src/lxc/process_utils.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #ifndef __LXC_PROCESS_UTILS_H
   4 #define __LXC_PROCESS_UTILS_H
   5
   6 #ifndef _GNU_SOURCE
   7 #define _GNU_SOURCE 1
   8 #endif
   9 #include <linux/sched.h>
  10 #include <sched.h>
  11 #include <signal.h>
  12 #include <stdbool.h>
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <sys/syscall.h>
  16 #include <unistd.h>
  17
  18 #include "compiler.h"
  19 #include "config.h"
  20 #include "syscall_numbers.h"
  21
  22 #ifndef CSIGNAL
  23 #define CSIGNAL 0x000000ff /* signal mask to be sent at exit */
  24 #endif
  25
  26 #ifndef CLONE_VM
  27 #define CLONE_VM 0x00000100 /* set if VM shared between processes */
  28 #endif
  29
  30 #ifndef CLONE_FS
  31 #define CLONE_FS 0x00000200 /* set if fs info shared between processes */
  32 #endif
  33
  34 #ifndef CLONE_FILES
  35 #define CLONE_FILES 0x00000400 /* set if open files shared between processes */
  36 #endif
  37
  38 #ifndef CLONE_SIGHAND
  39 #define CLONE_SIGHAND 0x00000800 /* set if signal handlers and blocked signals shared */
  40 #endif
  41
  42 #ifndef CLONE_PIDFD
  43 #define CLONE_PIDFD 0x00001000 /* set if a pidfd should be placed in parent */
  44 #endif
  45
  46 #ifndef CLONE_PTRACE
  47 #define CLONE_PTRACE 0x00002000 /* set if we want to let tracing continue on the child too */
  48 #endif
  49
  50 #ifndef CLONE_VFORK
  51 #define CLONE_VFORK 0x00004000 /* set if the parent wants the child to wake it up on mm_release */
  52 #endif
  53
  54 #ifndef CLONE_PARENT
  55 #define CLONE_PARENT 0x00008000 /* set if we want to have the same parent as the cloner */
  56 #endif
  57
  58 #ifndef CLONE_THREAD
  59 #define CLONE_THREAD 0x00010000 /* Same thread group? */
  60 #endif
  61
  62 #ifndef CLONE_NEWNS
  63 #define CLONE_NEWNS 0x00020000 /* New mount namespace group */
  64 #endif
  65
  66 #ifndef CLONE_SYSVSEM
  67 #define CLONE_SYSVSEM 0x00040000 /* share system V SEM_UNDO semantics */
  68 #endif
  69
  70 #ifndef CLONE_SETTLS
  71 #define CLONE_SETTLS 0x00080000 /* create a new TLS for the child */
  72 #endif
  73
  74 #ifndef CLONE_PARENT_SETTID
  75 #define CLONE_PARENT_SETTID 0x00100000 /* set the TID in the parent */
  76 #endif
  77
  78 #ifndef CLONE_CHILD_CLEARTID
  79 #define CLONE_CHILD_CLEARTID 0x00200000 /* clear the TID in the child */
  80 #endif
  81
  82 #ifndef CLONE_DETACHED
  83 #define CLONE_DETACHED 0x00400000 /* Unused, ignored */
  84 #endif
  85
  86 #ifndef CLONE_UNTRACED
  87 #define CLONE_UNTRACED 0x00800000 /* set if the tracing process can't force CLONE_PTRACE on this clone */
  88 #endif
  89
  90 #ifndef CLONE_CHILD_SETTID
  91 #define CLONE_CHILD_SETTID 0x01000000 /* set the TID in the child */
  92 #endif
  93
  94 #ifndef CLONE_NEWCGROUP
  95 #define CLONE_NEWCGROUP 0x02000000 /* New cgroup namespace */
  96 #endif
  97
  98 #ifndef CLONE_NEWUTS
  99 #define CLONE_NEWUTS 0x04000000 /* New utsname namespace */
 100 #endif
 101
 102 #ifndef CLONE_NEWIPC
 103 #define CLONE_NEWIPC 0x08000000 /* New ipc namespace */
