Add GNU Property Note

Cargo.toml

@@ -3,7 +3,7 @@ name = "object"
 version = "0.31.0"
 edition = "2018"
 exclude = ["/.github", "/testfiles"]
-keywords = ["object", "elf", "mach-o", "pe", "coff", "xcoff"]
+keywords = ["object", "elf", "mach-o", "pe", "coff"]
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/gimli-rs/object"
 description = "A unified interface for reading and writing object file formats."

src/elf.rs

@@ -1900,6 +1900,20 @@ pub const NT_GNU_GOLD_VERSION: u32 = 4;
 pub const NT_GNU_PROPERTY_TYPE_0: u32 = 5;
 
 // TODO: GNU_PROPERTY_*
+
+/// GNU Property Type for X86
+pub const GNU_PROPERTY_X86_FEATURE_1_AND: u32 = 0xc0000002;
+/// GNU Property Type for IBT X86
+pub const GNU_PROPERTY_X86_FEATURE_1_IBT: u32 = 1 << 0;
+/// GNU Property Type for SHSTK X86
+pub const GNU_PROPERTY_X86_FEATURE_1_SHSTK: u32 = 1 << 1;
+/// GNU Property Type for AARCH64
+pub const GNU_PROPERTY_AARCH64_FEATURE_1_AND: u32 = 0xc0000000;
+/// GNU Property Type for BTI  AArch64
+pub const GNU_PROPERTY_AARCH64_FEATURE_1_BTI: u32 = 1 << 0;
+/// GNU Property Type for PAC AArch64
+pub const GNU_PROPERTY_AARCH64_FEATURE_1_PAC: u32 = 1 << 0;
+
 // TODO: Elf*_Move
 
 /// Header of `SHT_HASH` section.