《Linux系统编程训练营》0-2_深入理解系统调用

揭示系统 API 的奥秘

Linux 系统架构

应用程序运行之后得到用户进程

模式切换的本质（系统调用的本质）

系统模式切换依赖于 CPU 提供的工作方式
一般来说，大部分 CPU 至少具有两种工作方式
- 高特权级 (Ring 0) : 可以访问任意的数据，包括外围设备，比如网卡、硬盘等（内核模式）
- 低特权级 (Ring 3) : 只能受限的访问内存，并且不允许访问外围设备，可被打断（用户模式）
系统模式切换通过执行特殊的 CPU 指令发起（int 0x80，触发中断）
应用程序（进程）无法直接切换 CPU 的工作方式
系统调用是应用程序（进程）请求模式切换的唯一方式

系统调用的真面目

char *s = "D.T.Software\n;"
int l = 13;

asm volatile (
    "movl $s, %%eax\n"  // 指定编号为 4 的系统调用（sys_write）
    "movl $1, %%ebx\n"  // 指定 sys_write 的输出目标， 1 为标准输出
    "movl %0, %%ecx\n"  // 指定输出字符串地址
    "movl %1, %%edx\n"  // 指定输出字符串长度
    "int $0x80     \n"  // 执行系统调用
    :                   // 忽略输出参数
    : "r"(s), "r"(l)
    : "eax", "ebx", "ecx", "edx");  // 保留寄存去，不用于关联变量

void print(const char *s, int l)
{
    asm volatile (
      "movl $s, %%eax\n"  // sys_write
      "movl $1, %%ebx\n" 
      "movl %0, %%ecx\n" 
      "movl %1, %%edx\n"
      "int $0x80     \n"  // 80H Service
      :      
      : "r"(s), "r"(l)    // parameter
      : "eax", "ebx", "ecx", "edx");  // 保留寄存去，不用于关联变量
}

系统调用和系统 API 实现示例

#define SysCall(type, cmd, param1, param2)  asm volatile (
                  "movl $"#type", %%eax\n"        \
                  "movl $"#cmd",  %%ebx\n"        \ 
                  "movl %0,       %%ecx\n"        \
                  "movl %1,       %%edx\n"        \
                  "int $0x80           \n"        \
                  :                               \
                  : "r"(param1), "r"(param2)      \
                  : "eax", "ebx", "ecx", "edx"    \
                )

void RegApp(const char *name, void(*tmain)(), byte pri)
{
    if (name && tmain) {
        AppInof info = {0};
        
        info.name = name;
        info.tmain = tmain;
        info.priority = pri;
        
        SysCall(0, 2, &info, 0);
    }
}

编程实验：系统调用的本质

直接使用系统调用 program.c

第 1 处不同，没有引用头文件
第 2 处不同，没有 main 函数
第 3 处不同，函数里面嵌入了汇编代码

void print(const char *s, int l);
void exit(int code);

void program()
{
    print("Hello World!\n", 13);
    exit(0);
}

void print(const char *s, int l)
{
    asm volatile (
        "movl $4, %%eax\n"
        "movl $1, %%ebx\n"
        "movl %0, %%ecx\n"
        "movl %1, %%edx\n"
        "int $0x80     \n"
        :
        : "r"(s), "r"(l)
        : "eax", "ebx", "ecx", "edx"
    );
}

void exit(int code) 
{
    asm volatile (
        "movl $1, %%eax\n"
        "movl %0, %%ebx\n"
        "int $0x80     \n"
        :
        : "r"(code)
        : "eax", "ebx"
    );    
}

编译：
gcc -m32 -e program -fno-builtin -nostartfiles  program.c -o program.out

-m32 : 指定使用 32 位编译方式
-e program : 指定 program 函数为入口
-fno-builtin -nostartfiles : 不需要 _start 函数

运行：
Hello World!

借助第三方库 main.c

#include <stdio.h>

int main()
{
    printf("Hello World!\n");

    return 0;
}

编译：
gcc main.c -o main.out

运行：
Hello World!

值得思考的问题

如何判断一个应用程序（进程）触发了系统调用？

相同功能的代码实现

python

print('Hello World!')

perl

print "Hello World!\n"

C++

#include "iostream"
using namespace std;
int main()
{
    cout << "Hello World!" << endl;
    return 0;
}

C#

namespace Test {
    class Program {
        static void Main(string[] args)
        {
            Console.Write("Hello World\n");
        }
    }
}

strace - 系统调用探测器

strace 用户监控进程与内核的交付（监控系统调用）
starce 用于追踪进程内部状态（定位运行时问题）
starce 按序输出进程运行过程系统调用名称，参数和返回值

strace 程序性能分析

tiansong@tiansong:~/Desktop$ strace -tt -T -o program.log ./program.out 
Hello World!

program.log

20:49:43.455558 execve("./program.out", ["./program.out"], 0x7ffd4866f4f0 /* 41 vars */) = 0 <0.000543>
20:49:43.456490 brk(NULL)               = 0x57eb4000 <0.000090>
20:49:43.456758 arch_prctl(0x3001 /* ARCH_??? */, 0xffe88698) = -1 EINVAL (Invalid argument) <0.000087>
20:49:43.457239 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) <0.000242>
20:49:43.457786 mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xf7f95000 <0.000226>
20:49:43.458639 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) <0.000726>
20:49:43.459965 set_thread_area({entry_number=-1, base_addr=0xf7f959c0, limit=0x0fffff, seg_32bit=1, contents=0, read_exec_only=0, limit_in_pages=1, seg_not_present=0, useable=1}) = 0 (entry_number=12) <0.000489>
20:49:43.460899 mprotect(0x565c7000, 4096, PROT_READ) = 0 <0.000247>
20:49:43.461308 write(1, "Hello World!\n", 13) = 13 <0.000162>
20:49:43.461744 exit(0)                 = ?
20:49:43.462040 +++ exited with 0 +++

man execve
man brk

查看依赖

tiansong@tiansong:~/Desktop$ ldd program.out 
        statically linked

tiansong@tiansong:~/Desktop$ strace -c ./program.out 
strace: [ Process PID=3691 runs in 32 bit mode. ]
Hello World!
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
  0.00    0.000000           0         1           execve
------ ----------- ----------- --------- --------- ----------------
100.00    0.000000                     1           total
System call usage summary for 32 bit mode:
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
  0.00    0.000000           0         1           write
  0.00    0.000000           0         2         2 access
  0.00    0.000000           0         1           brk
  0.00    0.000000           0         1           mprotect
  0.00    0.000000           0         1           mmap2
  0.00    0.000000           0         1           set_thread_area
  0.00    0.000000           0         1         1 arch_prctl
------ ----------- ----------- --------- --------- ----------------
100.00    0.000008                     8         3 total

