hurd/hurdstartup.c

   1 /* Initial program startup for running under the GNU Hurd.
   2    Copyright (C) 1991-2023 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 <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
  47 void
  48 _hurd_startup (void **argptr, void (*main) (intptr_t *data))
  49 {
  50   error_t err;
  51   mach_port_t in_bootstrap;
  52   char *args, *env;
  53   mach_msg_type_number_t argslen, envlen;
  54   struct hurd_startup_data data;
  55   char **argv, **envp;
  56   int argc, envc;
  57   intptr_t *argcptr;
  58   vm_address_t addr;
  59
  60   /* Attempt to map page zero redzoned before we receive any RPC
  61      data that might get allocated there.  We can ignore errors.  */
  62   addr = 0;
  63   __vm_map (__mach_task_self (),
  64             &addr, __vm_page_size, 0, 0, MACH_PORT_NULL, 0, 1,
  65             VM_PROT_NONE, VM_PROT_NONE, VM_INHERIT_COPY);
  66
  67   if (err = __task_get_special_port (__mach_task_self (), TASK_BOOTSTRAP_PORT,
  68                                      &in_bootstrap))
  69     LOSE;
  70
  71   if (in_bootstrap != MACH_PORT_NULL)
  72     {
  73       /* Call the exec server on our bootstrap port and
  74          get all our standard information from it.  */
  75
  76       argslen = envlen = 0;
  77       data.dtablesize = data.portarraysize = data.intarraysize = 0;
  78
  79       err = __exec_startup_get_info (in_bootstrap,
  80                                      &data.user_entry,
  81                                      &data.phdr, &data.phdrsz,
  82                                      &data.stack_base, &data.stack_size,
  83                                      &data.flags,
  84                                      &args, &argslen,
  85                                      &env, &envlen,
  86                                      &data.dtable, &data.dtablesize,
  87                                      &data.portarray, &data.portarraysize,
  88                                      &data.intarray, &data.intarraysize);
  89       __mach_port_deallocate (__mach_task_self (), in_bootstrap);
  90     }
  91
  92   if (err || in_bootstrap == MACH_PORT_NULL || (data.flags & EXEC_STACK_ARGS))
  93     {
  94       /* Either we have no bootstrap port, or the RPC to the exec server
  95          failed, or whoever started us up passed the flag saying args are
  96          on the stack.  Try to snarf the args in the canonical Mach way.
  97          Hopefully either they will be on the stack as expected, or the
  98          stack will be zeros so we don't crash.  */
  99
 100       argcptr = (intptr_t *) argptr;
 101       argc = argcptr[0];
 102       argv = (char **) &argcptr[1];
 103       envp = &argv[argc + 1];
 104       envc = 0;
 105       while (envp[envc])
 106         ++envc;
 107     }
 108   else
 109     {
 110       /* Turn the block of null-separated strings we were passed for the
 111          arguments and environment into vectors of pointers to strings.  */
 112
 113       /* Count up the arguments so we can allocate ARGV.  */
 114       argc = __argz_count (args, argslen);
 115       /* Count up the environment variables so we can allocate ENVP.  */
 116       envc = __argz_count (env, envlen);
 117
 118       /* There were some arguments.  Allocate space for the vectors of
 119          pointers and fill them in.  We allocate the space for the
 120          environment pointers immediately after the argv pointers because
 121          the ELF ABI will expect it.  */
 122       argcptr = __alloca (sizeof (intptr_t)
 123                           + (argc + 1 + envc + 1) * sizeof (char *)
 124                           + sizeof (struct hurd_startup_data));
 125       *argcptr = argc;
 126       argv = (void *) (argcptr + 1);
 127       __argz_extract (args, argslen, argv);
 128
 129       /* There was some environment.  */
 130       envp = &argv[argc + 1];
 131       __argz_extract (env, envlen, envp);
 132     }
 133
 134   if (err || in_bootstrap == MACH_PORT_NULL)
 135     {
 136       /* Either we have no bootstrap port, or the RPC to the exec server
 137          failed.  Set all our other variables to have empty information.  */
 138
 139       data.flags = 0;
 140       args = env = NULL;
 141       argslen = envlen = 0;
 142       data.dtable = NULL;
 143       data.dtablesize = 0;
 144       data.portarray = NULL;
 145       data.portarraysize = 0;
 146       data.intarray = NULL;
 147       data.intarraysize = 0;
 148       data.stack_base = 0;
 149       data.stack_size = 0;
 150       data.phdr = 0;
 151       data.phdrsz = 0;
 152       data.user_entry = 0;
 153     }
 154   else if ((void *) &envp[envc + 1] == argv[0])
 155     {
 156       /* The arguments arrived on the stack from the kernel, but our
 157          protocol requires some space after them for a `struct
 158          hurd_startup_data'.  Move them.  */
 159       struct
 160         {
 161           intptr_t count;
 162           char *argv[argc + 1];
 163           char *envp[envc + 1];
 164           struct hurd_startup_data data;
 165         } *args = alloca (sizeof *args);
 166       if ((void *) &args[1] == (void *) argcptr)
 167         args = alloca (-((char *) &args->data - (char *) args));
 168       memmove (args, argcptr, (char *) &args->data - (char *) args);
 169       argcptr = (void *) args;
 170       argv = args->argv;
 171       envp = args->envp;
 172     }
 173
 174   {
 175     struct hurd_startup_data *d = (void *) &envp[envc + 1];
 176
 177     if ((void *) d != argv[0])
 178       {
 179         *d = data;
 180         _hurd_init_dtable = d->dtable;
 181         _hurd_init_dtablesize = d->dtablesize;
 182       }
 183
 184     (*main) (argcptr);
 185   }
 186
 187   /* Should never get here.  */
 188   LOSE;
 189   abort ();
 190 }