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authorDimitry Andric <dim@FreeBSD.org>2015-09-06 18:41:23 +0000
committerDimitry Andric <dim@FreeBSD.org>2015-09-06 18:41:23 +0000
commitf31bcc68c72371a2bf63aead9f3373a1ff2053b6 (patch)
treeb259e5d585da0f8cde9579939a74d5ef44c72abd /lib/safestack
parentcd2dd3df15523e2be8d2bbace27641d6ac9fa40d (diff)
downloadsrc-f31bcc68c72371a2bf63aead9f3373a1ff2053b6.tar.gz
src-f31bcc68c72371a2bf63aead9f3373a1ff2053b6.zip
Import compiler-rt 3.7.0 release (r246257).vendor/compiler-rt/compiler-rt-release_370-r246257
Notes
Notes: svn path=/vendor/compiler-rt/dist/; revision=287516 svn path=/vendor/compiler-rt/compiler-rt-release_370-r246257/; revision=287517; tag=vendor/compiler-rt/compiler-rt-release_370-r246257
Diffstat (limited to 'lib/safestack')
-rw-r--r--lib/safestack/CMakeLists.txt28
-rw-r--r--lib/safestack/safestack.cc246
2 files changed, 274 insertions, 0 deletions
diff --git a/lib/safestack/CMakeLists.txt b/lib/safestack/CMakeLists.txt
new file mode 100644
index 000000000000..1c15d079dbb5
--- /dev/null
+++ b/lib/safestack/CMakeLists.txt
@@ -0,0 +1,28 @@
+add_custom_target(safestack)
+
+set(SAFESTACK_SOURCES safestack.cc)
+
+include_directories(..)
+
+set(SAFESTACK_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+
+if(APPLE)
+ # Build universal binary on APPLE.
+ add_compiler_rt_osx_static_runtime(clang_rt.safestack_osx
+ ARCH ${SAFESTACK_SUPPORTED_ARCH}
+ SOURCES ${SAFESTACK_SOURCES}
+ $<TARGET_OBJECTS:RTInterception.osx>
+ $<TARGET_OBJECTS:RTSanitizerCommon.osx>
+ CFLAGS ${SAFESTACK_CFLAGS})
+ add_dependencies(safestack clang_rt.safestack_osx)
+else()
+ # Otherwise, build separate libraries for each target.
+ foreach(arch ${SAFESTACK_SUPPORTED_ARCH})
+ add_compiler_rt_runtime(clang_rt.safestack-${arch} ${arch} STATIC
+ SOURCES ${SAFESTACK_SOURCES}
+ $<TARGET_OBJECTS:RTInterception.${arch}>
+ $<TARGET_OBJECTS:RTSanitizerCommon.${arch}>
+ CFLAGS ${SAFESTACK_CFLAGS})
+ add_dependencies(safestack clang_rt.safestack-${arch})
+ endforeach()
+endif()
diff --git a/lib/safestack/safestack.cc b/lib/safestack/safestack.cc
new file mode 100644
index 000000000000..504bd3cd0d99
--- /dev/null
+++ b/lib/safestack/safestack.cc
@@ -0,0 +1,246 @@
+//===-- safestack.cc ------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the runtime support for the safe stack protection
+// mechanism. The runtime manages allocation/deallocation of the unsafe stack
+// for the main thread, as well as all pthreads that are created/destroyed
+// during program execution.
+//
+//===----------------------------------------------------------------------===//
+
+#include <limits.h>
+#include <pthread.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <sys/resource.h>
+#include <sys/types.h>
+#include <sys/user.h>
+
+#include "interception/interception.h"
+#include "sanitizer_common/sanitizer_common.h"
+
+// TODO: The runtime library does not currently protect the safe stack beyond
+// relying on the system-enforced ASLR. The protection of the (safe) stack can
+// be provided by three alternative features:
+//
+// 1) Protection via hardware segmentation on x86-32 and some x86-64
+// architectures: the (safe) stack segment (implicitly accessed via the %ss
+// segment register) can be separated from the data segment (implicitly
+// accessed via the %ds segment register). Dereferencing a pointer to the safe
+// segment would result in a segmentation fault.
+//
+// 2) Protection via software fault isolation: memory writes that are not meant
+// to access the safe stack can be prevented from doing so through runtime
+// instrumentation. One way to do it is to allocate the safe stack(s) in the
+// upper half of the userspace and bitmask the corresponding upper bit of the
+// memory addresses of memory writes that are not meant to access the safe
+// stack.
