NJU PA
Created Feb 21, 2025 - Last updated: Feb 21, 2025
Growing 🌿
nju PA
Computer Systems
PA 1
pa 1.1
运行第一个客户程序
问题1 错误信息
进入nemu文件夹，运行make run得到
+ CC src/nemu-main.c
+ CC src/engine/interpreter/init.c
+ CC src/engine/interpreter/hostcall.c
+ CC src/device/io/map.c
+ CC src/device/io/mmio.c
+ CC src/device/io/port-io.c
+ CC src/isa/riscv32/reg.c
+ CC src/isa/riscv32/inst.c
+ CC src/isa/riscv32/init.c
+ CC src/isa/riscv32/system/mmu.c
+ CC src/isa/riscv32/system/intr.c
+ CC src/isa/riscv32/logo.c
+ CC src/isa/riscv32/difftest/dut.c
+ CC src/cpu/cpu-exec.c
+ CC src/cpu/difftest/ref.c
+ CC src/cpu/difftest/dut.c
+ CC src/monitor/sdb/expr.c
+ CC src/monitor/sdb/watchpoint.c
+ CC src/monitor/sdb/sdb.c
+ CC src/monitor/monitor.c
+ CC src/utils/log.c
+ CC src/utils/disasm.c
+ CC src/utils/state.c
+ CC src/utils/timer.c
+ CC src/memory/paddr.c
+ CC src/memory/vaddr.c
+ LD /home/haoyue/ics2024/nemu/build/riscv32-nemu-interpreter
# -@git add /home/haoyue/ics2024/nemu/.. -A --ignore-errors
# -@while (test -e .git/index.lock); do sleep 0.1; done
# -@(echo "> "compile NEMU"" && echo 23241121 Haoyuehx && uname -a && uptime) | git commit -F - -q --author='tracer-ics2024 <[email protected]>' --no-verify --allow-empty
# -@sync
# -@git add /home/haoyue/ics2024/nemu/.. -A --ignore-errors
# -@while (test -e .git/index.lock); do sleep 0.1; done
# -@(echo "> "run NEMU"" && echo 23241121 Haoyuehx && uname -a && uptime) | git commit -F - -q --author='tracer-ics2024 <[email protected]>' --no-verify --allow-empty
# -@sync
/home/haoyue/ics2024/nemu/build/riscv32-nemu-interpreter --log=/home/haoyue/ics2024/nemu/build/nemu-log.txt
[src/utils/log.c:30 init_log] Log is written to /home/haoyue/ics2024/nemu/build/nemu-log.txt
[src/memory/paddr.c:50 init_mem] physical memory area [0x80000000, 0x87ffffff]
[src/monitor/monitor.c:51 load_img] No image is given. Use the default build-in image.
[src/monitor/monitor.c:28 welcome] Trace: ON
[src/monitor/monitor.c:31 welcome] If trace is enabled, a log file will be generated to record the trace. This may lead to a large log file. If it is not necessary, you can disable it in menuconfig
[src/monitor/monitor.c:32 welcome] Build time: 16:32:13, Feb 21 2025
Welcome to riscv32-NEMU!
For help, type "help"
[src/monitor/monitor.c:35 welcome] Exercise: Please remove me in the source code and compile NEMU again.
riscv32-nemu-interpreter: src/monitor/monitor.c:36: void welcome(): Assertion `0' failed.
make: *** [/home/haoyue/ics2024/nemu/scripts/native.mk:38: run] Aborted (core dumped)
注意到shell里面的这句话’Please remove me in the source code and compile NEMU again. riscv32-nemu-interpreter: src/monitor/monitor.c:36: void welcome(): Assertion `0’ failed.'
首先找到src/monitor/monitor.c将
static void welcome() {
Log("Trace: %s", MUXDEF(CONFIG_TRACE, ANSI_FMT("ON", ANSI_FG_GREEN), ANSI_FMT("OFF", ANSI_FG_RED)));
IFDEF(CONFIG_TRACE, Log("If trace is enabled, a log file will be generated "
"to record the trace. This may lead to a large log file. "
"If it is not necessary, you can disable it in menuconfig"));
Log("Build time: %s, %s", __TIME__, __DATE__);
printf("Welcome to %s-NEMU!\n", ANSI_FMT(str(__GUEST_ISA__), ANSI_FG_YELLOW ANSI_BG_RED));
printf("For help, type \"help\"\n");
# Log("Exercise: Please remove me in the source code and compile NEMU again.");
# assert(0);
}
后两行注释掉，nemu就可以正确运行。
问题2 在运行NEMU之后直接键入q退出, 你会发现终端输出了一些错误信息.
