[X86] Added support for nocf_check attribute for indirect Branch Tracking
X86 Supports Indirect Branch Tracking (IBT) as part of Control-Flow Enforcement Technology (CET).
IBT instruments ENDBR instructions used to specify valid targets of indirect call / jmp.
The `nocf_check` attribute has two roles in the context of X86 IBT technology:
1. Appertains to a function - do not add ENDBR instruction at the beginning of the function.
2. Appertains to a function pointer - do not track the target function of this pointer by adding nocf_check prefix to the indirect-call instruction.
This patch implements `nocf_check` context for Indirect Branch Tracking.
It also auto generates `nocf_check` prefixes before indirect branchs to jump tables that are guarded by range checks.
Differential Revision: https://reviews.llvm.org/D41879
llvm-svn: 327767
diff --git a/llvm/lib/Transforms/IPO/ForceFunctionAttrs.cpp b/llvm/lib/Transforms/IPO/ForceFunctionAttrs.cpp
index 325a5d7..d10b4f4a 100644
--- a/llvm/lib/Transforms/IPO/ForceFunctionAttrs.cpp
+++ b/llvm/lib/Transforms/IPO/ForceFunctionAttrs.cpp
@@ -42,6 +42,7 @@
.Case("nonlazybind", Attribute::NonLazyBind)
.Case("noredzone", Attribute::NoRedZone)
.Case("noreturn", Attribute::NoReturn)
+ .Case("nocf_check", Attribute::NoCfCheck)
.Case("norecurse", Attribute::NoRecurse)
.Case("nounwind", Attribute::NoUnwind)
.Case("optnone", Attribute::OptimizeNone)
diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
index 2fc987d..ef39f21 100644
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -696,6 +696,7 @@
case Attribute::StackProtectStrong:
case Attribute::StrictFP:
case Attribute::UWTable:
+ case Attribute::NoCfCheck:
break;
}