glibc/sysdeps/mach/hurd/i386/init-first.c

/* Initialization code run first thing by the ELF startup code.  For i386/Hurd.
   Copyright (C) 1995-2023 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <hurd.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sysdep.h>
#include <set-hooks.h>
#include "hurdstartup.h"
#include "hurdmalloc.h"		/* XXX */
#include "../locale/localeinfo.h"

#include <ldsodefs.h>
#include <fpu_control.h>
#include <libc-diag.h>
#include <libc-internal.h>

extern void __mach_init (void);
extern void __init_misc (int, char **, char **);

unsigned long int __hurd_threadvar_stack_offset;
unsigned long int __hurd_threadvar_stack_mask;

extern int __libc_argc attribute_hidden;
extern char **__libc_argv attribute_hidden;
extern char **_dl_argv;

#ifndef SHARED
unsigned short __init1_desc;
static tcbhead_t __init1_tcbhead;
#endif

/* Things that want to be run before _hurd_init or much anything else.
   Importantly, these are called before anything tries to use malloc.  */
DEFINE_HOOK (_hurd_preinit_hook, (void));


/* We call this once the Hurd magic is all set up and we are ready to be a
   Posixoid program.  This does the same things the generic version does.  */
static void
posixland_init (int argc, char **argv, char **envp)
{
  /* Now we have relocations etc. we can start signals etc.  */
  _hurd_libc_proc_init (argv);

#ifdef SHARED
  /* Make sure we don't initialize twice.  */
  if (__libc_initial)
    {
      /* Set the FPU control word to the proper default value.  */
      __setfpucw (__fpu_control);
    }
  else
    {
      /* Initialize data structures so the additional libc can do RPCs.  */
      __mach_init ();
    }
#else /* !SHARED */
  __setfpucw (__fpu_control);
#endif

  /* Save the command-line arguments.  */
  __libc_argc = argc;
  __libc_argv = argv;
  __environ = envp;

#ifndef SHARED
  _dl_non_dynamic_init ();
#endif
  __init_misc (argc, argv, envp);
}


static void
init1 (int argc, char *arg0, ...)
{
  char **argv = &arg0;
  char **envp = &argv[argc + 1];
  struct hurd_startup_data *d;

  while (*envp)
    ++envp;
  d = (void *) ++envp;

  if ((void *) d == argv[0])
    {
      /* No Hurd data block to process.  */
#ifndef SHARED
      __libc_enable_secure = 0;
#endif
      return;
    }

#ifndef SHARED
  __libc_enable_secure = d->flags & EXEC_SECURE;
#endif

  _hurd_init_dtable = d->dtable;
  _hurd_init_dtablesize = d->dtablesize;

  {
    /* Check if the stack we are now on is different from
       the one described by _hurd_stack_{base,size}.  */

    char dummy;
    const vm_address_t newsp = (vm_address_t) &dummy;

    if (d->stack_size != 0 && (newsp < d->stack_base
			       || newsp - d->stack_base > d->stack_size))
      /* The new stack pointer does not intersect with the
	 stack the exec server set up for us, so free that stack.  */
      __vm_deallocate (__mach_task_self (), d->stack_base, d->stack_size);
  }

  if (d->portarray || d->intarray)
    /* Initialize library data structures, start signal processing, etc.  */
    _hurd_init (d->flags, argv,
		d->portarray, d->portarraysize,
		d->intarray, d->intarraysize);
}


static inline void
init (int *data)
{
  /* data is the address of the argc parameter to _dl_init_first or
     doinit1 in _hurd_stack_setup, so the array subscripts are
     undefined.  */
  DIAG_PUSH_NEEDS_COMMENT;
  DIAG_IGNORE_NEEDS_COMMENT (10, "-Warray-bounds");

  int argc = *data;
  char **argv = (void *) (data + 1);
  char **envp = &argv[argc + 1];

  /* Since the cthreads initialization code uses malloc, and the
     malloc initialization code needs to get at the environment, make
     sure we can find it.  We'll need to do this again later on since
     switching stacks changes the location where the environment is
     stored.  */
  __environ = envp;

#ifndef SHARED
  struct hurd_startup_data *d;

  while (*envp)
    ++envp;
  d = (void *) ++envp;

  /* If we are the bootstrap task started by the kernel,
     then after the environment pointers there is no Hurd
     data block; the argument strings start there.  */
  if ((void *) d == argv[0] || d->phdr == 0)
    {
      /* With a new enough linker (binutils-2.23 or better),
         the magic __ehdr_start symbol will be available and
         __libc_start_main will have done this that way already.  */
      if (_dl_phdr == NULL)
        {
          /* We may need to see our own phdrs, e.g. for TLS setup.
             Try the usual kludge to find the headers without help from
             the exec server.  */
          extern const void __executable_start;
          const ElfW(Ehdr) *const ehdr = &__executable_start;
          _dl_phdr = (const void *) ehdr + ehdr->e_phoff;
          _dl_phnum = ehdr->e_phnum;
          assert (ehdr->e_phentsize == sizeof (ElfW(Phdr)));
        }
    }
  else
    {
      _dl_phdr = (ElfW(Phdr) *) d->phdr;
      _dl_phnum = d->phdrsz / sizeof (ElfW(Phdr));
      assert (d->phdrsz % sizeof (ElfW(Phdr)) == 0);
    }
#endif

