调用过程：
用户空间->内核空间
INT 0x80（封装在C库函数中） -->system_call（系统调用处理程序）-->系统调用服务例程 -->内核程序
系统调用时通过软中断指令INT 0x80实现的，这条指令会让系统跳转到一个预先设置好的内核地址，指向系统调用处理程序system_call。
系统调用服务例程是对一个具体的系统调用的内核实现函数。执行任何系统调用，都需要先调用C库中的函数，触发INT 0x80中断，跳转到系统调用处理程序，从而通过系统调用号查找系统调用表sys_call_table[__NR_syscall_max+1]。主要可以看
<unistd_32.h>
#ifndef _ASM_X86_UNISTD_32_H
#define _ASM_X86_UNISTD_32_H
/*
* This file contains the system call numbers.
*/
#define __NR_restart_syscall 0
#define __NR_exit 1
#define __NR_fork 2
#define __NR_read 3
#define __NR_write 4
#define __NR_open 5
#define __NR_close 6
#define __NR_waitpid 7
#define __NR_creat 8
#define __NR_link 9
#define __NR_unlink 10
#define __NR_execve 11
#define __NR_chdir 12
#define __NR_time 13
#define __NR_mknod 14
#define __NR_chmod 15
#define __NR_lchown 16
#define __NR_break 17
#define __NR_oldstat 18
#define __NR_lseek 19
#define __NR_getpid 20
#define __NR_mount 21
#define __NR_umount 22
#define __NR_setuid 23
#define __NR_getuid 24
#define __NR_stime 25
#define __NR_ptrace 26
#define __NR_alarm 27
#define __NR_oldfstat 28
#define __NR_pause 29
#define __NR_utime 30
#define __NR_stty 31
#define __NR_gtty 32
#define __NR_access 33
#define __NR_nice 34
#define __NR_ftime 35
#define __NR_sync 36
#define __NR_kill 37
#define __NR_rename 38
#define __NR_mkdir 39
#define __NR_rmdir 40
#define __NR_dup 41
#define __NR_pipe 42
#define __NR_times 43
#define __NR_prof 44
#define __NR_brk 45
#define __NR_setgid 46
#define __NR_getgid 47
#define __NR_signal 48
#define __NR_geteuid 49
#define __NR_getegid 50
#define __NR_acct 51
#define __NR_umount2 52
#define __NR_lock 53
#define __NR_ioctl 54
#define __NR_fcntl 55
#define __NR_mpx 56
#define __NR_setpgid 57
#define __NR_ulimit 58
#define __NR_oldolduname 59
#define __NR_umask 60
#define __NR_chroot 61
#define __NR_ustat 62
#define __NR_dup2 63
#define __NR_getppid 64
#define __NR_getpgrp 65
#define __NR_setsid 66
#define __NR_sigaction 67
#define __NR_sgetmask 68
#define __NR_ssetmask 69
#define __NR_setreuid 70
#define __NR_setregid 71
#define __NR_sigsuspend 72
#define __NR_sigpending 73
#define __NR_sethostname 74
#define __NR_setrlimit 75
#define __NR_getrlimit 76 /* Back compatible 2Gig limited rlimit */
#define __NR_getrusage 77
#define __NR_gettimeofday 78
#define __NR_settimeofday 79
#define __NR_getgroups 80
#define __NR_setgroups 81
#define __NR_select 82
#define __NR_symlink 83
#define __NR_oldlstat 84
#define __NR_readlink 85
#define __NR_uselib 86
#define __NR_swapon 87
#define __NR_reboot 88
#define __NR_readdir 89
#define __NR_mmap 90
#define __NR_munmap 91
#define __NR_truncate 92
#define __NR_ftruncate 93
#define __NR_fchmod 94
#define __NR_fchown 95
#define __NR_getpriority 96
#define __NR_setpriority 97
#define __NR_profil 98
#define __NR_statfs 99
#define __NR_fstatfs 100
#define __NR_ioperm 101
#define __NR_socketcall 102
#define __NR_syslog 103
#define __NR_setitimer 104
#define __NR_getitimer 105
#define __NR_stat 106
#define __NR_lstat 107
#define __NR_fstat 108
#define __NR_olduname 109
#define __NR_iopl 110
#define __NR_vhangup 111
#define __NR_idle 112
#define __NR_vm86old 113
#define __NR_wait4 114
#define __NR_swapoff 115
#define __NR_sysinfo 116
#define __NR_ipc 117
#define __NR_fsync 118
#define __NR_sigreturn 119
#define __NR_clone 120
#define __NR_setdomainname 121
#define __NR_uname 122
#define __NR_modify_ldt 123
#define __NR_adjtimex 124
#define __NR_mprotect 125
#define __NR_sigprocmask 126
#define __NR_create_module 127
#define __NR_init_module 128
#define __NR_delete_module 129
#define __NR_get_kernel_syms 130
#define __NR_quotactl 131
#define __NR_getpgid 132
#define __NR_fchdir 133
#define __NR_bdflush 134
#define __NR_sysfs 135
#define __NR_personality 136
#define __NR_afs_syscall 137 /* Syscall for Andrew File System */
#define __NR_setfsuid 138
#define __NR_setfsgid 139
#define __NR__llseek 140
#define __NR_getdents 141
#define __NR__newselect 142
#define __NR_flock 143
#define __NR_msync 144
#define __NR_readv 145
#define __NR_writev 146
#define __NR_getsid 147
#define __NR_fdatasync 148
#define __NR__sysctl 149
#define __NR_mlock 150
#define __NR_munlock 151