(nemu) q
make: *** [/home/haoyue/ics2024/nemu/scripts/native.mk:38: run] Error 1
使用lldb debug
haoyue@haoyue:~/ics2024/nemu$ lldb ./build/riscv32-nemu-interpreter
(lldb) target create "./build/riscv32-nemu-interpreter"
Current executable set to '/home/haoyue/ics2024/nemu/build/riscv32-nemu-interpreter' (x86_64).
首先找到键入q后调用的函数
static int cmd_q(char *args) {
return -1;
}
添加断点
(lldb) b cmd_q
Breakpoint 1: where = riscv32-nemu-interpreter`cmd_q at sdb.c:53:3, address = 0x00000000000039f0
运行,输入q,单步调试
(lldb) run
Process 119418 launched: '/home/haoyue/ics2024/nemu/build/riscv32-nemu-interpreter' (x86_64)
[src/utils/log.c:30 init_log] Log is written to stdout
[src/utils/log.c:30 init_log] Log is written to stdout
[src/memory/paddr.c:50 init_mem] physical memory area [0x80000000, 0x87ffffff]
[src/memory/paddr.c:50 init_mem] physical memory area [0x80000000, 0x87ffffff]
[src/monitor/monitor.c:51 load_img] No image is given. Use the default build-in image.
[src/monitor/monitor.c:51 load_img] No image is given. Use the default build-in image.
[src/monitor/monitor.c:28 welcome] Trace: ON
[src/monitor/monitor.c:28 welcome] Trace: ON
[src/monitor/monitor.c:31 welcome] If trace is enabled, a log file will be generated to record the trace. This may lead to a large log file. If it is not necessary, you can disable it in menuconfig
[src/monitor/monitor.c:31 welcome] If trace is enabled, a log file will be generated to record the trace. This may lead to a large log file. If it is not necessary, you can disable it in menuconfig
[src/monitor/monitor.c:32 welcome] Build time: 16:37:26, Feb 21 2025
[src/monitor/monitor.c:32 welcome] Build time: 16:37:26, Feb 21 2025
Welcome to riscv32-NEMU!
For help, type "help"
(nemu) q
Process 119418 stopped
* thread #1, name = 'riscv32-nemu-in', stop reason = breakpoint 1.1
frame #0: 0x00005555555579f0 riscv32-nemu-interpreter`cmd_q(args=<unavailable>) at sdb.c:53:3
50
51 static int cmd_q(char *args) {
52 // nemu_state.state = NEMU_QUIT;
-> 53 return -1;
54 }
55
56 static int cmd_help(char *args);
发现返回is_exit_status_bad()
(lldb) s
Process 119418 stopped
* thread #1, name = 'riscv32-nemu-in', stop reason = step in
frame #0: 0x000055555555635d riscv32-nemu-interpreter`main(argc=<unavailable>, argv=<unavailable>) at nemu-main.c:34:10
31 /* Start engine. */
32 engine_start();
33
-> 34 return is_exit_status_bad();
35 }
发现good值是1
(lldb) s
Process 119418 stopped
* thread #1, name = 'riscv32-nemu-in', stop reason = step in
frame #0: 0x000055555555821f riscv32-nemu-interpreter`is_exit_status_bad at state.c:23:3
20 int is_exit_status_bad() {
21 int good = (nemu_state.state == NEMU_END && nemu_state.halt_ret == 0) ||
22 (nemu_state.state == NEMU_QUIT);
-> 23 return !good;
24 }
(lldb) print good
(int) 1
应该修改cmd_q
static int cmd_q(char *args) {
nemu_state.state = NEMU_QUIT;
return -1;
}
补全代码
单步执行
| 命令 | 格式 | 使用举例 | 说明 |
|---|---|---|---|
| 单步执行 | si [N] |
si 10 |
让程序单步执行N条指令后暂停执行,当N没有给出时, 缺省为1 |
cmd_table添加命令
static struct {
const char *name;
const char *description;
int (*handler) (char *);
} cmd_table[] = {
{ "help", "Display information about all supported commands", cmd_help },
{ "c", "Continue the execution of the program", cmd_c },
{ "q", "Exit NEMU", cmd_q },
{ "si", "Step into n instructions", cmd_is },
/* TODO: Add more commands */
};
实现方法
static int cmd_is(char* args)
{
int n_inst = 1;
char extra;
if (args == NULL) {
cpu_exec(n_inst);
return 0;
}
if (sscanf(args, "%d%c", &n_inst, &extra) != 1) {
printf("error: invalid thread index '%s'.\n", args);
