vgalaxy@vgalaxy-VirtualBox:~/Templates/include$ ll
total 36
drwxrwxr-x 2 vgalaxy vgalaxy  4096  9月 30 11:05 ./
drwxr-xr-x 4 vgalaxy vgalaxy  4096  9月 30 11:03 ../
-rw-rw-r-- 1 vgalaxy vgalaxy    67  9月 30 11:05 a.c
-rw-rw-r-- 1 vgalaxy vgalaxy    13  9月 30 11:04 a.inc
-rwxrwxr-x 1 vgalaxy vgalaxy 16096  9月 30 11:05 a.out*
-rw-rw-r-- 1 vgalaxy vgalaxy    18  9月 30 11:05 b
vgalaxy@vgalaxy-VirtualBox:~/Templates/include$ cat a.c
#include<stdio.h>

int main(){
  printf(
    #include "a.inc"
      );
}
vgalaxy@vgalaxy-VirtualBox:~/Templates/include$ cat a.inc
#include "b"
vgalaxy@vgalaxy-VirtualBox:~/Templates/include$ cat b
"Hello, world!\n"
vgalaxy@vgalaxy-VirtualBox:~/Templates/include$ ./a.out
Hello, world!

#include <stdio.h>
#include "stdio.h"

#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc/x86_64-linux-gnu/10/include
 /usr/local/include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.

#include "..." search starts here:
#include <...> search starts here:
 .
 /usr/lib/gcc/x86_64-linux-gnu/10/include
 /usr/local/include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.

extern int printf (const char *__restrict __format, ...);

int main(){
    printf("Hello, world!\n");
}

#include<stdio.h>

int main(){
#if aa == bb
    printf("Yes\n");
#else
    printf("No\n");
#endif
}

# 3 "a.c"
int main(){

 printf("Yes\n");



}

#define A "aaaaaaaaaa"
#define TEN(x) x x x x x x x x x x
#define B TEN(A)
#define C TEN(B)
#define D TEN(C)
#define E TEN(D)
#define F TEN(E)
#define G TEN(F)


int main(){
    puts(G);
}

#define A sys ## tem

int main(){
    A("echo Hello\n");
}

#define NAMES(X) X(A) X(B) X(C) X(D)

int main(){
#define PRINT(x) puts("Hello, "#x"!");
    NAMES(PRINT);
}

vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat a.cc
extern "C" {
  int foo() { return 0; }
}

int bar() {
  return 0;
}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ g++ -c a.cc
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ls
a.cc  a.o
vgalaxy@vgalaxy-VirtualBox:~/Templates$ objdump -d a.o

a.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <foo>:
   0:  f3 0f 1e fa            endbr64
   4:  55                     push   %rbp
   5:  48 89 e5               mov    %rsp,%rbp
   8:  b8 00 00 00 00         mov    $0x0,%eax
   d:  5d                     pop    %rbp
   e:  c3                     ret

000000000000000f <_Z3barv>:
   f:  f3 0f 1e fa            endbr64
  13:  55                     push   %rbp
  14:  48 89 e5               mov    %rsp,%rbp
  17:  b8 00 00 00 00         mov    $0x0,%eax
  1c:  5d                     pop    %rbp
  1d:  c3                     ret

int main (int argc, char *argv[]) {
    int *p = (void *)1; // OK
    *p = 1; // Segmentation fault
}

#include <stdio.h>

void printptr(void *p) {
    printf("p = %p; *p = %016lx\n", p, *(long*)p);
}

int x;

int main(int argc, char *argv[]) {
    printptr(main); // 代码
    printptr(&main);
    printptr(&x); // 数据
    printptr(&argc); // 堆栈
    printptr(argv);
    printptr(&argv);
    printptr(argv[0]);
}

$ ./a.out
p = 0x562ea2e9017b; *p = e5894855fa1e0ff3
p = 0x562ea2e9017b; *p = e5894855fa1e0ff3
p = 0x562ea2e93014; *p = 0000000000000000
p = 0x7ffe9e89c20c; *p = 0000000000000001
p = 0x7ffe9e89c308; *p = 00007ffe9e89d2e8
p = 0x7ffe9e89c200; *p = 00007ffe9e89c308
p = 0x7ffe9e89d2e8; *p = 0074756f2e612f2e

#include<stdio.h>
#include<assert.h>

int main (int argc, char *argv[]) {
    int (*f)(int, char*[]) = main;
    if(argc!= 0) {
        char***a = &argv, *first = argv [0], ch = argv[0][0];
        printf("arg = \"%s\"; ch = '%c'\n", first, ch);
        assert(***a == ch);
        f(argc- 1, argv+ 1);
    }
}

$ ./a.out 1 2 3 hello
arg = "./a.out"; ch = '.'
arg = "1"; ch = '1'
arg = "2"; ch = '2'
arg = "3"; ch = '3'
arg = "hello"; ch = 'h'

$ wget https://www.ioccc.org/2011/hou/hou.c
$ gcc hou.c -lm -o hou

-nolibc

Do not use the C library or system libraries tightly coupled with it when linking.  Still link with the startup files, libgcc or toolchain provided language support libraries such as libgnat, libgfortran or libstdc++ unless options preventing their inclusion are used as well.  This typically removes -lc from the link command line, as well as system libraries that normally go with it and become meaningless when absence of a C library is assumed, for example -lpthread or -lm in some configurations.  This is intended for bare-board targets when there is indeed no C library available.

void (*signal (int sig, void (*func)(int)))(int);

SYNOPSIS
       #include <signal.h>

       typedef void (*sighandler_t)(int);

       sighandler_t signal(int signum, sighandler_t handler);

$ wget http://jyywiki.cn/pages/ICS/2020/demos/logisim.c
$ wget http://jyywiki.cn/pages/ICS/2020/demos/display.py

#include <stdio.h>
#include <unistd.h>

#define FORALL_REGS(_)  _(X) _(Y)
#define OUTPUTS(_)      _(A) _(B) _(C) _(D) _(E) _(F) _(G)
#define LOGIC           X1 = !X && Y; \
                        Y1 = !X && !Y; \
                        A  = (!X && !Y) || (X && !Y); \
                        B  = 1; \
                        C  = (!X && !Y) || (!X && Y); \
                        D  = (!X && !Y) || (X && !Y); \
                        E  = (!X && !Y) || (X && !Y); \
                        F  = (!X && !Y); \
                        G  = (X && !Y);

#define DEFINE(X)   static int X, X##1;
#define UPDATE(X)   X = X##1;
#define PRINT(X)    printf(#X " = %d; ", X);

int main() {
  FORALL_REGS(DEFINE);
  OUTPUTS(DEFINE);
  while (1) { // clock
    LOGIC;
    OUTPUTS(PRINT);
    putchar('\n');
    fflush(stdout);
    sleep(1);
    FORALL_REGS(UPDATE);
  }

$ ./a.out
A = 1; B = 1; C = 1; D = 1; E = 1; F = 1; G = 0;
A = 0; B = 1; C = 1; D = 0; E = 0; F = 0; G = 0;
A = 1; B = 1; C = 0; D = 1; E = 1; F = 0; G = 1;
A = 1; B = 1; C = 1; D = 1; E = 1; F = 1; G = 0;
A = 0; B = 1; C = 1; D = 0; E = 0; F = 0; G = 0;
A = 1; B = 1; C = 0; D = 1; E = 1; F = 0; G = 1;
A = 1; B = 1; C = 1; D = 1; E = 1; F = 1; G = 0;
A = 0; B = 1; C = 1; D = 0; E = 0; F = 0; G = 0;
A = 1; B = 1; C = 0; D = 1; E = 1; F = 0; G = 1;
A = 1; B = 1; C = 1; D = 1; E = 1; F = 1; G = 0;
A = 0; B = 1; C = 1; D = 0; E = 0; F = 0; G = 0;
A = 1; B = 1; C = 0; D = 1; E = 1; F = 0; G = 1;
A = 1; B = 1; C = 1; D = 1; E = 1; F = 1; G = 0;
^C

#!/usr/bin/env python3

import turtle
import fileinput

A, B, C, D, E, F, G = 0, 0, 0, 0, 0, 0, 0

turtle.setup(width=240, height=320)
turtle.pen(shown=False, pendown=False, pencolor='#aa0000', pensize=5)
turtle.tracer(0)

stdin = fileinput.input()
while True:
  turtle.clear()
  turtle.home()
  turtle.setpos(-20, 0)
  for i, draw in enumerate([G, C, D, E, F, A, B]):
    turtle.penup(); turtle.forward(5)
    turtle.pendown() if draw else turtle.penup()
    turtle.forward(40)
    turtle.penup(); turtle.forward(5)
    turtle.right(90)
    if i == 3: turtle.left(90)
  turtle.update()
  exec(stdin.readline())

$ sudo apt-get install python3-tk

$ ./a.out | ./display.py

#include<stdint.h>

#define NREG 4
#define NMEM 16

typedef uint8_t u8;

u8 pc = 0, R[NREG], M[NMEM] ={ ... };

enum
{ RA, R1, ..., PC };
u8 R[] =
{ [RA] = 0, [R1] = 0, ... [PC] = init_pc, };

#define pc (R[PC])
#define NREG (sizeof(R) / sizeof(u8))

// breaks when adding a register
#define NREG 5

// breaks when changing register size
#define NREG (sizeof(R) / sizeof(u8))

// never breaks
#define NREG (sizeof(R) / sizeof(R[0])) // 但需要R的定义

// even better (why?)
enum { RA, ... , PC, NREG }

#include <assert.h>
#include <stdio.h>
#include "yemu.h"

typedef union inst {
  struct { u8 rs  : 2, rt: 2, op: 4; } rtype;
  struct { u8 addr: 4,        op: 4; } mtype;
} inst_t;

#define RTYPE(i) u8 rt = (i)->rtype.rt, rs = (i)->rtype.rs;
#define MTYPE(i) u8 addr = (i)->mtype.addr;

void idex() {
  inst_t *cur = (inst_t *)&M[pc];
  switch (cur->rtype.op) {
    case 0b0000: { RTYPE(cur); R[rt]   = R[rs];   pc++; break; }
    case 0b0001: { RTYPE(cur); R[rt]  += R[rs];   pc++; break; }
    case 0b1110: { MTYPE(cur); R[RA]   = M[addr]; pc++; break; }
    case 0b1111: { MTYPE(cur); M[addr] = R[RA];   pc++; break; }
    default: assert(0);
  }
}

