Merge changes Ie770320e,I32c05cce,Ia7cb2f40 into main
* changes:
bionic: linker_phdr: Introduce kPageSize
bionic: Introduce ElfReader::ReadPadSegmentNote()
bionic: Refactor __get_elf_note()
diff --git a/libc/Android.bp b/libc/Android.bp
index 244cbfb..807073a 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -222,6 +222,11 @@
name: "libc_bootstrap",
}
+filegroup {
+ name: "elf_note_sources",
+ srcs: ["bionic/elf_note.cpp"],
+}
+
// libc_init_static.cpp and libc_init_dynamic.cpp need to be built without stack protector.
// libc_init_static.cpp sets up TLS for static executables, and libc_init_dynamic.cpp initializes
// the stack protector global variable.
@@ -229,7 +234,10 @@
cc_library_static {
name: "libc_init_static",
defaults: ["libc_defaults"],
- srcs: ["bionic/libc_init_static.cpp"],
+ srcs: [
+ "bionic/libc_init_static.cpp",
+ ":elf_note_sources",
+ ],
cflags: [
"-fno-stack-protector",
diff --git a/libc/bionic/elf_note.cpp b/libc/bionic/elf_note.cpp
new file mode 100644
index 0000000..d5cd5de
--- /dev/null
+++ b/libc/bionic/elf_note.cpp
@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2024 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 "platform/bionic/macros.h"
+#include "private/elf_note.h"
+
+#include <string.h>
+
+bool __get_elf_note(unsigned note_type, const char* note_name, const ElfW(Addr) note_addr,
+ const ElfW(Phdr)* phdr_note, const ElfW(Nhdr)** note_hdr,
+ const char** note_desc) {
+ if (phdr_note->p_type != PT_NOTE || !note_name || !note_addr) {
+ return false;
+ }
+
+ ElfW(Addr) p = note_addr;
+ ElfW(Addr) note_end = p + phdr_note->p_memsz;
+
+ while (p + sizeof(ElfW(Nhdr)) <= note_end) {
+ const ElfW(Nhdr)* note = reinterpret_cast<const ElfW(Nhdr)*>(p);
+ p += sizeof(ElfW(Nhdr));
+ const char* name = reinterpret_cast<const char*>(p);
+ p += align_up(note->n_namesz, 4);
+ const char* desc = reinterpret_cast<const char*>(p);
+ p += align_up(note->n_descsz, 4);
+ if (p > note_end) {
+ break;
+ }
+ if (note->n_type != note_type) {
+ continue;
+ }
+ size_t note_name_len = strlen(note_name) + 1;
+ if (note->n_namesz != note_name_len || strncmp(note_name, name, note_name_len) != 0) {
+ break;
+ }
+
+ *note_hdr = note;
+ *note_desc = desc;
+
+ return true;
+ }
+ return false;
+}
+
+bool __find_elf_note(unsigned int note_type, const char* note_name, const ElfW(Phdr)* phdr_start,
+ size_t phdr_ct, const ElfW(Nhdr)** note_hdr, const char** note_desc,
+ const ElfW(Addr) load_bias) {
+ for (size_t i = 0; i < phdr_ct; ++i) {
+ const ElfW(Phdr)* phdr = &phdr_start[i];
+
+ ElfW(Addr) note_addr = load_bias + phdr->p_vaddr;
+ if (__get_elf_note(note_type, note_name, note_addr, phdr, note_hdr, note_desc)) {
+ return true;
+ }
+ }
+
+ return false;
+}
diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index f46d702..00faa5b 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -51,6 +51,7 @@
#include "private/bionic_elf_tls.h"
#include "private/bionic_globals.h"
#include "private/bionic_tls.h"
+#include "private/elf_note.h"
#include "pthread_internal.h"
#include "sys/system_properties.h"
#include "sysprop_helpers.h"
@@ -157,49 +158,12 @@
}
#ifdef __aarch64__
-static bool __get_elf_note(const ElfW(Phdr) * phdr_start, size_t phdr_ct,
- const ElfW(Addr) load_bias, unsigned desired_type,
- const char* desired_name, const ElfW(Nhdr) * *note_out,
- const char** desc_out) {
- for (size_t i = 0; i < phdr_ct; ++i) {
- const ElfW(Phdr)* phdr = &phdr_start[i];
- if (phdr->p_type != PT_NOTE) {
- continue;
- }
- ElfW(Addr) p = load_bias + phdr->p_vaddr;
