Merge changes Ifbb55372,I26f5833b,I19ec542e,Ibe203918 into main

* changes:
  Implement deterministic MTE globals for dlext RELRO sharing
  Fix dlext tests for MTE globals
  Re-land tests for MTE globals
  Re-land linker support for MTE globals
diff --git a/libc/bionic/__libc_init_main_thread.cpp b/libc/bionic/__libc_init_main_thread.cpp
index 1b539f2..0d557f1 100644
--- a/libc/bionic/__libc_init_main_thread.cpp
+++ b/libc/bionic/__libc_init_main_thread.cpp
@@ -44,7 +44,7 @@
 // Declared in "private/bionic_ssp.h".
 uintptr_t __stack_chk_guard = 0;
 
-static pthread_internal_t main_thread;
+BIONIC_USED_BEFORE_LINKER_RELOCATES static pthread_internal_t main_thread;
 
 // Setup for the main thread. For dynamic executables, this is called by the
 // linker _before_ libc is mapped in memory. This means that all writes to
diff --git a/libc/bionic/bionic_call_ifunc_resolver.cpp b/libc/bionic/bionic_call_ifunc_resolver.cpp
index e44d998..d5a812c 100644
--- a/libc/bionic/bionic_call_ifunc_resolver.cpp
+++ b/libc/bionic/bionic_call_ifunc_resolver.cpp
@@ -31,6 +31,7 @@
 #include <sys/hwprobe.h>
 #include <sys/ifunc.h>
 
+#include "bionic/macros.h"
 #include "private/bionic_auxv.h"
 
 // This code is called in the linker before it has been relocated, so minimize calls into other
@@ -40,8 +41,8 @@
 ElfW(Addr) __bionic_call_ifunc_resolver(ElfW(Addr) resolver_addr) {
 #if defined(__aarch64__)
   typedef ElfW(Addr) (*ifunc_resolver_t)(uint64_t, __ifunc_arg_t*);
-  static __ifunc_arg_t arg;
-  static bool initialized = false;
+  BIONIC_USED_BEFORE_LINKER_RELOCATES static __ifunc_arg_t arg;
+  BIONIC_USED_BEFORE_LINKER_RELOCATES static bool initialized = false;
   if (!initialized) {
     initialized = true;
     arg._size = sizeof(__ifunc_arg_t);
diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index 7c46113..ae86da1 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -344,19 +344,12 @@
 // 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) {
+    uintptr_t load_bias) {
   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);
-  }
+  __libc_shared_globals()->initial_memtag_stack = memtag_stack;
+
   if (int64_t timed_upgrade = __get_memtag_upgrade_secs()) {
     if (level == M_HEAP_TAGGING_LEVEL_ASYNC) {
       async_safe_format_log(ANDROID_LOG_INFO, "libc",
@@ -380,15 +373,7 @@
     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;
@@ -404,11 +389,36 @@
   }
   // 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;
 }
+
+// Figure out whether we need to map the stack as PROT_MTE.
+// For dynamic executables, this has to be called after loading all
+// DT_NEEDED libraries, in case one of them needs stack MTE.
+__attribute__((no_sanitize("hwaddress", "memtag"))) void __libc_init_mte_stack(void* stack_top) {
+  if (!__libc_shared_globals()->initial_memtag_stack) {
+    return;
+  }
+
+  // Even if the device doesn't support MTE, we have to allocate stack
+  // history buffers for code compiled for stack MTE. That is because the
+  // codegen expects a buffer to be present in TLS_SLOT_STACK_MTE either
+  // way.
+  __libc_shared_globals()->initial_memtag_stack_abi = true;
+  __get_bionic_tcb()->tls_slot(TLS_SLOT_STACK_MTE) = __allocate_stack_mte_ringbuffer(0, nullptr);
+
+  if (!__libc_mte_enabled()) {
+    __libc_shared_globals()->initial_memtag_stack = false;
+    return;
+  }
+  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");
+  }
+}
+
 #else   // __aarch64__
-void __libc_init_mte(const memtag_dynamic_entries_t*, const void*, size_t, uintptr_t, void*) {}
+void __libc_init_mte(const memtag_dynamic_entries_t*, const void*, size_t, uintptr_t) {}
+void __libc_init_mte_stack(void*) {}
 #endif  // __aarch64__
 
 void __libc_init_profiling_handlers() {
@@ -436,7 +446,8 @@
   __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);
+                  /*load_bias = */ 0);
+  __libc_init_mte_stack(/*stack_top = */ raw_args);
   __libc_init_scudo();
   __libc_init_profiling_handlers();
   __libc_init_fork_handler();
@@ -508,6 +519,11 @@
 // 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;
+  BIONIC_USED_BEFORE_LINKER_RELOCATES static libc_shared_globals globals;
   return &globals;
 }
+
+__LIBC_HIDDEN__ bool __libc_mte_enabled() {
+  HeapTaggingLevel lvl = __libc_shared_globals()->initial_heap_tagging_level;
+  return lvl == M_HEAP_TAGGING_LEVEL_SYNC || lvl == M_HEAP_TAGGING_LEVEL_ASYNC;
+}
diff --git a/libc/platform/bionic/macros.h b/libc/platform/bionic/macros.h
index 93268c1..837583e 100644
--- a/libc/platform/bionic/macros.h
+++ b/libc/platform/bionic/macros.h
@@ -97,3 +97,26 @@
 static inline T* _Nonnull untag_address(T* _Nonnull p) {
   return reinterpret_cast<T*>(untag_address(reinterpret_cast<uintptr_t>(p)));
 }
+
+// MTE globals protects internal and external global variables. One of the main
+// things that MTE globals does is force all global variable accesses to go
+// through the GOT. In the linker though, some global variables are accessed (or
+// address-taken) prior to relocations being processed. Because relocations
+// haven't run yet, the GOT entry hasn't been populated, and this leads to
+// crashes. Thus, any globals used by the linker prior to relocation should be
+// annotated with this attribute, which suppresses tagging of this global
+// variable, restoring the pc-relative address computation.
+//
+// A way to find global variables that need this attribute is to build the
+// linker/libc with `SANITIZE_TARGET=memtag_globals`, push them onto a device
+// (it doesn't have to be MTE capable), and then run an executable using
+// LD_LIBRARY_PATH and using the linker in interpreter mode (e.g.
+// `LD_LIBRARY_PATH=/data/tmp/ /data/tmp/linker64 /data/tmp/my_binary`). A
+// good heuristic is that the global variable is in a file that should be
+// compiled with `-ffreestanding` (but there are global variables there that
+// don't need thisattribute).
+#if __has_feature(memtag_globals)
+#define BIONIC_USED_BEFORE_LINKER_RELOCATES __attribute__((no_sanitize("memtag")))
+#else  // __has_feature(memtag_globals)
+#define BIONIC_USED_BEFORE_LINKER_RELOCATES
+#endif  // __has_feature(memtag_globals)
diff --git a/libc/platform/bionic/mte.h b/libc/platform/bionic/mte.h
index 98b3d27..423ed0f 100644
--- a/libc/platform/bionic/mte.h
+++ b/libc/platform/bionic/mte.h
@@ -28,6 +28,7 @@
 
 #pragma once
 
+#include <stddef.h>
 #include <sys/auxv.h>
 #include <sys/mman.h>
 #include <sys/prctl.h>
@@ -49,6 +50,36 @@
   return supported;
 }
 
+inline void* get_tagged_address(const void* ptr) {
+#if defined(__aarch64__)
+  if (mte_supported()) {
+    __asm__ __volatile__(".arch_extension mte; ldg %0, [%0]" : "+r"(ptr));
+  }
+#endif  // aarch64
+  return const_cast<void*>(ptr);
+}
+
+// Inserts a random tag tag to `ptr`, using any of the set lower 16 bits in
+// `mask` to exclude the corresponding tag from being generated. Note: This does
+// not tag memory. This generates a pointer to be used with set_memory_tag.
+inline void* insert_random_tag(const void* ptr, __attribute__((unused)) uint64_t mask = 0) {
+#if defined(__aarch64__)
+  if (mte_supported() && ptr) {
+    __asm__ __volatile__(".arch_extension mte; irg %0, %0, %1" : "+r"(ptr) : "r"(mask));
+  }
+#endif  // aarch64
+  return const_cast<void*>(ptr);
+}
+
+// Stores the address tag in `ptr` to memory, at `ptr`.
+inline void set_memory_tag(__attribute__((unused)) void* ptr) {
+#if defined(__aarch64__)
+  if (mte_supported()) {
+    __asm__ __volatile__(".arch_extension mte; stg %0, [%0]" : "+r"(ptr));
+  }
+#endif  // aarch64
+}
+
 #ifdef __aarch64__
 class ScopedDisableMTE {
   size_t prev_tco_;
diff --git a/libc/private/bionic_globals.h b/libc/private/bionic_globals.h
index a1bebda..02713fc 100644
--- a/libc/private/bionic_globals.h
+++ b/libc/private/bionic_globals.h
@@ -157,6 +157,7 @@
 };
 
