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macho: add hot-code swapping poc

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This commit is contained in:
Jakub Konka 2023-03-16 20:41:46 +01:00
parent 266c81322e
commit f1e25cf43e
7 changed files with 165 additions and 110 deletions
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2
build.zig
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@ -152,6 +152,7 @@ pub fn build(b: *std.Build) !void {
if (only_install_lib_files)
return;
const entitlements = b.option([]const u8, "entitlements", "Path to entitlements file for hot-code swapping without sudo on macOS");
const tracy = b.option([]const u8, "tracy", "Enable Tracy integration. Supply path to Tracy source");
const tracy_callstack = b.option(bool, "tracy-callstack", "Include callstack information with Tracy data. Does nothing if -Dtracy is not provided") orelse (tracy != null);
const tracy_allocation = b.option(bool, "tracy-allocation", "Include allocation information with Tracy data. Does nothing if -Dtracy is not provided") orelse (tracy != null);
@ -173,6 +174,7 @@ pub fn build(b: *std.Build) !void {
exe.pie = pie;
exe.sanitize_thread = sanitize_thread;
exe.build_id = b.option(bool, "build-id", "Include a build id note") orelse false;
exe.entitlements = entitlements;
exe.install();
const compile_step = b.step("compile", "Build the self-hosted compiler");

4
lib/std/macho.zig
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@ -656,6 +656,10 @@ pub const segment_command_64 = extern struct {
pub fn segName(seg: *const segment_command_64) []const u8 {
return parseName(&seg.segname);
}
pub fn isWriteable(seg: segment_command_64) bool {
return seg.initprot & PROT.WRITE != 0;
}
};
pub const PROT = struct {

16
src/link.zig
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@ -392,6 +392,19 @@ pub const File = struct {
.linux => std.os.ptrace(std.os.linux.PTRACE.ATTACH, pid, 0, 0) catch |err| {
log.warn("ptrace failure: {s}", .{@errorName(err)});
},
.macos => {
const macho = base.cast(MachO).?;
if (macho.mach_task == null) {
if (std.os.darwin.machTaskForPid(pid)) |task| {
macho.mach_task = task;
std.os.ptrace(std.os.darwin.PT.ATTACHEXC, pid, 0, 0) catch |err| {
log.warn("ptrace failure: {s}", .{@errorName(err)});
};
} else |err| {
log.warn("failed to acquire Mach task for child process: {s}", .{@errorName(err)});
}
}
},
else => return error.HotSwapUnavailableOnHostOperatingSystem,
}
}
@ -430,6 +443,9 @@ pub const File = struct {
.linux => std.os.ptrace(std.os.linux.PTRACE.DETACH, pid, 0, 0) catch |err| {
log.warn("ptrace failure: {s}", .{@errorName(err)});
},
.macos => std.os.ptrace(std.os.darwin.PT.KILL, pid, 0, 0) catch |err| {
log.warn("ptrace failure: {s}", .{@errorName(err)});
},
else => return error.HotSwapUnavailableOnHostOperatingSystem,
}
}

55
src/link/MachO.zig
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@ -221,6 +221,9 @@ lazy_bindings: BindingTable = .{},
/// Table of tracked Decls.
decls: std.AutoArrayHashMapUnmanaged(Module.Decl.Index, DeclMetadata) = .{},
/// Mach task used when the compiler is in hot-code swapping mode.
