diff --git a/linker/linker_phdr.h b/linker/linker_phdr.h
index a30fe33..2f159f3 100644
--- a/linker/linker_phdr.h
+++ b/linker/linker_phdr.h
@@ -39,6 +39,13 @@
 #include "linker_mapped_file_fragment.h"
 #include "linker_note_gnu_property.h"
 
+#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) | \
+                                      MAYBE_MAP_FLAG((x), PF_W, PROT_WRITE))
+
+static constexpr size_t kCompatPageSize = 0x1000;
+
 class ElfReader {
  public:
   ElfReader();
@@ -60,6 +67,8 @@
   ElfW(Addr) entry_point() const { return header_.e_entry + load_bias_; }
   bool should_pad_segments() const { return should_pad_segments_; }
   bool should_use_16kib_app_compat() const { return should_use_16kib_app_compat_; }
+  ElfW(Addr) compat_relro_start() const { return compat_relro_start_; }
+  ElfW(Addr) compat_relro_size() const { return compat_relro_size_; }
 
  private:
   [[nodiscard]] bool ReadElfHeader();
@@ -70,10 +79,14 @@
   [[nodiscard]] bool ReadPadSegmentNote();
   [[nodiscard]] bool ReserveAddressSpace(address_space_params* address_space);
   [[nodiscard]] bool MapSegment(size_t seg_idx, size_t len);
+  [[nodiscard]] bool CompatMapSegment(size_t seg_idx, size_t len);
   void ZeroFillSegment(const ElfW(Phdr)* phdr);
   void DropPaddingPages(const ElfW(Phdr)* phdr, uint64_t seg_file_end);
   [[nodiscard]] bool MapBssSection(const ElfW(Phdr)* phdr, ElfW(Addr) seg_page_end,
                                    ElfW(Addr) seg_file_end);
+  [[nodiscard]] bool IsEligibleFor16KiBAppCompat(ElfW(Addr)* vaddr);
+  [[nodiscard]] bool HasAtMostOneRelroSegment(const ElfW(Phdr)** relro_phdr);
+  [[nodiscard]] bool Setup16KiBAppCompat();
   [[nodiscard]] bool LoadSegments();
   [[nodiscard]] bool FindPhdr();
   [[nodiscard]] bool FindGnuPropertySection();
@@ -127,6 +140,10 @@
   // Use app compat mode when loading 4KiB max-page-size ELFs on 16KiB page-size devices?
   bool should_use_16kib_app_compat_ = false;
 
+  // RELRO region for 16KiB compat loading
+  ElfW(Addr) compat_relro_start_ = 0;
+  ElfW(Addr) compat_relro_size_ = 0;
+
   // Only used by AArch64 at the moment.
   GnuPropertySection note_gnu_property_ __unused;
 };
@@ -150,6 +167,8 @@
                                  ElfW(Addr) load_bias, bool should_pad_segments,
                                  bool should_use_16kib_app_compat);
 
+int phdr_table_protect_gnu_relro_16kib_compat(ElfW(Addr) start, ElfW(Addr) size);
+
 int phdr_table_serialize_gnu_relro(const ElfW(Phdr)* phdr_table, size_t phdr_count,
                                    ElfW(Addr) load_bias, int fd, size_t* file_offset);