 __LIBC_HIDDEN__ libc_shared_globals* __libc_shared_globals();
+__LIBC_HIDDEN__ bool __libc_mte_enabled();
 __LIBC_HIDDEN__ void __libc_init_fdsan();
 __LIBC_HIDDEN__ void __libc_init_fdtrack();
 __LIBC_HIDDEN__ void __libc_init_profiling_handlers();
diff --git a/linker/Android.bp b/linker/Android.bp
index a06ca29..847a9b2 100644
--- a/linker/Android.bp
+++ b/linker/Android.bp
@@ -108,6 +108,12 @@
 
     // We need to access Bionic private headers in the linker.
     include_dirs: ["bionic/libc"],
+
+    sanitize: {
+        // Supporting memtag_globals in the linker would be tricky,
+        // because it relocates itself very early.
+        memtag_globals: false,
+    },
 }
 
 // ========================================================
diff --git a/linker/dlfcn.cpp b/linker/dlfcn.cpp
index fee19f4..82f2728 100644
--- a/linker/dlfcn.cpp
+++ b/linker/dlfcn.cpp
@@ -331,6 +331,7 @@
     __libdl_info->gnu_bloom_filter_ = linker_si.gnu_bloom_filter_;
     __libdl_info->gnu_bucket_ = linker_si.gnu_bucket_;
     __libdl_info->gnu_chain_ = linker_si.gnu_chain_;
+    __libdl_info->memtag_dynamic_entries_ = linker_si.memtag_dynamic_entries_;
 
     __libdl_info->ref_count_ = 1;
     __libdl_info->strtab_size_ = linker_si.strtab_size_;
diff --git a/linker/linker.cpp b/linker/linker.cpp
index 88d02dc..ed3f121 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -51,6 +51,7 @@
 #include <android-base/scopeguard.h>
 #include <async_safe/log.h>
 #include <bionic/pthread_internal.h>
+#include <platform/bionic/mte.h>
 
 // Private C library headers.
 
@@ -1697,11 +1698,19 @@
     }
   }
 
+  // The WebView loader uses RELRO sharing in order to promote page sharing of the large RELRO
+  // segment, as it's full of C++ vtables. Because MTE globals, by default, applies random tags to
+  // each global variable, the RELRO segment is polluted and unique for each process. In order to
+  // allow sharing, but still provide some protection, we use deterministic global tagging schemes
+  // for DSOs that are loaded through android_dlopen_ext, such as those loaded by WebView.
+  bool deterministic_memtag_globals =
+      extinfo && extinfo->flags & (ANDROID_DLEXT_WRITE_RELRO | ANDROID_DLEXT_USE_RELRO);
+
   // Step 3: pre-link all DT_NEEDED libraries in breadth first order.
   bool any_memtag_stack = false;
   for (auto&& task : load_tasks) {
     soinfo* si = task->get_soinfo();
-    if (!si->is_linked() && !si->prelink_image()) {
+    if (!si->is_linked() && !si->prelink_image(deterministic_memtag_globals)) {
       return false;
     }
     // si->memtag_stack() needs to be called after si->prelink_image() which populates
@@ -2361,7 +2370,7 @@
         void* tls_block = get_tls_block_for_this_thread(tls_module, /*should_alloc=*/true);
         *symbol = static_cast<char*>(tls_block) + sym->st_value;
       } else {
-        *symbol = reinterpret_cast<void*>(found->resolve_symbol_address(sym));
+        *symbol = get_tagged_address(reinterpret_cast<void*>(found->resolve_symbol_address(sym)));
       }
       failure_guard.Disable();
       LD_LOG(kLogDlsym,
@@ -2791,15 +2800,25 @@
   return true;
 }
 
-static void apply_relr_reloc(ElfW(Addr) offset, ElfW(Addr) load_bias) {
-  ElfW(Addr) address = offset + load_bias;
-  *reinterpret_cast<ElfW(Addr)*>(address) += load_bias;
+static void apply_relr_reloc(ElfW(Addr) offset, ElfW(Addr) load_bias, bool has_memtag_globals) {
+  ElfW(Addr) destination = offset + load_bias;
+  if (!has_memtag_globals) {
+    *reinterpret_cast<ElfW(Addr)*>(destination) += load_bias;
+    return;
+  }
+
+  ElfW(Addr)* tagged_destination =
+      reinterpret_cast<ElfW(Addr)*>(get_tagged_address(reinterpret_cast<void*>(destination)));
+  ElfW(Addr) tagged_value = reinterpret_cast<ElfW(Addr)>(
+      get_tagged_address(reinterpret_cast<void*>(*tagged_destination + load_bias)));
+  *tagged_destination = tagged_value;
 }
 
 // Process relocations in SHT_RELR section (experimental).
 // Details of the encoding are described in this post:
 //   https://groups.google.com/d/msg/generic-abi/bX460iggiKg/Pi9aSwwABgAJ
-bool relocate_relr(const ElfW(Relr)* begin, const ElfW(Relr)* end, ElfW(Addr) load_bias) {
+bool relocate_relr(const ElfW(Relr) * begin, const ElfW(Relr) * end, ElfW(Addr) load_bias,
+                   bool has_memtag_globals) {
   constexpr size_t wordsize = sizeof(ElfW(Addr));
 
   ElfW(Addr) base = 0;
@@ -2810,7 +2829,7 @@
     if ((entry&1) == 0) {
       // Even entry: encodes the offset for next relocation.
       offset = static_cast<ElfW(Addr)>(entry);
-      apply_relr_reloc(offset, load_bias);
+      apply_relr_reloc(offset, load_bias, has_memtag_globals);
       // Set base offset for subsequent bitmap entries.
       base = offset + wordsize;
       continue;
@@ -2821,7 +2840,7 @@
     while (entry != 0) {
       entry >>= 1;
       if ((entry&1) != 0) {
-        apply_relr_reloc(offset, load_bias);
+        apply_relr_reloc(offset, load_bias, has_memtag_globals);
       }
       offset += wordsize;
     }
@@ -2836,7 +2855,7 @@
 // An empty list of soinfos
 static soinfo_list_t g_empty_list;
 
-bool soinfo::prelink_image() {
+bool soinfo::prelink_image(bool deterministic_memtag_globals) {
   if (flags_ & FLAG_PRELINKED) return true;
   /* Extract dynamic section */
   ElfW(Word) dynamic_flags = 0;
@@ -3325,6 +3344,18 @@
   // it each time we look up a symbol with a version.
   if (!validate_verdef_section(this)) return false;
 
+  // MTE globals requires remapping data segments with PROT_MTE as anonymous mappings, because file
+  // based mappings may not be backed by tag-capable memory (see "MAP_ANONYMOUS" on
+  // https://www.kernel.org/doc/html/latest/arch/arm64/memory-tagging-extension.html). This is only
+  // done if the binary has MTE globals (evidenced by the dynamic table entries), as it destroys
+  // page sharing. It's also only done on devices that support MTE, because the act of remapping
+  // pages is unnecessary on non-MTE devices (where we might still run MTE-globals enabled code).
+  if (should_tag_memtag_globals() &&
+      remap_memtag_globals_segments(phdr, phnum, base) == 0) {
+    tag_globals(deterministic_memtag_globals);
+    protect_memtag_globals_ro_segments(phdr, phnum, base);
+  }
+
   flags_ |= FLAG_PRELINKED;
   return true;
 }
@@ -3397,6 +3428,10 @@
     return false;
   }
 
+  if (should_tag_memtag_globals()) {
+    name_memtag_globals_segments(phdr, phnum, base, get_realpath(), vma_names_);
+  }
+
   /* Handle serializing/sharing the RELRO segment */
   if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
     if (phdr_table_serialize_gnu_relro(phdr, phnum, load_bias,
@@ -3435,6 +3470,54 @@
   return true;
 }
 
