1 | #define _GNU_SOURCE
|
---|
2 | #include <spawn.h>
|
---|
3 | #include <sched.h>
|
---|
4 | #include <unistd.h>
|
---|
5 | #include <signal.h>
|
---|
6 | #include <fcntl.h>
|
---|
7 | #include <sys/wait.h>
|
---|
8 | #include "syscall.h"
|
---|
9 | #include "pthread_impl.h"
|
---|
10 | #include "fdop.h"
|
---|
11 | #include "libc.h"
|
---|
12 |
|
---|
13 | struct args {
|
---|
14 | int p[2];
|
---|
15 | sigset_t oldmask;
|
---|
16 | const char *path;
|
---|
17 | int (*exec)(const char *, char *const *, char *const *);
|
---|
18 | const posix_spawn_file_actions_t *fa;
|
---|
19 | const posix_spawnattr_t *restrict attr;
|
---|
20 | char *const *argv, *const *envp;
|
---|
21 | };
|
---|
22 |
|
---|
23 | void __get_handler_set(sigset_t *);
|
---|
24 |
|
---|
25 | static int __sys_dup2(int old, int new)
|
---|
26 | {
|
---|
27 | #ifdef SYS_dup2
|
---|
28 | return __syscall(SYS_dup2, old, new);
|
---|
29 | #else
|
---|
30 | if (old==new) {
|
---|
31 | int r = __syscall(SYS_fcntl, old, F_GETFD);
|
---|
32 | return r<0 ? r : old;
|
---|
33 | } else {
|
---|
34 | return __syscall(SYS_dup3, old, new, 0);
|
---|
35 | }
|
---|
36 | #endif
|
---|
37 | }
|
---|
38 |
|
---|
39 | static int child(void *args_vp)
|
---|
40 | {
|
---|
41 | int i, ret;
|
---|
42 | struct sigaction sa = {0};
|
---|
43 | struct args *args = args_vp;
|
---|
44 | int p = args->p[1];
|
---|
45 | const posix_spawn_file_actions_t *fa = args->fa;
|
---|
46 | const posix_spawnattr_t *restrict attr = args->attr;
|
---|
47 | sigset_t hset;
|
---|
48 |
|
---|
49 | close(args->p[0]);
|
---|
50 |
|
---|
51 | /* All signal dispositions must be either SIG_DFL or SIG_IGN
|
---|
52 | * before signals are unblocked. Otherwise a signal handler
|
---|
53 | * from the parent might get run in the child while sharing
|
---|
54 | * memory, with unpredictable and dangerous results. To
|
---|
55 | * reduce overhead, sigaction has tracked for us which signals
|
---|
56 | * potentially have a signal handler. */
|
---|
57 | __get_handler_set(&hset);
|
---|
58 | for (i=1; i<_NSIG; i++) {
|
---|
59 | if ((attr->__flags & POSIX_SPAWN_SETSIGDEF)
|
---|
60 | && sigismember(&attr->__def, i)) {
|
---|
61 | sa.sa_handler = SIG_DFL;
|
---|
62 | } else if (sigismember(&hset, i)) {
|
---|
63 | if (i-32<3U) {
|
---|
64 | sa.sa_handler = SIG_IGN;
|
---|
65 | } else {
|
---|
66 | __libc_sigaction(i, 0, &sa);
|
---|
67 | if (sa.sa_handler==SIG_IGN) continue;
|
---|
68 | sa.sa_handler = SIG_DFL;
|
---|
69 | }
|
---|
70 | } else {
|
---|
71 | continue;
|
---|
72 | }
|
---|
73 | __libc_sigaction(i, &sa, 0);
|
---|
74 | }
|
---|
75 |
|
---|
76 | if (attr->__flags & POSIX_SPAWN_SETSID)
|
---|
77 | if ((ret=__syscall(SYS_setsid)) < 0)
|
---|
78 | goto fail;
|
---|
79 |
|
---|
80 | if (attr->__flags & POSIX_SPAWN_SETPGROUP)
|
---|
81 | if ((ret=__syscall(SYS_setpgid, 0, attr->__pgrp)))
|
---|
82 | goto fail;
|
---|
83 |
|
---|
84 | /* Use syscalls directly because the library functions attempt
|
---|
85 | * to do a multi-threaded synchronized id-change, which would
|
---|
86 | * trash the parent's state. */
|
---|
87 | if (attr->__flags & POSIX_SPAWN_RESETIDS)
|
---|
88 | if ((ret=__syscall(SYS_setgid, __syscall(SYS_getgid))) ||
|
---|
89 | (ret=__syscall(SYS_setuid, __syscall(SYS_getuid))) )
|
---|
90 | goto fail;
|
---|
91 |
|
---|
92 | if (fa && fa->__actions) {
|
---|
93 | struct fdop *op;
|
---|
94 | int fd;
|
---|
95 | for (op = fa->__actions; op->next; op = op->next);
|
---|
96 | for (; op; op = op->prev) {
|
---|
97 | /* It's possible that a file operation would clobber
|
---|
98 | * the pipe fd used for synchronizing with the
|
---|
99 | * parent. To avoid that, we dup the pipe onto
