1  /* Check if clone (CLONE_THREAD) does not call exit_group (BZ #21512)
       2     Copyright (C) 2021-2023 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 <string.h>
      20  #include <sched.h>
      21  #include <signal.h>
      22  #include <unistd.h>
      23  #include <errno.h>
      24  #include <sys/syscall.h>
      25  #include <sys/wait.h>
      26  #include <sys/types.h>
      27  #include <linux/futex.h>
      28  #include <support/check.h>
      29  #include <stdatomic.h>
      30  #include <clone_internal.h>
      31  
      32  /* Test if clone call with CLONE_THREAD does not call exit_group.  The 'f'
      33     function returns '1', which will be used by clone thread to call the
      34     'exit' syscall directly.  If _exit is used instead, exit_group will be
      35     used and thus the thread group will finish with return value of '1'
      36     (where '2' from main thread is expected.).  */
      37  
      38  static int
      39  f (void *a)
      40  {
      41    return 1;
      42  }
      43  
      44  /* Futex wait for TID argument, similar to pthread_join internal
      45     implementation.  */
      46  #define wait_tid(ctid_ptr, ctid_val)					\
      47    do {									\
      48      __typeof (*(ctid_ptr)) __tid;					\
      49      /* We need acquire MO here so that we synchronize with the		\
      50         kernel's store to 0 when the clone terminates.  */		\
      51      while ((__tid = atomic_load_explicit (ctid_ptr,			\
      52  					  memory_order_acquire)) != 0)	\
      53        futex_wait (ctid_ptr, ctid_val);					\
      54    } while (0)
      55  
      56  static inline int
      57  futex_wait (int *futexp, int val)
      58  {
      59  #ifdef __NR_futex
      60    return syscall (__NR_futex, futexp, FUTEX_WAIT, val);
      61  #else
      62    return syscall (__NR_futex_time64, futexp, FUTEX_WAIT, val);
      63  #endif
      64  }
      65  
      66  static int
      67  do_test (void)
      68  {
      69    char st[1024] __attribute__ ((aligned));
      70    int clone_flags = CLONE_THREAD;
      71    /* Minimum required flags to used along with CLONE_THREAD.  */
      72    clone_flags |= CLONE_VM | CLONE_SIGHAND;
      73    /* We will used ctid to call on futex to wait for thread exit.  */
      74    clone_flags |= CLONE_CHILD_CLEARTID;
      75    /* Initialize with a known value.  ctid is set to zero by the kernel after the
      76       cloned thread has exited.  */
      77  #define CTID_INIT_VAL 1
      78    pid_t ctid = CTID_INIT_VAL;
      79    pid_t tid;
      80  
      81    struct clone_args clone_args =
      82      {
      83        .flags = clone_flags & ~CSIGNAL,
      84        .exit_signal = clone_flags & CSIGNAL,
      85        .stack = (uintptr_t) st,
      86        .stack_size = sizeof (st),
      87        .child_tid = (uintptr_t) &ctid,
      88      };
      89    tid = __clone_internal (&clone_args, f, NULL);
      90    if (tid == -1)
      91      FAIL_EXIT1 ("clone failed: %m");
      92  
      93    wait_tid (&ctid, CTID_INIT_VAL);
      94  
      95    return 2;
      96  }
      97  
      98  #define EXPECTED_STATUS 2
      99  #include <support/test-driver.c>