+// https://github.com/ARM-software/abi-aa/blob/main/memtagabielf64/memtagabielf64.rst#global-variable-tagging
+void soinfo::tag_globals(bool deterministic_memtag_globals) {
+  if (is_linked()) return;
+  if (flags_ & FLAG_GLOBALS_TAGGED) return;
+  flags_ |= FLAG_GLOBALS_TAGGED;
+
+  constexpr size_t kTagGranuleSize = 16;
+  const uint8_t* descriptor_stream = reinterpret_cast<const uint8_t*>(memtag_globals());
+
+  if (memtag_globalssz() == 0) {
+    DL_ERR("Invalid memtag descriptor pool size: %zu", memtag_globalssz());
+  }
+
+  uint64_t addr = load_bias;
+  uleb128_decoder decoder(descriptor_stream, memtag_globalssz());
+  // Don't ever generate tag zero, to easily distinguish between tagged and
+  // untagged globals in register/tag dumps.
+  uint64_t last_tag_mask = 1;
+  uint64_t last_tag = 1;
+  constexpr uint64_t kDistanceReservedBits = 3;
+
+  while (decoder.has_bytes()) {
+    uint64_t value = decoder.pop_front();
+    uint64_t distance = (value >> kDistanceReservedBits) * kTagGranuleSize;
+    uint64_t ngranules = value & ((1 << kDistanceReservedBits) - 1);
+    if (ngranules == 0) {
+      ngranules = decoder.pop_front() + 1;
+    }
+
+    addr += distance;
+    void* tagged_addr;
+    if (deterministic_memtag_globals) {
+      tagged_addr = reinterpret_cast<void*>(addr | (last_tag++ << 56));
+      if (last_tag > (1 << kTagGranuleSize)) last_tag = 1;
+    } else {
+      tagged_addr = insert_random_tag(reinterpret_cast<void*>(addr), last_tag_mask);
+      uint64_t tag = (reinterpret_cast<uint64_t>(tagged_addr) >> 56) & 0x0f;
+      last_tag_mask = 1 | (1 << tag);
+    }
+
+    for (size_t k = 0; k < ngranules; k++) {
+      auto* granule = static_cast<uint8_t*>(tagged_addr) + k * kTagGranuleSize;
+      set_memory_tag(static_cast<void*>(granule));
+    }
+    addr += ngranules * kTagGranuleSize;
+  }
+}
+
 static std::vector<android_namespace_t*> init_default_namespace_no_config(bool is_asan, bool is_hwasan) {
   g_default_namespace.set_isolated(false);
   auto default_ld_paths = is_asan ? kAsanDefaultLdPaths : (
diff --git a/linker/linker.h b/linker/linker.h
index ac2222d..b696fd9 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -179,7 +179,8 @@
 int get_application_target_sdk_version();
 ElfW(Versym) find_verdef_version_index(const soinfo* si, const version_info* vi);
 bool validate_verdef_section(const soinfo* si);
-bool relocate_relr(const ElfW(Relr)* begin, const ElfW(Relr)* end, ElfW(Addr) load_bias);
+bool relocate_relr(const ElfW(Relr) * begin, const ElfW(Relr) * end, ElfW(Addr) load_bias,
+                   bool has_memtag_globals);
 
 struct platform_properties {
 #if defined(__aarch64__)
diff --git a/linker/linker_main.cpp b/linker/linker_main.cpp
index 48ed723..f65f82d 100644
--- a/linker/linker_main.cpp
+++ b/linker/linker_main.cpp
@@ -46,6 +46,7 @@
 #include "linker_tls.h"
 #include "linker_utils.h"
 
+#include "platform/bionic/macros.h"
 #include "private/KernelArgumentBlock.h"
 #include "private/bionic_call_ifunc_resolver.h"
 #include "private/bionic_globals.h"
@@ -71,7 +72,9 @@
 static void set_bss_vma_name(soinfo* si);
 
 void __libc_init_mte(const memtag_dynamic_entries_t* memtag_dynamic_entries, const void* phdr_start,
-                     size_t phdr_count, uintptr_t load_bias, void* stack_top);
+                     size_t phdr_count, uintptr_t load_bias);
+
+void __libc_init_mte_stack(void* stack_top);
 
 static void __linker_cannot_link(const char* argv0) {
   __linker_error("CANNOT LINK EXECUTABLE \"%s\": %s", argv0, linker_get_error_buffer());
@@ -365,6 +368,8 @@
   init_link_map_head(*solinker);
 
 #if defined(__aarch64__)
+  __libc_init_mte(somain->memtag_dynamic_entries(), somain->phdr, somain->phnum, somain->load_bias);
+
   if (exe_to_load == nullptr) {
     // Kernel does not add PROT_BTI to executable pages of the loaded ELF.
     // Apply appropriate protections here if it is needed.
@@ -465,8 +470,7 @@
 #if defined(__aarch64__)
   // This has to happen after the find_libraries, which will have collected any possible
   // libraries that request memtag_stack in the dynamic section.
-  __libc_init_mte(somain->memtag_dynamic_entries(), somain->phdr, somain->phnum, somain->load_bias,
-                  args.argv);
+  __libc_init_mte_stack(args.argv);
 #endif
 
   linker_finalize_static_tls();
@@ -625,8 +629,13 @@
     // Apply RELR relocations first so that the GOT is initialized for ifunc
     // resolvers.
     if (relr && relrsz) {
+      // Nothing has tagged the memtag globals here, so it is pointless either
+      // way to handle them, the tags will be zero anyway.
+      // That is moot though, because the linker does not use memtag_globals
+      // in the first place.
       relocate_relr(reinterpret_cast<ElfW(Relr*)>(ehdr + relr),
-                    reinterpret_cast<ElfW(Relr*)>(ehdr + relr + relrsz), ehdr);
+                    reinterpret_cast<ElfW(Relr*)>(ehdr + relr + relrsz), ehdr,
+                    /*has_memtag_globals=*/ false);
     }
     if (pltrel && pltrelsz) {
       call_ifunc_resolvers_for_section(reinterpret_cast<RelType*>(ehdr + pltrel),
@@ -646,6 +655,16 @@
   }
 }
 
+// Remapping MTE globals segments happens before the linker relocates itself, and so can't use
+// memcpy() from string.h. This function is compiled with -ffreestanding.
+void linker_memcpy(void* dst, const void* src, size_t n) {
+  char* dst_bytes = reinterpret_cast<char*>(dst);
+  const char* src_bytes = reinterpret_cast<const char*>(src);
+  for (size_t i = 0; i < n; ++i) {
+    dst_bytes[i] = src_bytes[i];
+  }
+}
+
 // Detect an attempt to run the linker on itself. e.g.:
 //   /system/bin/linker64 /system/bin/linker64
 // Use priority-1 to run this constructor before other constructors.
diff --git a/linker/linker_main.h b/linker/linker_main.h
index 724f43c..ffbcf0f 100644
--- a/linker/linker_main.h
+++ b/linker/linker_main.h
@@ -70,3 +70,5 @@
 soinfo* solist_get_head();
 soinfo* solist_get_somain();
 soinfo* solist_get_vdso();
+
+void linker_memcpy(void* dst, const void* src, size_t n);
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 7691031..2bdd7f8 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -37,9 +37,12 @@
 #include <unistd.h>
 
 #include "linker.h"
+#include "linker_debug.h"
 #include "linker_dlwarning.h"
 #include "linker_globals.h"
-#include "linker_debug.h"
+#include "linker_logger.h"
+#include "linker_main.h"
+#include "linker_soinfo.h"
 #include "linker_utils.h"
 
 #include "private/bionic_asm_note.h"
@@ -1172,6 +1175,125 @@
                                    should_use_16kib_app_compat);
 }
 
