xiaoxiang781216 commented on a change in pull request #5782: URL: https://github.com/apache/incubator-nuttx/pull/5782#discussion_r837807826
########## 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: Review comment: > I personally prefer this, it is a simple context save to 1 location (a0) and does not need to involve a system call. But, the most portion of code is to simulate ECALL which is same as riscv_syscall_dispatch. Once the simulation is done, riscv_handle_syscall is just a simple switch case statement. > This is just faster, even though it duplicates a bit of code. > Yes, it could save some instruction, but is very small. On the other hand, it duplicated a lot of code and make the code hard to maintain. > If duplicated code is to be removed at all expense then I guess it can be done. In that case it would be the same as simulating ecall but with a trampoline. -- 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