.PHONY: run clean test

CFLAGS = -Wall -Werror -std=c11 -O2
CC = gcc
LD = gcc

yemu: yemu.o idex.o
    $(LD) $(LDFLAGS) -o yemu yemu.o idex.o

yemu.o: yemu.c yemu.h
    $(CC) $(CFLAGS) -c -o yemu.o yemu.c

idex.o: idex.c yemu.h
    $(CC) $(CFLAGS) -c -o idex.o idex.c

run: yemu
    @./yemu

clean:
    rm -f test yemu *.o

test: yemu
    $(CC) $(CFLAGS) -o test idex.o test.c && ./test

$ gcc -E test.c | indent - | vim -

$ rm -rf

$ rm -- -rf

*.*
*
!*/
!/nemu/*
!/nexus-am/*
!/nanos-lite/*
!/navy-apps/*
!Makefile
!README.md
!.gitignore
!init.sh
/fceux-am
/am-kernels

*.*
*
!*/
!Makefile
!*.mk
!*.[cSh]
!.gitignore
!README.md
!Kconfig
include/config
include/generated

include nemu/scripts/git.mk

default:
    @echo "Please run 'make' under any subprojects to compile."

submit:
    git gc
    STUID=$(STUID) STUNAME=$(STUNAME) bash -c "$$(curl -s http://jyywiki.cn/static/submit.sh)"

.PHONY: default submit

COURSE=ICS2021
MODULE=$(git rev-parse --abbrev-ref HEAD | tr '[a-z]' '[A-Z]')
FILE=/tmp/upload.tar.bz2
tar caf "$FILE" ".git" $(find . -maxdepth 2 -name "*.pdf") && \
  curl -F "token=$TOKEN" \
       -F "stuid=$STUID" \
       -F "stuname=$STUNAME" \
       -F "course=$COURSE" \
       -F "module=$MODULE" \
       -F "file=@$FILE" \
       http://jyywiki.cn/upload

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ git branch
  master
  pa0
  pa1
* pa2
vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ git rev-parse --abbrev-ref HEAD
pa2

STUID = XXX
STUNAME = XXX

# DO NOT modify the following code!!!

GITFLAGS = -q --author='tracer-ics2021 <tracer@njuics.org>' --no-verify --allow-empty

# prototype: git_commit(msg)
define git_commit
    -@git add $(NEMU_HOME)/.. -A --ignore-errors
    -@while (test -e .git/index.lock); do sleep 0.1; done
    -@(echo "> $(1)" && echo $(STUID) && hostnamectl && uptime) | git commit -F - $(GITFLAGS)
    -@sync
endef

vgalaxy@vgalaxy-VirtualBox:~$ hostnamectl
   Static hostname: vgalaxy-VirtualBox
         Icon name: computer-vm
           Chassis: vm
        Machine ID: beeabc33a4e84c64ba86a73bb19c624a
           Boot ID: 293d87d068e74a8ea858bbff7c29835d
    Virtualization: oracle
  Operating System: Ubuntu 21.04
            Kernel: Linux 5.11.0-16-generic
      Architecture: x86-64
vgalaxy@vgalaxy-VirtualBox:~$ uptime
 20:12:26 up 11:08,  1 user,  load average: 0.62, 0.59, 0.44

.PHONY: run clean test

CFLAGS = -Wall -Werror -std=c11 -O2
CC = gcc
LD = gcc

yemu: yemu.o idex.o
    $(LD) $(LDFLAGS) -o yemu yemu.o idex.o

yemu.o: yemu.c yemu.h
    $(CC) $(CFLAGS) -c -o yemu.o yemu.c

idex.o: idex.c yemu.h
    $(CC) $(CFLAGS) -c -o idex.o idex.c

run: yemu
    @./yemu

clean:
    rm -f test yemu *.o

test: yemu
    $(CC) $(CFLAGS) -o test idex.o test.c && ./test

NAME := $(shell basename $(PWD))
all: $(NAME)-64 $(NAME)-32
export MODULE := Lab1
export STUID = XXX
export STUNAME = XXX
include ../Makefile

vgalaxy@vgalaxy-VirtualBox:~/ics-workbench/multimod$ basename $PWD
multimod

ifeq ($(NAME),)
$(error Should make in each lab's directory)
endif

SRCS   := $(shell find . -maxdepth 1 -name "*.c")
DEPS   := $(shell find . -maxdepth 1 -name "*.h") $(SRCS)
CFLAGS += -O1 -std=gnu11 -ggdb -Wall -Werror -Wno-unused-result -Wno-unused-value -Wno-unused-variable

.PHONY: all git test clean commit-and-make

.DEFAULT_GOAL := commit-and-make
commit-and-make: git all

$(NAME)-64: $(DEPS) # 64bit binary
    gcc -m64 $(CFLAGS) $(SRCS) -o $@ $(LDFLAGS)

$(NAME)-32: $(DEPS) # 32bit binary
    gcc -m32 $(CFLAGS) $(SRCS) -o $@ $(LDFLAGS)

$(NAME)-64.so: $(DEPS) # 64bit shared library
    gcc -fPIC -shared -m64 $(CFLAGS) $(SRCS) -o $@ $(LDFLAGS)

$(NAME)-32.so: $(DEPS) # 32bit shared library
    gcc -fPIC -shared -m32 $(CFLAGS) $(SRCS) -o $@ $(LDFLAGS)

clean:
    rm -f $(NAME)-64 $(NAME)-32 $(NAME)-64.so $(NAME)-32.so

include ../Makefile.lab

# **DO NOT MODIFY**

export COURSE := ICS2021
URL := 'http://jyywiki.cn/static/submit-icslab.sh'

submit:
    @cd $(dir $(abspath $(lastword $(MAKEFILE_LIST)))) && \
      curl -sSL '$(URL)' | bash

git:
    @git add $(shell find . -name "*.c") $(shell find . -name "*.h") -A --ignore-errors
    @while (test -e .git/index.lock); do sleep 0.1; done
    @(hostnamectl && uptime) | git commit -F - -q --author='tracer-nju <tracer@nju.edu.cn>' --no-verify --allow-empty
    @sync

vgalaxy@vgalaxy-VirtualBox:~/ics-workbench/multimod$ make -nB
git add ./main.c ./multimod.c  -A --ignore-errors
while (test -e .git/index.lock); do sleep 0.1; done
(hostnamectl && uptime) | git commit -F - -q --author='tracer-nju <tracer@nju.edu.cn>' --no-verify --allow-empty
sync
gcc -m64 -O1 -std=gnu11 -ggdb -Wall -Werror -Wno-unused-result -Wno-unused-value -Wno-unused-variable ./main.c ./multimod.c -o multimod-64
gcc -m32 -O1 -std=gnu11 -ggdb -Wall -Werror -Wno-unused-result -Wno-unused-value -Wno-unused-variable ./main.c ./multimod.c -o multimod-32

include nemu/scripts/git.mk

default:
    @echo "Please run 'make' under any subprojects to compile."

submit:
    git gc
    STUID=$(STUID) STUNAME=$(STUNAME) bash -c "$$(curl -s http://jyywiki.cn/static/submit.sh)"

.PHONY: default submit

# Include variables and rules generated by menuconfig
-include $(NEMU_HOME)/include/config/auto.conf
-include $(NEMU_HOME)/include/config/auto.conf.cmd

...

# Include rules for menuconfig
include $(NEMU_HOME)/scripts/config.mk

...

# Include rules to build NEMU
include $(NEMU_HOME)/scripts/native.mk

include $(NEMU_HOME)/scripts/git.mk
include $(NEMU_HOME)/scripts/build.mk

include $(NEMU_HOME)/tools/difftest.mk

compile_git:
    $(call git_commit, "compile")
$(BINARY): compile_git

# Some convenient rules

override ARGS ?= --log=$(BUILD_DIR)/nemu-log.txt
override ARGS += $(ARGS_DIFF)

# Command to execute NEMU
IMG ?=
NEMU_EXEC := $(BINARY) $(ARGS) $(IMG)

run-env: $(BINARY) $(DIFF_REF_SO)

run: run-env
    $(call git_commit, "run")
    $(NEMU_EXEC)

gdb: run-env
    $(call git_commit, "gdb")
    gdb -s $(BINARY) --args $(NEMU_EXEC)

clean-tools = $(dir $(shell find ./tools -name "Makefile"))
$(clean-tools):
    -@$(MAKE) -s -C $@ clean
clean-tools: $(clean-tools)
clean-all: clean distclean clean-tools

.PHONY: run gdb run-env clean-tools clean-all $(clean-tools)

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ grep -nr git_commit
scripts/git.mk:8:# prototype: git_commit(msg)
scripts/git.mk:9:define git_commit
scripts/native.mk:7:  $(call git_commit, "compile")
scripts/native.mk:22:  $(call git_commit, "run")
scripts/native.mk:26:  $(call git_commit, "gdb")

NEMU_EXEC := $(BINARY) $(ARGS) $(IMG)

BINARY   = $(BUILD_DIR)/$(NAME)$(SO)

remove_quote = $(patsubst "%",%,$(1))

# Extract variabls from menuconfig
GUEST_ISA ?= $(call remove_quote,$(CONFIG_ISA))
ENGINE ?= $(call remove_quote,$(CONFIG_ENGINE))
NAME    = $(GUEST_ISA)-nemu-$(ENGINE)

CONFIG_ISA="riscv32"
...
CONFIG_ENGINE="interpreter"

.PHONY: app clean

app: $(BINARY)

$(BINARY): $(OBJS) $(ARCHIVES)
    @echo + LD $@
    @$(LD) -o $@ $(OBJS) $(LDFLAGS) $(ARCHIVES) $(LIBS)

clean:
    -rm -rf $(BUILD_DIR)

OBJS = $(SRCS:%.c=$(OBJ_DIR)/%.o) $(CXXSRC:%.cc=$(OBJ_DIR)/%.o)

# Compilation patterns
$(OBJ_DIR)/%.o: %.c
    @echo + CC $<
    @mkdir -p $(dir $@)
    @$(CC) $(CFLAGS) -c -o $@ $<
    $(call call_fixdep, $(@:.o=.d), $@)

