From 0b67463b9285158d818d6cd196c5f2ba9961a05e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Wed, 13 Nov 2024 11:15:56 +0100
Subject: [PATCH 1/6] riscv64: Support the fp alias for register s0 in inline
 assembly.

---
 src/arch/riscv64/CodeGen.zig | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/arch/riscv64/CodeGen.zig b/src/arch/riscv64/CodeGen.zig
index 29a0a8b8b5..a836d02d71 100644
--- a/src/arch/riscv64/CodeGen.zig
+++ b/src/arch/riscv64/CodeGen.zig
@@ -8442,6 +8442,10 @@ fn failSymbol(func: *Func, comptime format: []const u8, args: anytype) InnerErro
 }
 
 fn parseRegName(name: []const u8) ?Register {
+    // The `fp` alias for `s0` is awkward to fit into the current `Register` scheme, so for now we
+    // special-case it here.
+    if (std.mem.eql(u8, name, "fp")) return .s0;
+
     return std.meta.stringToEnum(Register, name);
 }
 

From 8af82621d75f9f0d96ebf734f5ea862d06a5f1fa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Wed, 13 Nov 2024 06:04:04 +0100
Subject: [PATCH 2/6] compiler: Improve the handling of unwind table levels.

The goal here is to support both levels of unwind tables (sync and async) in
zig cc and zig build. Previously, the LLVM backend always used async tables
while zig cc was partially influenced by whatever was Clang's default.
---
 lib/std/Build.zig                        | 10 ++---
 lib/std/Build/Module.zig                 | 13 ++++--
 lib/std/builtin.zig                      |  8 ++++
 src/Builtin.zig                          |  3 ++
 src/Compilation.zig                      | 27 +++++++++---
 src/Compilation/Config.zig               | 24 ++++++-----
 src/Package/Module.zig                   |  7 +--
 src/clang_options_data.zig               | 18 +++++++-
 src/codegen/llvm.zig                     |  7 ++-
 src/libcxx.zig                           |  9 ++--
 src/libunwind.zig                        |  3 +-
 src/main.zig                             | 54 ++++++++++++++++++++----
 src/mingw.zig                            | 17 ++++++--
 src/target.zig                           | 13 +++++-
 test/standalone/stack_iterator/build.zig |  6 +--
 tools/update_clang_options.zig           |  8 ++++
 16 files changed, 174 insertions(+), 53 deletions(-)

diff --git a/lib/std/Build.zig b/lib/std/Build.zig
index 041de3e06f..65e2db3d1d 100644
--- a/lib/std/Build.zig
+++ b/lib/std/Build.zig
@@ -706,7 +706,7 @@ pub const ExecutableOptions = struct {
     single_threaded: ?bool = null,
     pic: ?bool = null,
     strip: ?bool = null,
-    unwind_tables: ?bool = null,
+    unwind_tables: ?std.builtin.UnwindTables = null,
     omit_frame_pointer: ?bool = null,
     sanitize_thread: ?bool = null,
     error_tracing: ?bool = null,
@@ -762,7 +762,7 @@ pub const ObjectOptions = struct {
     single_threaded: ?bool = null,
     pic: ?bool = null,
     strip: ?bool = null,
-    unwind_tables: ?bool = null,
+    unwind_tables: ?std.builtin.UnwindTables = null,
     omit_frame_pointer: ?bool = null,
     sanitize_thread: ?bool = null,
     error_tracing: ?bool = null,
@@ -810,7 +810,7 @@ pub const SharedLibraryOptions = struct {
     single_threaded: ?bool = null,
     pic: ?bool = null,
     strip: ?bool = null,
-    unwind_tables: ?bool = null,
+    unwind_tables: ?std.builtin.UnwindTables = null,
     omit_frame_pointer: ?bool = null,
     sanitize_thread: ?bool = null,
     error_tracing: ?bool = null,
@@ -867,7 +867,7 @@ pub const StaticLibraryOptions = struct {
     single_threaded: ?bool = null,
     pic: ?bool = null,
     strip: ?bool = null,
-    unwind_tables: ?bool = null,
+    unwind_tables: ?std.builtin.UnwindTables = null,
     omit_frame_pointer: ?bool = null,
     sanitize_thread: ?bool = null,
     error_tracing: ?bool = null,
@@ -919,7 +919,7 @@ pub const TestOptions = struct {
     single_threaded: ?bool = null,
     pic: ?bool = null,
     strip: ?bool = null,
-    unwind_tables: ?bool = null,
+    unwind_tables: ?std.builtin.UnwindTables = null,
     omit_frame_pointer: ?bool = null,
     sanitize_thread: ?bool = null,
     error_tracing: ?bool = null,
diff --git a/lib/std/Build/Module.zig b/lib/std/Build/Module.zig
index 347695a4c0..0e421280f0 100644
--- a/lib/std/Build/Module.zig
+++ b/lib/std/Build/Module.zig
@@ -22,7 +22,7 @@ frameworks: std.StringArrayHashMapUnmanaged(LinkFrameworkOptions),
 link_objects: std.ArrayListUnmanaged(LinkObject),
 
 strip: ?bool,
-unwind_tables: ?bool,
+unwind_tables: ?std.builtin.UnwindTables,
 single_threaded: ?bool,
 stack_protector: ?bool,
 stack_check: ?bool,
@@ -218,7 +218,7 @@ pub const CreateOptions = struct {
     link_libcpp: ?bool = null,
     single_threaded: ?bool = null,
     strip: ?bool = null,
-    unwind_tables: ?bool = null,
+    unwind_tables: ?std.builtin.UnwindTables = null,
     dwarf_format: ?std.dwarf.Format = null,
     code_model: std.builtin.CodeModel = .default,
     stack_protector: ?bool = null,
@@ -675,7 +675,6 @@ pub fn appendZigProcessFlags(
     const b = m.owner;
 
     try addFlag(zig_args, m.strip, "-fstrip", "-fno-strip");
-    try addFlag(zig_args, m.unwind_tables, "-funwind-tables", "-fno-unwind-tables");
     try addFlag(zig_args, m.single_threaded, "-fsingle-threaded", "-fno-single-threaded");
     try addFlag(zig_args, m.stack_check, "-fstack-check", "-fno-stack-check");
     try addFlag(zig_args, m.stack_protector, "-fstack-protector", "-fno-stack-protector");
@@ -695,6 +694,14 @@ pub fn appendZigProcessFlags(
         });
     }
 
+    if (m.unwind_tables) |unwind_tables| {
+        try zig_args.append(switch (unwind_tables) {
+            .none => "-fno-unwind-tables",
+            .sync => "-funwind-tables",
+            .@"async" => "-fasync-unwind-tables",
+        });
+    }
+
     try zig_args.ensureUnusedCapacity(1);
     if (m.optimize) |optimize| switch (optimize) {
         .Debug => zig_args.appendAssumeCapacity("-ODebug"),
diff --git a/lib/std/builtin.zig b/lib/std/builtin.zig
index 5ddde66a0a..eda7f0ff4f 100644
--- a/lib/std/builtin.zig
+++ b/lib/std/builtin.zig
@@ -804,6 +804,14 @@ pub const LinkMode = enum {
     dynamic,
 };
 
