Save and restore GDT in UEFI loader.

Author: eyalz800

uefi_loader/src/main.cpp

@@ -10,10 +10,14 @@ extern "C" {
 #include <Protocol/LoadedImage.h>
 #include <Protocol/MpService.h>
 }
+#include "zpp/scope_guard.h"
+#include "zpp/x64/asm.h"
 #include <cstddef>
 #include <cstdint>
 #include <string>
 
+namespace zpp
+{
 /**
  * The boot services.
  */
@@ -112,6 +116,11 @@ static int call_on_cpu(std::size_t cpuid,
 {
     int result = -1;
 
+    // Save this GDT and restore it at function exit.
+    alignas(0x10) unsigned char gdt_layout[0x10]{};
+    x64::sgdt(gdt_layout);
+    scope_guard restore_gdt = [&] { x64::lgdt(gdt_layout); };
+
     // If this is the main CPU, just call the user function.
     if (0 == cpuid) {
         return function(context);
@@ -383,3 +392,5 @@ extern "C" EFI_STATUS EFIAPI uefi_main(EFI_HANDLE image_handle,
     // Return success anyway, no image was found is considered ok.
     return EFI_SUCCESS;
 }
+
+} // namespace zpp

uefi_loader/uefi_loader.vcxproj

@@ -77,30 +77,30 @@
     <NMakeCleanCommandLine>C:\Windows\sysnative\bash -c "make clean"</NMakeCleanCommandLine>
     <NMakeReBuildCommandLine>C:\Windows\sysnative\bash -c "make clean &amp;&amp; make"</NMakeReBuildCommandLine>
     <NMakePreprocessorDefinitions>WIN32;_DEBUG;$(NMakePreprocessorDefinitions)</NMakePreprocessorDefinitions>
-    <NMakeIncludeSearchPath>include;../loader/include;C:/Temp/edk2-UDK2018/MdePkg/Include</NMakeIncludeSearchPath>
+    <NMakeIncludeSearchPath>include;../hypervisor/include;C:/Temp/edk2-UDK2018/MdePkg/Include</NMakeIncludeSearchPath>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
     <NMakeBuildCommandLine>C:\Windows\sysnative\bash -c make</NMakeBuildCommandLine>
     <NMakeCleanCommandLine>C:\Windows\sysnative\bash -c "make clean"</NMakeCleanCommandLine>
     <NMakeReBuildCommandLine>C:\Windows\sysnative\bash -c "make clean &amp;&amp; make"</NMakeReBuildCommandLine>
     <NMakePreprocessorDefinitions>_DEBUG;$(NMakePreprocessorDefinitions)</NMakePreprocessorDefinitions>
-    <NMakeIncludeSearchPath>include;../loader/include;C:/Temp/edk2-UDK2018/MdePkg/Include</NMakeIncludeSearchPath>
+    <NMakeIncludeSearchPath>include;../hypervisor/include;C:/Temp/edk2-UDK2018/MdePkg/Include</NMakeIncludeSearchPath>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">
     <NMakeBuildCommandLine>C:\Windows\sysnative\bash -c "make mode=release"</NMakeBuildCommandLine>
     <NMakeOutput>hypervisor.exe</NMakeOutput>
     <NMakeCleanCommandLine>C:\Windows\sysnative\bash -c "make clean"</NMakeCleanCommandLine>
     <NMakeReBuildCommandLine>C:\Windows\sysnative\bash -c "make clean &amp;&amp; make mode=release"</NMakeReBuildCommandLine>
     <NMakePreprocessorDefinitions>WIN32;NDEBUG;$(NMakePreprocessorDefinitions)</NMakePreprocessorDefinitions>
-    <NMakeIncludeSearchPath>include;../loader/include;C:/Temp/edk2-UDK2018/MdePkg/Include</NMakeIncludeSearchPath>
+    <NMakeIncludeSearchPath>include;../hypervisor/include;C:/Temp/edk2-UDK2018/MdePkg/Include</NMakeIncludeSearchPath>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'">
     <NMakeBuildCommandLine>C:\Windows\sysnative\bash -c "make mode=release"</NMakeBuildCommandLine>
     <NMakeOutput>hypervisor.exe</NMakeOutput>
     <NMakeCleanCommandLine>C:\Windows\sysnative\bash -c "make clean"</NMakeCleanCommandLine>
     <NMakeReBuildCommandLine>C:\Windows\sysnative\bash -c "make clean &amp;&amp; make mode=release"</NMakeReBuildCommandLine>
     <NMakePreprocessorDefinitions>NDEBUG;$(NMakePreprocessorDefinitions)</NMakePreprocessorDefinitions>
-    <NMakeIncludeSearchPath>include;../loader/include;C:/Temp/edk2-UDK2018/MdePkg/Include</NMakeIncludeSearchPath>
+    <NMakeIncludeSearchPath>include;../hypervisor/include;C:/Temp/edk2-UDK2018/MdePkg/Include</NMakeIncludeSearchPath>
   </PropertyGroup>
   <ItemDefinitionGroup>
   </ItemDefinitionGroup>