$(OBJ_DIR)/%.o: %.cc
    @echo + CXX $<
    @mkdir -p $(dir $@)
    @$(CXX) $(CFLAGS) $(CXXFLAGS) -c -o $@ $<
    $(call call_fixdep, $(@:.o=.d), $@)

make -nB | grep -ve '^\(\#\|echo\|mkdir\)' | vim -

:g/fixdep/d
:g/mv/d

gcc -O2 -MMD -Wall -Werror -I/home/vgalaxy/ics2021/nemu/include -I/home/vgalaxy/ics2021/nemu/src/engine/interpreter -I/home/vgalaxy/ics2021/nemu/src/isa/riscv32/include -O2  -ggdb3  -DITRACE_COND=true -D__GUEST_ISA__=riscv32 -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/nemu-main.o src/nemu-main.c

gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/nemu-main.o src/nemu-main.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/cpu/difftest/dut.o src/cpu/difftest/dut.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/cpu/cpu-exec.o src/cpu/cpu-exec.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/monitor/monitor.o src/monitor/monitor.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/monitor/sdb/watchpoint.o src/monitor/sdb/watchpoint.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/monitor/sdb/expr.o src/monitor/sdb/expr.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/monitor/sdb/sdb.o src/monitor/sdb/sdb.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/log.o src/utils/log.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/timer.o src/utils/timer.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/state.o src/utils/state.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/rand.o src/utils/rand.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/memory/paddr.o src/memory/paddr.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/memory/vaddr.o src/memory/vaddr.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/device/io/port-io.o src/device/io/port-io.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/device/io/map.o src/device/io/map.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/device/io/mmio.o src/device/io/mmio.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/engine/interpreter/hostcall.o src/engine/interpreter/hostcall.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/engine/interpreter/init.o src/engine/interpreter/init.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/system/intr.o src/isa/riscv32/system/intr.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/system/mmu.o src/isa/riscv32/system/mmu.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/reg.o src/isa/riscv32/reg.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/difftest/dut.o src/isa/riscv32/difftest/dut.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/instr/decode.o src/isa/riscv32/instr/decode.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/logo.o src/isa/riscv32/logo.c
gcc -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/init.o src/isa/riscv32/init.c
g++ -O2 -MMD -Wall -Werror -I/home/vgalaxy/ics2021/nemu/include -I/home/vgalaxy/ics2021/nemu/src/engine/interpreter -I/home/vgalaxy/ics2021/nemu/src/isa/riscv32/include -O2  -ggdb3  -DITRACE_COND=true -D__GUEST_ISA__=riscv32 -I/usr/lib/llvm-11/include -std=c++14   -fno-exceptions -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -fPIE -c -o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/disasm.o src/utils/disasm.cc
git add /home/vgalaxy/ics2021/nemu/.. -A --ignore-errors
while (test -e .git/index.lock); do sleep 0.1; done
(echo ">  "compile"" && echo 201250012 && hostnamectl && uptime) | git commit -F - -q --author='tracer-ics2021 <tracer@njuics.org>' --no-verify --allow-empty
sync

g++ -o /home/vgalaxy/ics2021/nemu/build/riscv32-nemu-interpreter /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/nemu-main.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/cpu/difftest/dut.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/cpu/cpu-exec.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/monitor/monitor.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/monitor/sdb/watchpoint.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/monitor/sdb/expr.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/monitor/sdb/sdb.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/log.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/timer.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/state.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/rand.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/memory/paddr.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/memory/vaddr.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/device/io/port-io.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/device/io/map.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/device/io/mmio.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/engine/interpreter/hostcall.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/engine/interpreter/init.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/system/intr.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/system/mmu.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/reg.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/difftest/dut.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/instr/decode.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/logo.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/isa/riscv32/init.o /home/vgalaxy/ics2021/nemu/build/obj-riscv32-nemu-interpreter/src/utils/disasm.o -O2 -O2  -ggdb3   -lreadline -ldl -pie -lLLVM-11

### *Get a more readable version of this Makefile* by `make html` (requires python-markdown)
html:
    cat Makefile | sed 's/^\([^#]\)/    \1/g' | markdown_py > Makefile.html
.PHONY: html

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ find . -name "*.c" -o -name "*.h" | xargs cat | wc -l
23415
vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ cd tools/
vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu/tools$ find . -name "*.c" -o -name "*.h" | xargs cat | wc -l
18927

$ grep -n main $(find . -name "*.c")
$ find . | xargs grep --color -nse '\<main\>'

:vimgrep /\<main\>/ **/*.c

int main(int argc, char *argv[]) {
  init_monitor(argc, argv);
  engine_start();
  return is_exit_status_bad();
}

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ make run
+ LD /home/vgalaxy/ics2021/nemu/build/riscv32-nemu-interpreter
/home/vgalaxy/ics2021/nemu/build/riscv32-nemu-interpreter --log=/home/vgalaxy/ics2021/nemu/build/nemu-log.txt
[src/utils/log.c:13 init_log] Log is written to /home/vgalaxy/ics2021/nemu/build/nemu-log.txt
[src/memory/paddr.c:36 init_mem] physical memory area [0x80000000, 0x88000000]
[src/monitor/monitor.c:34 load_img] No image is given. Use the default build-in image.
[src/monitor/monitor.c:13 welcome] Trace: ON
[src/monitor/monitor.c:14 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:17 welcome] Build time: 17:23:04, Oct  2 2021
Welcome to riscv32-NEMU!
For help, type "help"
(nemu)

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ ./build/riscv32-nemu-interpreter --help
Usage: ./build/riscv32-nemu-interpreter [OPTION...] IMAGE [args]

  -b,--batch              run with batch mode
  -l,--log=FILE           output log to FILE
  -d,--diff=REF_SO        run DiffTest with reference REF_SO
  -p,--port=PORT          run DiffTest with port PORT

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ ./build/riscv32-nemu-interpreter -b --log=/home/vgalaxy/ics2021/nemu/build/nemu-log.txt
[src/utils/log.c:13 init_log] Log is written to /home/vgalaxy/ics2021/nemu/build/nemu-log.txt
[src/memory/paddr.c:36 init_mem] physical memory area [0x80000000, 0x88000000]
[src/monitor/monitor.c:34 load_img] No image is given. Use the default build-in image.
[src/monitor/monitor.c:13 welcome] Trace: ON
[src/monitor/monitor.c:14 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:17 welcome] Build time: 17:23:04, Oct  2 2021
Welcome to riscv32-NEMU!
For help, type "help"
[src/cpu/cpu-exec.c:122 cpu_exec] nemu: HIT GOOD TRAP at pc = 0x8000000c
[src/cpu/cpu-exec.c:55 statistic] host time spent = 18 us
[src/cpu/cpu-exec.c:56 statistic] total guest instructions = 4
[src/cpu/cpu-exec.c:57 statistic] simulation frequency = 222,222 instr/s

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ cat input
si
q
vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ ./build/riscv32-nemu-interpreter --log=/home/vgalaxy/ics2021/nemu/build/nemu-log.txt < input
[src/utils/log.c:13 init_log] Log is written to /home/vgalaxy/ics2021/nemu/build/nemu-log.txt
[src/memory/paddr.c:36 init_mem] physical memory area [0x80000000, 0x88000000]
[src/monitor/monitor.c:34 load_img] No image is given. Use the default build-in image.
[src/monitor/monitor.c:13 welcome] Trace: ON
[src/monitor/monitor.c:14 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:17 welcome] Build time: 17:23:04, Oct  2 2021
Welcome to riscv32-NEMU!
For help, type "help"
(nemu) si
0x80000000: b7 02 00 80 lui  t0, 524288
(nemu) q

test: run-env
    $(NEMU_EXEC) < input

vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat a.c
#include "a.h"

void foo(){
  f();
}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat b.c
#include "a.h"

void bar(){
  f();
}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat main.c
int main(){
  return 0;
}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat a.h
int f() {return 0;}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ gcc a.c b.c main.c
/usr/bin/ld: /tmp/ccjWoe4C.o: in function `f':
b.c:(.text+0x0): multiple definition of `f'; /tmp/ccpMMypI.o:a.c:(.text+0x0): first defined here
collect2: error: ld returned 1 exit status

0000000000001129 <f>:
    1129:  f3 0f 1e fa            endbr64
    112d:  55                     push   %rbp
    112e:  48 89 e5               mov    %rsp,%rbp
    1131:  b8 00 00 00 00         mov    $0x0,%eax
    1136:  5d                     pop    %rbp
    1137:  c3                     ret

0000000000001138 <foo>:
    1138:  f3 0f 1e fa            endbr64
    113c:  55                     push   %rbp
    113d:  48 89 e5               mov    %rsp,%rbp
    1140:  b8 00 00 00 00         mov    $0x0,%eax
    1145:  e8 df ff ff ff         call   1129 <f>
    114a:  90                     nop
    114b:  5d                     pop    %rbp
    114c:  c3                     ret

000000000000114d <f>:
    114d:  f3 0f 1e fa            endbr64
    1151:  55                     push   %rbp
    1152:  48 89 e5               mov    %rsp,%rbp
    1155:  b8 00 00 00 00         mov    $0x0,%eax
    115a:  5d                     pop    %rbp
    115b:  c3                     ret

000000000000115c <bar>:
    115c:  f3 0f 1e fa            endbr64
    1160:  55                     push   %rbp
    1161:  48 89 e5               mov    %rsp,%rbp
    1164:  b8 00 00 00 00         mov    $0x0,%eax
    1169:  e8 df ff ff ff         call   114d <f>
    116e:  90                     nop
    116f:  5d                     pop    %rbp
    1170:  c3                     ret

vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat x.c
#include "a.h"
vgalaxy@vgalaxy-VirtualBox:~/Templates$ gcc -Wall -Werror a.c b.c x.c main.c
In file included from x.c:1:
a.h:1:12: error: ‘f’ defined but not used [-Werror=unused-function]
    1 | static int f() {return 0;}
      |            ^
cc1: all warnings being treated as errors

0000000000001129 <f>:
    1129:  55                     push   %rbp
    112a:  48 89 e5               mov    %rsp,%rbp
    112d:  b8 00 00 00 00         mov    $0x0,%eax
    1132:  5d                     pop    %rbp
    1133:  c3                     ret

0000000000001134 <foo>:
    1134:  f3 0f 1e fa            endbr64
    1138:  55                     push   %rbp
    1139:  48 89 e5               mov    %rsp,%rbp
    113c:  b8 00 00 00 00         mov    $0x0,%eax
    1141:  e8 e3 ff ff ff         call   1129 <f>
    1146:  90                     nop
    1147:  5d                     pop    %rbp
    1148:  c3                     ret

0000000000001149 <f>:
    1149:  55                     push   %rbp
    114a:  48 89 e5               mov    %rsp,%rbp
    114d:  b8 00 00 00 00         mov    $0x0,%eax
    1152:  5d                     pop    %rbp
    1153:  c3                     ret

0000000000001154 <bar>:
    1154:  f3 0f 1e fa            endbr64
    1158:  55                     push   %rbp
    1159:  48 89 e5               mov    %rsp,%rbp
    115c:  b8 00 00 00 00         mov    $0x0,%eax
    1161:  e8 e3 ff ff ff         call   1149 <f>
    1166:  90                     nop
    1167:  5d                     pop    %rbp
    1168:  c3                     ret

#define assert(cond) if (!(cond)) panic(...);

if (...) assert(0);
else ...

