[lldb][lldb-server] Enable sending RegisterFlags as XML (#69951)

This adds ToXML methods to encode RegisterFlags and its fields into XML according to GDB's target XML format: https://sourceware.org/gdb/onlinedocs/gdb/Target-Description-Format.html#Target-Description-Format lldb-server does not use libXML to build XML, so this follows the existing code that uses strings. Indentation is used so the result is still human readable. ``` <flags id=\"Foo\" size=\"4\"> <field name=\"abc\" start=\"0\" end=\"0\"/> </flags> ``` This is used by lldb-server when building target XML, though no one sets any fields yet. That'll come in a later commit.

Author: DavidSpickett

lldb/include/lldb/Target/RegisterFlags.h

@@ -9,20 +9,21 @@
 #ifndef LLDB_TARGET_REGISTERFLAGS_H
 #define LLDB_TARGET_REGISTERFLAGS_H
 
-#include "lldb/Utility/Log.h"
+#include <string>
+#include <vector>
 
 namespace lldb_private {
 
+class StreamString;
+class Log;
+
 class RegisterFlags {
 public:
  class Field {
  public:
  /// Where start is the least significant bit and end is the most
  /// significant bit. The start bit must be <= the end bit.
- Field(std::string name, unsigned start, unsigned end)
- : m_name(std::move(name)), m_start(start), m_end(end) {
- assert(m_start <= m_end && "Start bit must be <= end bit.");
- }
+ Field(std::string name, unsigned start, unsigned end);
 
  /// Construct a field that occupies a single bit.
  Field(std::string name, unsigned bit_position)
@@ -51,6 +52,11 @@ class RegisterFlags {
  /// covered by either field.
  unsigned PaddingDistance(const Field &other) const;
 
+ /// Output XML that describes this field, to be inserted into a target XML
+ /// file. Reserved characters in field names like "<" are replaced with
+ /// their XML safe equivalents like "&gt;".
+ void ToXML(StreamString &strm) const;
+
  bool operator<(const Field &rhs) const {
  return GetStart() < rhs.GetStart();
  }
@@ -106,6 +112,9 @@ class RegisterFlags {
  /// be split into many tables as needed.
  std::string AsTable(uint32_t max_width) const;
 
+ // Output XML that describes this set of flags.
+ void ToXML(StreamString &strm) const;
+
 private:
  const std::string m_id;
  /// Size in bytes

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp

@@ -3094,6 +3094,12 @@ GDBRemoteCommunicationServerLLGS::BuildTargetXml() {
  continue;
  }
 
+ if (reg_info->flags_type) {
+ response.IndentMore();
+ reg_info->flags_type->ToXML(response);
+ response.IndentLess();
+ }
+
  response.Indent();
  response.Printf("<reg name=\"%s\" bitsize=\"%" PRIu32
  "\" regnum=\"%d\" ",
@@ -3113,6 +3119,9 @@ GDBRemoteCommunicationServerLLGS::BuildTargetXml() {
  if (!format.empty())
  response << "format=\"" << format << "\" ";
 
+ if (reg_info->flags_type)
+ response << "type=\"" << reg_info->flags_type->GetID() << "\" ";
+
  const char *const register_set_name =
  reg_context.GetRegisterSetNameForRegisterAtIndex(reg_index);
  if (register_set_name)

lldb/source/Target/RegisterFlags.cpp

@@ -7,13 +7,21 @@
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Target/RegisterFlags.h"
+#include "lldb/Utility/Log.h"
 #include "lldb/Utility/StreamString.h"
 
+#include "llvm/ADT/StringExtras.h"
+
 #include <numeric>
 #include <optional>
 
 using namespace lldb_private;
 
