Merge pull request #22035 from alexrp/unwind-fixes

Better unwind table support + unwind protection in `_start()` and `clone()`

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

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

lib/libc/musl/src/thread/i386/clone.s

@@ -30,20 +30,19 @@ __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
 	xor %eax,%eax
 	inc %eax
 	int $128
 	hlt
-
-1:	add $16,%esp
-	pop %edi
-	pop %esi
-	pop %ebx
-	pop %ebp
-	ret

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

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

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

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

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

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

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)
 

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
-

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

lib/libc/musl/src/thread/x86_64/clone.s

@@ -16,13 +16,13 @@ __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
 	xor %eax,%eax
 	mov $60,%al
 	syscall
 	hlt
-1:	ret

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,

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"),

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 {

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

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
     );
 }

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
         \\

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

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

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