diff --git a/docs/status.md b/docs/status.md
index 2919471..bc8ab6a 100644
--- a/docs/status.md
+++ b/docs/status.md
@@ -397,22 +397,25 @@
 overrun is detected, the program is safely aborted as in this
 [example](https://source.android.com/devices/tech/debug/native-crash#fortify).
 
-Note that in recent releases Android's FORTIFY has been extended to
-cover other issues. It can now detect, for example, passing `O_CREAT`
-to open(2) without specifying a mode. It also performs some checking
-regardless of whether the caller was built with FORTIFY enabled. In P,
-for example, calling a `pthread_mutex_` function on a destroyed mutex,
-calling a `<dirent.h>` function on a null pointer, using `%n` with the
-printf(3) family, or using the scanf(3) `m` modifier incorrectly will
-all result in FORTIFY failures even for code not built with FORTIFY.
+Note that Android's FORTIFY has been extended to cover other issues. It can
+detect, for example, passing `O_CREAT` to open(2) without specifying a mode. It
+also performs some checking regardless of whether the caller was built with
+FORTIFY enabled. From API level 28, for example, calling a `pthread_mutex_`
+function on a destroyed mutex, calling a `<dirent.h>` function on a null
+pointer, using `%n` with the printf(3) family, or using the scanf(3) `m`
+modifier incorrectly will all result in FORTIFY failures even for code not built
+with FORTIFY.
 
 More background information is available in our
 [FORTIFY in Android](https://android-developers.googleblog.com/2017/04/fortify-in-android.html)
-blog post.
+blog post, and there's more detail about the implementation in
+[The Anatomy of Clang FORTIFY](clang_fortify_anatomy.md).
 
-The Android platform is built with `-D_FORTIFY_SOURCE=2`, but NDK users
-need to manually enable FORTIFY by setting that themselves in whatever
-build system they're using. The exact subset of FORTIFY available to
+The Android platform is built with `-D_FORTIFY_SOURCE=2`. Users of ndk-build
+or the NDK's CMake toolchain file also get this by default with NDK r21 or
+newer. Users of other build systems
+need to manually enable FORTIFY by setting `_FORTIFY_SOURCE` themselves in
+whatever build system they're using. The exact subset of FORTIFY available to
 NDK users will depend on their target ABI level, because when a FORTIFY
 check can't be guaranteed at compile-time, a call to a run-time `_chk`
 function is added.
diff --git a/libc/include/android/versioning.h b/libc/include/android/versioning.h
index cd61f33..64528e1 100644
--- a/libc/include/android/versioning.h
+++ b/libc/include/android/versioning.h
@@ -22,8 +22,8 @@
 
 #define __INTRODUCED_IN(api_level) __attribute__((__annotate__("introduced_in=" #api_level)))
 #define __INTRODUCED_IN_NO_GUARD_FOR_NDK(api_level) __attribute__((__annotate__("introduced_in=" #api_level))) __VERSIONER_NO_GUARD
-#define __DEPRECATED_IN(api_level) __attribute__((__annotate__("deprecated_in=" #api_level)))
-#define __REMOVED_IN(api_level) __attribute__((__annotate__("obsoleted_in=" #api_level)))
+#define __DEPRECATED_IN(api_level, ...) __attribute__((__annotate__("deprecated_in=" #api_level)))
+#define __REMOVED_IN(api_level, ...) __attribute__((__annotate__("obsoleted_in=" #api_level)))
 #define __INTRODUCED_IN_32(api_level) __attribute__((__annotate__("introduced_in_32=" #api_level)))
 #define __INTRODUCED_IN_64(api_level) __attribute__((__annotate__("introduced_in_64=" #api_level)))
 
