libc/bionic/libc_init_static.cpp - android_bionic - Gitiles

 /*
  * 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 <malloc.h>
 #include <signal.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/auxv.h>
 #include <sys/mman.h>

 #include "async_safe/log.h"
 #include "heap_tagging.h"
 #include "libc_init_common.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 "private/elf_note.h"
 #include "pthread_internal.h"
 #include "sys/system_properties.h"
 #include "sysprop_helpers.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, size_t count, int argc, char* argv[], char* envp[]) {
   while (count-- > 0) {
     init_func_t* function = *list++;
     (*function)(argc, argv, envp);
   }
 }

 static void call_fini_array(void* arg) {
   structors_array_t* structors = reinterpret_cast<structors_array_t*>(arg);
   fini_func_t** array = structors->fini_array;
   size_t count = structors->fini_array_count;
   // Now call each destructor in reverse order.
   while (count-- > 0) {
     fini_func_t* function = array[count];
     (*function)();
   }
 }

 #if defined(__arm__) || defined(__i386__)  // Legacy architectures used REL...
 extern __LIBC_HIDDEN__ __attribute__((weak)) ElfW(Rel) __rel_iplt_start[], __rel_iplt_end[];

 static void call_ifunc_resolvers() {
   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);
   }
 }
 #else  // ...but modern architectures use RELA instead.
 extern __LIBC_HIDDEN__ __attribute__((weak)) ElfW(Rela) __rela_iplt_start[], __rela_iplt_end[];

 static void call_ifunc_resolvers() {
   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);
   }
 }
 #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_align(mod.segment.aligned_size.align.value)) {
       async_safe_fatal("error: TLS segment alignment in \"%s\" is not a power of 2: %zu\n",
                        progname, mod.segment.aligned_size.align.value);
     }
     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();
 }

 #ifdef __aarch64__
 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 (!__find_elf_note(NT_ANDROID_TYPE_MEMTAG, "Android", phdr_start, phdr_ct, &note, &desc,
                        load_bias)) {
     return M_HEAP_TAGGING_LEVEL_TBI;
   }

   // Previously (in Android 12), if the note was != 4 bytes, we check-failed
   // here. Let's be more permissive to allow future expansion.
   if (note->n_descsz < 4) {
     async_safe_fatal("unrecognized android.memtag note: n_descsz = %d, expected >= 4",
                      note->n_descsz);
   }

   // `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;

   // Warning: In Android 12, any value outside of bits [0..3] resulted in a check-fail.
   if (!(note_val & (NT_MEMTAG_HEAP | NT_MEMTAG_STACK))) {
     async_safe_format_log(ANDROID_LOG_INFO, "libc",
                           "unrecognised memtag note_val did not specificy heap or stack: %u",
                           note_val);
     return M_HEAP_TAGGING_LEVEL_TBI;
   }

   unsigned mode = note_val & NT_MEMTAG_LEVEL_MASK;
   switch (mode) {
     case NT_MEMTAG_LEVEL_NONE:
       // Note, previously (in Android 12), NT_MEMTAG_LEVEL_NONE was
       // NT_MEMTAG_LEVEL_DEFAULT, which implied SYNC mode. This was never used
       // by anyone, but we note it (heh) here for posterity, in case the zero
       // level becomes meaningful, and binaries with this note can be executed
       // on Android 12 devices.
       return M_HEAP_TAGGING_LEVEL_TBI;
     case NT_MEMTAG_LEVEL_ASYNC:
       return M_HEAP_TAGGING_LEVEL_ASYNC;
     case NT_MEMTAG_LEVEL_SYNC:
     default:
       // We allow future extensions to specify mode 3 (currently unused), with
       // the idea that it might be used for ASYMM mode or something else. On
       // this version of Android, it falls back to SYNC mode.
       return M_HEAP_TAGGING_LEVEL_SYNC;
   }
 }

