1/* Wait for process to change state. Linux version.
2 Copyright (C) 2019-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <sys/wait.h>
20#include <sys/resource.h>
21#include <sysdep-cancel.h>
22
23pid_t
24__wait4 (pid_t pid, int *stat_loc, int options, struct rusage *usage)
25{
26#ifdef __NR_wait4
27 return SYSCALL_CANCEL (wait4, pid, stat_loc, options, usage);
28#elif defined (__ASSUME_WAITID_PID0_P_PGID)
29 idtype_t idtype = P_PID;
30
31 if (pid < -1)
32 {
33 idtype = P_PGID;
34 pid *= -1;
35 }
36 else if (pid == -1)
37 idtype = P_ALL;
38 else if (pid == 0)
39 idtype = P_PGID;
40
41 options |= WEXITED;
42
43 siginfo_t infop;
44 if (SYSCALL_CANCEL (waitid, idtype, pid, &infop, options, usage) < 0)
45 return -1;
46
47 if (stat_loc)
48 {
49 switch (infop.si_code)
50 {
51 case CLD_EXITED:
52 *stat_loc = W_EXITCODE (infop.si_status, 0);
53 break;
54 case CLD_DUMPED:
55 *stat_loc = WCOREFLAG | infop.si_status;
56 break;
57 case CLD_KILLED:
58 *stat_loc = infop.si_status;
59 break;
60 case CLD_TRAPPED:
61 case CLD_STOPPED:
62 *stat_loc = W_STOPCODE (infop.si_status);
63 break;
64 case CLD_CONTINUED:
65 *stat_loc = __W_CONTINUED;
66 break;
67 default:
68 *stat_loc = 0;
69 break;
70 }
71 }
72
73 return infop.si_pid;
74# else
75/* Linux waitid prior kernel 5.4 does not support waiting for the current
76 process. It is possible to emulate wait4 it by calling getpgid for
77 PID 0, however, it would require an additional syscall and it is inherent
78 racy: after the current process group is received and before it is passed
79 to waitid a signal could arrive causing the current process group to
80 change. */
81# error "The kernel ABI does not provide a way to implement wait4"
82#endif
83}
84libc_hidden_def (__wait4);
85weak_alias (__wait4, wait4)
86