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/*
* Copyright (C) 2020 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "linker_note_gnu_property.h"
#include <elf.h>
#include <link.h>
#include "linker.h"
#include "linker_debug.h"
#include "linker_globals.h"
#include "linker_soinfo.h"
GnuPropertySection::GnuPropertySection(const soinfo* si)
: GnuPropertySection(si->phdr, si->phnum, si->load_bias, si->get_realpath()) {}
GnuPropertySection::GnuPropertySection(const ElfW(Phdr)* phdr, size_t phdr_count,
const ElfW(Addr) load_bias, const char* name) {
// Try to find PT_GNU_PROPERTY segment.
auto note_gnu_property = FindSegment(phdr, phdr_count, load_bias, name);
// Perform some validity checks.
if (note_gnu_property && SanityCheck(note_gnu_property, name)) {
// Parse section.
Parse(note_gnu_property, name);
}
}
const ElfW(NhdrGNUProperty)* GnuPropertySection::FindSegment(const ElfW(Phdr)* phdr,
size_t phdr_count,
const ElfW(Addr) load_bias,
const char* name) const {
// According to Linux gABI extension this segment should contain
// .note.gnu.property section only.
if (phdr != nullptr) {
for (size_t i = 0; i < phdr_count; ++i) {
if (phdr[i].p_type != PT_GNU_PROPERTY) {
continue;
}
TRACE("\"%s\" PT_GNU_PROPERTY: found at segment index %zu", name, i);
// Check segment size.
if (phdr[i].p_memsz < sizeof(ElfW(NhdrGNUProperty))) {
DL_ERR_AND_LOG(
"\"%s\" PT_GNU_PROPERTY segment is too small. Segment "
"size is %zu, minimum is %zu.",
name, static_cast<size_t>(phdr[i].p_memsz), sizeof(ElfW(NhdrGNUProperty)));
return nullptr;
}
// PT_GNU_PROPERTY contains .note.gnu.property which has SHF_ALLOC
// attribute, therefore it is loaded.
auto note_nhdr = reinterpret_cast<ElfW(NhdrGNUProperty)*>(load_bias + phdr[i].p_vaddr);
// Check that the n_descsz <= p_memsz
if ((phdr[i].p_memsz - sizeof(ElfW(NhdrGNUProperty))) < note_nhdr->nhdr.n_descsz) {
DL_ERR_AND_LOG(
"\"%s\" PT_GNU_PROPERTY segment p_memsz (%zu) is too small for note n_descsz (%zu).",
name, static_cast<size_t>(phdr[i].p_memsz),
static_cast<size_t>(note_nhdr->nhdr.n_descsz));
return nullptr;
}
return note_nhdr;
}
}
TRACE("\"%s\" PT_GNU_PROPERTY: not found", name);
return nullptr;
}
bool GnuPropertySection::SanityCheck(const ElfW(NhdrGNUProperty)* note_nhdr,
const char* name) const {
// Check .note section type
if (note_nhdr->nhdr.n_type != NT_GNU_PROPERTY_TYPE_0) {
DL_ERR_AND_LOG("\"%s\" .note.gnu.property: unexpected note type. Expected %u, got %u.", name,
NT_GNU_PROPERTY_TYPE_0, note_nhdr->nhdr.n_type);
return false;
}
if (note_nhdr->nhdr.n_namesz != 4) {
DL_ERR_AND_LOG("\"%s\" .note.gnu.property: unexpected name size. Expected 4, got %u.", name,
note_nhdr->nhdr.n_namesz);
return false;
}
if (strncmp(note_nhdr->n_name, "GNU", 4) != 0) {
DL_ERR_AND_LOG("\"%s\" .note.gnu.property: unexpected name. Expected 'GNU', got '%s'.", name,
note_nhdr->n_name);
return false;
}
return true;
}
bool GnuPropertySection::Parse(const ElfW(NhdrGNUProperty)* note_nhdr, const char* name) {
// The total length of the program property array is in _bytes_.
ElfW(Word) offset = 0;
while (offset < note_nhdr->nhdr.n_descsz) {
DEBUG("\"%s\" .note.gnu.property: processing at offset 0x%x", name, offset);
// At least the "header" part must fit.
// The ABI doesn't say that pr_datasz can't be 0.
if ((note_nhdr->nhdr.n_descsz - offset) < sizeof(ElfW(Prop))) {
DL_ERR_AND_LOG(
"\"%s\" .note.gnu.property: no more space left for a "
"Program Property Note header.",
name);
return false;
}
// Loop on program property array.
const ElfW(Prop)* property = reinterpret_cast<const ElfW(Prop)*>(¬e_nhdr->n_desc[offset]);
const ElfW(Word) property_size =
align_up(sizeof(ElfW(Prop)) + property->pr_datasz, sizeof(ElfW(Addr)));
if ((note_nhdr->nhdr.n_descsz - offset) < property_size) {
DL_ERR_AND_LOG(
"\"%s\" .note.gnu.property: property descriptor size is "
"invalid. Expected at least %u bytes, got %u.",
name, property_size, note_nhdr->nhdr.n_descsz - offset);
return false;
}
// Cache found properties.
switch (property->pr_type) {
#if defined(__aarch64__)
case GNU_PROPERTY_AARCH64_FEATURE_1_AND: {
if (property->pr_datasz != 4) {
DL_ERR_AND_LOG(
"\"%s\" .note.gnu.property: property descriptor size is "
"invalid. Expected %u bytes for GNU_PROPERTY_AARCH64_FEATURE_1_AND, got %u.",
name, 4, property->pr_datasz);
return false;
}
const ElfW(Word) flags = *reinterpret_cast<const ElfW(Word)*>(&property->pr_data[0]);
properties_.bti_compatible = (flags & GNU_PROPERTY_AARCH64_FEATURE_1_BTI) != 0;
if (properties_.bti_compatible) {
INFO("[ BTI compatible: \"%s\" ]", name);
}
break;
}
#endif
default:
DEBUG("\"%s\" .note.gnu.property: found property pr_type %u pr_datasz 0x%x", name,
property->pr_type, property->pr_datasz);
break;
}
// Move offset, this should be safe to add because of previous checks.
offset += property_size;
}
return true;
}
#if defined(__aarch64__)
bool GnuPropertySection::IsBTICompatible() const {
return (g_platform_properties.bti_supported && properties_.bti_compatible);
}
#endif
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