platform_bionic/libc/bionic/libc_init_static.cpp
Mitch Phillips 93400371f7 [NFCI] Change Android's NT_TYPE to NT_ANDROID_TYPE.
Normally, platform-specific note types in the toolchain are prefixed
with the platform name. Because we're exposing the NT_TYPE_MEMTAG and
synthesizing the note in the toolchain in an upcoming patch
(https://reviews.llvm.org/D118948), it's been requested that we change
the name to include the platform prefix.

While NT_TYPE_IDENT and NT_TYPE_KUSER aren't known about or synthesized
by the toolchain, update those references as well for consistency.

Bug: N/A
Test: Build Android
Change-Id: I7742e4917ae275d59d7984991664ea48028053a1
2022-02-07 13:49:20 -08:00

427 lines
16 KiB
C++

/*
* Copyright (C) 2008 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 <android/api-level.h>
#include <elf.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/auxv.h>
#include <sys/mman.h>
#include "libc_init_common.h"
#include "pthread_internal.h"
#include "platform/bionic/macros.h"
#include "platform/bionic/mte.h"
#include "platform/bionic/page.h"
#include "platform/bionic/reserved_signals.h"
#include "private/KernelArgumentBlock.h"
#include "private/bionic_asm.h"
#include "private/bionic_asm_note.h"
#include "private/bionic_call_ifunc_resolver.h"
#include "private/bionic_elf_tls.h"
#include "private/bionic_globals.h"
#include "private/bionic_tls.h"
#include "sys/system_properties.h"
#if __has_feature(hwaddress_sanitizer)
#include <sanitizer/hwasan_interface.h>
#endif
// Leave the variable uninitialized for the sake of the dynamic loader, which
// links in this file. The loader will initialize this variable before
// relocating itself.
#if defined(__i386__)
__LIBC_HIDDEN__ void* __libc_sysinfo;
#endif
extern "C" int __cxa_atexit(void (*)(void *), void *, void *);
extern "C" const char* __gnu_basename(const char* path);
static void call_array(init_func_t** list, int argc, char* argv[], char* envp[]) {
// First element is -1, list is null-terminated
while (*++list) {
(*list)(argc, argv, envp);
}
}
#if defined(__aarch64__) || defined(__x86_64__)
extern __LIBC_HIDDEN__ __attribute__((weak)) ElfW(Rela) __rela_iplt_start[], __rela_iplt_end[];
static void call_ifunc_resolvers() {
if (__rela_iplt_start == nullptr || __rela_iplt_end == nullptr) {
// These symbols are not emitted by gold. Gold has code to do so, but for
// whatever reason it is not being run. In these cases ifuncs cannot be
// resolved, so we do not support using ifuncs in static executables linked
// with gold.
//
// Since they are weak, they will be non-null when linked with bfd/lld and
// null when linked with gold.
return;
}
for (ElfW(Rela) *r = __rela_iplt_start; r != __rela_iplt_end; ++r) {
ElfW(Addr)* offset = reinterpret_cast<ElfW(Addr)*>(r->r_offset);
ElfW(Addr) resolver = r->r_addend;
*offset = __bionic_call_ifunc_resolver(resolver);
}
}
#else
extern __LIBC_HIDDEN__ __attribute__((weak)) ElfW(Rel) __rel_iplt_start[], __rel_iplt_end[];
static void call_ifunc_resolvers() {
if (__rel_iplt_start == nullptr || __rel_iplt_end == nullptr) {
// These symbols are not emitted by gold. Gold has code to do so, but for
// whatever reason it is not being run. In these cases ifuncs cannot be
// resolved, so we do not support using ifuncs in static executables linked
// with gold.
