path: root/csu/libc-start.c

/* Perform initialization and invoke main.
   Copyright (C) 1998-2025 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/>.  */

/* Note: This code is only part of the startup code proper for
   statically linked binaries.  For dynamically linked binaries, it
   resides in libc.so.  */

/* Mark symbols hidden in static PIE for early self relocation to work.  */
#if BUILD_PIE_DEFAULT
# pragma GCC visibility push(hidden)
#endif

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <ldsodefs.h>
#include <libc-diag.h>
#include <libc-internal.h>
#include <elf/libc-early-init.h>
#include <stdbool.h>
#include <elf-initfini.h>
#include <shlib-compat.h>

#include <elf/dl-tunables.h>

extern void __libc_init_first (int argc, char **argv, char **envp);

#include <tls.h>
#ifndef SHARED
# include <dl-osinfo.h>
# ifndef THREAD_SET_STACK_GUARD
/* Only exported for architectures that don't store the stack guard canary
   in thread local area.  */
uintptr_t __stack_chk_guard attribute_relro;
# endif
# ifndef  THREAD_SET_POINTER_GUARD
/* Only exported for architectures that don't store the pointer guard
   value in thread local area.  */
uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
# endif
#endif

#ifndef SHARED
# include <link.h>
# include <dl-irel.h>

# ifdef ELF_MACHINE_IRELA
#  define IREL_T	ElfW(Rela)
#  define IPLT_START	__rela_iplt_start
#  define IPLT_END	__rela_iplt_end
#  define IREL		elf_irela
# elif defined ELF_MACHINE_IREL
#  define IREL_T	ElfW(Rel)
#  define IPLT_START	__rel_iplt_start
#  define IPLT_END	__rel_iplt_end
#  define IREL		elf_irel
# endif

static void
apply_irel (void)
{
# ifdef IREL
  /* We use weak references for these so that we'll still work with a linker
     that doesn't define them.  Such a linker doesn't support IFUNC at all
     and so uses won't work, but a statically-linked program that doesn't
     use any IFUNC symbols won't have a problem.  */
  extern const IREL_T IPLT_START[] __attribute__ ((weak));
  extern const IREL_T IPLT_END[] __attribute__ ((weak));
  for (const IREL_T *ipltent = IPLT_START; ipltent < IPLT_END; ++ipltent)
    IREL (ipltent);
# endif
}
#endif


#ifdef LIBC_START_MAIN
# ifdef LIBC_START_DISABLE_INLINE
#  define STATIC static
# else
#  define STATIC static inline __attribute__ ((always_inline))
# endif
# define DO_DEFINE_LIBC_START_MAIN_VERSION 0
#else
# define STATIC
# define LIBC_START_MAIN __libc_start_main_impl
# define DO_DEFINE_LIBC_START_MAIN_VERSION 1
#endif

#ifdef MAIN_AUXVEC_ARG
/* main gets passed a pointer to the auxiliary.  */
# define MAIN_AUXVEC_DECL	, void *
# define MAIN_AUXVEC_PARAM	, auxvec
#else
# define MAIN_AUXVEC_DECL
# define MAIN_AUXVEC_PARAM
#endif

#ifndef ARCH_INIT_CPU_FEATURES
# define ARCH_INIT_CPU_FEATURES()
#endif

/* Obtain the definition of __libc_start_call_main.  */
#include <libc_start_call_main.h>

#ifdef SHARED
/* Initialization for dynamic executables.  Find the main executable
   link map and run its init functions.  */
static void
call_init (int argc, char **argv, char **env)
{
  /* Obtain the main map of the executable.  */
  struct link_map *l = GL(dl_ns)[LM_ID_BASE]._ns_loaded;

  /* DT_PREINIT_ARRAY is not processed here.  It is already handled in
     _dl_init in elf/dl-init.c.  Also see the call_init function in
     the same file.  */

  if (ELF_INITFINI && l->l_info[DT_INIT] != NULL)
    DL_CALL_DT_INIT(l, l->l_addr + l->l_info[DT_INIT]->d_un.d_ptr,
		    argc, argv, env);

  ElfW(Dyn) *init_array = l->l_info[DT_INIT_ARRAY];
  if (init_array != NULL)
    {
      unsigned int jm
	= l->l_info[DT_INIT_ARRAYSZ]->d_un.d_val / sizeof (ElfW(Addr));
      ElfW(Addr) *addrs = (void *) (init_array->d_un.d_ptr + l->l_addr);
      for (unsigned int j = 0; j < jm; ++j)
	((dl_init_t) addrs[j]) (argc, argv, env);
    }
}

#else /* !SHARED */

/* These magic symbols are provided by the linker.  */
extern void (*__preinit_array_start []) (int, char **, char **)
  attribute_hidden;
extern void (*__preinit_array_end []) (int, char **, char **)
  attribute_hidden;
extern void (*__init_array_start []) (int, char **, char **)
  attribute_hidden;
extern void (*__init_array_end []) (int, char **, char **)
  attribute_hidden;
extern void (*__fini_array_start []) (void) attribute_hidden;
extern void (*__fini_array_end []) (void) attribute_hidden;

# if ELF_INITFINI
/* These function symbols are provided for the .init/.fini section entry
   points automagically by the linker.  */
extern void _init (void);
extern void _fini (void);
# endif

/* Initialization for static executables.  There is no dynamic
   segment, so we access the symbols directly.  */
static void
call_init (int argc, char **argv, char **envp)
{
  /* For static executables, preinit happens right before init.  */
  {
    const size_t size = __preinit_array_end - __preinit_array_start;
    size_t i;
    for (i = 0; i < size; i++)
      (*__preinit_array_start [i]) (argc, argv, envp);
  }

# if ELF_INITFINI
  _init ();
# endif

  const size_t size = __init_array_end - __init_array_start;
  for (size_t i = 0; i < size; i++)
      (*__init_array_start [i]) (argc, argv, envp);
}

/* Likewise for the destructor.  */
static