|
---|
100 | * an unoccupied fd. */
|
---|
101 | if (op->fd == p) {
|
---|
102 | ret = __syscall(SYS_dup, p);
|
---|
103 | if (ret < 0) goto fail;
|
---|
104 | __syscall(SYS_close, p);
|
---|
105 | p = ret;
|
---|
106 | }
|
---|
107 | switch(op->cmd) {
|
---|
108 | case FDOP_CLOSE:
|
---|
109 | __syscall(SYS_close, op->fd);
|
---|
110 | break;
|
---|
111 | case FDOP_DUP2:
|
---|
112 | if ((ret=__sys_dup2(op->srcfd, op->fd))<0)
|
---|
113 | goto fail;
|
---|
114 | break;
|
---|
115 | case FDOP_OPEN:
|
---|
116 | fd = __sys_open(op->path, op->oflag, op->mode);
|
---|
117 | if ((ret=fd) < 0) goto fail;
|
---|
118 | if (fd != op->fd) {
|
---|
119 | if ((ret=__sys_dup2(fd, op->fd))<0)
|
---|
120 | goto fail;
|
---|
121 | __syscall(SYS_close, fd);
|
---|
122 | }
|
---|
123 | break;
|
---|
124 | }
|
---|
125 | }
|
---|
126 | }
|
---|
127 |
|
---|
128 | /* Close-on-exec flag may have been lost if we moved the pipe
|
---|
129 | * to a different fd. We don't use F_DUPFD_CLOEXEC above because
|
---|
130 | * it would fail on older kernels and atomicity is not needed --
|
---|
131 | * in this process there are no threads or signal handlers. */
|
---|
132 | __syscall(SYS_fcntl, p, F_SETFD, FD_CLOEXEC);
|
---|
133 |
|
---|
134 | pthread_sigmask(SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
|
---|
135 | ? &attr->__mask : &args->oldmask, 0);
|
---|
136 |
|
---|
137 | args->exec(args->path, args->argv, args->envp);
|
---|
138 | ret = -errno;
|
---|
139 |
|
---|
140 | fail:
|
---|
141 | /* Since sizeof errno < PIPE_BUF, the write is atomic. */
|
---|
142 | ret = -ret;
|
---|
143 | if (ret) while (__syscall(SYS_write, p, &ret, sizeof ret) < 0);
|
---|
144 | _exit(127);
|
---|
145 | }
|
---|
146 |
|
---|
147 |
|
---|
148 | int __posix_spawnx(pid_t *restrict res, const char *restrict path,
|
---|
149 | int (*exec)(const char *, char *const *, char *const *),
|
---|
150 | const posix_spawn_file_actions_t *fa,
|
---|
151 | const posix_spawnattr_t *restrict attr,
|
---|
152 | char *const argv[restrict], char *const envp[restrict])
|
---|
153 | {
|
---|
154 | pid_t pid;
|
---|
155 | char stack[1024+PATH_MAX];
|
---|
156 | int ec=0, cs;
|
---|
157 | struct args args;
|
---|
158 |
|
---|
159 | if (pipe2(args.p, O_CLOEXEC))
|
---|
160 | return errno;
|
---|
161 |
|
---|
162 | pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
|
---|
163 |
|
---|
164 | args.path = path;
|
---|
165 | args.exec = exec;
|
---|
166 | args.fa = fa;
|
---|
167 | args.attr = attr ? attr : &(const posix_spawnattr_t){0};
|
---|
168 | args.argv = argv;
|
---|
169 | args.envp = envp;
|
---|
170 | pthread_sigmask(SIG_BLOCK, SIGALL_SET, &args.oldmask);
|
---|
171 |
|
---|
172 | pid = __clone(child, stack+sizeof stack,
|
---|
173 | CLONE_VM|CLONE_VFORK|SIGCHLD, &args);
|
---|
174 | close(args.p[1]);
|
---|
175 |
|
---|
176 | if (pid > 0) {
|
---|
177 | if (read(args.p[0], &ec, sizeof ec) != sizeof ec) ec = 0;
|
---|
178 | else waitpid(pid, &(int){0}, 0);
|
---|
179 | } else {
|
---|
180 | ec = -pid;
|
---|
181 | }
|
---|
182 |
|
---|
183 | close(args.p[0]);
|
---|
184 |
|
---|
185 | if (!ec && res) *res = pid;
|
---|
186 |
|
---|
187 | pthread_sigmask(SIG_SETMASK, &args.oldmask, 0);
|
---|
188 | pthread_setcancelstate(cs, 0);
|
---|
189 |
|
---|
190 | return ec;
|
---|
191 | }
|
---|
192 |
|
---|
193 | int posix_spawn(pid_t *restrict res, const char *restrict path,
|
---|
194 | const posix_spawn_file_actions_t *fa,
|
---|
195 | const posix_spawnattr_t *restrict attr,
|
---|
196 | char *const argv[restrict], char *const envp[restrict])
|
---|
197 | {
|
---|
198 | return __posix_spawnx(res, path, execve, fa, attr, argv, envp);
|
---|
199 | }
|
---|