#define __NR_mlockall 152
#define __NR_munlockall 153
#define __NR_sched_setparam 154
#define __NR_sched_getparam 155
#define __NR_sched_setscheduler 156
#define __NR_sched_getscheduler 157
#define __NR_sched_yield 158
#define __NR_sched_get_priority_max 159
#define __NR_sched_get_priority_min 160
#define __NR_sched_rr_get_interval 161
#define __NR_nanosleep 162
#define __NR_mremap 163
#define __NR_setresuid 164
#define __NR_getresuid 165
#define __NR_vm86 166
#define __NR_query_module 167
#define __NR_poll 168
#define __NR_nfsservctl 169
#define __NR_setresgid 170
#define __NR_getresgid 171
#define __NR_prctl 172
#define __NR_rt_sigreturn 173
#define __NR_rt_sigaction 174
#define __NR_rt_sigprocmask 175
#define __NR_rt_sigpending 176
#define __NR_rt_sigtimedwait 177
#define __NR_rt_sigqueueinfo 178
#define __NR_rt_sigsuspend 179
#define __NR_pread64 180
#define __NR_pwrite64 181
#define __NR_chown 182
#define __NR_getcwd 183
#define __NR_capget 184
#define __NR_capset 185
#define __NR_sigaltstack 186
#define __NR_sendfile 187
#define __NR_getpmsg 188 /* some people actually want streams */
#define __NR_putpmsg 189 /* some people actually want streams */
#define __NR_vfork 190
#define __NR_ugetrlimit 191 /* SuS compliant getrlimit */
#define __NR_mmap2 192
#define __NR_truncate64 193
#define __NR_ftruncate64 194
#define __NR_stat64 195
#define __NR_lstat64 196
#define __NR_fstat64 197
#define __NR_lchown32 198
#define __NR_getuid32 199
#define __NR_getgid32 200
#define __NR_geteuid32 201
#define __NR_getegid32 202
#define __NR_setreuid32 203
#define __NR_setregid32 204
#define __NR_getgroups32 205
#define __NR_setgroups32 206
#define __NR_fchown32 207
#define __NR_setresuid32 208
#define __NR_getresuid32 209
#define __NR_setresgid32 210
#define __NR_getresgid32 211
#define __NR_chown32 212
#define __NR_setuid32 213
#define __NR_setgid32 214
#define __NR_setfsuid32 215
#define __NR_setfsgid32 216
#define __NR_pivot_root 217
#define __NR_mincore 218
#define __NR_madvise 219
#define __NR_madvise1 219 /* delete when C lib stub is removed */
#define __NR_getdents64 220
#define __NR_fcntl64 221
/* 223 is unused */
#define __NR_gettid 224
#define __NR_readahead 225
#define __NR_setxattr 226
#define __NR_lsetxattr 227
#define __NR_fsetxattr 228
#define __NR_getxattr 229
#define __NR_lgetxattr 230
#define __NR_fgetxattr 231
#define __NR_listxattr 232
#define __NR_llistxattr 233
#define __NR_flistxattr 234
#define __NR_removexattr 235
#define __NR_lremovexattr 236
#define __NR_fremovexattr 237
#define __NR_tkill 238
#define __NR_sendfile64 239
#define __NR_futex 240
#define __NR_sched_setaffinity 241
#define __NR_sched_getaffinity 242
#define __NR_set_thread_area 243
#define __NR_get_thread_area 244
#define __NR_io_setup 245
#define __NR_io_destroy 246
#define __NR_io_getevents 247
#define __NR_io_submit 248
#define __NR_io_cancel 249
#define __NR_fadvise64 250
/* 251 is available for reuse (was briefly sys_set_zone_reclaim) */
#define __NR_exit_group 252
#define __NR_lookup_dcookie 253
#define __NR_epoll_create 254
#define __NR_epoll_ctl 255
#define __NR_epoll_wait 256
#define __NR_remap_file_pages 257
#define __NR_set_tid_address 258
#define __NR_timer_create 259
#define __NR_timer_settime (__NR_timer_create+1)
#define __NR_timer_gettime (__NR_timer_create+2)
#define __NR_timer_getoverrun (__NR_timer_create+3)
#define __NR_timer_delete (__NR_timer_create+4)
#define __NR_clock_settime (__NR_timer_create+5)
#define __NR_clock_gettime (__NR_timer_create+6)
#define __NR_clock_getres (__NR_timer_create+7)
#define __NR_clock_nanosleep (__NR_timer_create+8)
#define __NR_statfs64 268
#define __NR_fstatfs64 269
#define __NR_tgkill 270
#define __NR_utimes 271
#define __NR_fadvise64_64 272
#define __NR_vserver 273
#define __NR_mbind 274
#define __NR_get_mempolicy 275
#define __NR_set_mempolicy 276
#define __NR_mq_open 277
#define __NR_mq_unlink (__NR_mq_open+1)
#define __NR_mq_timedsend (__NR_mq_open+2)
#define __NR_mq_timedreceive (__NR_mq_open+3)
#define __NR_mq_notify (__NR_mq_open+4)
#define __NR_mq_getsetattr (__NR_mq_open+5)
#define __NR_kexec_load 283
#define __NR_waitid 284