 // 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.";
   static const char kMemtagGlobalSysprop[] = "persist.arm64.memtag.default";
   static const char kMemtagOverrideSyspropPrefix[] =
       "persist.device_config.memory_safety_native.mode_override.process.";

   const char* progname = __libc_shared_globals()->init_progname;
   if (progname == nullptr) return false;

   const char* basename = __gnu_basename(progname);

   char options_str[PROP_VALUE_MAX];
   char sysprop_name[512];
   async_safe_format_buffer(sysprop_name, sizeof(sysprop_name), "%s%s", kMemtagPrognameSyspropPrefix,
                            basename);
   char remote_sysprop_name[512];
   async_safe_format_buffer(remote_sysprop_name, sizeof(remote_sysprop_name), "%s%s",
                            kMemtagOverrideSyspropPrefix, basename);
   const char* sys_prop_names[] = {sysprop_name, remote_sysprop_name, kMemtagGlobalSysprop};

   if (!get_config_from_env_or_sysprops("MEMTAG_OPTIONS", sys_prop_names, arraysize(sys_prop_names),
                                        options_str, sizeof(options_str))) {
     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_tagging_level(const memtag_dynamic_entries_t* memtag_dynamic_entries,
                                             const void* phdr_start, size_t phdr_ct,
                                             uintptr_t load_bias, bool* stack) {
   HeapTaggingLevel level = M_HEAP_TAGGING_LEVEL_TBI;

   // If the dynamic entries exist, use those. Otherwise, fall back to the old
   // Android note, which is still used for fully static executables. When
   // -fsanitize=memtag* is used in newer toolchains, currently both the dynamic
   // entries and the old note are created, but we'd expect to move to just the
   // dynamic entries for dynamically linked executables in the future. In
   // addition, there's still some cleanup of the build system (that uses a
   // manually-constructed note) needed. For more information about the dynamic
   // entries, see:
   // https://github.com/ARM-software/abi-aa/blob/main/memtagabielf64/memtagabielf64.rst#dynamic-section
   if (memtag_dynamic_entries && memtag_dynamic_entries->has_memtag_mode) {
     switch (memtag_dynamic_entries->memtag_mode) {
       case 0:
         level = M_HEAP_TAGGING_LEVEL_SYNC;
         break;
       case 1:
         level = M_HEAP_TAGGING_LEVEL_ASYNC;
         break;
       default:
         async_safe_format_log(ANDROID_LOG_INFO, "libc",
                               "unrecognised DT_AARCH64_MEMTAG_MODE value: %u",
                               memtag_dynamic_entries->memtag_mode);
     }
     *stack = memtag_dynamic_entries->memtag_stack;
   } else {
     level = __get_memtag_level_from_note(reinterpret_cast<const ElfW(Phdr)*>(phdr_start), phdr_ct,
                                          load_bias, stack);
   }

   // We can't short-circuit the environment override, as `stack` is still inherited from the
   // binary's settings.
   get_environment_memtag_setting(&level);
   return level;
 }

 static void __enable_mte_signal_handler(int, siginfo_t* info, void*) {
   if (info->si_code != SI_TIMER) {
     async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Got BIONIC_ENABLE_MTE not from SI_TIMER");
     return;
   }
   int tagged_addr_ctrl = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
   if (tagged_addr_ctrl < 0) {
     async_safe_fatal("failed to PR_GET_TAGGED_ADDR_CTRL: %m");
   }
   if ((tagged_addr_ctrl & PR_MTE_TCF_MASK) != PR_MTE_TCF_NONE) {
     return;
   }
   async_safe_format_log(ANDROID_LOG_INFO, "libc",
                         "Re-enabling MTE, value: %x (tagged_addr_ctrl %lu)",
                         info->si_value.sival_int, info->si_value.sival_int & PR_MTE_TCF_MASK);
   tagged_addr_ctrl =
       (tagged_addr_ctrl & ~PR_MTE_TCF_MASK) | (info->si_value.sival_int & PR_MTE_TCF_MASK);
   if (prctl(PR_SET_TAGGED_ADDR_CTRL, tagged_addr_ctrl, 0, 0, 0) < 0) {
     async_safe_fatal("failed to PR_SET_TAGGED_ADDR_CTRL %d: %m", tagged_addr_ctrl);
   }
 }

