diff --git a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
index 0591a0d57554..36795e584cfa 100644
--- a/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
+++ b/lldb/source/Plugins/Process/Linux/ProcessMonitor.cpp
@@ -168,9 +168,9 @@ PtraceWrapper(int req, lldb::pid_t pid, void *addr, void *data, size_t data_size
 
     errno = 0;
     if (req == PTRACE_GETREGSET || req == PTRACE_SETREGSET)
-        result = ptrace(static_cast<__ptrace_request>(req), pid, *(unsigned int *)addr, data);
+        result = ptrace(static_cast<__ptrace_request>(req), static_cast<pid_t>(pid), *(unsigned int *)addr, data);
     else
-        result = ptrace(static_cast<__ptrace_request>(req), pid, addr, data);
+        result = ptrace(static_cast<__ptrace_request>(req), static_cast<pid_t>(pid), addr, data);
 
     if (log)
         log->Printf("ptrace(%s, %" PRIu64 ", %p, %p, %zu)=%lX called from file %s line %d",
diff --git a/lldb/source/Plugins/Process/POSIX/POSIXThread.cpp b/lldb/source/Plugins/Process/POSIX/POSIXThread.cpp
index cc759eaad96d..9c0a0016747b 100644
--- a/lldb/source/Plugins/Process/POSIX/POSIXThread.cpp
+++ b/lldb/source/Plugins/Process/POSIX/POSIXThread.cpp
@@ -190,7 +190,17 @@ POSIXThread::GetRegisterContext()
                         reg_interface = new RegisterContextFreeBSD_x86_64(target_arch);
                         break;
                     case llvm::Triple::Linux:
-                        reg_interface = new RegisterContextLinux_x86_64(target_arch);
+                        if (Host::GetArchitecture().GetAddressByteSize() == 4)
+                        {
+                            // 32-bit hosts run with a RegisterContextLinux_i386 context.
+                            reg_interface = static_cast<RegisterInfoInterface*>(new RegisterContextLinux_i386(target_arch));
+                        }
+                        else
+                        {
+                            assert((Host::GetArchitecture().GetAddressByteSize() == 8) && "Register setting path assumes this is a 64-bit host");
+                            // X86_64 hosts know how to work with 64-bit and 32-bit EXEs using the x86_64 register context.
+                            reg_interface = static_cast<RegisterInfoInterface*>(new RegisterContextLinux_x86_64(target_arch));
+                        }
                         break;
                     default:
                         assert(false && "OS not supported");
diff --git a/lldb/source/Plugins/Process/POSIX/RegisterContextLinux_i386.cpp b/lldb/source/Plugins/Process/POSIX/RegisterContextLinux_i386.cpp
index ef5b9e4355bd..f2c1bab9f738 100644
--- a/lldb/source/Plugins/Process/POSIX/RegisterContextLinux_i386.cpp
+++ b/lldb/source/Plugins/Process/POSIX/RegisterContextLinux_i386.cpp
@@ -36,14 +36,30 @@ struct GPR
 
 struct FPR_i386
 {
-    int32_t cwd;
-    int32_t swd;
-    int32_t twd;
-    int32_t fip;
-    int32_t fcs;
-    int32_t foo;
-    int32_t fos;
-    int32_t st_space [20];
+    uint16_t fctrl;         // FPU Control Word (fcw)
+    uint16_t fstat;         // FPU Status Word (fsw)
+    uint16_t ftag;          // FPU Tag Word (ftw)
+    uint16_t fop;           // Last Instruction Opcode (fop)
+    union
+    {
+        struct
+        {
+            uint64_t fip;   // Instruction Pointer
+            uint64_t fdp;   // Data Pointer
+        } x86_64;
+        struct
+        {
+            uint32_t fioff;   // FPU IP Offset (fip)
+            uint32_t fiseg;   // FPU IP Selector (fcs)
+            uint32_t fooff;   // FPU Operand Pointer Offset (foo)
+            uint32_t foseg;   // FPU Operand Pointer Selector (fos)
+        } i386;
+    } ptr;
+    uint32_t mxcsr;         // MXCSR Register State
+    uint32_t mxcsrmask;     // MXCSR Mask
+    MMSReg   stmm[8];       // 8*16 bytes for each FP-reg = 128 bytes
+    XMMReg   xmm[8];        // 8*16 bytes for each XMM-reg = 128 bytes
+    uint32_t padding[56];
 };
 
 struct UserArea
@@ -69,6 +85,7 @@ struct UserArea
 #define DR_SIZE sizeof(UserArea::u_debugreg[0])
 #define DR_OFFSET(reg_index) \
     (LLVM_EXTENSION offsetof(UserArea, u_debugreg[reg_index]))
+#define FPR_SIZE(reg) sizeof(((FPR_i386*)NULL)->reg)
 
 //---------------------------------------------------------------------------
 // Include RegisterInfos_i386 to declare our g_register_infos_i386 structure.
diff --git a/lldb/source/Plugins/Process/POSIX/RegisterInfos_i386.h b/lldb/source/Plugins/Process/POSIX/RegisterInfos_i386.h
index 7c516568cd62..35cbc70399c1 100644
--- a/lldb/source/Plugins/Process/POSIX/RegisterInfos_i386.h
+++ b/lldb/source/Plugins/Process/POSIX/RegisterInfos_i386.h
@@ -24,7 +24,9 @@
     (LLVM_EXTENSION offsetof(YMM, regname))
 
 // Number of bytes needed to represent a FPR.
+#if !defined(FPR_SIZE)
 #define FPR_SIZE(reg) sizeof(((FXSAVE*)NULL)->reg)
+#endif
 
 // Number of bytes needed to represent the i'th FP register.
 #define FP_SIZE sizeof(((MMSReg*)NULL)->bytes)