zig/std/elf.zig
Andrew Kelley 6dba1f1c8e slice and array re-work plus some misc. changes
* `@truncate` builtin allows casting to the same size integer.
   It also performs two's complement casting between signed and
   unsigned integers.
 * The idiomatic way to convert between bytes and numbers is now
   `mem.readInt` and `mem.writeInt` instead of an unsafe cast.
   It works at compile time, is safer, and looks cleaner.
 * Implicitly casting an array to a slice is allowed only if the
   slice is const.
 * Constant pointer values know if their memory is from a compile-
   time constant value or a compile-time variable.
 * Cast from [N]u8 to []T no longer allowed, but [N]u8 to []const T
   still allowed.
 * Fix inability to pass a mutable pointer to comptime variable at
   compile-time to a function and have the function modify the
   memory pointed to by the pointer.
 * Add the `comptime T: type` parameter back to mem.eql. Prevents
   accidentally creating instantiations for arrays.
2017-02-12 17:35:51 -05:00

267 lines
9.7 KiB
Zig

const io = @import("io.zig");
const math = @import("math.zig");
const mem = @import("mem.zig");
const debug = @import("debug.zig");
error InvalidFormat;
pub const SHT_NULL = 0;
pub const SHT_PROGBITS = 1;
pub const SHT_SYMTAB = 2;
pub const SHT_STRTAB = 3;
pub const SHT_RELA = 4;
pub const SHT_HASH = 5;
pub const SHT_DYNAMIC = 6;
pub const SHT_NOTE = 7;
pub const SHT_NOBITS = 8;
pub const SHT_REL = 9;
pub const SHT_SHLIB = 10;
pub const SHT_DYNSYM = 11;
pub const SHT_INIT_ARRAY = 14;
pub const SHT_FINI_ARRAY = 15;
pub const SHT_PREINIT_ARRAY = 16;
pub const SHT_GROUP = 17;
pub const SHT_SYMTAB_SHNDX = 18;
pub const SHT_LOOS = 0x60000000;
pub const SHT_HIOS = 0x6fffffff;
pub const SHT_LOPROC = 0x70000000;
pub const SHT_HIPROC = 0x7fffffff;
pub const SHT_LOUSER = 0x80000000;
pub const SHT_HIUSER = 0xffffffff;
pub const FileType = enum {
Relocatable,
Executable,
Shared,
Core,
};
// TODO rename this to Arch when the builtin Arch enum is namespaced
// or make debug info work for builtin enums
pub const ElfArch = enum {
Sparc,
x86,
Mips,
PowerPc,
Arm,
SuperH,
IA_64,
x86_64,
AArch64,
};
pub const SectionHeader = struct {
name: u32,
sh_type: u32,
flags: u64,
addr: u64,
offset: u64,
size: u64,
link: u32,
info: u32,
addr_align: u64,
ent_size: u64,
};
pub const Elf = struct {
in_stream: &io.InStream,
auto_close_stream: bool,
is_64: bool,
is_big_endian: bool,
file_type: FileType,
arch: ElfArch,
entry_addr: u64,
program_header_offset: u64,
section_header_offset: u64,
string_section_index: u64,
string_section: &SectionHeader,
section_headers: []SectionHeader,
allocator: &mem.Allocator,
prealloc_stream: io.InStream,
/// Call close when done.
pub fn openFile(elf: &Elf, allocator: &mem.Allocator, path: []const u8) -> %void {
%return elf.prealloc_stream.open(path);
%return elf.openStream(allocator, &elf.prealloc_stream);
elf.auto_close_stream = true;
}
/// Call close when done.
