linux系统调用，linux系统调用函数

文章由LinuxBoy分享于2019-04-03 05:04:11热评（417）

linux系统调用，linux系统调用函数

2016-03-18 17:10:19

张超《Linux内核分析》MOOC课程http://mooc.study.163.com/course/USTC-1000029000

我的实验平台以及代码见https://www.shiyanlou.com/courses/reports/986221

实验要求：

扒开系统调用的三层皮

使用库函数触发一个系统调用

C代码中嵌入汇编代码的写法

使用嵌入式汇编代码触发同一个系统调用

系统调用在内核代码中的处理过程

系统调用：

操作系统为用户态进程与硬件设备进行交互提供了一组接口——系统调用

把用户从底层的硬件编程中解放出来

极大的提高了系统的安全性

使用户程序具有可移植性

API和系统调用

应用编程接口(application program interface, API) 和系统调用是不同的

API只是一个函数定义

系统调用通过软中断向内核发出一个明确的请求

Libc库定义的一些API引用了封装例程(wrapper routine，唯一目的就是发布系统调用)

一般每个系统调用对应一个封装例程

库再用这些封装例程定义出给用户的API

不是每个API都对应一个特定的系统调用。

API可能直接提供用户态的服务

一个单独的API可能调用几个系统调用

不同的API可能调用了同一个系统调用

返回值

大部分封装例程返回一个整数，其值的含义依赖于相应的系统调用

-1在多数情况下表示内核不能满足进程的请求

Libc中定义的errno变量包含特定的出错码

应用程序、封装例程、系统调用处理程序及系统调用服务例程之间的关系

系统调用程序及服务例程

当用户态进程调用一个系统调用时，CPU切换到内核态并开始执行一个内核函数。

在Linux中是通过执行int $0x80来执行系统调用的，这条汇编指令产生向量为128的编程异常

Intel Pentium II中引入了sysenter指令（快速系统调用），2.6已经支持（本课程不考虑这个）

传参：

内核实现了很多不同的系统调用，进程必须指明需要哪个系统调用，这需要传递一个名为系统调用号的参数

使用eax寄存器

参数传递

系统调用也需要输入输出参数，例如

实际的值

用户态进程地址空间的变量的地址

甚至是包含指向用户态函数的指针的数据结构的地址

system_call是linux中所有系统调用的入口点，每个系统调用至少有一个参数，即由eax传递的系统调用号

一个应用程序调用fork()封装例程，那么在执行int $0x80之前就把eax寄存器的值置为2(即__NR_fork)。

这个寄存器的设置是libc库中的封装例程进行的，因此用户一般不关心系统调用号

进入sys_call之后，立即将eax的值压入内核堆栈

寄存器传递参数具有如下限制：

1）每个参数的长度不能超过寄存器的长度，即32位

2）在系统调用号（eax）之外，参数的个数不能超过6个（ebx，ecx，edx，esi，edi，ebp）

系统调用列表参见：

# # 32-bit system call numbers and entry vectors # # The format is: # <number> <abi> <name> <entry point> <compat entry point> # # The abi is always "i386" for this file. # 0 i386 restart_syscall sys_restart_syscall 1 i386 exit sys_exit 2 i386 fork sys_fork stub32_fork 3 i386 read sys_read 4 i386 write sys_write 5 i386 open sys_open compat_sys_open 6 i386 close sys_close 7 i386 waitpid sys_waitpid sys32_waitpid 8 i386 creat sys_creat 9 i386 link sys_link 10 i386 unlink sys_unlink 11 i386 execve sys_execve stub32_execve 12 i386 chdir sys_chdir 13 i386 time sys_time compat_sys_time 14 i386 mknod sys_mknod 15 i386 chmod sys_chmod 16 i386 lchown sys_lchown16 17 i386 break 18 i386 oldstat sys_stat 19 i386 lseek sys_lseek compat_sys_lseek 20 i386 getpid sys_getpid 21 i386 mount sys_mount compat_sys_mount 22 i386 umount sys_oldumount 23 i386 setuid sys_setuid16 24 i386 getuid sys_getuid16 25 i386 stime sys_stime compat_sys_stime 26 i386 ptrace sys_ptrace compat_sys_ptrace 27 i386 alarm sys_alarm 28 i386 oldfstat sys_fstat 29 i386 pause sys_pause 30 i386 utime sys_utime compat_sys_utime 31 i386 stty 32 i386 gtty 33 i386 access sys_access 34 i386 nice sys_nice 35 i386 ftime 36 i386 sync sys_sync 37 i386 kill sys_kill 38 i386 rename sys_rename 39 i386 mkdir sys_mkdir 40 i386 rmdir sys_rmdir 41 i386 dup sys_dup 42 i386 pipe sys_pipe 43 i386 times sys_times compat_sys_times 44 i386 prof 45 i386 brk sys_brk 46 i386 setgid sys_setgid16 47 i386 getgid sys_getgid16 48 i386 signal sys_signal 49 i386 geteuid sys_geteuid16 50 i386 getegid sys_getegid16 51 i386 acct sys_acct 52 i386 umount2 sys_umount 53 i386 lock 54 i386 ioctl sys_ioctl compat_sys_ioctl 55 i386 fcntl sys_fcntl