/* #define __NR_sys_setaltroot 285 */
#define __NR_add_key 286
#define __NR_request_key 287
#define __NR_keyctl 288
#define __NR_ioprio_set 289
#define __NR_ioprio_get 290
#define __NR_inotify_init 291
#define __NR_inotify_add_watch 292
#define __NR_inotify_rm_watch 293
#define __NR_migrate_pages 294
#define __NR_openat 295
#define __NR_mkdirat 296
#define __NR_mknodat 297
#define __NR_fchownat 298
#define __NR_futimesat 299
#define __NR_fstatat64 300
#define __NR_unlinkat 301
#define __NR_renameat 302
#define __NR_linkat 303
#define __NR_symlinkat 304
#define __NR_readlinkat 305
#define __NR_fchmodat 306
#define __NR_faccessat 307
#define __NR_pselect6 308
#define __NR_ppoll 309
#define __NR_unshare 310
#define __NR_set_robust_list 311
#define __NR_get_robust_list 312
#define __NR_splice 313
#define __NR_sync_file_range 314
#define __NR_tee 315
#define __NR_vmsplice 316
#define __NR_move_pages 317
#define __NR_getcpu 318
#define __NR_epoll_pwait 319
#define __NR_utimensat 320
#define __NR_signalfd 321
#define __NR_timerfd_create 322
#define __NR_eventfd 323
#define __NR_fallocate 324
#define __NR_timerfd_settime 325
#define __NR_timerfd_gettime 326
#define __NR_signalfd4 327
#define __NR_eventfd2 328
#define __NR_epoll_create1 329
#define __NR_dup3 330
#define __NR_pipe2 331
#define __NR_inotify_init1 332
#define __NR_preadv 333
#define __NR_pwritev 334
#define __NR_rt_tgsigqueueinfo 335
#define __NR_perf_event_open 336
#define __NR_recvmmsg 337
#ifdef __KERNEL__
#define NR_syscalls 338
#define __ARCH_WANT_IPC_PARSE_VERSION
#define __ARCH_WANT_OLD_READDIR
#define __ARCH_WANT_OLD_STAT
#define __ARCH_WANT_STAT64
#define __ARCH_WANT_SYS_ALARM
#define __ARCH_WANT_SYS_GETHOSTNAME
#define __ARCH_WANT_SYS_IPC
#define __ARCH_WANT_SYS_PAUSE
#define __ARCH_WANT_SYS_SGETMASK
#define __ARCH_WANT_SYS_SIGNAL
#define __ARCH_WANT_SYS_TIME
#define __ARCH_WANT_SYS_UTIME
#define __ARCH_WANT_SYS_WAITPID
#define __ARCH_WANT_SYS_SOCKETCALL
#define __ARCH_WANT_SYS_FADVISE64
#define __ARCH_WANT_SYS_GETPGRP
#define __ARCH_WANT_SYS_LLSEEK
#define __ARCH_WANT_SYS_NICE
#define __ARCH_WANT_SYS_OLD_GETRLIMIT
#define __ARCH_WANT_SYS_OLD_UNAME
#define __ARCH_WANT_SYS_OLD_MMAP
#define __ARCH_WANT_SYS_OLD_SELECT
#define __ARCH_WANT_SYS_OLDUMOUNT
#define __ARCH_WANT_SYS_SIGPENDING
#define __ARCH_WANT_SYS_SIGPROCMASK
#define __ARCH_WANT_SYS_RT_SIGACTION
#define __ARCH_WANT_SYS_RT_SIGSUSPEND
/*
* "Conditional" syscalls
*
* What we want is __attribute__((weak,alias("sys_ni_syscall"))),
* but it doesn't work on all toolchains, so we just do it by hand
*/
#ifndef cond_syscall
#define cond_syscall(x) asm(".weak " #x "
.set " #x ",sys_ni_syscall")
#endif
#endif /* __KERNEL__ */
#endif /* _ASM_X86_UNISTD_32_H */
<unistd_64.h>
#define __NR_read 0
__SYSCALL(__NR_read, sys_read)
#define __NR_write 1
__SYSCALL(__NR_write, sys_write)
#define __NR_open 2
__SYSCALL(__NR_open, sys_open)
#define __NR_close 3
__SYSCALL(__NR_close, sys_close)
#define __NR_stat 4
__SYSCALL(__NR_stat, sys_newstat)
#define __NR_fstat 5
__SYSCALL(__NR_fstat, sys_newfstat)
#define __NR_lstat 6
__SYSCALL(__NR_lstat, sys_newlstat)
#define __NR_poll 7
__SYSCALL(__NR_poll, sys_poll)
#define __NR_lseek 8
__SYSCALL(__NR_lseek, sys_lseek)
#define __NR_mmap 9
__SYSCALL(__NR_mmap, sys_mmap)
#define __NR_mprotect 10
__SYSCALL(__NR_mprotect, sys_mprotect)
#define __NR_munmap 11
__SYSCALL(__NR_munmap, sys_munmap)
#define __NR_brk 12
__SYSCALL(__NR_brk, sys_brk)
#define __NR_rt_sigaction 13
__SYSCALL(__NR_rt_sigaction, sys_rt_sigaction)
#define __NR_rt_sigprocmask 14
__SYSCALL(__NR_rt_sigprocmask, sys_rt_sigprocmask)
#define __NR_rt_sigreturn 15
__SYSCALL(__NR_rt_sigreturn, stub_rt_sigreturn)
#define __NR_ioctl 16
__SYSCALL(__NR_ioctl, sys_ioctl)
#define __NR_pread64 17
__SYSCALL(__NR_pread64, sys_pread64)
#define __NR_pwrite64 18
__SYSCALL(__NR_pwrite64, sys_pwrite64)
#define __NR_readv 19
__SYSCALL(__NR_readv, sys_readv)
#define __NR_writev 20
__SYSCALL(__NR_writev, sys_writev)
#define __NR_access 21
__SYSCALL(__NR_access, sys_access)
#define __NR_pipe 22
__SYSCALL(__NR_pipe, sys_pipe)
#define __NR_select 23
__SYSCALL(__NR_select, sys_select)
#define __NR_sched_yield 24