 static int64_t __get_memtag_upgrade_secs() {
   char* env = getenv("BIONIC_MEMTAG_UPGRADE_SECS");
   if (!env) return 0;
   int64_t timed_upgrade = 0;
   static const char kAppProcessName[] = "app_process64";
   const char* progname = __libc_shared_globals()->init_progname;
   progname = progname ? __gnu_basename(progname) : nullptr;
   // disable timed upgrade for zygote, as the thread spawned will violate the requirement
   // that it be single-threaded.
   if (!progname || strncmp(progname, kAppProcessName, sizeof(kAppProcessName)) != 0) {
     char* endptr;
     timed_upgrade = strtoll(env, &endptr, 10);
     if (*endptr != '\0' || timed_upgrade < 0) {
       async_safe_format_log(ANDROID_LOG_ERROR, "libc",
                             "Invalid value for BIONIC_MEMTAG_UPGRADE_SECS: %s", env);
       timed_upgrade = 0;
     }
   }
   // Make sure that this does not get passed to potential processes inheriting
   // this environment.
   unsetenv("BIONIC_MEMTAG_UPGRADE_SECS");
   return timed_upgrade;
 }

 // 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 memtag_dynamic_entries_t* memtag_dynamic_entries, const void* phdr_start, size_t phdr_ct,
     uintptr_t load_bias, void* stack_top) {
   bool memtag_stack = false;
   HeapTaggingLevel level =
       __get_tagging_level(memtag_dynamic_entries, phdr_start, phdr_ct, load_bias, &memtag_stack);
   // initial_memtag_stack is used by the linker (in linker.cpp) to communicate than any library
   // linked by this executable enables memtag-stack.
   // memtag_stack is also set for static executables if they request memtag stack via the note,
   // in which case it will differ from initial_memtag_stack.
   if (__libc_shared_globals()->initial_memtag_stack || memtag_stack) {
     memtag_stack = true;
     __libc_shared_globals()->initial_memtag_stack_abi = true;
     __get_bionic_tcb()->tls_slot(TLS_SLOT_STACK_MTE) = __allocate_stack_mte_ringbuffer(0, nullptr);
   }
   if (int64_t timed_upgrade = __get_memtag_upgrade_secs()) {
     if (level == M_HEAP_TAGGING_LEVEL_ASYNC) {
       async_safe_format_log(ANDROID_LOG_INFO, "libc",
                             "Attempting timed MTE upgrade from async to sync.");
       __libc_shared_globals()->heap_tagging_upgrade_timer_sec = timed_upgrade;
       level = M_HEAP_TAGGING_LEVEL_SYNC;
     } else if (level != M_HEAP_TAGGING_LEVEL_SYNC) {
       async_safe_format_log(
           ANDROID_LOG_ERROR, "libc",
           "Requested timed MTE upgrade from invalid %s to sync. Ignoring.",
           DescribeTaggingLevel(level));
     }
   }
   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;
       __libc_shared_globals()->initial_memtag_stack = memtag_stack;

       if (memtag_stack) {
         void* pg_start =
             reinterpret_cast<void*>(page_start(reinterpret_cast<uintptr_t>(stack_top)));
         if (mprotect(pg_start, page_size(), PROT_READ | PROT_WRITE | PROT_MTE | PROT_GROWSDOWN)) {
           async_safe_fatal("error: failed to set PROT_MTE on main thread stack: %m");
         }
       }
       struct sigaction action = {};
       action.sa_flags = SA_SIGINFO | SA_RESTART;
       action.sa_sigaction = __enable_mte_signal_handler;
       sigaction(BIONIC_ENABLE_MTE, &action, nullptr);
       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;
   }
   // We did not enable MTE, so we do not need to arm the upgrade timer.
   __libc_shared_globals()->heap_tagging_upgrade_timer_sec = 0;
   // We also didn't enable memtag_stack.
   __libc_shared_globals()->initial_memtag_stack = false;
 }
 #else   // __aarch64__
 void __libc_init_mte(const memtag_dynamic_entries_t*, const void*, size_t, uintptr_t, void*) {}
 #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);
 }