compat_sys_fcntl64 56 i386 mpx 57 i386 setpgid sys_setpgid 58 i386 ulimit 59 i386 oldolduname sys_olduname 60 i386 umask sys_umask 61 i386 chroot sys_chroot 62 i386 ustat sys_ustat compat_sys_ustat 63 i386 dup2 sys_dup2 64 i386 getppid sys_getppid 65 i386 getpgrp sys_getpgrp 66 i386 setsid sys_setsid 67 i386 sigaction sys_sigaction compat_sys_sigaction 68 i386 sgetmask sys_sgetmask 69 i386 ssetmask sys_ssetmask 70 i386 setreuid sys_setreuid16 71 i386 setregid sys_setregid16 72 i386 sigsuspend sys_sigsuspend sys_sigsuspend 73 i386 sigpending sys_sigpending compat_sys_sigpending 74 i386 sethostname sys_sethostname 75 i386 setrlimit sys_setrlimit compat_sys_setrlimit 76 i386 getrlimit sys_old_getrlimit compat_sys_old_getrlimit 77 i386 getrusage sys_getrusage compat_sys_getrusage 78 i386 gettimeofday sys_gettimeofday compat_sys_gettimeofday 79 i386 settimeofday sys_settimeofday compat_sys_settimeofday 80 i386 getgroups sys_getgroups16 81 i386 setgroups sys_setgroups16 82 i386 select sys_old_select compat_sys_old_select 83 i386 symlink sys_symlink 84 i386 oldlstat sys_lstat 85 i386 readlink sys_readlink 86 i386 uselib sys_uselib 87 i386 swapon sys_swapon 88 i386 reboot sys_reboot 89 i386 readdir sys_old_readdir compat_sys_old_readdir 90 i386 mmap sys_old_mmap sys32_mmap 91 i386 munmap sys_munmap 92 i386 truncate sys_truncate compat_sys_truncate 93 i386 ftruncate sys_ftruncate compat_sys_ftruncate 94 i386 fchmod sys_fchmod 95 i386 fchown sys_fchown16 96 i386 getpriority sys_getpriority 97 i386 setpriority sys_setpriority 98 i386 profil 99 i386 statfs sys_statfs compat_sys_statfs 100 i386 fstatfs sys_fstatfs compat_sys_fstatfs 101 i386 ioperm sys_ioperm 102 i386 socketcall sys_socketcall compat_sys_socketcall 103 i386 syslog sys_syslog 104 i386 setitimer sys_setitimer compat_sys_setitimer 105 i386 getitimer sys_getitimer compat_sys_getitimer 106 i386 stat sys_newstat compat_sys_newstat 107 i386 lstat sys_newlstat compat_sys_newlstat 108 i386 fstat sys_newfstat compat_sys_newfstat 109 i386 olduname sys_uname 110 i386 iopl sys_iopl 111 i386 vhangup sys_vhangup 112 i386 idle 113 i386 vm86old sys_vm86old sys32_vm86_warning 114 i386 wait4 sys_wait4 compat_sys_wait4 115 i386 swapoff sys_swapoff 116 i386 sysinfo sys_sysinfo compat_sys_sysinfo 117 i386 ipc sys_ipc compat_sys_ipc 118 i386 fsync sys_fsync 119 i386 sigreturn sys_sigreturn stub32_sigreturn 120 i386 clone sys_clone stub32_clone 121 i386 setdomainname sys_setdomainname 122 i386 uname sys_newuname 123 i386 modify_ldt sys_modify_ldt 124 i386 adjtimex sys_adjtimex compat_sys_adjtimex 125 i386 mprotect sys_mprotect 126 i386 sigprocmask sys_sigprocmask compat_sys_sigprocmask 127 i386 create_module 128 i386 init_module sys_init_module 129 i386 delete_module sys_delete_module 130 i386 get_kernel_syms 131 i386 quotactl sys_quotactl sys32_quotactl 132 i386 getpgid sys_getpgid 133 i386 fchdir sys_fchdir 134 i386 bdflush sys_bdflush 135 i386 sysfs sys_sysfs 136 i386 personality sys_personality 137 i386 afs_syscall 138 i386 setfsuid sys_setfsuid16 139 i386 setfsgid sys_setfsgid16 140 i386 _llseek sys_llseek 141 i386 getdents sys_getdents compat_sys_getdents 142 i386 _newselect sys_select compat_sys_select 143 i386 flock sys_flock 144 i386 msync sys_msync 145 i386 readv sys_readv compat_sys_readv 146 i386 writev sys_writev compat_sys_writev 147 i386 getsid sys_getsid 148 i386 fdatasync sys_fdatasync 149 i386 _sysctl sys_sysctl compat_sys_sysctl 150 i386 mlock sys_mlock 151 i386 munlock sys_munlock 152 i386 mlockall sys_mlockall 153 i386 munlockall sys_munlockall 154 i386 sched_setparam sys_sched_setparam 155 i386 sched_getparam sys_sched_getparam 156 i386 sched_setscheduler sys_sched_setscheduler 157 i386 sched_getscheduler sys_sched_getscheduler 158 i386 sched_yield sys_sched_yield 159 i386 sched_get_priority_max sys_sched_get_priority_max 160 i386 sched_get_priority_min sys_sched_get_priority_min 161 i386 sched_rr_get_interval sys_sched_rr_get_interval compat_sys_sched_rr_get_interval 162 i386 nanosleep sys_nanosleep compat_sys_nanosleep 163 i386 mremap sys_mremap 164 i386 setresuid sys_setresuid16 165 i386 getresuid sys_getresuid16 166 i386 vm86 sys_vm86 sys32_vm86_warning 167 i386 query_module 168 i386 poll sys_poll 169 i386 nfsservctl 170 i386 setresgid sys_setresgid16 171 i386 getresgid sys_getresgid16 172 i386 prctl sys_prctl 173 i386 rt_sigreturn sys_rt_sigreturn stub32_rt_sigreturn 174 i386 rt_sigaction sys_rt_sigaction compat_sys_rt_sigaction 175 i386 rt_sigprocmask sys_rt_sigprocmask 176 i386 rt_sigpending sys_rt_sigpending compat_sys_rt_sigpending 177 i386 rt_sigtimedwait sys_rt_sigtimedwait compat_sys_rt_sigtimedwait 178 i386 rt_sigqueueinfo sys_rt_sigqueueinfo compat_sys_rt_sigqueueinfo 179 i386 rt_sigsuspend sys_rt_sigsuspend 180 i386 pread64 sys_pread64 sys32_pread 181 i386 pwrite64 sys_pwrite64 sys32_pwrite 182 i386 chown sys_chown16 183 i386 getcwd sys_getcwd 184 i386 capget sys_capget 185 i386 capset sys_capset 186 i386 sigaltstack sys_sigaltstack compat_sys_sigaltstack 187 i386 sendfile sys_sendfile compat_sys_sendfile 188 i386 getpmsg 189 i386 putpmsg 190 i386 vfork sys_vfork stub32_vfork 191 i386 ugetrlimit sys_getrlimit compat_sys_getrlimit 192 i386 mmap2 sys_mmap_pgoff 193 i386 truncate64 sys_truncate64 sys32_truncate64 194 i386 ftruncate64 sys_ftruncate64 sys32_ftruncate64 195 i386 stat64 sys_stat64 sys32_stat64 196 i386 lstat64 sys_lstat64 sys32_lstat64 197 i386 fstat64 sys_fstat64 sys32_fstat64 198 i386 lchown32 sys_lchown 199 i386 getuid32 sys_getuid 200 i386 getgid32 sys_getgid 201 i386 geteuid32 sys_geteuid 202 i386 getegid32 sys_getegid 203 i386 setreuid32 sys_setreuid 204 i386 setregid32 sys_setregid 205 i386 getgroups32 sys_getgroups 206 i386 setgroups32 sys_setgroups 207 i386 fchown32 sys_fchown 208 i386 setresuid32 sys_setresuid 209 i386 getresuid32 sys_getresuid 210 i386 setresgid32 sys_setresgid 211 i386 getresgid32 sys_getresgid 212 i386 chown32 sys_chown 213 i386 setuid32 sys_setuid 214 i386 setgid32 sys_setgid 215 i386 setfsuid32 sys_setfsuid 216 i386 setfsgid32 sys_setfsgid 217 i386 pivot_root sys_pivot_root 218 i386 mincore sys_mincore 219 i386 madvise sys_madvise 220 