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[runtimes][PAC] Harden unwinding when possible (#138571) #143230

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69 changes: 63 additions & 6 deletions compiler-rt/lib/builtins/gcc_personality_v0.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,46 @@ EXCEPTION_DISPOSITION _GCC_specific_handler(PEXCEPTION_RECORD, void *, PCONTEXT,
_Unwind_Personality_Fn);
#endif

#if __has_include(<ptrauth.h>)
#include <ptrauth.h>
#endif

#if defined(__APPLE__) && __has_feature(ptrauth_qualifier)
#if __has_feature(ptrauth_restricted_intptr_qualifier)
#define PERSONALITY_PTRAUTH_RESTRICTED_INTPTR(key, addressDiscriminated, \
discriminatorString) \
__ptrauth_restricted_intptr( \
key, addressDiscriminated, \
ptrauth_string_discriminator(discriminatorString))
#else
#define PERSONALITY_PTRAUTH_RESTRICTED_INTPTR(key, addressDiscriminated, \
discriminatorString) \
__ptrauth(key, addressDiscriminated, \
ptrauth_string_discriminator(discriminatorString))
#endif
#else
#define PERSONALITY_PTRAUTH_RESTRICTED_INTPTR(key, addressDiscriminated, \
discriminatorString)
#endif

// Helper wrappers for pointer auth qualifiers because we use a lot of variants
// Suffixes:
// * PDC : ptrauth_key_process_dependent_code
// * RA : ptrauth_key_return_address
// * FN : ptrauth_key_function_pointer
#define PERSONALITY_PTRAUTH_RI_FN(__discriminator) \
PERSONALITY_PTRAUTH_RESTRICTED_INTPTR(ptrauth_key_function_pointer, \
/*__address_discriminated=*/1, \
__discriminator)
#define PERSONALITY_PTRAUTH_RI_PDC(__discriminator) \
PERSONALITY_PTRAUTH_RESTRICTED_INTPTR(ptrauth_key_process_dependent_code, \
/*__address_discriminated=*/1, \
__discriminator)
#define PERSONALITY_PTRAUTH_RI_RA(__discriminator) \
PERSONALITY_PTRAUTH_RESTRICTED_INTPTR(ptrauth_key_return_address, \
/*__address_discriminated=*/1, \
__discriminator)

// Pointer encodings documented at:
// http://refspecs.freestandards.org/LSB_1.3.0/gLSB/gLSB/ehframehdr.html

Expand Down Expand Up @@ -205,7 +245,8 @@ COMPILER_RT_ABI _Unwind_Reason_Code __gcc_personality_v0(
return continueUnwind(exceptionObject, context);

uintptr_t pc = (uintptr_t)_Unwind_GetIP(context) - 1;
uintptr_t funcStart = (uintptr_t)_Unwind_GetRegionStart(context);
uintptr_t PERSONALITY_PTRAUTH_RI_FN("__gcc_personality_v0'funcStart")
funcStart = (uintptr_t)_Unwind_GetRegionStart(context);
uintptr_t pcOffset = pc - funcStart;

