Commit ed13cffca4

Andrew Kelley <andrew@ziglang.org>
2020-03-11 03:01:58
rework some old ELF parsing code and start to fix emitRaw
1 parent bd14a81
Changed files (3)
lib/std/build/emit_raw.zig
@@ -14,11 +14,6 @@ const io = std.io;
 const sort = std.sort;
 const warn = std.debug.warn;
 
-const BinOutStream = io.OutStream(anyerror);
-const BinSeekStream = io.SeekableStream(anyerror, anyerror);
-const ElfSeekStream = io.SeekableStream(anyerror, anyerror);
-const ElfInStream = io.InStream(anyerror);
-
 const BinaryElfSection = struct {
     elfOffset: u64,
     binaryOffset: u64,
@@ -41,22 +36,21 @@ const BinaryElfOutput = struct {
 
     const Self = @This();
 
-    pub fn init(allocator: *Allocator) Self {
-        return Self{
-            .segments = ArrayList(*BinaryElfSegment).init(allocator),
-            .sections = ArrayList(*BinaryElfSection).init(allocator),
-        };
-    }
-
     pub fn deinit(self: *Self) void {
         self.sections.deinit();
         self.segments.deinit();
     }
 
-    pub fn parseElf(self: *Self, elfFile: elf.Elf) !void {
-        const allocator = self.segments.allocator;
+    pub fn parse(allocator: *Allocator, elf_file: File) !Self {
+        var self: Self = .{
+            .segments = ArrayList(*BinaryElfSegment).init(allocator),
+            .sections = ArrayList(*BinaryElfSection).init(allocator),
+        };
+        const elf_hdrs = try std.elf.readAllHeaders(allocator, elf_file);
 
-        for (elfFile.section_headers) |section, i| {
+        var binaryElfOutput = BinaryElfOutput.init(arena_allocator);
+
+        for (elf_hdrs.section_headers) |section, i| {
             if (sectionValidForOutput(section)) {
                 const newSection = try allocator.create(BinaryElfSection);
 
@@ -69,19 +63,19 @@ const BinaryElfOutput = struct {
             }
         }
 
-        for (elfFile.program_headers) |programHeader, i| {
-            if (programHeader.p_type == elf.PT_LOAD) {
+        for (elf_hdrs.program_headers) |phdr, i| {
+            if (phdr.p_type == elf.PT_LOAD) {
                 const newSegment = try allocator.create(BinaryElfSegment);
 
-                newSegment.physicalAddress = if (programHeader.p_paddr != 0) programHeader.p_paddr else programHeader.p_vaddr;
-                newSegment.virtualAddress = programHeader.p_vaddr;
-                newSegment.fileSize = @intCast(usize, programHeader.p_filesz);
-                newSegment.elfOffset = programHeader.p_offset;
+                newSegment.physicalAddress = if (phdr.p_paddr != 0) phdr.p_paddr else phdr.p_vaddr;
+                newSegment.virtualAddress = phdr.p_vaddr;
+                newSegment.fileSize = @intCast(usize, phdr.p_filesz);
+                newSegment.elfOffset = phdr.p_offset;
                 newSegment.binaryOffset = 0;
                 newSegment.firstSection = null;
 
                 for (self.sections.toSlice()) |section| {
-                    if (sectionWithinSegment(section, programHeader)) {
+                    if (sectionWithinSegment(section, phdr)) {
                         if (section.segment) |sectionSegment| {
                             if (sectionSegment.elfOffset > newSegment.elfOffset) {
                                 section.segment = newSegment;
@@ -126,14 +120,17 @@ const BinaryElfOutput = struct {
         }
 
         sort.sort(*BinaryElfSection, self.sections.toSlice(), sectionSortCompare);
+
+        return self;
     }
 
-    fn sectionWithinSegment(section: *BinaryElfSection, segment: elf.ProgramHeader) bool {
+    fn sectionWithinSegment(section: *BinaryElfSection, segment: elf.Elf64_Phdr) bool {
         return segment.p_offset <= section.elfOffset and (segment.p_offset + segment.p_filesz) >= (section.elfOffset + section.fileSize);
     }
 