+//
+// 3) Protection via information hiding on 64 bit architectures: the location
+// of the safe stack(s) can be randomized through secure mechanisms, and the
+// leakage of the stack pointer can be prevented. Currently, libc can leak the
+// stack pointer in several ways (e.g. in longjmp, signal handling, user-level
+// context switching related functions, etc.). These can be fixed in libc and
+// in other low-level libraries, by either eliminating the escaping/dumping of
+// the stack pointer (i.e., %rsp) when that's possible, or by using
+// encryption/PTR_MANGLE (XOR-ing the dumped stack pointer with another secret
+// we control and protect better, as is already done for setjmp in glibc.)
+// Furthermore, a static machine code level verifier can be ran after code
+// generation to make sure that the stack pointer is never written to memory,
+// or if it is, its written on the safe stack.
+//
+// Finally, while the Unsafe Stack pointer is currently stored in a thread
+// local variable, with libc support it could be stored in the TCB (thread
+// control block) as well, eliminating another level of indirection and making
+// such accesses faster. Alternatively, dedicating a separate register for
+// storing it would also be possible.
+
+/// Minimum stack alignment for the unsafe stack.
+const unsigned kStackAlign = 16;
+
+/// Default size of the unsafe stack. This value is only used if the stack
+/// size rlimit is set to infinity.
+const unsigned kDefaultUnsafeStackSize = 0x2800000;
+
+// TODO: To make accessing the unsafe stack pointer faster, we plan to
+// eventually store it directly in the thread control block data structure on
+// platforms where this structure is pointed to by %fs or %gs. This is exactly
+// the same mechanism as currently being used by the traditional stack
+// protector pass to store the stack guard (see getStackCookieLocation()
+// function above). Doing so requires changing the tcbhead_t struct in glibc
+// on Linux and tcb struct in libc on FreeBSD.
+//
+// For now, store it in a thread-local variable.
+extern "C" {
+__attribute__((visibility(
+ "default"))) __thread void *__safestack_unsafe_stack_ptr = nullptr;
+}
+
+// Per-thread unsafe stack information. It's not frequently accessed, so there
+// it can be kept out of the tcb in normal thread-local variables.
+static __thread void *unsafe_stack_start = nullptr;
+static __thread size_t unsafe_stack_size = 0;
+static __thread size_t unsafe_stack_guard = 0;
+
+static inline void *unsafe_stack_alloc(size_t size, size_t guard) {
+ CHECK_GE(size + guard, size);
+ void *addr = MmapOrDie(size + guard, "unsafe_stack_alloc");
+ MprotectNoAccess((uptr)addr, (uptr)guard);
+ return (char *)addr + guard;
+}
+
+static inline void unsafe_stack_setup(void *start, size_t size, size_t guard) {
+ CHECK_GE((char *)start + size, (char *)start);
+ CHECK_GE((char *)start + guard, (char *)start);
+ void *stack_ptr = (char *)start + size;
+ CHECK_EQ((((size_t)stack_ptr) & (kStackAlign - 1)), 0);
+
+ __safestack_unsafe_stack_ptr = stack_ptr;
+ unsafe_stack_start = start;
+ unsafe_stack_size = size;
+ unsafe_stack_guard = guard;
+}
+
+static void unsafe_stack_free() {
+ if (unsafe_stack_start) {
+ UnmapOrDie((char *)unsafe_stack_start - unsafe_stack_guard,
+ unsafe_stack_size + unsafe_stack_guard);
+ }
+ unsafe_stack_start = nullptr;
+}
+
+/// Thread data for the cleanup handler
+static pthread_key_t thread_cleanup_key;
+
+/// Safe stack per-thread information passed to the thread_start function
+struct tinfo {
+ void *(*start_routine)(void *);
+ void *start_routine_arg;
+
+ void *unsafe_stack_start;
+ size_t unsafe_stack_size;
+ size_t unsafe_stack_guard;
+};
+
+/// Wrap the thread function in order to deallocate the unsafe stack when the
+/// thread terminates by returning from its main function.
