pprof_mac_fix: do not patch OS X 10.11 El Capitan

From the public beta, it appears that Apple fixed the bug.
Let's hope it stays fixed through to the actual release.

main.go

@@ -7,6 +7,15 @@
 // pprof_mac_fix applies a binary patch to the OS X kernel in order to make
 // pprof profiling report accurate values.
 //
+// Hooray Hooray Hooray
+//
+// The public beta of OS X 10.11 El Capitan appears to contain a fix for the
+// underlying kernel bug. It therefore appears that pprof_mac_fix is unnecessary
+// on that system: pprof will just work out of the box.
+//
+// If run on an OS X 10.11 system, pprof_mac_fix will report that the kernel
+// is already correct without any patch.
+//
 // Warning Warning Warning
 //
 // This program is meant to modify the operating system kernel, the program
@@ -209,6 +218,10 @@ func fixIt(k *kernel) {
 			fmt.Fprintf(os.Stderr, "kernel %s already patched; not rewriting\n", k.file)
 			os.Exit(2)
 		}
+		if len(errs) == 1 && errs[0] == errNoBug {
+			fmt.Fprintf(os.Stderr, "kernel %s works without any patch; not rewriting\n", k.file)
+			os.Exit(2)
+		}
 		fmt.Fprintf(os.Stderr, "unrecognized kernel: %s\n", k.file)
 		for _, err := range errs {
 			fmt.Fprintf(os.Stderr, "%s\n", err)
@@ -304,7 +317,7 @@ func fixAnyVersion(k *kernel) []error {
 	var errs []error
 	for _, f := range fixes {
 		err := f.apply(k.current_thread, k.bsd_ast)
-		if err == errPatched {
+		if err == errPatched || err == errNoBug {
 			return []error{err}
 		}
 		if err != nil {
@@ -316,7 +329,10 @@ func fixAnyVersion(k *kernel) []error {
 	return errs
 }
 
-var errPatched = fmt.Errorf("kernel already patched")
+var (
+	errPatched = fmt.Errorf("kernel already patched")
+	errNoBug   = fmt.Errorf("kernel is correct without patch - Apple fixed the bug!")
+)
 
 var updateText = `
 For an update, mail rsc@golang.org with the output printed by:
@@ -609,6 +625,9 @@ func (f *fix) apply(current_thread []byte, bsd_ast []byte) error {
 	}
 
 	var replace [][]byte
+	if f.version >= "15." && total == 2 && len(timers) == 1 && len(timers[0]) == 2 && strings.HasSuffix(f.version, "no bug") {
+		return errNoBug
+	}
 	if f.version >= "14." {
 		if total != 2 || len(timers) != 1 || len(timers[0]) != 2 {
 			return fmt.Errorf("cannot match bsd_ast 14 timer call %d %d", total, len(timers[0]))
@@ -1052,6 +1071,7 @@ var fixes = []*fix{
 	&fix_13_0_0_fixed,
 	&fix_14_0_0,
 	&fix_14_0_0_fixed,
+	&fix_15_0_0_nobug,
 }
 
 // Darwin 13.0.0 (Mavericks)

main_test.go

@@ -93,3 +93,22 @@ func gdbDisas(t *testing.T, file, name string) []byte {
 	}
 	return disas
 }
+
+var fixed = []string{
+	"testdata/mach_kernel_15_0_0",
+}
+
+func TestFixed(t *testing.T) {
+	for _, tt := range fixed {
+		k := loadKernel(tt)
+		errs := fixAnyVersion(k)
+		t.Log("%s: %v\n", tt, errs)
+		if len(errs) != 1 || errs[0] != errNoBug {
+			t.Errorf("%s: correct kernel not recognized", tt)
+			for _, err := range errs {
+				t.Errorf("%s", err)
+			}
+			continue
+		}
+	}
+}

rewrite.go

@@ -47,6 +47,21 @@ var bsd_ast_14_0_0_fixed = mustCompile(`
     0xe8 0x00/0x00 0x00/0x00 0x00/0x00 0x00/0x00 *  // 15 call psignal_internal
 `)
 
+var fix_15_0_0_nobug = fix{
+	"15.0.0 no bug",
+	current_thread_pop,
+	[]*pattern{bsd_ast_15_0_0_nobug},
+}
+
+var bsd_ast_15_0_0_nobug = mustCompile(`
+    * 0x31 0xf6                                     // 0 xor %esi, %esi
+    0xb9 0x08 0x00 0x00 0x00                        // 2 mov $0x8, %ecx
+    0x41 0xb8 0x1a/0xfe 0x00 0x00 0x00              // 7 mov $0x1a, %r8d [or $0x1b]
+    0x4c 0x89 0xe7                                  // 12 mov %r12, %rdi
+    0x4c 0x89 0xfa                                  // 15 mov %r15, %rdx
+    0xe8 0x00/0x00 0x00/0x00 0x00/0x00 0x00/0x00 *  // 18 call psignal_internal
+`)
+
 type Inst struct {
 	x86asm.Inst
 	Enc   []byte

testdata/Makefile

@@ -11,6 +11,7 @@ all: \
 	mach_kernel_13_0_0_fix \
 	mach_kernel_14_0_0 \
 	mach_kernel_14_0_0_fix \
+	mach_kernel_15_0_0 \
 
 %_i386: %_i386.s
 	gcc -m32 -o $*_i386 $*_i386.s