]>
Commit | Line | Data |
---|---|---|
43c6afee CB |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | #define _GNU_SOURCE | |
4 | #include <err.h> | |
5 | #include <errno.h> | |
6 | #include <fcntl.h> | |
7 | #include <inttypes.h> | |
8 | #include <limits.h> | |
9 | #include <sched.h> | |
10 | #include <signal.h> | |
11 | #include <stdio.h> | |
12 | #include <stdlib.h> | |
13 | #include <string.h> | |
14 | #include <sys/stat.h> | |
15 | #include <sys/syscall.h> | |
16 | #include <sys/types.h> | |
17 | #include <sys/wait.h> | |
18 | #include <unistd.h> | |
19 | ||
20 | #ifndef CLONE_PIDFD | |
21 | #define CLONE_PIDFD 0x00001000 | |
22 | #endif | |
23 | ||
7c33277b GR |
24 | #ifndef __NR_pidfd_send_signal |
25 | #define __NR_pidfd_send_signal -1 | |
26 | #endif | |
27 | ||
43c6afee CB |
28 | static int do_child(void *args) |
29 | { | |
30 | printf("%d\n", getpid()); | |
31 | _exit(EXIT_SUCCESS); | |
32 | } | |
33 | ||
34 | static pid_t pidfd_clone(int flags, int *pidfd) | |
35 | { | |
36 | size_t stack_size = 1024; | |
37 | char *stack[1024] = { 0 }; | |
38 | ||
39 | #ifdef __ia64__ | |
40 | return __clone2(do_child, stack, stack_size, flags | SIGCHLD, NULL, pidfd); | |
41 | #else | |
42 | return clone(do_child, stack + stack_size, flags | SIGCHLD, NULL, pidfd); | |
43 | #endif | |
44 | } | |
45 | ||
46 | static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info, | |
47 | unsigned int flags) | |
48 | { | |
49 | return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags); | |
50 | } | |
51 | ||
52 | static int pidfd_metadata_fd(pid_t pid, int pidfd) | |
53 | { | |
54 | int procfd, ret; | |
55 | char path[100]; | |
56 | ||
57 | snprintf(path, sizeof(path), "/proc/%d", pid); | |
58 | procfd = open(path, O_DIRECTORY | O_RDONLY | O_CLOEXEC); | |
59 | if (procfd < 0) { | |
60 | warn("Failed to open %s\n", path); | |
61 | return -1; | |
62 | } | |
63 | ||
64 | /* | |
65 | * Verify that the pid has not been recycled and our /proc/<pid> handle | |
66 | * is still valid. | |
67 | */ | |
68 | ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0); | |
69 | if (ret < 0) { | |
70 | switch (errno) { | |
71 | case EPERM: | |
72 | /* Process exists, just not allowed to signal it. */ | |
73 | break; | |
74 | default: | |
75 | warn("Failed to signal process\n"); | |
76 | close(procfd); | |
77 | procfd = -1; | |
78 | } | |
79 | } | |
80 | ||
81 | return procfd; | |
82 | } | |
83 | ||
84 | int main(int argc, char *argv[]) | |
85 | { | |
86 | int pidfd = 0, ret = EXIT_FAILURE; | |
87 | char buf[4096] = { 0 }; | |
88 | pid_t pid; | |
89 | int procfd, statusfd; | |
90 | ssize_t bytes; | |
91 | ||
92 | pid = pidfd_clone(CLONE_PIDFD, &pidfd); | |
93 | if (pid < 0) | |
94 | exit(ret); | |
95 | ||
96 | procfd = pidfd_metadata_fd(pid, pidfd); | |
97 | close(pidfd); | |
98 | if (procfd < 0) | |
99 | goto out; | |
100 | ||
101 | statusfd = openat(procfd, "status", O_RDONLY | O_CLOEXEC); | |
102 | close(procfd); | |
103 | if (statusfd < 0) | |
104 | goto out; | |
105 | ||
106 | bytes = read(statusfd, buf, sizeof(buf)); | |
107 | if (bytes > 0) | |
108 | bytes = write(STDOUT_FILENO, buf, bytes); | |
109 | close(statusfd); | |
110 | ret = EXIT_SUCCESS; | |
111 | ||
112 | out: | |
113 | (void)wait(NULL); | |
114 | ||
115 | exit(ret); | |
116 | } |