Merge "Runtime support for CFI"

libc/include/dlfcn.h

@@ -29,6 +29,7 @@
 #ifndef __DLFCN_H__
 #define __DLFCN_H__
 
+#include <stdint.h>
 #include <sys/cdefs.h>
 
 __BEGIN_DECLS

libc/private/CFIShadow.h

@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef CFI_SHADOW_H
+#define CFI_SHADOW_H
+
+#include <stdint.h>
+
+#include "private/bionic_page.h"
+#include "private/bionic_macros.h"
+
+constexpr unsigned kLibraryAlignmentBits = 18;
+constexpr size_t kLibraryAlignment = 1UL << kLibraryAlignmentBits;
+
+// This class defines format of the shadow region for Control Flow Integrity support.
+// See documentation in http://clang.llvm.org/docs/ControlFlowIntegrityDesign.html#shared-library-support.
+//
+// CFI shadow is effectively a very fast and specialized implementation of dladdr: given an address that
+// belongs to a shared library or an executable, it can find the address of a specific export in that
+// library (a function called "__cfi_check"). This is only guaranteed to work for
+// addresses of possible CFI targets inside a library: indirectly called functions and virtual
+// tables. A random address inside a library may not work in the future (but it does in the current
+// implementation).
+//
+// Implementation is a sparse array of uint16_t where each element describes the location of
+// __cfi_check for a 2**kShadowGranularity range of memory. Array elements (called "shadow values"
+// below) are interpreted as follows.
+//
+// For an address P and corresponding shadow value V, the address of __cfi_check is calculated as
+//   align_up(P, 2**kShadowGranularity) - (V - 2) * (2 ** kCfiCheckGranularity)
+//
+// Special shadow values:
+//        0 = kInvalidShadow, this memory range has no valid CFI targets.
+//        1 = kUncheckedShadow, any address is this memory range is a valid CFI target
+//
+// Loader requirement: each aligned 2**kShadowGranularity region of address space may contain at
+// most one DSO.
+// Compiler requirement: __cfi_check is aligned at kCfiCheckGranularity.
+// Compiler requirement: __cfi_check for a given DSO is located below any CFI target for that DSO.
+class CFIShadow {
+ public:
+  static constexpr uintptr_t kShadowGranularity = kLibraryAlignmentBits;
+  static constexpr uintptr_t kCfiCheckGranularity = 12;
+
+  // Each uint16_t element of the shadow corresponds to this much application memory.
+  static constexpr uintptr_t kShadowAlign = 1UL << kShadowGranularity;
+
+  // Alignment of __cfi_check.
+  static constexpr uintptr_t kCfiCheckAlign = 1UL << kCfiCheckGranularity;  // 4K
+
+#if defined(__aarch64__)
+  static constexpr uintptr_t kMaxTargetAddr = 0x7fffffffff;
+#elif defined (__LP64__)
+  static constexpr uintptr_t kMaxTargetAddr = 0x7fffffffffff;
+#else
+  static constexpr uintptr_t kMaxTargetAddr = 0xffffffff;
+#endif
+
+  // Shadow is 2 -> 2**kShadowGranularity.
+  static constexpr uintptr_t kShadowSize =
+      align_up((kMaxTargetAddr >> (kShadowGranularity - 1)), PAGE_SIZE);
+
+  // Returns offset inside the shadow region for an address.
+  static constexpr uintptr_t MemToShadowOffset(uintptr_t x) {
+    return (x >> kShadowGranularity) << 1;
+  }
+
+  typedef int (*CFICheckFn)(uint64_t, void *, void *);
+
+ public:
+  enum ShadowValues : uint16_t {
+    kInvalidShadow = 0,    // Not a valid CFI target.
+    kUncheckedShadow = 1,  // Unchecked, valid CFI target.
+    kRegularShadowMin = 2  // This and all higher values encode a negative offset to __cfi_check in
+                           // the units of kCfiCheckGranularity, starting with 0 at
+                           // kRegularShadowMin.
+  };
+};
+
+#endif  // CFI_SHADOW_H

libc/private/bionic_macros.h

@@ -48,11 +48,11 @@
     ? (1UL << (64 - __builtin_clzl(static_cast<unsigned long>(value)))) \
     : (1UL << (32 - __builtin_clz(static_cast<unsigned int>(value)))))
 