tiansong@tiansong:~/Desktop$ strace -tt -T ./a.out 
20:49:16.540739 execve("./a.out", ["./a.out"], 0x7ffdf1b95370 /* 41 vars */) = 0 <0.000394>
20:49:16.541439 brk(NULL)               = 0x55a4e7477000 <0.000090>
20:49:16.541730 arch_prctl(0x3001 /* ARCH_??? */, 0x7ffe0f8e6a60) = -1 EINVAL (Invalid argument) <0.000088>
20:49:16.542141 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) <0.000150>
20:49:16.542615 openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 <0.000146>
20:49:16.542949 fstat(3, {st_mode=S_IFREG|0644, st_size=73887, ...}) = 0 <0.000117>
20:49:16.543361 mmap(NULL, 73887, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f6df5276000 <0.000187>
20:49:16.543696 close(3)                = 0 <0.000108>
20:49:16.544083 openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 <0.000534>
20:49:16.544859 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\300A\2\0\0\0\0\0"..., 832) = 832 <0.000131>
20:49:16.545221 pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784 <0.000169>
20:49:16.545577 pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32 <0.000133>
20:49:16.546027 pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\30x\346\264ur\f|Q\226\236i\253-'o"..., 68, 880) = 68 <0.000106>
20:49:16.546356 fstat(3, {st_mode=S_IFREG|0755, st_size=2029592, ...}) = 0 <0.000182>
20:49:16.546723 mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f6df5274000 <0.000096>
20:49:16.547047 pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784 <0.000091>
20:49:16.547426 pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32 <0.000375>
20:49:16.548194 pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\30x\346\264ur\f|Q\226\236i\253-'o"..., 68, 880) = 68 <0.000175>
20:49:16.548696 mmap(NULL, 2037344, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f6df5082000 <0.000283>
20:49:16.549183 mmap(0x7f6df50a4000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7f6df50a4000 <0.000117>
20:49:16.549507 mmap(0x7f6df521c000, 319488, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19a000) = 0x7f6df521c000 <0.000177>
20:49:16.549875 mmap(0x7f6df526a000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f6df526a000 <0.000301>
20:49:16.550483 mmap(0x7f6df5270000, 13920, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f6df5270000 <0.000295>
20:49:16.551340 close(3)                = 0 <0.000251>
20:49:16.551837 arch_prctl(ARCH_SET_FS, 0x7f6df5275540) = 0 <0.000148>
20:49:16.552355 mprotect(0x7f6df526a000, 16384, PROT_READ) = 0 <0.000143>
20:49:16.552720 mprotect(0x55a4e6f29000, 4096, PROT_READ) = 0 <0.000197>
20:49:16.553099 mprotect(0x7f6df52b6000, 4096, PROT_READ) = 0 <0.000423>
20:49:16.553795 munmap(0x7f6df5276000, 73887) = 0 <0.000281>
20:49:16.554455 fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x3), ...}) = 0 <0.000791>
20:49:16.555759 brk(NULL)               = 0x55a4e7477000 <0.000404>
20:49:16.556416 brk(0x55a4e7498000)     = 0x55a4e7498000 <0.000268>
20:49:16.557149 write(1, "Hello World!\n", 13Hello World!
) = 13 <0.000127>
20:49:16.557496 exit_group(0)           = ?
20:49:16.557904 +++ exited with 0 +++

查看依赖

tiansong@tiansong:~/Desktop$ ldd a.out
        linux-vdso.so.1 (0x00007ffc13f0f000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f95f22f0000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f95f24fc000)

tiansong@tiansong:~/Desktop$ strace -c ./a.out 
Hello World!
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
  0.00    0.000000           0         1           read
  0.00    0.000000           0         1           write
  0.00    0.000000           0         2           close
  0.00    0.000000           0         3           fstat
  0.00    0.000000           0         7           mmap
  0.00    0.000000           0         3           mprotect
  0.00    0.000000           0         1           munmap
  0.00    0.000000           0         3           brk
  0.00    0.000000           0         6           pread64
  0.00    0.000000           0         1         1 access
  0.00    0.000000           0         1           execve
  0.00    0.000000           0         2         1 arch_prctl
  0.00    0.000000           0         2           openat
------ ----------- ----------- --------- --------- ----------------
100.00    0.000012                    33         2 total

strace - 用法详解

• -c -- count time, calls, and errors for each syscall and report summary
• -f -- follow forks
• -ff -- with output into separate files
• -F -- attempt to follow vforks
• -i -- print instruction pointer at time of syscall
• -q -- suppress messages about attaching, detaching, etc.
• -r -- print relative timestamp
• -t -- absolute timestamp,
• -tt -- with usecs
• -T -- print time spent in each syscall,
• -v -- verbose mode: print unabbreviated argv, stat, termio[s], etc. args
• -x -- print non-ascii strings in hex,
• -xx -- print all strings in hex
• -o file -- send trace output to FILE instead of stderr
• -O overhead -- set overhead for tracing syscalls to OVERHEAD usecs
• -p pid -- trace process with process id PID, may be repeated
• -D -- run tracer process as a detached grandchild, not as parent
• -s strsize -- limit length of print strings to STRSIZE chars (default 32)
• -S sortby -- sort syscall counts by: time, calls, name, nothing (default time)

-e expr : 指定一个表达式，用来控制如何跟踪

 -e trace=set 跟踪指定的系统调用
    如： -e trace=open,close,rean,write 表示只跟踪这四个系统调用
 -e trace=file 跟踪有关文件操作的系统调用
 -e trace=process 跟踪有关进程控制的系统调用
 -e trace=network 跟踪与网络有关的所有系统调用
 -e strace=signal 跟踪所有与系统信号有关的系统调用
 -e trace=ipc 跟踪所有与进程通讯有关的系统调用
 -e raw=set 将指定的系统调用的参数以十六进制显示
 -e signal=set 指定跟踪的系统信号
   如： signal=!SIGIO(或者signal=!IO)，表示不跟踪 SIGIO 信号
 -e read=set 输出从指定文件中读出的数据
   如： -e read=3,5
 -e write=set 输出写入到指定文件中的数据

