lab01: xv6 and Unix utilities

preparations

环境配置：

$ conda activate os

编译：

$ make qemu

gcc版本太新有可能会报-Werror=infinite-recursion：

(os) xv6-labs-2021$ gcc --version
gcc (conda-forge gcc 11.4.0-13) 11.4.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
(os) xv6-labs-2021$ make qemu
riscv64-linux-gnu-gcc -Wall -Werror -O -fno-omit-frame-pointer -ggdb -DSOL_UTIL -DLAB_UTIL -MD -mcmodel=medany -ffreestanding -fno-common -nostdlib -mno-relax -I. -fno-stack-protector -fno-pie -no-pie   -c -o user/sh.o user/sh.c
user/sh.c: In function ‘runcmd’:
user/sh.c:58:1: error: infinite recursion detected [-Werror=infinite-recursion]
   58 | runcmd(struct cmd *cmd)
      | ^~~~~~
user/sh.c:89:5: note: recursive call
   89 |     runcmd(rcmd->cmd);
      |     ^~~~~~~~~~~~~~~~~
user/sh.c:109:7: note: recursive call
  109 |       runcmd(pcmd->left);
      |       ^~~~~~~~~~~~~~~~~~
user/sh.c:116:7: note: recursive call
  116 |       runcmd(pcmd->right);
      |       ^~~~~~~~~~~~~~~~~~~
user/sh.c:95:7: note: recursive call
   95 |       runcmd(lcmd->left);
      |       ^~~~~~~~~~~~~~~~~~
user/sh.c:97:5: note: recursive call
   97 |     runcmd(lcmd->right);
      |     ^~~~~~~~~~~~~~~~~~~
user/sh.c:127:7: note: recursive call
  127 |       runcmd(bcmd->cmd);
      |       ^~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make: *** [<builtin>: user/sh.o] Error 1

此时可以在第58行的runcmd函数之前加上声明：

__attribute__((noreturn))

重新编译看到这个就算成功：

xv6 kernel is booting

hart 1 starting
hart 2 starting
init: starting sh
$

Boot xv6 (Easy)