+/// This data structure is used by the Zig language code generation and
+/// therefore must be kept in sync with the compiler implementation.
+pub const UnwindTables = enum {
+    none,
+    sync,
+    @"async",
+};
+
 /// This data structure is used by the Zig language code generation and
 /// therefore must be kept in sync with the compiler implementation.
 pub const WasiExecModel = enum {
diff --git a/src/Builtin.zig b/src/Builtin.zig
index 8dc5b31c16..1782527f69 100644
--- a/src/Builtin.zig
+++ b/src/Builtin.zig
@@ -2,6 +2,7 @@ target: std.Target,
 zig_backend: std.builtin.CompilerBackend,
 output_mode: std.builtin.OutputMode,
 link_mode: std.builtin.LinkMode,
+unwind_tables: std.builtin.UnwindTables,
 is_test: bool,
 single_threaded: bool,
 link_libc: bool,
@@ -40,6 +41,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
         \\
         \\pub const output_mode: std.builtin.OutputMode = .{p_};
         \\pub const link_mode: std.builtin.LinkMode = .{p_};
+        \\pub const unwind_tables: std.builtin.UnwindTables = .{p_};
         \\pub const is_test = {};
         \\pub const single_threaded = {};
         \\pub const abi: std.Target.Abi = .{p_};
@@ -53,6 +55,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
         std.zig.fmtId(@tagName(zig_backend)),
         std.zig.fmtId(@tagName(opts.output_mode)),
         std.zig.fmtId(@tagName(opts.link_mode)),
+        std.zig.fmtId(@tagName(opts.unwind_tables)),
         opts.is_test,
         opts.single_threaded,
         std.zig.fmtId(@tagName(target.abi)),
diff --git a/src/Compilation.zig b/src/Compilation.zig
index c198b5af82..16d3589b5d 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -1261,12 +1261,15 @@ pub fn create(gpa: Allocator, arena: Allocator, options: CreateOptions) !*Compil
         // The "any" values provided by resolved config only account for
         // explicitly-provided settings. We now make them additionally account
         // for default setting resolution.
-        const any_unwind_tables = options.config.any_unwind_tables or options.root_mod.unwind_tables;
+        const any_unwind_tables = switch (options.config.any_unwind_tables) {
+            .none => options.root_mod.unwind_tables,
+            .sync, .@"async" => |uwt| uwt,
+        };
         const any_non_single_threaded = options.config.any_non_single_threaded or !options.root_mod.single_threaded;
         const any_sanitize_thread = options.config.any_sanitize_thread or options.root_mod.sanitize_thread;
         const any_fuzz = options.config.any_fuzz or options.root_mod.fuzz;
 
-        const link_eh_frame_hdr = options.link_eh_frame_hdr or any_unwind_tables;
+        const link_eh_frame_hdr = options.link_eh_frame_hdr or any_unwind_tables != .none;
         const build_id = options.build_id orelse .none;
 
         const link_libc = options.config.link_libc;
@@ -1354,6 +1357,7 @@ pub fn create(gpa: Allocator, arena: Allocator, options: CreateOptions) !*Compil
         cache.hash.add(options.config.pie);
         cache.hash.add(options.config.lto);
         cache.hash.add(options.config.link_mode);
+        cache.hash.add(options.config.any_unwind_tables);
         cache.hash.add(options.function_sections);
         cache.hash.add(options.data_sections);
         cache.hash.add(link_libc);
@@ -5538,10 +5542,17 @@ pub fn addCCArgs(
                 try argv.append("-Werror=date-time");
             }
 
-            if (mod.unwind_tables) {
-                try argv.append("-funwind-tables");
-            } else {
-                try argv.append("-fno-unwind-tables");
+            switch (mod.unwind_tables) {
+                .none => {
+                    try argv.append("-fno-unwind-tables");
+                    try argv.append("-fno-asynchronous-unwind-tables");
+                },
+                .sync => {
+                    // Need to override Clang's convoluted default logic.
+                    try argv.append("-fno-asynchronous-unwind-tables");
+                    try argv.append("-funwind-tables");
+                },
+                .@"async" => try argv.append("-fasynchronous-unwind-tables"),
             }
         },
         .shared_library, .ll, .bc, .unknown, .static_library, .object, .def, .zig, .res, .manifest => {},
@@ -6273,6 +6284,7 @@ pub const CrtFileOptions = struct {
     function_sections: ?bool = null,
     data_sections: ?bool = null,
     omit_frame_pointer: ?bool = null,
+    unwind_tables: ?std.builtin.UnwindTables = null,
     pic: ?bool = null,
     no_builtin: ?bool = null,
 };
@@ -6334,7 +6346,8 @@ pub fn build_crt_file(
             // Some libcs (e.g. musl) are opinionated about -fomit-frame-pointer.
             .omit_frame_pointer = options.omit_frame_pointer orelse comp.root_mod.omit_frame_pointer,
             .valgrind = false,
-            .unwind_tables = false,
+            // Some libcs (e.g. MinGW) are opinionated about -funwind-tables.
+            .unwind_tables = options.unwind_tables orelse .none,
             // Some CRT objects (e.g. musl's rcrt1.o and Scrt1.o) are opinionated about PIC.
             .pic = options.pic orelse comp.root_mod.pic,
             .optimize_mode = comp.compilerRtOptMode(),
diff --git a/src/Compilation/Config.zig b/src/Compilation/Config.zig
index 4458d474bb..baaa6c9f47 100644
--- a/src/Compilation/Config.zig
+++ b/src/Compilation/Config.zig
@@ -12,13 +12,14 @@ link_libunwind: bool,
 /// True if and only if the c_source_files field will have nonzero length when
 /// calling Compilation.create.
 any_c_source_files: bool,
-/// This is true if any Module has unwind_tables set explicitly to true. Until
-/// Compilation.create is called, it is possible for this to be false while in
-/// fact all Module instances have unwind_tables=true due to the default
-/// being unwind_tables=true. After Compilation.create is called this will
-/// also take into account the default setting, making this value true if and
-/// only if any Module has unwind_tables set to true.
-any_unwind_tables: bool,
+/// This is not `.none` if any `Module` has `unwind_tables` set explicitly to a
+/// value other than `.none`. Until `Compilation.create()` is called, it is
+/// possible for this to be `.none` while in fact all `Module` instances have
+/// `unwind_tables != .none` due to the default. After `Compilation.create()` is
+/// called, this will also take into account the default setting, making this
+/// value `.sync` or `.@"async"` if and only if any `Module` has
+/// `unwind_tables != .none`.
+any_unwind_tables: std.builtin.UnwindTables,
 /// This is true if any Module has single_threaded set explicitly to false. Until
 /// Compilation.create is called, it is possible for this to be false while in
 /// fact all Module instances have single_threaded=false due to the default
@@ -85,7 +86,7 @@ pub const Options = struct {
     any_non_single_threaded: bool = false,
     any_sanitize_thread: bool = false,
     any_fuzz: bool = false,
-    any_unwind_tables: bool = false,
+    any_unwind_tables: std.builtin.UnwindTables = .none,
     any_dyn_libs: bool = false,
     any_c_source_files: bool = false,
     any_non_stripped: bool = false,
@@ -356,8 +357,11 @@ pub fn resolve(options: Options) ResolveError!Config {
         break :b false;
     };
 
-    const any_unwind_tables = options.any_unwind_tables or
-        link_libunwind or target_util.needUnwindTables(target);
+    const any_unwind_tables = b: {
+        if (options.any_unwind_tables != .none) break :b options.any_unwind_tables;
+
+        break :b target_util.needUnwindTables(target, link_libunwind, options.any_sanitize_thread);
+    };
 
     const link_mode = b: {
         const explicitly_exe_or_dyn_lib = switch (options.output_mode) {
diff --git a/src/Package/Module.zig b/src/Package/Module.zig
index 781a8e50c2..bfcef038ed 100644
--- a/src/Package/Module.zig
+++ b/src/Package/Module.zig
@@ -27,7 +27,7 @@ red_zone: bool,
 sanitize_c: bool,
 sanitize_thread: bool,
 fuzz: bool,
-unwind_tables: bool,
+unwind_tables: std.builtin.UnwindTables,
 cc_argv: []const []const u8,
 /// (SPIR-V) whether to generate a structured control flow graph or not
 structured_cfg: bool,
@@ -91,7 +91,7 @@ pub const CreateOptions = struct {
         /// other number means stack protection with that buffer size.
         stack_protector: ?u32 = null,
         red_zone: ?bool = null,
-        unwind_tables: ?bool = null,
+        unwind_tables: ?std.builtin.UnwindTables = null,
         sanitize_c: ?bool = null,
         sanitize_thread: ?bool = null,
         fuzz: ?bool = null,
@@ -112,7 +112,7 @@ pub fn create(arena: Allocator, options: CreateOptions) !*Package.Module {
     if (options.inherited.sanitize_thread == true) assert(options.global.any_sanitize_thread);
     if (options.inherited.fuzz == true) assert(options.global.any_fuzz);
     if (options.inherited.single_threaded == false) assert(options.global.any_non_single_threaded);
-    if (options.inherited.unwind_tables == true) assert(options.global.any_unwind_tables);
+    if (options.inherited.unwind_tables) |uwt| if (uwt != .none) assert(options.global.any_unwind_tables != .none);
     if (options.inherited.error_tracing == true) assert(options.global.any_error_tracing);
 