-    fn sectionValidForOutput(section: elf.SectionHeader) bool {
-        return section.sh_size > 0 and section.sh_type != elf.SHT_NOBITS and ((section.sh_flags & elf.SHF_ALLOC) == elf.SHF_ALLOC);
+    fn sectionValidForOutput(shdr: var) bool {
+        return shdr.sh_size > 0 and shdr.sh_type != elf.SHT_NOBITS and
+            ((shdr.sh_flags & elf.SHF_ALLOC) == elf.SHF_ALLOC);
     }
 
     fn segmentSortCompare(left: *BinaryElfSegment, right: *BinaryElfSegment) bool {
@@ -151,60 +148,27 @@ const BinaryElfOutput = struct {
     }
 };
 
-const WriteContext = struct {
-    inStream: *ElfInStream,
-    inSeekStream: *ElfSeekStream,
-    outStream: *BinOutStream,
-    outSeekStream: *BinSeekStream,
-};
-
-fn writeBinaryElfSection(allocator: *Allocator, context: WriteContext, section: *BinaryElfSection) !void {
-    var readBuffer = try allocator.alloc(u8, section.fileSize);
-    defer allocator.free(readBuffer);
+fn writeBinaryElfSection(elf_file: File, out_file: File, section: *BinaryElfSection) !void {
+    try out_file.seekTo(section.binaryOffset);
 
-    try context.inSeekStream.seekTo(section.elfOffset);
-    _ = try context.inStream.read(readBuffer);
-
-    try context.outSeekStream.seekTo(section.binaryOffset);
-    try context.outStream.write(readBuffer);
+    try out_file.writeFileAll(elf_file, .{
+        .in_offset = section.elfOffset,
+        .in_len = section.fileSize,
+    });
 }
 
-fn emit_raw(allocator: *Allocator, elf_path: []const u8, raw_path: []const u8) !void {
-    var arenaAlloc = ArenaAllocator.init(allocator);
-    errdefer arenaAlloc.deinit();
-    var arena_allocator = &arenaAlloc.allocator;
-
-    const currentDir = fs.cwd();
-
-    var file = try currentDir.openFile(elf_path, File.OpenFlags{});
-    defer file.close();
-
-    var fileInStream = file.inStream();
-    var fileSeekStream = file.seekableStream();
-
-    var elfFile = try elf.Elf.openStream(allocator, @ptrCast(*ElfSeekStream, &fileSeekStream.stream), @ptrCast(*ElfInStream, &fileInStream.stream));
-    defer elfFile.close();
-
-    var outFile = try currentDir.createFile(raw_path, File.CreateFlags{});
-    defer outFile.close();
-
-    var outFileOutStream = outFile.outStream();
-    var outFileSeekStream = outFile.seekableStream();
-
-    const writeContext = WriteContext{
-        .inStream = @ptrCast(*ElfInStream, &fileInStream.stream),
-        .inSeekStream = @ptrCast(*ElfSeekStream, &fileSeekStream.stream),
-        .outStream = @ptrCast(*BinOutStream, &outFileOutStream.stream),
-        .outSeekStream = @ptrCast(*BinSeekStream, &outFileSeekStream.stream),
-    };
+fn emitRaw(allocator: *Allocator, elf_path: []const u8, raw_path: []const u8) !void {
+    var elf_file = try fs.cwd().openFile(elf_path, .{});
+    defer elf_file.close();
 
-    var binaryElfOutput = BinaryElfOutput.init(arena_allocator);
-    defer binaryElfOutput.deinit();
+    var out_file = try fs.cwd().createFile(raw_path, .{});
+    defer out_file.close();
 
-    try binaryElfOutput.parseElf(elfFile);
+    const binary_elf_output = BinaryElfOutput.parse(allocator, elf_file);
+    defer binary_elf_output.deinit();
 
-    for (binaryElfOutput.sections.toSlice()) |section| {
-        try writeBinaryElfSection(allocator, writeContext, section);
+    for (binary_elf_output.sections.toSlice()) |section| {
+        try writeBinaryElfSection(elf_file, out_file, section);
     }
 }
 