  /* Call `init1' (above) with the user code as the return address, and the
     argument data immediately above that on the stack.  */

  int usercode;

  void call_init1 (void);

  /* The argument data is just above the stack frame we will unwind by
     returning.  Mutate our own return address to run the code below.  */
  /* The following expression would typically be written as
     ``__builtin_return_address (0)''.  But, for example, GCC 4.4.6 doesn't
     recognize that this read operation may alias the following write
     operation, and thus is free to reorder the two, clobbering the
     original return address.  */
  usercode = *((int *) __builtin_frame_address (0) + 1);
  /* GCC 4.4.6 also wants us to force loading USERCODE already here.  */
  asm volatile ("# %0" : : "X" (usercode));
  *((void **) __builtin_frame_address (0) + 1) = &call_init1;
  /* Force USERCODE into %eax and &init1 into %ecx, which are not
     restored by function return.  */
  asm volatile ("# a %0 c %1" : : "a" (usercode), "c" (&init1));

  DIAG_POP_NEEDS_COMMENT;	/* -Warray-bounds.  */
}

/* These bits of inline assembler used to be located inside `init'.
   However they were optimized away by gcc 2.95.  */

/* The return address of `init' above, was redirected to here, so at
   this point our stack is unwound and callers' registers restored.
   Only %ecx and %eax are call-clobbered and thus still have the
   values we set just above.  Fetch from there the new stack pointer
   we will run on, and jmp to the run-time address of `init1'; when it
   returns, it will run the user code with the argument data at the
   top of the stack.  */
asm ("switch_stacks:\n"
     "	movl %eax, %esp\n"
     "	jmp *%ecx");

/* As in the stack-switching case, at this point our stack is unwound
   and callers' registers restored, and only %ecx and %eax communicate
   values from the lines above.  In this case we have stashed in %eax
   the user code return address.  Push it on the top of the stack so
   it acts as init1's return address, and then jump there.  */
asm ("call_init1:\n"
     "	push %eax\n"
     "	jmp *%ecx\n");


/* Do the first essential initializations that must precede all else.  */
static inline void
first_init (void)
{
  /* Initialize data structures so we can do RPCs.  */
  __mach_init ();

#ifndef SHARED
  /* In the static case, we need to set up TLS early so that the stack
     protection guard can be read at gs:0x14 by the gcc-generated snippets.  */
  _hurd_tls_init(&__init1_tcbhead);
  asm ("movw %%gs,%w0" : "=m" (__init1_desc));
#endif

  RUN_RELHOOK (_hurd_preinit_hook, ());
}

#ifdef SHARED
/* This function is called specially by the dynamic linker to do early
   initialization of the shared C library before normal initializers
   expecting a Posixoid environment can run.  It gets called with the
   stack set up just as the user will see it, so it can switch stacks.  */

void
_dl_init_first (int argc, ...)
{
  first_init ();

  /* If we use ``__builtin_frame_address (0) + 2'' here, GCC gets confused.  */
  init (&argc);
}
#endif


#ifdef SHARED
/* The regular posixland initialization is what goes into libc's
   normal initializer.  */
/* NOTE!  The linker notices the magical name `_init' and sets the DT_INIT
   pointer in the dynamic section based solely on that.  It is convention
   for this function to be in the `.init' section, but the symbol name is
   the only thing that really matters!!  */
strong_alias (posixland_init, _init);

void
__libc_init_first (int argc, char **argv, char **envp)
{
  /* Everything was done in the shared library initializer, _init.  */
}
#else
strong_alias (posixland_init, __libc_init_first);


/* XXX This is all a crock and I am not happy with it.
   This poorly-named function is called by static-start.S,
   which should not exist at all.  */
void
inhibit_stack_protector
_hurd_stack_setup (void)
{
  intptr_t caller = (intptr_t) __builtin_return_address (0);

  void doinit (intptr_t *data)
    {
      /* This function gets called with the argument data at TOS.  */
      void doinit1 (int argc, ...)
	{
	  /* If we use ``__builtin_frame_address (0) + 2'' here, GCC gets
	     confused.  */
	  init ((int *) &argc);
	}

      /* Push the user return address after the argument data, and then
	 jump to `doinit1' (above), so it is as if __libc_init_first's
	 caller had called `doinit1' with the argument data already on the
	 stack.  */
      *--data = caller;
      asm volatile ("movl %0, %%esp\n" /* Switch to new outermost stack.  */
		    "movl $0, %%ebp\n" /* Clear outermost frame pointer.  */
		    "jmp *%1" : : "r" (data), "r" (&doinit1));
      /* NOTREACHED */
    }

  first_init ();

  _hurd_startup ((void **) __builtin_frame_address (0) + 2, &doinit);
}
#endif


/* This function is defined here so that if this file ever gets into
   ld.so we will get a link error.  Having this file silently included
   in ld.so causes disaster, because the _init definition above will
   cause ld.so to gain an init function, which is not a cool thing. */

void
_dl_start (void)
{
  abort ();
}