__SYSCALL(__NR_sched_yield, sys_sched_yield)
#define __NR_mremap 25
__SYSCALL(__NR_mremap, sys_mremap)
#define __NR_msync 26
__SYSCALL(__NR_msync, sys_msync)
#define __NR_mincore 27
__SYSCALL(__NR_mincore, sys_mincore)
#define __NR_madvise 28
__SYSCALL(__NR_madvise, sys_madvise)
#define __NR_shmget 29
__SYSCALL(__NR_shmget, sys_shmget)
#define __NR_shmat 30
__SYSCALL(__NR_shmat, sys_shmat)
#define __NR_shmctl 31
__SYSCALL(__NR_shmctl, sys_shmctl)
#define __NR_dup 32
__SYSCALL(__NR_dup, sys_dup)
#define __NR_dup2 33
__SYSCALL(__NR_dup2, sys_dup2)
#define __NR_pause 34
__SYSCALL(__NR_pause, sys_pause)
#define __NR_nanosleep 35
__SYSCALL(__NR_nanosleep, sys_nanosleep)
#define __NR_getitimer 36
__SYSCALL(__NR_getitimer, sys_getitimer)
#define __NR_alarm 37
__SYSCALL(__NR_alarm, sys_alarm)
#define __NR_setitimer 38
__SYSCALL(__NR_setitimer, sys_setitimer)
#define __NR_getpid 39
__SYSCALL(__NR_getpid, sys_getpid)
#define __NR_sendfile 40
__SYSCALL(__NR_sendfile, sys_sendfile64)
#define __NR_socket 41
__SYSCALL(__NR_socket, sys_socket)
#define __NR_connect 42
__SYSCALL(__NR_connect, sys_connect)
#define __NR_accept 43
__SYSCALL(__NR_accept, sys_accept)
#define __NR_sendto 44
__SYSCALL(__NR_sendto, sys_sendto)
#define __NR_recvfrom 45
__SYSCALL(__NR_recvfrom, sys_recvfrom)
#define __NR_sendmsg 46
__SYSCALL(__NR_sendmsg, sys_sendmsg)
#define __NR_recvmsg 47
__SYSCALL(__NR_recvmsg, sys_recvmsg)
#define __NR_shutdown 48
__SYSCALL(__NR_shutdown, sys_shutdown)
#define __NR_bind 49
__SYSCALL(__NR_bind, sys_bind)
#define __NR_listen 50
__SYSCALL(__NR_listen, sys_listen)
#define __NR_getsockname 51
__SYSCALL(__NR_getsockname, sys_getsockname)
#define __NR_getpeername 52
__SYSCALL(__NR_getpeername, sys_getpeername)
#define __NR_socketpair 53
__SYSCALL(__NR_socketpair, sys_socketpair)
#define __NR_setsockopt 54
__SYSCALL(__NR_setsockopt, sys_setsockopt)
#define __NR_getsockopt 55
__SYSCALL(__NR_getsockopt, sys_getsockopt)
#define __NR_clone 56
__SYSCALL(__NR_clone, stub_clone)
#define __NR_fork 57
__SYSCALL(__NR_fork, stub_fork)
#define __NR_vfork 58
__SYSCALL(__NR_vfork, stub_vfork)
#define __NR_execve 59
__SYSCALL(__NR_execve, stub_execve)
#define __NR_exit 60
__SYSCALL(__NR_exit, sys_exit)
#define __NR_wait4 61
__SYSCALL(__NR_wait4, sys_wait4)
#define __NR_kill 62
__SYSCALL(__NR_kill, sys_kill)
#define __NR_uname 63
__SYSCALL(__NR_uname, sys_newuname)
#define __NR_semget 64
__SYSCALL(__NR_semget, sys_semget)
#define __NR_semop 65
__SYSCALL(__NR_semop, sys_semop)
#define __NR_semctl 66
__SYSCALL(__NR_semctl, sys_semctl)
#define __NR_shmdt 67
__SYSCALL(__NR_shmdt, sys_shmdt)
#define __NR_msgget 68
__SYSCALL(__NR_msgget, sys_msgget)
#define __NR_msgsnd 69
__SYSCALL(__NR_msgsnd, sys_msgsnd)
#define __NR_msgrcv 70
__SYSCALL(__NR_msgrcv, sys_msgrcv)
#define __NR_msgctl 71
__SYSCALL(__NR_msgctl, sys_msgctl)
#define __NR_fcntl 72
__SYSCALL(__NR_fcntl, sys_fcntl)
#define __NR_flock 73
__SYSCALL(__NR_flock, sys_flock)
#define __NR_fsync 74
__SYSCALL(__NR_fsync, sys_fsync)
#define __NR_fdatasync 75
__SYSCALL(__NR_fdatasync, sys_fdatasync)
#define __NR_truncate 76
__SYSCALL(__NR_truncate, sys_truncate)
#define __NR_ftruncate 77
__SYSCALL(__NR_ftruncate, sys_ftruncate)
#define __NR_getdents 78
__SYSCALL(__NR_getdents, sys_getdents)
#define __NR_getcwd 79
__SYSCALL(__NR_getcwd, sys_getcwd)
#define __NR_chdir 80
__SYSCALL(__NR_chdir, sys_chdir)
#define __NR_fchdir 81
__SYSCALL(__NR_fchdir, sys_fchdir)
#define __NR_rename 82
__SYSCALL(__NR_rename, sys_rename)
#define __NR_mkdir 83
__SYSCALL(__NR_mkdir, sys_mkdir)
#define __NR_rmdir 84
__SYSCALL(__NR_rmdir, sys_rmdir)
#define __NR_creat 85
__SYSCALL(__NR_creat, sys_creat)
#define __NR_link 86
__SYSCALL(__NR_link, sys_link)
#define __NR_unlink 87
__SYSCALL(__NR_unlink, sys_unlink)
#define __NR_symlink 88
__SYSCALL(__NR_symlink, sys_symlink)
#define __NR_readlink 89
__SYSCALL(__NR_readlink, sys_readlink)
#define __NR_chmod 90
__SYSCALL(__NR_chmod, sys_chmod)
#define __NR_fchmod 91
__SYSCALL(__NR_fchmod, sys_fchmod)
#define __NR_chown 92
__SYSCALL(__NR_chown, sys_chown)
#define __NR_fchown 93
__SYSCALL(__NR_fchown, sys_fchown)
#define __NR_lchown 94