@@ -250,6 +214,6 @@ pub const InstallRawStep = struct {
         const full_dest_path = builder.getInstallPath(self.dest_dir, self.dest_filename);
 
         fs.cwd().makePath(builder.getInstallPath(self.dest_dir, "")) catch unreachable;
-        try emit_raw(builder.allocator, full_src_path, full_dest_path);
+        try emitRaw(builder.allocator, full_src_path, full_dest_path);
     }
 };
lib/std/zig/system.zig
@@ -570,7 +570,7 @@ pub const NativeTargetInfo = struct {
         cross_target: CrossTarget,
     ) AbiAndDynamicLinkerFromFileError!NativeTargetInfo {
         var hdr_buf: [@sizeOf(elf.Elf64_Ehdr)]u8 align(@alignOf(elf.Elf64_Ehdr)) = undefined;
-        _ = try preadFull(file, &hdr_buf, 0, hdr_buf.len);
+        _ = try preadMin(file, &hdr_buf, 0, hdr_buf.len);
         const hdr32 = @ptrCast(*elf.Elf32_Ehdr, &hdr_buf);
         const hdr64 = @ptrCast(*elf.Elf64_Ehdr, &hdr_buf);
         if (!mem.eql(u8, hdr32.e_ident[0..4], "\x7fELF")) return error.InvalidElfMagic;
@@ -587,6 +587,7 @@ pub const NativeTargetInfo = struct {
             elf.ELFCLASS64 => true,
             else => return error.InvalidElfClass,
         };
+        const elfInt = elf.int;
         var phoff = elfInt(is_64, need_bswap, hdr32.e_phoff, hdr64.e_phoff);
         const phentsize = elfInt(is_64, need_bswap, hdr32.e_phentsize, hdr64.e_phentsize);
         const phnum = elfInt(is_64, need_bswap, hdr32.e_phnum, hdr64.e_phnum);
@@ -610,7 +611,7 @@ pub const NativeTargetInfo = struct {
             // Reserve some bytes so that we can deref the 64-bit struct fields
             // even when the ELF file is 32-bits.
             const ph_reserve: usize = @sizeOf(elf.Elf64_Phdr) - @sizeOf(elf.Elf32_Phdr);
-            const ph_read_byte_len = try preadFull(file, ph_buf[0 .. ph_buf.len - ph_reserve], phoff, phentsize);
+            const ph_read_byte_len = try preadMin(file, ph_buf[0 .. ph_buf.len - ph_reserve], phoff, phentsize);
             var ph_buf_i: usize = 0;
             while (ph_buf_i < ph_read_byte_len and ph_i < phnum) : ({
                 ph_i += 1;
@@ -625,7 +626,7 @@ pub const NativeTargetInfo = struct {
                         const p_offset = elfInt(is_64, need_bswap, ph32.p_offset, ph64.p_offset);
                         const p_filesz = elfInt(is_64, need_bswap, ph32.p_filesz, ph64.p_filesz);
                         if (p_filesz > result.dynamic_linker.buffer.len) return error.NameTooLong;
-                        _ = try preadFull(file, result.dynamic_linker.buffer[0..p_filesz], p_offset, p_filesz);
+                        _ = try preadMin(file, result.dynamic_linker.buffer[0..p_filesz], p_offset, p_filesz);
                         // PT_INTERP includes a null byte in p_filesz.
                         const len = p_filesz - 1;
                         // dynamic_linker.max_byte is "max", not "len".
@@ -656,7 +657,7 @@ pub const NativeTargetInfo = struct {
                             // Reserve some bytes so that we can deref the 64-bit struct fields
                             // even when the ELF file is 32-bits.
                             const dyn_reserve: usize = @sizeOf(elf.Elf64_Dyn) - @sizeOf(elf.Elf32_Dyn);
-                            const dyn_read_byte_len = try preadFull(
+                            const dyn_read_byte_len = try preadMin(
                                 file,
                                 dyn_buf[0 .. dyn_buf.len - dyn_reserve],
                                 dyn_off,
@@ -701,14 +702,14 @@ pub const NativeTargetInfo = struct {
                 var sh_buf: [16 * @sizeOf(elf.Elf64_Shdr)]u8 align(@alignOf(elf.Elf64_Shdr)) = undefined;
                 if (sh_buf.len < shentsize) return error.InvalidElfFile;
 
