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
@@ -706,6 +706,34 @@
         assert (false && "how do we save the floating point registers?");
         error.SetErrorString ("unsure how to save the floating point registers");
     }
+    /** The following code is specific to Linux x86 based architectures,
+     *  where the register orig_eax (32 bit)/orig_rax (64 bit) is set to
+     *  -1 to solve the bug 23659, such a setting prevents the automatic
+     *  decrement of the instruction pointer which was causing the SIGILL
+     *  exception.
+     * **/
+    llvm::Triple t_triple = GetRegisterInfoInterface().GetTargetArchitecture().GetTriple();
+
+        if (t_triple.getOS() == llvm::Triple::Linux &&
+           (t_triple.getArch() == llvm::Triple::x86 ||
+            t_triple.getArch() == llvm::Triple::x86_64))
+        {
+            RegisterValue value((uint64_t) -1);
+            const RegisterInfo *reg_info = GetRegisterInfoInterface().GetDynamicRegisterInfo("orig_eax");
+            if (reg_info == nullptr)
+                reg_info = GetRegisterInfoInterface().GetDynamicRegisterInfo("orig_rax");
+
+            if (reg_info != nullptr) {
+                NativeProcessProtocolSP process_sp(m_thread.GetProcess());
+                if (!process_sp)
+                    return Error("NativeProcessProtocol is NULL");
+
+                NativeProcessLinux* process_p = static_cast<NativeProcessLinux*>(process_sp.get());
+                return process_p->DoOperation([&] {
+                    return DoWriteRegisterValue(reg_info->byte_offset,reg_info->name,value);
+                });
+            }
+        }
 
     return error;
 }
Index: source/Plugins/Process/Utility/RegisterContextLinux_i386.h
===================================================================
--- source/Plugins/Process/Utility/RegisterContextLinux_i386.h
+++ source/Plugins/Process/Utility/RegisterContextLinux_i386.h
@@ -29,6 +29,12 @@
 
     uint32_t
     GetUserRegisterCount () const override;
+
+    const std::vector<lldb_private::RegisterInfo> *
+    GetDynamicRegisterInfoP() const override;
+
+private:
+    std::vector<lldb_private::RegisterInfo> d_register_infos;
 };
 
 #endif
Index: source/Plugins/Process/Utility/RegisterContextLinux_i386.cpp
===================================================================
--- source/Plugins/Process/Utility/RegisterContextLinux_i386.cpp
+++ source/Plugins/Process/Utility/RegisterContextLinux_i386.cpp
@@ -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;
@@ -98,6 +98,9 @@
 RegisterContextLinux_i386::RegisterContextLinux_i386(const ArchSpec &target_arch) :
     RegisterInfoInterface(target_arch)
 {
+    RegisterInfo orig_ax = { "orig_eax", NULL, sizeof(((GPR*)NULL)->orig_eax), (LLVM_EXTENSION offsetof(GPR, orig_eax)), eEncodingUint, \
+              eFormatHex, { LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM }, NULL, NULL };
+    d_register_infos.push_back(orig_ax);
 }
 
 size_t
@@ -131,3 +134,9 @@
 {
     return static_cast<uint32_t> (k_num_user_registers_i386);
 }
+
+const std::vector<lldb_private::RegisterInfo> *
+RegisterContextLinux_i386::GetDynamicRegisterInfoP() const
+{
+    return &d_register_infos;
+}
Index: source/Plugins/Process/Utility/RegisterContextLinux_x86_64.h
===================================================================
--- source/Plugins/Process/Utility/RegisterContextLinux_x86_64.h
+++ source/Plugins/Process/Utility/RegisterContextLinux_x86_64.h
@@ -30,10 +30,15 @@
     uint32_t
     GetUserRegisterCount () const override;
 
+    const std::vector<lldb_private::RegisterInfo> *
+    GetDynamicRegisterInfoP() const override;
+
 private:
     const lldb_private::RegisterInfo *m_register_info_p;
     uint32_t m_register_info_count;
     uint32_t m_user_register_count;
+    std::vector<lldb_private::RegisterInfo> d_register_infos;
+
 };
 
 #endif
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
@@ -32,7 +32,7 @@
     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;
@@ -171,6 +171,9 @@
     m_register_info_count (GetRegisterInfoCount (target_arch)),
     m_user_register_count (GetUserRegisterInfoCount (target_arch))
 {
+    RegisterInfo orig_ax = { "orig_rax", NULL, sizeof(((GPR*)NULL)->orig_rax), (LLVM_EXTENSION offsetof(GPR, orig_rax)), eEncodingUint, \
+              eFormatHex, { LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM, LLDB_INVALID_REGNUM }, NULL, NULL };
+    d_register_infos.push_back(orig_ax);
 }
 
 size_t
@@ -179,6 +182,12 @@
     return sizeof(GPR);
 }
 
+const std::vector<lldb_private::RegisterInfo> *
+RegisterContextLinux_x86_64::GetDynamicRegisterInfoP() const
+{
+    return &d_register_infos;
+}
+
 const RegisterInfo *
 RegisterContextLinux_x86_64::GetRegisterInfo() const
 {
Index: source/Plugins/Process/Utility/RegisterInfoInterface.h
===================================================================
--- source/Plugins/Process/Utility/RegisterInfoInterface.h
+++ source/Plugins/Process/Utility/RegisterInfoInterface.h
@@ -50,6 +50,26 @@
         GetTargetArchitecture() const
             { return m_target_arch; }
 
+        virtual const lldb_private::RegisterInfo *
+        GetDynamicRegisterInfo(const char *reg_name) const
+        {
+            const std::vector <lldb_private::RegisterInfo> * d_register_infos = GetDynamicRegisterInfoP();
+            if(d_register_infos != nullptr)
+            {
+                std::vector <lldb_private::RegisterInfo> ::const_iterator pos = d_register_infos->begin();
+                for(; pos < d_register_infos->end() ; pos++)
+                {
+                    if(::strcmp(reg_name, pos->name) == 0)
+                        return(d_register_infos->data() + (pos - d_register_infos->begin()) );
+                }
+            }
+            return nullptr;
+        }
+
+        virtual const std::vector<lldb_private::RegisterInfo> *
+        GetDynamicRegisterInfoP() const
+        { return nullptr; }
+
     public:
         // FIXME make private.
         lldb_private::ArchSpec m_target_arch;
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()