编程实验：strace 程序逆向分析

在只有可执行程序 fcopy.out 的前提下，探究其实现
通过 read、 write 的交替，大概可判断为文件的复制

tiansong@tiansong:~/Desktop$ strace ./fcopy.out new_a.out a.out 
execve("./fcopy.out", ["./fcopy.out", "new_a.out", "a.out"], 0x7fff7dbfd8f0 /* 41 vars */) = 0
brk(NULL)                               = 0x55b198e42000
arch_prctl(0x3001 /* ARCH_??? */, 0x7ffc282006b0) = -1 EINVAL (Invalid argument)
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=73887, ...}) = 0
mmap(NULL, 73887, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fc31c5f6000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\300A\2\0\0\0\0\0"..., 832) = 832
pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784
pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32
pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\30x\346\264ur\f|Q\226\236i\253-'o"..., 68, 880) = 68
fstat(3, {st_mode=S_IFREG|0755, st_size=2029592, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fc31c5f4000
pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784
pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32
pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\30x\346\264ur\f|Q\226\236i\253-'o"..., 68, 880) = 68
mmap(NULL, 2037344, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fc31c402000
mmap(0x7fc31c424000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7fc31c424000
mmap(0x7fc31c59c000, 319488, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19a000) = 0x7fc31c59c000
mmap(0x7fc31c5ea000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7fc31c5ea000
mmap(0x7fc31c5f0000, 13920, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fc31c5f0000
close(3)                                = 0
arch_prctl(ARCH_SET_FS, 0x7fc31c5f5540) = 0
mprotect(0x7fc31c5ea000, 16384, PROT_READ) = 0
mprotect(0x55b198828000, 4096, PROT_READ) = 0
mprotect(0x7fc31c636000, 4096, PROT_READ) = 0
munmap(0x7fc31c5f6000, 73887)           = 0
openat(AT_FDCWD, "new_a.out", O_WRONLY|O_CREAT, 0600) = 3
openat(AT_FDCWD, "a.out", O_RDONLY)     = 4
read(4, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0`\20\0\0\0\0\0\0"..., 512) = 512
write(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0`\20\0\0\0\0\0\0"..., 512) = 512
read(4, "\4\0\0\0\4\0\0\0X\3\0\0\0\0\0\0X\3\0\0\0\0\0\0X\3\0\0\0\0\0\0"..., 512) = 512
write(3, "\4\0\0\0\4\0\0\0X\3\0\0\0\0\0\0X\3\0\0\0\0\0\0X\3\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\37\0\0\0\22\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\37\0\0\0\22\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\363\17\36\372H\203\354\10H\213\5\331/\0\0H\205\300t\2\377\320H\203\304\10\303\0\0\0\0\0"..., 512) = 512
write(3, "\363\17\36\372H\203\354\10H\213\5\331/\0\0H\205\300t\2\377\320H\203\304\10\303\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\1\0\2\0Hello World!\0\0\0\0\1\33\3;@\0\0\0\7\0\0\0"..., 512) = 512
write(3, "\1\0\2\0Hello World!\0\0\0\0\1\33\3;@\0\0\0\7\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\270=\0\0\0\0\0\0\33\0\0\0\0\0\0\0\10\0\0\0\0\0\0\0\32\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\270=\0\0\0\0\0\0\33\0\0\0\0\0\0\0\10\0\0\0\0\0\0\0\32\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\10@\0\0\0\0\0\0GCC: (Ubuntu 9.4"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\10@\0\0\0\0\0\0GCC: (Ubuntu 9.4"..., 512) = 512
read(4, "\0\0\0\0\0\0\0\0\0\0\0\0\3\0\23\0\24 \0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\3\0\23\0\24 \0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\255\0\0\0\0\0\25\0\300=\0\0\0\0\0\0\0\0\0\0\0\0\0\0\276\0\0\0\1\0\27\0"..., 512) = 512
write(3, "\255\0\0\0\0\0\25\0\300=\0\0\0\0\0\0\0\0\0\0\0\0\0\0\276\0\0\0\1\0\27\0"..., 512) = 512
read(4, "I\21\0\0\0\0\0\0\33\0\0\0\0\0\0\0\300\1\0\0\21\2\31\0\20@\0\0\0\0\0\0"..., 512) = 512
write(3, "I\21\0\0\0\0\0\0\33\0\0\0\0\0\0\0\300\1\0\0\21\2\31\0\20@\0\0\0\0\0\0"..., 512) = 512
read(4, "u_init\0__bss_start\0main\0__TMC_EN"..., 512) = 512
write(3, "u_init\0__bss_start\0main\0__TMC_EN"..., 512) = 512
read(4, "\2\0\0\0\0\0\0\08\3\0\0\0\0\0\08\3\0\0\0\0\0\0 \0\0\0\0\0\0\0"..., 512) = 512
write(3, "\2\0\0\0\0\0\0\08\3\0\0\0\0\0\08\3\0\0\0\0\0\0 \0\0\0\0\0\0\0"..., 512) = 512
read(4, "\2\0\0\0\0\0\0\0 \5\0\0\0\0\0\0 \5\0\0\0\0\0\0\300\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\2\0\0\0\0\0\0\0 \5\0\0\0\0\0\0 \5\0\0\0\0\0\0\300\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\2\0\0\0\0\0\0\0\0 \0\0\0\0\0\0\0 \0\0\0\0\0\0\21\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\2\0\0\0\0\0\0\0\0 \0\0\0\0\0\0\0 \0\0\0\0\0\0\21\0\0\0\0\0\0\0"..., 512) = 512
read(4, "\3\0\0\0\0\0\0\0\20@\0\0\0\0\0\0\0200\0\0\0\0\0\0\10\0\0\0\0\0\0\0"..., 512) = 312
write(3, "\3\0\0\0\0\0\0\0\20@\0\0\0\0\0\0\0200\0\0\0\0\0\0\10\0\0\0\0\0\0\0"..., 312) = 312
read(4, "", 512)                        = 0
close(3)                                = 0
close(4)                                = 0
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x3), ...}) = 0
brk(NULL)                               = 0x55b198e42000
brk(0x55b198e63000)                     = 0x55b198e63000
write(1, "copy completed\n", 15copy completed
)        = 15
exit_group(0)                           = ?
+++ exited with 0 +++

fcopy.c

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int file_copy(const char* dst, const char* src)
{
    int dfd = open(dst, O_WRONLY|O_CREAT, 0600);
    int sfd = open(src, O_RDONLY);
    int ret = 0;
    
    if( dfd == -1 )
    {
        ret = -1;
    }
    else if( sfd == -1 )
    {
        ret = -2;
    }
    else if( (dfd != -1) && (sfd != -1) )
    {
        char buf[512] = {0};
        int len = 0;

        while( (len = read(sfd, buf, sizeof(buf))) > 0 )
        {
            write(dfd, buf, len);
        }

        close(dfd);
        close(sfd);
    }
    
    return ret;
}

int main(char argc, char* argv[])
{
    if( argc > 2 )
    {
        if( file_copy(argv[1], argv[2]) == 0) 
        {
            printf("copy completed\n");
        }
        else
        {
            printf("copy failed\n");
        }   
    }
    else
    {
        printf("parameter error\n");
    }

    return 0;
}

编程实验：应用程序错误定位

tiansong@tiansong:~/Desktop$ ./fcopy.out /new_folder/new_a.out 
a.out 
copy failed  // 应用程序报错

tiansong@tiansong:~/Desktop$ strace ./fcopy.out /new_folder/new_a.out a.out 
execve("./fcopy.out", ["./fcopy.out", "/new_folder/new_a.out", "a.out"], 0x7ffef202d8c0 /* 41 vars */) = 0
brk(NULL)                               = 0x55da5b131000
arch_prctl(0x3001 /* ARCH_??? */, 0x7ffff7aaec10) = -1 EINVAL (Invalid argument)
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)  // 错误定位
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=73887, ...}) = 0
mmap(NULL, 73887, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f0b8eac7000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\300A\2\0\0\0\0\0"..., 832) = 832
pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784
pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32
pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\30x\346\264ur\f|Q\226\236i\253-'o"..., 68, 880) = 68
fstat(3, {st_mode=S_IFREG|0755, st_size=2029592, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f0b8eac5000
pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784
pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32
pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\30x\346\264ur\f|Q\226\236i\253-'o"..., 68, 880) = 68
mmap(NULL, 2037344, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f0b8e8d3000
mmap(0x7f0b8e8f5000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7f0b8e8f5000
mmap(0x7f0b8ea6d000, 319488, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19a000) = 0x7f0b8ea6d000
mmap(0x7f0b8eabb000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f0b8eabb000
mmap(0x7f0b8eac1000, 13920, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f0b8eac1000
close(3)                                = 0
arch_prctl(ARCH_SET_FS, 0x7f0b8eac6540) = 0
mprotect(0x7f0b8eabb000, 16384, PROT_READ) = 0
mprotect(0x55da5abe0000, 4096, PROT_READ) = 0
mprotect(0x7f0b8eb07000, 4096, PROT_READ) = 0
munmap(0x7f0b8eac7000, 73887)           = 0
openat(AT_FDCWD, "/new_folder/new_a.out", O_WRONLY|O_CREAT, 0600) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "a.out", O_RDONLY)     = 3
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x3), ...}) = 0
brk(NULL)                               = 0x55da5b131000
brk(0x55da5b152000)                     = 0x55da5b152000
write(1, "copy failed\n", 12copy failed
)           = 12
exit_group(0)                           = ?
+++ exited with 0 +++

