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[cfi] Hide runtime implementation in a namespace. 

Move all internal stuff into namespace __cfi.
Remove the double underscore prefix from anything that's now inside
the namespace.

llvm-svn: 258859
This commit is contained in:
Evgeniy Stepanov 2016-01-26 21:06:26 +00:00
parent 3e1701da29
commit 79685810f1
2 changed files with 64 additions and 56 deletions
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115
compiler-rt/lib/cfi/cfi.cc
View File

@ -26,13 +26,15 @@ typedef ElfW(Ehdr) Elf_Ehdr;
#include "ubsan/ubsan_init.h"
#include "ubsan/ubsan_flags.h"
namespace __cfi {
static constexpr uptr kCfiShadowPointerStorageSize = 4096; // 1 page
// Lets hope that the data segment is mapped with 4K pages.
// The pointer to the cfi shadow region is stored at the start of this page.
// The rest of the page is unused and re-mapped read-only.
static char __cfi_shadow_pointer_storage[kCfiShadowPointerStorageSize]
static char cfi_shadow_pointer_storage[kCfiShadowPointerStorageSize]
__attribute__((aligned(kCfiShadowPointerStorageSize)));
static uptr __cfi_shadow_size;
static uptr cfi_shadow_size;
static constexpr uptr kShadowGranularity = 12;
static constexpr uptr kShadowAlign = 1UL << kShadowGranularity; // 4096
@ -41,10 +43,10 @@ static constexpr uint16_t kUncheckedShadow = 0xFFFFU;
// Get the start address of the CFI shadow region.
uptr GetShadow() {
return *reinterpret_cast<uptr *>(&__cfi_shadow_pointer_storage);
return *reinterpret_cast<uptr *>(&cfi_shadow_pointer_storage);
}
static uint16_t *MemToShadow(uptr x, uptr shadow_base) {
uint16_t *MemToShadow(uptr x, uptr shadow_base) {
return (uint16_t *)(shadow_base + ((x >> kShadowGranularity) << 1));
}
@ -93,9 +95,8 @@ public:
};
void ShadowBuilder::Start() {
shadow_ = (uptr)MmapNoReserveOrDie(__cfi_shadow_size, "CFI shadow");
VReport(1, "CFI: shadow at %zx .. %zx\n", shadow_,
shadow_ + __cfi_shadow_size);
shadow_ = (uptr)MmapNoReserveOrDie(cfi_shadow_size, "CFI shadow");
VReport(1, "CFI: shadow at %zx .. %zx\n", shadow_, shadow_ + cfi_shadow_size);
}
void ShadowBuilder::AddUnchecked(uptr begin, uptr end) {
@ -121,19 +122,19 @@ void ShadowBuilder::Add(uptr begin, uptr end, uptr cfi_check) {
#if SANITIZER_LINUX
void ShadowBuilder::Install() {
MprotectReadOnly(shadow_, __cfi_shadow_size);
MprotectReadOnly(shadow_, cfi_shadow_size);
uptr main_shadow = GetShadow();
if (main_shadow) {
// Update.
void *res = mremap((void *)shadow_, __cfi_shadow_size, __cfi_shadow_size,
void *res = mremap((void *)shadow_, cfi_shadow_size, cfi_shadow_size,
MREMAP_MAYMOVE | MREMAP_FIXED, main_shadow);
CHECK(res != MAP_FAILED);
} else {
// Initial setup.
CHECK_EQ(kCfiShadowPointerStorageSize, GetPageSizeCached());
CHECK_EQ(0, GetShadow());
*reinterpret_cast<uptr *>(&__cfi_shadow_pointer_storage) = shadow_;
MprotectReadOnly((uptr)&__cfi_shadow_pointer_storage,
*reinterpret_cast<uptr *>(&cfi_shadow_pointer_storage) = shadow_;
MprotectReadOnly((uptr)&cfi_shadow_pointer_storage,
kCfiShadowPointerStorageSize);
CHECK_EQ(shadow_, GetShadow());
}
@ -147,7 +148,7 @@ void ShadowBuilder::Install() {
// Other platforms can, hopefully, just do
// dlopen(RTLD_NOLOAD | RTLD_LAZY)
// dlsym("__cfi_check").
static uptr find_cfi_check_in_dso(dl_phdr_info *info) {
uptr find_cfi_check_in_dso(dl_phdr_info *info) {
const ElfW(Dyn) *dynamic = nullptr;
for (int i = 0; i < info->dlpi_phnum; ++i) {
if (info->dlpi_phdr[i].p_type == PT_DYNAMIC) {
@ -201,7 +202,7 @@ static uptr find_cfi_check_in_dso(dl_phdr_info *info) {
return 0;
}
static int dl_iterate_phdr_cb(dl_phdr_info *info, size_t size, void *data) {
int dl_iterate_phdr_cb(dl_phdr_info *info, size_t size, void *data) {
uptr cfi_check = find_cfi_check_in_dso(info);
if (cfi_check)
VReport(1, "Module '%s' __cfi_check %zx\n", info->dlpi_name, cfi_check);
@ -230,29 +231,29 @@ static int dl_iterate_phdr_cb(dl_phdr_info *info, size_t size, void *data) {
}
// Init or update shadow for the current set of loaded libraries.