mach_task: ?std.os.darwin.MachTask = null,
const DeclMetadata = struct {
atom: Atom.Index,
section: u8,
@ -584,7 +587,21 @@ pub fn flushModule(self: *MachO, comp: *Compilation, prog_node: *std.Progress.No
try self.allocateSpecialSymbols();
for (self.relocs.keys()) |atom_index| {
try Atom.resolveRelocations(self, atom_index);
if (self.relocs.get(atom_index) == null) continue;
const atom = self.getAtom(atom_index);
const sym = atom.getSymbol(self);
const section = self.sections.get(sym.n_sect - 1).header;
const file_offset = section.offset + sym.n_value - section.addr;
var code = std.ArrayList(u8).init(self.base.allocator);
defer code.deinit();
try code.resize(atom.size);
const amt = try self.base.file.?.preadAll(code.items, file_offset);
if (amt != code.items.len) return error.InputOutput;
try self.writeAtom(atom_index, code.items);
}
if (build_options.enable_logging) {
@ -1052,14 +1069,38 @@ pub fn parseDependentLibs(self: *MachO, syslibroot: ?[]const u8, dependent_libs:
}
}
pub fn writeAtom(self: *MachO, atom_index: Atom.Index, code: []const u8) !void {
pub fn writeAtom(self: *MachO, atom_index: Atom.Index, code: []u8) !void {
const atom = self.getAtom(atom_index);
const sym = atom.getSymbol(self);
const section = self.sections.get(sym.n_sect - 1);
const file_offset = section.header.offset + sym.n_value - section.header.addr;
log.debug("writing atom for symbol {s} at file offset 0x{x}", .{ atom.getName(self), file_offset });
if (self.relocs.get(atom_index)) |relocs| {
try Atom.resolveRelocations(self, atom_index, relocs.items, code);
}
if (self.base.child_pid) |pid| blk: {
const task = self.mach_task orelse {
log.warn("cannot hot swap: no Mach task acquired for child process with pid {d}", .{pid});
break :blk;
};
self.writeAtomToMemory(task, section.segment_index, sym.n_value, code) catch |err| {
log.warn("cannot hot swap: writing to memory failed: {s}", .{@errorName(err)});
};
}
try self.base.file.?.pwriteAll(code, file_offset);
try Atom.resolveRelocations(self, atom_index);
}
fn writeAtomToMemory(self: *MachO, task: std.os.darwin.MachTask, segment_index: u8, addr: u64, code: []const u8) !void {
const segment = self.segments.items[segment_index];
if (!segment.isWriteable()) {
try task.setCurrProtection(addr, code.len, macho.PROT.READ | macho.PROT.WRITE | macho.PROT.COPY);
}
defer if (!segment.isWriteable()) task.setCurrProtection(addr, code.len, segment.initprot) catch {};
const nwritten = try task.writeMem(addr, code, self.base.options.target.cpu.arch);
if (nwritten != code.len) return error.InputOutput;
}
fn writePtrWidthAtom(self: *MachO, atom_index: Atom.Index) !void {
@ -2063,7 +2104,7 @@ pub fn updateFunc(self: *MachO, module: *Module, func: *Module.Fn, air: Air, liv
else
try codegen.generateFunction(&self.base, decl.srcLoc(), func, air, liveness, &code_buffer, .none);
const code = switch (res) {
var code = switch (res) {
.ok => code_buffer.items,
.fail => |em| {
decl.analysis = .codegen_failure;
@ -2115,7 +2156,7 @@ pub fn lowerUnnamedConst(self: *MachO, typed_value: TypedValue, decl_index: Modu
const res = try codegen.generateSymbol(&self.base, decl.srcLoc(), typed_value, &code_buffer, .none, .{
.parent_atom_index = self.getAtom(atom_index).getSymbolIndex().?,
});
const code = switch (res) {
var code = switch (res) {
.ok => code_buffer.items,
.fail => |em| {
decl.analysis = .codegen_failure;
@ -2202,7 +2243,7 @@ pub fn updateDecl(self: *MachO, module: *Module, decl_index: Module.Decl.Index)
.parent_atom_index = atom.getSymbolIndex().?,
});
const code = switch (res) {
var code = switch (res) {
.ok => code_buffer.items,
.fail => |em| {
decl.analysis = .codegen_failure;
@ -2375,7 +2416,7 @@ pub fn getOutputSection(self: *MachO, sect: macho.section_64) !?u8 {
return sect_id;
}
fn updateDeclCode(self: *MachO, decl_index: Module.Decl.Index, code: []const u8) !u64 {
fn updateDeclCode(self: *MachO, decl_index: Module.Decl.Index, code: []u8) !u64 {
const gpa = self.base.allocator;
const mod = self.base.options.module.?;
const decl = mod.declPtr(decl_index);

16
src/link/MachO/Atom.zig
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@ -183,19 +183,11 @@ pub fn addLazyBinding(macho_file: *MachO, atom_index: Index, binding: Binding) !
