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const std = @import("index.zig");
const mem = std.mem;
const elf = std.elf;
const cstr = std.cstr;
const linux = std.os.linux;
pub const DynLib = struct {
allocator: *mem.Allocator,
elf_lib: ElfLib,
fd: i32,
map_addr: usize,
map_size: usize,
/// Trusts the file
pub fn open(allocator: *mem.Allocator, path: []const u8) !DynLib {
const fd = try std.os.posixOpen(allocator, path, 0, linux.O_RDONLY | linux.O_CLOEXEC);
errdefer std.os.close(fd);
const size = @intCast(usize, (try std.os.posixFStat(fd)).size);
const addr = linux.mmap(
null,
size,
linux.PROT_READ | linux.PROT_EXEC,
linux.MAP_PRIVATE | linux.MAP_LOCKED,
fd,
0,
);
errdefer _ = linux.munmap(addr, size);
const bytes = @intToPtr([*]align(std.os.page_size) u8, addr)[0..size];
return DynLib{
.allocator = allocator,
.elf_lib = try ElfLib.init(bytes),
.fd = fd,
.map_addr = addr,
.map_size = size,
};
}
pub fn close(self: *DynLib) void {
_ = linux.munmap(self.map_addr, self.map_size);
std.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: [*]u8,
syms: [*]elf.Sym,
hashtab: [*]linux.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 = @maxValue(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 == @maxValue(usize)) return error.BaseNotFound;
var maybe_strings: ?[*]u8 = null;
var maybe_syms: ?[*]elf.Sym = null;
var maybe_hashtab: ?[*]linux.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([*]u8, p),
elf.DT_SYMTAB => maybe_syms = @intToPtr([*]elf.Sym, p),
elf.DT_HASH => maybe_hashtab = @intToPtr([*]linux.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 == (u32(1) << @intCast(u5, self.syms[i].st_info & 0xf) & OK_TYPES)) continue;
if (0 == (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, cstr.toSliceConst(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: [*]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, cstr.toSliceConst(strings + aux.vda_name));
}
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