Add Windows ehcont section support (/guard:ehcont).

Add option /guard:ehcont

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D96709

diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
index b762bf9..c668645 100644 (file)
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -3523,7 +3523,8 @@ Execute ``clang-cl /?`` to see a list of supported options:
       /Gs                     Use stack probes (default)
       /Gs<value>              Set stack probe size (default 4096)
       /guard:<value>          Enable Control Flow Guard with /guard:cf,
-                              or only the table with /guard:cf,nochecks
+                              or only the table with /guard:cf,nochecks.
+                              Enable EH Continuation Guard with /guard:ehcont
       /Gv                     Set __vectorcall as a default calling convention
       /Gw-                    Don't put each data item in its own section
       /Gw                     Put each data item in its own section

diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index 832f7fa..50503db 100644 (file)
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -42,6 +42,7 @@ CODEGENOPT(Backchain         , 1, 0) ///< -mbackchain
 CODEGENOPT(IgnoreXCOFFVisibility         , 1, 0) ///< -mignore-xcoff-visibility
 CODEGENOPT(ControlFlowGuardNoChecks  , 1, 0) ///< -cfguard-no-checks
 CODEGENOPT(ControlFlowGuard  , 1, 0) ///< -cfguard
+CODEGENOPT(EHContGuard       , 1, 0) ///< -ehcontguard
 CODEGENOPT(CXAAtExit         , 1, 1) ///< Use __cxa_atexit for calling destructors.
 CODEGENOPT(RegisterGlobalDtorsWithAtExit, 1, 1) ///< Use atexit or __cxa_atexit to register global destructors.
 CODEGENOPT(CXXCtorDtorAliases, 1, 0) ///< Emit complete ctors/dtors as linker

diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 72213ed..2f57895 100644 (file)
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -4859,6 +4859,9 @@ def cfguard_no_checks : Flag<["-"], "cfguard-no-checks">,
 def cfguard : Flag<["-"], "cfguard">,
     HelpText<"Emit Windows Control Flow Guard tables and checks">,
     MarshallingInfoFlag<CodeGenOpts<"ControlFlowGuard">>;
+def ehcontguard : Flag<["-"], "ehcontguard">,
+    HelpText<"Emit Windows EH Continuation Guard tables">,
+    MarshallingInfoFlag<CodeGenOpts<"EHContGuard">>;
 
 def fdenormal_fp_math_f32_EQ : Joined<["-"], "fdenormal-fp-math-f32=">,
    Group<f_Group>;
@@ -5857,7 +5860,8 @@ def _SLASH_Fo : CLCompileJoined<"Fo">,
   HelpText<"Set output object file (with /c)">,
   MetaVarName<"<file or dir/>">;
 def _SLASH_guard : CLJoined<"guard:">,
-  HelpText<"Enable Control Flow Guard with /guard:cf, or only the table with /guard:cf,nochecks">;
+  HelpText<"Enable Control Flow Guard with /guard:cf, or only the table with /guard:cf,nochecks. "
+           "Enable EH Continuation Guard with /guard:ehcont">;
 def _SLASH_GX : CLFlag<"GX">,
   HelpText<"Deprecated; use /EHsc">;
 def _SLASH_GX_ : CLFlag<"GX-">,

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 802a13f..b23d995 100644 (file)
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -552,6 +552,10 @@ void CodeGenModule::Release() {
     // Function ID tables for Control Flow Guard (cfguard=1).
     getModule().addModuleFlag(llvm::Module::Warning, "cfguard", 1);
   }
+  if (CodeGenOpts.EHContGuard) {
+    // Function ID tables for EH Continuation Guard.
+    getModule().addModuleFlag(llvm::Module::Warning, "ehcontguard", 1);
+  }
   if (CodeGenOpts.OptimizationLevel > 0 && CodeGenOpts.StrictVTablePointers) {
     // We don't support LTO with 2 with different StrictVTablePointers
     // FIXME: we could support it by stripping all the information introduced

diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index df2b207..eb09d72 100644 (file)
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7076,14 +7076,19 @@ void Clang::AddClangCLArgs(const ArgList &Args, types::ID InputType,
 
