diff options
Diffstat (limited to 'llvm/lib/CodeGen/WindowsSecureHotPatching.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/WindowsSecureHotPatching.cpp | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/WindowsSecureHotPatching.cpp b/llvm/lib/CodeGen/WindowsSecureHotPatching.cpp index 6267207..fd54190 100644 --- a/llvm/lib/CodeGen/WindowsSecureHotPatching.cpp +++ b/llvm/lib/CodeGen/WindowsSecureHotPatching.cpp @@ -369,6 +369,19 @@ static GlobalVariable *getOrCreateRefVariable( AddrOfOldGV, Twine("__ref_").concat(GV->getName()), nullptr, GlobalVariable::NotThreadLocal); + // RefGV is created with isConstant = false, but we want to place RefGV into + // .rdata, not .data. It is important that the GlobalVariable be mutable + // from the compiler's point of view, so that the optimizer does not remove + // the global variable entirely and replace all references to it with its + // initial value. + // + // When the Windows hot-patch loader applies a hot-patch, it maps the + // pages of .rdata as read/write so that it can set each __ref_* variable + // to point to the original variable in the base image. Afterward, pages in + // .rdata are remapped as read-only. This protects the __ref_* variables from + // being overwritten during execution. + RefGV->setSection(".rdata"); + // Create debug info for the replacement global variable. DataLayout Layout = M->getDataLayout(); DIType *DebugType = DebugInfo.createPointerType( |