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| 1 | +const std = @import("index.zig"); |
| 2 | +const mem = std.mem; |
| 3 | +const elf = std.elf; |
| 4 | +const cstr = std.cstr; |
| 5 | +const linux = std.os.linux; |
| 6 | + |
| 7 | +pub const DynLib = struct { |
| 8 | + allocator: *mem.Allocator, |
| 9 | + elf_lib: ElfLib, |
| 10 | + fd: i32, |
| 11 | + map_addr: usize, |
| 12 | + map_size: usize, |
| 13 | + |
| 14 | + /// Trusts the file |
| 15 | + pub fn findAndOpen(allocator: *mem.Allocator, name: []const u8) !DynLib { |
| 16 | + return open(allocator, name); |
| 17 | + } |
| 18 | + |
| 19 | + /// Trusts the file |
| 20 | + pub fn open(allocator: *mem.Allocator, path: []const u8) !DynLib { |
| 21 | + const fd = try std.os.posixOpen(allocator, path, 0, linux.O_RDONLY); |
| 22 | + errdefer std.os.close(fd); |
| 23 | + |
| 24 | + const size = usize((try std.os.posixFStat(fd)).size); |
| 25 | + |
| 26 | + const addr = linux.mmap( |
| 27 | + null, |
| 28 | + size, |
| 29 | + linux.PROT_READ | linux.PROT_EXEC, |
| 30 | + linux.MAP_PRIVATE | linux.MAP_LOCKED, |
| 31 | + fd, |
| 32 | + 0, |
| 33 | + ); |
| 34 | + errdefer _ = linux.munmap(addr, size); |
| 35 | + |
| 36 | + const bytes = @intToPtr([*]align(std.os.page_size) u8, addr)[0..size]; |
| 37 | + |
| 38 | + return DynLib{ |
| 39 | + .allocator = allocator, |
| 40 | + .elf_lib = try ElfLib.init(bytes), |
| 41 | + .fd = fd, |
| 42 | + .map_addr = addr, |
| 43 | + .map_size = size, |
| 44 | + }; |
| 45 | + } |
| 46 | + |
| 47 | + pub fn close(self: *DynLib) void { |
| 48 | + _ = linux.munmap(self.map_addr, self.map_size); |
| 49 | + std.os.close(self.fd); |
| 50 | + self.* = undefined; |
| 51 | + } |
| 52 | + |
| 53 | + pub fn lookup(self: *DynLib, name: []const u8) ?usize { |
| 54 | + return self.elf_lib.lookup("", name); |
| 55 | + } |
| 56 | +}; |
| 57 | + |
| 58 | +pub const ElfLib = struct { |
| 59 | + strings: [*]u8, |
| 60 | + syms: [*]elf.Sym, |
| 61 | + hashtab: [*]linux.Elf_Symndx, |
| 62 | + versym: ?[*]u16, |
| 63 | + verdef: ?*elf.Verdef, |
| 64 | + base: usize, |
| 65 | + |
| 66 | + // Trusts the memory |
| 67 | + pub fn init(bytes: []align(@alignOf(elf.Ehdr)) u8) !ElfLib { |
| 68 | + const eh = @ptrCast(*elf.Ehdr, bytes.ptr); |
| 69 | + if (!mem.eql(u8, eh.e_ident[0..4], "\x7fELF")) return error.NotElfFile; |
| 70 | + if (eh.e_type != elf.ET_DYN) return error.NotDynamicLibrary; |
| 71 | + |
| 72 | + const elf_addr = @ptrToInt(bytes.ptr); |
| 73 | + var ph_addr: usize = elf_addr + eh.e_phoff; |
| 74 | + |
| 75 | + var base: usize = @maxValue(usize); |
| 76 | + var maybe_dynv: ?[*]usize = null; |
| 77 | + { |
| 78 | + var i: usize = 0; |
| 79 | + while (i < eh.e_phnum) : ({ |
| 80 | + i += 1; |
| 81 | + ph_addr += eh.e_phentsize; |
| 82 | + }) { |
| 83 | + const ph = @intToPtr(*elf.Phdr, ph_addr); |
| 84 | + switch (ph.p_type) { |
| 85 | + elf.PT_LOAD => base = elf_addr + ph.p_offset - ph.p_vaddr, |
| 86 | + elf.PT_DYNAMIC => maybe_dynv = @intToPtr([*]usize, elf_addr + ph.p_offset), |
| 87 | + else => {}, |
| 88 | + } |
| 89 | + } |
| 90 | + } |
| 91 | + const dynv = maybe_dynv orelse return error.MissingDynamicLinkingInformation; |
