Merge GNU_PROPERTY_AARCH64_FEATURE_1_AND

We used to merge only x86 properties in .note.gnu.property, so an ARM64
output lost GNU_PROPERTY_AARCH64_FEATURE_1_AND even if all its inputs
were compiled with -mbranch-protection. We now AND-merge it as GNU ld
and lld do, and merge x86 properties only on x86.

elf/chunks/note_property.rs

@@ -2,7 +2,7 @@
 
 use std::collections::{BTreeMap, BTreeSet};
 
-use crate::arch::Target;
+use crate::arch::{Family, Target};
 use crate::chunks::ChunkHeader;
 use crate::context::Context;
 use crate::elf::*;
@@ -46,15 +46,21 @@ pub fn update_shdr<E: Target>(ctx: &mut Context<E>) {
     // Merge values for each key
     let mut map: BTreeMap<u32, u32> = BTreeMap::new();
     for key in keys {
-        if (GNU_PROPERTY_X86_UINT32_AND_LO..=GNU_PROPERTY_X86_UINT32_AND_HI).contains(&key) {
+        if (E::IS_X86
+            && (GNU_PROPERTY_X86_UINT32_AND_LO..=GNU_PROPERTY_X86_UINT32_AND_HI).contains(&key))
+            || (E::FAMILY == Family::Arm64 && key == GNU_PROPERTY_AARCH64_FEATURE_1_AND)
+        {
             // An AND feature is set if all input objects have the property and
             // the feature.
             map.insert(key, files.iter().fold(u32::MAX, |acc, f| acc & value(f, key)));
-        } else if (GNU_PROPERTY_X86_UINT32_OR_LO..=GNU_PROPERTY_X86_UINT32_OR_HI).contains(&key) {
+        } else if E::IS_X86
+            && (GNU_PROPERTY_X86_UINT32_OR_LO..=GNU_PROPERTY_X86_UINT32_OR_HI).contains(&key)
+        {
             // An OR feature is set if some input object has the feature.
             map.insert(key, files.iter().fold(0, |acc, f| acc | value(f, key)));
-        } else if (GNU_PROPERTY_X86_UINT32_OR_AND_LO..=GNU_PROPERTY_X86_UINT32_OR_AND_HI)
-            .contains(&key)
+        } else if E::IS_X86
+            && (GNU_PROPERTY_X86_UINT32_OR_AND_LO..=GNU_PROPERTY_X86_UINT32_OR_AND_HI)
+                .contains(&key)
         {
             // An OR-AND feature is set if all input object files have the property
             // and some of them have the feature.
@@ -64,13 +70,17 @@ pub fn update_shdr<E: Target>(ctx: &mut Context<E>) {
         }
     }
 
-    if ctx.args.z_ibt {
-        *map.entry(GNU_PROPERTY_X86_FEATURE_1_AND).or_insert(0) |= GNU_PROPERTY_X86_FEATURE_1_IBT;
+    if E::IS_X86 {
+        if ctx.args.z_ibt {
+            *map.entry(GNU_PROPERTY_X86_FEATURE_1_AND).or_insert(0) |=
+                GNU_PROPERTY_X86_FEATURE_1_IBT;
+        }
+        if ctx.args.z_shstk {
+            *map.entry(GNU_PROPERTY_X86_FEATURE_1_AND).or_insert(0) |=
+                GNU_PROPERTY_X86_FEATURE_1_SHSTK;
+        }
+        *map.entry(GNU_PROPERTY_X86_ISA_1_NEEDED).or_insert(0) |= ctx.args.z_x86_64_isa_level;
     }
-    if ctx.args.z_shstk {
-        *map.entry(GNU_PROPERTY_X86_FEATURE_1_AND).or_insert(0) |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
-    }
-    *map.entry(GNU_PROPERTY_X86_ISA_1_NEEDED).or_insert(0) |= ctx.args.z_x86_64_isa_level;
 