+static bool segment_needs_memtag_globals_remapping(const ElfW(Phdr) * phdr) {
+  // For now, MTE globals is only supported on writeable data segments.
+  return phdr->p_type == PT_LOAD && !(phdr->p_flags & PF_X) && (phdr->p_flags & PF_W);
+}
+
+/* When MTE globals are requested by the binary, and when the hardware supports
+ * it, remap the executable's PT_LOAD data pages to have PROT_MTE.
+ *
+ * Returns 0 on success, -1 on failure (error code in errno).
+ */
+int remap_memtag_globals_segments(const ElfW(Phdr) * phdr_table __unused,
+                                  size_t phdr_count __unused, ElfW(Addr) load_bias __unused) {
+#if defined(__aarch64__)
+  for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_table + phdr_count; phdr++) {
+    if (!segment_needs_memtag_globals_remapping(phdr)) {
+      continue;
+    }
+
+    uintptr_t seg_page_start = page_start(phdr->p_vaddr) + load_bias;
+    uintptr_t seg_page_end = page_end(phdr->p_vaddr + phdr->p_memsz) + load_bias;
+    size_t seg_page_aligned_size = seg_page_end - seg_page_start;
+
+    int prot = PFLAGS_TO_PROT(phdr->p_flags);
+    // For anonymous private mappings, it may be possible to simply mprotect()
+    // the PROT_MTE flag over the top. For file-based mappings, this will fail,
+    // and we'll need to fall back. We also allow PROT_WRITE here to allow
+    // writing memory tags (in `soinfo::tag_globals()`), and set these sections
+    // back to read-only after tags are applied (similar to RELRO).
+    prot |= PROT_MTE;
+    if (mprotect(reinterpret_cast<void*>(seg_page_start), seg_page_aligned_size,
+                 prot | PROT_WRITE) == 0) {
+      continue;
+    }
+
+    void* mapping_copy = mmap(nullptr, seg_page_aligned_size, PROT_READ | PROT_WRITE,
+                              MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    linker_memcpy(mapping_copy, reinterpret_cast<void*>(seg_page_start), seg_page_aligned_size);
+
+    void* seg_addr = mmap(reinterpret_cast<void*>(seg_page_start), seg_page_aligned_size,
+                          prot | PROT_WRITE, MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    if (seg_addr == MAP_FAILED) return -1;
+
+    linker_memcpy(seg_addr, mapping_copy, seg_page_aligned_size);
+    munmap(mapping_copy, seg_page_aligned_size);
+  }
+#endif  // defined(__aarch64__)
+  return 0;
+}
+
+void protect_memtag_globals_ro_segments(const ElfW(Phdr) * phdr_table __unused,
+                                        size_t phdr_count __unused, ElfW(Addr) load_bias __unused) {
+#if defined(__aarch64__)
+  for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_table + phdr_count; phdr++) {
+    int prot = PFLAGS_TO_PROT(phdr->p_flags);
+    if (!segment_needs_memtag_globals_remapping(phdr) || (prot & PROT_WRITE)) {
+      continue;
+    }
+
+    prot |= PROT_MTE;
+
+    uintptr_t seg_page_start = page_start(phdr->p_vaddr) + load_bias;
+    uintptr_t seg_page_end = page_end(phdr->p_vaddr + phdr->p_memsz) + load_bias;
+    size_t seg_page_aligned_size = seg_page_end - seg_page_start;
+    mprotect(reinterpret_cast<void*>(seg_page_start), seg_page_aligned_size, prot);
+  }
+#endif  // defined(__aarch64__)
+}
+
+void name_memtag_globals_segments(const ElfW(Phdr) * phdr_table, size_t phdr_count,
+                                  ElfW(Addr) load_bias, const char* soname,
+                                  std::list<std::string>& vma_names) {
+  for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_table + phdr_count; phdr++) {
+    if (!segment_needs_memtag_globals_remapping(phdr)) {
+      continue;
+    }
+
+    uintptr_t seg_page_start = page_start(phdr->p_vaddr) + load_bias;
+    uintptr_t seg_page_end = page_end(phdr->p_vaddr + phdr->p_memsz) + load_bias;
+    size_t seg_page_aligned_size = seg_page_end - seg_page_start;
+
+    // For file-based mappings that we're now forcing to be anonymous mappings, set the VMA name to
+    // make debugging easier.
+    // Once we are targeting only devices that run kernel 5.10 or newer (and thus include
+    // https://android-review.git.corp.google.com/c/kernel/common/+/1934723 which causes the
+    // VMA_ANON_NAME to be copied into the kernel), we can get rid of the storage here.
+    // For now, that is not the case:
+    // https://source.android.com/docs/core/architecture/kernel/android-common#compatibility-matrix
+    constexpr int kVmaNameLimit = 80;
+    std::string& vma_name = vma_names.emplace_back('\0', kVmaNameLimit);
+    int full_vma_length =
+        async_safe_format_buffer(vma_name.data(), kVmaNameLimit, "mt:%s+%" PRIxPTR, soname,
+                                 page_start(phdr->p_vaddr)) +
+        /* include the null terminator */ 1;
+    // There's an upper limit of 80 characters, including the null terminator, in the anonymous VMA
+    // name. If we run over that limit, we end up truncating the segment offset and parts of the
+    // DSO's name, starting on the right hand side of the basename. Because the basename is the most
+    // important thing, chop off the soname from the left hand side first.
+    //
+    // Example (with '#' as the null terminator):
+    //   - "mt:/data/nativetest64/bionic-unit-tests/bionic-loader-test-libs/libdlext_test.so+e000#"
+    //     is a `full_vma_length` == 86.
+    //
+    // We need to left-truncate (86 - 80) 6 characters from the soname, plus the
+    // `vma_truncation_prefix`, so 9 characters total.
+    if (full_vma_length > kVmaNameLimit) {
+      const char vma_truncation_prefix[] = "...";
+      int soname_truncated_bytes =
+          full_vma_length - kVmaNameLimit + sizeof(vma_truncation_prefix) - 1;
+      async_safe_format_buffer(vma_name.data(), kVmaNameLimit, "mt:%s%s+%" PRIxPTR,
+                               vma_truncation_prefix, soname + soname_truncated_bytes,
+                               page_start(phdr->p_vaddr));
+    }
+    if (prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, reinterpret_cast<void*>(seg_page_start),
+              seg_page_aligned_size, vma_name.data()) != 0) {
+      DL_WARN("Failed to re-name memtag global segment.");
+    }
+  }
+}
+
 /* Change the protection of all loaded segments in memory to writable.
  * This is useful before performing relocations. Once completed, you
  * will have to call phdr_table_protect_segments to restore the original
diff --git a/linker/linker_phdr.h b/linker/linker_phdr.h
index 2f159f3..353970c 100644
--- a/linker/linker_phdr.h
+++ b/linker/linker_phdr.h
@@ -39,6 +39,8 @@
 #include "linker_mapped_file_fragment.h"
 #include "linker_note_gnu_property.h"
 
+#include <list>
+
 #define MAYBE_MAP_FLAG(x, from, to)  (((x) & (from)) ? (to) : 0)
 #define PFLAGS_TO_PROT(x)            (MAYBE_MAP_FLAG((x), PF_X, PROT_EXEC) | \
                                       MAYBE_MAP_FLAG((x), PF_R, PROT_READ) | \
@@ -188,3 +190,13 @@
                                             ElfW(Addr) load_bias);
 
 bool page_size_migration_supported();
+
+int remap_memtag_globals_segments(const ElfW(Phdr) * phdr_table, size_t phdr_count,
+                                  ElfW(Addr) load_bias);
+
+void protect_memtag_globals_ro_segments(const ElfW(Phdr) * phdr_table, size_t phdr_count,
+                                        ElfW(Addr) load_bias);
+
+void name_memtag_globals_segments(const ElfW(Phdr) * phdr_table, size_t phdr_count,
+                                  ElfW(Addr) load_bias, const char* soname,
+                                  std::list<std::string>& vma_names);
diff --git a/linker/linker_relocate.cpp b/linker/linker_relocate.cpp
index 0470f87..bbf8359 100644
--- a/linker/linker_relocate.cpp
+++ b/linker/linker_relocate.cpp
@@ -44,6 +44,8 @@
 #include "linker_soinfo.h"
 #include "private/bionic_globals.h"
 
+#include <platform/bionic/mte.h>
+
 static bool is_tls_reloc(ElfW(Word) type) {
   switch (type) {
     case R_GENERIC_TLS_DTPMOD:
@@ -163,7 +165,8 @@
 static bool process_relocation_impl(Relocator& relocator, const rel_t& reloc) {
   constexpr bool IsGeneral = Mode == RelocMode::General;
 
-  void* const rel_target = reinterpret_cast<void*>(reloc.r_offset + relocator.si->load_bias);
+  void* const rel_target = reinterpret_cast<void*>(
+      relocator.si->apply_memtag_if_mte_globals(reloc.r_offset + relocator.si->load_bias));
   const uint32_t r_type = ELFW(R_TYPE)(reloc.r_info);
   const uint32_t r_sym = ELFW(R_SYM)(reloc.r_info);
 