@@ -47,16 +47,16 @@
 // libc++ doesn't currently guard these calls. There's no risk to the apps though because using
 // those APIs will still cause a link error.
 #if defined(__ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__)
-#define __BIONIC_AVAILABILITY(__what) __attribute__((__availability__(android,__what)))
+#define __BIONIC_AVAILABILITY(__what, ...) __attribute__((__availability__(android,__what __VA_OPT__(,) __VA_ARGS__)))
 #define __INTRODUCED_IN_NO_GUARD_FOR_NDK(api_level) __INTRODUCED_IN(api_level)
 #else
-#define __BIONIC_AVAILABILITY(__what) __attribute__((__availability__(android,strict,__what)))
+#define __BIONIC_AVAILABILITY(__what, ...) __attribute__((__availability__(android,strict,__what __VA_OPT__(,) __VA_ARGS__)))
 #define __INTRODUCED_IN_NO_GUARD_FOR_NDK(api_level)
 #endif
 
 #define __INTRODUCED_IN(api_level) __BIONIC_AVAILABILITY(introduced=api_level)
-#define __DEPRECATED_IN(api_level) __BIONIC_AVAILABILITY(deprecated=api_level)
-#define __REMOVED_IN(api_level) __BIONIC_AVAILABILITY(obsoleted=api_level)
+#define __DEPRECATED_IN(api_level, ...) __BIONIC_AVAILABILITY(deprecated=api_level __VA_OPT__(,message=) __VA_ARGS__)
+#define __REMOVED_IN(api_level, ...) __BIONIC_AVAILABILITY(obsoleted=api_level __VA_OPT__(,message=) __VA_ARGS__)
 
 // The same availability attribute can't be annotated multiple times. Therefore, the macros are
 // defined for the configuration that it is valid for so that declarations like the below doesn't
@@ -80,5 +80,5 @@
 // Vendor modules do not follow SDK versioning. Ignore NDK guards for vendor modules.
 #if defined(__ANDROID_VENDOR__)
 #undef __BIONIC_AVAILABILITY
-#define __BIONIC_AVAILABILITY(x)
+#define __BIONIC_AVAILABILITY(api_level, ...)
 #endif // defined(__ANDROID_VENDOR__)
diff --git a/libc/include/stdio.h b/libc/include/stdio.h
index 32264d6..78114c3 100644
--- a/libc/include/stdio.h
+++ b/libc/include/stdio.h
@@ -69,7 +69,7 @@
 #define stderr stderr
 #else
 /* Before M the actual symbols for stdin and friends had different names. */
-extern FILE __sF[] __REMOVED_IN(23);
+extern FILE __sF[] __REMOVED_IN(23, "Use stdin/stdout/stderr");
 
 #define stdin (&__sF[0])
 #define stdout (&__sF[1])
diff --git a/libc/system_properties/system_properties.cpp b/libc/system_properties/system_properties.cpp
index 1dedb61..e0d38a8 100644
--- a/libc/system_properties/system_properties.cpp
+++ b/libc/system_properties/system_properties.cpp
@@ -337,31 +337,42 @@
 
 int SystemProperties::Add(const char* name, unsigned int namelen, const char* value,
                           unsigned int valuelen) {
-  if (valuelen >= PROP_VALUE_MAX && !is_read_only(name)) {
+  if (namelen < 1) {
+    async_safe_format_log(ANDROID_LOG_ERROR, "libc",
+                          "__system_property_add failed: name length 0");
     return -1;
   }
 
-  if (namelen < 1) {
+  if (valuelen >= PROP_VALUE_MAX && !is_read_only(name)) {
+    async_safe_format_log(ANDROID_LOG_ERROR, "libc",
+                          "__system_property_add failed: \"%s\" value too long: %d >= PROP_VALUE_MAX",
+                          name, valuelen);
     return -1;
   }
 
   if (!initialized_) {
+    async_safe_format_log(ANDROID_LOG_ERROR, "libc",
+                          "__system_property_add failed: properties not initialized");
     return -1;
   }
 
   prop_area* serial_pa = contexts_->GetSerialPropArea();
   if (serial_pa == nullptr) {
+    async_safe_format_log(ANDROID_LOG_ERROR, "libc",
+                          "__system_property_add failed: property area not found");
     return -1;
   }
 
   prop_area* pa = contexts_->GetPropAreaForName(name);
   if (!pa) {
-    async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Access denied adding property \"%s\"", name);
+    async_safe_format_log(ANDROID_LOG_ERROR, "libc",
+                          "__system_property_add failed: access denied for \"%s\"", name);
     return -1;
   }
 
