[Lldb-commits] [PATCH] D27161: Fix floating point register reads x86_64 linux on targets with no AVX support

[Pavel Labath via Phabricator via lldb-commits]

labath created this revision.
labath added reviewers: tberghammer, valentinagiusti.
labath added a subscriber: lldb-commits.

On for 64-bit targets, the correct register set to read the fxsave are is
NT_PRFPREG (only 32-bit targets need NT_PRXFPREG, presumably for historic
reasons). Reference:
https://github.com/torvalds/linux/blob/v4.8/arch/x86/kernel/ptrace.c#L1261.


https://reviews.llvm.org/D27161

Files:
  source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp


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
@@ -20,6 +20,8 @@
 #include "Plugins/Process/Utility/RegisterContextLinux_i386.h"
 #include "Plugins/Process/Utility/RegisterContextLinux_x86_64.h"
 
+#include <linux/elf.h>
+
 using namespace lldb_private;
 using namespace lldb_private::process_linux;
 
@@ -218,6 +220,12 @@
 #define NT_PRXFPREG 0x46e62b7f
 #endif
 
+// On x86_64 NT_PRFPREG is used to access the FXSAVE area. On i386, we need to
+// use NT_PRXFPREG.
+static inline unsigned int fxsr_regset(const ArchSpec &arch) {
+  return arch.GetAddressByteSize() == 8 ? NT_PRFPREG : NT_PRXFPREG;
+}
+
 // ----------------------------------------------------------------------------
 // Required MPX define.
 // ----------------------------------------------------------------------------
@@ -235,6 +243,8 @@
 #define mask_XSTATE_BNDCFG (1ULL << 4)
 #define mask_XSTATE_MPX (mask_XSTATE_BNDREGS | mask_XSTATE_BNDCFG)
 
+
+
 NativeRegisterContextLinux *
 NativeRegisterContextLinux::CreateHostNativeRegisterContextLinux(
     const ArchSpec &target_arch, NativeThreadProtocol &native_thread,
@@ -852,8 +862,9 @@
 Error NativeRegisterContextLinux_x86_64::WriteFPR() {
   switch (m_xstate_type) {
   case XStateType::FXSAVE:
-      return WriteRegisterSet(&m_iovec, sizeof(m_fpr.xstate.xsave),
-                              NT_PRXFPREG);
+    return WriteRegisterSet(
+        &m_iovec, sizeof(m_fpr.xstate.xsave),
+        fxsr_regset(GetRegisterInfoInterface().GetTargetArchitecture()));
   case XStateType::XSAVE:
     return WriteRegisterSet(&m_iovec, sizeof(m_fpr.xstate.xsave),
                             NT_X86_XSTATE);
@@ -957,7 +968,9 @@
       return error;
     }
   }
-  error = ReadRegisterSet(&m_iovec, sizeof(m_fpr.xstate.xsave), NT_PRXFPREG);
+  error = ReadRegisterSet(
+      &m_iovec, sizeof(m_fpr.xstate.xsave),
+      fxsr_regset(GetRegisterInfoInterface().GetTargetArchitecture()));
   if (!error.Fail()) {
     m_xstate_type = XStateType::FXSAVE;
     return error;


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