hurd/hurdstartup.c

   1 /* Initial program startup for running under the GNU Hurd.
   2    Copyright (C) 1991-2017 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    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <stdlib.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <hurd.h>
  24 #include <hurd/exec_startup.h>
  25 #include <sysdep.h>
  26 #include <hurd/threadvar.h>
  27 #include <unistd.h>
  28 #include <elf.h>
  29 #include <set-hooks.h>
  30 #include "hurdstartup.h"
  31 #include <argz.h>
  32
  33 mach_port_t *_hurd_init_dtable;
  34 mach_msg_type_number_t _hurd_init_dtablesize;
  35
  36 extern void __mach_init (void);
  37
  38 /* Entry point.  This is the first thing in the text segment.
  39
  40    The exec server started the initial thread in our task with this spot the
  41    PC, and a stack that is presumably big enough.  We do basic Mach
  42    initialization so mig-generated stubs work, and then do an exec_startup
  43    RPC on our bootstrap port, to which the exec server responds with the
  44    information passed in the exec call, as well as our original bootstrap
  45    port, and the base address and size of the preallocated stack.
  46
  47    If using cthreads, we are given a new stack by cthreads initialization and
  48    deallocate the stack set up by the exec server.  On the new stack we call
  49    `start1' (above) to do the rest of the startup work.  Since the stack may
  50    disappear out from under us in a machine-dependent way, we use a pile of
  51    static variables to communicate the information from exec_startup to start1.
  52    This is unfortunate but preferable to machine-dependent frobnication to copy
  53    the state from the old stack to the new one.  */
  54
  55
  56 void
  57 _hurd_startup (void **argptr, void (*main) (intptr_t *data))
  58 {
  59   error_t err;
  60   mach_port_t in_bootstrap;
  61   char *args, *env;
  62   mach_msg_type_number_t argslen, envlen;
  63   struct hurd_startup_data data;
  64   char **argv, **envp;
  65   int argc, envc;
  66   intptr_t *argcptr;
  67   vm_address_t addr;
  68
  69   /* Attempt to map page zero redzoned before we receive any RPC
  70      data that might get allocated there.  We can ignore errors.  */
  71   addr = 0;
  72   __vm_map (__mach_task_self (),
  73             &addr, __vm_page_size, 0, 0, MACH_PORT_NULL, 0, 1,
  74             VM_PROT_NONE, VM_PROT_NONE, VM_INHERIT_COPY);
  75
  76   if (err = __task_get_special_port (__mach_task_self (), TASK_BOOTSTRAP_PORT,
  77                                      &in_bootstrap))
  78     LOSE;
  79
  80   if (in_bootstrap != MACH_PORT_NULL)
  81     {
  82       /* Call the exec server on our bootstrap port and
  83          get all our standard information from it.  */
  84
  85       argslen = envlen = 0;
  86       data.dtablesize = data.portarraysize = data.intarraysize = 0;
  87
  88       err = __exec_startup_get_info (in_bootstrap,
  89                                      &data.user_entry,
  90                                      &data.phdr, &data.phdrsz,
  91                                      &data.stack_base, &data.stack_size,
  92                                      &data.flags,
  93                                      &args, &argslen,
  94                                      &env, &envlen,
  95                                      &data.dtable, &data.dtablesize,
  96                                      &data.portarray, &data.portarraysize,
  97                                      &data.intarray, &data.intarraysize);
  98       __mach_port_deallocate (__mach_task_self (), in_bootstrap);
  99     }
 100
 101   if (err || in_bootstrap == MACH_PORT_NULL || (data.flags & EXEC_STACK_ARGS))
 102     {
 103       /* Either we have no bootstrap port, or the RPC to the exec server
 104          failed, or whoever started us up passed the flag saying args are
 105          on the stack.  Try to snarf the args in the canonical Mach way.
 106          Hopefully either they will be on the stack as expected, or the
 107          stack will be zeros so we don't crash.  */
 108
 109       argcptr = (intptr_t *) argptr;
 110       argc = argcptr[0];
 111       argv = (char **) &argcptr[1];
 112       envp = &argv[argc + 1];
 113       envc = 0;
 114       while (envp[envc])
 115         ++envc;
 116     }
 117   else
 118     {
 119       /* Turn the block of null-separated strings we were passed for the
 120          arguments and environment into vectors of pointers to strings.  */
 121
 122       /* Count up the arguments so we can allocate ARGV.  */
 123       argc = __argz_count (args, argslen);
 124       /* Count up the environment variables so we can allocate ENVP.  */
 125       envc = __argz_count (env, envlen);
 126
 127       /* There were some arguments.  Allocate space for the vectors of
 128          pointers and fill them in.  We allocate the space for the
 129          environment pointers immediately after the argv pointers because
 130          the ELF ABI will expect it.  */
 131       argcptr = __alloca (sizeof (intptr_t) +
 132                           (argc + 1 + envc + 1) * sizeof (char *) +
 133                           sizeof (struct hurd_startup_data));
 134       *argcptr = argc;
 135       argv = (void *) (argcptr + 1);
 136       __argz_extract (args, argslen, argv);
 137
 138       /* There was some environment.  */
 139       envp = &argv[argc + 1];
 140       __argz_extract (env, envlen, envp);
 141     }
 142
 143   if (err || in_bootstrap == MACH_PORT_NULL)
 144     {
 145       /* Either we have no bootstrap port, or the RPC to the exec server
 146          failed.  Set all our other variables to have empty information.  */
 147
 148       data.flags = 0;
 149       args = env = NULL;
 150       argslen = envlen = 0;
 151       data.dtable = NULL;
 152       data.dtablesize = 0;
 153       data.portarray = NULL;
 154       data.portarraysize = 0;
 155       data.intarray = NULL;
 156       data.intarraysize = 0;
 157     }
 158   else if ((void *) &envp[envc + 1] == argv[0])
 159     {
 160       /* The arguments arrived on the stack from the kernel, but our
 161          protocol requires some space after them for a `struct
 162          hurd_startup_data'.  Move them.  */
 163       struct
 164         {
 165           intptr_t count;
 166           char *argv[argc + 1];
 167           char *envp[envc + 1];
 168           struct hurd_startup_data data;
 169         } *args = alloca (sizeof *args);
 170       if ((void *) &args[1] == (void *) argcptr)
 171         args = alloca (-((char *) &args->data - (char *) args));
 172       memmove (args, argcptr, (char *) &args->data - (char *) args);
 173       argcptr = (void *) args;
 174       argv = args->argv;
 175       envp = args->envp;
 176     }
 177
 178   {
 179     struct hurd_startup_data *d = (void *) &envp[envc + 1];
 180
 181     if ((void *) d != argv[0])
 182       {
 183         *d = data;
 184         _hurd_init_dtable = d->dtable;
 185         _hurd_init_dtablesize = d->dtablesize;
 186       }
 187
 188     (*main) (argcptr);
 189   }
 190
 191   /* Should never get here.  */
 192   LOSE;
 193   abort ();
 194 }