[Lldb-commits] [lldb] [lldb][Mach-O] Allow "process metadata" LC_NOTE to supply registers (PR #144627)

Jason Molenda via lldb-commits lldb-commits at lists.llvm.org
Tue Jun 17 19:18:54 PDT 2025


https://github.com/jasonmolenda created https://github.com/llvm/llvm-project/pull/144627

The "process metadata" LC_NOTE allows for thread IDs to be specified in a Mach-O corefile.  This extends the JSON recognzied in that LC_NOTE to allow for additional registers to be supplied on a per-thread basis.

The registers included in a Mach-O corefile LC_THREAD load command can only be one of the register flavors that the kernel (xnu) defines in <mach/arm/thread_status.h> for arm64 -- the general purpose registers, floating point registers, exception registers.

JTAG style corefile producers may have access to many additional registers beyond these that EL0 programs typically use, for instance TCR_EL1 on AArch64, and people developing low level code need access to these registers.  This patch defines a format for including these registers for any thread.

The JSON in "process metadata" is a dictionary that must have a `threads` key.  The value is an array of entries, one per LC_THREAD in the Mach-O corefile.  The number of entries must match the LC_THREADs so they can be correctly associated.

Each thread's dictionary must have two keys, `sets`, and `registers`. `sets` is an array of register set names.  If a register set name matches one from the LC_THREAD core registers, any registers that are defined will be added to that register set.  e.g. metadata can add a register to the "General Purpose Registers" set that lldb shows users.

`registers` is an array of dictionaries, one per register.  Each register must have the keys `name`, `value`, `bitsize`, and `set`. It may provide additional keys like `alt-name`, that `DynamicRegisterInfo::SetRegisterInfo` recognizes.

This `sets` + `registers` formatting is the same that is used by the `target.process.python-os-plugin-path` script interface uses, both are parsed by `DynamicRegisterInfo`.  The one addition is that in this LC_NOTE metadata, each register must also have a `value` field, with the value provided in big-endian base 10, as usual with JSON.

In RegisterContextUnifiedCore, I combine the register sets & registers from the LC_THREAD for a specific thread, and the metadata sets & registers for that thread from the LC_NOTE.  Even if no LC_NOTE is present, this class ingests the LC_THREAD register contexts and reformats it to its internal stores before returning itself as the RegisterContex, instead of shortcutting and returning the core's native RegisterContext.  I could have gone either way with that, but in the end I decided if the code is correct, we should live on it always.

I added a test where we process save-core to create a userland corefile, then use a utility "add-lcnote" to strip the existing "process metadata" LC_NOTE that lldb put in it, and adds a new one from a JSON string.

rdar://74358787

>From 92348b28fb02901e9bbbb437b92c1ddf8cfed31c Mon Sep 17 00:00:00 2001
From: Jason Molenda <jmolenda at apple.com>
Date: Tue, 17 Jun 2025 18:57:11 -0700
Subject: [PATCH] [lldb][Mach-O] Allow "process metadata" LC_NOTE to supply
 registers

The "process metadata" LC_NOTE allows for thread IDs to be specified
in a Mach-O corefile.  This extends the JSON recognzied in that
LC_NOTE to allow for additional registers to be supplied on a
per-thread basis.

The registers included in a Mach-O corefile LC_THREAD load command
can only be one of the register flavors that the kernel (xnu) defines
in <mach/arm/thread_status.h> for arm64 -- the general purpose
registers, floating point registers, exception registers.

JTAG style corefile producers may have access to many additional
registers beyond these that EL0 programs typically use, for instance
TCR_EL1 on AArch64, and people developing low level code need access
to these registers.  This patch defines a format for including these
registers for any thread.

The JSON in "process metadata" is a dictionary that must have a
`threads` key.  The value is an array of entries, one per LC_THREAD
in the Mach-O corefile.  The number of entries must match the
LC_THREADs so they can be correctly associated.

Each thread's dictionary must have two keys, `sets`, and `registers`.
`sets` is an array of register set names.  If a register set name
matches one from the LC_THREAD core registers, any registers that
are defined will be added to that register set.  e.g. metadata can
add a register to the "General Purpose Registers" set that lldb
shows users.

`registers` is an array of dictionaries, one per register.  Each
register must have the keys `name`, `value`, `bitsize`, and `set`.
It may provide additional keys like `alt-name`, that
`DynamicRegisterInfo::SetRegisterInfo` recognizes.

This `sets` + `registers` formatting is the same that is used by
the `target.process.python-os-plugin-path` script interface uses,
both are parsed by `DynamicRegisterInfo`.  The one addition is that
in this LC_NOTE metadata, each register must also have a `value`
field, with the value provided in big-endian base 10, as usual with
JSON.

In RegisterContextUnifiedCore, I combine the register sets & registers
from the LC_THREAD for a specific thread, and the metadata sets &
registers for that thread from the LC_NOTE.  Even if no LC_NOTE
is present, this class ingests the LC_THREAD register contexts and
reformats it to its internal stores before returning itself as the
RegisterContex, instead of shortcutting and returning the core's
native RegisterContext.  I could have gone either way with that,
but in the end I decided if the code is correct, we should live on
it always.

I added a test where we process save-core to create a userland corefile,
then use a utility "add-lcnote" to strip the existing "process metadata"
LC_NOTE that lldb put in it, and adds a new one from a JSON string.

rdar://74358787
---
 lldb/include/lldb/Symbol/ObjectFile.h         |  17 +-
 .../ObjectFile/Mach-O/ObjectFileMachO.cpp     |  61 ++-
 .../ObjectFile/Mach-O/ObjectFileMachO.h       |   2 +
 .../Plugins/Process/mach-core/CMakeLists.txt  |   1 +
 .../mach-core/RegisterContextUnifiedCore.cpp  | 293 +++++++++++++
 .../mach-core/RegisterContextUnifiedCore.h    |  57 +++
 .../Process/mach-core/ThreadMachCore.cpp      |  55 ++-
 .../lc-note/additional-registers/Makefile     |  11 +
 .../TestMetadataRegisters.py                  | 100 +++++
 .../additional-registers/add-lcnote.cpp       | 384 ++++++++++++++++++
 .../lc-note/additional-registers/main.c       |  11 +
 11 files changed, 957 insertions(+), 35 deletions(-)
 create mode 100644 lldb/source/Plugins/Process/mach-core/RegisterContextUnifiedCore.cpp
 create mode 100644 lldb/source/Plugins/Process/mach-core/RegisterContextUnifiedCore.h
 create mode 100644 lldb/test/API/macosx/lc-note/additional-registers/Makefile
 create mode 100644 lldb/test/API/macosx/lc-note/additional-registers/TestMetadataRegisters.py
 create mode 100644 lldb/test/API/macosx/lc-note/additional-registers/add-lcnote.cpp
 create mode 100644 lldb/test/API/macosx/lc-note/additional-registers/main.c

diff --git a/lldb/include/lldb/Symbol/ObjectFile.h b/lldb/include/lldb/Symbol/ObjectFile.h
index 43567592dd447..1b9ae1fb31a69 100644
--- a/lldb/include/lldb/Symbol/ObjectFile.h
+++ b/lldb/include/lldb/Symbol/ObjectFile.h
@@ -18,6 +18,7 @@
 #include "lldb/Utility/Endian.h"
 #include "lldb/Utility/FileSpec.h"
 #include "lldb/Utility/FileSpecList.h"
+#include "lldb/Utility/StructuredData.h"
 #include "lldb/Utility/UUID.h"
 #include "lldb/lldb-private.h"
 #include "llvm/Support/Threading.h"
@@ -544,9 +545,9 @@ class ObjectFile : public std::enable_shared_from_this<ObjectFile>,
     return false;
   }
 
