From 1a4fc2413fbe789f4b5bbff50c1fcc234fb304ee Mon Sep 17 00:00:00 2001
From: Julian Lettner <jlettner@apple.com>
Date: Tue, 9 Jul 2019 18:42:01 +0000
Subject: Revert "[TSan] Improve handling of stack pointer mangling in
 {set,long}jmp, pt.8"

This reverts commit 521f77e6351fd921f5a81027c7c72addca378989.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@365534 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/tsan/rtl/tsan_platform_linux.cc | 50 ++++---------------------------------
 lib/tsan/rtl/tsan_platform_mac.cc   | 11 ++++----
 2 files changed, 10 insertions(+), 51 deletions(-)

diff --git a/lib/tsan/rtl/tsan_platform_linux.cc b/lib/tsan/rtl/tsan_platform_linux.cc
index 1373037ed..71f6f4872 100644
--- a/lib/tsan/rtl/tsan_platform_linux.cc
+++ b/lib/tsan/rtl/tsan_platform_linux.cc
@@ -68,17 +68,12 @@ void *__libc_stack_end = 0;
 #endif
 
 #if SANITIZER_LINUX && defined(__aarch64__)
-__tsan::uptr InitializeGuardPtr() __attribute__((visibility("hidden")));
+void InitializeGuardPtr() __attribute__((visibility("hidden")));
 extern "C" __tsan::uptr _tsan_pointer_chk_guard;
 #endif
 
 namespace __tsan {
 
-#if SANITIZER_LINUX && defined(__aarch64__)
-static void InitializeLongjmpXorKey();
-static uptr longjmp_xor_key;
-#endif
-
 #ifdef TSAN_RUNTIME_VMA
 // Runtime detected VMA size.
 uptr vmaSize;
@@ -290,25 +285,7 @@ void InitializePlatform() {
       reexec = true;
     }
     // Initialize the guard pointer used in {sig}{set,long}jump.
-    longjmp_xor_key = InitializeGuardPtr();
-    uptr old_value = longjmp_xor_key;
-    InitializeLongjmpXorKey();
-    CHECK_EQ(longjmp_xor_key, old_value);
-    // If the above check fails for you, please contact me (jlettner@apple.com)
-    // and let me know the values of the two differing keys.  Please also set a
-    // breakpoint on `InitializeGuardPtr` and `InitializeLongjmpXorKey` and tell
-    // me the stack pointer (SP) values that go into the XOR operation (where we
-    // derive the key):
-    //
-    //   InitializeLongjmpXorKey:
-    //     uptr sp = (uptr)__builtin_frame_address(0);
-    //
-    //   InitializeGuardPtr (in tsan_rtl_aarch64.S):
-    //       mov  x0, sp
-    //       ...
-    //       eor  x0, x0, x1
-    //
-    // Then feel free to comment out the call to `InitializeLongjmpXorKey`.
+    InitializeGuardPtr();
 #endif
     if (reexec)
       ReExec();
@@ -376,7 +353,9 @@ static uptr UnmangleLongJmpSp(uptr mangled_sp) {
 # endif
 #elif defined(__aarch64__)
 # if SANITIZER_LINUX
-  return mangled_sp ^ longjmp_xor_key;
+  // TODO(yln): fix this
+  // return mangled_sp ^ _tsan_pointer_chk_guard;
+  return mangled_sp;
 # else
   return mangled_sp;
 # endif
@@ -415,25 +394,6 @@ uptr ExtractLongJmpSp(uptr *env) {
   return UnmangleLongJmpSp(mangled_sp);
 }
 
-#if SANITIZER_LINUX && defined(__aarch64__)
-// GLIBC mangles the function pointers in jmp_buf (used in {set,long}*jmp
-// functions) by XORing them with a random key.  For AArch64 it is a global
-// variable rather than a TCB one (as for x86_64/powerpc).  We obtain the key by
-// issuing a setjmp and XORing the SP pointer values to derive the key.
-static void InitializeLongjmpXorKey() {
-  // 1. Call REAL(setjmp), which stores the mangled SP in env.
-  jump_buf env;
-  REAL(setjmp)(env);
-
-  // 2. Retrieve mangled/vanilla SP.
-  uptr mangled_sp = ((uptr *)&env)[LONG_JMP_SP_ENV_SLOT];
-  uptr sp = (uptr)__builtin_frame_address(0);
-
-  // 3. xor SPs to obtain key.
-  longjmp_xor_key = mangled_sp ^ sp;
-}
-#endif
-
 void ImitateTlsWrite(ThreadState *thr, uptr tls_addr, uptr tls_size) {
   // Check that the thr object is in tls;
   const uptr thr_beg = (uptr)thr;
diff --git a/lib/tsan/rtl/tsan_platform_mac.cc b/lib/tsan/rtl/tsan_platform_mac.cc
index 0c2d2aa93..e43a9ec34 100644
--- a/lib/tsan/rtl/tsan_platform_mac.cc
+++ b/lib/tsan/rtl/tsan_platform_mac.cc
@@ -238,7 +238,8 @@ void InitializePlatformEarly() {
 #endif
 }
 
-static uptr longjmp_xor_key = 0;
+static const uptr kPthreadSetjmpXorKeySlot = 0x7;
+extern "C" uptr __tsan_darwin_setjmp_xor_key = 0;
 
 void InitializePlatform() {
   DisableCoreDumperIfNecessary();
@@ -253,9 +254,8 @@ void InitializePlatform() {
 #endif
 
   if (GetMacosVersion() >= MACOS_VERSION_MOJAVE) {
-    // Libsystem currently uses a process-global key; this might change.
-    const unsigned kTLSLongjmpXorKeySlot = 0x7;
-    longjmp_xor_key = (uptr)pthread_getspecific(kTLSLongjmpXorKeySlot);
+    __tsan_darwin_setjmp_xor_key =
+        (uptr)pthread_getspecific(kPthreadSetjmpXorKeySlot);
   }
 }
 
@@ -268,8 +268,7 @@ void InitializePlatform() {
 
 uptr ExtractLongJmpSp(uptr *env) {
   uptr mangled_sp = env[LONG_JMP_SP_ENV_SLOT];
-  uptr sp = mangled_sp ^ longjmp_xor_key;
-  return sp;
+  return mangled_sp ^ __tsan_darwin_setjmp_xor_key;
 }
 
 #if !SANITIZER_GO
-- 
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