| 92 | + if (base == @maxValue(usize)) return error.BaseNotFound; |
| 93 | + |
| 94 | + var maybe_strings: ?[*]u8 = null; |
| 95 | + var maybe_syms: ?[*]elf.Sym = null; |
| 96 | + var maybe_hashtab: ?[*]linux.Elf_Symndx = null; |
| 97 | + var maybe_versym: ?[*]u16 = null; |
| 98 | + var maybe_verdef: ?*elf.Verdef = null; |
| 99 | + |
| 100 | + { |
| 101 | + var i: usize = 0; |
| 102 | + while (dynv[i] != 0) : (i += 2) { |
| 103 | + const p = base + dynv[i + 1]; |
| 104 | + switch (dynv[i]) { |
| 105 | + elf.DT_STRTAB => maybe_strings = @intToPtr([*]u8, p), |
| 106 | + elf.DT_SYMTAB => maybe_syms = @intToPtr([*]elf.Sym, p), |
| 107 | + elf.DT_HASH => maybe_hashtab = @intToPtr([*]linux.Elf_Symndx, p), |
| 108 | + elf.DT_VERSYM => maybe_versym = @intToPtr([*]u16, p), |
| 109 | + elf.DT_VERDEF => maybe_verdef = @intToPtr(*elf.Verdef, p), |
| 110 | + else => {}, |
| 111 | + } |
| 112 | + } |
| 113 | + } |
| 114 | + |
| 115 | + return ElfLib{ |
| 116 | + .base = base, |
| 117 | + .strings = maybe_strings orelse return error.ElfStringSectionNotFound, |
| 118 | + .syms = maybe_syms orelse return error.ElfSymSectionNotFound, |
| 119 | + .hashtab = maybe_hashtab orelse return error.ElfHashTableNotFound, |
| 120 | + .versym = maybe_versym, |
| 121 | + .verdef = maybe_verdef, |
| 122 | + }; |
| 123 | + } |
| 124 | + |
| 125 | + /// Returns the address of the symbol |
| 126 | + pub fn lookup(self: *const ElfLib, vername: []const u8, name: []const u8) ?usize { |
| 127 | + const maybe_versym = if (self.verdef == null) null else self.versym; |
| 128 | + |
| 129 | + const OK_TYPES = (1 << elf.STT_NOTYPE | 1 << elf.STT_OBJECT | 1 << elf.STT_FUNC | 1 << elf.STT_COMMON); |
| 130 | + const OK_BINDS = (1 << elf.STB_GLOBAL | 1 << elf.STB_WEAK | 1 << elf.STB_GNU_UNIQUE); |
| 131 | + |
| 132 | + var i: usize = 0; |
| 133 | + while (i < self.hashtab[1]) : (i += 1) { |
| 134 | + if (0 == (u32(1) << u5(self.syms[i].st_info & 0xf) & OK_TYPES)) continue; |
| 135 | + if (0 == (u32(1) << u5(self.syms[i].st_info >> 4) & OK_BINDS)) continue; |
| 136 | + if (0 == self.syms[i].st_shndx) continue; |
| 137 | + if (!mem.eql(u8, name, cstr.toSliceConst(self.strings + self.syms[i].st_name))) continue; |
| 138 | + if (maybe_versym) |versym| { |
| 139 | + if (!checkver(self.verdef.?, versym[i], vername, self.strings)) |
| 140 | + continue; |
| 141 | + } |
| 142 | + return self.base + self.syms[i].st_value; |
| 143 | + } |
| 144 | + |
| 145 | + return null; |
| 146 | + } |
| 147 | +}; |
| 148 | + |
| 149 | +fn checkver(def_arg: *elf.Verdef, vsym_arg: i32, vername: []const u8, strings: [*]u8) bool { |
| 150 | + var def = def_arg; |
| 151 | + const vsym = @bitCast(u32, vsym_arg) & 0x7fff; |
| 152 | + while (true) { |
| 153 | + if (0 == (def.vd_flags & elf.VER_FLG_BASE) and (def.vd_ndx & 0x7fff) == vsym) |
| 154 | + break; |
| 155 | + if (def.vd_next == 0) |
| 156 | + return false; |
| 157 | + def = @intToPtr(*elf.Verdef, @ptrToInt(def) + def.vd_next); |
| 158 | + } |
| 159 | + const aux = @intToPtr(*elf.Verdaux, @ptrToInt(def) + def.vd_aux); |
| 160 | + return mem.eql(u8, vername, cstr.toSliceConst(strings + aux.vda_name)); |
| 161 | +} |
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