     const resolved_target = options.inherited.resolved_target orelse options.parent.?.resolved_target;
@@ -382,6 +382,7 @@ pub fn create(arena: Allocator, options: CreateOptions) !*Package.Module {
             .zig_backend = zig_backend,
             .output_mode = options.global.output_mode,
             .link_mode = options.global.link_mode,
+            .unwind_tables = options.global.any_unwind_tables,
             .is_test = options.global.is_test,
             .single_threaded = single_threaded,
             .link_libc = options.global.link_libc,
diff --git a/src/clang_options_data.zig b/src/clang_options_data.zig
index 9ced7e9ebe..88cf41d0d4 100644
--- a/src/clang_options_data.zig
+++ b/src/clang_options_data.zig
@@ -2757,7 +2757,14 @@ flagpd1("fast"),
 flagpd1("fastcp"),
 flagpd1("fastf"),
 flagpd1("fasync-exceptions"),
-flagpd1("fasynchronous-unwind-tables"),
+.{
+    .name = "fasynchronous-unwind-tables",
+    .syntax = .flag,
+    .zig_equivalent = .asynchronous_unwind_tables,
+    .pd1 = true,
+    .pd2 = false,
+    .psl = false,
+},
 flagpd1("fauto-import"),
 flagpd1("fauto-profile"),
 flagpd1("fauto-profile-accurate"),
@@ -3247,7 +3254,14 @@ flagpd1("fno-assume-sane-operator-new"),
 flagpd1("fno-assume-unique-vtables"),
 flagpd1("fno-assumptions"),
 flagpd1("fno-async-exceptions"),
-flagpd1("fno-asynchronous-unwind-tables"),
+.{
+    .name = "fno-asynchronous-unwind-tables",
+    .syntax = .flag,
+    .zig_equivalent = .no_asynchronous_unwind_tables,
+    .pd1 = true,
+    .pd2 = false,
+    .psl = false,
+},
 flagpd1("fno-auto-import"),
 flagpd1("fno-auto-profile"),
 flagpd1("fno-auto-profile-accurate"),
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index ff1e679898..b94ea07995 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -3141,8 +3141,11 @@ pub const Object = struct {
             } }, &o.builder);
         }
         try attributes.addFnAttr(.nounwind, &o.builder);
-        if (owner_mod.unwind_tables) {
-            try attributes.addFnAttr(.{ .uwtable = Builder.Attribute.UwTable.default }, &o.builder);
+        if (owner_mod.unwind_tables != .none) {
+            try attributes.addFnAttr(
+                .{ .uwtable = if (owner_mod.unwind_tables == .@"async") .@"async" else .sync },
+                &o.builder,
+            );
         }
         if (owner_mod.no_builtin) {
             // The intent here is for compiler-rt and libc functions to not generate
diff --git a/src/libcxx.zig b/src/libcxx.zig
index 39fd999112..6386d493a6 100644
--- a/src/libcxx.zig
+++ b/src/libcxx.zig
@@ -397,7 +397,6 @@ pub fn buildLibCXXABI(comp: *Compilation, prog_node: std.Progress.Node) BuildErr
 
     const optimize_mode = comp.compilerRtOptMode();
     const strip = comp.compilerRtStrip();
-    const unwind_tables = true;
 
     const config = Compilation.Config.resolve(.{
         .output_mode = output_mode,
@@ -409,7 +408,6 @@ pub fn buildLibCXXABI(comp: *Compilation, prog_node: std.Progress.Node) BuildErr
         .root_optimize_mode = optimize_mode,
         .root_strip = strip,
         .link_libc = true,
-        .any_unwind_tables = unwind_tables,
         .lto = comp.config.lto,
         .any_sanitize_thread = comp.config.any_sanitize_thread,
     }) catch |err| {
@@ -440,7 +438,12 @@ pub fn buildLibCXXABI(comp: *Compilation, prog_node: std.Progress.Node) BuildErr
             .valgrind = false,
             .optimize_mode = optimize_mode,
             .structured_cfg = comp.root_mod.structured_cfg,
-            .unwind_tables = unwind_tables,
+            // See the `-fno-exceptions` logic for WASI.
+            // The old 32-bit x86 variant of SEH doesn't use tables.
+            .unwind_tables = if (target.os.tag == .wasi or (target.cpu.arch == .x86 and target.os.tag == .windows))
+                .none
+            else
+                .@"async",
             .pic = comp.root_mod.pic,
         },
         .global = config,
diff --git a/src/libunwind.zig b/src/libunwind.zig
index 1e101da229..4b3583e1cd 100644
--- a/src/libunwind.zig
+++ b/src/libunwind.zig
@@ -65,7 +65,8 @@ pub fn buildStaticLib(comp: *Compilation, prog_node: std.Progress.Node) BuildErr
             .sanitize_c = false,
             .sanitize_thread = false,
             // necessary so that libunwind can unwind through its own stack frames
-            .unwind_tables = true,
+            // The old 32-bit x86 variant of SEH doesn't use tables.
+            .unwind_tables = if (target.cpu.arch == .x86 and target.os.tag == .windows) .none else .@"async",
             .pic = if (target_util.supports_fpic(target)) true else null,
             .optimize_mode = comp.compilerRtOptMode(),
         },
diff --git a/src/main.zig b/src/main.zig
index 23c4d7507e..1f8bd8d065 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -510,6 +510,7 @@ const usage_build_generic =
     \\  -ffuzz                    Enable fuzz testing instrumentation
     \\  -fno-fuzz                 Disable fuzz testing instrumentation
     \\  -funwind-tables           Always produce unwind table entries for all functions
+    \\  -fasync-unwind-tables     Always produce asynchronous unwind table entries for all functions
     \\  -fno-unwind-tables        Never produce unwind table entries
     \\  -ferror-tracing           Enable error tracing in ReleaseFast mode
     \\  -fno-error-tracing        Disable error tracing in Debug and ReleaseSafe mode
@@ -1385,9 +1386,11 @@ fn buildOutputType(
                     } else if (mem.eql(u8, arg, "-fno-lto")) {
                         create_module.opts.lto = false;
                     } else if (mem.eql(u8, arg, "-funwind-tables")) {
-                        mod_opts.unwind_tables = true;
+                        mod_opts.unwind_tables = .sync;
+                    } else if (mem.eql(u8, arg, "-fasync-unwind-tables")) {
+                        mod_opts.unwind_tables = .@"async";
                     } else if (mem.eql(u8, arg, "-fno-unwind-tables")) {
-                        mod_opts.unwind_tables = false;
+                        mod_opts.unwind_tables = .none;
                     } else if (mem.eql(u8, arg, "-fstack-check")) {
                         mod_opts.stack_check = true;
                     } else if (mem.eql(u8, arg, "-fno-stack-check")) {
@@ -1973,8 +1976,27 @@ fn buildOutputType(
                         }
                     },
                     .no_stack_protector => mod_opts.stack_protector = 0,
-                    .unwind_tables => mod_opts.unwind_tables = true,
-                    .no_unwind_tables => mod_opts.unwind_tables = false,
+                    // The way these unwind table options are processed in GCC and Clang is crazy
+                    // convoluted, and we also don't know the target triple here, so this is all
+                    // best-effort.
+                    .unwind_tables => if (mod_opts.unwind_tables) |uwt| switch (uwt) {
+                        .none => {
+                            mod_opts.unwind_tables = .sync;
+                        },
+                        .sync, .@"async" => {},
+                    } else {
+                        mod_opts.unwind_tables = .sync;
+                    },
+                    .no_unwind_tables => mod_opts.unwind_tables = .none,
+                    .asynchronous_unwind_tables => mod_opts.unwind_tables = .@"async",
+                    .no_asynchronous_unwind_tables => if (mod_opts.unwind_tables) |uwt| switch (uwt) {
+                        .none, .sync => {},
+                        .@"async" => {
+                            mod_opts.unwind_tables = .sync;
+                        },
+                    } else {
+                        mod_opts.unwind_tables = .sync;
+                    },
                     .nostdlib => {
                         create_module.opts.ensure_libc_on_non_freestanding = false;
                         create_module.opts.ensure_libcpp_on_non_freestanding = false;
@@ -2788,8 +2810,15 @@ fn buildOutputType(
             create_module.opts.any_sanitize_thread = true;
         if (mod_opts.fuzz == true)
             create_module.opts.any_fuzz = true;
-        if (mod_opts.unwind_tables == true)
-            create_module.opts.any_unwind_tables = true;
+        if (mod_opts.unwind_tables) |uwt| switch (uwt) {
+            .none => {},
+            .sync => if (create_module.opts.any_unwind_tables == .none) {
+                create_module.opts.any_unwind_tables = .sync;
+            },
+            .@"async" => {
+                create_module.opts.any_unwind_tables = .@"async";
+            },
+        };
         if (mod_opts.strip == false)
             create_module.opts.any_non_stripped = true;
         if (mod_opts.error_tracing == true)
@@ -5713,6 +5742,8 @@ pub const ClangArgIterator = struct {
         no_lto,
         unwind_tables,
         no_unwind_tables,
+        asynchronous_unwind_tables,
+        no_asynchronous_unwind_tables,
         nostdlib,
         nostdlib_cpp,
         shared,
@@ -7435,8 +7466,15 @@ fn handleModArg(
         create_module.opts.any_sanitize_thread = true;
     if (mod_opts.fuzz == true)
         create_module.opts.any_fuzz = true;
-    if (mod_opts.unwind_tables == true)
-        create_module.opts.any_unwind_tables = true;
+    if (mod_opts.unwind_tables) |uwt| switch (uwt) {
+        .none => {},
+        .sync => if (create_module.opts.any_unwind_tables == .none) {
+            create_module.opts.any_unwind_tables = .sync;
+        },
+        .@"async" => {
+            create_module.opts.any_unwind_tables = .@"async";
+        },
+    };
     if (mod_opts.strip == false)
         create_module.opts.any_non_stripped = true;
     if (mod_opts.error_tracing == true)
diff --git a/src/mingw.zig b/src/mingw.zig
index cdee9acb07..8473a7a93b 100644
--- a/src/mingw.zig
+++ b/src/mingw.zig
@@ -24,6 +24,10 @@ pub fn buildCrtFile(comp: *Compilation, crt_file: CrtFile, prog_node: std.Progre
     var arena_allocator = std.heap.ArenaAllocator.init(comp.gpa);
     defer arena_allocator.deinit();
     const arena = arena_allocator.allocator();
+    const target = comp.getTarget();
+
+    // The old 32-bit x86 variant of SEH doesn't use tables.
+    const unwind_tables: std.builtin.UnwindTables = if (target.cpu.arch != .x86) .@"async" else .none;
 