- ElfW(Addr) note_end = load_bias + phdr->p_vaddr + phdr->p_memsz;
- while (p + sizeof(ElfW(Nhdr)) <= note_end) {
- const ElfW(Nhdr)* note = reinterpret_cast<const ElfW(Nhdr)*>(p);
- p += sizeof(ElfW(Nhdr));
- const char* name = reinterpret_cast<const char*>(p);
- p += align_up(note->n_namesz, 4);
- const char* desc = reinterpret_cast<const char*>(p);
- p += align_up(note->n_descsz, 4);
- if (p > note_end) {
- break;
- }
- if (note->n_type != desired_type) {
- continue;
- }
- size_t desired_name_len = strlen(desired_name);
- if (note->n_namesz != desired_name_len + 1 ||
- strncmp(desired_name, name, desired_name_len) != 0) {
- break;
- }
- *note_out = note;
- *desc_out = desc;
- return true;
- }
- }
- return false;
-}
-
static HeapTaggingLevel __get_memtag_level_from_note(const ElfW(Phdr) * phdr_start, size_t phdr_ct,
const ElfW(Addr) load_bias, bool* stack) {
const ElfW(Nhdr) * note;
const char* desc;
- if (!__get_elf_note(phdr_start, phdr_ct, load_bias, NT_ANDROID_TYPE_MEMTAG, "Android", ¬e,
- &desc)) {
+ if (!__find_elf_note(NT_ANDROID_TYPE_MEMTAG, "Android", phdr_start, phdr_ct, ¬e, &desc,
+ load_bias)) {
return M_HEAP_TAGGING_LEVEL_TBI;
}
@@ -210,7 +174,7 @@
note->n_descsz);
}
- // `desc` is always aligned due to ELF requirements, enforced in __get_elf_note().
+ // `desc` is always aligned due to ELF requirements, enforced in __find_elf_note().
ElfW(Word) note_val = *reinterpret_cast<const ElfW(Word)*>(desc);
*stack = (note_val & NT_MEMTAG_STACK) != 0;
diff --git a/libc/private/elf_note.h b/libc/private/elf_note.h
new file mode 100644
index 0000000..6a9399b
--- /dev/null
+++ b/libc/private/elf_note.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2024 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.
+ */
+
+#pragma once
+
+#include <elf.h>
+#include <link.h>
+
+// Get desired ELF note (Nhdr/desc) from mmapped PT_NOTE
+bool __get_elf_note(unsigned note_type, const char* note_name, const ElfW(Addr) note_addr,
+ const ElfW(Phdr)* phdr_note, const ElfW(Nhdr)** note_hdr,
+ const char** note_desc);
+
+// Search all mapped PT_NOTE's for the desired ELF note (Nhdr/desc)
+bool __find_elf_note(unsigned int note_type, const char* note_name, const ElfW(Phdr)* phdr_start,
+ size_t phdr_ct, const ElfW(Nhdr)** note_hdr, const char** note_desc,
+ const ElfW(Addr) load_bias);
diff --git a/linker/linker.cpp b/linker/linker.cpp
index ffbf136..724f821 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -639,6 +639,7 @@
si_->phdr = elf_reader.loaded_phdr();
si_->set_gap_start(elf_reader.gap_start());
si_->set_gap_size(elf_reader.gap_size());
+ si_->set_should_pad_segments(elf_reader.should_pad_segments());
return true;
}
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 0ad0fd5..85cd949 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -42,7 +42,9 @@
#include "linker_debug.h"
#include "linker_utils.h"
+#include "private/bionic_asm_note.h"
#include "private/CFIShadow.h" // For kLibraryAlignment
+#include "private/elf_note.h"
static int GetTargetElfMachine() {
#if defined(__arm__)
@@ -140,8 +142,18 @@
MAYBE_MAP_FLAG((x), PF_R, PROT_READ) | \
MAYBE_MAP_FLAG((x), PF_W, PROT_WRITE))
-// Default PMD size for x86_64 and aarch64 (2MB).
-static constexpr size_t kPmdSize = (1UL << 21);
+static const size_t kPageSize = page_size();
+
+/*
+ * Generic PMD size calculation:
+ * - Each page table (PT) is of size 1 page.
+ * - Each page table entry (PTE) is of size 64 bits.
+ * - Each PTE locates one physical page frame (PFN) of size 1 page.
