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       1                 :            : /* SPDX-License-Identifier: LGPL-2.1+ */
       2                 :            : #pragma once
       3                 :            : 
       4                 :            : /***
       5                 :            :   Copyright © 2016 Michael Karcher
       6                 :            : ***/
       7                 :            : 
       8                 :            : #include <errno.h>
       9                 :            : #include <sched.h>
      10                 :            : #include <sys/syscall.h>
      11                 :            : 
      12                 :            : #include "log.h"
      13                 :            : #include "macro.h"
      14                 :            : 
      15                 :            : /**
      16                 :            :  * raw_clone() - uses clone to create a new process with clone flags
      17                 :            :  * @flags: Flags to pass to the clone system call
      18                 :            :  *
      19                 :            :  * Uses the clone system call to create a new process with the cloning flags and termination signal passed in the flags
      20                 :            :  * parameter. Opposed to glibc's clone function, using this function does not set up a separate stack for the child, but
      21                 :            :  * relies on copy-on-write semantics on the one stack at a common virtual address, just as fork does.
      22                 :            :  *
      23                 :            :  * To obtain copy-on-write semantics, flags must not contain CLONE_VM, and thus CLONE_THREAD and CLONE_SIGHAND (which
      24                 :            :  * require CLONE_VM) are not usable.
      25                 :            :  *
      26                 :            :  * Additionally, as this function does not pass the ptid, newtls and ctid parameters to the kernel, flags must not
      27                 :            :  * contain CLONE_PARENT_SETTID, CLONE_CHILD_SETTID, CLONE_CHILD_CLEARTID or CLONE_SETTLS.
      28                 :            :  *
      29                 :            :  * Returns: 0 in the child process and the child process id in the parent.
      30                 :            :  */
      31                 :          8 : static inline pid_t raw_clone(unsigned long flags) {
      32                 :            :         pid_t ret;
      33                 :            : 
      34         [ -  + ]:          8 :         assert((flags & (CLONE_VM|CLONE_PARENT_SETTID|CLONE_CHILD_SETTID|
      35                 :            :                          CLONE_CHILD_CLEARTID|CLONE_SETTLS)) == 0);
      36                 :            : #if defined(__s390x__) || defined(__s390__) || defined(__CRIS__)
      37                 :            :         /* On s390/s390x and cris the order of the first and second arguments
      38                 :            :          * of the raw clone() system call is reversed. */
      39                 :            :         ret = (pid_t) syscall(__NR_clone, NULL, flags);
      40                 :            : #elif defined(__sparc__)
      41                 :            :         {
      42                 :            :                 /**
      43                 :            :                  * sparc always returns the other process id in %o0, and
      44                 :            :                  * a boolean flag whether this is the child or the parent in
      45                 :            :                  * %o1. Inline assembly is needed to get the flag returned
      46                 :            :                  * in %o1.
      47                 :            :                  */
      48                 :            :                 int in_child, child_pid, error;
      49                 :            : 
      50                 :            :                 asm volatile("mov %3, %%g1\n\t"
      51                 :            :                              "mov %4, %%o0\n\t"
      52                 :            :                              "mov 0 , %%o1\n\t"
      53                 :            : #if defined(__arch64__)
      54                 :            :                              "t 0x6d\n\t"
      55                 :            : #else
      56                 :            :                              "t 0x10\n\t"
      57                 :            : #endif
      58                 :            :                              "addx %%g0, 0, %2\n\t"
      59                 :            :                              "mov %%o1, %0\n\t"
      60                 :            :                              "mov %%o0, %1" :
      61                 :            :                              "=r"(in_child), "=r"(child_pid), "=r"(error) :
      62                 :            :                              "i"(__NR_clone), "r"(flags) :
      63                 :            :                              "%o1", "%o0", "%g1", "cc" );
      64                 :            : 
      65                 :            :                 if (error) {
      66                 :            :                         errno = child_pid;
      67                 :            :                         ret = -1;
      68                 :            :                 } else
      69                 :            :                         ret = in_child ? 0 : child_pid;
      70                 :            :         }
      71                 :            : #else
      72                 :          8 :         ret = (pid_t) syscall(__NR_clone, flags, NULL);
      73                 :            : #endif
      74                 :            : 
      75         [ -  + ]:          8 :         if (ret == 0)
      76                 :          0 :                 reset_cached_pid();
      77                 :            : 
      78                 :          8 :         return ret;
      79                 :            : }