-                _ = try preadFull(file, &sh_buf, str_section_off, shentsize);
+                _ = try preadMin(file, &sh_buf, str_section_off, shentsize);
                 const shstr32 = @ptrCast(*elf.Elf32_Shdr, @alignCast(@alignOf(elf.Elf32_Shdr), &sh_buf));
                 const shstr64 = @ptrCast(*elf.Elf64_Shdr, @alignCast(@alignOf(elf.Elf64_Shdr), &sh_buf));
                 const shstrtab_off = elfInt(is_64, need_bswap, shstr32.sh_offset, shstr64.sh_offset);
                 const shstrtab_size = elfInt(is_64, need_bswap, shstr32.sh_size, shstr64.sh_size);
                 var strtab_buf: [4096:0]u8 = undefined;
                 const shstrtab_len = std.math.min(shstrtab_size, strtab_buf.len);
-                const shstrtab_read_len = try preadFull(file, &strtab_buf, shstrtab_off, shstrtab_len);
+                const shstrtab_read_len = try preadMin(file, &strtab_buf, shstrtab_off, shstrtab_len);
                 const shstrtab = strtab_buf[0..shstrtab_read_len];
 
                 const shnum = elfInt(is_64, need_bswap, hdr32.e_shnum, hdr64.e_shnum);
@@ -717,7 +718,7 @@ pub const NativeTargetInfo = struct {
                     // Reserve some bytes so that we can deref the 64-bit struct fields
                     // even when the ELF file is 32-bits.
                     const sh_reserve: usize = @sizeOf(elf.Elf64_Shdr) - @sizeOf(elf.Elf32_Shdr);
-                    const sh_read_byte_len = try preadFull(
+                    const sh_read_byte_len = try preadMin(
                         file,
                         sh_buf[0 .. sh_buf.len - sh_reserve],
                         shoff,
@@ -751,7 +752,7 @@ pub const NativeTargetInfo = struct {
 
                 if (dynstr) |ds| {
                     const strtab_len = std.math.min(ds.size, strtab_buf.len);
-                    const strtab_read_len = try preadFull(file, &strtab_buf, ds.offset, shstrtab_len);
+                    const strtab_read_len = try preadMin(file, &strtab_buf, ds.offset, shstrtab_len);
                     const strtab = strtab_buf[0..strtab_read_len];
                     // TODO this pointer cast should not be necessary
                     const rpath_list = mem.toSliceConst(u8, @ptrCast([*:0]u8, strtab[rpoff..].ptr));
@@ -813,7 +814,7 @@ pub const NativeTargetInfo = struct {
         return result;
     }
 
-    fn preadFull(file: fs.File, buf: []u8, offset: u64, min_read_len: usize) !usize {
+    fn preadMin(file: fs.File, buf: []u8, offset: u64, min_read_len: usize) !usize {
         var i: u64 = 0;
         while (i < min_read_len) {
             const len = file.pread(buf[i .. buf.len - i], offset + i) catch |err| switch (err) {
@@ -853,22 +854,6 @@ pub const NativeTargetInfo = struct {
         abi: Target.Abi,
     };
 
-    fn elfInt(is_64: bool, need_bswap: bool, int_32: var, int_64: var) @TypeOf(int_64) {
-        if (is_64) {
-            if (need_bswap) {
-                return @byteSwap(@TypeOf(int_64), int_64);
-            } else {
-                return int_64;
-            }
-        } else {
-            if (need_bswap) {
-                return @byteSwap(@TypeOf(int_32), int_32);
-            } else {
-                return int_32;
-            }
-        }
-    }
-
     fn detectNativeCpuAndFeatures(cpu_arch: Target.Cpu.Arch, os: Target.Os, cross_target: CrossTarget) ?Target.Cpu {
         // Here we switch on a comptime value rather than `cpu_arch`. This is valid because `cpu_arch`,
         // although it is a runtime value, is guaranteed to be one of the architectures in the set
lib/std/elf.zig
@@ -330,9 +330,7 @@ pub const ET = extern enum(u16) {
     pub const HIPROC = 0xffff;
 };
 
