From 1aa98f4294861f3021f52c00ca4cc57403410de9 Mon Sep 17 00:00:00 2001 From: Vitaly Buka Date: Sat, 24 Feb 2018 06:58:56 +0000 Subject: [PATCH] [cfi] Lazy initialization of CFI interceptors Summary: Interceptors initialization may need to allocate memory. So if we initialize too early we can crash in non initialized allocator. Reviewers: pcc, eugenis Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D43669 llvm-svn: 326025 --- compiler-rt/lib/cfi/cfi.cc | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/compiler-rt/lib/cfi/cfi.cc b/compiler-rt/lib/cfi/cfi.cc index f7693b3..52f504b 100644 --- a/compiler-rt/lib/cfi/cfi.cc +++ b/compiler-rt/lib/cfi/cfi.cc @@ -379,6 +379,8 @@ __cfi_slowpath_diag(u64 CallSiteTypeId, void *Ptr, void *DiagData) { } #endif +static void EnsureInterceptorsInitialized(); + // Setup shadow for dlopen()ed libraries. // The actual shadow setup happens after dlopen() returns, which means that // a library can not be a target of any CFI checks while its constructors are @@ -388,6 +390,7 @@ __cfi_slowpath_diag(u64 CallSiteTypeId, void *Ptr, void *DiagData) { // We could insert a high-priority constructor into the library, but that would // not help with the uninstrumented libraries. INTERCEPTOR(void*, dlopen, const char *filename, int flag) { + EnsureInterceptorsInitialized(); EnterLoader(); void *handle = REAL(dlopen)(filename, flag); ExitLoader(); @@ -395,12 +398,27 @@ INTERCEPTOR(void*, dlopen, const char *filename, int flag) { } INTERCEPTOR(int, dlclose, void *handle) { + EnsureInterceptorsInitialized(); EnterLoader(); int res = REAL(dlclose)(handle); ExitLoader(); return res; } +static BlockingMutex interceptor_init_lock(LINKER_INITIALIZED); +static bool interceptors_inited = false; + +static void EnsureInterceptorsInitialized() { + BlockingMutexLock lock(&interceptor_init_lock); + if (interceptors_inited) + return; + + INTERCEPT_FUNCTION(dlopen); + INTERCEPT_FUNCTION(dlclose); + + interceptors_inited = true; +} + extern "C" SANITIZER_INTERFACE_ATTRIBUTE #if !SANITIZER_CAN_USE_PREINIT_ARRAY // On ELF platforms, the constructor is invoked using .preinit_array (see below) @@ -411,9 +429,6 @@ void __cfi_init() { InitializeFlags(); InitShadow(); - INTERCEPT_FUNCTION(dlopen); - INTERCEPT_FUNCTION(dlclose); - #ifdef CFI_ENABLE_DIAG __ubsan::InitAsPlugin(); #endif -- 2.7.4