Week 4

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1. Linux

Implement lazy allocation, which will only allocate resource until it is actually needed. That is, sbrk function doesn't allocate physical memory, but just remembers which addresses are allocated. When the process first tries to use any given page of memory, the CPU generates a page fault, which the kernel handles by allocating physical memory, zeroing it, and mapping it.


2. Bootloader

It was found that the u-boot transplantation tutorial on the Internet was performed on the Samsung template, which is different from the source code used by risc-v.


3. SoC

  1. Discuss how the operating system communicate with the CPU (system call)
  2. Search information to solve the problem of DDR2 SDRAM, which cause the whole project not to meet the expectation progress.
  3. Replace on chip DDR2 RAM with LUT RAM and Block RAM
    1. Can not support the compile file of operating system. Therefore, memory support is necessary

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Week 1

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1. Linux Install the running environment (including riscv32-unknown-elf-gcc and qemu-system-riscv32). riscv32-unknown-elf-gcc is the cross compile, which can compile the operating system source code so that it can be used in 32 bit RISC-V. Qemu-system-riscv32 can simulate the 32 bit RISC-V environment on Ubuntu. Therefore, we can test the correctness of operating system without a completed CPU.  After finishing the installation, write a simple C program to test the correctness. Firstly, use the riscv32-unknown-elf-gcc to compile the source code and generate an executable file. Then, use qemu-system-riscv32 to run this executable file. This process is shown in following figure. 2. Bootloader Read the book called <Computer Organization and Design RISC-V Edition: The Hardware Software Interface>. This is a thick book for me to read it because I lack knowledge of computer systems. I particularly focused on the second part <Instruction: Language...
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Week 2

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1. Linux Implement several shell commands, such as sleep , pingpong , primes , find and xargs . 1. sleep can pause the operating system for a given time. (eg. sleep 100: the system will pause for 10 second) 2. pingpong can transmit a byte message between two processors via a pair of pipes, parent_pipe and child_pipe , one for each direction (in and out). The parent process will write message to parent_pipe[1] and the child receive this message from parent_pipe[0] . Then child responds with writing a message to child_pipe[1] and parent can read from child_pipe[0]. 3. primes is based on the idea Unix Pipes .  The first process feeds the numbers 2 through 35 into the pipeline. For each prime number, you will arrange to create one process that reads from its left neighbor over a pipe and writes to its right neighbor over another pipe. All the numbers can be divided by the prime number will be discarded as shown in the following figure.  Figure 1: the function of...
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