sysdeps/mach/hurd/i386/htl/pt-setup.c

   1 /* Setup thread stack.  Hurd/i386 version.
   2    Copyright (C) 2000-2021 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 <stdint.h>
  20 #include <assert.h>
  21 #include <mach.h>
  22
  23 #include <pt-internal.h>
  24
  25 /* The stack layout used on the i386 is:
  26
  27     -----------------
  28    |  ARG            |
  29     -----------------
  30    |  START_ROUTINE  |
  31     -----------------
  32    |  0              |
  33     -----------------
  34  */
  35
  36 /* Set up the stack for THREAD, such that it appears as if
  37    START_ROUTINE and ARG were passed to the new thread's entry-point.
  38    Return the stack pointer for the new thread.  */
  39 static void *
  40 stack_setup (struct __pthread *thread,
  41              void *(*start_routine) (void *), void *arg)
  42 {
  43   error_t err;
  44   uintptr_t *bottom, *top;
  45
  46   /* Calculate the top of the new stack.  */
  47   bottom = thread->stackaddr;
  48   top = (uintptr_t *) ((uintptr_t) bottom + thread->stacksize
  49                        + ((thread->guardsize + __vm_page_size - 1)
  50                           / __vm_page_size) * __vm_page_size);
  51
  52   if (start_routine != NULL)
  53     {
  54       /* And then the call frame.  */
  55       top -= 3;
  56       top = (uintptr_t *) ((uintptr_t) top & ~0xf);
  57       top[2] = (uintptr_t) arg; /* Argument to START_ROUTINE.  */
  58       top[1] = (uintptr_t) start_routine;
  59       top[0] = (uintptr_t) thread;
  60       *--top = 0;               /* Fake return address.  */
  61     }
  62
  63   if (thread->guardsize)
  64     {
  65       err = __vm_protect (__mach_task_self (), (vm_address_t) bottom,
  66                           thread->guardsize, 0, 0);
  67       assert_perror (err);
  68     }
  69
  70   return top;
  71 }
  72
  73 int
  74 __pthread_setup (struct __pthread *thread,
  75                  void (*entry_point) (struct __pthread *, void *(*)(void *),
  76                                       void *), void *(*start_routine) (void *),
  77                  void *arg)
  78 {
  79   tcbhead_t *tcb;
  80   error_t err;
  81   mach_port_t ktid;
  82
  83   thread->mcontext.pc = entry_point;
  84   thread->mcontext.sp = stack_setup (thread, start_routine, arg);
  85
  86   ktid = __mach_thread_self ();
  87   if (thread->kernel_thread == ktid)
  88     /* Fix up the TCB for the main thread.  The C library has already
  89        installed a TCB, which we want to keep using.  This TCB must not
  90        be freed so don't register it in the thread structure.  On the
  91        other hand, it's not yet possible to reliably release a TCB.
  92        Leave the unused one registered so that it doesn't leak.  The
  93        only thing left to do is to correctly set the `self' member in
  94        the already existing TCB.  */
  95     tcb = THREAD_SELF;
  96   else
  97     {
  98       err = __thread_set_pcsptp (thread->kernel_thread,
  99                                  1, thread->mcontext.pc,
 100                                  1, thread->mcontext.sp,
 101                                  1, thread->tcb);
 102       assert_perror (err);
 103       tcb = thread->tcb;
 104     }
 105   __mach_port_deallocate (__mach_task_self (), ktid);
 106
 107   tcb->self = thread->kernel_thread;
 108
 109   return 0;
 110 }