-static inline uintptr_t align_down(uintptr_t p, size_t align) {
+static constexpr uintptr_t align_down(uintptr_t p, size_t align) {
   return p & ~(align - 1);
 }
 
-static inline uintptr_t align_up(uintptr_t p, size_t align) {
+static constexpr uintptr_t align_up(uintptr_t p, size_t align) {
   return (p + align - 1) & ~(align - 1);
 }
 

libdl/Android.bp

@@ -44,7 +44,7 @@ cc_library {
             version_script: "libdl.x86_64.map",
         },
     },
-    srcs: ["libdl.c"],
+    srcs: ["libdl.c", "libdl_cfi.cpp"],
     cflags: [
         "-Wall",
         "-Wextra",
@@ -61,6 +61,9 @@ cc_library {
     allow_undefined_symbols: true,
     system_shared_libs: [],
 
+    // For private/CFIShadow.h.
+    include_dirs: ["bionic/libc"],
+
     // This is placeholder library the actual implementation is (currently)
     // provided by the linker.
     shared_libs: [ "ld-android" ],

libdl/libdl.arm.map

@@ -36,6 +36,9 @@ LIBC_N {
 
 LIBC_PLATFORM {
   global:
+    __cfi_init;
+    __cfi_slowpath;
+    __cfi_slowpath_diag;
     android_dlwarning;
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;

libdl/libdl.arm64.map

@@ -35,6 +35,9 @@ LIBC_N {
 
 LIBC_PLATFORM {
   global:
+    __cfi_init;
+    __cfi_slowpath;
+    __cfi_slowpath_diag;
     android_dlwarning;
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;

libdl/libdl.map.txt

@@ -35,6 +35,9 @@ LIBC_N {
 
 LIBC_PLATFORM {
   global:
+    __cfi_init;
+    __cfi_slowpath;
+    __cfi_slowpath_diag;
     android_dlwarning;
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;

libdl/libdl.mips.map

@@ -35,6 +35,9 @@ LIBC_N {
 
 LIBC_PLATFORM {
   global:
+    __cfi_init;
+    __cfi_slowpath;
+    __cfi_slowpath_diag;
     android_dlwarning;
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;

libdl/libdl.mips64.map

@@ -35,6 +35,9 @@ LIBC_N {
 
 LIBC_PLATFORM {
   global:
+    __cfi_init;
+    __cfi_slowpath;
+    __cfi_slowpath_diag;
     android_dlwarning;
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;

libdl/libdl.x86.map

@@ -35,6 +35,9 @@ LIBC_N {
 
 LIBC_PLATFORM {
   global:
+    __cfi_init;
+    __cfi_slowpath;
+    __cfi_slowpath_diag;
     android_dlwarning;
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;

libdl/libdl.x86_64.map

@@ -35,6 +35,9 @@ LIBC_N {
 
 LIBC_PLATFORM {
   global:
+    __cfi_init;
+    __cfi_slowpath;
+    __cfi_slowpath_diag;
     android_dlwarning;
     android_get_application_target_sdk_version;
     android_set_application_target_sdk_version;

