syscall
- Ring 0 - 内核态
- 初始化中断或异常处理机制
- 代码可以直接访问硬件、管理内存和执行CPU的所有指令集
- 内核和驱动程序
- Ring 1 & Ring 2 - 很少使用 - 例如 驱动程序
- Ring 3 - 用户态
- 不能直接访问硬件或执行某些敏感的CPU指令
- 通过 系统调用/syscall 访问内核态
- 汇编指令
- x86
int 0x80- IDT - Interrupt Descriptor Table - 中断描述符表
- 0x80 - 0x85
lidt- load IDT
- x86-64
syscall- MSR - Model Specific Register - 模型特定寄存器
rdmsr- read MSRwrmsr- write MSR
- arm
swi 0- software interrupt - aaarch64
svc #0- supervisor call
- x86
- 当 linux 完成 init 之后 syscall 就是唯一的用户态和内核态交互方式
- 设置系统调用表
arch/x86/include/generated/uapi/asm/unistd_64.h- 调用号arch/x86/entry/syscalls/syscall_64.tbl
- 初始化中断或异常处理机制
- 配置用户空间到内核空间的切换
- 设置系统调用表
tip
- 大多数应用通过 libc 的封装调用 syscall
- 例如
write,read而不是syscall(SYS_write, 1, "Hello, world!\n", 14) - 大多动态依赖 libc - 引入环境依赖
- 不少应用可通过静态链接 musl 来避免依赖 libc
- 例如
- Golang 是直接调用 syscall - https://pkg.go.dev/syscall
- 不依赖 libc - 跨平台
- 静态编译
// SYS_write=1
syscall(SYS_write, 1, "Hello, world!\n", 14);
ausyscall 2 # open
ausyscall --dump
| N | SYS_name | api |
|---|---|---|
| 0 | read | ssize_t read(int fd, void *buf, size_t count) |
| 1 | write | |
| 2 | open | |
| 3 | close | |
| 4 | stat | |
| 5 | fstat | |
| 6 | lstat | |
| 7 | poll | |
| 8 | lseek | |
| 9 | mmap | |
| 10 | mprotect | |
| 11 | munmap | |
| 12 | brk | |
| 13 | rt_sigaction | |
| 14 | rt_sigprocmask | |
| 15 | rt_sigreturn | |
| 16 | ioctl | |
| 17 | pread | |
| 18 | pwrite | |
| 19 | readv | |
| 20 | writev | |
| 21 | access | |
| 22 | pipe | |
| 23 | select | |
| 24 | sched_yield | |
| 25 | mremap | |
| 26 | msync | |
| 27 | mincore | |
| 28 | madvise | |
| 29 | shmget | |
| 30 | shmat | |
| 31 | shmctl | |
| 32 | dup | |
| 33 | dup2 | |
| 34 | pause | |
| 35 | nanosleep | |
| 36 | getitimer | |
| 37 | alarm | |
| 38 | setitimer | |
| 39 | getpid | |
| 40 | sendfile | |
| 41 | socket | |
| 42 | connect | |
| 43 | accept | |
| 44 | sendto | |
| 45 | recvfrom | |
| 46 | sendmsg | |
| 47 | recvmsg | |
| 48 | shutdown | |
| 49 | bind | |
| 50 | listen | |
| 51 | getsockname | |
| 52 | getpeername | |
| 53 | socketpair | |
| 54 | setsockopt | |
| 55 | getsockopt | |
| 56 | clone | |
| 57 | fork | |
| 58 | vfork | |
| 59 | execve | |
| 60 | exit | |
| 61 | wait4 | |
| 62 | kill | |
| 63 | uname | |
| 64 | semget | |
| 65 | semop | |
| 66 | semctl | |
| 67 | shmdt | |
| 68 | msgget | |
| 69 | msgsnd | |
| 70 | msgrcv | |
| 71 | msgctl | |
| 72 | fcntl | |
| 73 | flock | |
| 74 | fsync | |
| 75 | fdatasync | |
| 76 | truncate | |
| 77 | ftruncate | |
| 78 | getdents | ssize_t posix_getdents(int fd, void *buf, size_t len, int flags),readdir |
| 79 | getcwd | |
| 80 | chdir | |
| 81 | fchdir | |
| 82 | rename | int rename(const char *old, const char *new) |
| 83 | mkdir | |
| 84 | rmdir | |
| 85 | creat | |
| 86 | link | |
| 87 | unlink | |
| 88 | symlink | |
| 89 | readlink | |
| 90 | chmod | |
| 91 | fchmod | |
| 92 | chown | |
| 93 | fchown | |
| 94 | lchown | |
| 95 | umask | |
| 96 | gettimeofday | |
| 97 | getrlimit | |
| 98 | getrusage | |
| 99 | sysinfo | |
| 100 | times | |
| 101 | ptrace | |
| 102 | getuid | |
| 103 | syslog | |
| 104 | getgid | |
| 105 | setuid | |
| 106 | setgid | |
| 107 | geteuid | |
| 108 | getegid | |
| 109 | setpgid | |
| 110 | getppid | |
| 111 | getpgrp | |
| 112 | setsid | |
| 113 | setreuid | |
| 114 | setregid | |
