1  /* Setup thread stack.  Hurd/i386 version.
       2     Copyright (C) 2000-2023 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 <stdint.h>
      20  #include <assert.h>
      21  #include <mach.h>
      22  #include <hurd.h>
      23  
      24  #include <pt-internal.h>
      25  
      26  /* The stack layout used on the x86 is:
      27  
      28      -----------------
      29     |  ARG            |
      30      -----------------
      31     |  START_ROUTINE  |
      32      -----------------
      33     |  0              |
      34      -----------------
      35   */
      36  
      37  /* Set up the stack for THREAD, such that it appears as if
      38     START_ROUTINE and ARG were passed to the new thread's entry-point.
      39     Return the stack pointer for the new thread.  */
      40  static void *
      41  stack_setup (struct __pthread *thread,
      42  	     void *(*start_routine) (void *), void *arg)
      43  {
      44    error_t err;
      45    uintptr_t *bottom, *top;
      46  
      47    /* Calculate the top of the new stack.  */
      48    bottom = thread->stackaddr;
      49    top = (uintptr_t *) ((uintptr_t) bottom + thread->stacksize
      50  		       + ((thread->guardsize + __vm_page_size - 1)
      51  			  / __vm_page_size) * __vm_page_size);
      52  
      53    if (start_routine != NULL)
      54      {
      55        /* And then the call frame.  */
      56        top -= 3;
      57        top = (uintptr_t *) ((uintptr_t) top & ~0xf);
      58        top[2] = (uintptr_t) arg;	/* Argument to START_ROUTINE.  */
      59        top[1] = (uintptr_t) start_routine;
      60        top[0] = (uintptr_t) thread;
      61        *--top = 0;		/* Fake return address.  */
      62      }
      63  
      64    if (thread->guardsize)
      65      {
      66        err = __vm_protect (__mach_task_self (), (vm_address_t) bottom,
      67  			  thread->guardsize, 0, 0);
      68        assert_perror (err);
      69      }
      70  
      71    return top;
      72  }
      73  
      74  int
      75  __pthread_setup (struct __pthread *thread,
      76  		 void (*entry_point) (struct __pthread *, void *(*)(void *),
      77  				      void *), void *(*start_routine) (void *),
      78  		 void *arg)
      79  {
      80    error_t err;
      81  
      82    if (thread->kernel_thread == __hurd_thread_self ())
      83      /* Fix up the TCB for the main thread.  The C library has already
      84         installed a TCB, which we want to keep using.  This TCB must not
      85         be freed so don't register it in the thread structure.  On the
      86         other hand, it's not yet possible to reliably release a TCB.
      87         Leave the unused one registered so that it doesn't leak.  */
      88      return 0;
      89  
      90    thread->mcontext.pc = entry_point;
      91    thread->mcontext.sp = stack_setup (thread, start_routine, arg);
      92  
      93    err = __thread_set_pcsptp (thread->kernel_thread,
      94  			     1, thread->mcontext.pc,
      95  			     1, thread->mcontext.sp,
      96  			     1, thread->tcb);
      97    assert_perror (err);
      98  
      99    return 0;
     100  }