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/* Support for GNU properties. x86 version.
Copyright (C) 2018-2020 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 <not-cancel.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 inline void __attribute__ ((always_inline))
_rtld_main_check (struct link_map *m, const char *program)
{
#if CET_ENABLED
_dl_cet_check (m, program);
#endif
}
static inline void __attribute__ ((always_inline))
_dl_open_check (struct link_map *m)
{
#if CET_ENABLED
_dl_cet_open_check (m);
#endif
}
static inline void __attribute__ ((unused))
_dl_process_cet_property_note (struct link_map *l,
const ElfW(Nhdr) *note,
const ElfW(Addr) size,
const ElfW(Addr) align)
{
#if CET_ENABLED
/* Skip if we have seen a NT_GNU_PROPERTY_TYPE_0 note before. */
if (l->l_cet != lc_unknown)
return;
/* The NT_GNU_PROPERTY_TYPE_0 note must be aliged 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 feature_1 = 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_cet != lc_unknown)
return;
/* Check CET status now. */
l->l_cet = lc_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;
if (type == GNU_PROPERTY_X86_FEATURE_1_AND)
{
/* The size of GNU_PROPERTY_X86_FEATURE_1_AND is 4
bytes. When seeing GNU_PROPERTY_X86_FEATURE_1_AND,
we stop the search regardless if its size is correct
or not. There is no point to continue if this note
is ill-formed. */
if (datasz != 4)
return;
feature_1 = *(unsigned int *) ptr;
/* Keep searching for the next GNU property note
generated by the older linker. */
break;
}
else if (type > GNU_PROPERTY_X86_FEATURE_1_AND)
{
/* Stop since property type is in ascending order. */
return;
}
/* 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 ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT))
l->l_cet |= lc_ibt;
if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_SHSTK))
l->l_cet |= lc_shstk;
#endif
}
#ifdef FILEBUF_SIZE
static inline int __attribute__ ((unused))
_dl_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph,
int fd, struct filebuf *fbp)
{
# if CET_ENABLED
const ElfW(Nhdr) *note;
ElfW(Nhdr) *note_malloced = NULL;
ElfW(Addr) size = ph->p_filesz;
if (ph->p_offset + size <= (size_t) fbp->len)
note = (const void *) (fbp->buf + ph->p_offset);
else
{
if (size < __MAX_ALLOCA_CUTOFF)
note = alloca (size);
else
{
note_malloced = malloc (size);
note = note_malloced;
}
if (__pread64_nocancel (fd, (void *) note, size, ph->p_offset) != size)
{
if (note_malloced)
free (note_malloced);
return -1;
}
}
_dl_process_cet_property_note (l, note, size, ph->p_align);
if (note_malloced)
free (note_malloced);
# endif
return 0;
}
#endif
static inline int __attribute__ ((unused))
_rtld_process_pt_note (struct link_map *l, const ElfW(Phdr) *ph)
{
const ElfW(Nhdr) *note = (const void *) (ph->p_vaddr + l->l_addr);
_dl_process_cet_property_note (l, note, ph->p_memsz, ph->p_align);
return 0;
}
#endif /* _DL_PROP_H */
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