hurd/hurdstartup.c

   1 /* Initial program startup for running under the GNU Hurd.
   2    Copyright (C) 1991-2019 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 <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 <unistd.h>
  27 #include <elf.h>
  28 #include <set-hooks.h>
  29 #include "hurdstartup.h"
  30 #include <argz.h>
  31
  32 mach_port_t *_hurd_init_dtable;
  33 mach_msg_type_number_t _hurd_init_dtablesize;
  34
  35 extern void __mach_init (void);
  36
  37 /* Entry point.  This is the first thing in the text segment.
  38
  39    The exec server started the initial thread in our task with this spot the
  40    PC, and a stack that is presumably big enough.  We do basic Mach
  41    initialization so mig-generated stubs work, and then do an exec_startup
  42    RPC on our bootstrap port, to which the exec server responds with the
  43    information passed in the exec call, as well as our original bootstrap
  44    port, and the base address and size of the preallocated stack.
  45
  46    If using cthreads, we are given a new stack by cthreads initialization and
  47    deallocate the stack set up by the exec server.  On the new stack we call
  48    `start1' (above) to do the rest of the startup work.  Since the stack may
  49    disappear out from under us in a machine-dependent way, we use a pile of
  50    static variables to communicate the information from exec_startup to start1.
  51    This is unfortunate but preferable to machine-dependent frobnication to copy
  52    the state from the old stack to the new one.  */
  53
  54
  55 void
  56 _hurd_startup (void **argptr, void (*main) (intptr_t *data))
  57 {
  58   error_t err;
  59   mach_port_t in_bootstrap;
  60   char *args, *env;
  61   mach_msg_type_number_t argslen, envlen;
  62   struct hurd_startup_data data;
  63   char **argv, **envp;
  64   int argc, envc;
  65   intptr_t *argcptr;
  66   vm_address_t addr;
  67
  68   /* Attempt to map page zero redzoned before we receive any RPC
  69      data that might get allocated there.  We can ignore errors.  */
  70   addr = 0;
  71   __vm_map (__mach_task_self (),
  72             &addr, __vm_page_size, 0, 0, MACH_PORT_NULL, 0, 1,
  73             VM_PROT_NONE, VM_PROT_NONE, VM_INHERIT_COPY);
  74
  75   if (err = __task_get_special_port (__mach_task_self (), TASK_BOOTSTRAP_PORT,
  76                                      &in_bootstrap))
  77     LOSE;
  78
  79   if (in_bootstrap != MACH_PORT_NULL)
  80     {
  81       /* Call the exec server on our bootstrap port and
  82          get all our standard information from it.  */
  83
  84       argslen = envlen = 0;
  85       data.dtablesize = data.portarraysize = data.intarraysize = 0;
  86
  87       err = __exec_startup_get_info (in_bootstrap,
  88                                      &data.user_entry,
  89                                      &data.phdr, &data.phdrsz,
  90                                      &data.stack_base, &data.stack_size,
  91                                      &data.flags,
  92                                      &args, &argslen,
  93                                      &env, &envlen,
  94                                      &data.dtable, &data.dtablesize,
  95                                      &data.portarray, &data.portarraysize,
  96                                      &data.intarray, &data.intarraysize);
  97       __mach_port_deallocate (__mach_task_self (), in_bootstrap);
  98     }
  99
 100   if (err || in_bootstrap == MACH_PORT_NULL || (data.flags & EXEC_STACK_ARGS))
 101     {
 102       /* Either we have no bootstrap port, or the RPC to the exec server
 103          failed, or whoever started us up passed the flag saying args are
 104          on the stack.  Try to snarf the args in the canonical Mach way.
 105          Hopefully either they will be on the stack as expected, or the
 106          stack will be zeros so we don't crash.  */
 107
 108       argcptr = (intptr_t *) argptr;
 109       argc = argcptr[0];
 110       argv = (char **) &argcptr[1];
 111       envp = &argv[argc + 1];
 112       envc = 0;
 113       while (envp[envc])
 114         ++envc;
 115     }
 116   else
 117     {
 118       /* Turn the block of null-separated strings we were passed for the
 119          arguments and environment into vectors of pointers to strings.  */
 120
 121       /* Count up the arguments so we can allocate ARGV.  */
 122       argc = __argz_count (args, argslen);
 123       /* Count up the environment variables so we can allocate ENVP.  */
 124       envc = __argz_count (env, envlen);
 125
 126       /* There were some arguments.  Allocate space for the vectors of
 127          pointers and fill them in.  We allocate the space for the
 128          environment pointers immediately after the argv pointers because
 129          the ELF ABI will expect it.  */
 130       argcptr = __alloca (sizeof (intptr_t)
 131                           + (argc + 1 + envc + 1) * sizeof (char *)
 132                           + sizeof (struct hurd_startup_data));
 133       *argcptr = argc;
 134       argv = (void *) (argcptr + 1);
 135       __argz_extract (args, argslen, argv);
 136
 137       /* There was some environment.  */
 138       envp = &argv[argc + 1];
 139       __argz_extract (env, envlen, envp);
 140     }
 141
 142   if (err || in_bootstrap == MACH_PORT_NULL)
 143     {
 144       /* Either we have no bootstrap port, or the RPC to the exec server
 145          failed.  Set all our other variables to have empty information.  */
 146
 147       data.flags = 0;
 148       args = env = NULL;
 149       argslen = envlen = 0;
 150       data.dtable = NULL;
 151       data.dtablesize = 0;
 152       data.portarray = NULL;
 153       data.portarraysize = 0;
 154       data.intarray = NULL;
 155       data.intarraysize = 0;
 156     }
 157   else if ((void *) &envp[envc + 1] == argv[0])
 158     {
 159       /* The arguments arrived on the stack from the kernel, but our
 160          protocol requires some space after them for a `struct
 161          hurd_startup_data'.  Move them.  */
 162       struct
 163         {
 164           intptr_t count;
 165           char *argv[argc + 1];
 166           char *envp[envc + 1];
 167           struct hurd_startup_data data;
 168         } *args = alloca (sizeof *args);
 169       if ((void *) &args[1] == (void *) argcptr)
 170         args = alloca (-((char *) &args->data - (char *) args));
 171       memmove (args, argcptr, (char *) &args->data - (char *) args);
 172       argcptr = (void *) args;
 173       argv = args->argv;
 174       envp = args->envp;
 175     }
 176
 177   {
 178     struct hurd_startup_data *d = (void *) &envp[envc + 1];
 179
 180     if ((void *) d != argv[0])
 181       {
 182         *d = data;
 183         _hurd_init_dtable = d->dtable;
 184         _hurd_init_dtablesize = d->dtablesize;
 185       }
 186
 187     (*main) (argcptr);
 188   }
 189
 190   /* Should never get here.  */
 191   LOSE;
 192   abort ();
 193 }