i386 getdents64 sys_getdents64 compat_sys_getdents64 221 i386 fcntl64 sys_fcntl64 compat_sys_fcntl64 # 222 is unused # 223 is unused 224 i386 gettid sys_gettid 225 i386 readahead sys_readahead sys32_readahead 226 i386 setxattr sys_setxattr 227 i386 lsetxattr sys_lsetxattr 228 i386 fsetxattr sys_fsetxattr 229 i386 getxattr sys_getxattr 230 i386 lgetxattr sys_lgetxattr 231 i386 fgetxattr sys_fgetxattr 232 i386 listxattr sys_listxattr 233 i386 llistxattr sys_llistxattr 234 i386 flistxattr sys_flistxattr 235 i386 removexattr sys_removexattr 236 i386 lremovexattr sys_lremovexattr 237 i386 fremovexattr sys_fremovexattr 238 i386 tkill sys_tkill 239 i386 sendfile64 sys_sendfile64 240 i386 futex sys_futex compat_sys_futex 241 i386 sched_setaffinity sys_sched_setaffinity compat_sys_sched_setaffinity 242 i386 sched_getaffinity sys_sched_getaffinity compat_sys_sched_getaffinity 243 i386 set_thread_area sys_set_thread_area 244 i386 get_thread_area sys_get_thread_area 245 i386 io_setup sys_io_setup compat_sys_io_setup 246 i386 io_destroy sys_io_destroy 247 i386 io_getevents sys_io_getevents compat_sys_io_getevents 248 i386 io_submit sys_io_submit compat_sys_io_submit 249 i386 io_cancel sys_io_cancel 250 i386 fadvise64 sys_fadvise64 sys32_fadvise64 # 251 is available for reuse (was briefly sys_set_zone_reclaim) 252 i386 exit_group sys_exit_group 253 i386 lookup_dcookie sys_lookup_dcookie compat_sys_lookup_dcookie 254 i386 epoll_create sys_epoll_create 255 i386 epoll_ctl sys_epoll_ctl 256 i386 epoll_wait sys_epoll_wait 257 i386 remap_file_pages sys_remap_file_pages 258 i386 set_tid_address sys_set_tid_address 259 i386 timer_create sys_timer_create compat_sys_timer_create 260 i386 timer_settime sys_timer_settime compat_sys_timer_settime 261 i386 timer_gettime sys_timer_gettime compat_sys_timer_gettime 262 i386 timer_getoverrun sys_timer_getoverrun 263 i386 timer_delete sys_timer_delete 264 i386 clock_settime sys_clock_settime compat_sys_clock_settime 265 i386 clock_gettime sys_clock_gettime compat_sys_clock_gettime 266 i386 clock_getres sys_clock_getres compat_sys_clock_getres 267 i386 clock_nanosleep sys_clock_nanosleep compat_sys_clock_nanosleep 268 i386 statfs64 sys_statfs64 compat_sys_statfs64 269 i386 fstatfs64 sys_fstatfs64 compat_sys_fstatfs64 270 i386 tgkill sys_tgkill 271 i386 utimes sys_utimes compat_sys_utimes 272 i386 fadvise64_64 sys_fadvise64_64 sys32_fadvise64_64 273 i386 vserver 274 i386 mbind sys_mbind 275 i386 get_mempolicy sys_get_mempolicy compat_sys_get_mempolicy 276 i386 set_mempolicy sys_set_mempolicy 277 i386 mq_open sys_mq_open compat_sys_mq_open 278 i386 mq_unlink sys_mq_unlink 279 i386 mq_timedsend sys_mq_timedsend compat_sys_mq_timedsend 280 i386 mq_timedreceive sys_mq_timedreceive compat_sys_mq_timedreceive 281 i386 mq_notify sys_mq_notify compat_sys_mq_notify 282 i386 mq_getsetattr sys_mq_getsetattr compat_sys_mq_getsetattr 283 i386 kexec_load sys_kexec_load compat_sys_kexec_load 284 i386 waitid sys_waitid compat_sys_waitid # 285 sys_setaltroot 286 i386 add_key sys_add_key 287 i386 request_key sys_request_key 