@@ -316,6 +319,7 @@
     // common in non-platform binaries.
     if (r_type == R_GENERIC_ABSOLUTE) {
       count_relocation_if<IsGeneral>(kRelocAbsolute);
+      if (found_in) sym_addr = found_in->apply_memtag_if_mte_globals(sym_addr);
       const ElfW(Addr) result = sym_addr + get_addend_rel();
       LD_DEBUG(reloc && IsGeneral, "RELO ABSOLUTE %16p <- %16p %s",
                rel_target, reinterpret_cast<void*>(result), sym_name);
@@ -326,6 +330,7 @@
       // document (IHI0044F) specifies that R_ARM_GLOB_DAT has an addend, but Bionic isn't adding
       // it.
       count_relocation_if<IsGeneral>(kRelocAbsolute);
+      if (found_in) sym_addr = found_in->apply_memtag_if_mte_globals(sym_addr);
       const ElfW(Addr) result = sym_addr + get_addend_norel();
       LD_DEBUG(reloc && IsGeneral, "RELO GLOB_DAT %16p <- %16p %s",
                rel_target, reinterpret_cast<void*>(result), sym_name);
@@ -335,7 +340,18 @@
       // In practice, r_sym is always zero, but if it weren't, the linker would still look up the
       // referenced symbol (and abort if the symbol isn't found), even though it isn't used.
       count_relocation_if<IsGeneral>(kRelocRelative);
-      const ElfW(Addr) result = relocator.si->load_bias + get_addend_rel();
+      ElfW(Addr) result = relocator.si->load_bias + get_addend_rel();
+      // MTE globals reuses the place bits for additional tag-derivation metadata for
+      // R_AARCH64_RELATIVE relocations, which makes it incompatible with
+      // `-Wl,--apply-dynamic-relocs`. This is enforced by lld, however there's nothing stopping
+      // Android binaries (particularly prebuilts) from building with this linker flag if they're
+      // not built with MTE globals. Thus, don't use the new relocation semantics if this DSO
+      // doesn't have MTE globals.
+      if (relocator.si->should_tag_memtag_globals()) {
+        int64_t* place = static_cast<int64_t*>(rel_target);
+        int64_t offset = *place;
+        result = relocator.si->apply_memtag_if_mte_globals(result + offset) - offset;
+      }
       LD_DEBUG(reloc && IsGeneral, "RELO RELATIVE %16p <- %16p",
                rel_target, reinterpret_cast<void*>(result));
       *static_cast<ElfW(Addr)*>(rel_target) = result;
@@ -600,7 +616,7 @@
     LD_DEBUG(reloc, "[ relocating %s relr ]", get_realpath());
     const ElfW(Relr)* begin = relr_;
     const ElfW(Relr)* end = relr_ + relr_count_;
-    if (!relocate_relr(begin, end, load_bias)) {
+    if (!relocate_relr(begin, end, load_bias, should_tag_memtag_globals())) {
       return false;
     }
   }
diff --git a/linker/linker_sleb128.h b/linker/linker_sleb128.h
index 6bb3199..f48fda8 100644
--- a/linker/linker_sleb128.h
+++ b/linker/linker_sleb128.h
@@ -69,3 +69,32 @@
   const uint8_t* current_;
   const uint8_t* const end_;
 };
+
+class uleb128_decoder {
+ public:
+  uleb128_decoder(const uint8_t* buffer, size_t count) : current_(buffer), end_(buffer + count) {}
+
+  uint64_t pop_front() {
+    uint64_t value = 0;
+
+    size_t shift = 0;
+    uint8_t byte;
+
+    do {
+      if (current_ >= end_) {
+        async_safe_fatal("uleb128_decoder ran out of bounds");
+      }
+      byte = *current_++;
+      value |= (static_cast<size_t>(byte & 127) << shift);
+      shift += 7;
+    } while (byte & 128);
+
+    return value;
+  }
+
+  bool has_bytes() { return current_ < end_; }
+
+ private:
+  const uint8_t* current_;
+  const uint8_t* const end_;
+};
diff --git a/linker/linker_soinfo.cpp b/linker/linker_soinfo.cpp
index 0549d36..176c133 100644
--- a/linker/linker_soinfo.cpp
+++ b/linker/linker_soinfo.cpp
@@ -44,6 +44,8 @@
 #include "linker_logger.h"
 #include "linker_relocate.h"
 #include "linker_utils.h"
+#include "platform/bionic/mte.h"
+#include "private/bionic_globals.h"
 
 SymbolLookupList::SymbolLookupList(soinfo* si)
     : sole_lib_(si->get_lookup_lib()), begin_(&sole_lib_), end_(&sole_lib_ + 1) {
@@ -304,6 +306,12 @@
   return is_gnu_hash() ? gnu_lookup(symbol_name, vi) : elf_lookup(symbol_name, vi);
 }
 
+ElfW(Addr) soinfo::apply_memtag_if_mte_globals(ElfW(Addr) sym_addr) const {
+  if (!should_tag_memtag_globals()) return sym_addr;
+  if (sym_addr == 0) return sym_addr;  // Handle undefined weak symbols.
+  return reinterpret_cast<ElfW(Addr)>(get_tagged_address(reinterpret_cast<void*>(sym_addr)));
+}
+
 const ElfW(Sym)* soinfo::gnu_lookup(SymbolName& symbol_name, const version_info* vi) const {
   const uint32_t hash = symbol_name.gnu_hash();
 
diff --git a/linker/linker_soinfo.h b/linker/linker_soinfo.h
index a776c1f..64f8aea 100644
--- a/linker/linker_soinfo.h
+++ b/linker/linker_soinfo.h
@@ -30,6 +30,7 @@
 
 #include <link.h>
 
+#include <list>
 #include <memory>
 #include <string>
 #include <vector>
@@ -66,9 +67,10 @@
                                          // soinfo is executed and this flag is
                                          // unset.
 #define FLAG_PRELINKED        0x00000400 // prelink_image has successfully processed this soinfo
+#define FLAG_GLOBALS_TAGGED   0x00000800 // globals have been tagged by MTE.
 #define FLAG_NEW_SOINFO       0x40000000 // new soinfo format
 
-#define SOINFO_VERSION 6
+#define SOINFO_VERSION 7
 
 ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr);
 
@@ -252,11 +254,14 @@
   void call_constructors();
   void call_destructors();
   void call_pre_init_constructors();
-  bool prelink_image();
+  bool prelink_image(bool deterministic_memtag_globals = false);
   bool link_image(const SymbolLookupList& lookup_list, soinfo* local_group_root,
                   const android_dlextinfo* extinfo, size_t* relro_fd_offset);
   bool protect_relro();
 
+  void tag_globals(bool deterministic_memtag_globals);
+  ElfW(Addr) apply_memtag_if_mte_globals(ElfW(Addr) sym_addr) const;
+
   void add_child(soinfo* child);
   void remove_all_links();
 
@@ -368,6 +373,10 @@
    should_pad_segments_ = should_pad_segments;
   }
   bool should_pad_segments() const { return should_pad_segments_; }
+  bool should_tag_memtag_globals() const {
+    return !is_linker() && memtag_globals() && memtag_globalssz() > 0 && __libc_mte_enabled();
+  }
+  std::list<std::string>& vma_names() { return vma_names_; };
 
   void set_should_use_16kib_app_compat(bool should_use_16kib_app_compat) {
     should_use_16kib_app_compat_ = should_use_16kib_app_compat;
@@ -464,6 +473,8 @@
   // version >= 7
   memtag_dynamic_entries_t memtag_dynamic_entries_;
 
+  std::list<std::string> vma_names_;
+
   // Pad gaps between segments when memory mapping?
   bool should_pad_segments_ = false;
 
diff --git a/tests/Android.bp b/tests/Android.bp
index f5f3e31..ea03c08 100644
--- a/tests/Android.bp
+++ b/tests/Android.bp
@@ -429,6 +429,7 @@
         "math_test.cpp",
         "membarrier_test.cpp",
         "memtag_stack_test.cpp",
+        "memtag_globals_test.cpp",
         "mntent_test.cpp",
         "mte_test.cpp",
         "netdb_test.cpp",
@@ -896,6 +897,11 @@
         "preinit_syscall_test_helper",
         "thread_exit_cb_helper",
         "tls_properties_helper",
+        "memtag_globals_binary",
+        "memtag_globals_binary_static",
+        "mte_globals_relr_regression_test_b_314038442",
+        "mte_globals_relr_regression_test_b_314038442_mte",
+        "memtag_globals_dso",
     ],
     data_libs: [
         "libatest_simple_zip",
@@ -1286,6 +1292,11 @@
         "heap_tagging_static_disabled_helper",
         "heap_tagging_static_sync_helper",
         "heap_tagging_sync_helper",
+        "memtag_globals_binary",
+        "memtag_globals_binary_static",
+        "memtag_globals_dso",
+        "mte_globals_relr_regression_test_b_314038442",
+        "mte_globals_relr_regression_test_b_314038442_mte",
         "stack_tagging_helper",
         "stack_tagging_static_helper",
     ],
diff --git a/tests/dlext_test.cpp b/tests/dlext_test.cpp
index 570da2a..8b26cb0 100644
--- a/tests/dlext_test.cpp
+++ b/tests/dlext_test.cpp
@@ -21,6 +21,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
+#include <link.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
@@ -40,11 +41,13 @@
 #include <procinfo/process_map.h>
 #include <ziparchive/zip_archive.h>
 
+#include "bionic/mte.h"
+#include "bionic/page.h"
 #include "core_shared_libs.h"
-#include "gtest_globals.h"
-#include "utils.h"
 #include "dlext_private.h"
 #include "dlfcn_symlink_support.h"
+#include "gtest_globals.h"
+#include "utils.h"
 
 #define ASSERT_DL_NOTNULL(ptr) \
     ASSERT_TRUE((ptr) != nullptr) << "dlerror: " << dlerror()
@@ -1958,6 +1961,14 @@
   dlclose(ns_a_handle3);
 }
 
+static inline int MapPflagsToProtFlags(uint32_t flags) {
+  int prot_flags = 0;
+  if (PF_X & flags) prot_flags |= PROT_EXEC;
+  if (PF_W & flags) prot_flags |= PROT_WRITE;
+  if (PF_R & flags) prot_flags |= PROT_READ;
+  return prot_flags;
+}
+
 TEST(dlext, ns_anonymous) {
   static const char* root_lib = "libnstest_root.so";
   std::string shared_libs = g_core_shared_libs + ":" + g_public_lib;
@@ -1999,30 +2010,45 @@
   typedef const char* (*fn_t)();
   fn_t ns_get_dlopened_string_private = reinterpret_cast<fn_t>(ns_get_dlopened_string_addr);
 