libdl/libdl_cfi.cpp

@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <sys/mman.h>
+
+#include "private/CFIShadow.h"
+
+__attribute__((__weak__, visibility("default"))) extern "C" void __loader_cfi_fail(
+    uint64_t CallSiteTypeId, void* Ptr, void* DiagData, void* CallerPc);
+
+// Base address of the CFI shadow. Passed down from the linker in __cfi_init()
+// and does not change after that. The contents of the shadow change in
+// dlopen/dlclose.
+static struct {
+  uintptr_t v;
+  char padding[PAGE_SIZE - sizeof(v)];
+} shadow_base_storage alignas(PAGE_SIZE);
+
+extern "C" uintptr_t* __cfi_init(uintptr_t shadow_base) {
+  shadow_base_storage.v = shadow_base;
+  static_assert(sizeof(shadow_base_storage) == PAGE_SIZE, "");
+  mprotect(&shadow_base_storage, PAGE_SIZE, PROT_READ);
+  return &shadow_base_storage.v;
+}
+
+static uint16_t shadow_load(void* p) {
+  uintptr_t addr = reinterpret_cast<uintptr_t>(p);
+  uintptr_t ofs = CFIShadow::MemToShadowOffset(addr);
+  if (ofs > CFIShadow::kShadowSize) return CFIShadow::kInvalidShadow;
+  return *reinterpret_cast<uint16_t*>(shadow_base_storage.v + ofs);
+}
+
+static uintptr_t cfi_check_addr(uint16_t v, void* Ptr) {
+  uintptr_t addr = reinterpret_cast<uintptr_t>(Ptr);
+  uintptr_t aligned_addr = align_up(addr, CFIShadow::kShadowAlign);
+  uintptr_t p = aligned_addr - (static_cast<uintptr_t>(v - CFIShadow::kRegularShadowMin)
+                                << CFIShadow::kCfiCheckGranularity);
+#ifdef __arm__
+  // Assume Thumb encoding. FIXME: force thumb at compile time?
+  p++;
+#endif
+  return p;
+}
+
+static inline void cfi_slowpath_common(uint64_t CallSiteTypeId, void* Ptr, void* DiagData) {
+  uint16_t v = shadow_load(Ptr);
+  switch (v) {
+    case CFIShadow::kInvalidShadow:
+      __loader_cfi_fail(CallSiteTypeId, Ptr, DiagData, __builtin_return_address(0));
+      break;
+    case CFIShadow::kUncheckedShadow:
+      break;
+    default:
+      reinterpret_cast<CFIShadow::CFICheckFn>(cfi_check_addr(v, Ptr))(CallSiteTypeId, Ptr, DiagData);
+  }
+}
+
+extern "C" void __cfi_slowpath(uint64_t CallSiteTypeId, void* Ptr) {
+  cfi_slowpath_common(CallSiteTypeId, Ptr, nullptr);
+}
+
+extern "C" void __cfi_slowpath_diag(uint64_t CallSiteTypeId, void* Ptr, void* DiagData) {
+  cfi_slowpath_common(CallSiteTypeId, Ptr, DiagData);
+}

linker/Android.bp

@@ -18,6 +18,7 @@ cc_binary {
         "linker.cpp",
         "linker_block_allocator.cpp",
         "linker_dlwarning.cpp",
+        "linker_cfi.cpp",
         "linker_gdb_support.cpp",
         "linker_globals.cpp",
         "linker_libc_support.c",

linker/dlfcn.cpp

@@ -15,6 +15,7 @@
  */
 
 #include "linker.h"
+#include "linker_cfi.h"
 #include "linker_globals.h"
 #include "linker_dlwarning.h"
 
@@ -189,6 +190,10 @@ android_namespace_t* __android_create_namespace(const char* name,
   return result;
 }
 
