sysdeps/unix/sysv/linux/clone-internal.c

   1 /* The internal wrapper of clone and clone3.
   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 <sysdep.h>
  20 #include <stddef.h>
  21 #include <errno.h>
  22 #include <sched.h>
  23 #include <clone_internal.h>
  24 #include <libc-pointer-arith.h> /* For cast_to_pointer.  */
  25 #include <stackinfo.h>          /* For _STACK_GROWS_{UP,DOWN}.  */
  26
  27 #define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
  28 #define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
  29 #define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
  30
  31 #define sizeof_field(TYPE, MEMBER) sizeof ((((TYPE *)0)->MEMBER))
  32 #define offsetofend(TYPE, MEMBER) \
  33   (offsetof (TYPE, MEMBER) + sizeof_field (TYPE, MEMBER))
  34
  35 _Static_assert (__alignof (struct clone_args) == 8,
  36                 "__alignof (struct clone_args) != 8");
  37 _Static_assert (offsetofend (struct clone_args, tls) == CLONE_ARGS_SIZE_VER0,
  38                 "offsetofend (struct clone_args, tls) != CLONE_ARGS_SIZE_VER0");
  39 _Static_assert (offsetofend (struct clone_args, set_tid_size) == CLONE_ARGS_SIZE_VER1,
  40                 "offsetofend (struct clone_args, set_tid_size) != CLONE_ARGS_SIZE_VER1");
  41 _Static_assert (offsetofend (struct clone_args, cgroup) == CLONE_ARGS_SIZE_VER2,
  42                 "offsetofend (struct clone_args, cgroup) != CLONE_ARGS_SIZE_VER2");
  43 _Static_assert (sizeof (struct clone_args) == CLONE_ARGS_SIZE_VER2,
  44                 "sizeof (struct clone_args) != CLONE_ARGS_SIZE_VER2");
  45
  46 int
  47 __clone_internal_fallback (struct clone_args *cl_args,
  48                            int (*func) (void *arg), void *arg)
  49 {
  50   /* Map clone3 arguments to clone arguments.  NB: No need to check
  51      invalid clone3 specific bits in flags nor exit_signal since this
  52      is an internal function.  */
  53   int flags = cl_args->flags | cl_args->exit_signal;
  54   void *stack = cast_to_pointer (cl_args->stack);
  55   int ret;
  56
  57 #ifdef __ia64__
  58   ret = __clone2 (func, stack, cl_args->stack_size,
  59                   flags, arg,
  60                   cast_to_pointer (cl_args->parent_tid),
  61                   cast_to_pointer (cl_args->tls),
  62                   cast_to_pointer (cl_args->child_tid));
  63 #else
  64 # if !_STACK_GROWS_DOWN && !_STACK_GROWS_UP
  65 #  error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
  66 # endif
  67
  68 # if _STACK_GROWS_DOWN
  69   stack += cl_args->stack_size;
  70 # endif
  71   ret = __clone (func, stack, flags, arg,
  72                  cast_to_pointer (cl_args->parent_tid),
  73                  cast_to_pointer (cl_args->tls),
  74                  cast_to_pointer (cl_args->child_tid));
  75 #endif
  76   return ret;
  77 }
  78
  79 int
  80 __clone3_internal (struct clone_args *cl_args, int (*func) (void *args),
  81                    void *arg)
  82 {
  83 #ifdef HAVE_CLONE3_WRAPPER
  84 # if __ASSUME_CLONE3
  85   return __clone3 (cl_args, sizeof (*cl_args), func, arg);
  86 # else
  87   static int clone3_supported = 1;
  88   if (atomic_load_relaxed (&clone3_supported) == 1)
  89     {
  90       int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
  91       if (ret != -1 || errno != ENOSYS)
  92         return ret;
  93
  94       atomic_store_relaxed (&clone3_supported, 0);
  95     }
  96 # endif
  97 #endif
  98   __set_errno (ENOSYS);
  99   return -1;
 100 }
 101
 102 int
 103 __clone_internal (struct clone_args *cl_args,
 104                   int (*func) (void *arg), void *arg)
 105 {
 106 #ifdef HAVE_CLONE3_WRAPPER
 107   int saved_errno = errno;
 108   int ret = __clone3_internal (cl_args, func, arg);
 109   if (ret != -1 || errno != ENOSYS)
 110     return ret;
 111
 112   /* NB: Restore errno since errno may be checked against non-zero
 113      return value.  */
 114   __set_errno (saved_errno);
 115 #endif
 116
 117   return __clone_internal_fallback (cl_args, func, arg);
 118 }
 119
 120 libc_hidden_def (__clone_internal)