288 i386 keyctl sys_keyctl 289 i386 ioprio_set sys_ioprio_set 290 i386 ioprio_get sys_ioprio_get 291 i386 inotify_init sys_inotify_init 292 i386 inotify_add_watch sys_inotify_add_watch 293 i386 inotify_rm_watch sys_inotify_rm_watch 294 i386 migrate_pages sys_migrate_pages 295 i386 openat sys_openat compat_sys_openat 296 i386 mkdirat sys_mkdirat 297 i386 mknodat sys_mknodat 298 i386 fchownat sys_fchownat 299 i386 futimesat sys_futimesat compat_sys_futimesat 300 i386 fstatat64 sys_fstatat64 sys32_fstatat 301 i386 unlinkat sys_unlinkat 302 i386 renameat sys_renameat 303 i386 linkat sys_linkat 304 i386 symlinkat sys_symlinkat 305 i386 readlinkat sys_readlinkat 306 i386 fchmodat sys_fchmodat 307 i386 faccessat sys_faccessat 308 i386 pselect6 sys_pselect6 compat_sys_pselect6 309 i386 ppoll sys_ppoll compat_sys_ppoll 310 i386 unshare sys_unshare 311 i386 set_robust_list sys_set_robust_list compat_sys_set_robust_list 312 i386 get_robust_list sys_get_robust_list compat_sys_get_robust_list 313 i386 splice sys_splice 314 i386 sync_file_range sys_sync_file_range sys32_sync_file_range 315 i386 tee sys_tee 316 i386 vmsplice sys_vmsplice compat_sys_vmsplice 317 i386 move_pages sys_move_pages compat_sys_move_pages 318 i386 getcpu sys_getcpu 319 i386 epoll_pwait sys_epoll_pwait 320 i386 utimensat sys_utimensat compat_sys_utimensat 321 i386 signalfd sys_signalfd compat_sys_signalfd 322 i386 timerfd_create sys_timerfd_create 323 i386 eventfd sys_eventfd 324 i386 fallocate sys_fallocate sys32_fallocate 325 i386 timerfd_settime sys_timerfd_settime compat_sys_timerfd_settime 326 i386 timerfd_gettime sys_timerfd_gettime compat_sys_timerfd_gettime 327 i386 signalfd4 sys_signalfd4 compat_sys_signalfd4 328 i386 eventfd2 sys_eventfd2 329 i386 epoll_create1 sys_epoll_create1 330 i386 dup3 sys_dup3 331 i386 pipe2 sys_pipe2 332 i386 inotify_init1 sys_inotify_init1 333 i386 preadv sys_preadv compat_sys_preadv 334 i386 pwritev sys_pwritev compat_sys_pwritev 335 i386 rt_tgsigqueueinfo sys_rt_tgsigqueueinfo compat_sys_rt_tgsigqueueinfo 336 i386 perf_event_open sys_perf_event_open 337 i386 recvmmsg sys_recvmmsg compat_sys_recvmmsg 338 i386 fanotify_init sys_fanotify_init 339 i386 fanotify_mark sys_fanotify_mark compat_sys_fanotify_mark 340 i386 prlimit64 sys_prlimit64 341 i386 name_to_handle_at sys_name_to_handle_at 342 i386 open_by_handle_at sys_open_by_handle_at compat_sys_open_by_handle_at 343 i386 clock_adjtime sys_clock_adjtime compat_sys_clock_adjtime 344 i386 syncfs sys_syncfs 345 i386 sendmmsg sys_sendmmsg compat_sys_sendmmsg 346 i386 setns sys_setns 347 i386 process_vm_readv sys_process_vm_readv compat_sys_process_vm_readv 348 i386 process_vm_writev sys_process_vm_writev compat_sys_process_vm_writev 349 i386 kcmp sys_kcmp 350 i386 finit_module sys_finit_module 351 i386 sched_setattr sys_sched_setattr 352 i386 sched_getattr sys_sched_getattr 353 i386 renameat2 sys_renameat2 354 i386 seccomp sys_seccomp 355 i386 getrandom sys_getrandom 356 i386 memfd_create sys_memfd_create 357 i386 bpf sys_bpf 系统调用

使用库函数触发一个系统调用

在这里我们选用的是：20 getpid

getpid（取得进程识别码）