-  std::vector<map_record> maps;
-  Maps::parse_maps(&maps);
-
+  Dl_info private_library_info;
+  ASSERT_NE(dladdr(reinterpret_cast<void*>(ns_get_dlopened_string_addr), &private_library_info), 0)
+      << dlerror();
+  std::vector<map_record> maps_to_copy;
+  bool has_executable_segment = false;
   uintptr_t addr_start = 0;
   uintptr_t addr_end = 0;
-  bool has_executable_segment = false;
-  std::vector<map_record> maps_to_copy;
+  std::tuple dl_iterate_arg = {&private_library_info, &maps_to_copy, &has_executable_segment,
+                               &addr_start, &addr_end};
+  ASSERT_EQ(
+      1, dl_iterate_phdr(
+             [](dl_phdr_info* info, size_t /*size*/, void* data) -> int {
+               auto [private_library_info, maps_to_copy, has_executable_segment, addr_start,
+                     addr_end] = *reinterpret_cast<decltype(dl_iterate_arg)*>(data);
+               if (info->dlpi_addr != reinterpret_cast<ElfW(Addr)>(private_library_info->dli_fbase))
+                 return 0;
 
-  for (const auto& rec : maps) {
-    if (rec.pathname == private_library_absolute_path) {
-      if (addr_start == 0) {
-        addr_start = rec.addr_start;
-      }
-      addr_end = rec.addr_end;
-      has_executable_segment = has_executable_segment || (rec.perms & PROT_EXEC) != 0;
-
-      maps_to_copy.push_back(rec);
-    }
-  }
+               for (size_t i = 0; i < info->dlpi_phnum; ++i) {
+                 const ElfW(Phdr)* phdr = info->dlpi_phdr + i;
+                 if (phdr->p_type != PT_LOAD) continue;
+                 *has_executable_segment |= phdr->p_flags & PF_X;
+                 uintptr_t mapping_start = page_start(info->dlpi_addr + phdr->p_vaddr);
+                 uintptr_t mapping_end = page_end(info->dlpi_addr + phdr->p_vaddr + phdr->p_memsz);
+                 if (*addr_start == 0 || mapping_start < *addr_start) *addr_start = mapping_start;
+                 if (*addr_end == 0 || mapping_end > *addr_end) *addr_end = mapping_end;
+                 maps_to_copy->push_back({
+                     .addr_start = mapping_start,
+                     .addr_end = mapping_end,
+                     .perms = MapPflagsToProtFlags(phdr->p_flags),
+                 });
+               }
+               return 1;
+             },
+             &dl_iterate_arg));
 
   // Some validity checks.
+  ASSERT_NE(maps_to_copy.size(), 0u);
   ASSERT_TRUE(addr_start > 0);
   ASSERT_TRUE(addr_end > 0);
-  ASSERT_TRUE(maps_to_copy.size() > 0);
   ASSERT_TRUE(ns_get_dlopened_string_addr > addr_start);
   ASSERT_TRUE(ns_get_dlopened_string_addr < addr_end);
 
@@ -2052,19 +2078,26 @@
   ASSERT_EQ(ret, 0) << "Failed to stat library";
   size_t file_size = file_stat.st_size;
 
-  for (const auto& rec : maps_to_copy) {
-    uintptr_t offset = rec.addr_start - addr_start;
-    size_t size = rec.addr_end - rec.addr_start;
-    void* addr = reinterpret_cast<void*>(reserved_addr + offset);
-    void* map = mmap(addr, size, PROT_READ | PROT_WRITE,
-                     MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
-    ASSERT_TRUE(map != MAP_FAILED);
-    // Attempting the below memcpy from a portion of the map that is off the end of
-    // the backing file will cause the kernel to throw a SIGBUS
-    size_t _size = ::android::procinfo::MappedFileSize(rec.addr_start, rec.addr_end,
-                                                       rec.offset, file_size);
-    memcpy(map, reinterpret_cast<void*>(rec.addr_start), _size);
-    mprotect(map, size, rec.perms);
+  {
+    // Disable MTE while copying the PROT_MTE-protected global variables from
+    // the existing mappings. We don't really care about turning on PROT_MTE for
+    // the new copy of the mappings, as this isn't the behaviour under test and
+    // tags will be ignored. This only applies for MTE-enabled devices.
+    ScopedDisableMTE disable_mte_for_copying_global_variables;
+    for (const auto& rec : maps_to_copy) {
+      uintptr_t offset = rec.addr_start - addr_start;
+      size_t size = rec.addr_end - rec.addr_start;
+      void* addr = reinterpret_cast<void*>(reserved_addr + offset);
+      void* map =
+          mmap(addr, size, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
+      ASSERT_TRUE(map != MAP_FAILED);
+      // Attempting the below memcpy from a portion of the map that is off the end of
+      // the backing file will cause the kernel to throw a SIGBUS
+      size_t _size =
+          ::android::procinfo::MappedFileSize(rec.addr_start, rec.addr_end, rec.offset, file_size);
+      memcpy(map, reinterpret_cast<void*>(rec.addr_start), _size);
+      mprotect(map, size, rec.perms);
+    }
   }
 