 104 #endif
 105
 106 #ifndef CLONE_NEWUSER
 107 #define CLONE_NEWUSER 0x10000000 /* New user namespace */
 108 #endif
 109
 110 #ifndef CLONE_NEWPID
 111 #define CLONE_NEWPID 0x20000000 /* New pid namespace */
 112 #endif
 113
 114 #ifndef CLONE_NEWNET
 115 #define CLONE_NEWNET 0x40000000 /* New network namespace */
 116 #endif
 117
 118 #ifndef CLONE_IO
 119 #define CLONE_IO 0x80000000 /* Clone io context */
 120 #endif
 121
 122 /* Flags for the clone3() syscall. */
 123 #ifndef CLONE_CLEAR_SIGHAND
 124 #define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and reset to SIG_DFL. */
 125 #endif
 126
 127 #ifndef CLONE_INTO_CGROUP
 128 #define CLONE_INTO_CGROUP 0x200000000ULL /* Clone into a specific cgroup given the right permissions. */
 129 #endif
 130
 131 /*
 132  * cloning flags intersect with CSIGNAL so can be used with unshare and clone3
 133  * syscalls only:
 134  */
 135 #ifndef CLONE_NEWTIME
 136 #define CLONE_NEWTIME 0x00000080 /* New time namespace */
 137 #endif
 138
 139 /* waitid */
 140 #ifndef P_PIDFD
 141 #define P_PIDFD 3
 142 #endif
 143
 144 #ifndef CLONE_ARGS_SIZE_VER0
 145 #define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
 146 #endif
 147
 148 #ifndef CLONE_ARGS_SIZE_VER1
 149 #define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
 150 #endif
 151
 152 #ifndef CLONE_ARGS_SIZE_VER2
 153 #define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
 154 #endif
 155
 156 #ifndef ptr_to_u64
 157 #define ptr_to_u64(ptr) ((__u64)((uintptr_t)(ptr)))
 158 #endif
 159 #ifndef u64_to_ptr
 160 #define u64_to_ptr(x) ((void *)(uintptr_t)x)
 161 #endif
 162
 163 struct lxc_clone_args {
 164         __aligned_u64 flags;
 165         __aligned_u64 pidfd;
 166         __aligned_u64 child_tid;
 167         __aligned_u64 parent_tid;
 168         __aligned_u64 exit_signal;
 169         __aligned_u64 stack;
 170         __aligned_u64 stack_size;
 171         __aligned_u64 tls;
 172         __aligned_u64 set_tid;
 173         __aligned_u64 set_tid_size;
 174         __aligned_u64 cgroup;
 175 };
 176
 177 __returns_twice static inline pid_t lxc_clone3(struct lxc_clone_args *args, size_t size)
 178 {
 179         return syscall(__NR_clone3, args, size);
 180 }
 181
 182 #if defined(__ia64__)
 183 int __clone2(int (*__fn)(void *__arg), void *__child_stack_base,
 184              size_t __child_stack_size, int __flags, void *__arg, ...);
 185 #else
 186 int clone(int (*fn)(void *), void *child_stack, int flags, void *arg, ...
 187           /* pid_t *ptid, struct user_desc *tls, pid_t *ctid */);
 188 #endif
 189
 190 /**
 191  * lxc_clone() - create a new process
 192  *
 193  * - allocate stack:
 194  *   This function allocates a new stack the size of page and passes it to the
 195  *   kernel.
 196  *
 197  * - support all CLONE_*flags:
 198  *   This function supports all CLONE_* flags. If in doubt or not sufficiently
 199  *   familiar with process creation in the kernel and interactions with libcs
 200  *   this function should be used.
