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add basic std lib code for loading dynamic libraries
this is going to only work for very basic libraries; I plan to slowly add more features over time to support more complicated libraries
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,161 @@ | ||
| 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 findAndOpen(allocator: *mem.Allocator, name: []const u8) !DynLib { | ||
| return open(allocator, name); | ||
| } | ||
|
|
||
| /// 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); | ||
| errdefer std.os.close(fd); | ||
|
|
||
| const size = usize((try std.os.posixFStat(fd)).size); | ||
|
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| 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]; | ||
|
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| 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; | ||
|
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||
| 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, | ||
| }; | ||
| } | ||
|
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||
| /// 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; | ||
|
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||
| 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); | ||
|
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||
| var i: usize = 0; | ||
| while (i < self.hashtab[1]) : (i += 1) { | ||
| if (0 == (u32(1) << u5(self.syms[i].st_info & 0xf) & OK_TYPES)) continue; | ||
| if (0 == (u32(1) << 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; | ||
| } | ||
|
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||
| return null; | ||
| } | ||
| }; | ||
|
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||
| 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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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,3 @@ | ||
| export fn add(a: i32, b: i32) i32 { | ||
| return a + b; | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| const Builder = @import("std").build.Builder; | ||
|
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| pub fn build(b: *Builder) void { | ||
| const opts = b.standardReleaseOptions(); | ||
|
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| const lib = b.addSharedLibrary("add", "add.zig", b.version(1, 0, 0)); | ||
| lib.setBuildMode(opts); | ||
| lib.linkSystemLibrary("c"); | ||
|
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| const main = b.addExecutable("main", "main.zig"); | ||
| main.setBuildMode(opts); | ||
|
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| const run = b.addCommand(".", b.env_map, [][]const u8{ | ||
| main.getOutputPath(), | ||
| lib.getOutputPath(), | ||
| }); | ||
| run.step.dependOn(&lib.step); | ||
| run.step.dependOn(&main.step); | ||
|
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| const test_step = b.step("test", "Test the program"); | ||
| test_step.dependOn(&run.step); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,17 @@ | ||
| const std = @import("std"); | ||
|
|
||
| pub fn main() !void { | ||
| const args = try std.os.argsAlloc(std.debug.global_allocator); | ||
| defer std.os.argsFree(std.debug.global_allocator, args); | ||
|
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| const dynlib_name = args[1]; | ||
|
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| var lib = try std.DynLib.open(std.debug.global_allocator, dynlib_name); | ||
| defer lib.close(); | ||
|
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| const addr = lib.lookup("add") orelse return error.SymbolNotFound; | ||
| const addFn = @intToPtr(extern fn (i32, i32) i32, addr); | ||
|
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| const result = addFn(12, 34); | ||
| std.debug.assert(result == 46); | ||
| } |