   // call the function copy
diff --git a/tests/libs/Android.bp b/tests/libs/Android.bp
index d13ee60..5b86e78 100644
--- a/tests/libs/Android.bp
+++ b/tests/libs/Android.bp
@@ -1903,3 +1903,89 @@
         " $(location soong_zip) -o $(out).unaligned -L 0 -C $(genDir)/zipdir -D $(genDir)/zipdir &&" +
         " $(location bionic_tests_zipalign) 16384 $(out).unaligned $(out)",
 }
+
+cc_defaults {
+    name: "memtag_globals_defaults",
+    defaults: [
+        "bionic_testlib_defaults",
+        "bionic_targets_only"
+    ],
+    cflags: [
+        "-Wno-array-bounds",
+        "-Wno-unused-variable",
+    ],
+    header_libs: ["bionic_libc_platform_headers"],
+    sanitize: {
+        hwaddress: false,
+        memtag_heap: true,
+        memtag_globals: true,
+        diag: {
+            memtag_heap: true,
+        }
+    },
+}
+
+cc_test_library {
+    name: "memtag_globals_dso",
+    defaults: [ "memtag_globals_defaults" ],
+    srcs: ["memtag_globals_dso.cpp"],
+}
+
+cc_test {
+    name: "memtag_globals_binary",
+    defaults: [ "memtag_globals_defaults" ],
+    srcs: ["memtag_globals_binary.cpp"],
+    shared_libs: [ "memtag_globals_dso" ],
+    // This binary is used in the bionic-unit-tests as a data dependency, and is
+    // in the same folder as memtag_globals_dso. But, the default cc_test rules
+    // make this binary (when just explicitly built and shoved in
+    // /data/nativetest64/) end up in a subfolder called
+    // 'memtag_globals_binary'. When this happens, the explicit build fails to
+    // find the DSO because the default rpath is just ${ORIGIN}, and because we
+    // want this to be usable both from bionic-unit-tests and explicit builds,
+    // let's just not put it in a subdirectory.
+    no_named_install_directory: true,
+}
+
+cc_test {
+    name: "memtag_globals_binary_static",
+    defaults: [ "memtag_globals_defaults" ],
+    srcs: ["memtag_globals_binary.cpp"],
+    static_libs: [ "memtag_globals_dso" ],
+    no_named_install_directory: true,
+    static_executable: true,
+}
+
+// This is a regression test for b/314038442, where binaries built *without* MTE
+// globals would have out-of-bounds RELR relocations, which where then `ldg`'d,
+// which resulted in linker crashes.
+cc_test {
+  name: "mte_globals_relr_regression_test_b_314038442",
+  defaults: [
+        "bionic_testlib_defaults",
+        "bionic_targets_only"
+    ],
+    cflags: [ "-Wno-array-bounds" ],
+    ldflags: [ "-Wl,--pack-dyn-relocs=relr" ],
+    srcs: ["mte_globals_relr_regression_test_b_314038442.cpp"],
+    no_named_install_directory: true,
+    sanitize: {
+        memtag_globals: false,
+    },
+}
+
+// Same test as above, but also for MTE globals, just for the sake of it.
+cc_test {
+  name: "mte_globals_relr_regression_test_b_314038442_mte",
+  defaults: [
+        "bionic_testlib_defaults",
+        "bionic_targets_only"
+    ],
+    cflags: [ "-Wno-array-bounds" ],
+    ldflags: [ "-Wl,--pack-dyn-relocs=relr" ],
+    srcs: ["mte_globals_relr_regression_test_b_314038442.cpp"],
+    no_named_install_directory: true,
+    sanitize: {
+      memtag_globals: true,
+    },
+}
diff --git a/tests/libs/memtag_globals.h b/tests/libs/memtag_globals.h
new file mode 100644
index 0000000..a03abae
--- /dev/null
+++ b/tests/libs/memtag_globals.h
@@ -0,0 +1,43 @@
+/*
+ * 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 <utility>
+#include <vector>
+
+void check_tagged(const void* a);
+void check_untagged(const void* a);
+void check_matching_tags(const void* a, const void* b);
+void check_eq(const void* a, const void* b);
+
+void dso_check_assertions(bool enforce_tagged);
+void dso_print_variables();
+
+void print_variable_address(const char* name, const void* ptr);
+void print_variables(const char* header,
+                     const std::vector<std::pair<const char*, const void*>>& tagged_variables,
+                     const std::vector<std::pair<const char*, const void*>>& untagged_variables);
diff --git a/tests/libs/memtag_globals_binary.cpp b/tests/libs/memtag_globals_binary.cpp
new file mode 100644
index 0000000..9248728
--- /dev/null
+++ b/tests/libs/memtag_globals_binary.cpp
@@ -0,0 +1,195 @@
+/*
+ * 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 <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <string>
+#include <vector>
+
+#include "memtag_globals.h"
+
+// Adapted from the LLD test suite: lld/test/ELF/Inputs/aarch64-memtag-globals.s
+
+/// Global variables defined here, of various semantics.
+char global[30] = {};
+__attribute__((no_sanitize("memtag"))) int global_untagged = 0;
+const int const_global = 0;
+static const int hidden_const_global = 0;
+static char hidden_global[12] = {};
+__attribute__((visibility("hidden"))) int hidden_attr_global = 0;
+__attribute__((visibility("hidden"))) const int hidden_attr_const_global = 0;
+
+/// Should be untagged.
+__thread int tls_global;
+__thread static int hidden_tls_global;
+
+/// Tagged, from the other file.
+extern int global_extern;
+/// Untagged, from the other file.
+extern __attribute__((no_sanitize("memtag"))) int global_extern_untagged;
+/// Tagged here, but untagged in the definition found in the sister objfile
+/// (explicitly).
+extern int global_extern_untagged_definition_but_tagged_import;
+
+/// ABS64 relocations. Also, forces symtab entries for local and external
+/// globals.
+char* pointer_to_global = &global[0];
+char* pointer_inside_global = &global[17];
+char* pointer_to_global_end = &global[30];
+char* pointer_past_global_end = &global[48];
+int* pointer_to_global_untagged = &global_untagged;
+const int* pointer_to_const_global = &const_global;
+/// RELATIVE relocations.
+const int* pointer_to_hidden_const_global = &hidden_const_global;
+char* pointer_to_hidden_global = &hidden_global[0];
+int* pointer_to_hidden_attr_global = &hidden_attr_global;
+const int* pointer_to_hidden_attr_const_global = &hidden_attr_const_global;
+/// RELATIVE relocations with special AArch64 MemtagABI semantics, with the
+/// offset ('12' or '16') encoded in the place.
+char* pointer_to_hidden_global_end = &hidden_global[12];
+char* pointer_past_hidden_global_end = &hidden_global[16];
+/// ABS64 relocations.
+int* pointer_to_global_extern = &global_extern;
+int* pointer_to_global_extern_untagged = &global_extern_untagged;
+int* pointer_to_global_extern_untagged_definition_but_tagged_import =
+    &global_extern_untagged_definition_but_tagged_import;
+
+// Force materialization of these globals into the symtab.
+int* get_address_to_tls_global() {
+  return &tls_global;
+}
+int* get_address_to_hidden_tls_global() {
+  return &hidden_tls_global;
+}
+
+static const std::vector<std::pair<const char*, const void*>>& get_expected_tagged_vars() {
+  static std::vector<std::pair<const char*, const void*>> expected_tagged_vars = {
+      {"global", &global},
+      {"pointer_inside_global", pointer_inside_global},
+      {"pointer_to_global_end", pointer_to_global_end},
+      {"pointer_past_global_end", pointer_past_global_end},
+      {"hidden_global", &hidden_global},
+      {"hidden_attr_global", &hidden_attr_global},
+      {"global_extern", &global_extern},
+  };
+  return expected_tagged_vars;
+}
+
+static const std::vector<std::pair<const char*, const void*>>& get_expected_untagged_vars() {
+  static std::vector<std::pair<const char*, const void*>> expected_untagged_vars = {
+      {"global_extern_untagged", &global_extern_untagged},
+      {"global_extern_untagged_definition_but_tagged_import",
+       &global_extern_untagged_definition_but_tagged_import},
+      {"global_untagged", &global_untagged},
+      {"const_global", &const_global},
+      {"hidden_const_global", &hidden_const_global},
+      {"hidden_attr_const_global", &hidden_attr_const_global},
+      {"tls_global", &tls_global},
+      {"hidden_tls_global", &hidden_tls_global},
+  };
+  return expected_untagged_vars;
+}
+
+void exe_print_variables() {
+  print_variables("  Variables accessible from the binary:\n", get_expected_tagged_vars(),
+                  get_expected_untagged_vars());
+}
+
+// Dump the addresses of the global variables to stderr
+void dso_print();
+void dso_print_others();
+
+void exe_check_assertions(bool check_pointers_are_tagged) {
+  // Check that non-const variables are writeable.
+  *pointer_to_global = 0;
+  *pointer_inside_global = 0;
+  *(pointer_to_global_end - 1) = 0;
+  *pointer_to_global_untagged = 0;
+  *pointer_to_hidden_global = 0;
+  *pointer_to_hidden_attr_global = 0;
+  *(pointer_to_hidden_global_end - 1) = 0;
+  *pointer_to_global_extern = 0;
+  *pointer_to_global_extern_untagged = 0;
+  *pointer_to_global_extern_untagged_definition_but_tagged_import = 0;
+
+  if (check_pointers_are_tagged) {
+    for (const auto& [_, pointer] : get_expected_tagged_vars()) {
+      check_tagged(pointer);
+    }
+  }
+
+  for (const auto& [_, pointer] : get_expected_untagged_vars()) {
+    check_untagged(pointer);
+  }
+
+  check_matching_tags(pointer_to_global, pointer_inside_global);
+  check_matching_tags(pointer_to_global, pointer_to_global_end);
+  check_matching_tags(pointer_to_global, pointer_past_global_end);
+  check_eq(pointer_inside_global, pointer_to_global + 17);
+  check_eq(pointer_to_global_end, pointer_to_global + 30);
+  check_eq(pointer_past_global_end, pointer_to_global + 48);
+
+  check_matching_tags(pointer_to_hidden_global, pointer_to_hidden_global_end);
+  check_matching_tags(pointer_to_hidden_global, pointer_past_hidden_global_end);
+  check_eq(pointer_to_hidden_global_end, pointer_to_hidden_global + 12);
+  check_eq(pointer_past_hidden_global_end, pointer_to_hidden_global + 16);
+}
+
+void crash() {
+  *pointer_past_global_end = 0;
+}
+
+int main(int argc, char** argv) {
+  bool check_pointers_are_tagged = false;
+  // For an MTE-capable device, provide argv[1] == '1' to enable the assertions
+  // that pointers should be tagged.
+  if (argc >= 2 && argv[1][0] == '1') {
+    check_pointers_are_tagged = true;
+  }
+