try gop.value_ptr.append(gpa, binding);
}
pub fn resolveRelocations(macho_file: *MachO, atom_index: Index) !void {
const atom = macho_file.getAtom(atom_index);
const relocs = macho_file.relocs.get(atom_index) orelse return;
const source_sym = atom.getSymbol(macho_file);
const source_section = macho_file.sections.get(source_sym.n_sect - 1).header;
const file_offset = source_section.offset + source_sym.n_value - source_section.addr;
log.debug("relocating '{s}'", .{atom.getName(macho_file)});
for (relocs.items) |*reloc| {
pub fn resolveRelocations(macho_file: *MachO, atom_index: Index, relocs: []Relocation, code: []u8) !void {
log.debug("relocating '{s}'", .{macho_file.getAtom(atom_index).getName(macho_file)});
for (relocs) |*reloc| {
if (!reloc.dirty) continue;
try reloc.resolve(macho_file, atom_index, file_offset);
try reloc.resolve(macho_file, atom_index, code);
reloc.dirty = false;
}
}

78
src/link/MachO/Relocation.zig
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@ -50,7 +50,7 @@ pub fn getTargetAtomIndex(self: Relocation, macho_file: *MachO) ?Atom.Index {
return macho_file.getAtomIndexForSymbol(self.target);
}
pub fn resolve(self: Relocation, macho_file: *MachO, atom_index: Atom.Index, base_offset: u64) !void {
pub fn resolve(self: Relocation, macho_file: *MachO, atom_index: Atom.Index, code: []u8) !void {
const arch = macho_file.base.options.target.cpu.arch;
const atom = macho_file.getAtom(atom_index);
const source_sym = atom.getSymbol(macho_file);
@ -68,42 +68,28 @@ pub fn resolve(self: Relocation, macho_file: *MachO, atom_index: Atom.Index, bas
});
switch (arch) {
.aarch64 => return self.resolveAarch64(macho_file, source_addr, target_addr, base_offset),
.x86_64 => return self.resolveX8664(macho_file, source_addr, target_addr, base_offset),
.aarch64 => return self.resolveAarch64(source_addr, target_addr, code),
.x86_64 => return self.resolveX8664(source_addr, target_addr, code),
else => unreachable,
}
}
fn resolveAarch64(
self: Relocation,
macho_file: *MachO,
source_addr: u64,
target_addr: i64,
base_offset: u64,
code: []u8,
) !void {
const rel_type = @intToEnum(macho.reloc_type_arm64, self.type);
if (rel_type == .ARM64_RELOC_UNSIGNED) {
var buffer: [@sizeOf(u64)]u8 = undefined;
const code = blk: {
switch (self.length) {
2 => {
mem.writeIntLittle(u32, buffer[0..4], @truncate(u32, @bitCast(u64, target_addr)));
break :blk buffer[0..4];
},
3 => {
mem.writeIntLittle(u64, &buffer, @bitCast(u64, target_addr));
break :blk &buffer;
},
return switch (self.length) {
2 => mem.writeIntLittle(u32, code[self.offset..][0..4], @truncate(u32, @bitCast(u64, target_addr))),
3 => mem.writeIntLittle(u64, code[self.offset..][0..8], @bitCast(u64, target_addr)),
else => unreachable,
}
};
return macho_file.base.file.?.pwriteAll(code, base_offset + self.offset);
}
var buffer: [@sizeOf(u32)]u8 = undefined;
const amt = try macho_file.base.file.?.preadAll(&buffer, base_offset + self.offset);