   if (Arg *A = Args.getLastArg(options::OPT__SLASH_guard)) {
     StringRef GuardArgs = A->getValue();
-    // The only valid options are "cf", "cf,nochecks", and "cf-".
+    // The only valid options are "cf", "cf,nochecks", "cf-", "ehcont" and
+    // "ehcont-".
     if (GuardArgs.equals_lower("cf")) {
       // Emit CFG instrumentation and the table of address-taken functions.
       CmdArgs.push_back("-cfguard");
     } else if (GuardArgs.equals_lower("cf,nochecks")) {
       // Emit only the table of address-taken functions.
       CmdArgs.push_back("-cfguard-no-checks");
-    } else if (GuardArgs.equals_lower("cf-")) {
+    } else if (GuardArgs.equals_lower("ehcont")) {
+      // Emit EH continuation table.
+      CmdArgs.push_back("-ehcontguard");
+    } else if (GuardArgs.equals_lower("cf-") ||
+               GuardArgs.equals_lower("ehcont-")) {
       // Do nothing, but we might want to emit a security warning in future.
     } else {
       D.Diag(diag::err_drv_invalid_value) << A->getSpelling() << GuardArgs;

diff --git a/clang/lib/Driver/ToolChains/MSVC.cpp b/clang/lib/Driver/ToolChains/MSVC.cpp
index c95c5b6..96de023 100644 (file)
--- a/clang/lib/Driver/ToolChains/MSVC.cpp
+++ b/clang/lib/Driver/ToolChains/MSVC.cpp
@@ -509,6 +509,10 @@ void visualstudio::Linker::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back("-guard:cf");
     } else if (GuardArgs.equals_lower("cf-")) {
       CmdArgs.push_back("-guard:cf-");
+    } else if (GuardArgs.equals_lower("ehcont")) {
+      CmdArgs.push_back("-guard:ehcont");
+    } else if (GuardArgs.equals_lower("ehcont-")) {
+      CmdArgs.push_back("-guard:ehcont-");
     }
   }
 

diff --git a/clang/test/CodeGen/cfguardtable.c b/clang/test/CodeGen/cfguardtable.c
index 05284f6..c0212ae 100644 (file)
--- a/clang/test/CodeGen/cfguardtable.c
+++ b/clang/test/CodeGen/cfguardtable.c
@@ -1,8 +1,10 @@
-// RUN: %clang_cc1 -cfguard-no-checks -emit-llvm %s -o - | FileCheck %s -check-prefix=CFGUARDNOCHECKS\r
-// RUN: %clang_cc1 -cfguard -emit-llvm %s -o - | FileCheck %s -check-prefix=CFGUARD\r
-\r
-void f() {}\r
-\r
-// Check that the cfguard metadata flag gets correctly set on the module.\r
-// CFGUARDNOCHECKS: !"cfguard", i32 1}\r
-// CFGUARD: !"cfguard", i32 2}\r
+// RUN: %clang_cc1 -cfguard-no-checks -emit-llvm %s -o - | FileCheck %s -check-prefix=CFGUARDNOCHECKS
+// RUN: %clang_cc1 -cfguard -emit-llvm %s -o - | FileCheck %s -check-prefix=CFGUARD
+// RUN: %clang_cc1 -ehcontguard -emit-llvm %s -o - | FileCheck %s -check-prefix=EHCONTGUARD
+
+void f() {}
+
+// Check that the cfguard metadata flag gets correctly set on the module.
+// CFGUARDNOCHECKS: !"cfguard", i32 1}
+// CFGUARD: !"cfguard", i32 2}
+// EHCONTGUARD: !"ehcontguard", i32 1}

diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 0e07ea4..7d83b3d 100644 (file)
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -614,6 +614,13 @@
 // RUN: %clang_cl /guard:nochecks -### -- %s 2>&1 | FileCheck -check-prefix=CFGUARDNOCHECKSINVALID %s
 // CFGUARDNOCHECKSINVALID: invalid value 'nochecks' in '/guard:'
 
+// RUN: %clang_cl  -### -- %s 2>&1 | FileCheck -check-prefix=NOEHCONTGUARD %s
+// RUN: %clang_cl /guard:ehcont- -### -- %s 2>&1 | FileCheck -check-prefix=NOEHCONTGUARD %s
+// NOEHCONTGUARD-NOT: -ehcontguard
+
+// RUN: %clang_cl /guard:ehcont -### -- %s 2>&1 | FileCheck -check-prefix=EHCONTGUARD %s
+// EHCONTGUARD: -ehcontguard
+
 // RUN: %clang_cl /guard:foo -### -- %s 2>&1 | FileCheck -check-prefix=CFGUARDINVALID %s
 // CFGUARDINVALID: invalid value 'foo' in '/guard:'
 

diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
index 1de11f0..411505c 100644 (file)
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -51,6 +51,9 @@ Non-comprehensive list of changes in this release
 
    Makes programs 10x faster by doing Special New Thing.
 
+* Windows Control-flow Enforcement Technology: the ``-ehcontguard`` option now
+  emits valid unwind entrypoints which are validated when the context is being
+  set during exception handling.
 
 Changes to the LLVM IR
 ----------------------