pussuw commented on a change in pull request #5782: URL: https://github.com/apache/incubator-nuttx/pull/5782#discussion_r837853635
########## File path: arch/risc-v/src/common/supervisor/riscv_context.S ########## @@ -0,0 +1,234 @@ +/**************************************************************************** + * arch/risc-v/src/common/supervisor/riscv_context.S + * + * 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. + * + ****************************************************************************/ + +.file "riscv_context.S" + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> +#include <arch/mode.h> + +#include "riscv_exception_macros.S" + +/**************************************************************************** + * Pre-processor Definitions + ****************************************************************************/ + +/**************************************************************************** + * Public Symbols + ****************************************************************************/ + + .globl riscv_saveusercontext + .globl riscv_fullcontextrestore + .globl riscv_switchcontext + .globl riscv_syscall_return + +/**************************************************************************** + * Name: riscv_saveusercontext + * + * Description: + * Save user context, partially destroys the caller's context + * + * C Function Prototype: + * int riscv_saveusercontext(uintptr_t *saveregs); + * + * Input Parameters: + * saveregs - Context to save + * + * Returned Value: + * 0 on context switch + * 1 on no context switch + * + * Assumptions: + * Global interrupts disabled by the caller. + * + ****************************************************************************/ + +.type riscv_saveusercontext, function + +riscv_saveusercontext: + + save_ctx a0 /* save context */ + + csrr s0, CSR_STATUS + REGSTORE s0, REG_INT_CTX(a0) /* save status */ + + REGSTORE x1, REG_EPC(a0) /* save ra to epc */ + REGSTORE sp, REG_SP(a0) /* original SP */ + +#ifdef CONFIG_ARCH_FPU + jal x1, riscv_savefpu /* FP registers */ + REGLOAD x1, REG_X1(a0) /* restore ra */ +#endif + + li s0, 1 /* return 1 (in context) */ + REGSTORE s0, REG_A0(a0) + REGLOAD s0, REG_S0(a0) /* restore s0 */ + + li a0, 0 /* return 0 (back to caller) */ + ret + +/**************************************************************************** + * Name: riscv_fullcontextrestore + * + * Description: + * Restore context + * + * C Function Prototype: + * void riscv_fullcontextrestore(uintptr_t *restoreregs) noreturn_function; + * + * Input Parameters: + * restoreregs - Context to restore + * + * Returned Value: + * None + * + * Assumptions: + * Global interrupts disabled by the caller. + * + ****************************************************************************/ + +.type riscv_fullcontextrestore, function + +riscv_fullcontextrestore: + +#ifdef CONFIG_ARCH_FPU + jal x1, riscv_restorefpu /* FP registers */ +#endif + + mv sp, a0 /* use sp, as a0 gets wiped */ + + REGLOAD s0, REG_EPC(sp) /* restore epc */ + csrw CSR_EPC, s0 + + /* Restore status register, but don't enable interrupts yet */ + + REGLOAD s0, REG_INT_CTX(sp) /* restore status */ + li s1, STATUS_IE /* move IE -> PIE */ + and s1, s0, s1 /* if (STATUS & IE) */ + beqz s1, 1f + li s1, ~STATUS_IE /* clear IE */ + and s0, s0, s1 + li s1, STATUS_PIE /* set PIE */ + or s0, s0, s1 + +1: + csrw CSR_STATUS, s0 + + load_ctx sp + + REGLOAD sp, REG_SP(sp) /* restore original sp */ + + /* return from exception, which updates the status register */ + + sret + +/**************************************************************************** + * Name: riscv_switchcontext + * + * Description: + * Restore user context + * + * C Function Prototype: + * void riscv_switchcontext(uintptr_t *saveregs, uintptr_t *restoreregs); + * + * Input Parameters: + * saveregs - Context to save + * restoreregs - Context to restore + * + * Returned Value: + * None + * + * Assumptions: + * Global interrupts disabled by the caller. + * + ****************************************************************************/ + +.type riscv_switchcontext, function + +riscv_switchcontext: + + /* Save old context to arg[0] */ + + save_ctx a0 /* save context */ + + REGSTORE x1, REG_EPC(a0) /* save ra to epc */ + REGSTORE sp, REG_SP(a0) /* original SP */ + + /* Set previous privilege, we are in privileged mode now */ + + csrr s0, CSR_STATUS /* read status register */ + li s1, STATUS_PPP /* set previous privilege */ + or s0, s0, s1 + li s1, ~STATUS_PIE /* clear previous interrupt enable */ + and s0, s0, s1 + REGSTORE s0, REG_INT_CTX(a0) /* store status to context */ + +#ifdef CONFIG_ARCH_FPU + jal x1, riscv_savefpu /* FP registers */ +#endif + + /* Load new context from arg[1] */ + + mv a0, a1 /* load from a1 */ + j riscv_fullcontextrestore /* restore context */ + +/**************************************************************************** + * Name: riscv_syscall_return + * + * Description: + * Return from system call to user task with user mode privileges + * + * C Function Prototype: + * void riscv_syscall_return(void); + * + * Input Parameters: + * Assumes the return value of the system call is in a0 + * + * Returned Value: + * Return value of system call is returned into contex + * + * Assumptions: + * User task is running system call in privileged mode, ready to resume + * the user task in unprivileged mode + * + ****************************************************************************/ + +.type riscv_syscall_return, function + +riscv_syscall_return: Review comment: Very well. I'll move the IRQ masking there. Need to see if something else is also needed, ecall / taking a trap does many implicit things which was / is simulated by the asm code -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@nuttx.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
