glibc/sysdeps/x86/dl-prop.h

/* Support for GNU properties.  x86 version.
   Copyright (C) 2018-2025 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/>.  */

#ifndef _DL_PROP_H
#define _DL_PROP_H

#include <libintl.h>

extern void _dl_cet_check (struct link_map *, const char *)
    attribute_hidden;
extern void _dl_cet_open_check (struct link_map *)
    attribute_hidden;

static void
dl_isa_level_check (struct link_map *m, const char *program)
{
  const struct cpu_features *cpu_features = __get_cpu_features ();
  unsigned int i;
  struct link_map *l;

  i = m->l_searchlist.r_nlist;
  while (i-- > 0)
    {
      /* Check each shared object to see if ISA level is compatible.  */
      l = m->l_initfini[i];

      /* Skip ISA level check if functions have been executed.  */
      if (l->l_init_called)
	continue;

#ifdef SHARED
      /* Skip ISA level check for ld.so since ld.so won't run if its ISA
	 level is higher than CPU.  */
      if (is_rtld_link_map (l) || is_rtld_link_map (l->l_real))
	continue;
#endif

      if ((l->l_x86_isa_1_needed & cpu_features->isa_1)
	  != l->l_x86_isa_1_needed)
	{
	  if (program)
	    _dl_fatal_printf ("%s: CPU ISA level is lower than required\n",
			      *l->l_name != '\0' ? l->l_name : program);
	  else
	    _dl_signal_error (0, l->l_name, "dlopen",
			      N_("CPU ISA level is lower than required"));
	}
    }
}

static inline void __attribute__ ((always_inline))
_rtld_main_check (struct link_map *m, const char *program)
{
  dl_isa_level_check (m, program);
#if CET_ENABLED
  _dl_cet_check (m, program);
#endif
}

static inline void __attribute__ ((always_inline))
_dl_open_check (struct link_map *m)
{
  dl_isa_level_check (m, NULL);
#if CET_ENABLED
  _dl_cet_open_check (m);
#endif
}

/* Check the GNU property and return its value.  It returns:
   -1: Skip this note.
    0: Stop checking.
    1: Continue to check.
 */
static inline int
_dl_check_gnu_property (unsigned int type, unsigned int datasz,
			void *ptr, unsigned int *feature_1_and,
			unsigned int *needed_1,
			unsigned int *isa_1_needed)
{
  if (type == GNU_PROPERTY_X86_FEATURE_1_AND
      || type == GNU_PROPERTY_X86_ISA_1_NEEDED
      || type == GNU_PROPERTY_1_NEEDED)
    {
      /* The sizes of types which we are searching for are
	 4 bytes.  There is no point to continue if this
	 note is ill-formed.  */
      if (datasz != 4)
	return -1;

      /* NB: Stop the scan only after seeing all types which
	 we are searching for.  */
      _Static_assert (((GNU_PROPERTY_X86_ISA_1_NEEDED
			> GNU_PROPERTY_X86_FEATURE_1_AND)
		       && (GNU_PROPERTY_X86_FEATURE_1_AND
			   > GNU_PROPERTY_1_NEEDED)),
		      "GNU_PROPERTY_X86_ISA_1_NEEDED > "
		      "GNU_PROPERTY_X86_FEATURE_1_AND && "
		      "GNU_PROPERTY_X86_FEATURE_1_AND > "
		      "GNU_PROPERTY_1_NEEDED");
      if (type == GNU_PROPERTY_X86_FEATURE_1_AND)
	*feature_1_and = *(unsigned int *) ptr;
      else if (type == GNU_PROPERTY_1_NEEDED)
	*needed_1 = *(unsigned int *) ptr;
      else
	{
	  *isa_1_needed = *(unsigned int *) ptr;

	  /* Keep searching for the next GNU property note
	     generated by the older linker.  */
	  return 0;
	}
    }
  else if (type > GNU_PROPERTY_X86_ISA_1_NEEDED)
    {
      /* Stop the scan since property type is in ascending
	 order.  */
      return 0;
    }

  return 1;
}

static inline void __attribute__ ((unused))
_dl_process_property_note (struct link_map *l, const ElfW(Nhdr) *note,
			   const ElfW(Addr) size, const ElfW(Addr) align)
{
  /* Skip if we have seen a NT_GNU_PROPERTY_TYPE_0 note before.  */
  if (l->l_property != lc_property_unknown)
    return;