编程实验：strace 程序数据分析

查看程序执行过程中所涉及的数据

tiansong@tiansong:~/Desktop$ strace -xx -s  512 ./fcopy.out  /n
ew_a.out a.out 
execve("\x2e\x2f\x66\x63\x6f\x70\x79\x2e\x6f\x75\x74", ["\x2e\x2f\x66\x63\x6f\x70\x79\x2e\x6f\x75\x74", "\x2f\x6e\x65\x77\x5f\x61\x2e\x6f\x75\x74", "\x61\x2e\x6f\x75\x74"], 0x7fff63fd54e8 /* 41 vars */) = 0
brk(NULL)                               = 0x5649cb7b0000
arch_prctl(0x3001 /* ARCH_??? */, 0x7ffdd8ed6540) = -1 EINVAL (Invalid argument)
access("\x2f\x65\x74\x63\x2f\x6c\x64\x2e\x73\x6f\x2e\x70\x72\x65\x6c\x6f\x61\x64", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "\x2f\x65\x74\x63\x2f\x6c\x64\x2e\x73\x6f\x2e\x63\x61\x63\x68\x65", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=73887, ...}) = 0
mmap(NULL, 73887, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fbd28ca5000
close(3)                                = 0
openat(AT_FDCWD, "\x2f\x6c\x69\x62\x2f\x78\x38\x36\x5f\x36\x34\x2d\x6c\x69\x6e\x75\x78\x2d\x67\x6e\x75\x2f\x6c\x69\x62\x63\x2e\x73\x6f\x2e\x36", O_RDONLY|O_CLOEXEC) = 3
read(3, "\x7f\x45\x4c\x46\x02\x01\x01\x03\x00\x00\x00\x00\x00\x00\x00\x00\x03\x00\x3e\x00\x01\x00\x00\x00\xc0\x41\x02\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x18\xe7\x1e\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00\x38\x00\x0e\x00\x40\x00\x44\x00\x43\x00\x06\x00\x00\x00\x04\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x10\x03\x00\x00\x00\x00\x00\x00\x10\x03\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x04\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\x1c\x00\x00\x00\x00\x00\x00\x00\x1c\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xe8\x14\x02\x00\x00\x00\x00\x00\xe8\x14\x02\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x05\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x24\x76\x17\x00\x00\x00\x00\x00\x24\x76\x17\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x04\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\xc4\xd2\x04\x00\x00\x00\x00\x00\xc4\xd2\x04\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x06\x00\x00\x00\x88\x77\x1e\x00\x00\x00\x00\x00\x88\x87\x1e\x00\x00\x00\x00\x00\x88\x87\x1e\x00\x00\x00\x00\x00\x18\x50\x00\x00\x00\x00\x00\x00\xd8\x8e\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x06\x00\x00\x00\x80\xab\x1e\x00\x00\x00\x00\x00\x80\xbb\x1e\x00\x00\x00\x00\x00\x80\xbb\x1e\x00\x00\x00\x00\x00\xe0\x01\x00\x00\x00\x00\x00\x00\xe0\x01\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x04\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00"..., 832) = 832
pread64(3, "\x06\x00\x00\x00\x04\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x10\x03\x00\x00\x00\x00\x00\x00\x10\x03\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x04\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\x1c\x00\x00\x00\x00\x00\x00\x00\x1c\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xe8\x14\x02\x00\x00\x00\x00\x00\xe8\x14\x02\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x05\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x24\x76\x17\x00\x00\x00\x00\x00\x24\x76\x17\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x04\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\xc4\xd2\x04\x00\x00\x00\x00\x00\xc4\xd2\x04\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x06\x00\x00\x00\x88\x77\x1e\x00\x00\x00\x00\x00\x88\x87\x1e\x00\x00\x00\x00\x00\x88\x87\x1e\x00\x00\x00\x00\x00\x18\x50\x00\x00\x00\x00\x00\x00\xd8\x8e\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x06\x00\x00\x00\x80\xab\x1e\x00\x00\x00\x00\x00\x80\xbb\x1e\x00\x00\x00\x00\x00\x80\xbb\x1e\x00\x00\x00\x00\x00\xe0\x01\x00\x00\x00\x00\x00\x00\xe0\x01\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x04\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x04\x00\x00\x00\x70\x03\x00\x00\x00\x00\x00\x00\x70\x03\x00\x00\x00\x00\x00\x00\x70\x03\x00\x00\x00\x00\x00\x00\x44\x00\x00\x00\x00\x00\x00\x00\x44\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x07\x00\x00\x00\x04\x00\x00\x00"..., 784, 64) = 784
pread64(3, "\x04\x00\x00\x00\x10\x00\x00\x00\x05\x00\x00\x00\x47\x4e\x55\x00\x02\x00\x00\xc0\x04\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00", 32, 848) = 32
pread64(3, "\x04\x00\x00\x00\x14\x00\x00\x00\x03\x00\x00\x00\x47\x4e\x55\x00\x18\x78\xe6\xb4\x75\x72\x0c\x7c\x51\x96\x9e\x69\xab\x2d\x27\x6f\xae\x6d\x1d\xee\x04\x00\x00\x00\x10\x00\x00\x00\x01\x00\x00\x00\x47\x4e\x55\x00\x00\x00\x00\x00\x03\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00", 68, 880) = 68
fstat(3, {st_mode=S_IFREG|0755, st_size=2029592, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fbd28ca3000
pread64(3, "\x06\x00\x00\x00\x04\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x10\x03\x00\x00\x00\x00\x00\x00\x10\x03\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x03\x00\x00\x00\x04\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\xa0\xe6\x1b\x00\x00\x00\x00\x00\x1c\x00\x00\x00\x00\x00\x00\x00\x1c\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xe8\x14\x02\x00\x00\x00\x00\x00\xe8\x14\x02\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x05\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x00\x20\x02\x00\x00\x00\x00\x00\x24\x76\x17\x00\x00\x00\x00\x00\x24\x76\x17\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x04\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\x00\xa0\x19\x00\x00\x00\x00\x00\xc4\xd2\x04\x00\x00\x00\x00\x00\xc4\xd2\x04\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x06\x00\x00\x00\x88\x77\x1e\x00\x00\x00\x00\x00\x88\x87\x1e\x00\x00\x00\x00\x00\x88\x87\x1e\x00\x00\x00\x00\x00\x18\x50\x00\x00\x00\x00\x00\x00\xd8\x8e\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x06\x00\x00\x00\x80\xab\x1e\x00\x00\x00\x00\x00\x80\xbb\x1e\x00\x00\x00\x00\x00\x80\xbb\x1e\x00\x00\x00\x00\x00\xe0\x01\x00\x00\x00\x00\x00\x00\xe0\x01\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x04\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x50\x03\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x04\x00\x00\x00\x70\x03\x00\x00\x00\x00\x00\x00\x70\x03\x00\x00\x00\x00\x00\x00\x70\x03\x00\x00\x00\x00\x00\x00\x44\x00\x00\x00\x00\x00\x00\x00\x44\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x07\x00\x00\x00\x04\x00\x00\x00"..., 784, 64) = 784
pread64(3, "\x04\x00\x00\x00\x10\x00\x00\x00\x05\x00\x00\x00\x47\x4e\x55\x00\x02\x00\x00\xc0\x04\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00", 32, 848) = 32
pread64(3, "\x04\x00\x00\x00\x14\x00\x00\x00\x03\x00\x00\x00\x47\x4e\x55\x00\x18\x78\xe6\xb4\x75\x72\x0c\x7c\x51\x96\x9e\x69\xab\x2d\x27\x6f\xae\x6d\x1d\xee\x04\x00\x00\x00\x10\x00\x00\x00\x01\x00\x00\x00\x47\x4e\x55\x00\x00\x00\x00\x00\x03\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00", 68, 880) = 68
mmap(NULL, 2037344, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fbd28ab1000
mmap(0x7fbd28ad3000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7fbd28ad3000
mmap(0x7fbd28c4b000, 319488, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19a000) = 0x7fbd28c4b000
mmap(0x7fbd28c99000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7fbd28c99000
mmap(0x7fbd28c9f000, 13920, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fbd28c9f000
close(3)                                = 0
arch_prctl(ARCH_SET_FS, 0x7fbd28ca4540) = 0
mprotect(0x7fbd28c99000, 16384, PROT_READ) = 0
mprotect(0x5649c9a24000, 4096, PROT_READ) = 0
mprotect(0x7fbd28ce5000, 4096, PROT_READ) = 0
munmap(0x7fbd28ca5000, 73887)           = 0
openat(AT_FDCWD, "\x2f\x6e\x65\x77\x5f\x61\x2e\x6f\x75\x74", O_WRONLY|O_CREAT, 0600) = -1 EACCES (Permission denied)
openat(AT_FDCWD, "\x61\x2e\x6f\x75\x74", O_RDONLY) = 3
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x3), ...}) = 0
brk(NULL)                               = 0x5649cb7b0000
brk(0x5649cb7d1000)                     = 0x5649cb7d1000
write(1, "\x63\x6f\x70\x79\x20\x66\x61\x69\x6c\x65\x64\x0a", 12copy failed
) = 12
exit_group(0)                           = ?
+++ exited with 0 +++