__SYSCALL(__NR_lchown, sys_lchown)
#define __NR_umask 95
__SYSCALL(__NR_umask, sys_umask)
#define __NR_gettimeofday 96
__SYSCALL(__NR_gettimeofday, sys_gettimeofday)
#define __NR_getrlimit 97
__SYSCALL(__NR_getrlimit, sys_getrlimit)
#define __NR_getrusage 98
__SYSCALL(__NR_getrusage, sys_getrusage)
#define __NR_sysinfo 99
__SYSCALL(__NR_sysinfo, sys_sysinfo)
#define __NR_times 100
__SYSCALL(__NR_times, sys_times)
#define __NR_ptrace 101
__SYSCALL(__NR_ptrace, sys_ptrace)
#define __NR_getuid 102
__SYSCALL(__NR_getuid, sys_getuid)
#define __NR_syslog 103
__SYSCALL(__NR_syslog, sys_syslog)
/* at the very end the stuff that never runs during the benchmarks */
#define __NR_getgid 104
__SYSCALL(__NR_getgid, sys_getgid)
#define __NR_setuid 105
__SYSCALL(__NR_setuid, sys_setuid)
#define __NR_setgid 106
__SYSCALL(__NR_setgid, sys_setgid)
#define __NR_geteuid 107
__SYSCALL(__NR_geteuid, sys_geteuid)
#define __NR_getegid 108
__SYSCALL(__NR_getegid, sys_getegid)
#define __NR_setpgid 109
__SYSCALL(__NR_setpgid, sys_setpgid)
#define __NR_getppid 110
__SYSCALL(__NR_getppid, sys_getppid)
#define __NR_getpgrp 111
__SYSCALL(__NR_getpgrp, sys_getpgrp)
#define __NR_setsid 112
__SYSCALL(__NR_setsid, sys_setsid)
#define __NR_setreuid 113
__SYSCALL(__NR_setreuid, sys_setreuid)
#define __NR_setregid 114
__SYSCALL(__NR_setregid, sys_setregid)
#define __NR_getgroups 115
__SYSCALL(__NR_getgroups, sys_getgroups)
#define __NR_setgroups 116
__SYSCALL(__NR_setgroups, sys_setgroups)
#define __NR_setresuid 117
__SYSCALL(__NR_setresuid, sys_setresuid)
#define __NR_getresuid 118
__SYSCALL(__NR_getresuid, sys_getresuid)
#define __NR_setresgid 119
__SYSCALL(__NR_setresgid, sys_setresgid)
#define __NR_getresgid 120
__SYSCALL(__NR_getresgid, sys_getresgid)
#define __NR_getpgid 121
__SYSCALL(__NR_getpgid, sys_getpgid)
#define __NR_setfsuid 122
__SYSCALL(__NR_setfsuid, sys_setfsuid)
#define __NR_setfsgid 123
__SYSCALL(__NR_setfsgid, sys_setfsgid)
#define __NR_getsid 124
__SYSCALL(__NR_getsid, sys_getsid)
#define __NR_capget 125
__SYSCALL(__NR_capget, sys_capget)
#define __NR_capset 126
__SYSCALL(__NR_capset, sys_capset)
#define __NR_rt_sigpending 127
__SYSCALL(__NR_rt_sigpending, sys_rt_sigpending)
#define __NR_rt_sigtimedwait 128
__SYSCALL(__NR_rt_sigtimedwait, sys_rt_sigtimedwait)
#define __NR_rt_sigqueueinfo 129
__SYSCALL(__NR_rt_sigqueueinfo, sys_rt_sigqueueinfo)
#define __NR_rt_sigsuspend 130
__SYSCALL(__NR_rt_sigsuspend, sys_rt_sigsuspend)
#define __NR_sigaltstack 131
__SYSCALL(__NR_sigaltstack, stub_sigaltstack)
#define __NR_utime 132
__SYSCALL(__NR_utime, sys_utime)
#define __NR_mknod 133
__SYSCALL(__NR_mknod, sys_mknod)
/* Only needed for a.out */
#define __NR_uselib 134
__SYSCALL(__NR_uselib, sys_ni_syscall)
#define __NR_personality 135
__SYSCALL(__NR_personality, sys_personality)
#define __NR_ustat 136
__SYSCALL(__NR_ustat, sys_ustat)
#define __NR_statfs 137
__SYSCALL(__NR_statfs, sys_statfs)
#define __NR_fstatfs 138
__SYSCALL(__NR_fstatfs, sys_fstatfs)
#define __NR_sysfs 139
__SYSCALL(__NR_sysfs, sys_sysfs)
#define __NR_getpriority 140
__SYSCALL(__NR_getpriority, sys_getpriority)
#define __NR_setpriority 141
__SYSCALL(__NR_setpriority, sys_setpriority)
#define __NR_sched_setparam 142
__SYSCALL(__NR_sched_setparam, sys_sched_setparam)
#define __NR_sched_getparam 143
__SYSCALL(__NR_sched_getparam, sys_sched_getparam)
#define __NR_sched_setscheduler 144
__SYSCALL(__NR_sched_setscheduler, sys_sched_setscheduler)
#define __NR_sched_getscheduler 145
__SYSCALL(__NR_sched_getscheduler, sys_sched_getscheduler)
#define __NR_sched_get_priority_max 146
__SYSCALL(__NR_sched_get_priority_max, sys_sched_get_priority_max)
#define __NR_sched_get_priority_min 147
__SYSCALL(__NR_sched_get_priority_min, sys_sched_get_priority_min)
#define __NR_sched_rr_get_interval 148
__SYSCALL(__NR_sched_rr_get_interval, sys_sched_rr_get_interval)
#define __NR_mlock 149
__SYSCALL(__NR_mlock, sys_mlock)
#define __NR_munlock 150
__SYSCALL(__NR_munlock, sys_munlock)
#define __NR_mlockall 151
__SYSCALL(__NR_mlockall, sys_mlockall)
#define __NR_munlockall 152
__SYSCALL(__NR_munlockall, sys_munlockall)
#define __NR_vhangup 153
