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

   1 /* The internal wrapper of clone and clone3.
   2    Copyright (C) 2021-2024 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 #if !_STACK_GROWS_DOWN && !_STACK_GROWS_UP
  58 # error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
  59 #endif
  60
  61 #if _STACK_GROWS_DOWN
  62   stack += cl_args->stack_size;
  63 #endif
  64   ret = __clone (func, stack, flags, arg,
  65                  cast_to_pointer (cl_args->parent_tid),
  66                  cast_to_pointer (cl_args->tls),
  67                  cast_to_pointer (cl_args->child_tid));
  68   return ret;
  69 }
  70
  71 int
  72 __clone3_internal (struct clone_args *cl_args, int (*func) (void *args),
  73                    void *arg)
  74 {
  75 #ifdef HAVE_CLONE3_WRAPPER
  76 # if __ASSUME_CLONE3
  77   return __clone3 (cl_args, sizeof (*cl_args), func, arg);
  78 # else
  79   static int clone3_supported = 1;
  80   if (atomic_load_relaxed (&clone3_supported) == 1)
  81     {
  82       int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
  83       if (ret != -1 || errno != ENOSYS)
  84         return ret;
  85
  86       atomic_store_relaxed (&clone3_supported, 0);
  87     }
  88 # endif
  89 #endif
  90   __set_errno (ENOSYS);
  91   return -1;
  92 }
  93
  94 int
  95 __clone_internal (struct clone_args *cl_args,
  96                   int (*func) (void *arg), void *arg)
  97 {
  98 #ifdef HAVE_CLONE3_WRAPPER
  99   int saved_errno = errno;
 100   int ret = __clone3_internal (cl_args, func, arg);
 101   if (ret != -1 || errno != ENOSYS)
 102     return ret;
 103
 104   /* NB: Restore errno since errno may be checked against non-zero
 105      return value.  */
 106   __set_errno (saved_errno);
 107 #endif
 108
 109   return __clone_internal_fallback (cl_args, func, arg);
 110 }
 111
 112 libc_hidden_def (__clone_internal)