tiansong@tiansong:~/Desktop$ strace -e read=3 ./fcopy.out  /new_a.out a.out 
execve("./fcopy.out", ["./fcopy.out", "/new_a.out", "a.out"], 0x7fff6dde78e0 /* 41 vars */) = 0
brk(NULL)                               = 0x55eda4dca000
arch_prctl(0x3001 /* ARCH_??? */, 0x7ffd1320ade0) = -1 EINVAL (Invalid argument)
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=73887, ...}) = 0
mmap(NULL, 73887, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f1ede05a000
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\300A\2\0\0\0\0\0"..., 832) = 832
 | 00000  7f 45 4c 46 02 01 01 03  00 00 00 00 00 00 00 00  .ELF............ |
 | 00010  03 00 3e 00 01 00 00 00  c0 41 02 00 00 00 00 00  ..>......A...... |
 | 00020  40 00 00 00 00 00 00 00  18 e7 1e 00 00 00 00 00  @............... |
 | 00030  00 00 00 00 40 00 38 00  0e 00 40 00 44 00 43 00  ....@.8...@.D.C. |
 | 00040  06 00 00 00 04 00 00 00  40 00 00 00 00 00 00 00  ........@....... |
 | 00050  40 00 00 00 00 00 00 00  40 00 00 00 00 00 00 00  @.......@....... |
 | 00060  10 03 00 00 00 00 00 00  10 03 00 00 00 00 00 00  ................ |
 | 00070  08 00 00 00 00 00 00 00  03 00 00 00 04 00 00 00  ................ |
 | 00080  a0 e6 1b 00 00 00 00 00  a0 e6 1b 00 00 00 00 00  ................ |
 | 00090  a0 e6 1b 00 00 00 00 00  1c 00 00 00 00 00 00 00  ................ |
 | 000a0  1c 00 00 00 00 00 00 00  10 00 00 00 00 00 00 00  ................ |
 | 000b0  01 00 00 00 04 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 000c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 000d0  e8 14 02 00 00 00 00 00  e8 14 02 00 00 00 00 00  ................ |
 | 000e0  00 10 00 00 00 00 00 00  01 00 00 00 05 00 00 00  ................ |
 | 000f0  00 20 02 00 00 00 00 00  00 20 02 00 00 00 00 00  . ....... ...... |
 | 00100  00 20 02 00 00 00 00 00  24 76 17 00 00 00 00 00  . ......$v...... |
 | 00110  24 76 17 00 00 00 00 00  00 10 00 00 00 00 00 00  $v.............. |
 | 00120  01 00 00 00 04 00 00 00  00 a0 19 00 00 00 00 00  ................ |
 | 00130  00 a0 19 00 00 00 00 00  00 a0 19 00 00 00 00 00  ................ |
 | 00140  c4 d2 04 00 00 00 00 00  c4 d2 04 00 00 00 00 00  ................ |
 | 00150  00 10 00 00 00 00 00 00  01 00 00 00 06 00 00 00  ................ |
 | 00160  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00170  88 87 1e 00 00 00 00 00  18 50 00 00 00 00 00 00  .........P...... |
 | 00180  d8 8e 00 00 00 00 00 00  00 10 00 00 00 00 00 00  ................ |
 | 00190  02 00 00 00 06 00 00 00  80 ab 1e 00 00 00 00 00  ................ |
 | 001a0  80 bb 1e 00 00 00 00 00  80 bb 1e 00 00 00 00 00  ................ |
 | 001b0  e0 01 00 00 00 00 00 00  e0 01 00 00 00 00 00 00  ................ |
 | 001c0  08 00 00 00 00 00 00 00  04 00 00 00 04 00 00 00  ................ |
 | 001d0  50 03 00 00 00 00 00 00  50 03 00 00 00 00 00 00  P.......P....... |
 | 001e0  50 03 00 00 00 00 00 00  20 00 00 00 00 00 00 00  P....... ....... |
 | 001f0  20 00 00 00 00 00 00 00  08 00 00 00 00 00 00 00   ............... |
 | 00200  04 00 00 00 04 00 00 00  70 03 00 00 00 00 00 00  ........p....... |
 | 00210  70 03 00 00 00 00 00 00  70 03 00 00 00 00 00 00  p.......p....... |
 | 00220  44 00 00 00 00 00 00 00  44 00 00 00 00 00 00 00  D.......D....... |
 | 00230  04 00 00 00 00 00 00 00  07 00 00 00 04 00 00 00  ................ |
 | 00240  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00250  88 87 1e 00 00 00 00 00  10 00 00 00 00 00 00 00  ................ |
 | 00260  90 00 00 00 00 00 00 00  08 00 00 00 00 00 00 00  ................ |
 | 00270  53 e5 74 64 04 00 00 00  50 03 00 00 00 00 00 00  S.td....P....... |
 | 00280  50 03 00 00 00 00 00 00  50 03 00 00 00 00 00 00  P.......P....... |
 | 00290  20 00 00 00 00 00 00 00  20 00 00 00 00 00 00 00   ....... ....... |
 | 002a0  08 00 00 00 00 00 00 00  50 e5 74 64 04 00 00 00  ........P.td.... |
 | 002b0  bc e6 1b 00 00 00 00 00  bc e6 1b 00 00 00 00 00  ................ |
 | 002c0  bc e6 1b 00 00 00 00 00  d4 5e 00 00 00 00 00 00  .........^...... |
 | 002d0  d4 5e 00 00 00 00 00 00  04 00 00 00 00 00 00 00  .^.............. |
 | 002e0  51 e5 74 64 06 00 00 00  00 00 00 00 00 00 00 00  Q.td............ |
 | 002f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 00300  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 00310  10 00 00 00 00 00 00 00  52 e5 74 64 04 00 00 00  ........R.td.... |
 | 00320  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00330  88 87 1e 00 00 00 00 00  78 38 00 00 00 00 00 00  ........x8...... |
pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784
 | 00000  06 00 00 00 04 00 00 00  40 00 00 00 00 00 00 00  ........@....... |
 | 00010  40 00 00 00 00 00 00 00  40 00 00 00 00 00 00 00  @.......@....... |
 | 00020  10 03 00 00 00 00 00 00  10 03 00 00 00 00 00 00  ................ |
 | 00030  08 00 00 00 00 00 00 00  03 00 00 00 04 00 00 00  ................ |
 | 00040  a0 e6 1b 00 00 00 00 00  a0 e6 1b 00 00 00 00 00  ................ |
 | 00050  a0 e6 1b 00 00 00 00 00  1c 00 00 00 00 00 00 00  ................ |
 | 00060  1c 00 00 00 00 00 00 00  10 00 00 00 00 00 00 00  ................ |
 | 00070  01 00 00 00 04 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 00080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 00090  e8 14 02 00 00 00 00 00  e8 14 02 00 00 00 00 00  ................ |
 | 000a0  00 10 00 00 00 00 00 00  01 00 00 00 05 00 00 00  ................ |
 | 000b0  00 20 02 00 00 00 00 00  00 20 02 00 00 00 00 00  . ....... ...... |
 | 000c0  00 20 02 00 00 00 00 00  24 76 17 00 00 00 00 00  . ......$v...... |
 | 000d0  24 76 17 00 00 00 00 00  00 10 00 00 00 00 00 00  $v.............. |
 | 000e0  01 00 00 00 04 00 00 00  00 a0 19 00 00 00 00 00  ................ |
 | 000f0  00 a0 19 00 00 00 00 00  00 a0 19 00 00 00 00 00  ................ |
 | 00100  c4 d2 04 00 00 00 00 00  c4 d2 04 00 00 00 00 00  ................ |
 | 00110  00 10 00 00 00 00 00 00  01 00 00 00 06 00 00 00  ................ |
 | 00120  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00130  88 87 1e 00 00 00 00 00  18 50 00 00 00 00 00 00  .........P...... |
 | 00140  d8 8e 00 00 00 00 00 00  00 10 00 00 00 00 00 00  ................ |
 | 00150  02 00 00 00 06 00 00 00  80 ab 1e 00 00 00 00 00  ................ |
 | 00160  80 bb 1e 00 00 00 00 00  80 bb 1e 00 00 00 00 00  ................ |
 | 00170  e0 01 00 00 00 00 00 00  e0 01 00 00 00 00 00 00  ................ |
 | 00180  08 00 00 00 00 00 00 00  04 00 00 00 04 00 00 00  ................ |
 | 00190  50 03 00 00 00 00 00 00  50 03 00 00 00 00 00 00  P.......P....... |
 | 001a0  50 03 00 00 00 00 00 00  20 00 00 00 00 00 00 00  P....... ....... |
 | 001b0  20 00 00 00 00 00 00 00  08 00 00 00 00 00 00 00   ............... |
 | 001c0  04 00 00 00 04 00 00 00  70 03 00 00 00 00 00 00  ........p....... |
 | 001d0  70 03 00 00 00 00 00 00  70 03 00 00 00 00 00 00  p.......p....... |
 | 001e0  44 00 00 00 00 00 00 00  44 00 00 00 00 00 00 00  D.......D....... |
 | 001f0  04 00 00 00 00 00 00 00  07 00 00 00 04 00 00 00  ................ |
 | 00200  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00210  88 87 1e 00 00 00 00 00  10 00 00 00 00 00 00 00  ................ |
 | 00220  90 00 00 00 00 00 00 00  08 00 00 00 00 00 00 00  ................ |
 | 00230  53 e5 74 64 04 00 00 00  50 03 00 00 00 00 00 00  S.td....P....... |
 | 00240  50 03 00 00 00 00 00 00  50 03 00 00 00 00 00 00  P.......P....... |