__SYSCALL(__NR_vhangup, sys_vhangup)
#define __NR_modify_ldt 154
__SYSCALL(__NR_modify_ldt, sys_modify_ldt)
#define __NR_pivot_root 155
__SYSCALL(__NR_pivot_root, sys_pivot_root)
#define __NR__sysctl 156
__SYSCALL(__NR__sysctl, sys_sysctl)
#define __NR_prctl 157
__SYSCALL(__NR_prctl, sys_prctl)
#define __NR_arch_prctl 158
__SYSCALL(__NR_arch_prctl, sys_arch_prctl)
#define __NR_adjtimex 159
__SYSCALL(__NR_adjtimex, sys_adjtimex)
#define __NR_setrlimit 160
__SYSCALL(__NR_setrlimit, sys_setrlimit)
#define __NR_chroot 161
__SYSCALL(__NR_chroot, sys_chroot)
#define __NR_sync 162
__SYSCALL(__NR_sync, sys_sync)
#define __NR_acct 163
__SYSCALL(__NR_acct, sys_acct)
#define __NR_settimeofday 164
__SYSCALL(__NR_settimeofday, sys_settimeofday)
#define __NR_mount 165
__SYSCALL(__NR_mount, sys_mount)
#define __NR_umount2 166
__SYSCALL(__NR_umount2, sys_umount)
#define __NR_swapon 167
__SYSCALL(__NR_swapon, sys_swapon)
#define __NR_swapoff 168
__SYSCALL(__NR_swapoff, sys_swapoff)
#define __NR_reboot 169
__SYSCALL(__NR_reboot, sys_reboot)
#define __NR_sethostname 170
__SYSCALL(__NR_sethostname, sys_sethostname)
#define __NR_setdomainname 171
__SYSCALL(__NR_setdomainname, sys_setdomainname)
#define __NR_iopl 172
__SYSCALL(__NR_iopl, stub_iopl)
#define __NR_ioperm 173
__SYSCALL(__NR_ioperm, sys_ioperm)
#define __NR_create_module 174
__SYSCALL(__NR_create_module, sys_ni_syscall)
#define __NR_init_module 175
__SYSCALL(__NR_init_module, sys_init_module)
#define __NR_delete_module 176
__SYSCALL(__NR_delete_module, sys_delete_module)
#define __NR_get_kernel_syms 177
__SYSCALL(__NR_get_kernel_syms, sys_ni_syscall)
#define __NR_query_module 178
__SYSCALL(__NR_query_module, sys_ni_syscall)
#define __NR_quotactl 179
__SYSCALL(__NR_quotactl, sys_quotactl)
#define __NR_nfsservctl 180
__SYSCALL(__NR_nfsservctl, sys_nfsservctl)
/* reserved for LiS/STREAMS */
#define __NR_getpmsg 181
__SYSCALL(__NR_getpmsg, sys_ni_syscall)
#define __NR_putpmsg 182
__SYSCALL(__NR_putpmsg, sys_ni_syscall)
/* reserved for AFS */
#define __NR_afs_syscall 183
__SYSCALL(__NR_afs_syscall, sys_ni_syscall)
/* reserved for tux */
#define __NR_tuxcall 184
__SYSCALL(__NR_tuxcall, sys_ni_syscall)
#define __NR_security 185
__SYSCALL(__NR_security, sys_ni_syscall)
#define __NR_gettid 186
__SYSCALL(__NR_gettid, sys_gettid)
#define __NR_readahead 187
__SYSCALL(__NR_readahead, sys_readahead)
#define __NR_setxattr 188
__SYSCALL(__NR_setxattr, sys_setxattr)
#define __NR_lsetxattr 189
__SYSCALL(__NR_lsetxattr, sys_lsetxattr)
#define __NR_fsetxattr 190
__SYSCALL(__NR_fsetxattr, sys_fsetxattr)
#define __NR_getxattr 191
__SYSCALL(__NR_getxattr, sys_getxattr)
#define __NR_lgetxattr 192
__SYSCALL(__NR_lgetxattr, sys_lgetxattr)
#define __NR_fgetxattr 193
__SYSCALL(__NR_fgetxattr, sys_fgetxattr)
#define __NR_listxattr 194
__SYSCALL(__NR_listxattr, sys_listxattr)
#define __NR_llistxattr 195
__SYSCALL(__NR_llistxattr, sys_llistxattr)
#define __NR_flistxattr 196
__SYSCALL(__NR_flistxattr, sys_flistxattr)
#define __NR_removexattr 197
__SYSCALL(__NR_removexattr, sys_removexattr)
#define __NR_lremovexattr 198
__SYSCALL(__NR_lremovexattr, sys_lremovexattr)
#define __NR_fremovexattr 199
__SYSCALL(__NR_fremovexattr, sys_fremovexattr)
#define __NR_tkill 200
__SYSCALL(__NR_tkill, sys_tkill)
#define __NR_time 201
__SYSCALL(__NR_time, sys_time)
#define __NR_futex 202
__SYSCALL(__NR_futex, sys_futex)
#define __NR_sched_setaffinity 203
__SYSCALL(__NR_sched_setaffinity, sys_sched_setaffinity)
#define __NR_sched_getaffinity 204
__SYSCALL(__NR_sched_getaffinity, sys_sched_getaffinity)
#define __NR_set_thread_area 205
__SYSCALL(__NR_set_thread_area, sys_ni_syscall) /* use arch_prctl */
#define __NR_io_setup 206
__SYSCALL(__NR_io_setup, sys_io_setup)
#define __NR_io_destroy 207
__SYSCALL(__NR_io_destroy, sys_io_destroy)
#define __NR_io_getevents 208
__SYSCALL(__NR_io_getevents, sys_io_getevents)
#define __NR_io_submit 209
__SYSCALL(__NR_io_submit, sys_io_submit)
#define __NR_io_cancel 210
__SYSCALL(__NR_io_cancel, sys_io_cancel)
#define __NR_get_thread_area 211
__SYSCALL(__NR_get_thread_area, sys_ni_syscall) /* use arch_prctl */
#define __NR_lookup_dcookie 212
