1 files changed, 280 insertions, 0 deletions
diff --git a/lib/std/dynamic_library.zig b/lib/std/dynamic_library.zig
new file mode 100644
index 0000000000..3413788019
--- /dev/null
+++ b/lib/std/dynamic_library.zig
@@ -0,0 +1,280 @@
+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: [*]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: ?[*]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([*]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 == (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, 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: [*]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");
+}