-  /// Get metadata about threads from the corefile.
+  /// Get metadata about thread ids from the corefile.
   ///
-  /// The corefile may have metadata (e.g. a Mach-O "thread extrainfo"
+  /// The corefile may have metadata (e.g. a Mach-O "process metadata"
   /// LC_NOTE) which for the threads in the process; this method tries
   /// to retrieve them.
   ///
@@ -568,6 +569,18 @@ class ObjectFile : public std::enable_shared_from_this<ObjectFile>,
     return false;
   }
 
+  /// Get process metadata from the corefile in a StructuredData dictionary.
+  ///
+  /// The corefile may have notes (e.g. a Mach-O "process metadata" LC_NOTE)
+  /// which provide metadata about the process and threads in a JSON or
+  /// similar format.
+  ///
+  /// \return
+  ///     A StructuredData object with the metadata in the note, if there is
+  ///     one.  An empty shared pointer is returned if not metadata is found,
+  ///     or a problem parsing it.
+  virtual StructuredData::ObjectSP GetCorefileProcessMetadata() { return {}; }
+
   virtual lldb::RegisterContextSP
   GetThreadContextAtIndex(uint32_t idx, lldb_private::Thread &thread) {
     return lldb::RegisterContextSP();
diff --git a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
index b1741926b74aa..aea45293095e7 100644
--- a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
+++ b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
@@ -5794,27 +5794,9 @@ bool ObjectFileMachO::GetCorefileThreadExtraInfos(
     std::lock_guard<std::recursive_mutex> guard(module_sp->GetMutex());
 
     Log *log(GetLog(LLDBLog::Object | LLDBLog::Process | LLDBLog::Thread));
-    auto lc_notes = FindLC_NOTEByName("process metadata");
-    for (auto lc_note : lc_notes) {
-      offset_t payload_offset = std::get<0>(lc_note);
-      offset_t strsize = std::get<1>(lc_note);
-      std::string buf(strsize, '\0');
-      if (m_data.CopyData(payload_offset, strsize, buf.data()) != strsize) {
-        LLDB_LOGF(log,
-                  "Unable to read %" PRIu64
-                  " bytes of 'process metadata' LC_NOTE JSON contents",
-                  strsize);
-        return false;
-      }
-      while (buf.back() == '\0')
-        buf.resize(buf.size() - 1);
-      StructuredData::ObjectSP object_sp = StructuredData::ParseJSON(buf);
+    StructuredData::ObjectSP object_sp = GetCorefileProcessMetadata();
+    if (object_sp) {
       StructuredData::Dictionary *dict = object_sp->GetAsDictionary();
-      if (!dict) {
-        LLDB_LOGF(log, "Unable to read 'process metadata' LC_NOTE, did not "
-                       "get a dictionary.");
-        return false;
-      }
       StructuredData::Array *threads;
       if (!dict->GetValueForKeyAsArray("threads", threads) || !threads) {
         LLDB_LOGF(log,
@@ -5857,6 +5839,45 @@ bool ObjectFileMachO::GetCorefileThreadExtraInfos(
   return false;
 }
 
+StructuredData::ObjectSP ObjectFileMachO::GetCorefileProcessMetadata() {
+  ModuleSP module_sp(GetModule());
+  if (!module_sp)
+    return {};
+
+  Log *log(GetLog(LLDBLog::Object | LLDBLog::Process | LLDBLog::Thread));
+  std::lock_guard<std::recursive_mutex> guard(module_sp->GetMutex());
+  auto lc_notes = FindLC_NOTEByName("process metadata");
+  if (lc_notes.size() == 0)
+    return {};
+
+  if (lc_notes.size() > 1)
+    LLDB_LOGF(
+        log,
+        "Multiple 'process metadata' LC_NOTEs found, only using the first.");
+
+  offset_t payload_offset = std::get<0>(lc_notes[0]);
+  offset_t strsize = std::get<1>(lc_notes[0]);
+  std::string buf(strsize, '\0');
+  if (m_data.CopyData(payload_offset, strsize, buf.data()) != strsize) {
+    LLDB_LOGF(log,
+              "Unable to read %" PRIu64
+              " bytes of 'process metadata' LC_NOTE JSON contents",
+              strsize);
+    return {};
+  }
+  while (buf.back() == '\0')
+    buf.resize(buf.size() - 1);
+  StructuredData::ObjectSP object_sp = StructuredData::ParseJSON(buf);
+  StructuredData::Dictionary *dict = object_sp->GetAsDictionary();
+  if (!dict) {
+    LLDB_LOGF(log, "Unable to read 'process metadata' LC_NOTE, did not "
+                   "get a dictionary.");
+    return {};
+  }
+
+  return object_sp;
+}
+
 lldb::RegisterContextSP
 ObjectFileMachO::GetThreadContextAtIndex(uint32_t idx,
                                          lldb_private::Thread &thread) {
diff --git a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.h b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.h
index 7f67f5e04f1d6..7e3a6754dd0b8 100644
--- a/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.h
+++ b/lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.h
@@ -133,6 +133,8 @@ class ObjectFileMachO : public lldb_private::ObjectFile {
 
   bool GetCorefileThreadExtraInfos(std::vector<lldb::tid_t> &tids) override;
 
+  lldb_private::StructuredData::ObjectSP GetCorefileProcessMetadata() override;
+
   bool LoadCoreFileImages(lldb_private::Process &process) override;
 
   lldb::RegisterContextSP
diff --git a/lldb/source/Plugins/Process/mach-core/CMakeLists.txt b/lldb/source/Plugins/Process/mach-core/CMakeLists.txt
index a1ea85ec4c728..926f06d23c64b 100644
--- a/lldb/source/Plugins/Process/mach-core/CMakeLists.txt
+++ b/lldb/source/Plugins/Process/mach-core/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_lldb_library(lldbPluginProcessMachCore PLUGIN
   ProcessMachCore.cpp
   ThreadMachCore.cpp
+  RegisterContextUnifiedCore.cpp
 