+  char* heap_ptr = static_cast<char*>(malloc(1));
+  print_variable_address("heap address", heap_ptr);
+  *heap_ptr = 0;
+  if (check_pointers_are_tagged) check_tagged(heap_ptr);
+  free(heap_ptr);
+
+  exe_print_variables();
+  dso_print_variables();
+
+  exe_check_assertions(check_pointers_are_tagged);
+  dso_check_assertions(check_pointers_are_tagged);
+
+  printf("Assertions were passed. Now doing a global-buffer-overflow.\n");
+  fflush(stdout);
+  crash();
+  printf("global-buffer-overflow went uncaught.\n");
+  return 0;
+}
diff --git a/tests/libs/memtag_globals_dso.cpp b/tests/libs/memtag_globals_dso.cpp
new file mode 100644
index 0000000..9ed264e
--- /dev/null
+++ b/tests/libs/memtag_globals_dso.cpp
@@ -0,0 +1,165 @@
+/*
+ * 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 <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <vector>
+
+#include "memtag_globals.h"
+
+// Adapted from the LLD test suite: lld/test/ELF/Inputs/aarch64-memtag-globals.s
+
+int global_extern;
+static int global_extern_hidden;
+__attribute__((no_sanitize("memtag"))) int global_extern_untagged;
+__attribute__((no_sanitize("memtag"))) int global_extern_untagged_definition_but_tagged_import;
+
+void assertion_failure() {
+  exit(1);
+}
+
+void check_tagged(const void* a) {
+  uintptr_t a_uptr = reinterpret_cast<uintptr_t>(a);
+#if defined(__aarch64__)
+  if ((a_uptr >> 56) == 0) {
+    fprintf(stderr, "**********************************\n");
+    fprintf(stderr, "Failed assertion:\n");
+    fprintf(stderr, "  tag(0x%zx) != 0\n", a_uptr);
+    fprintf(stderr, "**********************************\n");
+
+    assertion_failure();
+  }
+#endif  // defined(__aarch64__)
+}
+
+void check_untagged(const void* a) {
+  uintptr_t a_uptr = reinterpret_cast<uintptr_t>(a);
+#if defined(__aarch64__)
+  if ((a_uptr >> 56) != 0) {
+    fprintf(stderr, "**********************************\n");
+    fprintf(stderr, "Failed assertion:\n");
+    fprintf(stderr, "  tag(0x%zx) == 0\n", a_uptr);
+    fprintf(stderr, "**********************************\n");
+
+    assertion_failure();
+  }
+#endif  // defined(__aarch64__)
+}
+
+void check_matching_tags(const void* a, const void* b) {
+  uintptr_t a_uptr = reinterpret_cast<uintptr_t>(a);
+  uintptr_t b_uptr = reinterpret_cast<uintptr_t>(b);
+#if defined(__aarch64__)
+  if (a_uptr >> 56 != b_uptr >> 56) {
+    fprintf(stderr, "**********************************\n");
+    fprintf(stderr, "Failed assertion:\n");
+    fprintf(stderr, "  tag(0x%zx) != tag(0x%zx)\n", a_uptr, b_uptr);
+    fprintf(stderr, "**********************************\n");
+
+    assertion_failure();
+  }
+#endif  // defined(__aarch64__)
+}
+
+void check_eq(const void* a, const void* b) {
+  if (a != b) {
+    fprintf(stderr, "**********************************\n");
+    fprintf(stderr, "Failed assertion:\n");
+    fprintf(stderr, "  %p != %p\n", a, b);
+    fprintf(stderr, "**********************************\n");
+
+    assertion_failure();
+  }
+}
+
+#define LONGEST_VARIABLE_NAME "51"
+void print_variable_address(const char* name, const void* ptr) {
+  printf("%" LONGEST_VARIABLE_NAME "s: %16p\n", name, ptr);
+}
+
+static const std::vector<std::pair<const char*, const void*>>& get_expected_tagged_vars() {
+  static std::vector<std::pair<const char*, const void*>> expected_tagged_vars = {
+      {"global_extern", &global_extern},
+      {"global_extern_hidden", &global_extern_hidden},
+  };
+  return expected_tagged_vars;
+}
+
+static const std::vector<std::pair<const char*, const void*>>& get_expected_untagged_vars() {
+  static std::vector<std::pair<const char*, const void*>> expected_untagged_vars = {
+      {"global_extern_untagged", &global_extern_untagged},
+      {"global_extern_untagged_definition_but_tagged_import",
+       &global_extern_untagged_definition_but_tagged_import},
+  };
+  return expected_untagged_vars;
+}
+
+void dso_print_variables() {
+  print_variables("  Variables declared in the DSO:\n", get_expected_tagged_vars(),
+                  get_expected_untagged_vars());
+}
+
+void print_variables(const char* header,
+                     const std::vector<std::pair<const char*, const void*>>& tagged_variables,
+                     const std::vector<std::pair<const char*, const void*>>& untagged_variables) {
+  printf("==========================================================\n");
+  printf("%s", header);
+  printf("==========================================================\n");
+  printf(" Variables expected to be tagged:\n");
+  printf("----------------------------------------------------------\n");
+  for (const auto& [name, pointer] : tagged_variables) {
+    print_variable_address(name, pointer);
+  }
+
+  printf("\n----------------------------------------------------------\n");
+  printf(" Variables expected to be untagged:\n");
+  printf("----------------------------------------------------------\n");
+  for (const auto& [name, pointer] : untagged_variables) {
+    print_variable_address(name, pointer);
+  }
+  printf("\n");
+}
+
+void dso_check_assertions(bool check_pointers_are_tagged) {
+  // Check that non-const variables are writeable.
+  global_extern = 0;
+  global_extern_hidden = 0;
+  global_extern_untagged = 0;
+  global_extern_untagged_definition_but_tagged_import = 0;
+
+  if (check_pointers_are_tagged) {
+    for (const auto& [_, pointer] : get_expected_tagged_vars()) {
+      check_tagged(pointer);
+    }
+  }
+
+  for (const auto& [_, pointer] : get_expected_untagged_vars()) {
+    check_untagged(pointer);
+  }
+}
diff --git a/tests/libs/mte_globals_relr_regression_test_b_314038442.cpp b/tests/libs/mte_globals_relr_regression_test_b_314038442.cpp
new file mode 100644
index 0000000..20bbba9
--- /dev/null
+++ b/tests/libs/mte_globals_relr_regression_test_b_314038442.cpp
@@ -0,0 +1,55 @@
+/*
+ * 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 <stdint.h>
+#include <stdio.h>
+
+static volatile char array[0x10000];
+volatile char* volatile oob_ptr = &array[0x111111111];
+
+unsigned char get_tag(__attribute__((unused)) volatile void* ptr) {
+#if defined(__aarch64__)
+  return static_cast<unsigned char>(reinterpret_cast<uintptr_t>(ptr) >> 56) & 0xf;
+#else   // !defined(__aarch64__)
+  return 0;
+#endif  // defined(__aarch64__)
+}
+
+int main() {
+  printf("Program loaded successfully. %p %p. ", array, oob_ptr);
+  if (get_tag(array) != get_tag(oob_ptr)) {
+    printf("Tags are mismatched!\n");
+    return 1;
+  }
+  if (get_tag(array) == 0) {
+    printf("Tags are zero!\n");
+  } else {
+    printf("Tags are non-zero\n");
+  }
+  return 0;
+}
diff --git a/tests/memtag_globals_test.cpp b/tests/memtag_globals_test.cpp
new file mode 100644
index 0000000..ff93e7b
--- /dev/null
+++ b/tests/memtag_globals_test.cpp
@@ -0,0 +1,113 @@
+/*
+ * 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 <gtest/gtest.h>
+
+#if defined(__BIONIC__)
+#include "gtest_globals.h"
+#include "utils.h"
+#endif  // defined(__BIONIC__)
+
+#include <android-base/test_utils.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <string>
+#include <tuple>
+
+#include "platform/bionic/mte.h"
+
+class MemtagGlobalsTest : public testing::TestWithParam<bool> {};
+
+TEST_P(MemtagGlobalsTest, test) {
+  SKIP_WITH_HWASAN << "MTE globals tests are incompatible with HWASan";
+#if defined(__BIONIC__) && defined(__aarch64__)
+  std::string binary = GetTestLibRoot() + "/memtag_globals_binary";
+  bool is_static = MemtagGlobalsTest::GetParam();
+  if (is_static) {
+    binary += "_static";
+  }
+
+  chmod(binary.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({binary.c_str(), nullptr});
+  eth.Run(
+      [&]() {
+        execve(binary.c_str(), eth.GetArgs(), eth.GetEnv());
+        GTEST_FAIL() << "Failed to execve: " << strerror(errno) << " " << binary.c_str();
+      },
+      // We catch the global-buffer-overflow and crash only when MTE globals is
+      // supported. Note that MTE globals is unsupported for fully static
+      // executables, but we should still make sure the binary passes its
+      // assertions, just that global variables won't be tagged.
+      (mte_supported() && !is_static) ? -SIGSEGV : 0, "Assertions were passed");
+#else
+  GTEST_SKIP() << "bionic/arm64 only";
+#endif
+}
+
+INSTANTIATE_TEST_SUITE_P(MemtagGlobalsTest, MemtagGlobalsTest, testing::Bool(),
+                         [](const ::testing::TestParamInfo<MemtagGlobalsTest::ParamType>& info) {
+                           if (info.param) return "MemtagGlobalsTest_static";
+                           return "MemtagGlobalsTest";
+                         });
+
+TEST(MemtagGlobalsTest, RelrRegressionTestForb314038442) {
+  SKIP_WITH_HWASAN << "MTE globals tests are incompatible with HWASan";
+#if defined(__BIONIC__) && defined(__aarch64__)
+  std::string binary = GetTestLibRoot() + "/mte_globals_relr_regression_test_b_314038442";
+  chmod(binary.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({binary.c_str(), nullptr});
+  eth.Run(
+      [&]() {
+        execve(binary.c_str(), eth.GetArgs(), eth.GetEnv());
+        GTEST_FAIL() << "Failed to execve: " << strerror(errno) << " " << binary.c_str();
+      },
+      /* exit code */ 0, "Program loaded successfully.*Tags are zero!");
+#else
+  GTEST_SKIP() << "bionic/arm64 only";
+#endif
+}
+
+TEST(MemtagGlobalsTest, RelrRegressionTestForb314038442WithMteGlobals) {
+  if (!mte_supported()) GTEST_SKIP() << "Must have MTE support.";
+#if defined(__BIONIC__) && defined(__aarch64__)
+  std::string binary = GetTestLibRoot() + "/mte_globals_relr_regression_test_b_314038442_mte";
+  chmod(binary.c_str(), 0755);
+  ExecTestHelper eth;
+  eth.SetArgs({binary.c_str(), nullptr});
+  eth.Run(
+      [&]() {
+        execve(binary.c_str(), eth.GetArgs(), eth.GetEnv());
+        GTEST_FAIL() << "Failed to execve: " << strerror(errno) << " " << binary.c_str();
+      },
+      /* exit code */ 0, "Program loaded successfully.*Tags are non-zero");
+#else
+  GTEST_SKIP() << "bionic/arm64 only";
+#endif
+}