     switch (crt_file) {
         .crt2_o => {
@@ -41,7 +45,9 @@ pub fn buildCrtFile(comp: *Compilation, crt_file: CrtFile, prog_node: std.Progre
                     .owner = undefined,
                 },
             };
-            return comp.build_crt_file("crt2", .Obj, .@"mingw-w64 crt2.o", prog_node, &files, .{});
+            return comp.build_crt_file("crt2", .Obj, .@"mingw-w64 crt2.o", prog_node, &files, .{
+                .unwind_tables = unwind_tables,
+            });
         },
 
         .dllcrt2_o => {
@@ -56,7 +62,9 @@ pub fn buildCrtFile(comp: *Compilation, crt_file: CrtFile, prog_node: std.Progre
                     .owner = undefined,
                 },
             };
-            return comp.build_crt_file("dllcrt2", .Obj, .@"mingw-w64 dllcrt2.o", prog_node, &files, .{});
+            return comp.build_crt_file("dllcrt2", .Obj, .@"mingw-w64 dllcrt2.o", prog_node, &files, .{
+                .unwind_tables = unwind_tables,
+            });
         },
 
         .mingw32_lib => {
@@ -73,7 +81,6 @@ pub fn buildCrtFile(comp: *Compilation, crt_file: CrtFile, prog_node: std.Progre
                     .owner = undefined,
                 });
             }
-            const target = comp.getTarget();
             if (target.cpu.arch == .x86 or target.cpu.arch == .x86_64) {
                 for (mingw32_x86_src) |dep| {
                     try c_source_files.append(.{
@@ -118,7 +125,9 @@ pub fn buildCrtFile(comp: *Compilation, crt_file: CrtFile, prog_node: std.Progre
             } else {
                 @panic("unsupported arch");
             }
-            return comp.build_crt_file("mingw32", .Lib, .@"mingw-w64 mingw32.lib", prog_node, c_source_files.items, .{});
+            return comp.build_crt_file("mingw32", .Lib, .@"mingw-w64 mingw32.lib", prog_node, c_source_files.items, .{
+                .unwind_tables = unwind_tables,
+            });
         },
     }
 }
diff --git a/src/target.zig b/src/target.zig
index a1c9a19724..37f2cd50da 100644
--- a/src/target.zig
+++ b/src/target.zig
@@ -4,6 +4,7 @@ const assert = std.debug.assert;
 const Type = @import("Type.zig");
 const AddressSpace = std.builtin.AddressSpace;
 const Alignment = @import("InternPool.zig").Alignment;
+const Compilation = @import("Compilation.zig");
 const Feature = @import("Zcu.zig").Feature;
 
 pub const default_stack_protector_buffer_size = 4;
@@ -408,8 +409,16 @@ pub fn clangSupportsNoImplicitFloatArg(target: std.Target) bool {
     };
 }
 
-pub fn needUnwindTables(target: std.Target) bool {
-    return target.os.tag == .windows or target.isDarwin() or std.debug.Dwarf.abi.supportsUnwinding(target);
+pub fn needUnwindTables(target: std.Target, libunwind: bool, libtsan: bool) std.builtin.UnwindTables {
+    if (target.os.tag == .windows) {
+        // The old 32-bit x86 variant of SEH doesn't use tables.
+        return if (target.cpu.arch != .x86) .@"async" else .none;
+    }
+    if (target.os.tag.isDarwin()) return .@"async";
+    if (libunwind) return .@"async";
+    if (libtsan) return .@"async";
+    if (std.debug.Dwarf.abi.supportsUnwinding(target)) return .@"async";
+    return .none;
 }
 
 pub fn defaultAddressSpace(
diff --git a/test/standalone/stack_iterator/build.zig b/test/standalone/stack_iterator/build.zig
index ac9a676930..38f66edd9f 100644
--- a/test/standalone/stack_iterator/build.zig
+++ b/test/standalone/stack_iterator/build.zig
@@ -23,7 +23,7 @@ pub fn build(b: *std.Build) void {
             .root_source_file = b.path("unwind.zig"),
             .target = target,
             .optimize = optimize,
-            .unwind_tables = if (target.result.isDarwin()) true else null,
+            .unwind_tables = if (target.result.isDarwin()) .@"async" else null,
             .omit_frame_pointer = false,
         });
 
@@ -46,7 +46,7 @@ pub fn build(b: *std.Build) void {
             .root_source_file = b.path("unwind.zig"),
             .target = target,
             .optimize = optimize,
-            .unwind_tables = true,
+            .unwind_tables = .@"async",
             .omit_frame_pointer = true,
         });
 
@@ -85,7 +85,7 @@ pub fn build(b: *std.Build) void {
             .root_source_file = b.path("shared_lib_unwind.zig"),
             .target = target,
             .optimize = optimize,
-            .unwind_tables = if (target.result.isDarwin()) true else null,
+            .unwind_tables = if (target.result.isDarwin()) .@"async" else null,
             .omit_frame_pointer = true,
         });
 
diff --git a/tools/update_clang_options.zig b/tools/update_clang_options.zig
index 637c9a5eaf..9cc0ad90cd 100644
--- a/tools/update_clang_options.zig
+++ b/tools/update_clang_options.zig
@@ -110,6 +110,14 @@ const known_options = [_]KnownOpt{
         .name = "fno-unwind-tables",
         .ident = "no_unwind_tables",
     },
+    .{
+        .name = "fasynchronous-unwind-tables",
+        .ident = "asynchronous_unwind_tables",
+    },
+    .{
+        .name = "fno-asynchronous-unwind-tables",
+        .ident = "no_asynchronous_unwind_tables",
+    },
     .{
         .name = "nolibc",
         .ident = "nostdlib",

From 43b6bd42434cdc71e3405b4d5c3a36f6ff76ed01 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Tue, 12 Nov 2024 18:06:42 +0100
Subject: [PATCH 3/6] start: Zero the link and frame pointer registers on all
 architectures.