pub fn openStream(elf: &Elf, allocator: &mem.Allocator, stream: &io.InStream) -> %void {
elf.allocator = allocator;
elf.in_stream = stream;
elf.auto_close_stream = false;
var magic: [4]u8 = undefined;
%return elf.in_stream.readNoEof(magic[0...]);
if (!mem.eql(u8, magic, "\x7fELF")) return error.InvalidFormat;
elf.is_64 = switch (%return elf.in_stream.readByte()) {
1 => false,
2 => true,
else => return error.InvalidFormat,
};
elf.is_big_endian = switch (%return elf.in_stream.readByte()) {
1 => false,
2 => true,
else => return error.InvalidFormat,
};
const version_byte = %return elf.in_stream.readByte();
if (version_byte != 1) return error.InvalidFormat;
// skip over padding
%return elf.in_stream.seekForward(9);
elf.file_type = switch (%return elf.in_stream.readInt(elf.is_big_endian, u16)) {
1 => FileType.Relocatable,
2 => FileType.Executable,
3 => FileType.Shared,
4 => FileType.Core,
else => return error.InvalidFormat,
};
elf.arch = switch (%return elf.in_stream.readInt(elf.is_big_endian, u16)) {
0x02 => ElfArch.Sparc,
0x03 => ElfArch.x86,
0x08 => ElfArch.Mips,
0x14 => ElfArch.PowerPc,
0x28 => ElfArch.Arm,
0x2A => ElfArch.SuperH,
0x32 => ElfArch.IA_64,
0x3E => ElfArch.x86_64,
0xb7 => ElfArch.AArch64,
else => return error.InvalidFormat,
};
const elf_version = %return elf.in_stream.readInt(elf.is_big_endian, u32);
if (elf_version != 1) return error.InvalidFormat;
if (elf.is_64) {
elf.entry_addr = %return elf.in_stream.readInt(elf.is_big_endian, u64);
elf.program_header_offset = %return elf.in_stream.readInt(elf.is_big_endian, u64);
elf.section_header_offset = %return elf.in_stream.readInt(elf.is_big_endian, u64);
} else {
elf.entry_addr = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
elf.program_header_offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
elf.section_header_offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
}
// skip over flags
%return elf.in_stream.seekForward(4);
const header_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
if ((elf.is_64 && header_size != 64) ||
(!elf.is_64 && header_size != 52))
{
return error.InvalidFormat;
}
const ph_entry_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
const ph_entry_count = %return elf.in_stream.readInt(elf.is_big_endian, u16);
const sh_entry_size = %return elf.in_stream.readInt(elf.is_big_endian, u16);
const sh_entry_count = %return elf.in_stream.readInt(elf.is_big_endian, u16);
elf.string_section_index = u64(%return elf.in_stream.readInt(elf.is_big_endian, u16));
if (elf.string_section_index >= sh_entry_count) return error.InvalidFormat;
const sh_byte_count = u64(sh_entry_size) * u64(sh_entry_count);
const end_sh = %return math.addOverflow(u64, elf.section_header_offset, sh_byte_count);
const ph_byte_count = u64(ph_entry_size) * u64(ph_entry_count);
const end_ph = %return math.addOverflow(u64, elf.program_header_offset, ph_byte_count);
const stream_end = %return elf.in_stream.getEndPos();
if (stream_end < end_sh || stream_end < end_ph) {
return error.InvalidFormat;
}
%return elf.in_stream.seekTo(elf.section_header_offset);
elf.section_headers = %return elf.allocator.alloc(SectionHeader, sh_entry_count);
%defer elf.allocator.free(elf.section_headers);
if (elf.is_64) {
if (sh_entry_size != 64) return error.InvalidFormat;
for (elf.section_headers) |*section| {
section.name = %return elf.in_stream.readInt(elf.is_big_endian, u32);
section.sh_type = %return elf.in_stream.readInt(elf.is_big_endian, u32);
section.flags = %return elf.in_stream.readInt(elf.is_big_endian, u64);
section.addr = %return elf.in_stream.readInt(elf.is_big_endian, u64);
section.offset = %return elf.in_stream.readInt(elf.is_big_endian, u64);
section.size = %return elf.in_stream.readInt(elf.is_big_endian, u64);
section.link = %return elf.in_stream.readInt(elf.is_big_endian, u32);
section.info = %return elf.in_stream.readInt(elf.is_big_endian, u32);
section.addr_align = %return elf.in_stream.readInt(elf.is_big_endian, u64);
section.ent_size = %return elf.in_stream.readInt(elf.is_big_endian, u64);
}
} else {
if (sh_entry_size != 40) return error.InvalidFormat;
for (elf.section_headers) |*section| {
// TODO (multiple occurences) allow implicit cast from %u32 -> %u64 ?
section.name = %return elf.in_stream.readInt(elf.is_big_endian, u32);
section.sh_type = %return elf.in_stream.readInt(elf.is_big_endian, u32);
section.flags = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
section.addr = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
section.offset = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
section.size = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
section.link = %return elf.in_stream.readInt(elf.is_big_endian, u32);
section.info = %return elf.in_stream.readInt(elf.is_big_endian, u32);
section.addr_align = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
section.ent_size = u64(%return elf.in_stream.readInt(elf.is_big_endian, u32));
}
}
for (elf.section_headers) |*section| {
if (section.sh_type != SHT_NOBITS) {
const file_end_offset = %return math.addOverflow(u64,
section.offset, section.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;
}
}
pub fn close(elf: &Elf) {
elf.allocator.free(elf.section_headers);
if (elf.auto_close_stream)
elf.in_stream.close();
}
pub fn findSection(elf: &Elf, name: []const u8) -> %?&SectionHeader {
for (elf.section_headers) |*section| {
if (section.sh_type == SHT_NULL) continue;
const name_offset = elf.string_section.offset + section.name;
%return elf.in_stream.seekTo(name_offset);
for (name) |expected_c| {
const target_c = %return elf.in_stream.readByte();
if (target_c == 0 || expected_c != target_c) goto next_section;
}
{
const null_byte = %return elf.in_stream.readByte();
if (null_byte == 0) return (?&SectionHeader)(section);
}
next_section:
}
const null_sh: ?&SectionHeader = null;
return null_sh;
}
pub fn seekToSection(elf: &Elf, section: &SectionHeader) -> %void {
%return elf.in_stream.seekTo(section.offset);
}
};