From 001a12ed59c354aa759ff3e104748c36803cfaa2 Mon Sep 17 00:00:00 2001
From: Siva Chandra Reddy <sivachandra@google.com>
Date: Mon, 8 Mar 2021 15:12:22 -0800
Subject: [PATCH] [libc][NFC] Make x86_64 fenv functions msan safe.

These functions used inline asm to read FPU state. This change adds
explicit unpoisoning in these functions as the sanitizers don't see the
read operations.
---
 libc/src/__support/CMakeLists.txt | 1 +
 libc/utils/FPUtil/CMakeLists.txt  | 1 +
 libc/utils/FPUtil/x86_64/FEnv.h   | 6 ++++++
 3 files changed, 8 insertions(+)

diff --git a/libc/src/__support/CMakeLists.txt b/libc/src/__support/CMakeLists.txt
index 980b510..32f538e 100644
--- a/libc/src/__support/CMakeLists.txt
+++ b/libc/src/__support/CMakeLists.txt
@@ -2,4 +2,5 @@ add_header_library(
   common
   HDRS
     common.h
+    sanitizer_annotations.h
 )
diff --git a/libc/utils/FPUtil/CMakeLists.txt b/libc/utils/FPUtil/CMakeLists.txt
index 2c1c166..43ee643 100644
--- a/libc/utils/FPUtil/CMakeLists.txt
+++ b/libc/utils/FPUtil/CMakeLists.txt
@@ -31,6 +31,7 @@ add_header_library(
     libc.include.math
     libc.include.errno
     libc.include.fenv
+    libc.src.__support.common
     libc.utils.CPP.standalone_cpp
 )
 
diff --git a/libc/utils/FPUtil/x86_64/FEnv.h b/libc/utils/FPUtil/x86_64/FEnv.h
index 3fb4881..1196aba 100644
--- a/libc/utils/FPUtil/x86_64/FEnv.h
+++ b/libc/utils/FPUtil/x86_64/FEnv.h
@@ -12,6 +12,8 @@
 #include <fenv.h>
 #include <stdint.h>
 
+#include "src/__support/sanitizer_annotations.h"
+
 namespace __llvm_libc {
 namespace fputil {
 
@@ -95,6 +97,7 @@ static_assert(
 static inline uint16_t getX87ControlWord() {
   uint16_t w;
   __asm__ __volatile__("fnstcw %0" : "=m"(w)::);
+  SANITIZER_MEMORY_INITIALIZED(&w, sizeof(w));
   return w;
 }
 
@@ -105,6 +108,7 @@ static inline void writeX87ControlWord(uint16_t w) {
 static inline uint16_t getX87StatusWord() {
   uint16_t w;
   __asm__ __volatile__("fnstsw %0" : "=m"(w)::);
+  SANITIZER_MEMORY_INITIALIZED(&w, sizeof(w));
   return w;
 }
 
@@ -115,6 +119,7 @@ static inline void clearX87Exceptions() {
 static inline uint32_t getMXCSR() {
   uint32_t w;
   __asm__ __volatile__("stmxcsr %0" : "=m"(w)::);
+  SANITIZER_MEMORY_INITIALIZED(&w, sizeof(w));
   return w;
 }
 
@@ -124,6 +129,7 @@ static inline void writeMXCSR(uint32_t w) {
 
 static inline void getX87StateDescriptor(X87StateDescriptor &s) {
   __asm__ __volatile__("fnstenv %0" : "=m"(s));
+  SANITIZER_MEMORY_INITIALIZED(&s, sizeof(s));
 }
 
 static inline void writeX87StateDescriptor(const X87StateDescriptor &s) {
-- 
2.7.4