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++ /****************************************************************************
++ **
++ ** Copyright (C) 2020 Intel Corporation.
++ **
++ ** Permission is hereby granted, free of charge, to any person obtaining a copy
++ ** of this software and associated documentation files (the "Software"), to deal
++ ** in the Software without restriction, including without limitation the rights
++ ** to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
++ ** copies of the Software, and to permit persons to whom the Software is
++ ** furnished to do so, subject to the following conditions:
++ **
++ ** The above copyright notice and this permission notice shall be included in
++ ** all copies or substantial portions of the Software.
++ **
++ ** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
++ ** IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
++ ** FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
++ ** AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
++ ** LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
++ ** OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
++ ** THE SOFTWARE.
++ **
++ ****************************************************************************/
++
++ #ifndef _GNU_SOURCE
++ # define _GNU_SOURCE
++ #endif
++
++ #include "forkfd.h"
++
++ #include <errno.h>
++ #include <fcntl.h>
++ #include <limits.h>
++ #include <sched.h>
++ #include <signal.h>
++ #include <stdio.h>
++ #include <stdlib.h>
++ #include <string.h>
++ #include <sys/resource.h>
++ #include <sys/syscall.h>
++ #include <sys/types.h>
++ #include <sys/wait.h>
++ #include <unistd.h>
++
++ #include "forkfd_atomic.h"
++
++ #ifndef CLONE_PIDFD
++ # define CLONE_PIDFD 0x00001000
++ #endif
++ #ifndef P_PIDFD
++ # define P_PIDFD 3
++ #endif
++
++ #define SYSTEM_FORKFD_CAN_VFORK
++
++ // in forkfd.c
++ static int convertForkfdWaitFlagsToWaitFlags(int ffdoptions);
++ static void convertStatusToForkfdInfo(int status, struct forkfd_info *info);
++
++ static ffd_atomic_int system_forkfd_state = FFD_ATOMIC_INIT(0);
++
++ static int sys_waitid(int which, int pid_or_pidfd, siginfo_t *infop, int options,
++ struct rusage *ru)
++ {
++ /* use the waitid raw system call, which has an extra parameter that glibc
++ * doesn't offer to us */
++ return syscall(__NR_waitid, which, pid_or_pidfd, infop, options, ru);
++ }
++
++ static int sys_clone(unsigned long cloneflags, int *ptid)
++ {
++ void *child_stack = NULL;
++ int *ctid = NULL;
++ unsigned long newtls = 0;
++ #if defined(__NR_clone2)
++ size_t stack_size = 0;
++ return syscall(__NR_clone2, cloneflags, child_stack, stack_size, ptid, ctid, newtls);
++ #elif defined(__cris__) || defined(__s390__)
++ /* a.k.a., CONFIG_CLONE_BACKWARDS2 architectures */
++ return syscall(__NR_clone, child_stack, cloneflags, ptid, newtls, ctid);
++ #elif defined(__microblaze__)
++ /* a.k.a., CONFIG_CLONE_BACKWARDS3 architectures */
++ size_t stack_size = 0;
++ return syscall(__NR_clone, cloneflags, child_stack, stack_size, ptid, newtls, ctid);
++ #elif defined(__arc__) || defined(__arm__) || defined(__aarch64__) || defined(__mips__) || \
++ defined(__nds32__) || defined(__hppa__) || defined(__powerpc__) || defined(__i386__) || \
++ defined(__x86_64__) || defined(__xtensa__) || defined(__alpha__) || defined(__riscv) || \
++ defined(__loongarch__) || defined(__sparc__) || defined(__m68k__)
++ /* ctid and newtls are inverted on CONFIG_CLONE_BACKWARDS architectures,
++ * but since both values are 0, there's no harm. */
++ return syscall(__NR_clone, cloneflags, child_stack, ptid, ctid, newtls);
++ #else
++ (void) child_stack;
++ (void) ctid;
++ (void) newtls;
++ errno = ENOSYS;
++ return -1;
++ #endif
++ }
++
++ static int detect_clone_pidfd_support()
++ {
++ /*
++ * Detect support for CLONE_PIDFD and P_PIDFD. Support was added in steps:
++ * - Linux 5.2 added CLONE_PIDFD support in clone(2) system call
++ * - Linux 5.2 added pidfd_send_signal(2)
++ * - Linux 5.3 added support for poll(2) on pidfds
++ * - Linux 5.3 added clone3(2)
++ * - Linux 5.4 added P_PIDFD support in waitid(2)
++ *
++ * We need CLONE_PIDFD and the poll(2) support. We could emulate the
++ * P_PIDFD support by reading the PID from /proc/self/fdinfo/n, which works
++ * in Linux 5.2, but without poll(2), we can't guarantee the functionality
++ * anyway.