//
// Since they are weak, they will be non-null when linked with bfd/lld and
// null when linked with gold.
return;
}
for (ElfW(Rel) *r = __rel_iplt_start; r != __rel_iplt_end; ++r) {
ElfW(Addr)* offset = reinterpret_cast<ElfW(Addr)*>(r->r_offset);
ElfW(Addr) resolver = *offset;
*offset = __bionic_call_ifunc_resolver(resolver);
}
}
#endif
static void apply_gnu_relro() {
ElfW(Phdr)* phdr_start = reinterpret_cast<ElfW(Phdr)*>(getauxval(AT_PHDR));
unsigned long int phdr_ct = getauxval(AT_PHNUM);
for (ElfW(Phdr)* phdr = phdr_start; phdr < (phdr_start + phdr_ct); phdr++) {
if (phdr->p_type != PT_GNU_RELRO) {
continue;
}
ElfW(Addr) seg_page_start = PAGE_START(phdr->p_vaddr);
ElfW(Addr) seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz);
// Check return value here? What do we do if we fail?
mprotect(reinterpret_cast<void*>(seg_page_start), seg_page_end - seg_page_start, PROT_READ);
}
}
static void layout_static_tls(KernelArgumentBlock& args) {
StaticTlsLayout& layout = __libc_shared_globals()->static_tls_layout;
layout.reserve_bionic_tls();
const char* progname = args.argv[0];
ElfW(Phdr)* phdr_start = reinterpret_cast<ElfW(Phdr)*>(getauxval(AT_PHDR));
size_t phdr_ct = getauxval(AT_PHNUM);
static TlsModule mod;
TlsModules& modules = __libc_shared_globals()->tls_modules;
if (__bionic_get_tls_segment(phdr_start, phdr_ct, 0, &mod.segment)) {
if (!__bionic_check_tls_alignment(&mod.segment.alignment)) {
async_safe_fatal("error: TLS segment alignment in \"%s\" is not a power of 2: %zu\n",
progname, mod.segment.alignment);
}
mod.static_offset = layout.reserve_exe_segment_and_tcb(&mod.segment, progname);
mod.first_generation = kTlsGenerationFirst;
modules.module_count = 1;
modules.static_module_count = 1;
modules.module_table = &mod;
} else {
layout.reserve_exe_segment_and_tcb(nullptr, progname);
}
// Enable the fast path in __tls_get_addr.
__libc_tls_generation_copy = modules.generation;
layout.finish_layout();
}
// Get the presiding config string, in the following order of priority:
// 1. Environment variables.
// 2. System properties, in the order they're specified in sys_prop_names.
// If neither of these options are specified, this function returns false.
// Otherwise, it returns true, and the presiding options string is written to
// the `options` buffer of size `size`. If this function returns true, `options`
// is guaranteed to be null-terminated. `options_size` should be at least
// PROP_VALUE_MAX.
bool get_config_from_env_or_sysprops(const char* env_var_name, const char* const* sys_prop_names,
size_t sys_prop_names_size, char* options,
size_t options_size) {
const char* env = getenv(env_var_name);
if (env && *env != '\0') {
strncpy(options, env, options_size);
options[options_size - 1] = '\0'; // Ensure null-termination.
return true;
}
for (size_t i = 0; i < sys_prop_names_size; ++i) {
if (__system_property_get(sys_prop_names[i], options) && *options != '\0') return true;
}
return false;
}
#ifdef __aarch64__
static bool __read_memtag_note(const ElfW(Nhdr)* note, const char* name, const char* desc,
unsigned* result) {
if (note->n_namesz != 8 || strncmp(name, "Android", 8) != 0) {
return false;
}
if (note->n_type != NT_ANDROID_TYPE_MEMTAG) {
return false;
}
if (note->n_descsz != 4) {
async_safe_fatal("unrecognized android.memtag note: n_descsz = %d, expected 4", note->n_descsz);
}
*result = *reinterpret_cast<const ElfW(Word)*>(desc);
return true;
}
static unsigned __get_memtag_note(const ElfW(Phdr)* phdr_start, size_t phdr_ct,
const ElfW(Addr) load_bias) {
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;
}
unsigned ret;
if (__read_memtag_note(note, name, desc, &ret)) {
return ret;
}
}
}
return 0;
}
// Returns true if there's an environment setting (either sysprop or env var)
// that should overwrite the ELF note, and places the equivalent heap tagging
// level into *level.