 __attribute__((no_sanitize("memtag"))) __noreturn static void __real_libc_init(
     KernelArgumentBlock& args, 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;

   __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(/*memtag_dynamic_entries=*/nullptr,
                   reinterpret_cast<ElfW(Phdr)*>(getauxval(AT_PHDR)), getauxval(AT_PHNUM),
                   /*load_bias = */ 0, /*stack_top = */ raw_args);
   __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, structors->preinit_array_count, args.argc, args.argv,
              args.envp);
   call_array(structors->init_array, structors->init_array_count, 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_count > 0) {
     __cxa_atexit(call_fini_array, const_cast<structors_array_t*>(structors), nullptr);
   }

   __libc_init_mte_late();

   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", "memtag"))) __noreturn void __libc_init(
     void* raw_args, void (*onexit)(void) __unused, int (*slingshot)(int, char**, char**),
     structors_array_t const* const structors) {
   // We _really_ don't want the compiler to call memset() here,
   // but it's done so before for riscv64 (http://b/365618934),
   // so we have to force it to behave.
   bionic_tcb temp_tcb __attribute__((uninitialized));
   __builtin_memset_inline(&temp_tcb, 0, sizeof(temp_tcb));

   KernelArgumentBlock args(raw_args);
 #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 and read auxval for the page size.
   __set_tls(&temp_tcb.tls_slot(0));
   __libc_shared_globals()->auxv = args.auxv;
   // 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(args, 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;
 }
	/*
	* 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 <malloc.h>
	#include <signal.h>
	#include <stddef.h>
	#include <stdint.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <sys/auxv.h>
	#include <sys/mman.h>

	#include "async_safe/log.h"
	#include "heap_tagging.h"
	#include "libc_init_common.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 "private/elf_note.h"
	#include "pthread_internal.h"
	#include "sys/system_properties.h"
	#include "sysprop_helpers.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, size_t count, int argc, char* argv[], char* envp[]) {
	while (count-- > 0) {
	init_func_t* function = *list++;
	(*function)(argc, argv, envp);
	}
	}

	static void call_fini_array(void* arg) {
	structors_array_t* structors = reinterpret_cast<structors_array_t*>(arg);
	fini_func_t** array = structors->fini_array;
	size_t count = structors->fini_array_count;
	// Now call each destructor in reverse order.
	while (count-- > 0) {
	fini_func_t* function = array[count];
	(*function)();
	}
	}

	#if defined(__arm__) \|\| defined(__i386__) // Legacy architectures used REL...
	extern __LIBC_HIDDEN__ __attribute__((weak)) ElfW(Rel) __rel_iplt_start[], __rel_iplt_end[];

	static void call_ifunc_resolvers() {
	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);
	}
	}
	#else // ...but modern architectures use RELA instead.
	extern __LIBC_HIDDEN__ __attribute__((weak)) ElfW(Rela) __rela_iplt_start[], __rela_iplt_end[];

	static void call_ifunc_resolvers() {
	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);
	}
	}
	#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_align(mod.segment.aligned_size.align.value)) {
	async_safe_fatal("error: TLS segment alignment in \"%s\" is not a power of 2: %zu\n",
	progname, mod.segment.aligned_size.align.value);
	}
	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();
	}

	#ifdef __aarch64__
	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 (!__find_elf_note(NT_ANDROID_TYPE_MEMTAG, "Android", phdr_start, phdr_ct, &note, &desc,
	load_bias)) {
	return M_HEAP_TAGGING_LEVEL_TBI;
	}