---
 lib/std/start.zig | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/lib/std/start.zig b/lib/std/start.zig
index 0ded8ea625..39bea44039 100644
--- a/lib/std/start.zig
+++ b/lib/std/start.zig
@@ -279,8 +279,10 @@ fn _start() callconv(.naked) noreturn {
             ,
             .arm, .armeb, .thumb, .thumbeb =>
             // Note that this code must work for Thumb-1.
+            // r7 = FP (local), r11 = FP (unwind)
             \\ movs v1, #0
-            \\ mov fp, v1
+            \\ mov r7, v1
+            \\ mov r11, v1
             \\ mov lr, v1
             \\ mov a1, sp
             \\ subs v1, #16
@@ -290,20 +292,23 @@ fn _start() callconv(.naked) noreturn {
             ,
             .csky =>
             // The CSKY ABI assumes that `gb` is set to the address of the GOT in order for
-            // position-independent code to work. We depend on this in `std.os.linux.start_pie`
-            // to locate `_DYNAMIC` as well.
+            // position-independent code to work. We depend on this in `std.os.linux.pie` to locate
+            // `_DYNAMIC` as well.
+            // r8 = FP
             \\ grs t0, 1f
             \\ 1:
             \\ lrw gb, 1b@GOTPC
             \\ addu gb, t0
+            \\ movi r8, 0
             \\ movi lr, 0
             \\ mov a0, sp
             \\ andi sp, sp, -8
             \\ jmpi %[posixCallMainAndExit]
             ,
             .hexagon =>
-            // r29 = SP, r30 = FP
+            // r29 = SP, r30 = FP, r31 = LR
             \\ r30 = #0
+            \\ r31 = #0
             \\ r0 = r29
             \\ r29 = and(r29, #-16)
             \\ memw(r29 + #-8) = r29
@@ -312,12 +317,13 @@ fn _start() callconv(.naked) noreturn {
             ,
             .loongarch32, .loongarch64 =>
             \\ move $fp, $zero
+            \\ move $ra, $zero
             \\ move $a0, $sp
             \\ bstrins.d $sp, $zero, 3, 0
             \\ b %[posixCallMainAndExit]
             ,
             .riscv32, .riscv64 =>
-            \\ li s0, 0
+            \\ li fp, 0
             \\ li ra, 0
             \\ mv a0, sp
             \\ andi sp, sp, -16
@@ -371,28 +377,35 @@ fn _start() callconv(.naked) noreturn {
             ,
             .powerpc, .powerpcle =>
             // Set up the initial stack frame, and clear the back chain pointer.
+            // r1 = SP, r31 = FP
             \\ mr 3, 1
             \\ clrrwi 1, 1, 4
             \\ li 0, 0
             \\ stwu 1, -16(1)
             \\ stw 0, 0(1)
+            \\ li 31, 0
             \\ mtlr 0
             \\ b %[posixCallMainAndExit]
             ,
             .powerpc64, .powerpc64le =>
             // Set up the ToC and initial stack frame, and clear the back chain pointer.
+            // r1 = SP, r2 = ToC, r31 = FP
             \\ addis 2, 12, .TOC. - %[_start]@ha
             \\ addi 2, 2, .TOC. - %[_start]@l
             \\ mr 3, 1
             \\ clrrdi 1, 1, 4
             \\ li 0, 0
             \\ stdu 0, -32(1)
+            \\ li 31, 0
             \\ mtlr 0
             \\ b %[posixCallMainAndExit]
             \\ nop
             ,
             .s390x =>
             // Set up the stack frame (register save area and cleared back-chain slot).
+            // r11 = FP, r14 = LR, r15 = SP
+            \\ lghi %%r11, 0
+            \\ lghi %%r14, 0
             \\ lgr %%r2, %%r15
             \\ lghi %%r0, -16
             \\ ngr %%r15, %%r0
@@ -403,7 +416,9 @@ fn _start() callconv(.naked) noreturn {
             ,
             .sparc =>
             // argc is stored after a register window (16 registers * 4 bytes).
+            // i7 = LR
             \\ mov %%g0, %%fp
+            \\ mov %%g0, %%i7
             \\ add %%sp, 64, %%o0
             \\ and %%sp, -8, %%sp
             \\ ba,a %[posixCallMainAndExit]
@@ -411,7 +426,9 @@ fn _start() callconv(.naked) noreturn {
             .sparc64 =>
             // argc is stored after a register window (16 registers * 8 bytes) plus the stack bias
             // (2047 bytes).
+            // i7 = LR
             \\ mov %%g0, %%fp
+            \\ mov %%g0, %%i7
             \\ add %%sp, 2175, %%o0
             \\ add %%sp, 2047, %%sp
             \\ and %%sp, -16, %%sp

From 7d0087707634028308d3a870883249bfa59d94b8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Tue, 12 Nov 2024 17:39:59 +0100
Subject: [PATCH 4/6] start: Extend DWARF unwinding protection to more
 architectures.

The function is not marked .cantunwind for Arm/Thumb because of an LLVM
assembler bug: https://github.com/llvm/llvm-project/issues/115891
---
 lib/std/start.zig | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/lib/std/start.zig b/lib/std/start.zig
index 39bea44039..9da0cb2ec6 100644
--- a/lib/std/start.zig
+++ b/lib/std/start.zig
@@ -230,6 +230,29 @@ fn _start() callconv(.naked) noreturn {
         );
     }
 
+    // This is the first userspace frame. Prevent DWARF-based unwinders from unwinding further. We
+    // prevent FP-based unwinders from unwinding further by zeroing the register further below.
+    asm volatile (switch (native_arch) {
+            .arc => ".cfi_undefined blink",
+            .arm, .armeb, .thumb, .thumbeb => "", // https://github.com/llvm/llvm-project/issues/115891
+            .aarch64, .aarch64_be => ".cfi_undefined lr",
+            .csky => ".cfi_undefined lr",
+            .hexagon => ".cfi_undefined r31",
+            .loongarch32, .loongarch64 => ".cfi_undefined 1",
+            .m68k => ".cfi_undefined pc",
+            .mips, .mipsel, .mips64, .mips64el => ".cfi_undefined $ra",
+            .powerpc, .powerpcle, .powerpc64, .powerpc64le => ".cfi_undefined lr",
+            .riscv32, .riscv64 => if (builtin.zig_backend == .stage2_riscv64)
+                ""
+            else
+                ".cfi_undefined ra",
+            .s390x => ".cfi_undefined %%r14",
+            .sparc, .sparc64 => ".cfi_undefined %%i7",
+            .x86 => ".cfi_undefined %%eip",
+            .x86_64 => ".cfi_undefined %%rip",
+            else => @compileError("unsupported arch"),
+        });
+
     // Move this to the riscv prong below when this is resolved: https://github.com/ziglang/zig/issues/20918
     if (builtin.cpu.arch.isRISCV() and builtin.zig_backend != .stage2_riscv64) asm volatile (
         \\ .weak __global_pointer$
@@ -247,7 +270,6 @@ fn _start() callconv(.naked) noreturn {
     // linker explicitly.
     asm volatile (switch (native_arch) {
             .x86_64 =>
-            \\ .cfi_undefined %%rip
             \\ xorl %%ebp, %%ebp
             \\ movq %%rsp, %%rdi
             \\ andq $-16, %%rsp

From da018f972619377e8c044c5c27ebf231be262bb3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Mon, 4 Nov 2024 18:30:36 +0100
Subject: [PATCH 5/6] std.os.linux: Add unwinding protection in clone()
 implementations.

Whatever was in the frame pointer register prior to clone() will no longer be
valid in the child process, so zero it to protect FP-based unwinders. Similarly,
mark the link register as undefined to protect DWARF-based unwinders.