   LINK_COMPONENTS
     Support
diff --git a/lldb/source/Plugins/Process/mach-core/RegisterContextUnifiedCore.cpp b/lldb/source/Plugins/Process/mach-core/RegisterContextUnifiedCore.cpp
new file mode 100644
index 0000000000000..774c0ca605b3c
--- /dev/null
+++ b/lldb/source/Plugins/Process/mach-core/RegisterContextUnifiedCore.cpp
@@ -0,0 +1,293 @@
+//===-- RegisterContextUnifiedCore.cpp ------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "RegisterContextUnifiedCore.h"
+#include "lldb/Target/DynamicRegisterInfo.h"
+#include "lldb/Target/Process.h"
+#include "lldb/Utility/DataExtractor.h"
+#include "lldb/Utility/RegisterValue.h"
+#include "lldb/Utility/StructuredData.h"
+
+using namespace lldb;
+using namespace lldb_private;
+
+RegisterContextUnifiedCore::RegisterContextUnifiedCore(
+    Thread &thread, uint32_t concrete_frame_idx,
+    RegisterContextSP core_thread_regctx_sp,
+    StructuredData::ObjectSP metadata_thread_registers)
+    : RegisterContext(thread, concrete_frame_idx) {
+
+  ProcessSP process_sp(thread.GetProcess());
+  Target &target = process_sp->GetTarget();
+  StructuredData::Dictionary *metadata_registers_dict = nullptr;
+
+  // If we have thread metadata, check if the keys for register
+  // definitions are present; if not, clear the ObjectSP.
+  if (metadata_thread_registers &&
+      metadata_thread_registers->GetAsDictionary()->HasKey("register_info")) {
+    metadata_registers_dict = metadata_thread_registers->GetAsDictionary()
+                                  ->GetValueForKey("register_info")
+                                  ->GetAsDictionary();
+    if (metadata_registers_dict)
+      if (!metadata_registers_dict->HasKey("sets") ||
+          !metadata_registers_dict->HasKey("registers"))
+        metadata_registers_dict = nullptr;
+  }
+
+  // When creating a register set list from the two sources,
+  // the LC_THREAD aka core_thread_regctx_sp register sets
+  // will be used at the same indexes.
+  // Any additional sets named by the thread metadata registers
+  // will be added.  If the thread metadata registers specify
+  // a set with the same name, the already-used index from the
+  // core register context will be used.
+  std::map<size_t, size_t> metadata_regset_to_combined_regset;
+
+  // Calculate the total size of the register store buffer we need
+  // for all registers.  The corefile register definitions may include
+  // RegisterInfo descriptions of registers that aren't actually
+  // available.  For simplicity, calculate the size of all registers
+  // as if they are available, so we can maintain the same offsets into
+  // the buffer.
+  uint32_t core_buffer_end = 0;
+  for (size_t idx = 0; idx < core_thread_regctx_sp->GetRegisterCount(); idx++) {
+    const RegisterInfo *reginfo =
+        core_thread_regctx_sp->GetRegisterInfoAtIndex(idx);
+    core_buffer_end =
+        std::max(reginfo->byte_offset + reginfo->byte_size, core_buffer_end);
+  }
+
+  // Add metadata register sizes to the total buffer size.
+  uint32_t combined_buffer_end = core_buffer_end;
+  if (metadata_registers_dict) {
+    StructuredData::Array *registers = nullptr;
+    if (metadata_registers_dict->GetValueForKeyAsArray("registers", registers))
+      registers->ForEach(
+          [&combined_buffer_end](StructuredData::Object *ent) -> bool {
+            uint32_t bitsize;
+            if (!ent->GetAsDictionary()->GetValueForKeyAsInteger("bitsize",
+                                                                 bitsize))
+              return false;
+            combined_buffer_end += (bitsize / 8);
+            return true;
+          });
+  }
+  m_register_data.resize(combined_buffer_end, 0);
+
+  // Copy the core register values into our combined data buffer,
+  // skip registers that are contained within another (e.g. w0 vs. x0)
+  // and registers that return as "unavailable".
+  for (size_t idx = 0; idx < core_thread_regctx_sp->GetRegisterCount(); idx++) {
+    const RegisterInfo *reginfo =
+        core_thread_regctx_sp->GetRegisterInfoAtIndex(idx);
+    RegisterValue val;
+    if (!reginfo->value_regs &&
+        core_thread_regctx_sp->ReadRegister(reginfo, val))
+      memcpy(m_register_data.data() + reginfo->byte_offset, val.GetBytes(),
+             val.GetByteSize());
+  }
+
+  // Set 'offset' fields for each register definition into our combined
+  // register data buffer. DynamicRegisterInfo needs
+  // this field set to parse the JSON.
+  // Also copy the values of the registers into our register data buffer.
+  if (metadata_registers_dict) {
+    size_t offset = core_buffer_end;
+    ByteOrder byte_order = core_thread_regctx_sp->GetByteOrder();
+    StructuredData::Array *registers;
+    if (metadata_registers_dict->GetValueForKeyAsArray("registers", registers))
+      registers->ForEach([this, &offset,
+                          byte_order](StructuredData::Object *ent) -> bool {
+        uint64_t bitsize;
+        uint64_t value;
+        if (!ent->GetAsDictionary()->GetValueForKeyAsInteger("bitsize",
+                                                             bitsize))
+          return false;
+        if (!ent->GetAsDictionary()->GetValueForKeyAsInteger("value", value)) {
+          // we had a bitsize but no value, so move the offset forward I guess.
+          offset += (bitsize / 8);
+          return false;
+        }
+        ent->GetAsDictionary()->AddIntegerItem("offset", offset);
+        Status error;
+        switch (bitsize / 8) {
+        case 2: {
+          Scalar value_scalar((uint16_t)value);
+          value_scalar.GetAsMemoryData(m_register_data.data() + offset, 2,
+                                       byte_order, error);
+          offset += 2;
+        } break;
+        case 4: {
+          Scalar value_scalar((uint32_t)value);
+          value_scalar.GetAsMemoryData(m_register_data.data() + offset, 4,
+                                       byte_order, error);
+          offset += 4;
+        } break;
+        case 8: {
+          Scalar value_scalar((uint64_t)value);
+          value_scalar.GetAsMemoryData(m_register_data.data() + offset, 8,
+                                       byte_order, error);
+          offset += 8;
+        } break;
+        }
+        return true;
+      });
+  }
+
+  // Create a DynamicRegisterInfo from the metadata JSON.
+  std::unique_ptr<DynamicRegisterInfo> additional_reginfo_up;
+  if (metadata_registers_dict)
+    additional_reginfo_up = DynamicRegisterInfo::Create(
+        *metadata_registers_dict, target.GetArchitecture());
+
+  // Copy the core thread register sets into our combined register set list.
+  for (size_t idx = 0; idx < core_thread_regctx_sp->GetRegisterSetCount();
+       idx++) {
+    RegisterSet new_set;
+    const RegisterSet *old_set = core_thread_regctx_sp->GetRegisterSet(idx);
+    new_set.name = ConstString(old_set->name).AsCString();
+    if (old_set->short_name)
+      new_set.short_name = ConstString(old_set->short_name).AsCString();
+    else
+      new_set.short_name = nullptr;
+    m_register_sets.push_back(new_set);
+  }
+
+  // Set up our RegisterSet array.
+  // First copying all of the core thread register sets,
+  // then any additional unique register sets from the metadata.
+  if (additional_reginfo_up) {
+    for (size_t idx = 0; idx < additional_reginfo_up->GetNumRegisterSets();
+         idx++) {