__SYSCALL(__NR_lookup_dcookie, sys_lookup_dcookie)
#define __NR_epoll_create 213
__SYSCALL(__NR_epoll_create, sys_epoll_create)
#define __NR_epoll_ctl_old 214
__SYSCALL(__NR_epoll_ctl_old, sys_ni_syscall)
#define __NR_epoll_wait_old 215
__SYSCALL(__NR_epoll_wait_old, sys_ni_syscall)
#define __NR_remap_file_pages 216
__SYSCALL(__NR_remap_file_pages, sys_remap_file_pages)
#define __NR_getdents64 217
__SYSCALL(__NR_getdents64, sys_getdents64)
#define __NR_set_tid_address 218
__SYSCALL(__NR_set_tid_address, sys_set_tid_address)
#define __NR_restart_syscall 219
__SYSCALL(__NR_restart_syscall, sys_restart_syscall)
#define __NR_semtimedop 220
__SYSCALL(__NR_semtimedop, sys_semtimedop)
#define __NR_fadvise64 221
__SYSCALL(__NR_fadvise64, sys_fadvise64)
#define __NR_timer_create 222
__SYSCALL(__NR_timer_create, sys_timer_create)
#define __NR_timer_settime 223
__SYSCALL(__NR_timer_settime, sys_timer_settime)
#define __NR_timer_gettime 224
__SYSCALL(__NR_timer_gettime, sys_timer_gettime)
#define __NR_timer_getoverrun 225
__SYSCALL(__NR_timer_getoverrun, sys_timer_getoverrun)
#define __NR_timer_delete 226
__SYSCALL(__NR_timer_delete, sys_timer_delete)
#define __NR_clock_settime 227
__SYSCALL(__NR_clock_settime, sys_clock_settime)
#define __NR_clock_gettime 228
__SYSCALL(__NR_clock_gettime, sys_clock_gettime)
#define __NR_clock_getres 229
__SYSCALL(__NR_clock_getres, sys_clock_getres)
#define __NR_clock_nanosleep 230
__SYSCALL(__NR_clock_nanosleep, sys_clock_nanosleep)
#define __NR_exit_group 231
__SYSCALL(__NR_exit_group, sys_exit_group)
#define __NR_epoll_wait 232
__SYSCALL(__NR_epoll_wait, sys_epoll_wait)
#define __NR_epoll_ctl 233
__SYSCALL(__NR_epoll_ctl, sys_epoll_ctl)
#define __NR_tgkill 234
__SYSCALL(__NR_tgkill, sys_tgkill)
#define __NR_utimes 235
__SYSCALL(__NR_utimes, sys_utimes)
#define __NR_vserver 236
__SYSCALL(__NR_vserver, sys_ni_syscall)
#define __NR_mbind 237
__SYSCALL(__NR_mbind, sys_mbind)
#define __NR_set_mempolicy 238
__SYSCALL(__NR_set_mempolicy, sys_set_mempolicy)
#define __NR_get_mempolicy 239
__SYSCALL(__NR_get_mempolicy, sys_get_mempolicy)
#define __NR_mq_open 240
__SYSCALL(__NR_mq_open, sys_mq_open)
#define __NR_mq_unlink 241
__SYSCALL(__NR_mq_unlink, sys_mq_unlink)
#define __NR_mq_timedsend 242
__SYSCALL(__NR_mq_timedsend, sys_mq_timedsend)
#define __NR_mq_timedreceive 243
__SYSCALL(__NR_mq_timedreceive, sys_mq_timedreceive)
#define __NR_mq_notify 244
__SYSCALL(__NR_mq_notify, sys_mq_notify)
#define __NR_mq_getsetattr 245
__SYSCALL(__NR_mq_getsetattr, sys_mq_getsetattr)
#define __NR_kexec_load 246
__SYSCALL(__NR_kexec_load, sys_kexec_load)
#define __NR_waitid 247
__SYSCALL(__NR_waitid, sys_waitid)
#define __NR_add_key 248
__SYSCALL(__NR_add_key, sys_add_key)
#define __NR_request_key 249
__SYSCALL(__NR_request_key, sys_request_key)
#define __NR_keyctl 250
__SYSCALL(__NR_keyctl, sys_keyctl)
#define __NR_ioprio_set 251
__SYSCALL(__NR_ioprio_set, sys_ioprio_set)
#define __NR_ioprio_get 252
__SYSCALL(__NR_ioprio_get, sys_ioprio_get)
#define __NR_inotify_init 253
__SYSCALL(__NR_inotify_init, sys_inotify_init)
#define __NR_inotify_add_watch 254
__SYSCALL(__NR_inotify_add_watch, sys_inotify_add_watch)
#define __NR_inotify_rm_watch 255
__SYSCALL(__NR_inotify_rm_watch, sys_inotify_rm_watch)
#define __NR_migrate_pages 256
__SYSCALL(__NR_migrate_pages, sys_migrate_pages)
#define __NR_openat 257
__SYSCALL(__NR_openat, sys_openat)
#define __NR_mkdirat 258
__SYSCALL(__NR_mkdirat, sys_mkdirat)
#define __NR_mknodat 259
__SYSCALL(__NR_mknodat, sys_mknodat)
#define __NR_fchownat 260
__SYSCALL(__NR_fchownat, sys_fchownat)
#define __NR_futimesat 261
__SYSCALL(__NR_futimesat, sys_futimesat)
#define __NR_newfstatat 262
__SYSCALL(__NR_newfstatat, sys_newfstatat)
#define __NR_unlinkat 263
__SYSCALL(__NR_unlinkat, sys_unlinkat)
#define __NR_renameat 264
__SYSCALL(__NR_renameat, sys_renameat)
#define __NR_linkat 265
__SYSCALL(__NR_linkat, sys_linkat)
#define __NR_symlinkat 266
__SYSCALL(__NR_symlinkat, sys_symlinkat)
#define __NR_readlinkat 267
__SYSCALL(__NR_readlinkat, sys_readlinkat)
#define __NR_fchmodat 268
__SYSCALL(__NR_fchmodat, sys_fchmodat)
#define __NR_faccessat 269