-pub const SectionHeader = Elf64_Shdr;
-pub const ProgramHeader = Elf64_Phdr;
-
+/// All integers are native endian.
 const Header = struct {
     endian: builtin.Endian,
     is_64: bool,
@@ -346,9 +344,9 @@ const Header = struct {
     shstrndx: u16,
 };
 
-pub fn readHeader(in_stream: var) !Header {
+pub fn readHeader(file: File) !Header {
     var hdr_buf: [@sizeOf(Elf64_Ehdr)]u8 align(@alignOf(Elf64_Ehdr)) = undefined;
-    try in_stream.readAll(&hdr_buf);
+    try in_stream.preadAll(&hdr_buf, 0);
     const hdr32 = @ptrCast(*elf.Elf32_Ehdr, &hdr_buf);
     const hdr64 = @ptrCast(*elf.Elf64_Ehdr, &hdr_buf);
     if (!mem.eql(u8, hdr32.e_ident[0..4], "\x7fELF")) return error.InvalidElfMagic;
@@ -381,215 +379,85 @@ pub fn readHeader(in_stream: var) !Header {
     });
 }
 
-pub const Elf = struct {
-    seekable_stream: *io.SeekableStream(anyerror, anyerror),
-    in_stream: *io.InStream(anyerror),
-    is_64: bool,
-    endian: builtin.Endian,
-    file_type: ET,
-    arch: EM,
-    entry_addr: u64,
-    program_header_offset: u64,
-    section_header_offset: u64,
-    string_section_index: usize,
-    string_section: *SectionHeader,
-    section_headers: []SectionHeader,
-    program_headers: []ProgramHeader,
+/// All integers are native endian.
+pub const AllHeaders = struct {
+    header: Header,
+    section_headers: []Elf64_Shdr,
+    program_headers: []Elf64_Phdr,
     allocator: *mem.Allocator,
+};
 