+      bool found_match = false;
+      const RegisterSet *old_set = additional_reginfo_up->GetRegisterSet(idx);
+      for (size_t jdx = 0; jdx < m_register_sets.size(); jdx++) {
+        if (strcmp(m_register_sets[jdx].name, old_set->name) == 0) {
+          metadata_regset_to_combined_regset[idx] = jdx;
+          found_match = true;
+          break;
+        }
+      }
+      if (!found_match) {
+        RegisterSet new_set;
+        new_set.name = ConstString(old_set->name).AsCString();
+        if (old_set->short_name)
+          new_set.short_name = ConstString(old_set->short_name).AsCString();
+        else
+          new_set.short_name = nullptr;
+        metadata_regset_to_combined_regset[idx] = m_register_sets.size();
+        m_register_sets.push_back(new_set);
+      }
+    }
+  }
+
+  // Set up our RegisterInfo array, one RegisterSet at a time.
+  // The metadata registers may be declared to be in a core thread
+  // register set (e.g. "General Purpose Registers", so we scan
+  // both core registers and metadata registers should be examined
+  // when creating the combined register sets.
+  for (size_t combined_regset_idx = 0;
+       combined_regset_idx < m_register_sets.size(); combined_regset_idx++) {
+    uint32_t registers_this_regset = 0;
+    if (combined_regset_idx < core_thread_regctx_sp->GetRegisterSetCount()) {
+      const RegisterSet *regset =
+          core_thread_regctx_sp->GetRegisterSet(combined_regset_idx);
+      for (size_t j = 0; j < regset->num_registers; j++) {
+        uint32_t reg_idx = regset->registers[j];
+        const RegisterInfo *reginfo =
+            core_thread_regctx_sp->GetRegisterInfoAtIndex(reg_idx);
+        RegisterValue val;
+        if (!reginfo->value_regs &&
+            core_thread_regctx_sp->ReadRegister(reginfo, val)) {
+          m_regset_regnum_collection[combined_regset_idx].push_back(
+              m_register_infos.size());
+          m_register_infos.push_back(*reginfo);
+          registers_this_regset++;
+        }
+      }
+    }
+    if (additional_reginfo_up) {
+      // Find the register set in the metadata that matches this register
+      // set, then copy all its RegisterInfos.
+      for (size_t setidx = 0;
+           setidx < additional_reginfo_up->GetNumRegisterSets(); setidx++) {
+        if (metadata_regset_to_combined_regset[setidx] == combined_regset_idx) {
+          const RegisterSet *regset =
+              additional_reginfo_up->GetRegisterSet(setidx);
+          for (size_t j = 0; j < regset->num_registers; j++) {
+            uint32_t reg_idx = regset->registers[j];
+            const RegisterInfo *reginfo =
+                additional_reginfo_up->GetRegisterInfoAtIndex(reg_idx);
+            m_regset_regnum_collection[combined_regset_idx].push_back(
+                m_register_infos.size());
+            // register names in DynamicRegisterInfo are ConstString stored;
+            // we can reuse the char* pointers here without retaining the
+            // DynamicRegisterInfo.
+            m_register_infos.push_back(*reginfo);
+            registers_this_regset++;
+          }
+        }
+      }
+    }
+    m_register_sets[combined_regset_idx].num_registers = registers_this_regset;
+    m_register_sets[combined_regset_idx].registers =
+        m_regset_regnum_collection[combined_regset_idx].data();
+  }
+}
+
+size_t RegisterContextUnifiedCore::GetRegisterCount() {
+  return m_register_infos.size();
+}
+
+const RegisterInfo *
+RegisterContextUnifiedCore::GetRegisterInfoAtIndex(size_t reg) {
+  return &m_register_infos[reg];
+}
+
+size_t RegisterContextUnifiedCore::GetRegisterSetCount() {
+  return m_register_sets.size();
+}
+
+const RegisterSet *RegisterContextUnifiedCore::GetRegisterSet(size_t set) {
+  return &m_register_sets[set];
+}
+
+bool RegisterContextUnifiedCore::ReadRegister(
+    const lldb_private::RegisterInfo *reg_info,
+    lldb_private::RegisterValue &value) {
+  if (!reg_info)
+    return false;
+  ProcessSP process_sp(m_thread.GetProcess());
+  if (process_sp) {
+    DataExtractor regdata(m_register_data.data(), m_register_data.size(),
+                          process_sp->GetByteOrder(),
+                          process_sp->GetAddressByteSize());
+    offset_t offset = reg_info->byte_offset;
+    switch (reg_info->byte_size) {
+    case 2:
+      value.SetUInt16(regdata.GetU16(&offset));
+      break;
+    case 4:
+      value.SetUInt32(regdata.GetU32(&offset));
+      break;
+    case 8:
+      value.SetUInt64(regdata.GetU64(&offset));
+      break;
+    default:
+      return false;
+    }
+    return true;
+  }
+  return false;
+}
+
+bool RegisterContextUnifiedCore::WriteRegister(
+    const lldb_private::RegisterInfo *reg_info,
+    const lldb_private::RegisterValue &value) {
+  return false;
+}
diff --git a/lldb/source/Plugins/Process/mach-core/RegisterContextUnifiedCore.h b/lldb/source/Plugins/Process/mach-core/RegisterContextUnifiedCore.h
new file mode 100644
index 0000000000000..47e2fb7cac5a3
--- /dev/null
+++ b/lldb/source/Plugins/Process/mach-core/RegisterContextUnifiedCore.h
@@ -0,0 +1,57 @@
+//===-- RegisterContextUnifiedCore.h ----------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_SOURCE_PLUGINS_PROCESS_REGISTERCONTEXT_UNIFIED_CORE_H
+#define LLDB_SOURCE_PLUGINS_PROCESS_REGISTERCONTEXT_UNIFIED_CORE_H
+
+#include <string>
+#include <vector>
+
+#include "lldb/Target/RegisterContext.h"
+#include "lldb/Utility/ConstString.h"
+#include "lldb/Utility/StructuredData.h"
+#include "lldb/lldb-enumerations.h"
+#include "lldb/lldb-private.h"
+
+namespace lldb_private {
+
+class RegisterContextUnifiedCore : public RegisterContext {
+public:
+  RegisterContextUnifiedCore(
+      Thread &thread, uint32_t concrete_frame_idx,
+      lldb::RegisterContextSP core_thread_regctx_sp,
+      lldb_private::StructuredData::ObjectSP metadata_thread_registers);
+
+  void InvalidateAllRegisters() override{};
+
+  size_t GetRegisterCount() override;
+
+  const lldb_private::RegisterInfo *GetRegisterInfoAtIndex(size_t reg) override;
+
+  size_t GetRegisterSetCount() override;
+
+  const lldb_private::RegisterSet *GetRegisterSet(size_t set) override;
+
+  bool ReadRegister(const lldb_private::RegisterInfo *reg_info,
+                    lldb_private::RegisterValue &value) override;
+
+  bool WriteRegister(const lldb_private::RegisterInfo *reg_info,
+                     const lldb_private::RegisterValue &value) override;
+
+private:
+  std::vector<lldb_private::RegisterSet> m_register_sets;
+  std::vector<lldb_private::RegisterInfo> m_register_infos;
+  // For each register set, an array of register numbers included.
+  std::map<size_t, std::vector<uint32_t>> m_regset_regnum_collection;
+  // Bytes of the register contents.
+  std::vector<uint8_t> m_register_data;
+};
+
+} // namespace lldb_private
+
+#endif // LLDB_SOURCE_PLUGINS_PROCESS_REGISTERCONTEXT_UNIFIED_CORE_H
diff --git a/lldb/source/Plugins/Process/mach-core/ThreadMachCore.cpp b/lldb/source/Plugins/Process/mach-core/ThreadMachCore.cpp
index 003cdd0fcaa57..0bb9f4da9bc92 100644
--- a/lldb/source/Plugins/Process/mach-core/ThreadMachCore.cpp
+++ b/lldb/source/Plugins/Process/mach-core/ThreadMachCore.cpp
@@ -6,12 +6,18 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include <optional>
+#include <string>
+#include <vector>
+
+#include "RegisterContextUnifiedCore.h"
 #include "ThreadMachCore.h"
 