 | 00250  20 00 00 00 00 00 00 00  20 00 00 00 00 00 00 00   ....... ....... |
 | 00260  08 00 00 00 00 00 00 00  50 e5 74 64 04 00 00 00  ........P.td.... |
 | 00270  bc e6 1b 00 00 00 00 00  bc e6 1b 00 00 00 00 00  ................ |
 | 00280  bc e6 1b 00 00 00 00 00  d4 5e 00 00 00 00 00 00  .........^...... |
 | 00290  d4 5e 00 00 00 00 00 00  04 00 00 00 00 00 00 00  .^.............. |
 | 002a0  51 e5 74 64 06 00 00 00  00 00 00 00 00 00 00 00  Q.td............ |
 | 002b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 002c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 002d0  10 00 00 00 00 00 00 00  52 e5 74 64 04 00 00 00  ........R.td.... |
 | 002e0  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 002f0  88 87 1e 00 00 00 00 00  78 38 00 00 00 00 00 00  ........x8...... |
 | 00300  78 38 00 00 00 00 00 00  01 00 00 00 00 00 00 00  x8.............. |
pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32
 | 00000  04 00 00 00 10 00 00 00  05 00 00 00 47 4e 55 00  ............GNU. |
 | 00010  02 00 00 c0 04 00 00 00  03 00 00 00 00 00 00 00  ................ |
pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\30x\346\264ur\f|Q\226\236i\253-'o"..., 68, 880) = 68
 | 00000  04 00 00 00 14 00 00 00  03 00 00 00 47 4e 55 00  ............GNU. |
 | 00010  18 78 e6 b4 75 72 0c 7c  51 96 9e 69 ab 2d 27 6f  .x..ur.|Q..i.-'o |
 | 00020  ae 6d 1d ee 04 00 00 00  10 00 00 00 01 00 00 00  .m.............. |
 | 00030  47 4e 55 00 00 00 00 00  03 00 00 00 02 00 00 00  GNU............. |
 | 00040  00 00 00 00                                       ....             |
fstat(3, {st_mode=S_IFREG|0755, st_size=2029592, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1ede058000
pread64(3, "\6\0\0\0\4\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 784, 64) = 784
 | 00000  06 00 00 00 04 00 00 00  40 00 00 00 00 00 00 00  ........@....... |
 | 00010  40 00 00 00 00 00 00 00  40 00 00 00 00 00 00 00  @.......@....... |
 | 00020  10 03 00 00 00 00 00 00  10 03 00 00 00 00 00 00  ................ |
 | 00030  08 00 00 00 00 00 00 00  03 00 00 00 04 00 00 00  ................ |
 | 00040  a0 e6 1b 00 00 00 00 00  a0 e6 1b 00 00 00 00 00  ................ |
 | 00050  a0 e6 1b 00 00 00 00 00  1c 00 00 00 00 00 00 00  ................ |
 | 00060  1c 00 00 00 00 00 00 00  10 00 00 00 00 00 00 00  ................ |
 | 00070  01 00 00 00 04 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 00080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 00090  e8 14 02 00 00 00 00 00  e8 14 02 00 00 00 00 00  ................ |
 | 000a0  00 10 00 00 00 00 00 00  01 00 00 00 05 00 00 00  ................ |
 | 000b0  00 20 02 00 00 00 00 00  00 20 02 00 00 00 00 00  . ....... ...... |
 | 000c0  00 20 02 00 00 00 00 00  24 76 17 00 00 00 00 00  . ......$v...... |
 | 000d0  24 76 17 00 00 00 00 00  00 10 00 00 00 00 00 00  $v.............. |
 | 000e0  01 00 00 00 04 00 00 00  00 a0 19 00 00 00 00 00  ................ |
 | 000f0  00 a0 19 00 00 00 00 00  00 a0 19 00 00 00 00 00  ................ |
 | 00100  c4 d2 04 00 00 00 00 00  c4 d2 04 00 00 00 00 00  ................ |
 | 00110  00 10 00 00 00 00 00 00  01 00 00 00 06 00 00 00  ................ |
 | 00120  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00130  88 87 1e 00 00 00 00 00  18 50 00 00 00 00 00 00  .........P...... |
 | 00140  d8 8e 00 00 00 00 00 00  00 10 00 00 00 00 00 00  ................ |
 | 00150  02 00 00 00 06 00 00 00  80 ab 1e 00 00 00 00 00  ................ |
 | 00160  80 bb 1e 00 00 00 00 00  80 bb 1e 00 00 00 00 00  ................ |
 | 00170  e0 01 00 00 00 00 00 00  e0 01 00 00 00 00 00 00  ................ |
 | 00180  08 00 00 00 00 00 00 00  04 00 00 00 04 00 00 00  ................ |
 | 00190  50 03 00 00 00 00 00 00  50 03 00 00 00 00 00 00  P.......P....... |
 | 001a0  50 03 00 00 00 00 00 00  20 00 00 00 00 00 00 00  P....... ....... |
 | 001b0  20 00 00 00 00 00 00 00  08 00 00 00 00 00 00 00   ............... |
 | 001c0  04 00 00 00 04 00 00 00  70 03 00 00 00 00 00 00  ........p....... |
 | 001d0  70 03 00 00 00 00 00 00  70 03 00 00 00 00 00 00  p.......p....... |
 | 001e0  44 00 00 00 00 00 00 00  44 00 00 00 00 00 00 00  D.......D....... |
 | 001f0  04 00 00 00 00 00 00 00  07 00 00 00 04 00 00 00  ................ |
 | 00200  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00210  88 87 1e 00 00 00 00 00  10 00 00 00 00 00 00 00  ................ |
 | 00220  90 00 00 00 00 00 00 00  08 00 00 00 00 00 00 00  ................ |
 | 00230  53 e5 74 64 04 00 00 00  50 03 00 00 00 00 00 00  S.td....P....... |
 | 00240  50 03 00 00 00 00 00 00  50 03 00 00 00 00 00 00  P.......P....... |
 | 00250  20 00 00 00 00 00 00 00  20 00 00 00 00 00 00 00   ....... ....... |
 | 00260  08 00 00 00 00 00 00 00  50 e5 74 64 04 00 00 00  ........P.td.... |
 | 00270  bc e6 1b 00 00 00 00 00  bc e6 1b 00 00 00 00 00  ................ |
 | 00280  bc e6 1b 00 00 00 00 00  d4 5e 00 00 00 00 00 00  .........^...... |
 | 00290  d4 5e 00 00 00 00 00 00  04 00 00 00 00 00 00 00  .^.............. |
 | 002a0  51 e5 74 64 06 00 00 00  00 00 00 00 00 00 00 00  Q.td............ |
 | 002b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 002c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 002d0  10 00 00 00 00 00 00 00  52 e5 74 64 04 00 00 00  ........R.td.... |
 | 002e0  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 002f0  88 87 1e 00 00 00 00 00  78 38 00 00 00 00 00 00  ........x8...... |
 | 00300  78 38 00 00 00 00 00 00  01 00 00 00 00 00 00 00  x8.............. |
pread64(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32, 848) = 32
 | 00000  04 00 00 00 10 00 00 00  05 00 00 00 47 4e 55 00  ............GNU. |
 | 00010  02 00 00 c0 04 00 00 00  03 00 00 00 00 00 00 00  ................ |
pread64(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\30x\346\264ur\f|Q\226\236i\253-'o"..., 68, 880) = 68
 | 00000  04 00 00 00 14 00 00 00  03 00 00 00 47 4e 55 00  ............GNU. |
 | 00010  18 78 e6 b4 75 72 0c 7c  51 96 9e 69 ab 2d 27 6f  .x..ur.|Q..i.-'o |
 | 00020  ae 6d 1d ee 04 00 00 00  10 00 00 00 01 00 00 00  .m.............. |
 | 00030  47 4e 55 00 00 00 00 00  03 00 00 00 02 00 00 00  GNU............. |
 | 00040  00 00 00 00                                       ....             |
mmap(NULL, 2037344, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1edde66000
mmap(0x7f1edde88000, 1540096, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7f1edde88000
mmap(0x7f1ede000000, 319488, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x19a000) = 0x7f1ede000000
mmap(0x7f1ede04e000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f1ede04e000
mmap(0x7f1ede054000, 13920, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f1ede054000
close(3)                                = 0
arch_prctl(ARCH_SET_FS, 0x7f1ede059540) = 0
mprotect(0x7f1ede04e000, 16384, PROT_READ) = 0
mprotect(0x55eda4c16000, 4096, PROT_READ) = 0
mprotect(0x7f1ede09a000, 4096, PROT_READ) = 0
munmap(0x7f1ede05a000, 73887)           = 0
openat(AT_FDCWD, "/new_a.out", O_WRONLY|O_CREAT, 0600) = -1 EACCES (Permission denied)
openat(AT_FDCWD, "a.out", O_RDONLY)     = 3
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x3), ...}) = 0
brk(NULL)                               = 0x55eda4dca000
brk(0x55eda4deb000)                     = 0x55eda4deb000
write(1, "copy failed\n", 12copy failed
)           = 12
exit_group(0)                           = ?
+++ exited with 0 +++