     // Serialize the map
     let contents: Vec<(u32, u32)> = map.into_iter().filter(|&(_, v)| v != 0).collect();

elf/elf_consts.rs

@@ -264,6 +264,11 @@ pub const GNU_PROPERTY_X86_ISA_1_V2: u32 = 2;
 pub const GNU_PROPERTY_X86_ISA_1_V3: u32 = 4;
 pub const GNU_PROPERTY_X86_ISA_1_V4: u32 = 8;
 
+pub const GNU_PROPERTY_AARCH64_FEATURE_1_AND: u32 = 0xc0000000;
+pub const GNU_PROPERTY_AARCH64_FEATURE_1_BTI: u32 = 1;
+pub const GNU_PROPERTY_AARCH64_FEATURE_1_PAC: u32 = 2;
+pub const GNU_PROPERTY_AARCH64_FEATURE_1_GCS: u32 = 4;
+
 pub const ELFCOMPRESS_NONE: u32 = 0;
 pub const ELFCOMPRESS_ZLIB: u32 = 1;
 pub const ELFCOMPRESS_ZSTD: u32 = 2;

elf/passes.rs

@@ -174,7 +174,7 @@ pub fn create_synthetic_sections<E: Target>(ctx: &mut Context<E>) {
     chunks.push(ChunkId::Verneed);
     chunks.push(ChunkId::NotePackage);
 
-    if E::IS_X86 {
+    if E::IS_X86 || E::FAMILY == Family::Arm64 {
         ctx.note_property = Some(NotePropertySection::<E>::new());
         chunks.push(ChunkId::NoteProperty);
     }

elf/relocatable.rs

@@ -34,7 +34,7 @@ use std::collections::HashMap;
 
 use mold_common::util::align_to;
 
-use crate::arch::Target;
+use crate::arch::{Family, Target};
 use crate::chunks::comdat_group::ComdatGroupSection;
 use crate::chunks::note_property::NotePropertySection;
 use crate::chunks::output_section::{self, OutputSection};
@@ -109,7 +109,7 @@ fn create_synthetic_sections<E: Target>(ctx: &mut Context<E>) {
         ChunkId::Symtab,
         ChunkId::Shstrtab,
     ]);
-    if E::IS_X86 {
+    if E::IS_X86 || E::FAMILY == Family::Arm64 {
         ctx.note_property = Some(NotePropertySection::<E>::new());
         ctx.chunks.push(ChunkId::NoteProperty);
     }

tests/elf/arch-aarch64-note-property.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+. $(dirname $0)/common.inc
+
+test_cflags -mbranch-protection=standard || skip
+
+cat <<EOF | $CC -mbranch-protection=standard -c -o $t/a.o -xc -
+void _start() {}
+EOF
+
+cat <<EOF | $CC -mbranch-protection=standard -c -o $t/b.o -xc -
+void foo() {}
+EOF
+
+cat <<EOF | $CC -mbranch-protection=bti -c -o $t/c.o -xc -
+void bar() {}
+EOF
+
+cat <<EOF | $CC -mbranch-protection=none -c -o $t/d.o -xc -
+void baz() {}
+EOF
+
+./mold -o $t/exe1 $t/a.o $t/b.o
+readelf -n $t/exe1 | grep 'AArch64 feature: BTI, PAC'
+readelf -W --segments $t/exe1 | grep -w GNU_PROPERTY
+
+./mold -o $t/exe2 $t/a.o $t/b.o $t/c.o
+readelf -n $t/exe2 | grep 'AArch64 feature: BTI$'
+
+./mold -o $t/exe3 $t/a.o $t/b.o $t/c.o $t/d.o
+readelf -n $t/exe3 | not grep 'AArch64 feature'
+
+./mold -r -o $t/e.o $t/a.o $t/b.o
+readelf -n $t/e.o | grep 'AArch64 feature: BTI, PAC'