return 0;
}
if (n_inst == 0) {
printf("error: Thread index 0 is out of range (valid values are 0 - 1).\n");
return 0;
}
cpu_exec(n_inst);
return 0;
}
打印寄存器
| 命令 | 格式 | 使用举例 | 说明 |
|---|---|---|---|
| 打印程序状态 | info SUBCMD |
info r |
打印寄存器状态 |
cmd_table添加命令
static struct {
const char *name;
const char *description;
int (*handler) (char *);
} cmd_table[] = {
{ "help", "Display information about all supported commands", cmd_help },
{ "c", "Continue the execution of the program", cmd_c },
{ "q", "Exit NEMU", cmd_q },
{ "si", "Step into n instructions", cmd_is },
{ "info", "Print program status", cmd_info },
/* TODO: Add more commands */
};
实现方法，调用isa_reg_display()
static int cmd_info(char* args)
{
if (args == NULL) {
printf("info: missing argument.\n");
return 0;
}
else if (strcmp(args, "r") == 0) {
isa_reg_display();
return 0;
}
// else if (strcmp(args, "w") == 0) {
// return 0;
// }
else {
printf("Undefined info command: \"%s\".\n", args);
return 0;
}
return 0;
}
isa_reg_display()实现方法
void isa_reg_display()
{
for (int i = 0; i < REG_NUM; i++) {
word_t val = cpu.gpr[i];
printf("%-4s 0x%-16x %d\n", regs[i], val, val);
}
}
word_t isa_reg_str2val(const char *s, bool *success) {
for (int i = 0; i < REG_NUM; i++) {
if (strcmp(s, regs[i]) == 0) {
*success = true;
return cpu.gpr[i];
}
}
*success = false;
return 0;
}
扫描内存
| 命令 | 格式 | 使用举例 | 说明 |
|---|---|---|---|
| 扫描内存 | x N EXPR |
x 10 $esp |
求出表达式EXPR的值, 将结果作为起始内存 |
| 地址, 以十六进制形式输出连续的N个4字节 |
cmd_table添加命令
static struct {
const char* name;
const char* description;
int (*handler)(char*);
} cmd_table[] = {
{ "help", "Display information about all supported commands", cmd_help },
{ "c", "Continue the execution of the program", cmd_c },
{ "q", "Exit NEMU", cmd_q },
{ "si", "Step into n instructions", cmd_is },
{ "info", "Print program status", cmd_info },
{ "x", "Examine memory", cmd_x },
/* TODO: Add more commands */
};
实现方法，调用vaddr_read(vaddr_t addr, int len)
在sdb.h文件添加一行
word_t vaddr_read(vaddr_t addr, int len);
cmd_x(char* args)实现
static int cmd_x(char* args)
{
char* n_word = strtok(args, " ");
char* arg_expr = strtok(NULL, " ");
if (!n_word || !arg_expr) {
printf("Invalid arguments!\n");
return 0;
}
int len;
if (sscanf(n_word, "%d", &len) != 1) {
printf("error: first argument should be an integer, but got %s\n", n_word);
return 0;
}
word_t start_addr = 0;
if (sscanf(arg_expr, "%x", &start_addr) != 1) {
printf("error: require a hex expression, but got %s\n", arg_expr);
return 0;
}
if (start_addr < 0x80000000 || start_addr > 0x87ffffff) {
printf("Address 0x%x is out of bounds!\n", start_addr);
return 0;
}
for (int i = 0; i < len; i++) {
word_t current_addr = start_addr + i * 4;
word_t val = vaddr_read(current_addr, 4);
if (i == 0) {
printf("0x%x:", current_addr);
} else if (i % 4 == 0 && i != 0) {
printf("\n0x%x:", current_addr);
}
printf("\t0x%08x", val);
}
printf("\n");
return 0;
}
pa1.2
主要修改 /nemu/src/monitor/expr.c
添加cmd_p命令
首先，和前几个命令一样在sdb.c文件里添加static int cmd_p(char* args);
需要实现的功能：
- 检测输入是否正确
- 如果输入正确，计算表达式的值
static int cmd_p(char* args)
{
if (args == NULL) {
printf("p: missing argument.\n");
return 0;
}
bool success = true;
word_t result = expr(args, &success);
if (success) {
printf("%u\n", result);
} else {
printf("Invalid expression: %s\n", args);
}
return 0;
}
写完static int cmd_p(char* args)完善expr(args, &success)
正则表达式识别token
首先在enum里添加token类型
enum 枚举类型是一种可以由用户自定义数据集的数据类型。
枚举类型的每一个枚举值都对应一个整型数，默认情况下，第一个枚举值的值是0，然后依次增1，但也可以显示初始化任意一个枚举值对应的整形数，没定义的枚举值默认情况下在其前一个枚举值的对应整型数上加1.