-    pub fn openStream(
-        allocator: *mem.Allocator,
-        seekable_stream: *io.SeekableStream(anyerror, anyerror),
-        in: *io.InStream(anyerror),
-    ) !Elf {
-        var elf: Elf = undefined;
-        elf.allocator = allocator;
-        elf.seekable_stream = seekable_stream;
-        elf.in_stream = in;
-
-        var magic: [4]u8 = undefined;
-        try in.readNoEof(magic[0..]);
-        if (!mem.eql(u8, &magic, "\x7fELF")) return error.InvalidFormat;
-
-        elf.is_64 = switch (try in.readByte()) {
-            1 => false,
-            2 => true,
-            else => return error.InvalidFormat,
+pub fn readAllHeaders(allocator: *mem.Allocator, file: File) !AllHeaders {
+    var hdrs: AllHeaders = .{
+        .allocator = allocator,
+        .header = try readHeader(file),
+        .section_headers = undefined,
+        .program_headers = undefined,
+    };
+    const is_64 = hdrs.header.is_64;
+    const need_bswap = hdrs.header.endian != std.builtin.endian;
+
+    hdrs.section_headers = try allocator.alloc(Elf64_Shdr, hdrs.header.shnum);
+    errdefer hdrs.allocator.free(hdrs.section_headers);
+
+    hdrs.program_headers = try allocator.alloc(Elf64_Phdr, hdrs.header.phnum);
+    errdefer hdrs.allocator.free(hdrs.program_headers);
+
+    // Treat section headers and program headers as byte buffers. For 32-bit ELF and
+    // non-matching endian files, we post-process to correct integer endianness and offsets.
+
+    const shdr_buf = std.mem.sliceToBytes(hdrs.section_headers)[0 .. hdrs.header.shentsize * hdrs.header.shnum];
+    const phdr_buf = std.mem.sliceToBytes(hdrs.section_headers)[0 .. hdrs.header.phentsize * hdrs.header.phnum];
+
+    try file.preadAll(phdr_buf, hdrs.header.phoff);
+    try file.preadAll(shdr_buf, hdrs.header.shoff);
+
+    const shdrs32 = @ptrCast([*]Elf32_Shdr, @alignCast(@alignOf(Elf32_Shdr), shdr_buf.ptr))[0..hdrs.header.shnum];
+    const phdrs32 = @ptrCast([*]Elf32_Phdr, @alignCast(@alignOf(Elf32_Phdr), phdr_buf.ptr))[0..hdrs.header.phnum];
+    for (hdrs.section_headers) |*shdr, i| {
+        shdr.* = .{
+            .sh_name = int(is_64, need_bswap, shdrs32[i].sh_name, shdr.sh_name),
+            .sh_type = int(is_64, need_bswap, shdrs32[i].sh_type, shdr.sh_type),
+            .sh_flags = int(is_64, need_bswap, shdrs32[i].sh_flags, shdr.sh_flags),
+            .sh_addr = int(is_64, need_bswap, shdrs32[i].sh_addr, shdr.sh_addr),
+            .sh_offset = int(is_64, need_bswap, shdrs32[i].sh_offset, shdr.sh_offset),
+            .sh_size = int(is_64, need_bswap, shdrs32[i].sh_size, shdr.sh_size),
+            .sh_link = int(is_64, need_bswap, shdrs32[i].sh_link, shdr.sh_link),
+            .sh_info = int(is_64, need_bswap, shdrs32[i].sh_info, shdr.sh_info),
+            .sh_addralign = int(is_64, need_bswap, shdrs32[i].sh_addralign, shdr.sh_addralign),
+            .sh_entsize = int(is_64, need_bswap, shdrs32[i].sh_entsize, shdr.sh_entsize),
         };
-
-        elf.endian = switch (try in.readByte()) {
-            1 => .Little,
-            2 => .Big,
-            else => return error.InvalidFormat,
+    }
+    for (hdrs.program_headers) |*phdr, i| {
+        phdr.* = .{
+            .p_type = int(is_64, need_bswap, phdrs32[i].p_type, shdr.p_type),
+            .p_offset = int(is_64, need_bswap, phdrs32[i].p_offset, shdr.p_offset),
+            .p_vaddr = int(is_64, need_bswap, phdrs32[i].p_vaddr, shdr.p_vaddr),
+            .p_paddr = int(is_64, need_bswap, phdrs32[i].p_paddr, shdr.p_paddr),
+            .p_filesz = int(is_64, need_bswap, phdrs32[i].p_filesz, shdr.p_filesz),
+            .p_memsz = int(is_64, need_bswap, phdrs32[i].p_memsz, shdr.p_memsz),
+            .p_flags = int(is_64, need_bswap, phdrs32[i].p_flags, shdr.p_flags),
+            .p_align = int(is_64, need_bswap, phdrs32[i].p_align, shdr.p_align),
         };
+    }
+    return hdrs;
+}
 