static bool get_environment_memtag_setting(HeapTaggingLevel* level) {
static const char kMemtagPrognameSyspropPrefix[] = "arm64.memtag.process.";
const char* progname = __libc_shared_globals()->init_progname;
if (progname == nullptr) return false;
const char* basename = __gnu_basename(progname);
static constexpr size_t kOptionsSize = PROP_VALUE_MAX;
char options_str[kOptionsSize];
size_t sysprop_size = strlen(basename) + strlen(kMemtagPrognameSyspropPrefix) + 1;
char* sysprop_name = static_cast<char*>(alloca(sysprop_size));
async_safe_format_buffer(sysprop_name, sysprop_size, "%s%s", kMemtagPrognameSyspropPrefix,
basename);
if (!get_config_from_env_or_sysprops("MEMTAG_OPTIONS", &sysprop_name,
/* sys_prop_names_size */ 1, options_str, kOptionsSize)) {
return false;
}
if (strcmp("sync", options_str) == 0) {
*level = M_HEAP_TAGGING_LEVEL_SYNC;
} else if (strcmp("async", options_str) == 0) {
*level = M_HEAP_TAGGING_LEVEL_ASYNC;
} else if (strcmp("off", options_str) == 0) {
*level = M_HEAP_TAGGING_LEVEL_TBI;
} else {
async_safe_format_log(
ANDROID_LOG_ERROR, "libc",
"unrecognized memtag level: \"%s\" (options are \"sync\", \"async\", or \"off\").",
options_str);
return false;
}
return true;
}
// Returns the initial heap tagging level. Note: This function will never return
// M_HEAP_TAGGING_LEVEL_NONE, if MTE isn't enabled for this process we enable
// M_HEAP_TAGGING_LEVEL_TBI.
static HeapTaggingLevel __get_heap_tagging_level(const void* phdr_start, size_t phdr_ct,
uintptr_t load_bias) {
HeapTaggingLevel level;
if (get_environment_memtag_setting(&level)) return level;
unsigned note_val =
__get_memtag_note(reinterpret_cast<const ElfW(Phdr)*>(phdr_start), phdr_ct, load_bias);
if (note_val & ~(NT_MEMTAG_LEVEL_MASK | NT_MEMTAG_HEAP)) {
async_safe_fatal("unrecognized android.memtag note: desc = %d", note_val);
}
if (!(note_val & NT_MEMTAG_HEAP)) return M_HEAP_TAGGING_LEVEL_TBI;
unsigned memtag_level = note_val & NT_MEMTAG_LEVEL_MASK;
switch (memtag_level) {
case NT_MEMTAG_LEVEL_ASYNC:
return M_HEAP_TAGGING_LEVEL_ASYNC;
case NT_MEMTAG_LEVEL_DEFAULT:
case NT_MEMTAG_LEVEL_SYNC:
return M_HEAP_TAGGING_LEVEL_SYNC;
default:
async_safe_fatal("unrecognized android.memtag note: level = %d", memtag_level);
}
}
// Figure out the desired memory tagging mode (sync/async, heap/globals/stack) for this executable.
// This function is called from the linker before the main executable is relocated.
__attribute__((no_sanitize("hwaddress", "memtag"))) void __libc_init_mte(const void* phdr_start,
size_t phdr_ct,
uintptr_t load_bias) {
HeapTaggingLevel level = __get_heap_tagging_level(phdr_start, phdr_ct, load_bias);
if (level == M_HEAP_TAGGING_LEVEL_SYNC || level == M_HEAP_TAGGING_LEVEL_ASYNC) {
unsigned long prctl_arg = PR_TAGGED_ADDR_ENABLE | PR_MTE_TAG_SET_NONZERO;
prctl_arg |= (level == M_HEAP_TAGGING_LEVEL_SYNC) ? PR_MTE_TCF_SYNC : PR_MTE_TCF_ASYNC;
// When entering ASYNC mode, specify that we want to allow upgrading to SYNC by OR'ing in the
// SYNC flag. But if the kernel doesn't support specifying multiple TCF modes, fall back to
// specifying a single mode.