 #include "lldb/Breakpoint/Watchpoint.h"
 #include "lldb/Host/SafeMachO.h"
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Target/AppleArm64ExceptionClass.h"
+#include "lldb/Target/DynamicRegisterInfo.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Target/RegisterContext.h"
 #include "lldb/Target/StopInfo.h"
@@ -22,6 +28,7 @@
 #include "lldb/Utility/RegisterValue.h"
 #include "lldb/Utility/State.h"
 #include "lldb/Utility/StreamString.h"
+#include "lldb/Utility/StructuredData.h"
 
 #include "ProcessMachCore.h"
 //#include "RegisterContextKDP_arm.h"
@@ -70,27 +77,49 @@ lldb::RegisterContextSP ThreadMachCore::GetRegisterContext() {
 
 lldb::RegisterContextSP
 ThreadMachCore::CreateRegisterContextForFrame(StackFrame *frame) {
-  lldb::RegisterContextSP reg_ctx_sp;
   uint32_t concrete_frame_idx = 0;
 
   if (frame)
     concrete_frame_idx = frame->GetConcreteFrameIndex();
+  if (concrete_frame_idx > 0)
+    return GetUnwinder().CreateRegisterContextForFrame(frame);
+
+  if (m_thread_reg_ctx_sp)
+    return m_thread_reg_ctx_sp;
 
-  if (concrete_frame_idx == 0) {
-    if (!m_thread_reg_ctx_sp) {
-      ProcessSP process_sp(GetProcess());
+  ProcessSP process_sp(GetProcess());
 
-      ObjectFile *core_objfile =
-          static_cast<ProcessMachCore *>(process_sp.get())->GetCoreObjectFile();
-      if (core_objfile)
-        m_thread_reg_ctx_sp = core_objfile->GetThreadContextAtIndex(
-            m_objfile_lc_thread_idx, *this);
+  ObjectFile *core_objfile =
+      static_cast<ProcessMachCore *>(process_sp.get())->GetCoreObjectFile();
+  if (!core_objfile)
+    return {};
+
+  RegisterContextSP core_thread_regctx_sp =
+      core_objfile->GetThreadContextAtIndex(m_objfile_lc_thread_idx, *this);
+
+  if (!core_thread_regctx_sp)
+    return {};
+
+  StructuredData::ObjectSP process_md_sp =
+      core_objfile->GetCorefileProcessMetadata();
+
+  StructuredData::ObjectSP thread_md_sp;
+  if (process_md_sp && process_md_sp->GetAsDictionary() &&
+      process_md_sp->GetAsDictionary()->HasKey("threads")) {
+    StructuredData::Array *threads = process_md_sp->GetAsDictionary()
+                                         ->GetValueForKey("threads")
+                                         ->GetAsArray();
+    if (threads) {
+      StructuredData::ObjectSP thread_sp =
+          threads->GetItemAtIndex(m_objfile_lc_thread_idx);
+      if (thread_sp && thread_sp->GetAsDictionary())
+        thread_md_sp = thread_sp;
     }
-    reg_ctx_sp = m_thread_reg_ctx_sp;
-  } else {
-    reg_ctx_sp = GetUnwinder().CreateRegisterContextForFrame(frame);
   }
-  return reg_ctx_sp;
+  m_thread_reg_ctx_sp = std::make_shared<RegisterContextUnifiedCore>(
+      *this, concrete_frame_idx, core_thread_regctx_sp, thread_md_sp);
+
+  return m_thread_reg_ctx_sp;
 }
 