#define assert(cond) \
  do { \
    if (!(cond)) { \
      fprintf(stderr, "Fail @ %s:%d", __FILE__, __LINE__); \
      exit(1); \
    } \
  } while (0)

#define assert(cond) ({ ... })

static void welcome() {
  Log("Trace: %s", MUXDEF(CONFIG_TRACE, ASNI_FMT("ON", ASNI_FG_GREEN), ASNI_FMT("OFF", ASNI_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", ASNI_FMT(str(__GUEST_ISA__), ASNI_FG_YELLOW ASNI_BG_RED));
  printf("For help, type \"help\"\n");
}

#define ASNI_FG_BLACK   "\33[1;30m"
#define ASNI_FG_RED     "\33[1;31m"
#define ASNI_FG_GREEN   "\33[1;32m"
#define ASNI_FG_YELLOW  "\33[1;33m"
#define ASNI_FG_BLUE    "\33[1;34m"
#define ASNI_FG_MAGENTA "\33[1;35m"
#define ASNI_FG_CYAN    "\33[1;36m"
#define ASNI_FG_WHITE   "\33[1;37m"
#define ASNI_BG_BLACK   "\33[1;40m"
#define ASNI_BG_RED     "\33[1;41m"
#define ASNI_BG_GREEN   "\33[1;42m"
#define ASNI_BG_YELLOW  "\33[1;43m"
#define ASNI_BG_BLUE    "\33[1;44m"
#define ASNI_BG_MAGENTA "\33[1;35m"
#define ASNI_BG_CYAN    "\33[1;46m"
#define ASNI_BG_WHITE   "\33[1;47m"
#define ASNI_NONE       "\33[0m"

#define ASNI_FMT(str, fmt) fmt str ASNI_NONE

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ ./build/riscv32-nemu-interpreter --log=/home/vgalaxy/ics2021/nemu/build/nemu-log.txt | less

ESC[1;34m[src/utils/log.c:13 init_log] Log is written to /home/vgalaxy/ics2021/nemu/build/nemu-log.txtESC[0m
ESC[1;34m[src/memory/paddr.c:36 init_mem] physical memory area [0x80000000, 0x88000000]ESC[0m
ESC[1;34m[src/monitor/monitor.c:34 load_img] No image is given. Use the default build-in image.ESC[0m
ESC[1;34m[src/monitor/monitor.c:13 welcome] Trace: ESC[1;32mONESC[0mESC[0m
ESC[1;34m[src/monitor/monitor.c:14 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 menuconfigESC[0m
ESC[1;34m[src/monitor/monitor.c:17 welcome] Build time: 17:23:04, Oct  2 2021ESC[0m
Welcome to ESC[1;33mESC[1;41mriscv32ESC[0m-NEMU!
For help, type "help"

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ ls | less

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ ls --color | less

ESC[0mESC[01;34mbuildESC[0m
ESC[01;34mconfigsESC[0m
ESC[01;34mincludeESC[0m
input
Kconfig
Makefile
README.md
ESC[01;34mresourceESC[0m
ESC[01;34mscriptsESC[0m
ESC[01;34msrcESC[0m
tags
ESC[01;34mtoolsESC[0m

vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ echo -e "\033[34m HAHA \033[0m"
 HAHA
vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ echo -e "\033[43;34m HAHA \033[0m"
 HAHA
vgalaxy@vgalaxy-VirtualBox:~/ics2021/nemu$ echo -e "\033[44;37m HAHA \033[0m"
 HAHA

vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat demo.c
void bar(){
  *((int *)0)=0;
}

void foo(){
  bar();
}

int main(){
  foo();
}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ gcc -g demo.c
vgalaxy@vgalaxy-VirtualBox:~/Templates$ gdb ./a.out

Reading symbols from ./a.out...
(gdb) run
Starting program: /home/vgalaxy/Templates/a.out

Program received signal SIGSEGV, Segmentation fault.
bar () at demo.c:2
2    *((int *)0)=0;
(gdb) bt
#0  bar () at demo.c:2
#1  0x0000555555555151 in foo () at demo.c:6
#2  0x0000555555555166 in main () at demo.c:10

# Compilation patterns
$(OBJ_DIR)/%.o: %.c
    @echo + CC $<
    @mkdir -p $(dir $@)
    @$(CC) $(CFLAGS) -c -o $@ $<
    @$(CC) $(CFLAGS) -E -MF /dev/null $< | \
        grep -ve '^#' | \
        clang-format - > $(basename $@).i
    $(call call_fixdep, $(@:.o=.d), $@)

int bitset_size1(uint32_t S) { // SIMD
  S = (S & 0x55555555) + ((S >> 1) & 0x55555555);
  S = (S & 0x33333333) + ((S >> 2) & 0x33333333);
  S = (S & 0x0F0F0F0F) + ((S >> 4) & 0x0F0F0F0F);
  S = (S & 0x00FF00FF) + ((S >> 8) & 0x00FF00FF);
  S = (S & 0x0000FFFF) + ((S >> 16) & 0x0000FFFF);
  return S;
}

lowbit(x) = x & -x

int clz(uint32_t x) {
    int n = 0;
    if (x <= 0x0000ffff) n += 16, x <<= 16;
    if (x <= 0x00ffffff) n +=  8, x <<= 8;
    if (x <= 0x0fffffff) n +=  4, x <<= 4;
    if (x <= 0x3fffffff) n +=  2, x <<= 2;
    if (x <= 0x7fffffff) n ++;
    return n;
}

void LOG(int i) {
    int res = clz(i);
    printf("%d %d\n", i, 31 - res);
}

vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat log2.c
#include <stdio.h>
#include <stdint.h>
#include "log2.inc"

int main() {
  for (int i = 0; i < 64; i++) {
    uint64_t x = 1ULL << i;
    printf("%016lx %d\n", x, LOG2(x));
  }
}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat log2.inc
#define LOG2(x) ("-01W2?XG3<@kYCHf4-=:AnlLZNDcI\\g_5P-V>F;jBeo9mKMb[^OUEid8Ja]Th7`S6RQ"[(x) % 67] - '0')

#!/usr/bin/python3

import json

n, base = 64, '0'
for m in range(n, 10000):
  if len({ (2**i) % m for i in range(n) }) == n:
    M = { j: chr(ord(base) + i)
      for j in range(0, m)
        for i in range(0, n)
          if (2**i) % m == j }
    break

magic = json.dumps(''.join(
  [ M.get(j, '-') for j in range(0, m) ]
  )).strip('"')

print(f'#define LOG2(x) ("{magic}"[(x) % {m}] - \'{base}\')')

vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat sum_float.c
#define SUM(T, st, ed, d) ({ \
  T s = 0; \
  for (int i = st; i != ed + d; i += d) \
    s += (T)1 / i; \
  s; \
})

#include <stdio.h>
#define N 1000000

int main() {
  printf("%.16f\n", SUM(float, 1, N, 1));
  printf("%.16f\n", SUM(float, N, 1, -1));
  printf("%.16lf\n", SUM(double, 1, N, 1));
  printf("%.16lf\n", SUM(double, N, 1, -1));
}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
14.3573579788208008
14.3926515579223633
14.3927267228649889
14.3927267228657723

float Q_rsqrt( float number ) {
  union { float f; uint32_t i; } conv;
  float x2 = number * 0.5F;
  conv.f = number;
  conv.i = 0x5f3759df - ( conv.i >> 1 ); // ???
  conv.f = conv.f * ( 1.5F - ( x2 * conv.f * conv.f ) );
  return conv.f;
}

int64_t multimod_fast(int64_t a, int64_t b, int64_t m) {
  int64_t x = (int64_t)((double)a * b / m) * m;
  int64_t t = (a * b - x) % m;
  return t < 0 ? t + m : t;
}

vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat a.c
int f(int a, int b) {
  return a + b;
}
vgalaxy@vgalaxy-VirtualBox:~/Templates$ gcc -c -m32 -O2 -fno-pic a.c
vgalaxy@vgalaxy-VirtualBox:~/Templates$ objdump -d a.o

a.o:     file format elf32-i386


Disassembly of section .text:

00000000 <f>:
   0:  f3 0f 1e fb            endbr32
   4:  8b 44 24 08            mov    0x8(%esp),%eax
   8:  03 44 24 04            add    0x4(%esp),%eax
   c:  c3                     ret
vgalaxy@vgalaxy-VirtualBox:~/Templates$ gcc -c -m64 -O2 a.c
vgalaxy@vgalaxy-VirtualBox:~/Templates$ objdump -d a.o

a.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <f>:
   0:  f3 0f 1e fa            endbr64
   4:  8d 04 37               lea    (%rdi,%rsi,1),%eax
   7:  c3                     ret

void plus(int a, int b) {
  fprintf(stdout, "%d + %d = %d\n", a, b, a + b);
}

0000000000001170 <plus>:
    1170:  f3 0f 1e fa            endbr64
    1174:  44 8d 0c 37            lea    (%rdi,%rsi,1),%r9d
    1178:  89 f9                  mov    %edi,%ecx
    117a:  48 8b 3d 8f 2e 00 00   mov    0x2e8f(%rip),%rdi        # 4010 <stdout@@GLIBC_2.2.5>
    1181:  41 89 f0               mov    %esi,%r8d
    1184:  48 8d 15 79 0e 00 00   lea    0xe79(%rip),%rdx        # 2004 <_IO_stdin_used+0x4>
    118b:  be 01 00 00 00         mov    $0x1,%esi
    1190:  31 c0                  xor    %eax,%eax
    1192:  e9 b9 fe ff ff         jmp    1050 <__fprintf_chk@plt>
    1197:  66 0f 1f 84 00 00 00   nopw   0x0(%rax,%rax,1)
    119e:  00 00

int foo(int x, int y) {
  x++; y++;
  asm ("endbr64;"
       ".byte 0xf3, 0x0f, 0x1e, 0xfa"
  );
  return x + y;
}

    endbr64
#APP
# 3 "a.c" 1
    endbr64;.byte 0xf3, 0x0f, 0x1e, 0xfa
# 0 "" 2
#NO_APP
    leal    2(%rdi,%rsi), %eax
    ret