	// Previously (in Android 12), if the note was != 4 bytes, we check-failed
	// here. Let's be more permissive to allow future expansion.
	if (note->n_descsz < 4) {
	async_safe_fatal("unrecognized android.memtag note: n_descsz = %d, expected >= 4",
	note->n_descsz);
	}

	// `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;

	// Warning: In Android 12, any value outside of bits [0..3] resulted in a check-fail.
	if (!(note_val & (NT_MEMTAG_HEAP \| NT_MEMTAG_STACK))) {
	async_safe_format_log(ANDROID_LOG_INFO, "libc",
	"unrecognised memtag note_val did not specificy heap or stack: %u",
	note_val);
	return M_HEAP_TAGGING_LEVEL_TBI;
	}

	unsigned mode = note_val & NT_MEMTAG_LEVEL_MASK;
	switch (mode) {
	case NT_MEMTAG_LEVEL_NONE:
	// Note, previously (in Android 12), NT_MEMTAG_LEVEL_NONE was
	// NT_MEMTAG_LEVEL_DEFAULT, which implied SYNC mode. This was never used
	// by anyone, but we note it (heh) here for posterity, in case the zero
	// level becomes meaningful, and binaries with this note can be executed
	// on Android 12 devices.
	return M_HEAP_TAGGING_LEVEL_TBI;
	case NT_MEMTAG_LEVEL_ASYNC:
	return M_HEAP_TAGGING_LEVEL_ASYNC;
	case NT_MEMTAG_LEVEL_SYNC:
	default:
	// We allow future extensions to specify mode 3 (currently unused), with
	// the idea that it might be used for ASYMM mode or something else. On
	// this version of Android, it falls back to SYNC mode.
	return M_HEAP_TAGGING_LEVEL_SYNC;
	}
	}

	// 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.";
	static const char kMemtagGlobalSysprop[] = "persist.arm64.memtag.default";
	static const char kMemtagOverrideSyspropPrefix[] =
	"persist.device_config.memory_safety_native.mode_override.process.";

	const char* progname = __libc_shared_globals()->init_progname;
	if (progname == nullptr) return false;

	const char* basename = __gnu_basename(progname);

	char options_str[PROP_VALUE_MAX];
	char sysprop_name[512];
	async_safe_format_buffer(sysprop_name, sizeof(sysprop_name), "%s%s", kMemtagPrognameSyspropPrefix,
	basename);
	char remote_sysprop_name[512];
	async_safe_format_buffer(remote_sysprop_name, sizeof(remote_sysprop_name), "%s%s",
	kMemtagOverrideSyspropPrefix, basename);
	const char* sys_prop_names[] = {sysprop_name, remote_sysprop_name, kMemtagGlobalSysprop};

	if (!get_config_from_env_or_sysprops("MEMTAG_OPTIONS", sys_prop_names, arraysize(sys_prop_names),
	options_str, sizeof(options_str))) {
	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_tagging_level(const memtag_dynamic_entries_t* memtag_dynamic_entries,
	const void* phdr_start, size_t phdr_ct,
	uintptr_t load_bias, bool* stack) {
	HeapTaggingLevel level = M_HEAP_TAGGING_LEVEL_TBI;