 201  *
 202  * - pthread_atfork() handlers depending on libc:
 203  *   Whether this function runs pthread_atfork() handlers depends on the
 204  *   corresponding libc wrapper. glibc currently does not run pthread_atfork()
 205  *   handlers but does not guarantee that they are not. Other libcs might or
 206  *   might not run pthread_atfork() handlers. If you require guarantees please
 207  *   refer to the lxc_raw_clone*() functions in process_utils.{c,h}.
 208  *
 209  * - should call lxc_raw_getpid():
 210  *   The child should use lxc_raw_getpid() to retrieve its pid.
 211  */
 212 __hidden extern pid_t lxc_clone(int (*fn)(void *), void *arg, int flags, int *pidfd);
 213
 214
 215 /*
 216  * lxc_raw_clone() - create a new process
 217  *
 218  * - fork() behavior:
 219  *   This function returns 0 in the child and > 0 in the parent.
 220  *
 221  * - copy-on-write:
 222  *   This function does not allocate a new stack and relies on copy-on-write
 223  *   semantics.
 224  *
 225  * - supports subset of ClONE_* flags:
 226  *   lxc_raw_clone() intentionally only supports a subset of the flags available
 227  *   to the actual system call. Please refer to the implementation what flags
 228  *   cannot be used. Also, please don't assume that just because a flag isn't
 229  *   explicitly checked for as being unsupported that it is supported. If in
 230  *   doubt or not sufficiently familiar with process creation in the kernel and
 231  *   interactions with libcs this function should be used.
 232  *
 233  * - no pthread_atfork() handlers:
 234  *   This function circumvents - as much as this this is possible - any libc
 235  *   wrappers and thus does not run any pthread_atfork() handlers. Make sure
 236  *   that this is safe to do in the context you are trying to call this
 237  *   function.
 238  *
 239  * - must call lxc_raw_getpid():
 240  *   The child must use lxc_raw_getpid() to retrieve its pid.
 241  */
 242 __hidden extern pid_t lxc_raw_clone(unsigned long flags, int *pidfd);
 243 __hidden extern pid_t lxc_raw_legacy_clone(unsigned long flags, int *pidfd);
 244
 245 /*
 246  * lxc_raw_clone_cb() - create a new process
 247  *
 248  * - non-fork() behavior:
 249  *   Function does return pid of the child or -1 on error. Pass in a callback
 250  *   function via the "fn" argument that gets executed in the child process.
 251  *   The "args" argument is passed to "fn".
 252  *
 253  * All other comments that apply to lxc_raw_clone() apply to lxc_raw_clone_cb()
 254  * as well.
 255  */
 256 __hidden extern pid_t lxc_raw_clone_cb(int (*fn)(void *), void *args, unsigned long flags,
 257                                        int *pidfd);
 258
 259 #ifndef HAVE_EXECVEAT
 260 static inline int execveat(int dirfd, const char *pathname, char *const argv[],
 261                            char *const envp[], int flags)
 262 {
 263         return syscall(__NR_execveat, dirfd, pathname, argv, envp, flags);
 264 }
 265 #else
 266 extern int execveat(int dirfd, const char *pathname, char *const argv[],
 267                     char *const envp[], int flags);
 268 #endif
 269
 270 /*
 271  * Because of older glibc's pid cache (up to 2.25) whenever clone() is called
 272  * the child must must retrieve it's own pid via lxc_raw_getpid().
 273  */
 274 static inline pid_t lxc_raw_getpid(void)
 275 {
 276         return (pid_t)syscall(SYS_getpid);
 277 }
 278
 279 static inline pid_t lxc_raw_gettid(void)
 280 {
 281 #if __NR_gettid > 0
 282         return syscall(__NR_gettid);
 283 #else
 284         return lxc_raw_getpid();
 285 #endif
 286 }
 287
 288 __hidden extern int lxc_raw_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
 289                                               unsigned int flags);
 290
 291 #endif /* __LXC_PROCESS_UTILS_H */