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walnux/arch/arm/armv6-m/arm_svcall.c
Luchian Mihai 7335b36eca
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walnux: moveout
2025-11-04 19:15:10 +02:00

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/****************************************************************************
* arch/arm/src/armv6-m/arm_svcall.c
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <inttypes.h>
#include <stdint.h>
#include <string.h>
#include <assert.h>
#include <debug.h>
#include <syscall.h>
#include <arch/irq.h>
#include <nuttx/macro.h>
#include <nuttx/sched.h>
#include "sched/sched.h"
#include "signal/signal.h"
#include "exc_return.h"
#include "arm_internal.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* 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).
*
* 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__
(
" push {r4, r5}\n" /* Save R4 and R5 */
" sub sp, sp, #12\n" /* Create a stack frame to hold 3 parms */
" 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 */
" 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 r4\n" /* Call the stub (modifies lr) */
" mov lr, r5\n" /* Restore lr */
" add sp, sp, #12\n" /* Destroy the stack frame */
" pop {r4, r5}\n" /* Recover R4 and R5 */
" mov r2, r0\n" /* R2=Save return value in R2 */
" mov r0, #" STRINGIFY(SYS_syscall_return) "\n" /* R0=SYS_syscall_return */
" svc #" STRINGIFY(SYS_syscall) "\n" /* Return from the SYSCALL */
);
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: arm_svcall
*
* Description:
* This is SVCall exception handler that performs context switching
*
****************************************************************************/
int arm_svcall(int irq, void *context, void *arg)
{
uint32_t *regs = (uint32_t *)context;
struct tcb_s *tcb;
uint32_t cmd;
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.
*/
#ifdef CONFIG_DEBUG_SYSCALL_INFO
# ifndef CONFIG_DEBUG_SVCALL
if (cmd > SYS_switch_context)
# endif
{
svcinfo("SVCALL Entry: regs: %p cmd: %d\n", regs, cmd);
svcinfo(" 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]);
svcinfo(" 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]);
svcinfo(" PSR: %08x PRIMASK: %08x EXC_RETURN: %08x\n",
regs[REG_XPSR], regs[REG_PRIMASK], regs[REG_EXC_RETURN]);
}
#endif
/* Handle the SVCall according to the command in R0 */
switch (cmd)
{
case SYS_restore_context:
case SYS_switch_context:
{
tcb = this_task();
restore_critical_section(tcb, this_cpu());
#ifdef CONFIG_DEBUG_SYSCALL_INFO
regs = tcb->xcp.regs;
#endif
}
break;
/* R0=SYS_syscall_return: This a syscall return command:
*
* void arm_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_LIB_SYSCALL
case SYS_syscall_return:
{
struct tcb_s *rtcb = this_task();
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;
regs[REG_EXC_RETURN] = rtcb->xcp.syscall[index].excreturn;
regs[REG_CONTROL] = rtcb->xcp.syscall[index].ctrlreturn;
rtcb->xcp.nsyscalls = index;
/* The return value must be in R0-R1. dispatch_syscall()
* temporarily moved the value for R0 into R2.
*/
regs[REG_R0] = regs[REG_R2];
/* Handle any signal actions that were deferred while processing
* the system call.
*/
rtcb->flags &= ~TCB_FLAG_SYSCALL;
nxsig_unmask_pendingsignal();
}
break;
#endif
/* R0=SYS_task_start: This a user task start
*
* void up_task_start(main_t taskentry, int argc, 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_PROTECTED
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_THREAD;
/* Return unprivileged mode */
regs[REG_CONTROL] = getcontrol() | CONTROL_NPRIV;
/* Change the parameter ordering to match the expectation 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
/* 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_FLAT) && !defined(CONFIG_DISABLE_PTHREAD)
case SYS_pthread_start:
{
/* Set up to return to the user-space pthread start-up function in
* unprivileged mode.
*/
regs[REG_PC] = (uint32_t)regs[REG_R1]; /* startup */
regs[REG_EXC_RETURN] = EXC_RETURN_THREAD;
/* Return unprivileged mode */
regs[REG_CONTROL] = getcontrol() | CONTROL_NPRIV;
/* Change the parameter ordering to match the expectation of the
* user space pthread_startup:
*/
regs[REG_R0] = regs[REG_R2]; /* pthread entry */
regs[REG_R1] = regs[REG_R3]; /* arg */
}
break;
#endif
/* R0=SYS_signal_handler: This a user signal handler callback
*
* void signal_handler(_sa_sigaction_t sighand, int signo,
* siginfo_t *info, void *ucontext);
*
* At this point, the following values are saved in context:
*
* R0 = SYS_signal_handler
* R1 = sighand
* R2 = signo
* R3 = info
* R4 = ucontext
*/
#ifdef CONFIG_BUILD_PROTECTED
case SYS_signal_handler:
{
struct tcb_s *rtcb = this_task();
/* 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 trampoline function in
* unprivileged mode.
*/
regs[REG_PC] = (uint32_t)USERSPACE->signal_handler;
regs[REG_EXC_RETURN] = EXC_RETURN_THREAD;
/* Return unprivileged mode */
regs[REG_CONTROL] = getcontrol() | CONTROL_NPRIV;
/* 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 */
regs[REG_R3] = regs[REG_R4]; /* ucontext */
}
break;
#endif
/* 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
*/
#ifdef CONFIG_BUILD_PROTECTED
case SYS_signal_handler_return:
{
struct tcb_s *rtcb = this_task();
/* Set up to return to the kernel-mode signal dispatching logic. */
DEBUGASSERT(rtcb->xcp.sigreturn != 0);
regs[REG_PC] = rtcb->xcp.sigreturn;
regs[REG_EXC_RETURN] = EXC_RETURN_THREAD;
/* Return privileged mode */
regs[REG_CONTROL] = getcontrol() & ~CONTROL_NPRIV;
rtcb->xcp.sigreturn = 0;
}
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
struct tcb_s *rtcb = this_task();
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];
rtcb->xcp.syscall[index].excreturn = regs[REG_EXC_RETURN];
rtcb->xcp.syscall[index].ctrlreturn = regs[REG_CONTROL];
rtcb->xcp.nsyscalls = index + 1;
regs[REG_PC] = (uint32_t)dispatch_syscall;
regs[REG_EXC_RETURN] = EXC_RETURN_THREAD;
/* Return privileged mode */
regs[REG_CONTROL] = getcontrol() & ~CONTROL_NPRIV;
/* Offset R0 to account for the reserved values */
regs[REG_R0] -= CONFIG_SYS_RESERVED;
/* Indicate that we are in a syscall handler. */
rtcb->flags |= TCB_FLAG_SYSCALL;
#else
svcerr("ERROR: Bad SYS call: %" PRId32 "\n", regs[REG_R0]);
#endif
}
break;
}
/* Report what happened. That might difficult in the case of a context
* switch.
*/
#ifdef CONFIG_DEBUG_SYSCALL_INFO
# ifndef CONFIG_DEBUG_SVCALL
if (cmd > SYS_switch_context)
# endif
{
svcinfo("SVCall Return:\n");
svcinfo(" 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]);
svcinfo(" 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]);
svcinfo(" PSR: %08x EXC_RETURN: %08x CONTROL: %08x\n",
regs[REG_XPSR], regs[REG_EXC_RETURN], regs[REG_CONTROL]);
}
#endif
UNUSED(tcb);
return OK;
}
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