+static void *thread_start(void *arg) {
+ struct tinfo *tinfo = (struct tinfo *)arg;
+
+ void *(*start_routine)(void *) = tinfo->start_routine;
+ void *start_routine_arg = tinfo->start_routine_arg;
+
+ // Setup the unsafe stack; this will destroy tinfo content
+ unsafe_stack_setup(tinfo->unsafe_stack_start, tinfo->unsafe_stack_size,
+ tinfo->unsafe_stack_guard);
+
+ // Make sure out thread-specific destructor will be called
+ // FIXME: we can do this only any other specific key is set by
+ // intercepting the pthread_setspecific function itself
+ pthread_setspecific(thread_cleanup_key, (void *)1);
+
+ return start_routine(start_routine_arg);
+}
+
+/// Thread-specific data destructor
+static void thread_cleanup_handler(void *_iter) {
+ // We want to free the unsafe stack only after all other destructors
+ // have already run. We force this function to be called multiple times.
+ // User destructors that might run more then PTHREAD_DESTRUCTOR_ITERATIONS-1
+ // times might still end up executing after the unsafe stack is deallocated.
+ size_t iter = (size_t)_iter;
+ if (iter < PTHREAD_DESTRUCTOR_ITERATIONS) {
+ pthread_setspecific(thread_cleanup_key, (void *)(iter + 1));
+ } else {
+ // This is the last iteration
+ unsafe_stack_free();
+ }
+}
+
+/// Intercept thread creation operation to allocate and setup the unsafe stack
+INTERCEPTOR(int, pthread_create, pthread_t *thread,
+ const pthread_attr_t *attr,
+ void *(*start_routine)(void*), void *arg) {
+
+ size_t size = 0;
+ size_t guard = 0;
+
+ if (attr != NULL) {
+ pthread_attr_getstacksize(attr, &size);
+ pthread_attr_getguardsize(attr, &guard);
+ } else {
+ // get pthread default stack size
+ pthread_attr_t tmpattr;
+ pthread_attr_init(&tmpattr);
+ pthread_attr_getstacksize(&tmpattr, &size);
+ pthread_attr_getguardsize(&tmpattr, &guard);
+ pthread_attr_destroy(&tmpattr);
+ }
+
+ CHECK_NE(size, 0);
+ CHECK_EQ((size & (kStackAlign - 1)), 0);
+ CHECK_EQ((guard & (PAGE_SIZE - 1)), 0);
+
+ void *addr = unsafe_stack_alloc(size, guard);
+ struct tinfo *tinfo =
+ (struct tinfo *)(((char *)addr) + size - sizeof(struct tinfo));
+ tinfo->start_routine = start_routine;
+ tinfo->start_routine_arg = arg;
+ tinfo->unsafe_stack_start = addr;
+ tinfo->unsafe_stack_size = size;
+ tinfo->unsafe_stack_guard = guard;
+
+ return REAL(pthread_create)(thread, attr, thread_start, tinfo);
+}
+
+extern "C" __attribute__((visibility("default")))
+#if !SANITIZER_CAN_USE_PREINIT_ARRAY
+// On ELF platforms, the constructor is invoked using .preinit_array (see below)
+__attribute__((constructor(0)))
+#endif
+void __safestack_init() {
+ // Determine the stack size for the main thread.
+ size_t size = kDefaultUnsafeStackSize;
+ size_t guard = 4096;
+
+ struct rlimit limit;
+ if (getrlimit(RLIMIT_STACK, &limit) == 0 && limit.rlim_cur != RLIM_INFINITY)
+ size = limit.rlim_cur;
+
+ // Allocate unsafe stack for main thread
+ void *addr = unsafe_stack_alloc(size, guard);
+
+ unsafe_stack_setup(addr, size, guard);
+
+ // Initialize pthread interceptors for thread allocation
+ INTERCEPT_FUNCTION(pthread_create);
+
+ // Setup the cleanup handler
+ pthread_key_create(&thread_cleanup_key, thread_cleanup_handler);
+}
+
+#if SANITIZER_CAN_USE_PREINIT_ARRAY
+// On ELF platforms, run safestack initialization before any other constructors.
+// On other platforms we use the constructor attribute to arrange to run our
+// initialization early.
+extern "C" {
+__attribute__((section(".preinit_array"),
+ used)) void (*__safestack_preinit)(void) = __safestack_init;
+}
+#endif
+
+extern "C"
+ __attribute__((visibility("default"))) void *__get_unsafe_stack_start() {
+ return unsafe_stack_start;
+}
+
+extern "C"
+ __attribute__((visibility("default"))) void *__get_unsafe_stack_ptr() {
+ return __safestack_unsafe_stack_ptr;
+}