/**************************************************************************** * arch/arm/src/armv7-a/arm_syscall.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 /* 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 #include #include #include #include #include #include #include #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