static void UpdateShadow() {
void UpdateShadow() {
ShadowBuilder b;
b.Start();
dl_iterate_phdr(dl_iterate_phdr_cb, &b);
b.Install();
}
static void InitShadow() {
void InitShadow() {
// No difference, really.
UpdateShadow();
}
static THREADLOCAL int in_loader;
static BlockingMutex shadow_update_lock(LINKER_INITIALIZED);
THREADLOCAL int in_loader;
BlockingMutex shadow_update_lock(LINKER_INITIALIZED);
static void EnterLoader() {
void EnterLoader() {
if (in_loader == 0) {
shadow_update_lock.Lock();
}
++in_loader;
}
static void ExitLoader() {
void ExitLoader() {
CHECK(in_loader > 0);
--in_loader;
UpdateShadow();
@ -261,29 +262,7 @@ static void ExitLoader() {
}
}
// 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
// running. It's unclear how to fix this without some extra help from libc.
// In glibc, mmap inside dlopen is not interceptable.
// Maybe a seccomp-bpf filter?
// 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) {
EnterLoader();
void *handle = REAL(dlopen)(filename, flag);
ExitLoader();
return handle;
}
INTERCEPTOR(int, dlclose, void *handle) {
EnterLoader();
int res = REAL(dlclose)(handle);
ExitLoader();
return res;
}
static ALWAYS_INLINE void CfiSlowPathCommon(u64 CallSiteTypeId, void *Ptr,
ALWAYS_INLINE void CfiSlowPathCommon(u64 CallSiteTypeId, void *Ptr,
void *DiagData) {
uptr Addr = (uptr)Ptr;
VReport(3, "__cfi_slowpath: %llx, %p\n", CallSiteTypeId, Ptr);
@ -307,17 +286,7 @@ static ALWAYS_INLINE void CfiSlowPathCommon(u64 CallSiteTypeId, void *Ptr,
cfi_check(CallSiteTypeId, Ptr, DiagData);
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
__cfi_slowpath(u64 CallSiteTypeId, void *Ptr) {
CfiSlowPathCommon(CallSiteTypeId, Ptr, nullptr);
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
__cfi_slowpath_diag(u64 CallSiteTypeId, void *Ptr, void *DiagData) {
CfiSlowPathCommon(CallSiteTypeId, Ptr, DiagData);
}
static void InitializeFlags() {
void InitializeFlags() {
SetCommonFlagsDefaults();
#ifdef CFI_ENABLE_DIAG
__ubsan::Flags *uf = __ubsan::flags();
@ -347,6 +316,42 @@ static void InitializeFlags() {
}
}
} // namespace __cfi
using namespace __cfi;
extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
__cfi_slowpath(u64 CallSiteTypeId, void *Ptr) {
CfiSlowPathCommon(CallSiteTypeId, Ptr, nullptr);
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE void
__cfi_slowpath_diag(u64 CallSiteTypeId, void *Ptr, void *DiagData) {
CfiSlowPathCommon(CallSiteTypeId, Ptr, DiagData);
}
// 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
// running. It's unclear how to fix this without some extra help from libc.
// In glibc, mmap inside dlopen is not interceptable.
// Maybe a seccomp-bpf filter?
// 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) {
EnterLoader();
void *handle = REAL(dlopen)(filename, flag);
ExitLoader();
return handle;
}
INTERCEPTOR(int, dlclose, void *handle) {
EnterLoader();
int res = REAL(dlclose)(handle);
ExitLoader();
return res;
}
extern "C" SANITIZER_INTERFACE_ATTRIBUTE
#if !SANITIZER_CAN_USE_PREINIT_ARRAY
// On ELF platforms, the constructor is invoked using .preinit_array (see below)
@ -358,8 +363,8 @@ void __cfi_init() {
uptr vma = GetMaxVirtualAddress();
// Shadow is 2 -> 2**kShadowGranularity.
__cfi_shadow_size = (vma >> (kShadowGranularity - 1)) + 1;
VReport(1, "CFI: VMA size %zx, shadow size %zx\n", vma, __cfi_shadow_size);
cfi_shadow_size = (vma >> (kShadowGranularity - 1)) + 1;
VReport(1, "CFI: VMA size %zx, shadow size %zx\n", vma, cfi_shadow_size);
InitShadow();

5
compiler-rt/test/cfi/cross-dso/shadow_is_read_only.cpp
View File

@ -33,10 +33,13 @@ extern "C" A *create_A() { return new A(); }
#else
constexpr unsigned kShadowGranularity = 12;
namespace __cfi {
uintptr_t GetShadow();
}
void write_shadow(void *ptr) {
uintptr_t base = GetShadow();
uintptr_t base = __cfi::GetShadow();
uint16_t *s =
(uint16_t *)(base + (((uintptr_t)ptr >> kShadowGranularity) << 1));
fprintf(stderr, "going to crash\n");