+void __cfi_fail(uint64_t CallSiteTypeId, void* Ptr, void *DiagData, void *CallerPc) {
+  CFIShadowWriter::CfiFail(CallSiteTypeId, Ptr, DiagData, CallerPc);
+}
+
 // name_offset: starting index of the name in libdl_info.strtab
 #define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \
     { name_offset, \
@@ -225,11 +230,11 @@ static const char ANDROID_LIBDL_STRTAB[] =
   // 012345678901234 567890123456789012345678901234567 8901234567890123456789012345678901 2345678901234567 89
     "et_sdk_version\0__loader_android_init_namespaces\0__loader_android_create_namespace\0__loader_dlvsym\0__"
   // 4*
-  // 0000000000111111111122222 2222233333333334444444 4445555555555666666666677777777778 8888888889999999 999
-  // 0123456789012345678901234 5678901234567890123456 7890123456789012345678901234567890 1234567890123456 789
-    "loader_android_dlwarning\0"
+  // 0000000000111111111122222 222223333333333444 4444444555555555566666666667777 77777788888888889999999999
+  // 0123456789012345678901234 567890123456789012 3456789012345678901234567890123 45678901234567890123456789
+    "loader_android_dlwarning\0__loader_cfi_fail\0"
 #if defined(__arm__)
-  // 425
+  // 443
     "__loader_dl_unwind_find_exidx\0"
 #endif
     ;
@@ -255,8 +260,9 @@ static ElfW(Sym) g_libdl_symtab[] = {
   ELFW(SYM_INITIALIZER)(348, &__android_create_namespace, 1),
   ELFW(SYM_INITIALIZER)(382, &__dlvsym, 1),
   ELFW(SYM_INITIALIZER)(398, &__android_dlwarning, 1),
+  ELFW(SYM_INITIALIZER)(425, &__cfi_fail, 1),
 #if defined(__arm__)
-  ELFW(SYM_INITIALIZER)(425, &__dl_unwind_find_exidx, 1),
+  ELFW(SYM_INITIALIZER)(443, &__dl_unwind_find_exidx, 1),
 #endif
 };
 
@@ -273,9 +279,9 @@ static ElfW(Sym) g_libdl_symtab[] = {
 // Note that adding any new symbols here requires stubbing them out in libdl.
 static unsigned g_libdl_buckets[1] = { 1 };
 #if defined(__arm__)
-static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0 };
+static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 0 };
 #else
-static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0 };
+static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0 };
 #endif
 
 static uint8_t __libdl_info_buf[sizeof(soinfo)] __attribute__((aligned(8)));

linker/linker.cpp

@@ -48,6 +48,7 @@
 
 #include "linker.h"
 #include "linker_block_allocator.h"
+#include "linker_cfi.h"
 #include "linker_gdb_support.h"
 #include "linker_globals.h"
 #include "linker_debug.h"
@@ -105,6 +106,12 @@ static const char* const kAsanDefaultLdPaths[] = {
 // Is ASAN enabled?
 static bool g_is_asan = false;
 
+static CFIShadowWriter g_cfi_shadow;
+
+CFIShadowWriter* get_cfi_shadow() {
+  return &g_cfi_shadow;
+}
+
 static bool is_system_library(const std::string& realpath) {
   for (const auto& dir : g_default_namespace.get_default_library_paths()) {
     if (file_is_in_dir(realpath, dir)) {
@@ -1226,7 +1233,7 @@ static bool load_library(android_namespace_t* ns,
 //    target_sdk_version (*candidate != nullptr)
 // 2. The library was not found by soname (*candidate is nullptr)
 static bool find_loaded_library_by_soname(android_namespace_t* ns,
-                                          const char* name, soinfo** candidate) {
+                                         const char* name, soinfo** candidate) {
   *candidate = nullptr;
 
   // Ignore filename with path.
@@ -1504,7 +1511,8 @@ bool find_libraries(android_namespace_t* ns,
 
   bool linked = local_group.visit([&](soinfo* si) {
     if (!si->is_linked()) {
-      if (!si->link_image(global_group, local_group, extinfo)) {
+      if (!si->link_image(global_group, local_group, extinfo) ||
+          !get_cfi_shadow()->AfterLoad(si, solist_get_head())) {
         return false;
       }
     }
@@ -1656,6 +1664,7 @@ static void soinfo_unload(soinfo* soinfos[], size_t count) {
 
   while ((si = local_unload_list.pop_front()) != nullptr) {
     notify_gdb_of_unload(si);
+    get_cfi_shadow()->BeforeUnload(si);
     soinfo_free(si);
   }