0000000000000000 <foo>:
   0:  f3 0f 1e fa            endbr64
   4:  f3 0f 1e fa            endbr64
   8:  f3 0f 1e fa            endbr64
   c:  8d 44 37 02            lea    0x2(%rdi,%rsi,1),%eax
  10:  c3                     ret

int foo(int x, int y) {
  int z;
  x++; y++;
  asm (
    "addl %1, %2; "
    "movl %2, %0; "
    : "=r"(z) // output
    : "r"(x), "r"(y) // input
  );
  return z;
}

    endbr64
    addl    $1, %edi
    leal    1(%rsi), %eax
#APP
# 4 "a.c" 1
    addl %edi, %eax; movl %eax, %eax;
# 0 "" 2
#NO_APP
    ret

0000000000000000 <foo>:
   0:  f3 0f 1e fa            endbr64
   4:  83 c7 01               add    $0x1,%edi
   7:  8d 46 01               lea    0x1(%rsi),%eax
   a:  01 f8                  add    %edi,%eax
   c:  89 c0                  mov    %eax,%eax
   e:  c3                     ret

  asm (
    "addl %1, %2; "
    "movl %2, %0; "
    : "=r"(z) // output
    : "r"(x), "r"(y) // input
  );

  asm (
    "addl %1, %0; "
    : "=r"(z) // output
    : "r"(x), "0"(y) // input
  );

0000000000000000 <foo>:
   0:  f3 0f 1e fa            endbr64
   4:  83 c7 01               add    $0x1,%edi
   7:  8d 46 01               lea    0x1(%rsi),%eax
   a:  01 f8                  add    %edi,%eax
   c:  c3                     ret

  asm (
    "addl %%ecx, %%edx; "
    : "=c"(z) // output
    : "d"(x), "c"(y) // input
  );

0000000000000000 <foo>:
   0:  f3 0f 1e fa            endbr64
   4:  8d 57 01               lea    0x1(%rdi),%edx
   7:  8d 4e 01               lea    0x1(%rsi),%ecx
   a:  01 ca                  add    %ecx,%edx
   c:  89 c8                  mov    %ecx,%eax
   e:  c3                     ret

int foo(int x, int y) {
  int z;
  x++; y++;
  asm (
    "addl %1, %2; "
    "movl %2, %0; "
    : "=r"(z) // output
    : "r"(x), "r"(y) // input
  );
  return 0;
}

0000000000000000 <foo>:
   0:  f3 0f 1e fa            endbr64
   4:  31 c0                  xor    %eax,%eax
   6:  c3                     ret

  asm volatile (
    "addl %1, %2; "
    "movl %2, %0; "
    : "=r"(z) // output
    : "r"(x), "r"(y) // input
  );

#include <stdio.h>

void foo(int x, int y) {
    asm volatile (
            "decl %%edi; "
            "movl %%edi, %%ecx; "
            :
            :
            //: "ecx"
            );
    printf("%d %d\n", x, y);
}

int main() {
    foo(2021, 2);
}

0000000000001170 <foo>:
    1170:  f3 0f 1e fa            endbr64
    1174:  89 fa                  mov    %edi,%edx
    1176:  89 f1                  mov    %esi,%ecx
    1178:  ff cf                  dec    %edi
    117a:  89 f9                  mov    %edi,%ecx
    117c:  48 8d 35 81 0e 00 00   lea    0xe81(%rip),%rsi        # 2004 <_IO_stdin_used+0x4>
    1183:  bf 01 00 00 00         mov    $0x1,%edi
    1188:  31 c0                  xor    %eax,%eax
    118a:  e9 c1 fe ff ff         jmp    1050 <__printf_chk@plt>
    118f:  90                     nop

2021 2020

0000000000001170 <foo>:
    1170:  f3 0f 1e fa            endbr64
    1174:  89 fa                  mov    %edi,%edx
    1176:  ff cf                  dec    %edi
    1178:  89 f9                  mov    %edi,%ecx
    117a:  bf 01 00 00 00         mov    $0x1,%edi
    117f:  89 f1                  mov    %esi,%ecx
    1181:  48 8d 35 7c 0e 00 00   lea    0xe7c(%rip),%rsi        # 2004 <_IO_stdin_used+0x4>
    1188:  31 c0                  xor    %eax,%eax
    118a:  e9 c1 fe ff ff         jmp    1050 <__printf_chk@plt>
    118f:  90                     nop

2021 2

vgalaxy@vgalaxy-VirtualBox:~$ curl baidu.com
<html>
<meta http-equiv="refresh" content="0;url=http://www.baidu.com/">
</html>
vgalaxy@vgalaxy-VirtualBox:~$ export PATH=
vgalaxy@vgalaxy-VirtualBox:~$ curl baidu.com
bash: curl: No such file or directory

vgalaxy@vgalaxy-VirtualBox:~$ cat a.sh
curl baidu.com
vgalaxy@vgalaxy-VirtualBox:~$ strace -f bash a.sh 2>&1 | less

newfstatat(AT_FDCWD, "/usr/lib/ccache/bash", 0x7ffc68a50a00, 0) = -1 ENOENT (No such file or directory)
newfstatat(AT_FDCWD, "/usr/local/sbin/bash", 0x7ffc68a50a00, 0) = -1 ENOENT (No such file or directory)
newfstatat(AT_FDCWD, "/usr/local/bin/bash", 0x7ffc68a50a00, 0) = -1 ENOENT (No such file or directory)
newfstatat(AT_FDCWD, "/usr/sbin/bash", 0x7ffc68a50a00, 0) = -1 ENOENT (No such file or directory)
newfstatat(AT_FDCWD, "/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=1404744, ...}, 0) = 0

vgalaxy@vgalaxy-VirtualBox:~$ echo $PATH
/usr/lib/ccache:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/bin

gcc -v a.c
make -nB

CFLAGS  := -O2 -fno-pic
LDFLAGS := -static

gcc: a.o b.o main.o
    gcc $(LDFLAGS) a.o b.o main.o

ld: a.o b.o main.o
    ld a.o b.o main.o -e main

a.o: a.c
    gcc $(CFLAGS) -c a.c

b.o: b.c
    gcc $(CFLAGS) -c b.c

main.o: main.c
    gcc $(CFLAGS) -c main.c

clean:
    rm -f *.o a.out

   8:  8b 35 00 00 00 00      mov    0x0(%rip),%esi        # e <main+0xe>
   e:  8b 3d 00 00 00 00      mov    0x0(%rip),%edi        # 14 <main+0x14>

Disassembly of section .data:

0000000000000000 <y>:
   0:  c8 00 00 00            enter  $0x0,$0x0

0000000000000004 <x>:
   4:  64 00 00               add    %al,%fs:(%rax)

Relocation section '.rela.text.startup' at offset 0x208 contains 7 entries:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
00000000000a  000500000002 R_X86_64_PC32     0000000000000000 y - 4
000000000010  000600000002 R_X86_64_PC32     0000000000000000 x - 4
000000000015  000700000004 R_X86_64_PLT32    0000000000000000 foo - 4
00000000001b  000500000002 R_X86_64_PC32     0000000000000000 y - 4
000000000021  000600000002 R_X86_64_PC32     0000000000000000 x - 4
000000000026  00020000000a R_X86_64_32       0000000000000000 .rodata.str1.1 + 0
000000000035  000800000004 R_X86_64_PLT32    0000000000000000 __printf_chk - 4

  ↓0xa
-----------------------------------
  |   4B   |               | y |
-----------------------------------
           |←    y - 4    →|
  |←          y           →|

  401798:       8b 35 52 89 0b 00       mov    0xb8952(%rip),%esi        # 4ba0f0 <y>
  40179e:       8b 3d 50 89 0b 00       mov    0xb8950(%rip),%edi        # 4ba0f4 <x>

#include <stdio.h>

extern int x, y;
int foo(int a, int b);

int main() {
  foo(x, y);
}

ld: main.o: in function `main':
main.c:(.text.startup+0x35): undefined reference to `__printf_chk'

(gdb) p $rsp
$2 = (void *) 0x7fffffffdf00
(gdb) x 0x7fffffffdf00
0x7fffffffdf00: 0x00000001

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ cat as.S
mov $231, %rax
mov $99, %rdi
syscall
vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ gcc -c as.S
vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ objdump -d as.o

as.o:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <.text>:
   0:  48 c7 c0 e7 00 00 00   mov    $0xe7,%rax
   7:  48 c7 c7 63 00 00 00   mov    $0x63,%rdi
   e:  0f 05                  syscall
vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ ld as.o
ld: warning: cannot find entry symbol _start; defaulting to 0000000000401000
vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ ./a.out
vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ echo $?
99

_start -> __libc_start_main -> ...

LDFLAGS := -static -Wl,--verbose

-Wl,option
  Pass option as an option to the linker.

using internal linker script:
==================================================
...
  .text           :
  {
    *(.text.unlikely .text.*_unlikely .text.unlikely.*)
    *(.text.exit .text.exit.*)
    *(.text.startup .text.startup.*)
    *(.text.hot .text.hot.*)
    *(SORT(.text.sorted.*))
    *(.text .stub .text.* .gnu.linkonce.t.*)
    /* .gnu.warning sections are handled specially by elf.em.  */
    *(.gnu.warning)
  }
...
  .ctors          :
  {
    /* gcc uses crtbegin.o to find the start of
       the constructors, so we make sure it is
       first.  Because this is a wildcard, it
       doesn't matter if the user does not
       actually link against crtbegin.o; the
       linker won't look for a file to match a
       wildcard.  The wildcard also means that it
       doesn't matter which directory crtbegin.o
       is in.  */
    KEEP (*crtbegin.o(.ctors))
    KEEP (*crtbegin?.o(.ctors))
    /* We don't want to include the .ctor section from
       the crtend.o file until after the sorted ctors.
       The .ctor section from the crtend file contains the
       end of ctors marker and it must be last */
    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
    KEEP (*(SORT(.ctors.*)))
    KEEP (*(.ctors))
  }
  .dtors          :
  {
    KEEP (*crtbegin.o(.dtors))
    KEEP (*crtbegin?.o(.dtors))
    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
    KEEP (*(SORT(.dtors.*)))
    KEEP (*(.dtors))
  }
...
  . = ALIGN(64 / 8);
  _end = .; PROVIDE (end = .);
  . = DATA_SEGMENT_END (.);
...

