Index: source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp
===================================================================
--- source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp
+++ source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp
@@ -9,6 +9,9 @@
 
 #if defined(__i386__) || defined(__x86_64__)
 
+#include "Plugins/Process/Utility/RegisterContextLinux_i386.h"
+#include "Plugins/Process/Utility/RegisterContextLinux_x86_64.h"
+
 #include "NativeRegisterContextLinux_x86_64.h"
 
 #include "lldb/Core/Log.h"
@@ -17,9 +20,6 @@
 #include "lldb/Core/RegisterValue.h"
 #include "lldb/Host/HostInfo.h"
 
-#include "Plugins/Process/Utility/RegisterContextLinux_i386.h"
-#include "Plugins/Process/Utility/RegisterContextLinux_x86_64.h"
-
 using namespace lldb_private;
 using namespace lldb_private::process_linux;
 
@@ -49,6 +49,7 @@
         lldb_ss_i386,
         lldb_ds_i386,
         lldb_es_i386,
+        lldb_orig_eax_i386,
         lldb_ax_i386,
         lldb_bx_i386,
         lldb_cx_i386,
@@ -158,6 +159,7 @@
         lldb_ss_x86_64,
         lldb_ds_x86_64,
         lldb_es_x86_64,
+        lldb_orig_rax_x86_64,
         lldb_eax_x86_64,
         lldb_ebx_x86_64,
         lldb_ecx_x86_64,
Index: source/Plugins/Process/Utility/RegisterContextLinux_i386.cpp
===================================================================
--- source/Plugins/Process/Utility/RegisterContextLinux_i386.cpp
+++ source/Plugins/Process/Utility/RegisterContextLinux_i386.cpp
@@ -7,8 +7,8 @@
 //
 //===---------------------------------------------------------------------===//
 
-#include "RegisterContextPOSIX_x86.h"
 #include "RegisterContextLinux_i386.h"
+#include "RegisterContextPOSIX_x86.h"
 
 using namespace lldb_private;
 using namespace lldb;
@@ -26,7 +26,7 @@
     uint32_t es;
     uint32_t fs;
     uint32_t gs;
-    uint32_t orig_ax;
+    uint32_t orig_eax;
     uint32_t eip;
     uint32_t cs;
     uint32_t eflags;
@@ -91,9 +91,11 @@
 //---------------------------------------------------------------------------
 // Include RegisterInfos_i386 to declare our g_register_infos_i386 structure.
 //---------------------------------------------------------------------------
+#define LINUX
 #define DECLARE_REGISTER_INFOS_I386_STRUCT
 #include "RegisterInfos_i386.h"
 #undef DECLARE_REGISTER_INFOS_I386_STRUCT
+#undef LINUX
 
 RegisterContextLinux_i386::RegisterContextLinux_i386(const ArchSpec &target_arch) :
     RegisterInfoInterface(target_arch)
Index: source/Plugins/Process/Utility/RegisterContextLinux_x86_64.cpp
===================================================================
--- source/Plugins/Process/Utility/RegisterContextLinux_x86_64.cpp
+++ source/Plugins/Process/Utility/RegisterContextLinux_x86_64.cpp
@@ -8,9 +8,10 @@
 //===---------------------------------------------------------------------===//
 
 #include <vector>
-#include "RegisterContextPOSIX_x86.h"
-#include "RegisterContextLinux_i386.h"
+
 #include "RegisterContextLinux_x86_64.h"
+#include "RegisterContextLinux_i386.h"
+#include "RegisterContextPOSIX_x86.h"
 
 using namespace lldb_private;
 using namespace lldb;
@@ -32,7 +33,7 @@
     uint64_t rdx;
     uint64_t rsi;
     uint64_t rdi;
-    uint64_t orig_ax;
+    uint64_t orig_rax;
     uint64_t rip;
     uint64_t cs;
     uint64_t rflags;
@@ -81,9 +82,11 @@
 //---------------------------------------------------------------------------
 // Include RegisterInfos_x86_64 to declare our g_register_infos_x86_64 structure.
 //---------------------------------------------------------------------------
+#define LINUX
 #define DECLARE_REGISTER_INFOS_X86_64_STRUCT
 #include "RegisterInfos_x86_64.h"
 #undef DECLARE_REGISTER_INFOS_X86_64_STRUCT
+#undef LINUX
 
 static std::vector<lldb_private::RegisterInfo>&
 GetPrivateRegisterInfoVector ()
@@ -109,9 +112,11 @@
         // Include RegisterInfos_x86_64 to update the g_register_infos structure
         //  with x86_64 offsets.
         //---------------------------------------------------------------------------
+        #define LINUX
         #define UPDATE_REGISTER_INFOS_I386_STRUCT_WITH_X86_64_OFFSETS
         #include "RegisterInfos_x86_64.h"
         #undef UPDATE_REGISTER_INFOS_I386_STRUCT_WITH_X86_64_OFFSETS
+        #undef LINUX
     }
 