-        const version_byte = try in.readByte();
-        if (version_byte != 1) return error.InvalidFormat;
-
-        // skip over padding
-        try seekable_stream.seekBy(9);
-
-        elf.file_type = try in.readEnum(ET, elf.endian);
-        elf.arch = try in.readEnum(EM, elf.endian);
-
-        const elf_version = try in.readInt(u32, elf.endian);
-        if (elf_version != 1) return error.InvalidFormat;
-
-        if (elf.is_64) {
-            elf.entry_addr = try in.readInt(u64, elf.endian);
-            elf.program_header_offset = try in.readInt(u64, elf.endian);
-            elf.section_header_offset = try in.readInt(u64, elf.endian);
-        } else {
-            elf.entry_addr = @as(u64, try in.readInt(u32, elf.endian));
-            elf.program_header_offset = @as(u64, try in.readInt(u32, elf.endian));
-            elf.section_header_offset = @as(u64, try in.readInt(u32, elf.endian));
-        }
-
-        // skip over flags
-        try seekable_stream.seekBy(4);
-
-        const header_size = try in.readInt(u16, elf.endian);
-        if ((elf.is_64 and header_size != @sizeOf(Elf64_Ehdr)) or (!elf.is_64 and header_size != @sizeOf(Elf32_Ehdr))) {
-            return error.InvalidFormat;
-        }
-
-        const ph_entry_size = try in.readInt(u16, elf.endian);
-        const ph_entry_count = try in.readInt(u16, elf.endian);
-
-        if ((elf.is_64 and ph_entry_size != @sizeOf(Elf64_Phdr)) or (!elf.is_64 and ph_entry_size != @sizeOf(Elf32_Phdr))) {
-            return error.InvalidFormat;
-        }
-
-        const sh_entry_size = try in.readInt(u16, elf.endian);
-        const sh_entry_count = try in.readInt(u16, elf.endian);
-
-        if ((elf.is_64 and sh_entry_size != @sizeOf(Elf64_Shdr)) or (!elf.is_64 and sh_entry_size != @sizeOf(Elf32_Shdr))) {
-            return error.InvalidFormat;
-        }
-
-        elf.string_section_index = @as(usize, try in.readInt(u16, elf.endian));
-
-        if (elf.string_section_index >= sh_entry_count) return error.InvalidFormat;
-
-        const sh_byte_count = @as(u64, sh_entry_size) * @as(u64, sh_entry_count);
-        const end_sh = try math.add(u64, elf.section_header_offset, sh_byte_count);
-        const ph_byte_count = @as(u64, ph_entry_size) * @as(u64, ph_entry_count);
-        const end_ph = try math.add(u64, elf.program_header_offset, ph_byte_count);
-
-        const stream_end = try seekable_stream.getEndPos();
-        if (stream_end < end_sh or stream_end < end_ph) {
-            return error.InvalidFormat;
-        }
-
-        try seekable_stream.seekTo(elf.program_header_offset);
-
-        elf.program_headers = try elf.allocator.alloc(ProgramHeader, ph_entry_count);
-        errdefer elf.allocator.free(elf.program_headers);
-
-        if (elf.is_64) {
-            for (elf.program_headers) |*elf_program| {
-                elf_program.p_type = try in.readInt(Elf64_Word, elf.endian);
-                elf_program.p_flags = try in.readInt(Elf64_Word, elf.endian);
-                elf_program.p_offset = try in.readInt(Elf64_Off, elf.endian);
-                elf_program.p_vaddr = try in.readInt(Elf64_Addr, elf.endian);
-                elf_program.p_paddr = try in.readInt(Elf64_Addr, elf.endian);
-                elf_program.p_filesz = try in.readInt(Elf64_Xword, elf.endian);
-                elf_program.p_memsz = try in.readInt(Elf64_Xword, elf.endian);
-                elf_program.p_align = try in.readInt(Elf64_Xword, elf.endian);
-            }
+pub fn int(is_64: bool, need_bswap: bool, int_32: var, int_64: var) @TypeOf(int_64) {
+    if (is_64) {
+        if (need_bswap) {
+            return @byteSwap(@TypeOf(int_64), int_64);
         } else {
-            for (elf.program_headers) |*elf_program| {
-                elf_program.p_type = @as(Elf64_Word, try in.readInt(Elf32_Word, elf.endian));
-                elf_program.p_offset = @as(Elf64_Off, try in.readInt(Elf32_Off, elf.endian));
-                elf_program.p_vaddr = @as(Elf64_Addr, try in.readInt(Elf32_Addr, elf.endian));
-                elf_program.p_paddr = @as(Elf64_Addr, try in.readInt(Elf32_Addr, elf.endian));
-                elf_program.p_filesz = @as(Elf64_Word, try in.readInt(Elf32_Word, elf.endian));