enum {
TK_NOTYPE = 256,
TK_EQ, //257
/* TODO: Add more token types */
TK_HEX, // 十六进制整数
TK_UINT, // 十进制整数
TK_INT, // 负整数
};
在rules[]数组里添加新的正则表达对应
static struct rule {
const char* regex;
int token_type;
} rules[] = {
/* TODO: Add more rules.
* Pay attention to the precedence level of different rules.
*/
{ "0x[0-9AaBbCcDdEeFf]+", TK_HEX }, // 十六进制整数
{ "[0-9]+", TK_UINT }, // 十进制整数
{ "-[0-9]+", TK_INT }, // 负整数
{ " +", TK_NOTYPE }, // spaces
{ "\\+", '+' }, // plus
{ "==", TK_EQ }, // equal
{ "-", '-' }, // 减号
{ "\\*", '*' }, // 乘号
{ "/", '/' }, // 除号
{ "\\(", '(' }, // 左括号
{ "\\)", ')' }, // 右括号
};
最重要的部分:token识别
主要思路:
- 通过正则表达式进行分词,得到token的位置和长度
- 首先对token长度进行判断
- 通过正则表达式识别出的token_type进行分类存储
注意点:
- 每次存储完之后
nr_token自增 - 存储时
tokens[nr_token].str最后一位置为\0
static bool make_token(char* e)
{
int position = 0;
int i;
regmatch_t pmatch;
nr_token = 0;
while (e[position] != '\0') {
/* Try all rules one by one. */
for (i = 0; i < NR_REGEX; i++) {
if (regexec(&re[i], e + position, 1, &pmatch, 0) == 0 && pmatch.rm_so == 0) {
char* substr_start = e + position;
int substr_len = pmatch.rm_eo;
Log("match rules[%d] = \"%s\" at position %d with len %d: %.*s",
i, rules[i].regex, position, substr_len, substr_len, substr_start);
position += substr_len;
/* TODO: Now a new token is recognized with rules[i]. Add codes
* to record the token in the array `tokens'. For certain types
* of tokens, some extra actions should be performed.
*/
Assert(nr_token < 32, "too many tokens,token should less than 32 characters");
switch (rules[i].token_type) {
case TK_NOTYPE:
break;
case TK_HEX:
case TK_UINT:
Assert(substr_len < 32, "hex/uint token too long");
strncpy(tokens[nr_token].str, substr_start, substr_len);
tokens[nr_token].str[substr_len] = '\0';
tokens[nr_token].type = rules[i].token_type; // 设置类型
nr_token++;
break;
case TK_INT:
Assert(substr_len < 32, "int token too long");
strncpy(tokens[nr_token].str, substr_start, substr_len);
tokens[nr_token].str[substr_len] = '\0';
tokens[nr_token].type = rules[i].token_type; // 设置类型
nr_token++;
break;
case '+':
case '-':
case '*':
case '/':
case '(':
case ')':
strncpy(tokens[nr_token].str, substr_start, substr_len);
tokens[nr_token].str[substr_len] = '\0';
tokens[nr_token].type = rules[i].token_type; // 设置类型
nr_token++;
break;
default:
Assert(false, "unknow token type %d", rules[i].token_type);
}
break;
}
}
if (i == NR_REGEX) {
printf("no match at position %d\n%s\n%*.s^\n", position, e, position, "");
return false;
}
}
return true;
}
根据token求表达式的值
主要思路:递归
<expr> ::= <number> # 一个数是表达式
| "(" <expr> ")" # 在表达式两边加个括号也是表达式
| <expr> "+" <expr> # 两个表达式相加也是表达式
| <expr> "-" <expr> # 接下来你全懂了
| <expr> "*" <expr>
| <expr> "/" <expr>
根据分治法,将大的表达式化为小的表达式进行求值 代码框架:
eval(p, q) {
if (p > q) {
/* Bad expression */
}
else if (p == q) {
/* Single token.