 static bool IsCrashExceptionClass(AppleArm64ExceptionClass EC) {
diff --git a/lldb/test/API/macosx/lc-note/additional-registers/Makefile b/lldb/test/API/macosx/lc-note/additional-registers/Makefile
new file mode 100644
index 0000000000000..e232ec5d69675
--- /dev/null
+++ b/lldb/test/API/macosx/lc-note/additional-registers/Makefile
@@ -0,0 +1,11 @@
+MAKE_DSYM := NO
+C_SOURCES := main.c
+CXXFLAGS_EXTRAS := -std=c++17
+
+all: a.out add-lcnote
+
+add-lcnote:
+	"$(MAKE)" -f "$(MAKEFILE_RULES)" EXE=add-lcnote \
+	    CXX=$(CC) CXXFLAGS_EXTRAS="$(CXXFLAGS_EXTRAS)" CXX_SOURCES=add-lcnote.cpp
+
+include Makefile.rules
diff --git a/lldb/test/API/macosx/lc-note/additional-registers/TestMetadataRegisters.py b/lldb/test/API/macosx/lc-note/additional-registers/TestMetadataRegisters.py
new file mode 100644
index 0000000000000..104f79b62865c
--- /dev/null
+++ b/lldb/test/API/macosx/lc-note/additional-registers/TestMetadataRegisters.py
@@ -0,0 +1,100 @@
+"""Test that lldb will read additional registers from Mach-O LC_NOTE metadata."""
+
+import os
+import re
+import subprocess
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestMetadataRegisters(TestBase):
+    NO_DEBUG_INFO_TESTCASE = True
+
+    @skipUnlessDarwin
+    @skipIfRemote
+    def test_add_registers_via_metadata(self):
+        self.build()
+        self.aout_exe = self.getBuildArtifact("a.out")
+        lldb_corefile = self.getBuildArtifact("lldb.core")
+        metadata_corefile = self.getBuildArtifact("metadata.core")
+        add_lcnote = self.getBuildArtifact("add-lcnote")
+
+        (target, process, t, bp) = lldbutil.run_to_source_breakpoint(
+            self, "break here", lldb.SBFileSpec("main.c")
+        )
+
+        self.assertTrue(process.IsValid())
+
+        if self.TraceOn():
+            self.runCmd("bt")
+            self.runCmd("reg read -a")
+
+        self.runCmd("process save-core " + lldb_corefile)
+        process.Kill()
+        target.Clear()
+
+        cmd = (
+            add_lcnote
+            + " "
+            + "-r"
+            + " "
+            + "-i '%s'" % lldb_corefile
+            + " "
+            + "-o '%s'" % metadata_corefile
+            + " "
+            + "-n 'process metadata' "
+            + "-s '"
+            + """{"threads":[{"register_info":
+                   {"sets":["Special Registers", "General Purpose Registers"],
+                    "registers":[
+                       {"name":"jar", "value":10, "bitsize": 32, "set": 0},
+                       {"name":"bar", "value":65537, "bitsize":16, "set":0},
+                       {"name":"mar", "value":65537, "bitsize":32, "set":0},
+                       {"name":"anotherpc", "value":55, "bitsize":64, "set": 1}]}}]}"""
+            + "'"
+        )
+
+        print(cmd)
+        call(cmd, shell=True)
+
+        # Now load the corefile
+        target = self.dbg.CreateTarget("")
+        process = target.LoadCore(metadata_corefile)
+        self.assertTrue(process.IsValid())
+        if self.TraceOn():
+            self.runCmd("bt")
+            self.runCmd("reg read -a")
+
+        thread = process.GetSelectedThread()
+        frame = thread.GetFrameAtIndex(0)
+
+        # Register sets will be
+        #    from LC_THREAD:
+        #       General Purpose Registers
+        #       Floating Point Registers
+        #       Exception State Registers
+        #    from LC_NOTE metadata:
+        #       Special Registers
+        self.assertEqual(frame.registers[0].GetName(), "General Purpose Registers")
+        self.assertEqual(frame.registers[3].GetName(), "Special Registers")
+
+        anotherpc = frame.registers[0].GetChildMemberWithName("anotherpc")
+        self.assertTrue(anotherpc.IsValid())
+        self.assertEqual(anotherpc.GetValueAsUnsigned(), 0x37)
+
+        jar = frame.registers[3].GetChildMemberWithName("jar")
+        self.assertTrue(jar.IsValid())
+        self.assertEqual(jar.GetValueAsUnsigned(), 10)
+        self.assertEqual(jar.GetByteSize(), 4)
+
+        bar = frame.registers[3].GetChildMemberWithName("bar")
+        self.assertTrue(bar.IsValid())
+        self.assertEqual(bar.GetByteSize(), 2)
+
+        mar = frame.registers[3].GetChildMemberWithName("mar")
+        self.assertTrue(mar.IsValid())
+        self.assertEqual(mar.GetValueAsUnsigned(), 0x10001)
+        self.assertEqual(mar.GetByteSize(), 4)
diff --git a/lldb/test/API/macosx/lc-note/additional-registers/add-lcnote.cpp b/lldb/test/API/macosx/lc-note/additional-registers/add-lcnote.cpp
new file mode 100644
index 0000000000000..8d9d550a9ad72
--- /dev/null
+++ b/lldb/test/API/macosx/lc-note/additional-registers/add-lcnote.cpp
@@ -0,0 +1,384 @@
+#include <getopt.h>
+#include <mach-o/loader.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#include <iostream>
+#include <optional>
+#include <string>
+
+using namespace std;
+
+[[noreturn]] void print_help(void) {
+  fprintf(stderr, "Append an LC_NOTE to a corefile.  Usage: \n");
+  fprintf(stderr, "   -i|--input <corefile>\n");
+  fprintf(stderr, "   -o|--output <corefile>\n");
+  fprintf(stderr, "   -n|--name <LC_NOTE name>\n");
+  fprintf(
+      stderr,
+      "   -r|--remove-dups  remove existing LC_NOTEs with this same name\n");
+  fprintf(stderr, "  One of:\n");
+  fprintf(stderr, "   -f|--file <file to embed as LC_NOTE payload>\n");
+  fprintf(stderr, "   -s|--str <string to embed as LC_NOTE payload>\n");
+  exit(1);
+}
+
+void parse_args(int argc, char **argv, string &infile, string &outfile,
+                string &note_name, vector<uint8_t> &payload,
+                bool &remove_dups) {
+  const char *const short_opts = "i:o:n:f:s:hr";
+  const option long_opts[] = {{"input", required_argument, nullptr, 'i'},
+                              {"output", required_argument, nullptr, 'o'},
+                              {"name", required_argument, nullptr, 'n'},
+                              {"file", required_argument, nullptr, 'f'},
+                              {"str", required_argument, nullptr, 's'},
+                              {"remove-dups", no_argument, nullptr, 'r'},
