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feat: Support --use-android-relr-tags #1805

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feat: Support --use-android-relr-tags #1805

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22 changes: 20 additions & 2 deletions libwild/src/args/elf.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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,
Expand Down Expand Up @@ -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
];

Expand 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
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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);

Expand Down
52 changes: 48 additions & 4 deletions libwild/src/elf_writer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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(
Expand Down Expand Up @@ -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(
Expand Down Expand Up @@ -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,
Expand Down
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