++ *
++ * So we detect by trying to waitid(2) on a positive file descriptor that
++ * is definitely closed (INT_MAX). If P_PIDFD is supported, waitid(2) will
++ * return EBADF. If it isn't supported, it returns EINVAL (as it would for
++ * a negative file descriptor). This will succeed on Linux 5.4.
++ *
++ * We could have instead detected by the existence of the clone3(2) system
++ * call, but for that we would have needed to wait for __NR_clone3 to show
++ * up on the libcs. We choose to go via the waitid(2) route, which requires
++ * platform-independent constants only. It would have simplified the
++ * sys_clone() mess above...
++ */
++
++ sys_waitid(P_PIDFD, INT_MAX, NULL, WEXITED|WNOHANG, NULL);
++ return errno == EBADF ? 1 : -1;
++ }
++
++ int system_has_forkfd()
++ {
++ return ffd_atomic_load(&system_forkfd_state, FFD_ATOMIC_RELAXED) > 0;
++ }
++
++ static int system_forkfd_availability(void)
++ {
++ int state = ffd_atomic_load(&system_forkfd_state, FFD_ATOMIC_RELAXED);
++ if (state == 0) {
++ state = detect_clone_pidfd_support();
++ ffd_atomic_store(&system_forkfd_state, state, FFD_ATOMIC_RELAXED);
++ }
++ return state;
++ }
++
++ static int system_forkfd_pidfd_set_flags(int pidfd, int flags)
++ {
++ if ((flags & FFD_CLOEXEC) == 0) {
++ /* pidfd defaults to O_CLOEXEC */
++ fcntl(pidfd, F_SETFD, 0);
++ }
++ if (flags & FFD_NONBLOCK)
++ fcntl(pidfd, F_SETFL, fcntl(pidfd, F_GETFL) | O_NONBLOCK);
++ return pidfd;
++ }
++
++ int system_vforkfd(int flags, pid_t *ppid, int (*childFn)(void *), void *token, int *system)
++ {
++ __attribute__((aligned(64))) char childStack[SIGSTKSZ];
++ pid_t pid;
++ int pidfd;
++ unsigned long cloneflags = CLONE_PIDFD | CLONE_VFORK | CLONE_VM | SIGCHLD;
++
++ int state = system_forkfd_availability();
++ if (state < 0) {
++ *system = 0;
++ return state;
++ }
++ *system = 1;
++
++ pid = clone(childFn, childStack + sizeof(childStack), cloneflags, token, &pidfd, NULL, NULL);
++ if (pid < 0)
++ return pid;
++ if (ppid)
++ *ppid = pid;
++ return system_forkfd_pidfd_set_flags(pidfd, flags);
++ }
++
++ int system_forkfd(int flags, pid_t *ppid, int *system)
++ {
++ pid_t pid;
++ int pidfd;
++
++ int state = system_forkfd_availability();
++ if (state < 0) {
++ *system = 0;
++ return state;
++ }
++
++ *system = 1;
++ unsigned long cloneflags = CLONE_PIDFD | SIGCHLD;
++ pid = sys_clone(cloneflags, &pidfd);
++ if (pid < 0)
++ return pid;
++ if (ppid)
++ *ppid = pid;
++
++ if (pid == 0) {
++ /* Child process */
++ return FFD_CHILD_PROCESS;
++ }
++
++ /* parent process */
++ return system_forkfd_pidfd_set_flags(pidfd, flags);
++ }
++
++ int system_forkfd_wait(int ffd, struct forkfd_info *info, int ffdoptions, struct rusage *rusage)
++ {
++ siginfo_t si;
++ int ret;
++ int options = convertForkfdWaitFlagsToWaitFlags(ffdoptions);
++
++ if ((options & WNOHANG) == 0) {
++ /* check if the file descriptor is non-blocking */
++ ret = fcntl(ffd, F_GETFL);
++ if (ret == -1)
++ return ret;
++ if (ret & O_NONBLOCK)
++ options |= WNOHANG;
++ }
++
++ si.si_status = si.si_code = 0;
++ ret = sys_waitid(P_PIDFD, ffd, &si, options, rusage);
++ if (info) {
++ info->code = si.si_code;
++ info->status = si.si_status;
++ }
++ return ret;
++ }