267 lines
9.7 KiB
Zig
267 lines
9.7 KiB
Zig
const io = @import("io.zig");
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const math = @import("math.zig");
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const mem = @import("mem.zig");
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const debug = @import("debug.zig");
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error InvalidFormat;
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pub const SHT_NULL = 0;
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pub const SHT_PROGBITS = 1;
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pub const SHT_SYMTAB = 2;
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pub const SHT_STRTAB = 3;
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pub const SHT_RELA = 4;
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pub const SHT_HASH = 5;
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pub const SHT_DYNAMIC = 6;
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pub const SHT_NOTE = 7;
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pub const SHT_NOBITS = 8;
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pub const SHT_REL = 9;
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pub const SHT_SHLIB = 10;
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pub const SHT_DYNSYM = 11;
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pub const SHT_INIT_ARRAY = 14;
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pub const SHT_FINI_ARRAY = 15;
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pub const SHT_PREINIT_ARRAY = 16;
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pub const SHT_GROUP = 17;
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pub const SHT_SYMTAB_SHNDX = 18;
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pub const SHT_LOOS = 0x60000000;
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pub const SHT_HIOS = 0x6fffffff;
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pub const SHT_LOPROC = 0x70000000;
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pub const SHT_HIPROC = 0x7fffffff;
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pub const SHT_LOUSER = 0x80000000;
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pub const SHT_HIUSER = 0xffffffff;
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pub const FileType = enum {
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Relocatable,
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Executable,
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Shared,
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Core,
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};
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// TODO rename this to Arch when the builtin Arch enum is namespaced
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// or make debug info work for builtin enums
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pub const ElfArch = enum {
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Sparc,
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x86,
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Mips,
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PowerPc,
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Arm,
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SuperH,
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IA_64,
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x86_64,
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AArch64,
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};
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pub const SectionHeader = struct {
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name: u32,
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sh_type: u32,
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flags: u64,
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addr: u64,
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offset: u64,
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size: u64,
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link: u32,
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info: u32,
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addr_align: u64,
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ent_size: u64,
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};
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pub const Elf = struct {
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in_stream: &io.InStream,
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auto_close_stream: bool,
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is_64: bool,
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is_big_endian: bool,
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file_type: FileType,
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arch: ElfArch,
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entry_addr: u64,
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program_header_offset: u64,
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section_header_offset: u64,
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string_section_index: u64,
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string_section: &SectionHeader,
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section_headers: []SectionHeader,
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allocator: &mem.Allocator,
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prealloc_stream: io.InStream,
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/// Call close when done.
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pub fn openFile(elf: &Elf, allocator: &mem.Allocator, path: []const u8) -> %void {
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%return elf.prealloc_stream.open(path);
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%return elf.openStream(allocator, &elf.prealloc_stream);
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elf.auto_close_stream = true;
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}
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/// Call close when done.
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pub fn openStream(elf: &Elf, allocator: &mem.Allocator, stream: &io.InStream) -> %void {
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elf.allocator = allocator;
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elf.in_stream = stream;
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elf.auto_close_stream = false;
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var magic: [4]u8 = undefined;
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%return elf.in_stream.readNoEof(magic);
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if (!mem.eql(magic, "\x7fELF")) return error.InvalidFormat;
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elf.is_64 = switch (%return elf.in_stream.readByte()) {
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1 => false,
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2 => true,
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else => return error.InvalidFormat,
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};
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elf.is_big_endian = switch (%return elf.in_stream.readByte()) {
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1 => false,
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2 => true,
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else => return error.InvalidFormat,
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};
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const version_byte = %return elf.in_stream.readByte();
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if (version_byte != 1) return error.InvalidFormat;
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// skip over padding
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%return elf.in_stream.seekForward(9);
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elf.file_type = switch (%return elf.in_stream.readInt(elf.is_big_endian, u16)) {
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1 => FileType.Relocatable,
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2 => FileType.Executable,
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3 => FileType.Shared,
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4 => FileType.Core,
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else => return error.InvalidFormat,
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};
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elf.arch = switch (%return elf.in_stream.readInt(elf.is_big_endian, u16)) {
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0x02 => ElfArch.Sparc,
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0x03 => ElfArch.x86,
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0x08 => ElfArch.Mips,
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0x14 => ElfArch.PowerPc,
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0x28 => ElfArch.Arm,
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0x2A => ElfArch.SuperH,
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0x32 => ElfArch.IA_64,
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0x3E => ElfArch.x86_64,
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0xb7 => ElfArch.AArch64,
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else => return error.InvalidFormat,
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};
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const elf_version = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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if (elf_version != 1) return error.InvalidFormat;
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if (elf.is_64) {