#include <stdio.h>

extern int _end;
extern int end;

typedef unsigned char *byte_pointer;

void show_bytes(byte_pointer start, size_t len) {
    size_t i;
    for (i = 0; i < len; i++)
        printf(" %.2x", start[i]);
    printf("\n");
}

void show_pointer(void *x) {
    show_bytes((byte_pointer) &x, sizeof(void *));
}

int main() {
    show_pointer(&_end);
    show_pointer(&end);
    printf("%p 0x%lx\n", &_end, &_end);
}

attempt to open a.o succeeded
a.o
attempt to open b.o succeeded
b.o
attempt to open main.o succeeded
main.o
attempt to open /usr/lib/gcc/x86_64-linux-gnu/10/libgcc.a succeeded
/usr/lib/gcc/x86_64-linux-gnu/10/libgcc.a
attempt to open /usr/lib/gcc/x86_64-linux-gnu/10/libgcc_eh.a succeeded
/usr/lib/gcc/x86_64-linux-gnu/10/libgcc_eh.a
attempt to open /usr/lib/gcc/x86_64-linux-gnu/10/libc.a failed
attempt to open /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/libc.a succeeded
/usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/libc.a
(/usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/libc.a)libc-start.o
...
attempt to open /usr/lib/gcc/x86_64-linux-gnu/10/crtend.o succeeded
/usr/lib/gcc/x86_64-linux-gnu/10/crtend.o
attempt to open /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crtn.o succeeded
/usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crtn.o

__attribute__((constructor))
__attribute__((destructor))

#include <stdio.h>
#include <stdlib.h>

__attribute__((constructor)) void f() {
    puts("start");
}

__attribute__((destructor)) void g() {
    puts("end");
}

void h() {
    puts("exit");
}

int main() {
    atexit(h);
}

vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
start
exit
end

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ strace ./a.out
execve("./a.out", ["./a.out"], 0x7fff12355620 /* 60 vars */) = 0
arch_prctl(0x3001 /* ARCH_??? */, 0x7fffbfc1d830) = -1 EINVAL (Invalid argument)
brk(NULL)                               = 0x1207000
brk(0x1207d80)                          = 0x1207d80
arch_prctl(ARCH_SET_FS, 0x1207380)      = 0
uname({sysname="Linux", nodename="vgalaxy-VirtualBox", ...}) = 0
readlink("/proc/self/exe", "/home/vgalaxy/Downloads/link-tes"..., 4096) = 39
brk(0x1228d80)                          = 0x1228d80
brk(0x1229000)                          = 0x1229000
mprotect(0x4b6000, 16384, PROT_READ)    = 0
newfstatat(1, "", {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x2), ...}, AT_EMPTY_PATH) = 0
write(1, "100 + 200 = 300\n", 16100 + 200 = 300
)       = 16
exit_group(0)                           = ?
+++ exited with 0 +++

movl $100, %rdi

movl 1234(%rip), %rdi

-no-pie
  Don't produce a dynamically linked position independent executable.

movl $1, 1234(%eip)

movl (%esp), %ebx
ret

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ ldd ./a.out
  linux-vdso.so.1 (0x00007ffd45b9f000)
  libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fbab3fdf000)
  /lib64/ld-linux-x86-64.so.2 (0x00007fbab41e2000)

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ file /lib64/ld-linux-x86-64.so.2
/lib64/ld-linux-x86-64.so.2: symbolic link to /lib/x86_64-linux-gnu/ld-2.33.so

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ file /lib/x86_64-linux-gnu/ld-2.33.so
/lib/x86_64-linux-gnu/ld-2.33.so: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked, BuildID[sha1]=2238045eb12263c1ea1dd2bb6042dff799d0d127, stripped

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ ldd /lib/x86_64-linux-gnu/ld-2.33.so
  statically linked

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ readelf -d /lib/x86_64-linux-gnu/ld-2.33.so

Dynamic section at offset 0x32e70 contains 19 entries:
  Tag        Type                         Name/Value
 0x000000000000000e (SONAME)             Library soname: [ld-linux-x86-64.so.2]
 0x0000000000000004 (HASH)               0x2f0
 0x000000006ffffef5 (GNU_HASH)           0x3b8
 0x0000000000000005 (STRTAB)             0x790
 0x0000000000000006 (SYMTAB)             0x4a8
 0x000000000000000a (STRSZ)              549 (bytes)
 0x000000000000000b (SYMENT)             24 (bytes)
 0x0000000000000003 (PLTGOT)             0x34000
 0x0000000000000002 (PLTRELSZ)           96 (bytes)
 0x0000000000000014 (PLTREL)             RELA
 0x0000000000000017 (JMPREL)             0xb90
 0x0000000000000007 (RELA)               0xaa0
 0x0000000000000008 (RELASZ)             240 (bytes)
 0x0000000000000009 (RELAENT)            24 (bytes)
 0x000000006ffffffc (VERDEF)             0x9f8
 0x000000006ffffffd (VERDEFNUM)          5
 0x000000006ffffff0 (VERSYM)             0x9b6
 0x000000006ffffff9 (RELACOUNT)          8
 0x0000000000000000 (NULL)               0x0

cat $(which ldd) | less

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ /lib64/ld-linux-x86-64.so.2 --list ./a.out
  linux-vdso.so.1 (0x00007ffc337cc000)
  libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f76aa390000)
  /lib64/ld-linux-x86-64.so.2 (0x00007f76aa593000)

vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ /lib64/ld-linux-x86-64.so.2 ./a.out
100 + 200 = 300
vgalaxy@vgalaxy-VirtualBox:~/Downloads/link-test$ ./a.out
100 + 200 = 300

vgalaxy@vgalaxy-VirtualBox:~/Templates$ cat a.py
#! /usr/bin/env python3
print("HELLO")
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.py
HELLO
vgalaxy@vgalaxy-VirtualBox:~/Templates$ python3 ./a.py
HELLO

call *table[PRINTF]

printf@plt:
  jmp *table[PRINTF]
  push $PRINTF
  call resolve

#include <stdio.h>
#include <assert.h>
#include <stdint.h>

typedef uint32_t u32;

typedef struct {
  u32 pc, n;
  char from, to, via;
} Frame;

#define call(...) ({ *(++top) = (Frame) { .pc = 0, __VA_ARGS__ }; })
#define ret()     ({ top--; })

void hanoi(int n, char from, char to, char via) {
  Frame stk[64], *top = stk - 1;
  call(n, from, to, via);
  for (Frame *f; (f = top) >= stk; f->pc++) {
    switch (f->pc) {
      case 0: if (f->n == 1) printf("%c -> %c\n", f->from, f->to), f->pc = 3; break;
      case 1: call(f->n - 1, f->from, f->via, f->to);   break;
      case 2: call(       1, f->from, f->to,  f->via);  break;
      case 3: call(f->n - 1, f->via,  f->to,  f->from); break;
      case 4: ret();                                    break;
      default: assert(0);
    }
  }
}

int main() {
    hanoi(10, 'A', 'B', 'C');
}

// after each instruction
if (has_exception) {
  exception_handler();
}
if (has_interrupt && int_enabled) {
  interrupt_handler();
}

-------       ----------
| CPU |-------| Memory |
-------       ----------
   |
   |
--------------------------------- BUS
  |             |           |
 Reg: status   Reg: cmd    Reg: data

-------       ----------
| CPU |-------| Memory |
-------   |   ----------
          |
          |
--------------------------------- BUS
  |             |           |
 Reg: status   Reg: cmd    Reg: data

static inline uint8_t  inb(uintptr_t addr) { return *(volatile uint8_t  *)addr; }
static inline uint16_t inw(uintptr_t addr) { return *(volatile uint16_t *)addr; }
static inline uint32_t inl(uintptr_t addr) { return *(volatile uint32_t *)addr; }

static inline void outb(uintptr_t addr, uint8_t  data) { *(volatile uint8_t  *)addr = data; }
static inline void outw(uintptr_t addr, uint16_t data) { *(volatile uint16_t *)addr = data; }
static inline void outl(uintptr_t addr, uint32_t data) { *(volatile uint32_t *)addr = data; }

io_read -> ioe_read -> 回调函数 -> inb
io_write -> ioe_write -> 回调函数 -> outb

-------       ----------
| CPU |-------| Memory |
-------   |   ----------
          |
          |
--------------------------------- BUS
  |             |           |
 Reg: status   Reg: cmd    Reg: data (.ps)
  |             |           |
  ↓             ↓           ↓
  ---------------------------
  |                         |
  |         Printer         |
  |                         |
  |-------------------------|

%!
% http://www.cs.cmu.edu/afs/andrew/scs/cs/15-463/98/pub/www/assts/ps.html

72 72 scale % scale coordinate system so units are inches, not points
2 2 translate   % put origin 2 inches from lower left of page

/Symbol findfont 4 scalefont setfont
% current font is now Symbol about 4 inches high
gsave   % save graphics state (coordinate system & stuff)
.5 setgray
60 rotate
0 0 moveto (abcde) show
grestore    % restore previous graphics state

/Helvetica-Bold findfont .2 scalefont setfont
% current font is now slanted Helvetica about .2 inches high
0 4 moveto (Postscript is good at this stuff) show

/Times-Italic findfont 2 scalefont setfont
% current font is now italic Times about 2 inches high
1 0 0 setrgbcolor
0 6 moveto (yowza!) show

showpage

-------       ----------
| CPU |-------| Memory |
-------   |   ----------
          |
          |
--------------------------------- PCI BUS
  |           |         |
 USB BUS     GPU       SSD
  |
 USB

vgalaxy@vgalaxy-VirtualBox:~/Downloads$ lspci
00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
00:01.1 IDE interface: Intel Corporation 82371AB/EB/MB PIIX4 IDE (rev 01)
00:02.0 VGA compatible controller: VMware SVGA II Adapter
00:03.0 Ethernet controller: Intel Corporation 82540EM Gigabit Ethernet Controller (rev 02)
00:04.0 System peripheral: InnoTek Systemberatung GmbH VirtualBox Guest Service
00:05.0 Multimedia audio controller: Intel Corporation 82801AA AC'97 Audio Controller (rev 01)
00:06.0 USB controller: Apple Inc. KeyLargo/Intrepid USB
00:07.0 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 08)
00:0d.0 SATA controller: Intel Corporation 82801HM/HEM (ICH8M/ICH8M-E) SATA Controller [AHCI mode] (rev 02)
vgalaxy@vgalaxy-VirtualBox:~/Downloads$ lsusb
Bus 001 Device 002: ID 80ee:0021 VirtualBox USB Tablet
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

             ——— ———    -------        ----------
  Clock------| PIC |----| CPU |--------| Memory |
             ——— ———    -------    |   ----------
                |                  |
                |                  |
------------------------------------------- PCI BUS
  |           |         |
 USB BUS     GPU       SSD
  |
 USB

for (int i = 1; i <= H; i++) {
  for (int j = 1; j <= W; j++)
    putchar(j <= i ? '*' : ' ');
  putchar('\n');
}

for (int x = 0, pos = 0; x < HEIGHT; x++) { // 行扫描
  for (int y = 0; y < WIDTH; y++, pos++) {
    vbuf[pos] = draw(x, y); // 算出 (x,y) 的贴块 (和颜色)
  }
}