This is only zeroing the frame pointer(s) on Arm/Thumb because of an LLVM
assembler bug: https://github.com/llvm/llvm-project/issues/115891
---
 lib/std/os/linux/aarch64.zig     |  7 +++++-
 lib/std/os/linux/arm.zig         | 11 ++++++---
 lib/std/os/linux/hexagon.zig     |  4 ++++
 lib/std/os/linux/loongarch64.zig |  4 ++++
 lib/std/os/linux/mips.zig        |  4 ++++
 lib/std/os/linux/mips64.zig      |  4 ++++
 lib/std/os/linux/powerpc.zig     | 40 ++++++++++++++++----------------
 lib/std/os/linux/powerpc64.zig   |  7 +++++-
 lib/std/os/linux/riscv32.zig     |  6 ++++-
 lib/std/os/linux/riscv64.zig     |  6 ++++-
 lib/std/os/linux/s390x.zig       |  7 +++++-
 lib/std/os/linux/sparc64.zig     | 21 ++++++++++-------
 lib/std/os/linux/x86.zig         | 19 ++++++++-------
 lib/std/os/linux/x86_64.zig      |  2 ++
 14 files changed, 98 insertions(+), 44 deletions(-)

diff --git a/lib/std/os/linux/aarch64.zig b/lib/std/os/linux/aarch64.zig
index 9248360ae9..db304a3a33 100644
--- a/lib/std/os/linux/aarch64.zig
+++ b/lib/std/os/linux/aarch64.zig
@@ -120,8 +120,13 @@ pub fn clone() callconv(.Naked) usize {
         \\      cbz x0,1f
         \\      // parent
         \\      ret
+        \\
         \\      // child
-        \\1:    ldp x1,x0,[sp],#16
+        \\1:    .cfi_undefined lr
+        \\      mov fp, 0
+        \\      mov lr, 0
+        \\
+        \\      ldp x1,x0,[sp],#16
         \\      blr x1
         \\      mov x8,#93 // SYS_exit
         \\      svc #0
diff --git a/lib/std/os/linux/arm.zig b/lib/std/os/linux/arm.zig
index 1d22b8c3db..e9263b5cea 100644
--- a/lib/std/os/linux/arm.zig
+++ b/lib/std/os/linux/arm.zig
@@ -120,11 +120,16 @@ pub fn clone() callconv(.Naked) usize {
         \\    ldmfd sp!,{r4,r5,r6,r7}
         \\    bx lr
         \\
-        \\1:  mov r0,r6
+        \\    // https://github.com/llvm/llvm-project/issues/115891
+        \\1:  mov r7, #0
+        \\    mov r11, #0
+        \\    mov lr, #0
+        \\
+        \\    mov r0,r6
         \\    bl 3f
-        \\2:  mov r7,#1 // SYS_exit
+        \\    mov r7,#1 // SYS_exit
         \\    svc 0
-        \\    b 2b
+        \\
         \\3:  bx r5
     );
 }
diff --git a/lib/std/os/linux/hexagon.zig b/lib/std/os/linux/hexagon.zig
index e9bf9ab57c..0839ea8297 100644
--- a/lib/std/os/linux/hexagon.zig
+++ b/lib/std/os/linux/hexagon.zig
@@ -118,6 +118,10 @@ pub fn clone() callconv(.Naked) usize {
         \\ p0 = cmp.eq(r0, #0)
         \\ if (!p0) dealloc_return
         \\
+        \\ .cfi_undefined r31
+        \\ r30 = #0
+        \\ r31 = #0
+        \\
         \\ r0 = r10
         \\ callr r11
         \\
diff --git a/lib/std/os/linux/loongarch64.zig b/lib/std/os/linux/loongarch64.zig
index def3915494..b52f1d10b1 100644
--- a/lib/std/os/linux/loongarch64.zig
+++ b/lib/std/os/linux/loongarch64.zig
@@ -121,6 +121,10 @@ pub fn clone() callconv(.Naked) usize {
         \\ beqz    $a0, 1f         # whether child process
         \\ jirl    $zero, $ra, 0   # parent process return
         \\1:
+        \\ .cfi_undefined 1
+        \\ move    $fp, $zero
+        \\ move    $ra, $zero
+        \\
         \\ ld.d    $t8, $sp, 0     # function pointer
         \\ ld.d    $a0, $sp, 8     # argument pointer
         \\ jirl    $ra, $t8, 0     # call the user's function
diff --git a/lib/std/os/linux/mips.zig b/lib/std/os/linux/mips.zig
index e6cb5f7900..5d786ccde7 100644
--- a/lib/std/os/linux/mips.zig
+++ b/lib/std/os/linux/mips.zig
@@ -231,6 +231,10 @@ pub fn clone() callconv(.Naked) usize {
         \\  jr $ra
         \\  nop
         \\1:
+        \\  .cfi_undefined $ra
+        \\  move $fp, $zero
+        \\  move $ra, $zero
+        \\
         \\  lw $25, 0($sp)
         \\  lw $4, 4($sp)
         \\  jalr $25
diff --git a/lib/std/os/linux/mips64.zig b/lib/std/os/linux/mips64.zig
index 5e6661eae5..256c911bbe 100644
--- a/lib/std/os/linux/mips64.zig
+++ b/lib/std/os/linux/mips64.zig
@@ -210,6 +210,10 @@ pub fn clone() callconv(.Naked) usize {
         \\ jr $ra
         \\ nop
         \\1:
+        \\ .cfi_undefined $ra
+        \\ move $fp, $zero
+        \\ move $ra, $zero
+        \\
         \\ ld $25, 0($sp)
         \\ ld $4, 8($sp)
         \\ jalr $25
diff --git a/lib/std/os/linux/powerpc.zig b/lib/std/os/linux/powerpc.zig
index 7b56b94823..9dde326e1b 100644
--- a/lib/std/os/linux/powerpc.zig
+++ b/lib/std/os/linux/powerpc.zig
@@ -133,14 +133,14 @@ pub fn clone() callconv(.Naked) usize {
     // syscall(SYS_clone, flags, stack, ptid, tls, ctid)
     //         0          3,     4,     5,    6,   7
     asm volatile (
-        \\ # store non-volatile regs r30, r31 on stack in order to put our
+        \\ # store non-volatile regs r29, r30 on stack in order to put our
         \\ # start func and its arg there
-        \\ stwu 30, -16(1)
-        \\ stw 31, 4(1)
+        \\ stwu 29, -16(1)
+        \\ stw 30, 4(1)
         \\
-        \\ # save r3 (func) into r30, and r6(arg) into r31
-        \\ mr 30, 3
-        \\ mr 31, 6
+        \\ # save r3 (func) into r29, and r6(arg) into r30
+        \\ mr 29, 3
+        \\ mr 30, 6
         \\
         \\ # create initial stack frame for new thread
         \\ clrrwi 4, 4, 4
@@ -167,28 +167,28 @@ pub fn clone() callconv(.Naked) usize {
         \\ # compare sc result with 0
         \\ cmpwi cr7, 3, 0
         \\
-        \\ # if not 0, jump to end
-        \\ bne cr7, 2f
+        \\ # if not 0, restore stack and return
+        \\ beq cr7, 2f
+        \\ lwz 29, 0(1)
+        \\ lwz 30, 4(1)
+        \\ addi 1, 1, 16
+        \\ blr
         \\
         \\ #else: we're the child
+        \\ 2:
+        \\ .cfi_undefined lr
+        \\ li 31, 0
+        \\ mtlr 0
+        \\
         \\ #call funcptr: move arg (d) into r3
-        \\ mr 3, 31
-        \\ #move r30 (funcptr) into CTR reg
-        \\ mtctr 30
+        \\ mr 3, 30
+        \\ #move r29 (funcptr) into CTR reg
+        \\ mtctr 29
         \\ # call CTR reg
         \\ bctrl
         \\ # mov SYS_exit into r0 (the exit param is already in r3)
         \\ li 0, 1
         \\ sc
-        \\
-        \\ 2:
-        \\
-        \\ # restore stack
-        \\ lwz 30, 0(1)
-        \\ lwz 31, 4(1)
-        \\ addi 1, 1, 16
-        \\
-        \\ blr
     );
 }
 