if (prctl(PR_SET_TAGGED_ADDR_CTRL, prctl_arg | PR_MTE_TCF_SYNC, 0, 0, 0) == 0 ||
prctl(PR_SET_TAGGED_ADDR_CTRL, prctl_arg, 0, 0, 0) == 0) {
__libc_shared_globals()->initial_heap_tagging_level = level;
return;
}
}
// MTE was either not enabled, or wasn't supported on this device. Try and use
// TBI.
if (prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == 0) {
__libc_shared_globals()->initial_heap_tagging_level = M_HEAP_TAGGING_LEVEL_TBI;
}
}
#else // __aarch64__
void __libc_init_mte(const void*, size_t, uintptr_t) {}
#endif // __aarch64__
void __libc_init_profiling_handlers() {
// The dynamic variant of this function is more interesting, but this
// at least ensures that static binaries aren't killed by the kernel's
// default disposition for these two real-time signals that would have
// handlers installed if this was a dynamic binary.
signal(BIONIC_SIGNAL_PROFILER, SIG_IGN);
signal(BIONIC_SIGNAL_ART_PROFILER, SIG_IGN);
}
__noreturn static void __real_libc_init(void *raw_args,
void (*onexit)(void) __unused,
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors,
bionic_tcb* temp_tcb) {
BIONIC_STOP_UNWIND;
// Initialize TLS early so system calls and errno work.
KernelArgumentBlock args(raw_args);
__libc_init_main_thread_early(args, temp_tcb);
__libc_init_main_thread_late();
__libc_init_globals();
__libc_shared_globals()->init_progname = args.argv[0];
__libc_init_AT_SECURE(args.envp);
layout_static_tls(args);
__libc_init_main_thread_final();
__libc_init_common();
__libc_init_mte(reinterpret_cast<ElfW(Phdr)*>(getauxval(AT_PHDR)), getauxval(AT_PHNUM),
/*load_bias = */ 0);
__libc_init_scudo();
__libc_init_profiling_handlers();
__libc_init_fork_handler();
call_ifunc_resolvers();
apply_gnu_relro();
// Several Linux ABIs don't pass the onexit pointer, and the ones that
// do never use it. Therefore, we ignore it.
call_array(structors->preinit_array, args.argc, args.argv, args.envp);
call_array(structors->init_array, args.argc, args.argv, args.envp);
// The executable may have its own destructors listed in its .fini_array
// so we need to ensure that these are called when the program exits
// normally.
if (structors->fini_array != nullptr) {
__cxa_atexit(__libc_fini,structors->fini_array,nullptr);
}
exit(slingshot(args.argc, args.argv, args.envp));
}
extern "C" void __hwasan_init_static();
// This __libc_init() is only used for static executables, and is called from crtbegin.c.
//
// The 'structors' parameter contains pointers to various initializer
// arrays that must be run before the program's 'main' routine is launched.
__attribute__((no_sanitize("hwaddress")))
__noreturn void __libc_init(void* raw_args,
void (*onexit)(void) __unused,
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors) {
bionic_tcb temp_tcb = {};
#if __has_feature(hwaddress_sanitizer)
// Install main thread TLS early. It will be initialized later in __libc_init_main_thread. For now
// all we need is access to TLS_SLOT_SANITIZER.
__set_tls(&temp_tcb.tls_slot(0));
// Initialize HWASan enough to run instrumented code. This sets up TLS_SLOT_SANITIZER, among other
// things.
__hwasan_init_static();
// We are ready to run HWASan-instrumented code, proceed with libc initialization...
#endif
__real_libc_init(raw_args, onexit, slingshot, structors, &temp_tcb);
}
static int g_target_sdk_version{__ANDROID_API__};
extern "C" int android_get_application_target_sdk_version() {
return g_target_sdk_version;
}
extern "C" void android_set_application_target_sdk_version(int target) {
g_target_sdk_version = target;
__libc_set_target_sdk_version(target);
}
// This function is called in the dynamic linker before ifunc resolvers have run, so this file is
// compiled with -ffreestanding to avoid implicit string.h function calls. (It shouldn't strictly
// be necessary, though.)
__LIBC_HIDDEN__ libc_shared_globals* __libc_shared_globals() {
static libc_shared_globals globals;
return &globals;
}