+                              {"help", no_argument, nullptr, 'h'},
+                              {nullptr, no_argument, nullptr, 0}};
+  optional<string> infile_str, outfile_str, name_str, payload_file_str,
+      payload_str;
+  remove_dups = false;
+  while (true) {
+    const auto opt = getopt_long(argc, argv, short_opts, long_opts, nullptr);
+    if (opt == -1)
+      break;
+    switch (opt) {
+    case 'i':
+      infile_str = optarg;
+      break;
+    case 'o':
+      outfile_str = optarg;
+      break;
+    case 'n':
+      name_str = optarg;
+      break;
+    case 'f':
+      payload_file_str = optarg;
+      break;
+    case 's':
+      payload_str = optarg;
+      break;
+    case 'r':
+      remove_dups = true;
+      break;
+    case 'h':
+      print_help();
+    }
+  }
+
+  if (!infile_str || !outfile_str || !name_str ||
+      (!payload_file_str && !payload_str))
+    print_help();
+
+  infile = *infile_str;
+  outfile = *outfile_str;
+  note_name = *name_str;
+  if (payload_str) {
+    payload.resize(payload_str->size(), 0);
+    memcpy(payload.data(), payload_str->c_str(), payload_str->size());
+  } else {
+    struct stat sb;
+    if (stat(payload_file_str->c_str(), &sb)) {
+      fprintf(stderr, "File '%s' does not exist.\n", payload_file_str->c_str());
+      exit(1);
+    }
+    payload.resize(sb.st_size, 0);
+    FILE *f = fopen(payload_file_str->c_str(), "r");
+    fread(payload.data(), 1, sb.st_size, f);
+    fclose(f);
+  }
+}
+
+struct all_image_infos_header {
+  uint32_t version;         // currently 1
+  uint32_t imgcount;        // number of binary images
+  uint64_t entries_fileoff; // file offset in the corefile of where the array of
+                            // struct entry's begin.
+  uint32_t entry_size;      // size of 'struct entry'.
+  uint32_t unused;          // set to 0
+};
+
+struct image_entry {
+  uint64_t filepath_offset; // corefile offset of the c-string filepath,
+                            // if available, else this should be set
+                            // to UINT64_MAX.
+  uuid_t uuid;              // uint8_t[16].  should be set to all zeroes if
+                            // uuid is unknown.
+  uint64_t
+      load_address; // virtual addr of mach-o header, UINT64_MAX if unknown.
+  uint64_t seg_addrs_offset; // corefile offset to the array of struct
+                             // segment_vmaddr's, UINT64_MAX if none.
+  uint32_t segment_count; // The number of segments for this binary, 0 if none.
+  uint32_t
+      executing; // Set to 0 if executing status is unknown by corefile
+                 // creator.
+                 // Set to 1 if this binary was executing on any thread,
+                 // so it can be force-loaded by the corefile reader.
+                 // Set to 2 if this binary was not executing on any thread.
+};
+
+int count_lc_notes_with_name(FILE *in, std::string name) {
+  fseeko(in, 0, SEEK_SET);
+
+  uint8_t magic[4];
+  if (fread(magic, 1, 4, in) != 4) {
+    printf("Failed to read magic number\n");
+    return 0;
+  }
+  uint8_t magic_32_le[] = {0xce, 0xfa, 0xed, 0xfe};
+  uint8_t magic_64_le[] = {0xcf, 0xfa, 0xed, 0xfe};
+
+  if (memcmp(magic, magic_32_le, 4) != 0 &&
+      memcmp(magic, magic_64_le, 4) != 0) {
+    return 0;
+  }
+
+  fseeko(in, 0, SEEK_SET);
+
+  int number_of_load_cmds = 0;
+  size_t size_of_mach_header = 0;
+  if (memcmp(magic, magic_64_le, 4) == 0) {
+    struct mach_header_64 mh;
+    size_of_mach_header = sizeof(mh);
+    if (fread(&mh, sizeof(mh), 1, in) != 1) {
+      fprintf(stderr, "unable to read mach header\n");
+      return 0;
+    }
+    number_of_load_cmds = mh.ncmds;
+  } else {
+    struct mach_header mh;
+    size_of_mach_header = sizeof(mh);
+    if (fread(&mh, sizeof(mh), 1, in) != 1) {
+      fprintf(stderr, "unable to read mach header\n");
+      return 0;
+    }
+    number_of_load_cmds = mh.ncmds;
+  }
+
+  int notes_seen = 0;
+  fseeko(in, size_of_mach_header, SEEK_SET);
+  for (int i = 0; i < number_of_load_cmds; i++) {
+    off_t cmd_start = ftello(in);
+    uint32_t cmd, cmdsize;
+    fread(&cmd, sizeof(uint32_t), 1, in);
+    fread(&cmdsize, sizeof(uint32_t), 1, in);
+
+    fseeko(in, cmd_start, SEEK_SET);
+    off_t next_cmd = cmd_start + cmdsize;
+    if (cmd == LC_NOTE) {
+      struct note_command note;
+      fread(&note, sizeof(note), 1, in);
+      if (strncmp(name.c_str(), note.data_owner, 16) == 0)
+        notes_seen++;
+    }
+    fseeko(in, next_cmd, SEEK_SET);
+  }
+  return notes_seen;
+}
+
+void copy_and_add_note(FILE *in, FILE *out, std::string lc_note_name,
+                       vector<uint8_t> payload_data, bool remove_dups) {
+  int number_of_load_cmds = 0;
+  off_t header_start = ftello(in);
+
+  int notes_to_remove = 0;
+  if (remove_dups)
+    notes_to_remove = count_lc_notes_with_name(in, lc_note_name);
+  fseeko(in, header_start, SEEK_SET);
+
+  uint8_t magic[4];
+  if (fread(magic, 1, 4, in) != 4) {
+    printf("Failed to read magic number\n");
+    return;
+  }
+  uint8_t magic_32_le[] = {0xce, 0xfa, 0xed, 0xfe};
+  uint8_t magic_64_le[] = {0xcf, 0xfa, 0xed, 0xfe};
+
+  if (memcmp(magic, magic_32_le, 4) != 0 &&
+      memcmp(magic, magic_64_le, 4) != 0) {
+    return;
+  }
+
+  fseeko(in, header_start, SEEK_SET);
+
+  off_t end_of_infine_loadcmds;
+  size_t size_of_mach_header = 0;
+  if (memcmp(magic, magic_64_le, 4) == 0) {
+    struct mach_header_64 mh;
+    size_of_mach_header = sizeof(mh);
+    if (fread(&mh, sizeof(mh), 1, in) != 1) {
+      fprintf(stderr, "unable to read mach header\n");
+      return;
+    }
+    number_of_load_cmds = mh.ncmds;
+    end_of_infine_loadcmds = sizeof(mh) + mh.sizeofcmds;
+
+    mh.ncmds += 1;
+    mh.ncmds -= notes_to_remove;
+    mh.sizeofcmds += sizeof(struct note_command);
+    mh.sizeofcmds -= notes_to_remove * sizeof(struct note_command);
+    fseeko(out, header_start, SEEK_SET);
+    fwrite(&mh, sizeof(mh), 1, out);
+  } else {
+    struct mach_header mh;
+    size_of_mach_header = sizeof(mh);