+ * - A PMD entry locates 1 page table (PT)
+ *
+ * PMD size = Num entries in a PT * page_size
+ */
+static const size_t kPmdSize = (kPageSize / sizeof(uint64_t)) * kPageSize;
ElfReader::ElfReader()
: did_read_(false), did_load_(false), fd_(-1), file_offset_(0), file_size_(0), phdr_num_(0),
@@ -163,7 +175,8 @@
VerifyElfHeader() &&
ReadProgramHeaders() &&
ReadSectionHeaders() &&
- ReadDynamicSection()) {
+ ReadDynamicSection() &&
+ ReadPadSegmentNote()) {
did_read_ = true;
}
@@ -694,6 +707,46 @@
return true;
}
+// Find the ELF note of type NT_ANDROID_TYPE_PAD_SEGMENT and check that the desc value is 1.
+bool ElfReader::ReadPadSegmentNote() {
+ // The ELF can have multiple PT_NOTE's, check them all
+ for (size_t i = 0; i < phdr_num_; ++i) {
+ const ElfW(Phdr)* phdr = &phdr_table_[i];
+
+ if (phdr->p_type != PT_NOTE) {
+ continue;
+ }
+
+ // note_fragment is scoped to within the loop so that there is
+ // at most 1 PT_NOTE mapped at anytime during this search.
+ MappedFileFragment note_fragment;
+ if (!note_fragment.Map(fd_, file_offset_, phdr->p_offset, phdr->p_memsz)) {
+ DL_ERR("\"%s\" note mmap failed: %s", name_.c_str(), strerror(errno));
+ return false;
+ }
+
+ const ElfW(Nhdr)* note_hdr = nullptr;
+ const char* note_desc = nullptr;
+ if (!__get_elf_note(NT_ANDROID_TYPE_PAD_SEGMENT, "Android",
+ reinterpret_cast<ElfW(Addr)>(note_fragment.data()),
+ phdr, ¬e_hdr, ¬e_desc)) {
+ continue;
+ }
+
+ if (note_hdr->n_descsz != sizeof(ElfW(Word))) {
+ DL_ERR("\"%s\" NT_ANDROID_TYPE_PAD_SEGMENT note has unexpected n_descsz: %u",
+ name_.c_str(), reinterpret_cast<unsigned int>(note_hdr->n_descsz));
+ return false;
+ }
+
+ // 1 == enabled, 0 == disabled
+ should_pad_segments_ = *reinterpret_cast<const ElfW(Word)*>(note_desc) == 1;
+ return true;
+ }
+
+ return true;
+}
+
bool ElfReader::LoadSegments() {
for (size_t i = 0; i < phdr_num_; ++i) {
const ElfW(Phdr)* phdr = &phdr_table_[i];
diff --git a/linker/linker_phdr.h b/linker/linker_phdr.h
index 98bf020..e5b87bb 100644
--- a/linker/linker_phdr.h
+++ b/linker/linker_phdr.h
@@ -58,6 +58,7 @@
const char* get_string(ElfW(Word) index) const;
bool is_mapped_by_caller() const { return mapped_by_caller_; }
ElfW(Addr) entry_point() const { return header_.e_entry + load_bias_; }
+ bool should_pad_segments() const { return should_pad_segments_; }
private:
bool ReadElfHeader();
@@ -65,6 +66,7 @@
bool ReadProgramHeaders();
bool ReadSectionHeaders();
bool ReadDynamicSection();
+ bool ReadPadSegmentNote();
bool ReserveAddressSpace(address_space_params* address_space);
bool LoadSegments();
bool FindPhdr();
@@ -113,6 +115,9 @@
// Is map owned by the caller
bool mapped_by_caller_;
+ // Pad gaps between segments when memory mapping?
+ bool should_pad_segments_ = false;
+
// Only used by AArch64 at the moment.
GnuPropertySection note_gnu_property_ __unused;
};
diff --git a/linker/linker_soinfo.h b/linker/linker_soinfo.h
index 622719d..a5d31d5 100644
--- a/linker/linker_soinfo.h
+++ b/linker/linker_soinfo.h
@@ -364,6 +364,11 @@
bool memtag_heap() const { return memtag_dynamic_entries()->memtag_heap; }
bool memtag_stack() const { return memtag_dynamic_entries()->memtag_stack; }
+ void set_should_pad_segments(bool should_pad_segments) {
+ should_pad_segments_ = should_pad_segments;
+ }
+ bool should_pad_segments() const { return should_pad_segments_; }
+
private:
bool is_image_linked() const;
void set_image_linked();
@@ -449,6 +454,9 @@
// version >= 7
memtag_dynamic_entries_t memtag_dynamic_entries_;
+
+ // Pad gaps between segments when memory mapping?
+ bool should_pad_segments_ = false;
};
// This function is used by dlvsym() to calculate hash of sym_ver