     return &g_register_infos[0];
Index: source/Plugins/Process/Utility/RegisterInfos_i386.h
===================================================================
--- source/Plugins/Process/Utility/RegisterInfos_i386.h
+++ source/Plugins/Process/Utility/RegisterInfos_i386.h
@@ -114,6 +114,9 @@
     DEFINE_GPR(ss,     NULL,    LLDB_INVALID_REGNUM, dwarf_ss_i386,       LLDB_INVALID_REGNUM,       gdb_ss_i386),
     DEFINE_GPR(ds,     NULL,    LLDB_INVALID_REGNUM, dwarf_ds_i386,       LLDB_INVALID_REGNUM,       gdb_ds_i386),
     DEFINE_GPR(es,     NULL,    LLDB_INVALID_REGNUM, dwarf_es_i386,       LLDB_INVALID_REGNUM,       gdb_es_i386),
+#ifdef LINUX
+    DEFINE_GPR(orig_eax,     NULL,    LLDB_INVALID_REGNUM,     LLDB_INVALID_REGNUM,     LLDB_INVALID_REGNUM,       LLDB_INVALID_REGNUM),
+#endif
 
     DEFINE_GPR_PSEUDO_16(ax,  eax),
     DEFINE_GPR_PSEUDO_16(bx,  ebx),
Index: source/Plugins/Process/Utility/RegisterInfos_x86_64.h
===================================================================
--- source/Plugins/Process/Utility/RegisterInfos_x86_64.h
+++ source/Plugins/Process/Utility/RegisterInfos_x86_64.h
@@ -125,6 +125,9 @@
     DEFINE_GPR(ss,     NULL,    gcc_dwarf_ss_x86_64,     gcc_dwarf_ss_x86_64,     LLDB_INVALID_REGNUM,       gdb_ss_x86_64),
     DEFINE_GPR(ds,     NULL,    gcc_dwarf_ds_x86_64,     gcc_dwarf_ds_x86_64,     LLDB_INVALID_REGNUM,       gdb_ds_x86_64),
     DEFINE_GPR(es,     NULL,    gcc_dwarf_es_x86_64,     gcc_dwarf_es_x86_64,     LLDB_INVALID_REGNUM,       gdb_es_x86_64),
+#ifdef LINUX
+    DEFINE_GPR(orig_rax,     NULL,    LLDB_INVALID_REGNUM,     LLDB_INVALID_REGNUM,     LLDB_INVALID_REGNUM,       LLDB_INVALID_REGNUM),
+#endif
 
     DEFINE_GPR_PSEUDO_32(eax, rax),
     DEFINE_GPR_PSEUDO_32(ebx, rbx),
@@ -330,7 +333,9 @@
     UPDATE_GPR_INFO(ss,     ss);
     UPDATE_GPR_INFO(ds,     ds);
     UPDATE_GPR_INFO(es,     es);
-
+#ifdef LINUX
+    UPDATE_GPR_INFO(orig_eax, orig_rax);
+#endif
     UPDATE_GPR_INFO(ax,     rax);
     UPDATE_GPR_INFO(bx,     rbx);
     UPDATE_GPR_INFO(cx,     rcx);
Index: source/Plugins/Process/Utility/lldb-x86-register-enums.h
===================================================================
--- source/Plugins/Process/Utility/lldb-x86-register-enums.h
+++ source/Plugins/Process/Utility/lldb-x86-register-enums.h
@@ -36,7 +36,9 @@
         lldb_ss_i386,
         lldb_ds_i386,
         lldb_es_i386,
-
+#ifdef liblldb_RegisterContextLinux_i386_H_
+        lldb_orig_eax_i386,
+#endif
         k_first_alias_i386,
         lldb_ax_i386 = k_first_alias_i386,
         lldb_bx_i386,
@@ -152,7 +154,9 @@
         lldb_ss_x86_64,
         lldb_ds_x86_64,
         lldb_es_x86_64,
-
+#ifdef liblldb_RegisterContextLinux_x86_64_H_
+        lldb_orig_rax_x86_64,
+#endif
         k_first_alias_x86_64,
         lldb_eax_x86_64 = k_first_alias_x86_64,
         lldb_ebx_x86_64,
Index: test/expression_command/expr-in-syscall/TestExpressionInSyscall.py
===================================================================
--- test/expression_command/expr-in-syscall/TestExpressionInSyscall.py
+++ test/expression_command/expr-in-syscall/TestExpressionInSyscall.py
@@ -17,7 +17,6 @@
         self.buildDsym()
         self.expr_syscall()
 
-    @expectedFailureAll("llvm.org/pr23659", oslist=["linux"], archs=["i386", "x86_64"])
     @dwarf_test
     def test_setpgid_with_dwarf(self):
         self.buildDwarf()