// Parse LSDA header.
Expand All @@ -224,11 +265,14 @@ COMPILER_RT_ABI _Unwind_Reason_Code __gcc_personality_v0(
const uint8_t *callSiteTableEnd = callSiteTableStart + callSiteTableLength;
const uint8_t *p = callSiteTableStart;
while (p < callSiteTableEnd) {
uintptr_t start = readEncodedPointer(&p, callSiteEncoding);
size_t length = readEncodedPointer(&p, callSiteEncoding);
size_t landingPad = readEncodedPointer(&p, callSiteEncoding);
uintptr_t PERSONALITY_PTRAUTH_RI_PDC("__gcc_personality_v0'start") start =
readEncodedPointer(&p, callSiteEncoding);
size_t PERSONALITY_PTRAUTH_RI_PDC("__gcc_personality_v0'length") length =
readEncodedPointer(&p, callSiteEncoding);
size_t PERSONALITY_PTRAUTH_RI_PDC("__gcc_personality_v0'landingPadOffset")
landingPadOffset = readEncodedPointer(&p, callSiteEncoding);
readULEB128(&p); // action value not used for C code
if (landingPad == 0)
if (landingPadOffset == 0)
continue; // no landing pad for this entry
if ((start <= pcOffset) && (pcOffset < (start + length))) {
// Found landing pad for the PC.
Expand All @@ -238,7 +282,20 @@ COMPILER_RT_ABI _Unwind_Reason_Code __gcc_personality_v0(
_Unwind_SetGR(context, __builtin_eh_return_data_regno(0),
(uintptr_t)exceptionObject);
_Unwind_SetGR(context, __builtin_eh_return_data_regno(1), 0);
_Unwind_SetIP(context, (funcStart + landingPad));
#define LANDING_PAD_DISCRIMINATOR "__gcc_personality_v0'landingPad"
size_t PERSONALITY_PTRAUTH_RI_RA(LANDING_PAD_DISCRIMINATOR) landingPad =
funcStart + landingPadOffset;
#if defined(__APPLE__) && __has_feature(ptrauth_qualifier)
uintptr_t stack_pointer = _Unwind_GetGR(context, -2);
const uintptr_t existingDiscriminator = ptrauth_blend_discriminator(
&landingPad, ptrauth_string_discriminator(LANDING_PAD_DISCRIMINATOR));
uintptr_t newIP = (uintptr_t)ptrauth_auth_and_resign(
*(void **)&landingPad, ptrauth_key_function_pointer,
existingDiscriminator, ptrauth_key_return_address, stack_pointer);
_Unwind_SetIP(context, newIP);
#else
_Unwind_SetIP(context, landingPad);
#endif
return _URC_INSTALL_CONTEXT;
}
}
Expand Down
8 changes: 7 additions & 1 deletion compiler-rt/lib/profile/InstrProfilingValue.c
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Expand Up @@ -83,7 +83,13 @@ __llvm_profile_iterate_data(const __llvm_profile_data *Data) {
/* This method is only used in value profiler mock testing. */
COMPILER_RT_VISIBILITY void *
__llvm_get_function_addr(const __llvm_profile_data *Data) {
return Data->FunctionPointer;
void *FP = Data->FunctionPointer;
#if __has_feature(ptrauth_calls)
// This is only used for tests where we compare against what happens to be
// signed pointers.
FP = ptrauth_sign_unauthenticated(FP, VALID_CODE_KEY, 0);
#endif
return FP;
}

/* Allocate an array that holds the pointers to the linked lists of
Expand Down
67 changes: 51 additions & 16 deletions libcxxabi/include/__cxxabi_config.h
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Expand Up @@ -32,22 +32,23 @@
#endif

#if defined(_WIN32)
#if defined(_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS) || (defined(__MINGW32__) && !defined(_LIBCXXABI_BUILDING_LIBRARY))
#define _LIBCXXABI_HIDDEN
#define _LIBCXXABI_DATA_VIS
#define _LIBCXXABI_FUNC_VIS
#define _LIBCXXABI_TYPE_VIS
#elif defined(_LIBCXXABI_BUILDING_LIBRARY)
#define _LIBCXXABI_HIDDEN
#define _LIBCXXABI_DATA_VIS __declspec(dllexport)
#define _LIBCXXABI_FUNC_VIS __declspec(dllexport)
#define _LIBCXXABI_TYPE_VIS __declspec(dllexport)
#else
#define _LIBCXXABI_HIDDEN
#define _LIBCXXABI_DATA_VIS __declspec(dllimport)
#define _LIBCXXABI_FUNC_VIS __declspec(dllimport)
#define _LIBCXXABI_TYPE_VIS __declspec(dllimport)
#endif
# if defined(_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS) || \
(defined(__MINGW32__) && !defined(_LIBCXXABI_BUILDING_LIBRARY))
# define _LIBCXXABI_HIDDEN
# define _LIBCXXABI_DATA_VIS
# define _LIBCXXABI_FUNC_VIS
# define _LIBCXXABI_TYPE_VIS
# elif defined(_LIBCXXABI_BUILDING_LIBRARY)
# define _LIBCXXABI_HIDDEN
# define _LIBCXXABI_DATA_VIS __declspec(dllexport)
# define _LIBCXXABI_FUNC_VIS __declspec(dllexport)
# define _LIBCXXABI_TYPE_VIS __declspec(dllexport)
# else
# define _LIBCXXABI_HIDDEN
# define _LIBCXXABI_DATA_VIS __declspec(dllimport)
# define _LIBCXXABI_FUNC_VIS __declspec(dllimport)
# define _LIBCXXABI_TYPE_VIS __declspec(dllimport)
# endif
#else
#if !defined(_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS)
#define _LIBCXXABI_HIDDEN __attribute__((__visibility__("hidden")))
Expand Down Expand Up @@ -109,4 +110,38 @@
# define _LIBCXXABI_NOEXCEPT noexcept
#endif