tiansong@tiansong:~/Desktop$ strace -e read=3 -e trace=file,read,close ./fcopy.out  /new_a.out
 a.out 
execve("./fcopy.out", ["./fcopy.out", "/new_a.out", "a.out"], 0x7fff0de15440 /* 41 vars */) = 0
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
close(3)                                = 0
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\300A\2\0\0\0\0\0"..., 832) = 832
 | 00000  7f 45 4c 46 02 01 01 03  00 00 00 00 00 00 00 00  .ELF............ |
 | 00010  03 00 3e 00 01 00 00 00  c0 41 02 00 00 00 00 00  ..>......A...... |
 | 00020  40 00 00 00 00 00 00 00  18 e7 1e 00 00 00 00 00  @............... |
 | 00030  00 00 00 00 40 00 38 00  0e 00 40 00 44 00 43 00  ....@.8...@.D.C. |
 | 00040  06 00 00 00 04 00 00 00  40 00 00 00 00 00 00 00  ........@....... |
 | 00050  40 00 00 00 00 00 00 00  40 00 00 00 00 00 00 00  @.......@....... |
 | 00060  10 03 00 00 00 00 00 00  10 03 00 00 00 00 00 00  ................ |
 | 00070  08 00 00 00 00 00 00 00  03 00 00 00 04 00 00 00  ................ |
 | 00080  a0 e6 1b 00 00 00 00 00  a0 e6 1b 00 00 00 00 00  ................ |
 | 00090  a0 e6 1b 00 00 00 00 00  1c 00 00 00 00 00 00 00  ................ |
 | 000a0  1c 00 00 00 00 00 00 00  10 00 00 00 00 00 00 00  ................ |
 | 000b0  01 00 00 00 04 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 000c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 000d0  e8 14 02 00 00 00 00 00  e8 14 02 00 00 00 00 00  ................ |
 | 000e0  00 10 00 00 00 00 00 00  01 00 00 00 05 00 00 00  ................ |
 | 000f0  00 20 02 00 00 00 00 00  00 20 02 00 00 00 00 00  . ....... ...... |
 | 00100  00 20 02 00 00 00 00 00  24 76 17 00 00 00 00 00  . ......$v...... |
 | 00110  24 76 17 00 00 00 00 00  00 10 00 00 00 00 00 00  $v.............. |
 | 00120  01 00 00 00 04 00 00 00  00 a0 19 00 00 00 00 00  ................ |
 | 00130  00 a0 19 00 00 00 00 00  00 a0 19 00 00 00 00 00  ................ |
 | 00140  c4 d2 04 00 00 00 00 00  c4 d2 04 00 00 00 00 00  ................ |
 | 00150  00 10 00 00 00 00 00 00  01 00 00 00 06 00 00 00  ................ |
 | 00160  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00170  88 87 1e 00 00 00 00 00  18 50 00 00 00 00 00 00  .........P...... |
 | 00180  d8 8e 00 00 00 00 00 00  00 10 00 00 00 00 00 00  ................ |
 | 00190  02 00 00 00 06 00 00 00  80 ab 1e 00 00 00 00 00  ................ |
 | 001a0  80 bb 1e 00 00 00 00 00  80 bb 1e 00 00 00 00 00  ................ |
 | 001b0  e0 01 00 00 00 00 00 00  e0 01 00 00 00 00 00 00  ................ |
 | 001c0  08 00 00 00 00 00 00 00  04 00 00 00 04 00 00 00  ................ |
 | 001d0  50 03 00 00 00 00 00 00  50 03 00 00 00 00 00 00  P.......P....... |
 | 001e0  50 03 00 00 00 00 00 00  20 00 00 00 00 00 00 00  P....... ....... |
 | 001f0  20 00 00 00 00 00 00 00  08 00 00 00 00 00 00 00   ............... |
 | 00200  04 00 00 00 04 00 00 00  70 03 00 00 00 00 00 00  ........p....... |
 | 00210  70 03 00 00 00 00 00 00  70 03 00 00 00 00 00 00  p.......p....... |
 | 00220  44 00 00 00 00 00 00 00  44 00 00 00 00 00 00 00  D.......D....... |
 | 00230  04 00 00 00 00 00 00 00  07 00 00 00 04 00 00 00  ................ |
 | 00240  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00250  88 87 1e 00 00 00 00 00  10 00 00 00 00 00 00 00  ................ |
 | 00260  90 00 00 00 00 00 00 00  08 00 00 00 00 00 00 00  ................ |
 | 00270  53 e5 74 64 04 00 00 00  50 03 00 00 00 00 00 00  S.td....P....... |
 | 00280  50 03 00 00 00 00 00 00  50 03 00 00 00 00 00 00  P.......P....... |
 | 00290  20 00 00 00 00 00 00 00  20 00 00 00 00 00 00 00   ....... ....... |
 | 002a0  08 00 00 00 00 00 00 00  50 e5 74 64 04 00 00 00  ........P.td.... |
 | 002b0  bc e6 1b 00 00 00 00 00  bc e6 1b 00 00 00 00 00  ................ |
 | 002c0  bc e6 1b 00 00 00 00 00  d4 5e 00 00 00 00 00 00  .........^...... |
 | 002d0  d4 5e 00 00 00 00 00 00  04 00 00 00 00 00 00 00  .^.............. |
 | 002e0  51 e5 74 64 06 00 00 00  00 00 00 00 00 00 00 00  Q.td............ |
 | 002f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 00300  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  ................ |
 | 00310  10 00 00 00 00 00 00 00  52 e5 74 64 04 00 00 00  ........R.td.... |
 | 00320  88 77 1e 00 00 00 00 00  88 87 1e 00 00 00 00 00  .w.............. |
 | 00330  88 87 1e 00 00 00 00 00  78 38 00 00 00 00 00 00  ........x8...... |
close(3)                                = 0
openat(AT_FDCWD, "/new_a.out", O_WRONLY|O_CREAT, 0600) = -1 EACCES (Permission denied)
openat(AT_FDCWD, "a.out", O_RDONLY)     = 3
copy failed
+++ exited with 0 +++

