zig/lib/std/dynamic_library.zig
Andrew Kelley 7de138ad7c
std.elf: breaking improvements to the API
and also integration with std.Target.Arch
2019-11-26 14:25:35 -05:00

281 lines
8.8 KiB
Zig

const builtin = @import("builtin");
const std = @import("std.zig");
const mem = std.mem;
const os = std.os;
const assert = std.debug.assert;
const testing = std.testing;
const elf = std.elf;
const windows = std.os.windows;
const maxInt = std.math.maxInt;
pub const DynLib = switch (builtin.os) {
.linux => LinuxDynLib,
.windows => WindowsDynLib,
else => void,
};
// The link_map structure is not completely specified beside the fields
// reported below, any libc is free to store additional data in the remaining
// space.
// An iterator is provided in order to traverse the linked list in a idiomatic
// fashion.
const LinkMap = extern struct {
l_addr: usize,
l_name: [*]const u8,
l_ld: ?*elf.Dyn,
l_next: ?*LinkMap,
l_prev: ?*LinkMap,
pub const Iterator = struct {
current: ?*LinkMap,
fn end(self: *Iterator) bool {
return self.current == null;
}
fn next(self: *Iterator) ?*LinkMap {
if (self.current) |it| {
self.current = it.l_next;
return it;
}
return null;
}
};
};
const RDebug = extern struct {
r_version: i32,
r_map: ?*LinkMap,
r_brk: usize,
r_ldbase: usize,
};
fn elf_get_va_offset(phdrs: []elf.Phdr) !usize {
for (phdrs) |*phdr| {
if (phdr.p_type == elf.PT_LOAD) {
return @ptrToInt(phdr) - phdr.p_vaddr;
}
}
return error.InvalidExe;
}
pub fn linkmap_iterator(phdrs: []elf.Phdr) !LinkMap.Iterator {
const va_offset = try elf_get_va_offset(phdrs);
const dyn_table = init: {
for (phdrs) |*phdr| {
if (phdr.p_type == elf.PT_DYNAMIC) {
const ptr = @intToPtr([*]elf.Dyn, va_offset + phdr.p_vaddr);
break :init ptr[0 .. phdr.p_memsz / @sizeOf(elf.Dyn)];
}
}
// No PT_DYNAMIC means this is either a statically-linked program or a
// badly corrupted one
return LinkMap.Iterator{ .current = null };
};
const link_map_ptr = init: {
for (dyn_table) |*dyn| {
switch (dyn.d_tag) {
elf.DT_DEBUG => {
const r_debug = @intToPtr(*RDebug, dyn.d_un.d_ptr);
if (r_debug.r_version != 1) return error.InvalidExe;
break :init r_debug.r_map;
},
elf.DT_PLTGOT => {
const got_table = @intToPtr([*]usize, dyn.d_un.d_ptr);
// The address to the link_map structure is stored in the
// second slot
break :init @intToPtr(?*LinkMap, got_table[1]);
},
else => {},
}
}
return error.InvalidExe;
};
return LinkMap.Iterator{ .current = link_map_ptr };
}
pub const LinuxDynLib = struct {
elf_lib: ElfLib,
fd: i32,
memory: []align(mem.page_size) u8,
/// Trusts the file
pub fn open(path: []const u8) !DynLib {
const fd = try os.open(path, 0, os.O_RDONLY | os.O_CLOEXEC);
errdefer os.close(fd);
// TODO remove this @intCast
const size = @intCast(usize, (try os.fstat(fd)).size);
const bytes = try os.mmap(
null,
mem.alignForward(size, mem.page_size),
os.PROT_READ | os.PROT_EXEC,
os.MAP_PRIVATE,
fd,
0,
);
errdefer os.munmap(bytes);
return DynLib{
.elf_lib = try ElfLib.init(bytes),
.fd = fd,
.memory = bytes,
};
}
pub fn close(self: *DynLib) void {
os.munmap(self.memory);
os.close(self.fd);
self.* = undefined;
}
pub fn lookup(self: *DynLib, name: []const u8) ?usize {
return self.elf_lib.lookup("", name);
}
};
pub const ElfLib = struct {
strings: [*:0]u8,
syms: [*]elf.Sym,
hashtab: [*]os.Elf_Symndx,
versym: ?[*]u16,
verdef: ?*elf.Verdef,
base: usize,
// Trusts the memory
pub fn init(bytes: []align(@alignOf(elf.Ehdr)) u8) !ElfLib {
const eh = @ptrCast(*elf.Ehdr, bytes.ptr);
if (!mem.eql(u8, eh.e_ident[0..4], "\x7fELF")) return error.NotElfFile;
if (eh.e_type != elf.ET.DYN) return error.NotDynamicLibrary;
const elf_addr = @ptrToInt(bytes.ptr);