+    if (fread(&mh, sizeof(mh), 1, in) != 1) {
+      fprintf(stderr, "unable to read mach header\n");
+      return;
+    }
+    number_of_load_cmds = mh.ncmds;
+    end_of_infine_loadcmds = sizeof(mh) + mh.sizeofcmds;
+
+    mh.ncmds += 1;
+    mh.ncmds -= notes_to_remove;
+    mh.sizeofcmds += sizeof(struct note_command);
+    mh.sizeofcmds -= notes_to_remove * sizeof(struct note_command);
+    fseeko(out, header_start, SEEK_SET);
+    fwrite(&mh, sizeof(mh), 1, out);
+  }
+
+  off_t start_of_infile_load_cmds = ftello(in);
+  fseek(in, 0, SEEK_END);
+  off_t infile_size = ftello(in);
+
+  // LC_SEGMENT may be aligned to 4k boundaries, let's maintain
+  // that alignment by putting 4096 minus the size of the added
+  // LC_NOTE load command after the output file's load commands.
+  off_t end_of_outfile_loadcmds =
+      end_of_infine_loadcmds - (notes_to_remove * sizeof(struct note_command)) +
+      4096 - sizeof(struct note_command);
+  off_t slide = end_of_outfile_loadcmds - end_of_infine_loadcmds;
+
+  off_t all_image_infos_infile_offset = 0;
+
+  fseek(in, start_of_infile_load_cmds, SEEK_SET);
+  fseek(out, start_of_infile_load_cmds, SEEK_SET);
+  // Copy all the load commands from IN to OUT, updating any file offsets by
+  // SLIDE.
+  for (int cmd_num = 0; cmd_num < number_of_load_cmds; cmd_num++) {
+    off_t cmd_start = ftello(in);
+    uint32_t cmd, cmdsize;
+    fread(&cmd, sizeof(uint32_t), 1, in);
+    fread(&cmdsize, sizeof(uint32_t), 1, in);
+
+    fseeko(in, cmd_start, SEEK_SET);
+    off_t next_cmd = cmd_start + cmdsize;
+
+    switch (cmd) {
+    case LC_SEGMENT: {
+      struct segment_command segcmd;
+      fread(&segcmd, sizeof(segcmd), 1, in);
+      segcmd.fileoff += slide;
+      fwrite(&segcmd, cmdsize, 1, out);
+    } break;
+    case LC_SEGMENT_64: {
+      struct segment_command_64 segcmd;
+      fread(&segcmd, sizeof(segcmd), 1, in);
+      segcmd.fileoff += slide;
+      fwrite(&segcmd, cmdsize, 1, out);
+    } break;
+    case LC_NOTE: {
+      struct note_command notecmd;
+      fread(&notecmd, sizeof(notecmd), 1, in);
+      if ((strncmp(lc_note_name.c_str(), notecmd.data_owner, 16) == 0) &&
+          remove_dups) {
+        fseeko(in, next_cmd, SEEK_SET);
+        continue;
+      }
+      if (strncmp("all image infos", notecmd.data_owner, 16) == 0)
+        all_image_infos_infile_offset = notecmd.offset;
+      notecmd.offset += slide;
+      fwrite(&notecmd, cmdsize, 1, out);
+    } break;
+    default: {
+      vector<uint8_t> buf(cmdsize);
+      fread(buf.data(), cmdsize, 1, in);
+      fwrite(buf.data(), cmdsize, 1, out);
+    }
+    }
+    fseeko(in, next_cmd, SEEK_SET);
+  }
+
+  // Now add our additional LC_NOTE load command.
+  struct note_command note;
+  note.cmd = LC_NOTE;
+  note.cmdsize = sizeof(struct note_command);
+  memset(&note.data_owner, 0, 16);
+  // data_owner may not be nul terminated if all 16 characters
+  // are used, intentionally using strncpy here.
+  strncpy(note.data_owner, lc_note_name.c_str(), 16);
+  note.offset = infile_size + slide;
+  note.size = payload_data.size();
+  fwrite(&note, sizeof(struct note_command), 1, out);
+
+  fseeko(in, end_of_infine_loadcmds, SEEK_SET);
+  fseeko(out, end_of_outfile_loadcmds, SEEK_SET);
+
+  // Copy the rest of the corefile contents
+  vector<uint8_t> data_buf(1024 * 1024);
+  while (!feof(in)) {
+    size_t read_bytes = fread(data_buf.data(), 1, data_buf.size(), in);
+    if (read_bytes > 0) {
+      fwrite(data_buf.data(), read_bytes, 1, out);
+    } else {
+      break;
+    }
+  }
+
+  fwrite(payload_data.data(), payload_data.size(), 1, out);
+
+  // The "all image infos" LC_NOTE payload has file offsets hardcoded
+  // in it, unfortunately.  We've shifted the contents of the corefile
+  // and these offsets need to be updated in the ouput file.
+  // Re-copy them into the outfile with corrected file offsets.
+  off_t infile_image_entry_base = 0;
+  if (all_image_infos_infile_offset != 0) {
+    off_t all_image_infos_outfile_offset =
+        all_image_infos_infile_offset + slide;
+    fseeko(in, all_image_infos_infile_offset, SEEK_SET);
+    struct all_image_infos_header header;
+    fread(&header, sizeof(header), 1, in);
+    infile_image_entry_base = header.entries_fileoff;
+    header.entries_fileoff += slide;
+    fseeko(out, all_image_infos_outfile_offset, SEEK_SET);
+    fwrite(&header, sizeof(header), 1, out);
+
+    for (int i = 0; i < header.imgcount; i++) {
+      off_t infile_entries_fileoff = header.entries_fileoff - slide;
+      off_t outfile_entries_fileoff = header.entries_fileoff;
+
+      struct image_entry ent;
+      fseeko(in, infile_entries_fileoff + (header.entry_size * i), SEEK_SET);
+      fread(&ent, sizeof(ent), 1, in);
+      ent.filepath_offset += slide;
+      ent.seg_addrs_offset += slide;
+      fseeko(out, outfile_entries_fileoff + (header.entry_size * i), SEEK_SET);
+      fwrite(&ent, sizeof(ent), 1, out);
+    }
+  }
+}
+
+int main(int argc, char **argv) {
+  string infile, outfile, name;
+  vector<uint8_t> payload;
+  bool remove_dups;
+  parse_args(argc, argv, infile, outfile, name, payload, remove_dups);
+
+  FILE *in = fopen(infile.c_str(), "r");
+  if (!in) {
+    fprintf(stderr, "Unable to open %s for reading\n", infile.c_str());
+    exit(1);
+  }
+  FILE *out = fopen(outfile.c_str(), "w");
+  if (!out) {
+    fprintf(stderr, "Unable to open %s for reading\n", outfile.c_str());
+    exit(1);
+  }
+
+  copy_and_add_note(in, out, name, payload, remove_dups);
+
+  fclose(in);
+  fclose(out);
+}
diff --git a/lldb/test/API/macosx/lc-note/additional-registers/main.c b/lldb/test/API/macosx/lc-note/additional-registers/main.c
new file mode 100644
index 0000000000000..70679942daf06
--- /dev/null
+++ b/lldb/test/API/macosx/lc-note/additional-registers/main.c
@@ -0,0 +1,11 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc, char **argv) {
+
+  char *heap_buf = (char *)malloc(80);
+  strcpy(heap_buf, "this is a string on the heap");
+
+  return 0; // break here
+}



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