+RegisterFlags::Field::Field(std::string name, unsigned start, unsigned end)
+ : m_name(std::move(name)), m_start(start), m_end(end) {
+ assert(m_start <= m_end && "Start bit must be <= end bit.");
+}
+
 void RegisterFlags::Field::log(Log *log) const {
  LLDB_LOG(log, " Name: \"{0}\" Start: {1} End: {2}", m_name.c_str(), m_start,
  m_end);
@@ -175,3 +183,41 @@ std::string RegisterFlags::AsTable(uint32_t max_width) const {
 
  return table;
 }
+
+void RegisterFlags::ToXML(StreamString &strm) const {
+ // Example XML:
+ // <flags id="cpsr_flags" size="4">
+ // <field name="incorrect" start="0" end="0"/>
+ // </flags>
+ strm.Indent();
+ strm << "<flags id=\"" << GetID() << "\" ";
+ strm.Printf("size=\"%d\"", GetSize());
+ strm << ">";
+ for (const Field &field : m_fields) {
+ // Skip padding fields.
+ if (field.GetName().empty())
+ continue;
+
+ strm << "\n";
+ strm.IndentMore();
+ field.ToXML(strm);
+ strm.IndentLess();
+ }
+ strm.PutChar('\n');
+ strm.Indent("</flags>\n");
+}
+
+void RegisterFlags::Field::ToXML(StreamString &strm) const {
+ // Example XML:
+ // <field name="correct" start="0" end="0"/>
+ strm.Indent();
+ strm << "<field name=\"";
+
+ std::string escaped_name;
+ llvm::raw_string_ostream escape_strm(escaped_name);
+ llvm::printHTMLEscaped(GetName(), escape_strm);
+ strm << escaped_name << "\" ";
+
+ strm.Printf("start=\"%d\" end=\"%d\"", GetStart(), GetEnd());
+ strm << "/>";
+}

lldb/unittests/Target/RegisterFlagsTest.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Target/RegisterFlags.h"
+#include "lldb/Utility/StreamString.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
@@ -258,3 +259,52 @@ TEST(RegisterFlagsTest, AsTable) {
  "| really long name |",
  max_many_columns.AsTable(23));
 }
+
+TEST(RegisterFieldsTest, ToXML) {
+ StreamString strm;
+
+ // RegisterFlags requires that some fields be given, so no testing of empty
+ // input.
+
+ // Unnamed fields are padding that are ignored. This applies to fields passed
+ // in, and those generated to fill the other bits (31-1 here).
+ RegisterFlags("Foo", 4, {RegisterFlags::Field("", 0, 0)}).ToXML(strm);
+ ASSERT_EQ(strm.GetString(), "<flags id=\"Foo\" size=\"4\">\n"
+ "</flags>\n");
+
+ strm.Clear();
+ RegisterFlags("Foo", 4, {RegisterFlags::Field("abc", 0, 0)}).ToXML(strm);
+ ASSERT_EQ(strm.GetString(), "<flags id=\"Foo\" size=\"4\">\n"
+ " <field name=\"abc\" start=\"0\" end=\"0\"/>\n"
+ "</flags>\n");
+
+ strm.Clear();
+ // Should use the current indentation level as a starting point.
+ strm.IndentMore();
+ RegisterFlags(
+ "Bar", 5,
+ {RegisterFlags::Field("f1", 25, 32), RegisterFlags::Field("f2", 10, 24)})
+ .ToXML(strm);
+ ASSERT_EQ(strm.GetString(),
+ " <flags id=\"Bar\" size=\"5\">\n"
+ " <field name=\"f1\" start=\"25\" end=\"32\"/>\n"
+ " <field name=\"f2\" start=\"10\" end=\"24\"/>\n"
+ " </flags>\n");
+
+ strm.Clear();
+ strm.IndentLess();
+ // Should replace any XML unsafe characters in field names.
+ RegisterFlags("Safe", 8,
+ {RegisterFlags::Field("A<", 4), RegisterFlags::Field("B>", 3),
+ RegisterFlags::Field("C'", 2), RegisterFlags::Field("D\"", 1),
+ RegisterFlags::Field("E&", 0)})
+ .ToXML(strm);
+ ASSERT_EQ(strm.GetString(),
+ "<flags id=\"Safe\" size=\"8\">\n"
+ " <field name=\"A&lt;\" start=\"4\" end=\"4\"/>\n"
+ " <field name=\"B&gt;\" start=\"3\" end=\"3\"/>\n"
+ " <field name=\"C&apos;\" start=\"2\" end=\"2\"/>\n"
+ " <field name=\"D&quot;\" start=\"1\" end=\"1\"/>\n"
+ " <field name=\"E&amp;\" start=\"0\" end=\"0\"/>\n"
+ "</flags>\n");
+}