tiansong@tiansong:~/Desktop$ strace -e trace=write ./fcopy.out ./new_a.out a.out 
write(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0`\20\0\0\0\0\0\0"..., 512) = 512
write(3, "\4\0\0\0\4\0\0\0X\3\0\0\0\0\0\0X\3\0\0\0\0\0\0X\3\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\37\0\0\0\22\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\363\17\36\372H\203\354\10H\213\5\331/\0\0H\205\300t\2\377\320H\203\304\10\303\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\1\0\2\0Hello World!\0\0\0\0\1\33\3;@\0\0\0\7\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\270=\0\0\0\0\0\0\33\0\0\0\0\0\0\0\10\0\0\0\0\0\0\0\32\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\10@\0\0\0\0\0\0GCC: (Ubuntu 9.4"..., 512) = 512
write(3, "\0\0\0\0\0\0\0\0\0\0\0\0\3\0\23\0\24 \0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\255\0\0\0\0\0\25\0\300=\0\0\0\0\0\0\0\0\0\0\0\0\0\0\276\0\0\0\1\0\27\0"..., 512) = 512
write(3, "I\21\0\0\0\0\0\0\33\0\0\0\0\0\0\0\300\1\0\0\21\2\31\0\20@\0\0\0\0\0\0"..., 512) = 512
write(3, "u_init\0__bss_start\0main\0__TMC_EN"..., 512) = 512
write(3, "\2\0\0\0\0\0\0\08\3\0\0\0\0\0\08\3\0\0\0\0\0\0 \0\0\0\0\0\0\0"..., 512) = 512
write(3, "\2\0\0\0\0\0\0\0 \5\0\0\0\0\0\0 \5\0\0\0\0\0\0\300\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\2\0\0\0\0\0\0\0\0 \0\0\0\0\0\0\0 \0\0\0\0\0\0\21\0\0\0\0\0\0\0"..., 512) = 512
write(3, "\3\0\0\0\0\0\0\0\20@\0\0\0\0\0\0\0200\0\0\0\0\0\0\10\0\0\0\0\0\0\0"..., 312) = 312
write(1, "copy completed\n", 15copy completed
)        = 15
+++ exited with 0 +++

《Linux系统编程训练营》0-2_深入理解系统调用

揭示系统 API 的奥秘

Linux 系统架构

模式切换的本质（系统调用的本质）

系统调用的真面目

系统调用和系统 API 实现示例

编程实验：系统调用的本质

值得思考的问题

相同功能的代码实现

strace - 系统调用探测器

strace 程序性能分析

strace - 用法详解

编程实验：strace 程序逆向分析

编程实验：应用程序错误定位

编程实验：strace 程序数据分析

TianSong

引用和评论

《Linux系统编程训练营》1-2_多核调度预备知识

记录一次Linux下安装Oracle数据库的过程

在 ubuntu24.04 上使用英伟达显卡——安装驱动和cuda

linux下使用笔记本的相关设置

张晋涛：KubeCon China 2024 回顾

docker 使用--storage-opt参数约束容器文件系统大小

精简实用！一分钟搭建文件管理服务！