| 115 | getgroups | |
| 116 | setgroups | |
| 117 | setresuid | |
| 118 | getresuid | |
| 119 | setresgid | |
| 120 | getresgid | |
| 121 | getpgid | |
| 122 | setfsuid | |
| 123 | setfsgid | |
| 124 | getsid | |
| 125 | capget | |
| 126 | capset | |
| 127 | rt_sigpending | |
| 128 | rt_sigtimedwait | |
| 129 | rt_sigqueueinfo | |
| 130 | rt_sigsuspend | |
| 131 | sigaltstack | |
| 132 | utime | |
| 133 | mknod | |
| 134 | uselib | |
| 135 | personality | |
| 136 | ustat | |
| 137 | statfs | |
| 138 | fstatfs | |
| 139 | sysfs | |
| 140 | getpriority | |
| 141 | setpriority | |
| 142 | sched_setparam | |
| 143 | sched_getparam | |
| 144 | sched_setscheduler | |
| 145 | sched_getscheduler | |
| 146 | sched_get_priority_max | |
| 147 | sched_get_priority_min | |
| 148 | sched_rr_get_interval | |
| 149 | mlock | |
| 150 | munlock | |
| 151 | mlockall | |
| 152 | munlockall | |
| 153 | vhangup | |
| 154 | modify_ldt | |
| 155 | pivot_root | |
| 156 | _sysctl | |
| 157 | prctl | |
| 158 | arch_prctl | |
| 159 | adjtimex | |
| 160 | setrlimit | |
| 161 | chroot | |
| 162 | sync | |
| 163 | acct | |
| 164 | settimeofday | |
| 165 | mount | |
| 166 | umount2 | |
| 167 | swapon | |
| 168 | swapoff | |
| 169 | reboot | |
| 170 | sethostname | |
| 171 | setdomainname | |
| 172 | iopl | |
| 173 | ioperm | |
| 174 | create_module | |
| 175 | init_module | |
| 176 | delete_module | |
| 177 | get_kernel_syms | |
| 178 | query_module | |
| 179 | quotactl | |
| 180 | nfsservctl | |
| 181 | getpmsg | |
| 182 | putpmsg | |
| 183 | afs_syscall | |
| 184 | tuxcall | |
| 185 | security | |
| 186 | gettid | |
| 187 | readahead | |
| 188 | setxattr | |
| 189 | lsetxattr | |
| 190 | fsetxattr | |
| 191 | getxattr | |
| 192 | lgetxattr | |
| 193 | fgetxattr | |
| 194 | listxattr | |
| 195 | llistxattr | |
| 196 | flistxattr | |
| 197 | removexattr | |
| 198 | lremovexattr | |
| 199 | fremovexattr | |
| 200 | tkill | |
| 201 | time | |
| 202 | futex | |
| 203 | sched_setaffinity | |
| 204 | sched_getaffinity | |
| 205 | set_thread_area | |
| 206 | io_setup | |
| 207 | io_destroy | |
| 208 | io_getevents | |
| 209 | io_submit | |
| 210 | io_cancel | |
| 211 | get_thread_area | |
| 212 | lookup_dcookie | |
| 213 | epoll_create | |
| 214 | epoll_ctl_old | |
| 215 | epoll_wait_old | |
| 216 | remap_file_pages | |
| 217 | getdents64 | |
| 218 | set_tid_address | |
| 219 | restart_syscall | |
| 220 | semtimedop | |
| 221 | fadvise64 | |
| 222 | timer_create | |
| 223 | timer_settime | |
| 224 | timer_gettime | |
| 225 | timer_getoverrun | |
| 226 | timer_delete | |
| 227 | clock_settime | |
| 228 | clock_gettime | |
| 229 | clock_getres | |
| 230 | clock_nanosleep | |
| 231 | exit_group | |
| 232 | epoll_wait | |
| 233 | epoll_ctl | |
| 234 | tgkill | |
| 235 | utimes | |
| 236 | vserver | |
| 237 | mbind | |
| 238 | set_mempolicy | |
| 239 | get_mempolicy | |
| 240 | mq_open | |
| 241 | mq_unlink | |
| 242 | mq_timedsend | |
| 243 | mq_timedreceive | |
| 244 | mq_notify | |
| 245 | mq_getsetattr | |
| 246 | kexec_load | |
| 247 | waitid | |
| 248 | add_key | |
| 249 | request_key | |
| 250 | keyctl | |
| 251 | ioprio_set | |
| 252 | ioprio_get | |
| 253 | inotify_init | |
| 254 | inotify_add_watch | |
| 255 | inotify_rm_watch | |