__SYSCALL(__NR_faccessat, sys_faccessat)
#define __NR_pselect6 270
__SYSCALL(__NR_pselect6, sys_pselect6)
#define __NR_ppoll 271
__SYSCALL(__NR_ppoll, sys_ppoll)
#define __NR_unshare 272
__SYSCALL(__NR_unshare, sys_unshare)
#define __NR_set_robust_list 273
__SYSCALL(__NR_set_robust_list, sys_set_robust_list)
#define __NR_get_robust_list 274
__SYSCALL(__NR_get_robust_list, sys_get_robust_list)
#define __NR_splice 275
__SYSCALL(__NR_splice, sys_splice)
#define __NR_tee 276
__SYSCALL(__NR_tee, sys_tee)
#define __NR_sync_file_range 277
__SYSCALL(__NR_sync_file_range, sys_sync_file_range)
#define __NR_vmsplice 278
__SYSCALL(__NR_vmsplice, sys_vmsplice)
#define __NR_move_pages 279
__SYSCALL(__NR_move_pages, sys_move_pages)
#define __NR_utimensat 280
__SYSCALL(__NR_utimensat, sys_utimensat)
#define __IGNORE_getcpu /* implemented as a vsyscall */
#define __NR_epoll_pwait 281
__SYSCALL(__NR_epoll_pwait, sys_epoll_pwait)
#define __NR_signalfd 282
__SYSCALL(__NR_signalfd, sys_signalfd)
#define __NR_timerfd_create 283
__SYSCALL(__NR_timerfd_create, sys_timerfd_create)
#define __NR_eventfd 284
__SYSCALL(__NR_eventfd, sys_eventfd)
#define __NR_fallocate 285
__SYSCALL(__NR_fallocate, sys_fallocate)
#define __NR_timerfd_settime 286
__SYSCALL(__NR_timerfd_settime, sys_timerfd_settime)
#define __NR_timerfd_gettime 287
__SYSCALL(__NR_timerfd_gettime, sys_timerfd_gettime)
#define __NR_accept4 288
__SYSCALL(__NR_accept4, sys_accept4)
#define __NR_signalfd4 289
__SYSCALL(__NR_signalfd4, sys_signalfd4)
#define __NR_eventfd2 290
__SYSCALL(__NR_eventfd2, sys_eventfd2)
#define __NR_epoll_create1 291
__SYSCALL(__NR_epoll_create1, sys_epoll_create1)
#define __NR_dup3 292
__SYSCALL(__NR_dup3, sys_dup3)
#define __NR_pipe2 293
__SYSCALL(__NR_pipe2, sys_pipe2)
#define __NR_inotify_init1 294
__SYSCALL(__NR_inotify_init1, sys_inotify_init1)
#define __NR_preadv 295
__SYSCALL(__NR_preadv, sys_preadv)
#define __NR_pwritev 296
__SYSCALL(__NR_pwritev, sys_pwritev)
#define __NR_rt_tgsigqueueinfo 297
__SYSCALL(__NR_rt_tgsigqueueinfo, sys_rt_tgsigqueueinfo)
#define __NR_perf_event_open 298
__SYSCALL(__NR_perf_event_open, sys_perf_event_open)
#define __NR_recvmmsg 299
__SYSCALL(__NR_recvmmsg, sys_recvmmsg)
在Linux中，系统调用是用户空间访问内核的唯一手段；除异常和中断外，它们是内核惟一的合法入口。
系统调用必须验证参数是否合法（fd，pid..），最重要的是验证指针是否有效。如果一个进程可以给内核传递指针，但是没有进行验证，那么就可以给出一个它根本没有访问权限的指针，哄骗内核去为它拷贝不允许它访问的数据，这会产生严重的后果。
因此，在接收用户空间传递的指针时，必须保证：
1.指针指向的内存区域是用户空间，进程决不能哄骗内核去访问内核空间数据（属于内核的1G内存）
2.指针指向的内存区域在进程的地址空间里，进程决不能哄骗内核去读取其他进程的数据（不能访问其他进程地址空间）
3.如果是读，该内存应被标记为刻度。如果是写，该内存应被标记为可写。进程决不能绕过内存访问限制
用户空间<-->内核空间，内核提供了两个方法来完成检查和数据拷贝。
为了向用户空间写入数据：
/**
* copy_to_user: - Copy a block of data into user space.
* @to: Destination address, in user space.
* @from: Source address, in kernel space.
* @n: Number of bytes to copy.
*
* Context: User context only. This function may sleep.
*
* Copy data from kernel space to user space.
*
* Returns number of bytes that could not be copied.
* On success, this will be zero.
*/
unsigned long
copy_to_user(void __user *to, const void *from, unsigned long n)
{
if (access_ok(VERIFY_WRITE, to, n))
n = __copy_to_user(to, from, n);
return n;
}
为了从用户空间读数据
static inline unsigned long __must_check copy_from_user(void *to,
const void __user *from,
unsigned long n)
{
int sz = __compiletime_object_size(to);
if (likely(sz == -1 || sz >= n))
n = _copy_from_user(to, from, n);
else
copy_from_user_overflow();
return n;
}
系统调用的返回值放入了errno全局变量中，可以通过调用perror()把变量翻译成可理解字符串
以fork()来看看系统调用
在unistd.h
#define __NR_fork 1079
#ifdef CONFIG_MMU
__SYSCALL(__NR_fork, sys_fork)
#else
__SYSCALL(__NR_fork, sys_ni_syscall)
#endif /* CONFIG_MMU */
在syscalls.h
asmlinkage int sys_fork(struct pt_regs *);
在process.c
int sys_fork(struct pt_regs *regs)
{
return do_fork(SIGCHLD, regs->sp, regs, 0, NULL, NULL);
}
系统调用访问示例
操作系统使用系统调用表将系统调用编号翻译为特定的系统调用。系统调用表包含有实现每个系统调用的函数的地址。例如，read() 系统调用函数名为 sys_read。read() 系统调用编号是 3<unistd_32.h>，所以 sys_read() 位于系统调用表的第四个条目中（因为系统调用起始编号为0）。从地址 sys_call_table + (3 * word_size) 读取数据，得到 sys_read() 的地址。
感谢https://blog.csdn.net/q_l_s/article/details/55101496，写的很详细。
------------------
from:
https://blog.csdn.net/sinat_33518009/article/details/93416217