diff --git a/lib/std/os/linux/powerpc64.zig b/lib/std/os/linux/powerpc64.zig
index 06b67c17f1..6a1f98a65f 100644
--- a/lib/std/os/linux/powerpc64.zig
+++ b/lib/std/os/linux/powerpc64.zig
@@ -160,7 +160,12 @@ pub fn clone() callconv(.Naked) usize {
         \\  cmpwi cr7, 3, 0
         \\  bnelr cr7
         \\
-        \\  # we're the child. call fn(arg)
+        \\  # we're the child
+        \\  .cfi_undefined lr
+        \\  li    31, 0
+        \\  mtlr   0
+        \\
+        \\  # call fn(arg)
         \\  ld     3, 16(1)
         \\  ld    12,  8(1)
         \\  mtctr 12
diff --git a/lib/std/os/linux/riscv32.zig b/lib/std/os/linux/riscv32.zig
index 457d7e50b4..dc444a1956 100644
--- a/lib/std/os/linux/riscv32.zig
+++ b/lib/std/os/linux/riscv32.zig
@@ -120,7 +120,11 @@ pub fn clone() callconv(.Naked) usize {
         \\    ret
         \\
         \\    # Child
-        \\1:  lw a1, 0(sp)
+        \\1:  .cfi_undefined ra
+        \\    mv fp, zero
+        \\    mv ra, zero
+        \\
+        \\    lw a1, 0(sp)
         \\    lw a0, 4(sp)
         \\    jalr a1
         \\
diff --git a/lib/std/os/linux/riscv64.zig b/lib/std/os/linux/riscv64.zig
index e33169c5b1..45ba568c1b 100644
--- a/lib/std/os/linux/riscv64.zig
+++ b/lib/std/os/linux/riscv64.zig
@@ -120,7 +120,11 @@ pub fn clone() callconv(.Naked) usize {
         \\    ret
         \\
         \\    # Child
-        \\1:  ld a1, 0(sp)
+        \\1:  .cfi_undefined ra
+        \\    mv fp, zero
+        \\    mv ra, zero
+        \\
+        \\    ld a1, 0(sp)
         \\    ld a0, 8(sp)
         \\    jalr a1
         \\
diff --git a/lib/std/os/linux/s390x.zig b/lib/std/os/linux/s390x.zig
index efc48af4ff..8fbe1c930b 100644
--- a/lib/std/os/linux/s390x.zig
+++ b/lib/std/os/linux/s390x.zig
@@ -133,7 +133,12 @@ pub fn clone() callconv(.Naked) usize {
         \\ltgr %%r2, %%r2
         \\bnzr %%r14
         \\
-        \\# we're the child. call fn(arg)
+        \\# we're the child
+        \\.cfi_undefined %%r14
+        \\lghi %%r11, 0
+        \\lghi %%r14, 0
+        \\
+        \\# call fn(arg)
         \\lg   %%r1,  8(%%r15)
         \\lg   %%r2, 16(%%r15)
         \\basr %%r14, %%r1
diff --git a/lib/std/os/linux/sparc64.zig b/lib/std/os/linux/sparc64.zig
index c146ed17cf..d81e6fb40a 100644
--- a/lib/std/os/linux/sparc64.zig
+++ b/lib/std/os/linux/sparc64.zig
@@ -198,29 +198,34 @@ pub fn clone() callconv(.Naked) usize {
         \\ mov %%i5, %%o3
         \\ ldx [%%fp + 0x8af], %%o4
         \\ t 0x6d
-        \\ bcs,pn %%xcc, 2f
+        \\ bcs,pn %%xcc, 1f
         \\ nop
         \\ # The child pid is returned in o0 while o1 tells if this
         \\ # process is # the child (=1) or the parent (=0).
-        \\ brnz %%o1, 1f
+        \\ brnz %%o1, 2f
         \\ nop
         \\ # Parent process, return the child pid
         \\ mov %%o0, %%i0
         \\ ret
         \\ restore
         \\1:
-        \\ # Child process, call func(arg)
+        \\ # The syscall failed
+        \\ sub %%g0, %%o0, %%i0
+        \\ ret
+        \\ restore
+        \\2:
+        \\ # Child process
+        \\ .cfi_undefined %%i7
+        \\ mov %%g0, %%fp
+        \\ mov %%g0, %%i7
+        \\
+        \\ # call func(arg)
         \\ mov %%g0, %%fp
         \\ call %%g2
         \\ mov %%g3, %%o0
         \\ # Exit
         \\ mov 1, %%g1 // SYS_exit
         \\ t 0x6d
-        \\2:
-        \\ # The syscall failed
-        \\ sub %%g0, %%o0, %%i0
-        \\ ret
-        \\ restore
     );
 }
 
diff --git a/lib/std/os/linux/x86.zig b/lib/std/os/linux/x86.zig
index abcfb99b37..cb746e52a8 100644
--- a/lib/std/os/linux/x86.zig
+++ b/lib/std/os/linux/x86.zig
@@ -148,19 +148,22 @@ pub fn clone() callconv(.Naked) usize {
         \\  movl $120,%%eax // SYS_clone
         \\  int $128
         \\  testl %%eax,%%eax
-        \\  jnz 1f
-        \\  popl %%eax
-        \\  xorl %%ebp,%%ebp
-        \\  calll *%%eax
-        \\  movl %%eax,%%ebx
-        \\  movl $1,%%eax // SYS_exit
-        \\  int $128
-        \\1:
+        \\  jz 1f
         \\  popl %%edi
         \\  popl %%esi
         \\  popl %%ebx
         \\  popl %%ebp
         \\  retl
+        \\
+        \\1:
+        \\  .cfi_undefined %%eip
+        \\  xorl %%ebp,%%ebp
+        \\
+        \\  popl %%eax
+        \\  calll *%%eax
+        \\  movl %%eax,%%ebx
+        \\  movl $1,%%eax // SYS_exit
+        \\  int $128
     );
 }
 
diff --git a/lib/std/os/linux/x86_64.zig b/lib/std/os/linux/x86_64.zig
index cef15105ee..44a37345f0 100644
--- a/lib/std/os/linux/x86_64.zig
+++ b/lib/std/os/linux/x86_64.zig
@@ -116,8 +116,10 @@ pub fn clone() callconv(.Naked) usize {
         \\      testq %%rax,%%rax
         \\      jz 1f
         \\      retq
+        \\
         \\1:    .cfi_undefined %%rip
         \\      xorl %%ebp,%%ebp
+        \\
         \\      popq %%rdi
         \\      callq *%%r9
         \\      movl %%eax,%%edi

From c666ebb1f8aac440a4d0d554e9f8aa836bf58060 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Wed, 13 Nov 2024 09:18:37 +0100
Subject: [PATCH 6/6] musl: Add unwinding protection in clone()
 implementations.

Whatever was in the frame pointer register prior to clone() will no longer be
valid in the child process, so zero it to protect FP-based unwinders. This is
just an extension of what was already done for i386 and x86_64. Only applied
to architectures where the _start() code also zeroes the frame pointer.
---
 lib/libc/musl/src/thread/aarch64/clone.s     |  3 ++-
 lib/libc/musl/src/thread/arm/clone.s         |  3 ++-
 lib/libc/musl/src/thread/i386/clone.s        | 17 ++++++++--------
 lib/libc/musl/src/thread/loongarch64/clone.s |  1 +
 lib/libc/musl/src/thread/m68k/clone.s        |  3 ++-
 lib/libc/musl/src/thread/microblaze/clone.s  |  3 ++-
 lib/libc/musl/src/thread/mips/clone.s        |  3 ++-
 lib/libc/musl/src/thread/mips64/clone.s      |  3 ++-
 lib/libc/musl/src/thread/mipsn32/clone.s     |  3 ++-
 lib/libc/musl/src/thread/or1k/clone.s        |  3 ++-
 lib/libc/musl/src/thread/powerpc/clone.s     | 21 +++++++++-----------
 lib/libc/musl/src/thread/x32/clone.s         |  6 +++---
 lib/libc/musl/src/thread/x86_64/clone.s      |  6 +++---
 13 files changed, 40 insertions(+), 35 deletions(-)

diff --git a/lib/libc/musl/src/thread/aarch64/clone.s b/lib/libc/musl/src/thread/aarch64/clone.s
index e3c83395ca..9ac272bde3 100644
--- a/lib/libc/musl/src/thread/aarch64/clone.s
+++ b/lib/libc/musl/src/thread/aarch64/clone.s
@@ -24,7 +24,8 @@ __clone:
 	// parent
 	ret
 	// child
-1:	ldp x1,x0,[sp],#16
+1:	mov fp, 0
+	ldp x1,x0,[sp],#16
 	blr x1
 	mov x8,#93 // SYS_exit
 	svc #0
diff --git a/lib/libc/musl/src/thread/arm/clone.s b/lib/libc/musl/src/thread/arm/clone.s
index bb0965dafe..4ff0c0e88b 100644
--- a/lib/libc/musl/src/thread/arm/clone.s
+++ b/lib/libc/musl/src/thread/arm/clone.s
@@ -19,7 +19,8 @@ __clone:
 	ldmfd sp!,{r4,r5,r6,r7}
 	bx lr
 