-  bool ret = pa->add(name, namelen, value, valuelen);
-  if (!ret) {
+  if (!pa->add(name, namelen, value, valuelen)) {
+    async_safe_format_log(ANDROID_LOG_ERROR, "libc",
+                          "__system_property_add failed: add failed for \"%s\"", name);
     return -1;
   }
 
diff --git a/linker/linker_crt_pad_segment_test.cpp b/linker/linker_crt_pad_segment_test.cpp
index 5a219f8..c11df50 100644
--- a/linker/linker_crt_pad_segment_test.cpp
+++ b/linker/linker_crt_pad_segment_test.cpp
@@ -72,13 +72,22 @@
 };  // anonymous namespace
 
 TEST(crt_pad_segment, note_absent) {
+  if (!page_size_migration_supported()) {
+    GTEST_SKIP() << "Kernel does not support page size migration";
+  }
   ASSERT_FALSE(GetPadSegment("no_crt_pad_segment.so"));
 }
 
 TEST(crt_pad_segment, note_present_and_enabled) {
+  if (!page_size_migration_supported()) {
+    GTEST_SKIP() << "Kernel does not support page size migration";
+  }
   ASSERT_TRUE(GetPadSegment("crt_pad_segment_enabled.so"));
 }
 
 TEST(crt_pad_segment, note_present_and_disabled) {
+  if (!page_size_migration_supported()) {
+    GTEST_SKIP() << "Kernel does not support page size migration";
+  }
   ASSERT_FALSE(GetPadSegment("crt_pad_segment_disabled.so"));
 }
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index ef7671c..fa712a1 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -46,6 +46,8 @@
 #include "private/CFIShadow.h" // For kLibraryAlignment
 #include "private/elf_note.h"
 
+#include <android-base/file.h>
+
 static int GetTargetElfMachine() {
 #if defined(__arm__)
   return EM_ARM;
@@ -707,8 +709,28 @@
   return true;
 }
 
+/*
+ * Returns true if the kernel supports page size migration, else false.
+ */
+bool page_size_migration_supported() {
+  static bool pgsize_migration_enabled = []() {
+    std::string enabled;
+    if (!android::base::ReadFileToString("/sys/kernel/mm/pgsize_migration/enabled", &enabled)) {
+      return false;
+    }
+    return enabled.find("1") != std::string::npos;
+  }();
+  return pgsize_migration_enabled;
+}
+
 // Find the ELF note of type NT_ANDROID_TYPE_PAD_SEGMENT and check that the desc value is 1.
 bool ElfReader::ReadPadSegmentNote() {
+  if (!page_size_migration_supported()) {
+    // Don't attempt to read the note, since segment extension isn't
+    // supported; but return true so that loading can continue normally.
+    return true;
+  }
+
   // The ELF can have multiple PT_NOTE's, check them all
   for (size_t i = 0; i < phdr_num_; ++i) {
     const ElfW(Phdr)* phdr = &phdr_table_[i];
@@ -773,7 +795,16 @@
   const ElfW(Phdr)* next = nullptr;
   size_t next_idx = phdr_idx + 1;
 
-  if (phdr->p_align == kPageSize || !should_pad_segments) {
+  // Don't do segment extension for p_align > 64KiB, such ELFs already existed in the
+  // field e.g. 2MiB p_align for THPs and are relatively small in number.
+  //
+  // The kernel can only represent padding for p_align up to 64KiB. This is because
+  // the kernel uses 4 available bits in the vm_area_struct to represent padding
+  // extent; and so cannot enable mitigations to avoid breaking app compatibility for
+  // p_aligns > 64KiB.
+  //
+  // Don't perform segment extension on these to avoid app compatibility issues.
+  if (phdr->p_align <= kPageSize || phdr->p_align > 64*1024 || !should_pad_segments) {
     return;
   }
 
@@ -887,10 +918,28 @@
     //   2) Break the COW backing, faulting in new anon pages for a region
     //      that will not be used.
 