76543210
||||||||
||||||++- Palette
|||+++--- Unimplemented
||+------ Priority
|+------- Flip horizontally
+-------- Flip vertically

#include <stdio.h>

int main() {
    int a, b;
    scanf("%d %d", &a, &b);
    printf("%d + %d = %d", a, b, a + b);
}

:map <F9> :w<CR> :!gcc a.c && ./a.out < in.txt<CR>

      -
     -
    -
   -
  -
 -
-

   |------------
   |
   |
   |
   |
---|

                 ——— ——— INT --------       ----------
Clock ----|------| PIC |-----| CPU |--------| Memory |
Keyboard -|      ——— ———     --------    |  ----------
Mouse ----|         |                    |
                    |                    |
------------------------------------------- PCI BUS
  |           |         |
 USB BUS     GPU       SSD
  |
 USB

|    ...    |
|    xxx    | ---- old rsp
|    xxx    |
|    xxx    |
|    xxx    |
|    xxx    |
|           | ---- new rsp

|------|
| SS0  |
| RSP0 |
|------|
    |
    |       |    ...    |
    |-------|    xxx    |
            |    xxx    |
            |    xxx    |
            |    xxx    |
            |    xxx    |
            |           |

                      |--------------| --------- handler
cmp  %eax, %ebx ----- |    call      |
                      |  save regs   |
                      |  ..........  |
                      |  ..........  |
                      |  ..........  |
                      | restore regs |
             jz ----- |     ret      |
                      |--------------|

int main() {
    asm volatile ("cli");
    while (1);
}

0000000000001129 <main>:
    1129:  f3 0f 1e fa            endbr64
    112d:  55                     push   %rbp
    112e:  48 89 e5               mov    %rsp,%rbp
    1131:  fa                     cli
    1132:  eb fe                  jmp    1132 <main+0x9>
    1134:  66 2e 0f 1f 84 00 00   cs nopw 0x0(%rax,%rax,1)
    113b:  00 00 00
    113e:  66 90                  xchg   %ax,%ax

#define _GNU_SOURCE

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <ucontext.h>
#include <stdint.h>

void on_sigsegv(int sig, siginfo_t *info, void *ucontext) {
  ucontext_t *ctx = (ucontext_t *)ucontext;
  uint8_t *pc = (void *)ctx->uc_mcontext.gregs[REG_RIP];
  printf("PC = %p  ", pc);
  for (int i = -8; i < 8; i++) {
    printf(i == 0 ? "[%02x] " : "%02x ", pc[i]);
  }
  printf("\n");
  exit(1);
}

int main() {
  struct sigaction act;
  act.sa_sigaction = on_sigsegv;
  sigemptyset(&act.sa_mask);
  act.sa_flags = SA_SIGINFO;
  sigaction(SIGSEGV, &act, NULL);
  asm volatile("cli");
}

vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
PC = 0x556b07f3d2ed  00 00 00 e8 c3 fd ff ff [fa] b8 00 00 00 00 48 8b
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
PC = 0x561bd85f52ed  00 00 00 e8 c3 fd ff ff [fa] b8 00 00 00 00 48 8b
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
PC = 0x55e47ba5c2ed  00 00 00 e8 c3 fd ff ff [fa] b8 00 00 00 00 48 8b
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
PC = 0x55f2865fa2ed  00 00 00 e8 c3 fd ff ff [fa] b8 00 00 00 00 48 8b
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
PC = 0x55c5075192ed  00 00 00 e8 c3 fd ff ff [fa] b8 00 00 00 00 48 8b

void f1(int *xp, int *yp) {
    *xp += *yp;
    *xp += *yp;
}

void f2(int *xp, int *yp) {
    *xp += 2 * *yp;
}

#include <stdio.h>

int foo(int* ptr1, long* ptr2) {
    *ptr1 = 10;
    *ptr2 = 11;
    return *ptr1;
}

int main() {
    long a = 11.0;
    int result = foo((int*)&a, &a);
    printf("%d\n", result);
    return 0;
}

vgalaxy@vgalaxy-VirtualBox:~/Templates$ gcc -O2 b.c
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
10
vgalaxy@vgalaxy-VirtualBox:~/Templates$ gcc -O1 b.c
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
11

vgalaxy@vgalaxy-VirtualBox:~/Templates$ gcc -O2 b.c -fno-strict-aliasing
vgalaxy@vgalaxy-VirtualBox:~/Templates$ ./a.out
11

void lower1(char *s)
{
    long i;

    for (i = 0; i < strlen(s); i++)
    if (s[i] >= 'A' && s[i] <= 'Z')
        s[i] -= ('A' - 'a');
}

void lower2(char *s)
{
    long i;
    long len = strlen(s);

    for (i = 0; i < len; i++)
    if (s[i] >= 'A' && s[i] <= 'Z')
        s[i] -= ('A' - 'a');
}

#include <stdio.h>

long counter = 0;
long f() {
    return counter ++;
}

long func1() {
    return f() + f() + f() + f();
}

long func2() {
    return 4 * f();
}

int main() {
    counter = 0;
    printf("%ld\n", func1());

    counter = 0;
    printf("%ld\n", func2());
}

0000000000001165 <func1>:
    1165:  f3 0f 1e fa            endbr64
    1169:  55                     push   %rbp
    116a:  48 89 e5               mov    %rsp,%rbp
    116d:  53                     push   %rbx
    116e:  b8 00 00 00 00         mov    $0x0,%eax
    1173:  e8 d1 ff ff ff         call   1149 <f>
    1178:  48 89 c3               mov    %rax,%rbx
    117b:  b8 00 00 00 00         mov    $0x0,%eax
    1180:  e8 c4 ff ff ff         call   1149 <f>
    1185:  48 01 c3               add    %rax,%rbx
    1188:  b8 00 00 00 00         mov    $0x0,%eax
    118d:  e8 b7 ff ff ff         call   1149 <f>
    1192:  48 01 c3               add    %rax,%rbx
    1195:  b8 00 00 00 00         mov    $0x0,%eax
    119a:  e8 aa ff ff ff         call   1149 <f>
    119f:  48 01 d8               add    %rbx,%rax
    11a2:  48 8b 5d f8            mov    -0x8(%rbp),%rbx
    11a6:  c9                     leave
    11a7:  c3                     ret

00000000000011d0 <func1>:
    11d0:  f3 0f 1e fa            endbr64
    11d4:  48 8b 05 3d 2e 00 00   mov    0x2e3d(%rip),%rax        # 4018 <counter>
    11db:  48 8d 50 04            lea    0x4(%rax),%rdx
    11df:  48 8d 04 85 06 00 00   lea    0x6(,%rax,4),%rax
    11e6:  00
    11e7:  48 89 15 2a 2e 00 00   mov    %rdx,0x2e2a(%rip)        # 4018 <counter>
    11ee:  c3                     ret
    11ef:  90                     nop

long func1in() {
    long t = counter++; /* +0 */
    t += counter++;     /* +1 */
    t += counter++;     /* +2 */
    t += counter++;     /* +3 */
    return t;
}

long func1opt() {
    long t = 4 * counter + 6;
    counter += 4;
    return t;
}

/usr/bin/ld: /tmp/ccRZahyM.o: in function `func1':
a.c:(.text+0x13): undefined reference to `f'
/usr/bin/ld: a.c:(.text+0x20): undefined reference to `f'
/usr/bin/ld: a.c:(.text+0x2d): undefined reference to `f'
/usr/bin/ld: a.c:(.text+0x3a): undefined reference to `f'
/usr/bin/ld: /tmp/ccRZahyM.o: in function `func2':
a.c:(.text+0x55): undefined reference to `f'
collect2: error: ld returned 1 exit status

#include <stdio.h>
#include <stdint.h>
#include <sys/time.h>

// typedef double data_t;
// #define OP *
// #define IDENT 1

typedef int data_t;
#define OP +
#define IDENT 0

#define LENGTH 10000000
data_t data[LENGTH];

void combine1(data_t *dest) {
  long i = 0;
  data_t acc = IDENT;
  for (; i < LENGTH; ++i)
      acc = acc OP data[i];
  *dest = acc;
}

void combine2(data_t *dest) {
  long i = 0;
  data_t acc = IDENT;
  long limit = LENGTH - 1;
  for (; i < limit; i += 2)
      acc = acc OP data[i] OP data[i + 1];
  for (; i < LENGTH; ++i)
      acc = acc OP data[i];
  *dest = acc;
}

void combine3(data_t *dest) {
  long i = 0;
  data_t acc = IDENT;
  long limit = LENGTH - 1;
  for (; i < limit; i += 2)
      acc = acc OP (data[i] OP data[i + 1]);
  for (; i < LENGTH; ++i)
      acc = acc OP data[i];
  *dest = acc;
}

void combine4(data_t *dest) {
  long i = 0;
  data_t acc0 = IDENT;
  data_t acc1 = IDENT;
  long limit = LENGTH - 1;
  for (; i < limit; i += 2) {
      acc0 = acc0 OP data[i];
      acc1 = acc1 OP data[i + 1];
  }
  for (; i < LENGTH; ++i)
      acc0 = acc0 OP data[i];
  *dest = acc0 OP acc1;
}

int main() {
  data_t res;
  uint64_t use;
  long i = 0;
  for (; i < LENGTH; ++i) data[i] = (data_t) (i + 1);
  struct timeval t1, t2;

  gettimeofday(&t1, NULL);
  combine1(&res);
  gettimeofday(&t2, NULL);
  use = (t2.tv_sec - t1.tv_sec) * 1000000 + (t2.tv_usec - t1.tv_usec);
  printf("combine1: %lu\n", use);

  gettimeofday(&t1, NULL);
  combine2(&res);
  gettimeofday(&t2, NULL);
  use = (t2.tv_sec - t1.tv_sec) * 1000000 + (t2.tv_usec - t1.tv_usec);
  printf("combine2: %lu\n", use);

  gettimeofday(&t1, NULL);
  combine3(&res);
  gettimeofday(&t2, NULL);
  use = (t2.tv_sec - t1.tv_sec) * 1000000 + (t2.tv_usec - t1.tv_usec);
  printf("combine3: %lu\n", use);

  gettimeofday(&t1, NULL);
  combine4(&res);
  gettimeofday(&t2, NULL);
  use = (t2.tv_sec - t1.tv_sec) * 1000000 + (t2.tv_usec - t1.tv_usec);
  printf("combine4: %lu\n", use);
}