var ph_addr: usize = elf_addr + eh.e_phoff;
var base: usize = maxInt(usize);
var maybe_dynv: ?[*]usize = null;
{
var i: usize = 0;
while (i < eh.e_phnum) : ({
i += 1;
ph_addr += eh.e_phentsize;
}) {
const ph = @intToPtr(*elf.Phdr, ph_addr);
switch (ph.p_type) {
elf.PT_LOAD => base = elf_addr + ph.p_offset - ph.p_vaddr,
elf.PT_DYNAMIC => maybe_dynv = @intToPtr([*]usize, elf_addr + ph.p_offset),
else => {},
}
}
}
const dynv = maybe_dynv orelse return error.MissingDynamicLinkingInformation;
if (base == maxInt(usize)) return error.BaseNotFound;
var maybe_strings: ?[*:0]u8 = null;
var maybe_syms: ?[*]elf.Sym = null;
var maybe_hashtab: ?[*]os.Elf_Symndx = null;
var maybe_versym: ?[*]u16 = null;
var maybe_verdef: ?*elf.Verdef = null;
{
var i: usize = 0;
while (dynv[i] != 0) : (i += 2) {
const p = base + dynv[i + 1];
switch (dynv[i]) {
elf.DT_STRTAB => maybe_strings = @intToPtr([*:0]u8, p),
elf.DT_SYMTAB => maybe_syms = @intToPtr([*]elf.Sym, p),
elf.DT_HASH => maybe_hashtab = @intToPtr([*]os.Elf_Symndx, p),
elf.DT_VERSYM => maybe_versym = @intToPtr([*]u16, p),
elf.DT_VERDEF => maybe_verdef = @intToPtr(*elf.Verdef, p),
else => {},
}
}
}
return ElfLib{
.base = base,
.strings = maybe_strings orelse return error.ElfStringSectionNotFound,
.syms = maybe_syms orelse return error.ElfSymSectionNotFound,
.hashtab = maybe_hashtab orelse return error.ElfHashTableNotFound,
.versym = maybe_versym,
.verdef = maybe_verdef,
};
}
/// Returns the address of the symbol
pub fn lookup(self: *const ElfLib, vername: []const u8, name: []const u8) ?usize {
const maybe_versym = if (self.verdef == null) null else self.versym;
const OK_TYPES = (1 << elf.STT_NOTYPE | 1 << elf.STT_OBJECT | 1 << elf.STT_FUNC | 1 << elf.STT_COMMON);
const OK_BINDS = (1 << elf.STB_GLOBAL | 1 << elf.STB_WEAK | 1 << elf.STB_GNU_UNIQUE);
var i: usize = 0;
while (i < self.hashtab[1]) : (i += 1) {
if (0 == (@as(u32, 1) << @intCast(u5, self.syms[i].st_info & 0xf) & OK_TYPES)) continue;
if (0 == (@as(u32, 1) << @intCast(u5, self.syms[i].st_info >> 4) & OK_BINDS)) continue;
if (0 == self.syms[i].st_shndx) continue;
if (!mem.eql(u8, name, mem.toSliceConst(u8, self.strings + self.syms[i].st_name))) continue;
if (maybe_versym) |versym| {
if (!checkver(self.verdef.?, versym[i], vername, self.strings))
continue;
}
return self.base + self.syms[i].st_value;
}
return null;
}
};
fn checkver(def_arg: *elf.Verdef, vsym_arg: i32, vername: []const u8, strings: [*:0]u8) bool {
var def = def_arg;
const vsym = @bitCast(u32, vsym_arg) & 0x7fff;
while (true) {
if (0 == (def.vd_flags & elf.VER_FLG_BASE) and (def.vd_ndx & 0x7fff) == vsym)
break;
if (def.vd_next == 0)
return false;
def = @intToPtr(*elf.Verdef, @ptrToInt(def) + def.vd_next);
}
const aux = @intToPtr(*elf.Verdaux, @ptrToInt(def) + def.vd_aux);
return mem.eql(u8, vername, mem.toSliceConst(u8, strings + aux.vda_name));
}
pub const WindowsDynLib = struct {
dll: windows.HMODULE,
pub fn open(path: []const u8) !WindowsDynLib {
const wpath = try windows.sliceToPrefixedFileW(path);
return WindowsDynLib{
.dll = try windows.LoadLibraryW(&wpath),
};
}
pub fn close(self: *WindowsDynLib) void {
windows.FreeLibrary(self.dll);
self.* = undefined;
}
pub fn lookup(self: *WindowsDynLib, name: []const u8) ?usize {
return @ptrToInt(windows.kernel32.GetProcAddress(self.dll, name.ptr));
}
};
test "dynamic_library" {
const libname = switch (builtin.os) {
.linux => "invalid_so.so",
.windows => "invalid_dll.dll",
else => return,
};
const dynlib = DynLib.open(libname) catch |err| {
testing.expect(err == error.FileNotFound);
return;
};
@panic("Expected error from function");
}