92 lines
3.4 KiB
Zig
92 lines
3.4 KiB
Zig
const std = @import("../../std.zig");
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const elf = std.elf;
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const linux = std.os.linux;
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const mem = std.mem;
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const maxInt = std.math.maxInt;
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pub fn lookup(vername: []const u8, name: []const u8) usize {
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const vdso_addr = std.os.system.getauxval(std.elf.AT_SYSINFO_EHDR);
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if (vdso_addr == 0) return 0;
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const eh = @intToPtr(*elf.Ehdr, vdso_addr);
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var ph_addr: usize = vdso_addr + eh.e_phoff;
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const ph = @intToPtr(*elf.Phdr, ph_addr);
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var maybe_dynv: ?[*]usize = null;
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var base: usize = maxInt(usize);
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{
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var i: usize = 0;
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while (i < eh.e_phnum) : ({
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i += 1;
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ph_addr += eh.e_phentsize;
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}) {
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const this_ph = @intToPtr(*elf.Phdr, ph_addr);
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switch (this_ph.p_type) {
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elf.PT_LOAD => base = vdso_addr + this_ph.p_offset - this_ph.p_vaddr,
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elf.PT_DYNAMIC => maybe_dynv = @intToPtr([*]usize, vdso_addr + this_ph.p_offset),
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else => {},
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}
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}
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}
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const dynv = maybe_dynv orelse return 0;
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if (base == maxInt(usize)) return 0;
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var maybe_strings: ?[*]u8 = null;
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var maybe_syms: ?[*]elf.Sym = null;
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var maybe_hashtab: ?[*]linux.Elf_Symndx = null;
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var maybe_versym: ?[*]u16 = null;
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var maybe_verdef: ?*elf.Verdef = null;
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{
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var i: usize = 0;
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while (dynv[i] != 0) : (i += 2) {
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const p = base + dynv[i + 1];
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switch (dynv[i]) {
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elf.DT_STRTAB => maybe_strings = @intToPtr([*]u8, p),
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elf.DT_SYMTAB => maybe_syms = @intToPtr([*]elf.Sym, p),
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elf.DT_HASH => maybe_hashtab = @intToPtr([*]linux.Elf_Symndx, p),
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elf.DT_VERSYM => maybe_versym = @intToPtr([*]u16, p),
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elf.DT_VERDEF => maybe_verdef = @intToPtr(*elf.Verdef, p),
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else => {},
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}
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}
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}
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const strings = maybe_strings orelse return 0;
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const syms = maybe_syms orelse return 0;
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const hashtab = maybe_hashtab orelse return 0;
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if (maybe_verdef == null) maybe_versym = null;
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const OK_TYPES = (1 << elf.STT_NOTYPE | 1 << elf.STT_OBJECT | 1 << elf.STT_FUNC | 1 << elf.STT_COMMON);
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const OK_BINDS = (1 << elf.STB_GLOBAL | 1 << elf.STB_WEAK | 1 << elf.STB_GNU_UNIQUE);
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var i: usize = 0;
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while (i < hashtab[1]) : (i += 1) {
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if (0 == (u32(1) << @intCast(u5, syms[i].st_info & 0xf) & OK_TYPES)) continue;
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if (0 == (u32(1) << @intCast(u5, syms[i].st_info >> 4) & OK_BINDS)) continue;
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if (0 == syms[i].st_shndx) continue;
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if (!mem.eql(u8, name, mem.toSliceConst(u8, strings + syms[i].st_name))) continue;
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if (maybe_versym) |versym| {
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if (!checkver(maybe_verdef.?, versym[i], vername, strings))
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continue;
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}
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return base + syms[i].st_value;
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}
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return 0;
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}
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fn checkver(def_arg: *elf.Verdef, vsym_arg: i32, vername: []const u8, strings: [*]u8) bool {
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var def = def_arg;
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const vsym = @bitCast(u32, vsym_arg) & 0x7fff;
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while (true) {
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if (0 == (def.vd_flags & elf.VER_FLG_BASE) and (def.vd_ndx & 0x7fff) == vsym)
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break;
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if (def.vd_next == 0)
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return false;
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def = @intToPtr(*elf.Verdef, @ptrToInt(def) + def.vd_next);
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}
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const aux = @intToPtr(*elf.Verdaux, @ptrToInt(def) + def.vd_aux);
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return mem.eql(u8, vername, mem.toSliceConst(u8, strings + aux.vda_name));
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}
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