DISABLE_PTHREAD)
case SYS_pthread_start:
{
/* Set up to return to the user-space pthread start-up function in
* unprivileged mode. We need:
*
* R0 = arg
* PC = entrypt
* CSPR = user mode
*/
regs[REG_PC] = regs[REG_R1];
regs[REG_R0] = regs[REG_R2];
cpsr = regs[REG_CPSR] & ~PSR_MODE_MASK;
regs[REG_CPSR] = cpsr | PSR_MODE_USR;
}
break;
#endif
#if defined(CONFIG_BUILD_KERNEL) && !defined(CONFIG_DISABLE_SIGNALS)
/* R0=SYS_signal_handler: This a user signal handler callback
*
* void signal_handler(_sa_sigaction_t sighand, int signo,
* FAR siginfo_t *info, FAR void *ucontext);
*
* At this point, the following values are saved in context:
*
* R0 = SYS_signal_handler
* R1 = sighand
* R2 = signo
* R3 = info
* ucontext (on the stack)
*/
case SYS_signal_handler:
{
FAR struct tcb_s *rtcb = sched_self();
/* Remember the caller's return address */
DEBUGASSERT(rtcb->xcp.sigreturn == 0);
rtcb->xcp.sigreturn = regs[REG_PC];
/* Set up to return to the user-space pthread start-up function in
* unprivileged mode.
*/
regs[REG_PC] = (uint32_t)ARCH_DATA_RESERVE->ar_sigtramp;
cpsr = regs[REG_CPSR] & ~PSR_MODE_MASK;
regs[REG_CPSR] = cpsr | PSR_MODE_USR;
/* Change the parameter ordering to match the expectation of struct
* userpace_s signal_handler.
*/
regs[REG_R0] = regs[REG_R1]; /* sighand */
regs[REG_R1] = regs[REG_R2]; /* signal */
regs[REG_R2] = regs[REG_R3]; /* info */
/* The last parameter, ucontext, is trickier. The ucontext
* parameter will reside at an offset of 4 from the stack pointer.
*/
regs[REG_R3] = *(uint32_t*)(regs[REG_SP]+4);
#ifdef CONFIG_ARCH_KERNEL_STACK
/* If we are signalling a user process, then we must be operating
* on the kernel stack now. We need to switch back to the user
* stack before dispatching the signal handler to the user code.
* The existence of an allocated kernel stack is sufficient
* information to make this decision.
*/
if (rtcb->xcp.kstack != NULL)
{
DEBUGASSERT(rtcb->xcp.kstkptr == NULL && rtcb->xcp.ustkptr != NULL);
rtcb->xcp.kstkptr = (FAR uint32_t *)regs[REG_SP];
regs[REG_SP] = (uint32_t)rtcb->xcp.ustkptr;
}
#endif
}
break;
#endif
#if defined(CONFIG_BUILD_KERNEL) && !defined(CONFIG_DISABLE_SIGNALS)
/* R0=SYS_signal_handler_return: This a user signal handler callback
*
* void signal_handler_return(void);
*
* At this point, the following values are saved in context:
*
* R0 = SYS_signal_handler_return
*/
case SYS_signal_handler_return:
{
FAR struct tcb_s *rtcb = sched_self();
/* Set up to return to the kernel-mode signal dispatching logic. */
DEBUGASSERT(rtcb->xcp.sigreturn != 0);
regs[REG_PC] = rtcb->xcp.sigreturn;
cpsr = regs[REG_CPSR] & ~PSR_MODE_MASK;
regs[REG_CPSR] = cpsr | PSR_MODE_SVC;
rtcb->xcp.sigreturn = 0;
#ifdef CONFIG_ARCH_KERNEL_STACK
/* We must enter here be using the user stack. We need to switch
* to back to the kernel user stack before returning to the kernel
* mode signal trampoline.
*/
if (rtcb->xcp.kstack != NULL)
{
DEBUGASSERT(rtcb->xcp.kstkptr != NULL &&
(uint32_t)rtcb->xcp.ustkptr == regs[REG_SP]);
regs[REG_SP] = (uint32_t)rtcb->xcp.kstkptr;
rtcb->xcp.kstkptr = NULL;
}
#endif
}
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_LIB_SYSCALL
FAR struct tcb_s *rtcb = sched_self();
int index = rtcb->xcp.nsyscalls;
/* Verify that the SYS call number is within range */
DEBUGASSERT(cmd >= CONFIG_SYS_RESERVED && cmd < SYS_maxsyscall);
/* Make sure that there is a no saved SYSCALL return address. We
* cannot yet handle nested system calls.
*/
DEBUGASSERT(index < CONFIG_SYS_NNEST);
/* Setup to return to dispatch_syscall in privileged mode. */
rtcb->xcp.syscall[index].sysreturn = regs[REG_PC];
#ifdef CONFIG_BUILD_KERNEL
rtcb->xcp.syscall[index].cpsr = regs[REG_CPSR];
#endif
regs[REG_PC] = (uint32_t)dispatch_syscall;
#ifdef CONFIG_BUILD_KERNEL
cpsr = regs[REG_CPSR] & ~PSR_MODE_MASK;
regs[REG_CPSR] = cpsr | PSR_MODE_SVC;
#endif
/* Offset R0 to account for the reserved values */
regs[REG_R0] -= CONFIG_SYS_RESERVED;
#else
svcdbg("ERROR: Bad SYS call: %d\n", regs[REG_R0]);
#endif
#ifdef CONFIG_ARCH_KERNEL_STACK
/* If this is the first SYSCALL and if there is an allocated
* kernel stack, then switch to the kernel stack.
*/
if (index == 0 && rtcb->xcp.kstack != NULL)
{
rtcb->xcp.ustkptr = (FAR uint32_t *)regs[REG_SP];
regs[REG_SP] = (uint32_t)rtcb->xcp.kstack + ARCH_KERNEL_STACKSIZE;
}
#endif
/* Save the new SYSCALL nesting level */
rtcb->xcp.nsyscalls = index + 1;
}
break;
}
#if defined(CONFIG_DEBUG_SYSCALL)
/* Report what happened */
svcdbg("SYSCALL Exit: regs: %p\n", regs);
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]);
svcdbg("CPSR: %08x\n", regs[REG_CPSR]);
#endif
/* Return the last value of curent_regs. This supports context switches
* on return from the exception. That capability is only used with the
* SYS_context_switch system call.
*/
return regs;
}
#else
uint32_t *arm_syscall(uint32_t *regs)
{
lldbg("SYSCALL from 0x%x\n", regs[REG_PC]);
current_regs = regs;
PANIC();
}
#endif
