[lldb] Fix offset intersection bug between MPX and AVX registers

Summary:
This change increases the offset of MPX registers (by 128) so they
do not overlap with the offset associated with AVX registers. That was
causing MPX data in GDBRemoteRegisterContext::m_reg_data to get overwritten.

Reviewers: labath

Reviewed By: labath

Subscribers: JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D68874

5 files changed, 21 insertions, 4 deletions

diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.cpp b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.cpp
index 3ae215e7573..3186b6cf39a 100644
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.cpp
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.cpp
@@ -34,7 +34,7 @@ Status NativeRegisterContextLinux::ReadRegisterRaw(uint32_t reg_index,
   if (!reg_info)
     return Status("register %" PRIu32 " not found", reg_index);
 
-  return DoReadRegisterValue(reg_info->byte_offset, reg_info->name,
+  return DoReadRegisterValue(GetPtraceOffset(reg_index), reg_info->name,
                              reg_info->byte_size, reg_value);
 }
 
@@ -91,7 +91,8 @@ NativeRegisterContextLinux::WriteRegisterRaw(uint32_t reg_index,
                   "for write register index %" PRIu32,
                   __FUNCTION__, reg_to_write);
 
-  return DoWriteRegisterValue(reg_info->byte_offset, reg_info->name, reg_value);
+  return DoWriteRegisterValue(GetPtraceOffset(reg_index), reg_info->name,
+                              reg_value);
 }
 
 Status NativeRegisterContextLinux::ReadGPR() {
diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.h b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.h
index 82894852c13..3b98310c196 100644
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.h
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux.h
@@ -60,6 +60,10 @@ protected:
 
   virtual size_t GetFPRSize() = 0;
 
+  virtual uint32_t GetPtraceOffset(uint32_t reg_index) {
+    return GetRegisterInfoAtIndex(reg_index)->byte_offset;
+  }
+
   // The Do*** functions are executed on the privileged thread and can perform
   // ptrace
   // operations directly.
diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp
index 49f1d44b39d..0818630db62 100644
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp
@@ -1213,4 +1213,11 @@ uint32_t NativeRegisterContextLinux_x86_64::NumSupportedHardwareWatchpoints() {
   return 4;
 }
 
+uint32_t
+NativeRegisterContextLinux_x86_64::GetPtraceOffset(uint32_t reg_index) {
+  // If register is MPX, remove extra factor from gdb offset
+  return GetRegisterInfoAtIndex(reg_index)->byte_offset -
+         (IsMPX(reg_index) ? 128 : 0);
+}
+
 #endif // defined(__i386__) || defined(__x86_64__)
diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.h b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.h
index 6031ddb0a7a..58b749025c5 100644
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.h
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.h
@@ -75,6 +75,8 @@ protected:
 
   Status WriteFPR() override;
 
+  uint32_t GetPtraceOffset(uint32_t reg_index) override;
+
 private:
   // Private member types.
   enum class XStateType { Invalid, FXSAVE, XSAVE };
diff --git a/lldb/source/Plugins/Process/Utility/RegisterInfos_x86_64.h b/lldb/source/Plugins/Process/Utility/RegisterInfos_x86_64.h
index 4a3b3c73fd6..af3027afa73 100644
--- a/lldb/source/Plugins/Process/Utility/RegisterInfos_x86_64.h
+++ b/lldb/source/Plugins/Process/Utility/RegisterInfos_x86_64.h
@@ -25,15 +25,18 @@
    LLVM_EXTENSION offsetof(FPR, xsave) +                                       \
    LLVM_EXTENSION offsetof(XSAVE, ymmh[0]) + (32 * reg_index))
 
+// Guarantees BNDR/BNDC offsets do not overlap with YMM offsets.
+#define GDB_REMOTE_OFFSET 128
+
 #define BNDR_OFFSET(reg_index)                                                 \
   (LLVM_EXTENSION offsetof(UserArea, fpr) +                                    \
    LLVM_EXTENSION offsetof(FPR, xsave) +                                       \
-   LLVM_EXTENSION offsetof(XSAVE, mpxr[reg_index]))
+   LLVM_EXTENSION offsetof(XSAVE, mpxr[reg_index]) + GDB_REMOTE_OFFSET)
 
 #define BNDC_OFFSET(reg_index)                                                 \
   (LLVM_EXTENSION offsetof(UserArea, fpr) +                                    \
    LLVM_EXTENSION offsetof(FPR, xsave) +                                       \
-   LLVM_EXTENSION offsetof(XSAVE, mpxc[reg_index]))
+   LLVM_EXTENSION offsetof(XSAVE, mpxc[reg_index]) + GDB_REMOTE_OFFSET)
 
 #ifdef DECLARE_REGISTER_INFOS_X86_64_STRUCT