	// If the dynamic entries exist, use those. Otherwise, fall back to the old
	// Android note, which is still used for fully static executables. When
	// -fsanitize=memtag* is used in newer toolchains, currently both the dynamic
	// entries and the old note are created, but we'd expect to move to just the
	// dynamic entries for dynamically linked executables in the future. In
	// addition, there's still some cleanup of the build system (that uses a
	// manually-constructed note) needed. For more information about the dynamic
	// entries, see:
	// https://github.com/ARM-software/abi-aa/blob/main/memtagabielf64/memtagabielf64.rst#dynamic-section
	if (memtag_dynamic_entries && memtag_dynamic_entries->has_memtag_mode) {
	switch (memtag_dynamic_entries->memtag_mode) {
	case 0:
	level = M_HEAP_TAGGING_LEVEL_SYNC;
	break;
	case 1:
	level = M_HEAP_TAGGING_LEVEL_ASYNC;
	break;
	default:
	async_safe_format_log(ANDROID_LOG_INFO, "libc",
	"unrecognised DT_AARCH64_MEMTAG_MODE value: %u",
	memtag_dynamic_entries->memtag_mode);
	}
	*stack = memtag_dynamic_entries->memtag_stack;
	} else {
	level = __get_memtag_level_from_note(reinterpret_cast<const ElfW(Phdr)*>(phdr_start), phdr_ct,
	load_bias, stack);
	}

	// We can't short-circuit the environment override, as `stack` is still inherited from the
	// binary's settings.
	get_environment_memtag_setting(&level);
	return level;
	}

	static void __enable_mte_signal_handler(int, siginfo_t* info, void*) {
	if (info->si_code != SI_TIMER) {
	async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Got BIONIC_ENABLE_MTE not from SI_TIMER");
	return;
	}
	int tagged_addr_ctrl = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
	if (tagged_addr_ctrl < 0) {
	async_safe_fatal("failed to PR_GET_TAGGED_ADDR_CTRL: %m");
	}
	if ((tagged_addr_ctrl & PR_MTE_TCF_MASK) != PR_MTE_TCF_NONE) {
	return;
	}
	async_safe_format_log(ANDROID_LOG_INFO, "libc",
	"Re-enabling MTE, value: %x (tagged_addr_ctrl %lu)",
	info->si_value.sival_int, info->si_value.sival_int & PR_MTE_TCF_MASK);
	tagged_addr_ctrl =
	(tagged_addr_ctrl & ~PR_MTE_TCF_MASK) \| (info->si_value.sival_int & PR_MTE_TCF_MASK);
	if (prctl(PR_SET_TAGGED_ADDR_CTRL, tagged_addr_ctrl, 0, 0, 0) < 0) {
	async_safe_fatal("failed to PR_SET_TAGGED_ADDR_CTRL %d: %m", tagged_addr_ctrl);
	}
	}

	static int64_t __get_memtag_upgrade_secs() {
	char* env = getenv("BIONIC_MEMTAG_UPGRADE_SECS");
	if (!env) return 0;
	int64_t timed_upgrade = 0;
	static const char kAppProcessName[] = "app_process64";
	const char* progname = __libc_shared_globals()->init_progname;
	progname = progname ? __gnu_basename(progname) : nullptr;
	// disable timed upgrade for zygote, as the thread spawned will violate the requirement
	// that it be single-threaded.
	if (!progname \|\| strncmp(progname, kAppProcessName, sizeof(kAppProcessName)) != 0) {
	char* endptr;
	timed_upgrade = strtoll(env, &endptr, 10);
	if (*endptr != '\0' \|\| timed_upgrade < 0) {
	async_safe_format_log(ANDROID_LOG_ERROR, "libc",
	"Invalid value for BIONIC_MEMTAG_UPGRADE_SECS: %s", env);
	timed_upgrade = 0;
	}
	}
	// Make sure that this does not get passed to potential processes inheriting
	// this environment.
	unsetenv("BIONIC_MEMTAG_UPGRADE_SECS");
	return timed_upgrade;
	}