* For now this token should be a number.
* Return the value of the number.
*/
}
else if (check_parentheses(p, q) == true) {
/* The expression is surrounded by a matched pair of parentheses.
* If that is the case, just throw away the parentheses.
*/
return eval(p + 1, q - 1);
}
else {
/* We should do more things here. */
}
}
在一个token表达式中寻找主运算符:
- 非运算符的token不是主运算符.
- 出现在一对括号中的token不是主运算符. 注意到这里不会出现有括号包围整个表达式的情况, 因为这种情况已经在check_parentheses()相应的if块中被处理了.
- 主运算符的优先级在表达式中是最低的. 这是因为主运算符是最后一步才进行的运算符.
- 当有多个运算符的优先级都是最低时, 根据结合性, 最后被结合的运算符才是主运算符. 一个例子是1 + 2 + 3, 它的主运算符应该是右边的+. 要找出主运算符, 只需要将token表达式全部扫描一遍, 就可以按照上述方法唯一确定主运算符. 代码框架更新
eval(p, q) {
if (p > q) {
/* Bad expression */
}
else if (p == q) {
/* Single token.
* For now this token should be a number.
* Return the value of the number.
*/
}
else if (check_parentheses(p, q) == true) {
/* The expression is surrounded by a matched pair of parentheses.
* If that is the case, just throw away the parentheses.
*/
return eval(p + 1, q - 1);
}
else {
op = the position of 主运算符 in the token expression;
val1 = eval(p, op - 1);
val2 = eval(op + 1, q);
switch (op_type) {
case '+': return val1 + val2;
case '-': /* ... */
case '*': /* ... */
case '/': /* ... */
default: assert(0);
}
}
}
代码实现
bool check_parentheses(int p, int q)
{
if (tokens[p].type != '(' || tokens[q].type != ')') {
return false;
}
int n_left = 0;
for (int i = p + 1; i <= q - 1; i++) {
if (tokens[i].type == '(') {
n_left++;
} else if (tokens[i].type == ')') {
n_left--;
if (n_left < 0) {
return false;
}
}
}
return n_left == 0;
}
int find_main_op(int p, int q)
{
int main_op = -1;
int main_op_priority = 3;
for (int i = p; i <= q; i++) {
int priority = 0;
switch (tokens[i].type) {
case '+':
case '-':
priority = 1;
break;
case '*':
case '/':
priority = 2;
break;
case '(':
while (tokens[i].type != ')') {
i++;
}
continue;
default:
continue;
}
if (priority <= main_op_priority) {
main_op_priority = priority;
main_op = i;
}
}
return main_op;
}
word_t eval_expr(int p, int q, bool* success)
{
if (p > q) {
*success = false;
return 0;
} else if (p == q) {
*success = true;
word_t result = 0;
switch (tokens[p].type) {
case TK_HEX:
sscanf(tokens[p].str, "%x", &result);
return result;
case TK_UINT:
sscanf(tokens[p].str, "%d", &result);
return result;
case TK_INT:
sscanf(tokens[p].str, "%d", &result);
return result;
default:
Assert(false, "error token type %d", tokens[p].type);
}
} else if (check_parentheses(p, q) == true) {
return eval_expr(p + 1, q - 1, success);
} else {
*success = true;
int op = find_main_op(p, q);
int val1 = eval_expr(p, op - 1, success);
int val2 = eval_expr(op + 1, q, success);
switch (tokens[op].type) {
case '+':
return val1 + val2;
case '-':
return val1 - val2;
case '*':
return val1 * val2;
case '/':
return val1 / val2;
default:
assert(0);
}
}
return 0;
}