[asan] Use dynamic shadow on 32-bit Android.

Summary:
The following kernel change has moved ET_DYN base to 0x4000000 on arm32:
https://marc.info/?l=linux-kernel&m=149825162606848&w=2

Switch to dynamic shadow base to avoid such conflicts in the future.

Reserve shadow memory in an ifunc resolver, but don't use it in the instrumentation
until PR35221 is fixed. This will eventually let use save one load per function.

Reviewers: kcc

Subscribers: aemerson, srhines, kubamracek, kristof.beyls, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D39393

llvm-svn: 317943

1 files changed, 12 insertions, 6 deletions

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
index ea1e79556ab..6274b248edb 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
@@ -954,7 +954,7 @@ static uptr GetKernelAreaSize() {
 }
 #endif  // SANITIZER_WORDSIZE == 32
 
-uptr GetMaxUserVirtualAddress() {
+uptr GetMaxVirtualAddress() {
 #if SANITIZER_NETBSD && defined(__x86_64__)
   return 0x7f7ffffff000ULL;  // (0x00007f8000000000 - PAGE_SIZE)
 #elif SANITIZER_WORDSIZE == 64
@@ -978,15 +978,21 @@ uptr GetMaxUserVirtualAddress() {
 # if defined(__s390__)
   return (1ULL << 31) - 1;  // 0x7fffffff;
 # else
-  uptr res = (1ULL << 32) - 1;  // 0xffffffff;
-  if (!common_flags()->full_address_space)
-    res -= GetKernelAreaSize();
-  CHECK_LT(reinterpret_cast<uptr>(&res), res);
-  return res;
+  return (1ULL << 32) - 1;  // 0xffffffff;
 # endif
 #endif  // SANITIZER_WORDSIZE
 }
 
+uptr GetMaxUserVirtualAddress() {
+  uptr addr = GetMaxVirtualAddress();
+#if SANITIZER_WORDSIZE == 32 && !defined(__s390__)
+  if (!common_flags()->full_address_space)
+    addr -= GetKernelAreaSize();
+  CHECK_LT(reinterpret_cast<uptr>(&addr), addr);
+#endif
+  return addr;
+}
+
 uptr GetPageSize() {
 // Android post-M sysconf(_SC_PAGESIZE) crashes if called from .preinit_array.
 #if SANITIZER_ANDROID