	// 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 memtag_dynamic_entries_t* memtag_dynamic_entries, const void* phdr_start, size_t phdr_ct,
	uintptr_t load_bias, void* stack_top) {
	bool memtag_stack = false;
	HeapTaggingLevel level =
	__get_tagging_level(memtag_dynamic_entries, phdr_start, phdr_ct, load_bias, &memtag_stack);
	// initial_memtag_stack is used by the linker (in linker.cpp) to communicate than any library
	// linked by this executable enables memtag-stack.
	// memtag_stack is also set for static executables if they request memtag stack via the note,
	// in which case it will differ from initial_memtag_stack.
	if (__libc_shared_globals()->initial_memtag_stack \|\| memtag_stack) {
	memtag_stack = true;
	__libc_shared_globals()->initial_memtag_stack_abi = true;
	__get_bionic_tcb()->tls_slot(TLS_SLOT_STACK_MTE) = __allocate_stack_mte_ringbuffer(0, nullptr);
	}
	if (int64_t timed_upgrade = __get_memtag_upgrade_secs()) {
	if (level == M_HEAP_TAGGING_LEVEL_ASYNC) {
	async_safe_format_log(ANDROID_LOG_INFO, "libc",
	"Attempting timed MTE upgrade from async to sync.");
	__libc_shared_globals()->heap_tagging_upgrade_timer_sec = timed_upgrade;
	level = M_HEAP_TAGGING_LEVEL_SYNC;
	} else if (level != M_HEAP_TAGGING_LEVEL_SYNC) {
	async_safe_format_log(
	ANDROID_LOG_ERROR, "libc",
	"Requested timed MTE upgrade from invalid %s to sync. Ignoring.",
	DescribeTaggingLevel(level));
	}
	}
	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;
	__libc_shared_globals()->initial_memtag_stack = memtag_stack;

	if (memtag_stack) {
	void* pg_start =
	reinterpret_cast<void*>(page_start(reinterpret_cast<uintptr_t>(stack_top)));
	if (mprotect(pg_start, page_size(), PROT_READ \| PROT_WRITE \| PROT_MTE \| PROT_GROWSDOWN)) {
	async_safe_fatal("error: failed to set PROT_MTE on main thread stack: %m");
	}
	}
	struct sigaction action = {};
	action.sa_flags = SA_SIGINFO \| SA_RESTART;
	action.sa_sigaction = __enable_mte_signal_handler;
	sigaction(BIONIC_ENABLE_MTE, &action, nullptr);
	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;
	}
	// We did not enable MTE, so we do not need to arm the upgrade timer.
	__libc_shared_globals()->heap_tagging_upgrade_timer_sec = 0;
	// We also didn't enable memtag_stack.
	__libc_shared_globals()->initial_memtag_stack = false;
	}
	#else // __aarch64__
	void __libc_init_mte(const memtag_dynamic_entries_t, const void, size_t, uintptr_t, void*) {}
	#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);
	}

	__attribute__((no_sanitize("memtag"))) __noreturn static void __real_libc_init(
	KernelArgumentBlock& args, 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;

	__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(/memtag_dynamic_entries=/nullptr,
	reinterpret_cast<ElfW(Phdr)*>(getauxval(AT_PHDR)), getauxval(AT_PHNUM),
	/load_bias = / 0, /stack_top = / raw_args);
	__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, structors->preinit_array_count, args.argc, args.argv,
	args.envp);
	call_array(structors->init_array, structors->init_array_count, 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_count > 0) {
	__cxa_atexit(call_fini_array, const_cast<structors_array_t*>(structors), nullptr);
	}

	__libc_init_mte_late();

	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", "memtag"))) __noreturn void __libc_init(
	void* raw_args, void (onexit)(void) __unused, int (slingshot)(int, char, char),
	structors_array_t const* const structors) {
	// We _really_ don't want the compiler to call memset() here,
	// but it's done so before for riscv64 (http://b/365618934),
	// so we have to force it to behave.
	bionic_tcb temp_tcb __attribute__((uninitialized));
	__builtin_memset_inline(&temp_tcb, 0, sizeof(temp_tcb));

	KernelArgumentBlock args(raw_args);
	#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 and read auxval for the page size.
	__set_tls(&temp_tcb.tls_slot(0));
	__libc_shared_globals()->auxv = args.auxv;
	// 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(args, 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;
	}