-1:	mov r0,r6
+1:	mov fp,#0
+	mov r0,r6
 	bl 3f
 2:	mov r7,#1
 	svc 0
diff --git a/lib/libc/musl/src/thread/i386/clone.s b/lib/libc/musl/src/thread/i386/clone.s
index e237d3c632..f89ddd9d53 100644
--- a/lib/libc/musl/src/thread/i386/clone.s
+++ b/lib/libc/musl/src/thread/i386/clone.s
@@ -30,9 +30,15 @@ __clone:
 	mov 8(%ebp),%ebp
 	int $128
 	test %eax,%eax
-	jnz 1f
+	jz 1f
+	add $16,%esp
+	pop %edi
+	pop %esi
+	pop %ebx
+	pop %ebp
+	ret
 
-	mov %ebp,%eax
+1:	mov %ebp,%eax
 	xor %ebp,%ebp
 	call *%eax
 	mov %eax,%ebx
@@ -40,10 +46,3 @@ __clone:
 	inc %eax
 	int $128
 	hlt
-
-1:	add $16,%esp
-	pop %edi
-	pop %esi
-	pop %ebx
-	pop %ebp
-	ret
diff --git a/lib/libc/musl/src/thread/loongarch64/clone.s b/lib/libc/musl/src/thread/loongarch64/clone.s
index a165b365a3..cb4aacfc6d 100644
--- a/lib/libc/musl/src/thread/loongarch64/clone.s
+++ b/lib/libc/musl/src/thread/loongarch64/clone.s
@@ -22,6 +22,7 @@ __clone:
 	beqz    $a0, 1f         # whether child process
 	jirl    $zero, $ra, 0   # parent process return
 1:
+	move    $fp, $zero
 	ld.d    $t8, $sp, 0     # function pointer
 	ld.d    $a0, $sp, 8     # argument pointer
 	jirl    $ra, $t8, 0     # call the user's function
diff --git a/lib/libc/musl/src/thread/m68k/clone.s b/lib/libc/musl/src/thread/m68k/clone.s
index f6dfa06f49..42ec19f724 100644
--- a/lib/libc/musl/src/thread/m68k/clone.s
+++ b/lib/libc/musl/src/thread/m68k/clone.s
@@ -18,7 +18,8 @@ __clone:
 	beq 1f
 	movem.l (%sp)+,%d2-%d5
 	rts
-1:	move.l %a1,-(%sp)
+1:	suba.l %%fp,%%fp
+	move.l %a1,-(%sp)
 	jsr (%a0)
 	move.l #1,%d0
 	trap #0
diff --git a/lib/libc/musl/src/thread/microblaze/clone.s b/lib/libc/musl/src/thread/microblaze/clone.s
index b68cc5fc22..64e3f0743f 100644
--- a/lib/libc/musl/src/thread/microblaze/clone.s
+++ b/lib/libc/musl/src/thread/microblaze/clone.s
@@ -22,7 +22,8 @@ __clone:
 	rtsd    r15, 8
 	nop
 
-1:	lwi     r3, r1, 0
+1:	add     r19, r0, r0
+	lwi     r3, r1, 0
 	lwi     r5, r1, 4
 	brald   r15, r3
 	nop
diff --git a/lib/libc/musl/src/thread/mips/clone.s b/lib/libc/musl/src/thread/mips/clone.s
index 0446338568..229b987e96 100644
--- a/lib/libc/musl/src/thread/mips/clone.s
+++ b/lib/libc/musl/src/thread/mips/clone.s
@@ -27,7 +27,8 @@ __clone:
 	addu $sp, $sp, 16
 	jr $ra
 	nop
-1:	lw $25, 0($sp)
+1:	move $fp, $0
+	lw $25, 0($sp)
 	lw $4, 4($sp)
 	jalr $25
 	nop
diff --git a/lib/libc/musl/src/thread/mips64/clone.s b/lib/libc/musl/src/thread/mips64/clone.s
index 2d86899a1d..8de3db6c4e 100644
--- a/lib/libc/musl/src/thread/mips64/clone.s
+++ b/lib/libc/musl/src/thread/mips64/clone.s
@@ -25,7 +25,8 @@ __clone:
 	nop
 	jr	$ra
 	nop
-1:	ld	$25, 0($sp)	# function pointer
+1:	move	$fp, $0
+	ld	$25, 0($sp)	# function pointer
 	ld	$4, 8($sp)	# argument pointer
 	jalr	$25		# call the user's function
 	nop
diff --git a/lib/libc/musl/src/thread/mipsn32/clone.s b/lib/libc/musl/src/thread/mipsn32/clone.s
index 4d3c8c7a25..9571231a62 100644
--- a/lib/libc/musl/src/thread/mipsn32/clone.s
+++ b/lib/libc/musl/src/thread/mipsn32/clone.s
@@ -25,7 +25,8 @@ __clone:
 	nop
 	jr	$ra
 	nop
-1:	lw	$25, 0($sp)	# function pointer
+1:	move	$fp, $0
+	lw	$25, 0($sp)	# function pointer
 	lw	$4, 4($sp)	# argument pointer
 	jalr	$25		# call the user's function
 	nop
diff --git a/lib/libc/musl/src/thread/or1k/clone.s b/lib/libc/musl/src/thread/or1k/clone.s
index 2473ac2040..05c55c6982 100644
--- a/lib/libc/musl/src/thread/or1k/clone.s
+++ b/lib/libc/musl/src/thread/or1k/clone.s
@@ -23,7 +23,8 @@ __clone:
 	l.jr	r9
 	 l.nop
 
-1:	l.lwz	r11, 0(r1)
+1:	l.ori	r2, r0, 0
+	l.lwz	r11, 0(r1)
 	l.jalr	r11
 	 l.lwz	r3, 4(r1)
 
diff --git a/lib/libc/musl/src/thread/powerpc/clone.s b/lib/libc/musl/src/thread/powerpc/clone.s
index da13f446c0..019fd62a95 100644
--- a/lib/libc/musl/src/thread/powerpc/clone.s
+++ b/lib/libc/musl/src/thread/powerpc/clone.s
@@ -48,9 +48,16 @@ neg 3, 3 #negate the result (errno)
 # compare sc result with 0
 cmpwi cr7, 3, 0
 
-# if not 0, jump to end
-bne cr7, 2f
+# if not 0, restore stack and return
+beq cr7, 2f
 
+lwz 30, 0(1)
+lwz 31, 4(1)
+addi 1, 1, 16
+
+blr
+
+2:
 #else: we're the child
 #call funcptr: move arg (d) into r3
 mr 3, 31
@@ -61,13 +68,3 @@ bctrl
 # mov SYS_exit into r0 (the exit param is already in r3)
 li 0, 1
 sc
-
-2:
-
-# restore stack
-lwz 30, 0(1)
-lwz 31, 4(1)
-addi 1, 1, 16
-
-blr
-
diff --git a/lib/libc/musl/src/thread/x32/clone.s b/lib/libc/musl/src/thread/x32/clone.s
index b870880f93..d713452676 100644
--- a/lib/libc/musl/src/thread/x32/clone.s
+++ b/lib/libc/musl/src/thread/x32/clone.s
@@ -15,12 +15,12 @@ __clone:
 	mov %rcx,(%rsi)
 	syscall
 	test %eax,%eax
-	jnz 1f
-	xor %ebp,%ebp
+	jz 1f
+	ret
+1:	xor %ebp,%ebp
 	pop %rdi
 	call *%r9
 	mov %eax,%edi
 	movl $0x4000003c,%eax /* SYS_exit */
 	syscall
 	hlt
-1:	ret
diff --git a/lib/libc/musl/src/thread/x86_64/clone.s b/lib/libc/musl/src/thread/x86_64/clone.s
index 6e47bc0a37..3c30220e50 100644
--- a/lib/libc/musl/src/thread/x86_64/clone.s
+++ b/lib/libc/musl/src/thread/x86_64/clone.s
@@ -16,8 +16,9 @@ __clone:
 	mov %rcx,(%rsi)
 	syscall
 	test %eax,%eax
-	jnz 1f
-	xor %ebp,%ebp
+	jz 1f
+	ret
+1:	xor %ebp,%ebp
 	pop %rdi
 	call *%r9
 	mov %eax,%edi
@@ -25,4 +26,3 @@ __clone:
 	mov $60,%al
 	syscall
 	hlt
-1:	ret