refactor: align platform crate boundaries

senbei-elf/src/lib.rs

@@ -3,6 +3,64 @@
 use goblin::elf::{Elf, header::EM_AARCH64, program_header::PT_LOAD};
 use thiserror::Error;
 
+pub mod hash;
+pub mod layout;
+
+pub use hash::{build_gnu_hash, build_sysv_hash};
+pub use layout::{
+    ElfLayout, LoadSegment, PF_R, SHF_ALLOC, SHT_LOUSER, SHT_NOBITS, SectionHeader, align_up,
+    checked_index, read_i64, read_u16, read_u32, read_u64, slice, slice_u64, usize_from_u64,
+};
+
+/// ELF machine identifier for AArch64.
+pub const AARCH64_MACHINE: u16 = EM_AARCH64;
+
+/// Dynamic sections required by the restored AArch64 loader image.
+pub const DYNAMIC_SECTION_NAMES: [&str; 8] = [
+    ".dynsym",
+    ".gnu.version",
+    ".gnu.version_r",
+    ".gnu.hash",
+    ".dynstr",
+    ".rela.dyn",
+    ".rela.plt",
+    ".dynamic",
+];
+
+/// Dynamic sections needed to identify a protected image before extraction.
+pub const PROBE_SECTION_NAMES: [&str; 5] = [
+    ".dynsym",
+    ".dynstr",
+    ".gnu.hash",
+    ".gnu.version",
+    ".gnu.version_r",
+];
+
+/// ELF64 dynamic table record sizes.
+pub const ELF64_SYMBOL_SIZE: usize = 0x18;
+pub const ELF64_RELA_SIZE: usize = 0x18;
+
+/// AArch64 relocation kinds used by the dynamic linker.
+pub const R_AARCH64_ABS64: u32 = 0x101;
+pub const R_AARCH64_GLOB_DAT: u32 = 0x401;
+pub const R_AARCH64_JUMP_SLOT: u32 = 0x402;
+pub const R_AARCH64_RELATIVE: u32 = 0x403;
+pub const VER_NDX_GLOBAL: u16 = 1;
+
+/// ELF dynamic-table tag identifiers used by restored images.
+pub const DT_PLTRELSZ: u64 = 2;
+pub const DT_HASH: u64 = 4;
+pub const DT_STRTAB: u64 = 5;
+pub const DT_SYMTAB: u64 = 6;
+pub const DT_RELA: u64 = 7;
+pub const DT_RELASZ: u64 = 8;
+pub const DT_STRSZ: u64 = 10;
+pub const DT_JMPREL: u64 = 23;
+pub const DT_GNU_HASH: u64 = 0x6fff_fef5;
+pub const DT_VERSYM: u64 = 0x6fff_fff0;
+pub const DT_RELACOUNT: u64 = 0x6fff_fff9;
+pub const DT_VERNEED: u64 = 0x6fff_fffe;
+
 #[derive(Debug, Error)]
 pub enum Error {
     #[error("ELF parse failed: {0}")]
@@ -11,6 +69,8 @@ pub enum Error {
     NotElf64,
     #[error("input is not an AArch64 image")]
     NotAarch64,
+    #[error("invalid ELF layout: {0}")]
+    Invalid(String),
 }
 
 pub type Result<T> = std::result::Result<T, Error>;
@@ -31,6 +91,17 @@ pub fn is_aarch64(data: &[u8]) -> bool {
         .unwrap_or(false)
 }
 
+/// Return whether a short prefix identifies an ELF64 little-endian AArch64
+/// image. This is intentionally a prefix-only check for filesystem scanners;
+/// callers that need structural guarantees must use [`parse`].
+#[must_use]
+pub fn is_aarch64_prefix(data: &[u8]) -> bool {
+    data.get(0..6) == Some(b"\x7fELF\x02\x01")
+        && data
+            .get(18..20)
+            .is_some_and(|bytes| u16::from_le_bytes([bytes[0], bytes[1]]) == EM_AARCH64)
+}
+
 /// Return the maximum file end among PT_LOAD segments.
 pub fn load_file_end(data: &[u8]) -> Result<u64> {
     let elf = parse(data)?;
@@ -43,6 +114,10 @@ pub fn load_file_end(data: &[u8]) -> Result<u64> {
         .unwrap_or(0))
 }
 
+pub(crate) fn invalid<T>(message: impl Into<String>) -> Result<T> {
+    Err(Error::Invalid(message.into()))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;