if (amt != buffer.len) return error.InputOutput;
var buffer = code[self.offset..][0..4];
switch (rel_type) {
.ARM64_RELOC_BRANCH26 => {
const displacement = math.cast(
@ -114,10 +100,10 @@ fn resolveAarch64(
.unconditional_branch_immediate = mem.bytesToValue(meta.TagPayload(
aarch64.Instruction,
aarch64.Instruction.unconditional_branch_immediate,
), &buffer),
), buffer),
};
inst.unconditional_branch_immediate.imm26 = @truncate(u26, @bitCast(u28, displacement >> 2));
mem.writeIntLittle(u32, &buffer, inst.toU32());
mem.writeIntLittle(u32, buffer, inst.toU32());
},
.ARM64_RELOC_PAGE21,
.ARM64_RELOC_GOT_LOAD_PAGE21,
@ -130,31 +116,31 @@ fn resolveAarch64(
.pc_relative_address = mem.bytesToValue(meta.TagPayload(
aarch64.Instruction,
aarch64.Instruction.pc_relative_address,
), &buffer),
), buffer),
};
inst.pc_relative_address.immhi = @truncate(u19, pages >> 2);
inst.pc_relative_address.immlo = @truncate(u2, pages);
mem.writeIntLittle(u32, &buffer, inst.toU32());
mem.writeIntLittle(u32, buffer, inst.toU32());
},
.ARM64_RELOC_PAGEOFF12,
.ARM64_RELOC_GOT_LOAD_PAGEOFF12,
=> {
const narrowed = @truncate(u12, @intCast(u64, target_addr));
if (isArithmeticOp(&buffer)) {
if (isArithmeticOp(buffer)) {
var inst = aarch64.Instruction{
.add_subtract_immediate = mem.bytesToValue(meta.TagPayload(
aarch64.Instruction,
aarch64.Instruction.add_subtract_immediate,
), &buffer),
), buffer),
};
inst.add_subtract_immediate.imm12 = narrowed;
mem.writeIntLittle(u32, &buffer, inst.toU32());
mem.writeIntLittle(u32, buffer, inst.toU32());
} else {
var inst = aarch64.Instruction{
.load_store_register = mem.bytesToValue(meta.TagPayload(
aarch64.Instruction,
aarch64.Instruction.load_store_register,
), &buffer),
), buffer),
};
const offset: u12 = blk: {
if (inst.load_store_register.size == 0) {
@ -170,7 +156,7 @@ fn resolveAarch64(
}
};
inst.load_store_register.offset = offset;
mem.writeIntLittle(u32, &buffer, inst.toU32());
mem.writeIntLittle(u32, buffer, inst.toU32());
}
},
.ARM64_RELOC_TLVP_LOAD_PAGEOFF12 => {
@ -180,11 +166,11 @@ fn resolveAarch64(
size: u2,
};
const reg_info: RegInfo = blk: {
if (isArithmeticOp(&buffer)) {
if (isArithmeticOp(buffer)) {
const inst = mem.bytesToValue(meta.TagPayload(
aarch64.Instruction,
aarch64.Instruction.add_subtract_immediate,
), &buffer);
), buffer);
break :blk .{
.rd = inst.rd,
.rn = inst.rn,
@ -194,7 +180,7 @@ fn resolveAarch64(
const inst = mem.bytesToValue(meta.TagPayload(
aarch64.Instruction,
aarch64.Instruction.load_store_register,
), &buffer);
), buffer);
break :blk .{
.rd = inst.rt,
.rn = inst.rn,
@ -214,29 +200,25 @@ fn resolveAarch64(
.sf = @truncate(u1, reg_info.size),
},
};
mem.writeIntLittle(u32, &buffer, inst.toU32());
mem.writeIntLittle(u32, buffer, inst.toU32());
},
.ARM64_RELOC_POINTER_TO_GOT => {
const result = @intCast(i32, @intCast(i64, target_addr) - @intCast(i64, source_addr));
mem.writeIntLittle(i32, &buffer, result);
mem.writeIntLittle(i32, buffer, result);
},