#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>

int main() {
  for (int i = 0; i < 3; i++) {
    fork(); // create some processes
  }

  volatile int *ptr = mmap(
    (void *)0x20000000,          // mapping address (hint)
    1 << 20,                     // mapping size
    PROT_WRITE | PROT_READ,      // read/write mapping
    MAP_PRIVATE | MAP_ANONYMOUS, // mapping flags
    -1,                          // file descriptor
    0                            // offset
  );

  *ptr = getpid();
  printf("#%d sets %p = %d\n", getpid(), ptr, getpid());

  sleep(1);
  printf("#%d *%p = %d\n", getpid(), ptr, *ptr);
}

#3930 sets 0x20000000 = 3930
#3933 sets 0x20000000 = 3933
#3932 sets 0x20000000 = 3932
#3931 sets 0x20000000 = 3931
#3934 sets 0x20000000 = 3934
#3936 sets 0x20000000 = 3936
#3935 sets 0x20000000 = 3935
#3937 sets 0x20000000 = 3937
#3930 *0x20000000 = 3930
#3933 *0x20000000 = 3933
#3932 *0x20000000 = 3932
#3931 *0x20000000 = 3931
#3934 *0x20000000 = 3934
#3936 *0x20000000 = 3936
#3935 *0x20000000 = 3935
#3937 *0x20000000 = 3937

        Fork         Fork       Fork
─────────┬────────────┬───────────┬─────────►
         │            │           │
         │            │           │
         │            │           └─────────►
         │            │
         │            │
         │            │         Fork
         │            └───────────┬─────────►
         │                        │
         │                        │
         │                        └─────────►
         │
         │
         │           Fork       Fork
         └────────────┬───────────┬─────────►
                      │           │
                      │           │
                      │           └─────────►
                      │
                      │
                      │         Fork
                      └───────────┬─────────►
                                  │
                                  │
                                  └─────────►

bool     vme_init  (void *(*alloc)(int), void (*free)(void *));
void     protect   (AddrSpace *a);
void     unprotect (AddrSpace *a);
void     map       (AddrSpace *a, void *va, void *pa, int prot);
Context *ucontext  (AddrSpace *a, Area kstack, void *entry);

                   PA                                VA
           ┌─────────────────┐              ┌─────────────────┐
           │                 │              │                 │
           │                 │              │                 │
           │                 │              │                 │
           │                 │              │                 │
           │                 │              │                 │
           │                 │              │                 │
           │                 │              │                 │
           │                 │              │                 │
           │                 │              │                 │
           │                 │              ├─────────────────┤  0xc0021000
           │                 │              │                 │
           │                 │              │                 │
           │                 │       ┌─────►│                 │
           │                 │       │      ├─────────────────┤  0xc0020000
           │                 │       │      │                 │
0x21000    ├─────────────────┤       │      │                 │
           │                 │       │      │                 │
           │                 ├───────┘      │                 │
           │                 │              │                 │
0x20000    ├─────────────────┤              │                 │
           │                 │              │                 │
           │                 │              │                 │
           │                 │              │                 │
           └─────────────────┘              └─────────────────┘

┌────────────────┬────────────────┬──────────────────────────┐
│     10-bits    │     10-bits    │         12-bits          │
└────────────────┴────────────────┴──────────────────────────┘

┌───────────┬──────────┬──────────┬──────────┬─────────────────────┐
│   9-bits  │  9-bits  │  9-bits  │  9-bits  │      12-bits        │
└───────────┴──────────┴──────────┴──────────┴─────────────────────┘

0000000000000000 <.text>:
   0:  48 c7 c0 00 00 00 00   mov    $0x0,%rax
   7:  48 c7 c1 00 00 00 00   mov    $0x0,%rcx
   e:  48 c7 c2 00 00 00 00   mov    $0x0,%rdx
  15:  48 c7 c3 00 00 00 00   mov    $0x0,%rbx
  1c:  48 c7 c4 00 00 00 00   mov    $0x0,%rsp
  23:  48 c7 c5 00 00 00 00   mov    $0x0,%rbp
  2a:  48 c7 c6 00 00 00 00   mov    $0x0,%rsi
  31:  48 c7 c7 00 00 00 00   mov    $0x0,%rdi
  38:  49 c7 c0 00 00 00 00   mov    $0x0,%r8
  3f:  49 c7 c1 00 00 00 00   mov    $0x0,%r9
  46:  49 c7 c2 00 00 00 00   mov    $0x0,%r10
  4d:  49 c7 c3 00 00 00 00   mov    $0x0,%r11
  54:  49 c7 c4 00 00 00 00   mov    $0x0,%r12
  5b:  49 c7 c5 00 00 00 00   mov    $0x0,%r13
  62:  49 c7 c6 00 00 00 00   mov    $0x0,%r14
  69:  49 c7 c7 00 00 00 00   mov    $0x0,%r15

if (x == 1)
  %rax++;
else
  %rcx++;

char buf[SIZE];
cin >> buf;

// %rcx: 无权限访问的地址; %rbx: 未载入缓存的数组
        xorq   %rax, %rax
retry:  movzbq (%rcx), %rax   // 非法访问; Page Fault
        shlq   $0xc, %rax
        jz     retry
        movq   (%rbx, %rax), %rbx // (%rbx + (%rcx) * 4096)

do {
  rax = *ptr;
  rax << 12;
} while (rax == 0);

rbx = rbx[rax];

$ strace 2>&1 gcc a.c | vim -

unlink("/tmp/ccPSr2ZR.res")             = 0
unlink("/tmp/ccocFDMt.o")               = 0
unlink("/tmp/ccezma3p.s")               = 0
exit_group(0)                           = ?
+++ exited with 0 +++

unlink - call the unlink function to remove the specified file

openat(AT_FDCWD, "/tmp/ccezma3p.s", O_RDWR|O_CREAT|O_EXCL, 0600) = 4
close(4)                                = 0
access("/usr/lib/gcc/x86_64-linux-gnu/10/cc1", X_OK) = 0
pipe2([4, 5], O_CLOEXEC)                = 0
vfork()                                 = 4694
close(5)                                = 0
read(4, "", 16)                         = 0
close(4)                                = 0
wait4(4694, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 4694

openat(AT_FDCWD, "/tmp/ccfzJbeR.s", O_RDWR|O_CREAT|O_EXCL, 0600) = 4
close(4)                                = 0
newfstatat(AT_FDCWD, "/usr/lib/gcc/x86_64-linux-gnu/10/cc1", {st_mode=S_IFREG|0755, st_size=25697696, ...}, 0) = 0
access("/usr/lib/gcc/x86_64-linux-gnu/10/cc1", X_OK) = 0
pipe2([4, 5], O_CLOEXEC)                = 0
vfork( <unfinished ...>
[pid  5870] close(4)                    = 0
[pid  5870] execve("/usr/lib/gcc/x86_64-linux-gnu/10/cc1", ["/usr/lib/gcc/x86_64-linux-gnu/10"..., "-quiet", "-imultiarch", "x86_64-linux-gnu", "a.c", "-quiet", "-dumpbase", "a.c", "-mtune=generic", "-march=x86-64", "-auxbase", "a", "-fasynchronous-unwind-tables", "-fstack-protector-strong", "-Wformat", "-Wformat-security", "-fstack-clash-protection", "-fcf-protection", "-o", "/tmp/ccfzJbeR.s"], 0xe6c030 /* 72 vars */ <unfinished ...>
...

[pid  5870] openat(AT_FDCWD, "/tmp/ccfzJbeR.s", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 4
...
[pid  5870] write(4, "\t.file\t\"a.c\"\n\t.text\n\t.globl\tmain"..., 552) = 552

[pid  5870] openat(AT_FDCWD, "a.c", O_RDONLY|O_NOCTTY) = 4
...
[pid  5870] openat(AT_FDCWD, "/usr/include/stdc-predef.h", O_RDONLY|O_NOCTTY) = 5
...

[pid  5871] execve("/usr/lib/ccache/as", ["as", "--64", "-o", "/tmp/ccbXLqzq.o", "/tmp/ccfzJbeR.s"], 0xe6c030 /* 72 vars */) = -1 ENOENT (No such file or directory)
[pid  5871] execve("/usr/local/sbin/as", ["as", "--64", "-o", "/tmp/ccbXLqzq.o", "/tmp/ccfzJbeR.s"], 0xe6c030 /* 72 vars */) = -1 ENOENT (No such file or directory)
[pid  5871] execve("/usr/local/bin/as", ["as", "--64", "-o", "/tmp/ccbXLqzq.o", "/tmp/ccfzJbeR.s"], 0xe6c030 /* 72 vars */) = -1 ENOENT (No such file or directory)
[pid  5871] execve("/usr/sbin/as", ["as", "--64", "-o", "/tmp/ccbXLqzq.o", "/tmp/ccfzJbeR.s"], 0xe6c030 /* 72 vars */) = -1 ENOENT (No such file or directory)
[pid  5871] execve("/usr/bin/as", ["as", "--64", "-o", "/tmp/ccbXLqzq.o", "/tmp/ccfzJbeR.s"], 0xe6c030 /* 72 vars */ <unfinished ...>

set detach-on-fork off
set follow-fork-mode child
set breakpoint pending on

file gcc

break execve
commands
  silent
  echo \n\n\n---------- EXECVE ----------\n
  printf "program to execute: %s\n", $rdi
  set $i = 0
  set $argv = (char **)$rsi
  while ($argv[$i])
    printf "argv[%d] = %s\n", $i, $argv[$i]
    set $i = $i + 1
  end
  echo \n
end

run a.c

$ gdb -x gdb-internals.txt

---------- EXECVE ----------
program to execute: /usr/bin/gcc
argv[0] = /usr/bin/gcc
argv[1] = a.c

---------- EXECVE ----------
program to execute: /usr/lib/gcc/x86_64-linux-gnu/10/cc1
argv[0] = /usr/lib/gcc/x86_64-linux-gnu/10/cc1
argv[1] = -quiet
argv[2] = -imultiarch
argv[3] = x86_64-linux-gnu
argv[4] = a.c
argv[5] = -quiet
argv[6] = -dumpbase
argv[7] = a.c
argv[8] = -mtune=generic
argv[9] = -march=x86-64
argv[10] = -auxbase
argv[11] = a
argv[12] = -fasynchronous-unwind-tables
argv[13] = -fstack-protector-strong
argv[14] = -Wformat
argv[15] = -Wformat-security
argv[16] = -fstack-clash-protection
argv[17] = -fcf-protection
argv[18] = -o
argv[19] = /tmp/ccv9Jkb6.s