-                elf_program.p_memsz = @as(Elf64_Word, try in.readInt(Elf32_Word, elf.endian));
-                elf_program.p_flags = @as(Elf64_Word, try in.readInt(Elf32_Word, elf.endian));
-                elf_program.p_align = @as(Elf64_Word, try in.readInt(Elf32_Word, elf.endian));
-            }
+            return int_64;
         }
-
-        try seekable_stream.seekTo(elf.section_header_offset);
-
-        elf.section_headers = try elf.allocator.alloc(SectionHeader, sh_entry_count);
-        errdefer elf.allocator.free(elf.section_headers);
-
-        if (elf.is_64) {
-            for (elf.section_headers) |*elf_section| {
-                elf_section.sh_name = try in.readInt(u32, elf.endian);
-                elf_section.sh_type = try in.readInt(u32, elf.endian);
-                elf_section.sh_flags = try in.readInt(u64, elf.endian);
-                elf_section.sh_addr = try in.readInt(u64, elf.endian);
-                elf_section.sh_offset = try in.readInt(u64, elf.endian);
-                elf_section.sh_size = try in.readInt(u64, elf.endian);
-                elf_section.sh_link = try in.readInt(u32, elf.endian);
-                elf_section.sh_info = try in.readInt(u32, elf.endian);
-                elf_section.sh_addralign = try in.readInt(u64, elf.endian);
-                elf_section.sh_entsize = try in.readInt(u64, elf.endian);
-            }
+    } else {
+        if (need_bswap) {
+            return @byteSwap(@TypeOf(int_32), int_32);
         } else {
-            for (elf.section_headers) |*elf_section| {
-                // TODO (multiple occurrences) allow implicit cast from %u32 -> %u64 ?
-                elf_section.sh_name = try in.readInt(u32, elf.endian);
-                elf_section.sh_type = try in.readInt(u32, elf.endian);
-                elf_section.sh_flags = @as(u64, try in.readInt(u32, elf.endian));
-                elf_section.sh_addr = @as(u64, try in.readInt(u32, elf.endian));
-                elf_section.sh_offset = @as(u64, try in.readInt(u32, elf.endian));
-                elf_section.sh_size = @as(u64, try in.readInt(u32, elf.endian));
-                elf_section.sh_link = try in.readInt(u32, elf.endian);
-                elf_section.sh_info = try in.readInt(u32, elf.endian);
-                elf_section.sh_addralign = @as(u64, try in.readInt(u32, elf.endian));
-                elf_section.sh_entsize = @as(u64, try in.readInt(u32, elf.endian));
-            }
-        }
-
-        for (elf.section_headers) |*elf_section| {
-            if (elf_section.sh_type != SHT_NOBITS) {
-                const file_end_offset = try math.add(u64, elf_section.sh_offset, elf_section.sh_size);
-                if (stream_end < file_end_offset) return error.InvalidFormat;
-            }
-        }
-
-        elf.string_section = &elf.section_headers[elf.string_section_index];
-        if (elf.string_section.sh_type != SHT_STRTAB) {
-            // not a string table
-            return error.InvalidFormat;
-        }
-
-        return elf;
-    }
-
-    pub fn close(elf: *Elf) void {
-        elf.allocator.free(elf.section_headers);
-        elf.allocator.free(elf.program_headers);
-    }
-
-    pub fn findSection(elf: *Elf, name: []const u8) !?*SectionHeader {
-        section_loop: for (elf.section_headers) |*elf_section| {
-            if (elf_section.sh_type == SHT_NULL) continue;
-
-            const name_offset = elf.string_section.sh_offset + elf_section.sh_name;
-            try elf.seekable_stream.seekTo(name_offset);
-
-            for (name) |expected_c| {
-                const target_c = try elf.in_stream.readByte();
-                if (target_c == 0 or expected_c != target_c) continue :section_loop;
-            }
-
-            {
-                const null_byte = try elf.in_stream.readByte();
-                if (null_byte == 0) return elf_section;
-            }
+            return int_32;
         }
-
-        return null;
-    }
-
-    pub fn seekToSection(elf: *Elf, elf_section: *SectionHeader) !void {
-        try elf.seekable_stream.seekTo(elf_section.sh_offset);
     }
-};
+}
 
 pub const EI_NIDENT = 16;