-    // _seg_file_end = unextended seg_file_end
-    uint64_t _seg_file_end = seg_start + phdr->p_filesz;
-    if ((phdr->p_flags & PF_W) != 0 && page_offset(_seg_file_end) > 0) {
-      memset(reinterpret_cast<void*>(_seg_file_end), 0, kPageSize - page_offset(_seg_file_end));
+    uint64_t unextended_seg_file_end = seg_start + phdr->p_filesz;
+    if ((phdr->p_flags & PF_W) != 0 && page_offset(unextended_seg_file_end) > 0) {
+      memset(reinterpret_cast<void*>(unextended_seg_file_end), 0,
+             kPageSize - page_offset(unextended_seg_file_end));
+    }
+
+    // Pages may be brought in due to readahead.
+    // Drop the padding (zero) pages, to avoid reclaim work later.
+    //
+    // NOTE: The madvise() here is special, as it also serves to hint to the
+    // kernel the portion of the LOAD segment that is padding.
+    //
+    // See: [1] https://android-review.googlesource.com/c/kernel/common/+/3032411
+    //      [2] https://android-review.googlesource.com/c/kernel/common/+/3048835
+    uint64_t pad_start = page_end(unextended_seg_file_end);
+    uint64_t pad_end = page_end(seg_file_end);
+    CHECK(pad_start <= pad_end);
+    uint64_t pad_len = pad_end - pad_start;
+    if (page_size_migration_supported() && pad_len > 0 &&
+        madvise(reinterpret_cast<void*>(pad_start), pad_len, MADV_DONTNEED)) {
+      DL_WARN("\"%s\": madvise(0x%" PRIx64 ", 0x%" PRIx64 ", MADV_DONTNEED) failed: %m",
+              name_.c_str(), pad_start, pad_len);
     }
 
     seg_file_end = page_end(seg_file_end);
diff --git a/linker/linker_phdr.h b/linker/linker_phdr.h
index 61242eb..aab9018 100644
--- a/linker/linker_phdr.h
+++ b/linker/linker_phdr.h
@@ -154,3 +154,5 @@
 
 const char* phdr_table_get_interpreter_name(const ElfW(Phdr)* phdr_table, size_t phdr_count,
                                             ElfW(Addr) load_bias);
+
+bool page_size_migration_supported();
diff --git a/tests/clang_fortify_tests.cpp b/tests/clang_fortify_tests.cpp
index 544af43..f4ef4ac 100644
--- a/tests/clang_fortify_tests.cpp
+++ b/tests/clang_fortify_tests.cpp
@@ -164,9 +164,7 @@
     const char large_string[] = "Hello!!!";
     static_assert(sizeof(large_string) > sizeof(small_buffer), "");
 
-#if __clang_major__ > 13
-    // expected-error@+3{{will always overflow}}
-#endif
+    // expected-error@+2{{will always overflow}}
     // expected-error@+1{{string bigger than buffer}}
     EXPECT_FORTIFY_DEATH(strcpy(small_buffer, large_string));
     // expected-error@+1{{string bigger than buffer}}
@@ -204,9 +202,7 @@
     static_assert(sizeof(small_string) > sizeof(split.tiny_buffer), "");
 
 #if _FORTIFY_SOURCE > 1
-#if __clang_major__ > 13
-    // expected-error@+4{{will always overflow}}
-#endif
+    // expected-error@+3{{will always overflow}}
     // expected-error@+2{{string bigger than buffer}}
 #endif
     EXPECT_FORTIFY_DEATH_STRUCT(strcpy(split.tiny_buffer, small_string));