.ARM64_RELOC_SUBTRACTOR => unreachable,
.ARM64_RELOC_ADDEND => unreachable,
.ARM64_RELOC_UNSIGNED => unreachable,
}
try macho_file.base.file.?.pwriteAll(&buffer, base_offset + self.offset);
}
fn resolveX8664(
self: Relocation,
macho_file: *MachO,
source_addr: u64,
target_addr: i64,
base_offset: u64,
code: []u8,
) !void {
const rel_type = @intToEnum(macho.reloc_type_x86_64, self.type);
var buffer: [@sizeOf(u64)]u8 = undefined;
const code = blk: {
switch (rel_type) {
.X86_64_RELOC_BRANCH,
.X86_64_RELOC_GOT,
@ -244,8 +226,7 @@ fn resolveX8664(
.X86_64_RELOC_TLV,
=> {
const displacement = @intCast(i32, @intCast(i64, target_addr) - @intCast(i64, source_addr) - 4);
mem.writeIntLittle(u32, buffer[0..4], @bitCast(u32, displacement));
break :blk buffer[0..4];
mem.writeIntLittle(u32, code[self.offset..][0..4], @bitCast(u32, displacement));
},
.X86_64_RELOC_SIGNED,
.X86_64_RELOC_SIGNED_1,
@ -260,26 +241,21 @@ fn resolveX8664(
else => unreachable,
};
const displacement = @intCast(i32, target_addr - @intCast(i64, source_addr + correction + 4));
mem.writeIntLittle(u32, buffer[0..4], @bitCast(u32, displacement));
break :blk buffer[0..4];
mem.writeIntLittle(u32, code[self.offset..][0..4], @bitCast(u32, displacement));
},
.X86_64_RELOC_UNSIGNED => {
switch (self.length) {
2 => {
mem.writeIntLittle(u32, buffer[0..4], @truncate(u32, @bitCast(u64, target_addr)));
break :blk buffer[0..4];
mem.writeIntLittle(u32, code[self.offset..][0..4], @truncate(u32, @bitCast(u64, target_addr)));
},
3 => {
mem.writeIntLittle(u64, buffer[0..8], @bitCast(u64, target_addr));
break :blk &buffer;
mem.writeIntLittle(u64, code[self.offset..][0..8], @bitCast(u64, target_addr));
},
else => unreachable,
}
},
.X86_64_RELOC_SUBTRACTOR => unreachable,
}
};
try macho_file.base.file.?.pwriteAll(code, base_offset + self.offset);
}
inline fn isArithmeticOp(inst: *const [4]u8) bool {

24
src/main.zig
View File

@ -3851,6 +3851,28 @@ fn runOrTestHotSwap(
if (runtime_args_start) |i| {
try argv.appendSlice(all_args[i..]);
}
switch (builtin.target.os.tag) {
.macos, .ios, .tvos, .watchos => {
const PosixSpawn = std.os.darwin.PosixSpawn;
var attr = try PosixSpawn.Attr.init();
defer attr.deinit();
const flags: u16 = std.os.darwin.POSIX_SPAWN_SETSIGDEF |
std.os.darwin.POSIX_SPAWN_SETSIGMASK |
std.os.darwin._POSIX_SPAWN_DISABLE_ASLR;
try attr.set(flags);
var arena_allocator = std.heap.ArenaAllocator.init(gpa);
defer arena_allocator.deinit();
const arena = arena_allocator.allocator();
const argv_buf = try arena.allocSentinel(?[*:0]u8, argv.items.len, null);
for (argv.items, 0..) |arg, i| argv_buf[i] = (try arena.dupeZ(u8, arg)).ptr;
const pid = try PosixSpawn.spawn(argv.items[0], null, attr, argv_buf, std.c.environ);
return pid;
},
else => {
var child = std.ChildProcess.init(argv.items, gpa);
child.stdin_behavior = .Inherit;
@ -3860,6 +3882,8 @@ fn runOrTestHotSwap(
try child.spawn();
return child.id;
},
}
}
const AfterUpdateHook = union(enum) {