feat(debug): add named buffer allocation with pattern filling

debug/ptrace_linux_amd64.go

@@ -33,9 +33,17 @@ type Session struct {
 // JIT code, calls PTRACE_TRACEME and raises SIGSTOP; Launch waits for
 // that initial stop and returns a ready Session.
 func Launch(gasmBin, asmPath, funcName string, args []byte) (*Session, error) {
+	sess, _, err := LaunchWithBuffers(gasmBin, asmPath, funcName, args, "")
+	return sess, err
+}
+
+// LaunchWithBuffers is like Launch but also allocates buffers in the debuggee
+// based on the buffer specification.  Returns the Session and the buffer
+// addresses (in the order they appear in the spec).
+func LaunchWithBuffers(gasmBin, asmPath, funcName string, args []byte, bufSpec string) (*Session, []uint64, error) {
 	self, err := os.Executable()
 	if err != nil {
-		return nil, fmt.Errorf("debug: cannot find gasm binary: %w", err)
+		return nil, nil, fmt.Errorf("debug: cannot find gasm binary: %w", err)
 	}
 	if gasmBin != "" {
 		self = gasmBin
@@ -44,12 +52,20 @@ func Launch(gasmBin, asmPath, funcName string, args []byte) (*Session, error) {
 	// Write the arg block to a temp file (the child reads it).
 	tmpDir, err := os.MkdirTemp("", "gasm-debug-*")
 	if err != nil {
-		return nil, fmt.Errorf("debug: tempdir: %w", err)
+		return nil, nil, fmt.Errorf("debug: tempdir: %w", err)
 	}
 	argsFile := filepath.Join(tmpDir, "args.bin")
 	if err := os.WriteFile(argsFile, args, 0o644); err != nil {
 		os.RemoveAll(tmpDir)
-		return nil, fmt.Errorf("debug: write args: %w", err)
+		return nil, nil, fmt.Errorf("debug: write args: %w", err)
+	}
+
+	// Write the buffer spec if present.
+	if bufSpec != "" {
+		if err := os.WriteFile(filepath.Join(tmpDir, "bufspec"), []byte(bufSpec), 0o644); err != nil {
+			os.RemoveAll(tmpDir)
+			return nil, nil, fmt.Errorf("debug: write bufspec: %w", err)
+		}
 	}
 
 	cmd := exec.Command(self, "debug", "--target", "--func", funcName, "--args", argsFile, asmPath)
@@ -60,7 +76,7 @@ func Launch(gasmBin, asmPath, funcName string, args []byte) (*Session, error) {
 
 	if err := cmd.Start(); err != nil {
 		os.RemoveAll(tmpDir)
-		return nil, fmt.Errorf("debug: start debuggee: %w", err)
+		return nil, nil, fmt.Errorf("debug: start debuggee: %w", err)
 	}
 
 	s := &Session{pid: cmd.Process.Pid, cmd: cmd}
@@ -79,8 +95,28 @@ func Launch(gasmBin, asmPath, funcName string, args []byte) (*Session, error) {
 	if _, err := syscall.Wait4(s.pid, &ws, syscall.WUNTRACED, nil); err != nil {
 		cmd.Process.Kill()
 		os.RemoveAll(tmpDir)
-		return nil, fmt.Errorf("debug: wait for debuggee: %w", err)
+		return nil, nil, fmt.Errorf("debug: wait for stop: %w", err)
 	}
+
+	// Wait for the debuggee to reach the function entry point.
+	entryFile := filepath.Join(tmpDir, "entry")
+	for i := 0; i < 500; i++ {
+		if _, err := os.Stat(entryFile); err == nil {
+			break
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+
+	// Continue the debuggee to the entry point.
+	if err := s.Continue(); err != nil {
+		return nil, nil, fmt.Errorf("debug: continue to entry: %w", err)
+	}
+
+	// Wait for the entry stop.
+	if _, err := syscall.Wait4(s.pid, &ws, syscall.WUNTRACED, nil); err != nil {
+		return nil, nil, fmt.Errorf("debug: wait for entry: %w", err)
+	}
+
 	s.stopped = true
 
 	// Read the code base from /proc/pid/maps (find the RWX mapping).
@@ -93,7 +129,21 @@ func Launch(gasmBin, asmPath, funcName string, args []byte) (*Session, error) {
 		}
 	}
 
-	return s, nil
+	// Read buffer addresses if buffers were allocated.
+	var bufAddrs []uint64
+	if bufSpec != "" {
+		addrFile := filepath.Join(tmpDir, "bufaddrs")
+		if data, err := os.ReadFile(addrFile); err == nil {
+			for _, line := range strings.Split(strings.TrimSpace(string(data)), "\n") {
+				var addr uint64
+				if _, err := fmt.Sscanf(line, "%d", &addr); err == nil {
+					bufAddrs = append(bufAddrs, addr)
+				}
+			}
+		}
+	}
+
+	return s, bufAddrs, nil
 }
 
 // wait waits for the debuggee to stop and returns the wait status.