diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.h b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.h
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.h
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.h
@@ -95,6 +95,10 @@
 
   void *GetGPRBuffer() override { return &m_gpr_arm64; }
 
+  // GetGPRBufferSize returns sizeof arm64 GPR ptrace buffer, it is different
+  // from GetGPRSize which returns sizeof RegisterInfoPOSIX_arm64::GPR.
+  size_t GetGPRBufferSize() { return sizeof(m_gpr_arm64); }
+
   void *GetFPRBuffer() override { return &m_fpr; }
 
   size_t GetFPRSize() override { return sizeof(m_fpr); }
@@ -106,7 +110,7 @@
 
   bool m_sve_header_is_valid;
 
-  RegisterInfoPOSIX_arm64::GPR m_gpr_arm64; // 64-bit general purpose registers.
+  struct user_pt_regs m_gpr_arm64; // 64-bit general purpose registers.
 
   RegisterInfoPOSIX_arm64::FPU
       m_fpr; // floating-point registers including extended register sets.
diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.cpp b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.cpp
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.cpp
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm64.cpp
@@ -936,9 +936,9 @@
 
   struct iovec ioVec;
   ioVec.iov_base = GetGPRBuffer();
-  ioVec.iov_len = GetGPRSize();
+  ioVec.iov_len = GetGPRBufferSize();
 
-  error = ReadRegisterSet(&ioVec, GetGPRSize(), NT_PRSTATUS);
+  error = ReadRegisterSet(&ioVec, GetGPRBufferSize(), NT_PRSTATUS);
 
   if (error.Success())
     m_gpr_is_valid = true;
@@ -953,11 +953,11 @@
 
   struct iovec ioVec;
   ioVec.iov_base = GetGPRBuffer();
-  ioVec.iov_len = GetGPRSize();
+  ioVec.iov_len = GetGPRBufferSize();
 
   m_gpr_is_valid = false;
 
-  return WriteRegisterSet(&ioVec, GetGPRSize(), NT_PRSTATUS);
+  return WriteRegisterSet(&ioVec, GetGPRBufferSize(), NT_PRSTATUS);
 }
 
 Status NativeRegisterContextLinux_arm64::ReadFPR() {
diff --git a/lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h b/lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h
--- a/lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h
+++ b/lldb/source/Plugins/Process/Utility/RegisterInfoPOSIX_arm64.h
@@ -29,6 +29,7 @@
   };
 
   // based on RegisterContextDarwin_arm64.h
+  LLVM_PACKED_START
   struct GPR {
     uint64_t x[29]; // x0-x28
     uint64_t fp;    // x29
@@ -37,6 +38,7 @@
     uint64_t pc;    // pc
     uint32_t cpsr;  // cpsr
   };
+  LLVM_PACKED_END
 
   // based on RegisterContextDarwin_arm64.h
   struct VReg {