| 256 | migrate_pages | |
| 257 | openat | |
| 258 | mkdirat | |
| 259 | mknodat | |
| 260 | fchownat | |
| 261 | futimesat | |
| 262 | newfstatat | |
| 263 | unlinkat | |
| 264 | renameat | int renameat(int oldfd, const char *old, int newfd, const char *new) |
| 265 | linkat | |
| 266 | symlinkat | |
| 267 | readlinkat | |
| 268 | fchmodat | |
| 269 | faccessat | |
| 270 | pselect6 | |
| 271 | ppoll | |
| 272 | unshare | |
| 273 | set_robust_list | |
| 274 | get_robust_list | |
| 275 | splice | |
| 276 | tee | |
| 277 | sync_file_range | |
| 278 | vmsplice | |
| 279 | move_pages | |
| 280 | utimensat | |
| 281 | epoll_pwait | |
| 282 | signalfd | |
| 283 | timerfd_create | |
| 284 | eventfd | |
| 285 | fallocate | |
| 286 | timerfd_settime | |
| 287 | timerfd_gettime | |
| 288 | accept4 | |
| 289 | signalfd4 | |
| 290 | eventfd2 | |
| 291 | epoll_create1 | |
| 292 | dup3 | |
| 293 | pipe2 | |
| 294 | inotify_init1 | |
| 295 | preadv | |
| 296 | pwritev | |
| 297 | rt_tgsigqueueinfo | |
| 298 | perf_event_open | |
| 299 | recvmmsg | |
| 300 | fanotify_init | |
| 301 | fanotify_mark | |
| 302 | prlimit64 | |
| 303 | name_to_handle_at | |
| 304 | open_by_handle_at | |
| 305 | clock_adjtime | |
| 306 | syncfs | |
| 307 | sendmmsg | |
| 308 | setns | |
| 309 | getcpu | |
| 310 | process_vm_readv | |
| 311 | process_vm_writev | |
| 312 | kcmp | |
| 313 | finit_module | |
| 314 | sched_setattr | |
| 315 | sched_getattr | |
| 316 | renameat2 | int renameat2(int oldfd, const char *old, int newfd, const char *new, unsigned flags) |
| 317 | seccomp | |
| 318 | getrandom | |
| 319 | memfd_create | |
| 320 | kexec_file_load | |
| 321 | bpf | |
| 322 | execveat | |
| 323 | userfaultfd | |
| 324 | membarrier | |
| 325 | mlock2 | |
| 326 | copy_file_range | |
| 327 | preadv2 | |
| 328 | pwritev2 | |
| 329 | pkey_mprotect | |
| 330 | pkey_alloc | |
| 331 | pkey_free | |
| 332 | statx | |
| 333 | io_pgetevents | |
| 334 | rseq | |
| 424 | pidfd_send_signal | |
| 425 | io_uring_setup | |
| 426 | io_uring_enter | |
| 427 | io_uring_register | |
| 428 | open_tree | |
| 429 | move_mount | |
| 430 | fsopen | |
| 431 | fsconfig | |
| 432 | fsmount | |
| 433 | fspick | |
| 434 | pidfd_open | |
| 435 | clone3 | |
| 436 | close_range | |
| 437 | openat2 | |
| 438 | pidfd_getfd | |
| 439 | faccessat2 | |
| 440 | process_madvise | |
| 441 | epoll_pwait2 | |
| 442 | mount_setattr | |
| 443 | quotactl_fd | |
| 444 | landlock_create_ruleset | |
| 445 | landlock_add_rule | |
| 446 | landlock_restrict_self | |
| 447 | memfd_secret | |
| 448 | process_mrelease | |
| 449 | futex_waitv | |
| 450 | set_mempolicy_home_node |
int rename(const char *old, const char *new);
syscall(SYS_rename, old, new);
syscall(SYS_renameat, AT_FDCWD, old, AT_FDCWD, new);
syscall(SYS_renameat2, AT_FDCWD, old, AT_FDCWD, new, 0);
- kcm -> Kernel Samepage Merging
- seccmp -> Secure Computing Mode
- seccomp.2
- 一种沙箱机制
- SECCOMP_MODE_FILTER
- 通过回调函数过滤 syscall
- 过滤器适用
BPF语言
- google/gvisor
- 拦截 syscall 实现容器隔离
- https://github.com/bminor/musl/blob/master/src/internal/syscall.h
FAQ
BPF vs eBPF
- BPF - Berkeley Packet Filter
- 1992年由Steven McCanne和Van Jacobson在BSD上实现
- 用于过滤网络数据包
- eBPF - extended Berkeley Packet Filter
- 2014年由Alexei Starovoitov在Linux内核中实现
- 用于过滤系统调用
- 提升内核监控和分析能力