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elf.entry_addr = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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elf.program_header_offset = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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elf.section_header_offset = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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} else {
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elf.entry_addr = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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elf.program_header_offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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elf.section_header_offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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}
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// skip over flags
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%return elf.in_stream.seekForward(4);
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const header_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
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if ((elf.is_64 && header_size != 64) ||
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(!elf.is_64 && header_size != 52))
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{
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return error.InvalidFormat;
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}
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const ph_entry_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
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const ph_entry_count = %return elf.in_stream.readInt(elf.is_big_endian, u16);
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const sh_entry_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
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const sh_entry_count = %return elf.in_stream.readInt(elf.is_big_endian, u16);
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elf.string_section_index = u64(%return elf.in_stream.readInt(elf.is_big_endian, u16));
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if (elf.string_section_index >= sh_entry_count) return error.InvalidFormat;
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const sh_byte_count = u64(sh_entry_size) * u64(sh_entry_count);
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const end_sh = %return math.addOverflow(u64, elf.section_header_offset, sh_byte_count);
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const ph_byte_count = u64(ph_entry_size) * u64(ph_entry_count);
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const end_ph = %return math.addOverflow(u64, elf.program_header_offset, ph_byte_count);
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const stream_end = %return elf.in_stream.getEndPos();
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if (stream_end < end_sh || stream_end < end_ph) {
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return error.InvalidFormat;
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}
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%return elf.in_stream.seekTo(elf.section_header_offset);
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elf.section_headers = %return elf.allocator.alloc(SectionHeader, sh_entry_count);
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%defer elf.allocator.free(elf.section_headers);
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if (elf.is_64) {
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if (sh_entry_size != 64) return error.InvalidFormat;
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for (elf.section_headers) |*section| {
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section.name = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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section.sh_type = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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section.flags = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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section.addr = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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section.offset = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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section.size = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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section.link = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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section.info = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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section.addr_align = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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section.ent_size = %return elf.in_stream.readInt(elf.is_big_endian, u64);
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}
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} else {
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if (sh_entry_size != 40) return error.InvalidFormat;
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for (elf.section_headers) |*section| {
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// TODO (multiple occurences) allow implicit cast from %u32 -> %u64 ?
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section.name = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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section.sh_type = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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section.flags = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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section.addr = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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section.offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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section.size = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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section.link = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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section.info = %return elf.in_stream.readInt(elf.is_big_endian, u32);
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section.addr_align = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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section.ent_size = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
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}
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}
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for (elf.section_headers) |*section| {
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if (section.sh_type != SHT_NOBITS) {
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const file_end_offset = %return math.addOverflow(u64,
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section.offset, section.size);
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if (stream_end < file_end_offset) return error.InvalidFormat;
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}
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}
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elf.string_section = &elf.section_headers[elf.string_section_index];
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if (elf.string_section.sh_type != SHT_STRTAB) {
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// not a string table
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return error.InvalidFormat;
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}
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}
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pub fn close(elf: &Elf) {
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elf.allocator.free(elf.section_headers);
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if (elf.auto_close_stream)
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elf.in_stream.close();
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}
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pub fn findSection(elf: &Elf, name: []u8) -> %?&SectionHeader {
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for (elf.section_headers) |*section| {
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if (section.sh_type == SHT_NULL) continue;
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const name_offset = elf.string_section.offset + section.name;
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%return elf.in_stream.seekTo(name_offset);
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for (name) |expected_c| {
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const target_c = %return elf.in_stream.readByte();
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if (target_c == 0 || expected_c != target_c) goto next_section;
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}
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{
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const null_byte = %return elf.in_stream.readByte();
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if (null_byte == 0) return (?&SectionHeader)(section);
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}
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next_section:
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}
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const null_sh: ?&SectionHeader = null;
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return null_sh;
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}
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pub fn seekToSection(elf: &Elf, section: &SectionHeader) -> %void {
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%return elf.in_stream.seekTo(section.offset);
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}
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};
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