From 47ad587a52f36f0d4c98a29b37e4ddfa07eb78fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Miku=C5=82a?= <oss@mateuszmikula.dev>
Date: Fri, 3 Apr 2026 21:02:50 +0200
Subject: [PATCH] feat: Support `--use-android-relr-tags`

---
 libwild/src/args/elf.rs   | 22 +++++++++++++++--
 libwild/src/elf_writer.rs | 52 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 68 insertions(+), 6 deletions(-)

diff --git a/libwild/src/args/elf.rs b/libwild/src/args/elf.rs
index 608f38c6c..2d60e5ce2 100644
--- a/libwild/src/args/elf.rs
+++ b/libwild/src/args/elf.rs
@@ -115,6 +115,7 @@ pub struct ElfArgs {
     pub(crate) max_page_size: Option<Alignment>,
     pub(crate) trace: bool,
     pack_dyn_relocs: PackDynRelocs,
+    pub(crate) use_android_relr_tags: bool,
 
     pub(crate) relocation_model: RelocationModel,
     pub(crate) should_output_executable: bool,
@@ -217,7 +218,6 @@ pub(super) const IGNORED_FLAGS: &[&str] = &[
     "fix-cortex-a53-835769",
     "fix-cortex-a53-843419",
     "discard-all",
-    "use-android-relr-tags",
     "x", // alias for --discard-all
 ];
 
@@ -228,7 +228,6 @@ const DEFAULT_FLAGS: &[&str] = &[
     "no-add-needed",
     "discard-locals",
     "no-fatal-warnings",
-    "no-use-android-relr-tags",
 ];
 const DEFAULT_SHORT_FLAGS: &[&str] = &[
     "X",  // alias for --discard-locals
@@ -292,6 +291,7 @@ impl Default for ElfArgs {
             hash_style: HashStyle::Both,
             trace: false,
             pack_dyn_relocs: PackDynRelocs::None,
+            use_android_relr_tags: false,
 
             unresolved_symbols: UnresolvedSymbols::ReportAll,
             error_unresolved_symbols: true,
@@ -1709,6 +1709,24 @@ fn setup_argument_parser() -> ArgumentParser<ElfArgs> {
             Ok(())
         });
 
+    parser
+        .declare()
+        .long("use-android-relr-tags")
+        .help("Use Android version of SHT_RELR and DT_RELR")
+        .execute(|args, _modifier_stack| {
+            args.use_android_relr_tags = true;
+            Ok(())
+        });
+
+    parser
+        .declare()
+        .long("no-use-android-relr-tags")
+        .help("Do not use Android version of SHT_RELR and DT_RELR (default)")
+        .execute(|args, _modifier_stack| {
+            args.use_android_relr_tags = false;
+            Ok(())
+        });
+
     add_silently_ignored_flags(&mut parser);
     add_default_flags(&mut parser);
 
diff --git a/libwild/src/elf_writer.rs b/libwild/src/elf_writer.rs
index 525d40bd2..2eded24e7 100644
--- a/libwild/src/elf_writer.rs
+++ b/libwild/src/elf_writer.rs
@@ -4577,17 +4577,50 @@ const EPILOGUE_DYNAMIC_ENTRY_WRITERS: &[DynamicEntryWriter] = &[
     }),
     DynamicEntryWriter::optional(
         object::elf::DT_RELR,
-        |inputs| inputs.has_data_in_section(output_section_id::RELR_DYN),
+        |inputs| {
+            inputs.has_data_in_section(output_section_id::RELR_DYN)
+                && !has_android_relr_tags(inputs)
+        },
         |inputs| inputs.vma_of_section(output_section_id::RELR_DYN),
     ),
     DynamicEntryWriter::optional(
         object::elf::DT_RELRSZ,
-        |inputs| inputs.has_data_in_section(output_section_id::RELR_DYN),
+        |inputs| {
+            inputs.has_data_in_section(output_section_id::RELR_DYN)
+                && !has_android_relr_tags(inputs)
+        },
         |inputs| inputs.size_of_section(output_section_id::RELR_DYN),
     ),
     DynamicEntryWriter::optional(
         object::elf::DT_RELRENT,
-        |inputs| inputs.has_data_in_section(output_section_id::RELR_DYN),
+        |inputs| {
+            inputs.has_data_in_section(output_section_id::RELR_DYN)
+                && !has_android_relr_tags(inputs)
+        },
+        |_| elf::RELR_ENTRY_SIZE,
+    ),
+    DynamicEntryWriter::optional(
+        // TODO(object): Not yet added
+        0x6fff_e000,
+        |inputs| {
+            inputs.has_data_in_section(output_section_id::RELR_DYN) && has_android_relr_tags(inputs)
+        },
+        |inputs| inputs.vma_of_section(output_section_id::RELR_DYN),
+    ),
+    DynamicEntryWriter::optional(
+        // TODO(object): Not yet added
+        0x6fff_e001,
+        |inputs| {
+            inputs.has_data_in_section(output_section_id::RELR_DYN) && has_android_relr_tags(inputs)
+        },
+        |inputs| inputs.size_of_section(output_section_id::RELR_DYN),
+    ),
+    DynamicEntryWriter::optional(
+        // TODO(object): Not yet added
+        0x6fff_e003,
+        |inputs| {
+            inputs.has_data_in_section(output_section_id::RELR_DYN) && has_android_relr_tags(inputs)
+        },
         |_| elf::RELR_ENTRY_SIZE,
     ),
     DynamicEntryWriter::optional(
@@ -4849,7 +4882,14 @@ fn write_section_headers(out: &mut [u8], layout: &ElfLayout) -> Result {
         let entry = entries.next().unwrap();
         let e = LittleEndian;
         entry.sh_name.set(e, name_offset);
-        entry.sh_type.set(e, section_type.raw());
+
+        let sh_type = if layout.args().use_android_relr_tags && section_type == sht::RELR {
+            // TODO(object): Not yet added
+            0x6fffff00
+        } else {
+            section_type.raw()
+        };
+        entry.sh_type.set(e, sh_type);
 
         // TODO: Sections are always uncompressed and the output compression is not supported yet.
         entry.sh_flags.set(
@@ -5267,6 +5307,10 @@ fn has_rela_dyn(inputs: &DynamicEntryInputs) -> bool {
     relative.mem_size > 0 || general.mem_size > 0
 }
 
+fn has_android_relr_tags(inputs: &DynamicEntryInputs) -> bool {
+    inputs.args.use_android_relr_tags
+}
+
 pub(crate) fn verify_resolution_allocation(
     output_sections: &OutputSections<Elf>,
     output_order: &OutputOrder,