/**************************************************************************** * arch/arm/src/armv6-m/up_svcall.c * * Copyright (C) 2013-2014 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #include #ifdef CONFIG_LIB_SYSCALL # include #endif #include "svcall.h" #include "exc_return.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 (shows only syscalls) * - CONFIG_DEBUG and CONFIG_DEBUG_SVCALL (shows everything) */ #if defined(CONFIG_DEBUG_SYSCALL) || defined(CONFIG_DEBUG_SVCALL) # define svcdbg(format, ...) lldbg(format, ##__VA_ARGS__) #else # define svcdbg(x...) #endif /**************************************************************************** * Private Data ****************************************************************************/ /**************************************************************************** * Public Data ****************************************************************************/ /**************************************************************************** * 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 r5\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, #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; uint32_t cmd; DEBUGASSERT(regs && regs == current_regs); 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) || defined(CONFIG_DEBUG_SVCALL) # ifndef CONFIG_DEBUG_SVCALL if (cmd > SYS_switch_context) # endif { svcdbg("SVCALL 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]); # ifdef CONFIG_BUILD_PROTECTED svcdbg(" PSR: %08x PRIMASK: %08x EXC_RETURN: %08x\n", regs[REG_XPSR], regs[REG_PRIMASK], regs[REG_EXC_RETURN]); # else svcdbg(" PSR: %08x PRIMASK: %08x\n", regs[REG_XPSR], regs[REG_PRIMASK]); # endif } #endif /* Handle the SVCall according to the command in R0 */ switch (cmd) { /* 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_LIB_SYSCALL case SYS_syscall_return: { 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; regs[REG_EXC_RETURN] = rtcb->xcp.syscall[index].excreturn; 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]; } 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_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_UNPRIVTHR; /* 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_PROTECTED) && !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)USERSPACE->pthread_startup; regs[REG_EXC_RETURN] = EXC_RETURN_UNPRIVTHR; /* Change the parameter ordering to match the expectation of struct * userpace_s pthread_startup: */ regs[REG_R0] = regs[REG_R1]; /* pthread entry */ regs[REG_R1] = regs[REG_R2]; /* arg */ } break; #endif /* 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) */ #if defined(CONFIG_BUILD_PROTECTED) && !defined(CONFIG_DISABLE_SIGNALS) case SYS_signal_handler: { 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)USERSPACE->signal_handler; regs[REG_EXC_RETURN] = EXC_RETURN_UNPRIVTHR; /* 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); } 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 */ #if defined(CONFIG_BUILD_PROTECTED) && !defined(CONFIG_DISABLE_SIGNALS) case SYS_signal_handler_return: { 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; regs[REG_EXC_RETURN] = EXC_RETURN_PRIVTHR; 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 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]; rtcb->xcp.syscall[index].excreturn = regs[REG_EXC_RETURN]; rtcb->xcp.nsyscalls = index + 1; 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 defined(CONFIG_DEBUG_SYSCALL) || defined(CONFIG_DEBUG_SVCALL) # ifndef CONFIG_DEBUG_SVCALL if (cmd > SYS_switch_context) # else if (regs != current_regs) # endif { svcdbg("SVCall Return:\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_BUILD_PROTECTED svcdbg(" PSR: %08x PRIMASK: %08x EXC_RETURN: %08x\n", current_regs[REG_XPSR], current_regs[REG_PRIMASK], current_regs[REG_EXC_RETURN]); #else svcdbg(" PSR: %08x PRIMASK: %08x\n", current_regs[REG_XPSR], current_regs[REG_PRIMASK]); #endif } # ifdef CONFIG_DEBUG_SVCALL else { svcdbg("SVCall Return: %d\n", regs[REG_R0]); } # endif #endif return OK; }