  /* The NT_GNU_PROPERTY_TYPE_0 note must be aligned to 4 bytes in
     32-bit objects and to 8 bytes in 64-bit objects.  Skip notes
     with incorrect alignment.  */
  if (align != (__ELF_NATIVE_CLASS / 8))
    return;

  const ElfW(Addr) start = (ElfW(Addr)) note;

  unsigned int needed_1 = 0;
  unsigned int feature_1_and = 0;
  unsigned int isa_1_needed = 0;
  unsigned int last_type = 0;

  while ((ElfW(Addr)) (note + 1) - start < size)
    {
      /* Find the NT_GNU_PROPERTY_TYPE_0 note.  */
      if (note->n_namesz == 4
	  && note->n_type == NT_GNU_PROPERTY_TYPE_0
	  && memcmp (note + 1, "GNU", 4) == 0)
	{
	  /* Stop if we see more than one GNU property note which may
	     be generated by the older linker.  */
	  if (l->l_property != lc_property_unknown)
	    return;

	  /* Check CET status and ISA levels now.  */
	  l->l_property = lc_property_none;

	  /* Check for invalid property.  */
	  if (note->n_descsz < 8
	      || (note->n_descsz % sizeof (ElfW(Addr))) != 0)
	    return;

	  /* Start and end of property array.  */
	  unsigned char *ptr = (unsigned char *) (note + 1) + 4;
	  unsigned char *ptr_end = ptr + note->n_descsz;

	  do
	    {
	      unsigned int type = *(unsigned int *) ptr;
	      unsigned int datasz = *(unsigned int *) (ptr + 4);

	      /* Property type must be in ascending order.  */
	      if (type < last_type)
		return;

	      ptr += 8;
	      if ((ptr + datasz) > ptr_end)
		return;

	      last_type = type;

	      int result = _dl_check_gnu_property (type, datasz, ptr,
						   &feature_1_and,
						   &needed_1,
						   &isa_1_needed);
	      if (result == -1)
		return;		/* Skip this note.  */
	      else if (result == 0)
		break; /* Stop checking.  */

	      /* Check the next property item.  */
	      ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr)));
	    }
	  while ((ptr_end - ptr) >= 8);
	}

      /* NB: Note sections like .note.ABI-tag and .note.gnu.build-id are
	 aligned to 4 bytes in 64-bit ELF objects.  */
      note = ((const void *) note
	      + ELF_NOTE_NEXT_OFFSET (note->n_namesz, note->n_descsz,
				      align));
    }

  /* We get here only if there is one or no GNU property note.  */
  if (needed_1 != 0 || isa_1_needed != 0 || feature_1_and != 0)
    {
      l->l_property = lc_property_valid;
      l->l_1_needed = needed_1;
      l->l_x86_isa_1_needed = isa_1_needed;
      l->l_x86_feature_1_and = feature_1_and;
    }
  else
    l->l_property = lc_property_none;
}

static inline void __attribute__ ((unused))
_dl_process_pt_note (struct link_map *l, int fd, const ElfW(Phdr) *ph)
{
  const ElfW(Nhdr) *note = (const void *) (ph->p_vaddr + l->l_addr);
  _dl_process_property_note (l, note, ph->p_memsz, ph->p_align);
}

static inline int __attribute__ ((always_inline))
_dl_process_gnu_property (struct link_map *l, int fd, uint32_t type,
			  uint32_t datasz, void *data)
{
  /* This is called on each GNU property.  */
  unsigned int needed_1 = 0;
  unsigned int feature_1_and = 0;
  unsigned int isa_1_needed = 0;
  int result = _dl_check_gnu_property (type, datasz, data,
				       &feature_1_and, &needed_1,
				       &isa_1_needed);
  if (needed_1 != 0)
    l->l_1_needed = needed_1;
  if (isa_1_needed != 0)
    l->l_x86_isa_1_needed = isa_1_needed;
  if (feature_1_and != 0)
    l->l_x86_feature_1_and = feature_1_and;
  if ((needed_1 | isa_1_needed | feature_1_and) != 0)
    l->l_property = lc_property_valid;
  else if (l->l_property == lc_property_unknown)
    l->l_property = lc_property_none;
  return result <= 0 ? 0 : result;
}

#endif /* _DL_PROP_H */