Merge pull request #4 from Richard-Qin-001/dev/shell

Rebuilt the system's underlying structure; it is now stable enough to merge. 

The system now supports a read-only file system and has a simple shell implemented.

2 files changed, 60 insertions, 0 deletions

diff --git a/docs/dev/dev_device.md b/docs/dev/dev_device.md
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+# Dev log
+## **3.Device Model & HAL:**
+* Interrupt Controller: PLIC:
+
+    * Implement the PLIC (Platform-Level Interrupt Controller) driver.
+
+    * Set the PLIC priority threshold and enable bits during the start() phase.
+
+    * Dispatch Cause 9 (External Interrupt) in kerneltrap/usertrap.
+
+* Character Device: Interrupt-Driven Console:
+
+    * Implement a Ring Buffer. uart_putc returns immediately after writing to the buffer.
+
+    * UART transmit interrupt: triggers when the serial port is idle, the ISR takes data from the Ring Buffer and writes it to the register.
+
+    * UART receive interrupt: triggers when a key is pressed, the ISR reads the character and wakes up the process waiting to read.
+
+* Block Device: VirtIO-Blk:
+
+    * Implement a block device driver for the PCI or MMIO transport layer according to the VirtIO 2.0 standard.
+
+    * DMA: Use the Buddy System to allocate contiguous memory as the descriptor table for the Virtqueue.
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diff --git a/docs/dev/dev_memory.md b/docs/dev/dev_memory.md
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+# Dev log 
+## **1. Process Management:** 
+The core architecture has been upgraded from a simple single queue to a Per-CPU scheduler, supporting multi-core concurrency. 
+
+* Process lifecycle: A complete process state machine has been implemented, including UNUSED, RUNNABLE, RUNNING, SLEEPING, and ZOMBIE states. 
+
+* Core operations: 
+    * fork(): process cloning, supporting COW (copy-on-write) isolation of memory space between parent and child processes. 
+    * exit(): process termination and resource cleanup. 
+    * wait(): parent process waits for child process to exit. 
+    * sleep()/wakeup(): channel-based sleep and wakeup mechanism. 
+
+* Scheduling algorithm: 
+    * O(1) priority scheduling has been implemented (supporting 4 priority queues). 
+
+    * Per-CPU RunQueue: each CPU has its own independent run queue. 
+
+    * Supports Work Stealing: idle CPUs can fetch tasks from other CPUs’ queues. 
+
+## **2. Memory Management:** 
+A complete virtual and physical memory management system has been implemented. 
+
+* Physical Memory (PMM): Implements the Buddy System, supporting memory allocation and deallocation in $2^n$ pages. 
+
+* Virtual Memory (VM): Based on RISC-V Sv39 paging mode. Provides secure data copying from user space to kernel space (copyin). 
+
+* COW (Copy-On-Write): During fork, only page table entries are copied and pages are set to read-only; writes trigger page faults for physical copy, greatly improving process creation efficiency. 
+
+* Kernel heap: Implements a Slab Allocator, providing efficient allocation of small objects (such as struct Proc). 
+
+## **3. Synchronization:**
+
+* Spinlock: Used to protect very short critical sections (e.g., scheduler lock, PMM lock), supports disabling interrupts to prevent deadlocks. 
+
+* Mutex (sleeping lock): Used for long critical sections (e.g., file I/O), allowing sleep while holding the lock. 
+
+* Lock Handoff: Implements a complex lock handoff mechanism in the scheduler to ensure atomicity of context switches. 
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