#if __has_include(<ptrauth.h>)
# include <ptrauth.h>
#endif

#if defined(__APPLE__) && __has_feature(ptrauth_qualifier)
# define _LIBCXXABI_PTRAUTH(__key, __address_discriminated, __discriminator) \
__ptrauth(__key, __address_discriminated, ptrauth_string_discriminator(__discriminator))
// This work around is required to support divergence in spelling
// during the ptrauth upstreaming process.
# if __has_feature(ptrauth_restricted_intptr_qualifier)
# define _LIBCXXABI_PTRAUTH_RESTRICTED_INTPTR(__key, __address_discriminated, __discriminator) \
__ptrauth_restricted_intptr(__key, __address_discriminated, ptrauth_string_discriminator(__discriminator))
# else
# define _LIBCXXABI_PTRAUTH_RESTRICTED_INTPTR(__key, __address_discriminated, __discriminator) \
__ptrauth(__key, __address_discriminated, ptrauth_string_discriminator(__discriminator))
# endif
#else
# define _LIBCXXABI_PTRAUTH(__key, __address_discriminated, __discriminator)
# define _LIBCXXABI_PTRAUTH_RESTRICTED_INTPTR(__key, __address_discriminated, __discriminator)
#endif

// Helper wrappers for pointer auth qualifiers because we use a lot of variants
// Suffixes:
// * _RI : qualifier is __ptrauth_restricted_intptr
// * PDD : key is ptrauth_key_process_dependent_data
// * FN : key is ptrauth_key_function_pointer
#define _LIBCXXABI_PTRAUTH_PDD(__discriminator) \
_LIBCXXABI_PTRAUTH(ptrauth_key_process_dependent_data, /*__address_discriminated=*/1, __discriminator)
#define _LIBCXXABI_PTRAUTH_FN(__discriminator) \
_LIBCXXABI_PTRAUTH(ptrauth_key_function_pointer, /*__address_discriminated=*/1, __discriminator)
#define _LIBCXXABI_PTRAUTH_RI_PDD(__discriminator) \
_LIBCXXABI_PTRAUTH_RESTRICTED_INTPTR(ptrauth_key_process_dependent_data, /*__address_discriminated=*/1, \
__discriminator)

#endif // ____CXXABI_CONFIG_H
32 changes: 18 additions & 14 deletions libcxxabi/src/cxa_exception.h
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Expand Up @@ -47,10 +47,11 @@ struct _LIBCXXABI_HIDDEN __cxa_exception {
// In Wasm, a destructor returns its argument
void *(_LIBCXXABI_DTOR_FUNC *exceptionDestructor)(void *);
#else
void (_LIBCXXABI_DTOR_FUNC *exceptionDestructor)(void *);
void(_LIBCXXABI_DTOR_FUNC* _LIBCXXABI_PTRAUTH_FN("__cxa_exception::exceptionDestructor")
exceptionDestructor)(void*);
#endif
std::unexpected_handler unexpectedHandler;
std::terminate_handler terminateHandler;
std::unexpected_handler _LIBCXXABI_PTRAUTH_FN("__cxa_exception::unexpectedHandler") unexpectedHandler;
std::terminate_handler _LIBCXXABI_PTRAUTH_FN("__cxa_exception::terminateHandler") terminateHandler;

__cxa_exception *nextException;

Expand All @@ -61,10 +62,10 @@ struct _LIBCXXABI_HIDDEN __cxa_exception {
int propagationCount;
#else
int handlerSwitchValue;
const unsigned char *actionRecord;
const unsigned char *languageSpecificData;
void *catchTemp;
void *adjustedPtr;
const unsigned char* _LIBCXXABI_PTRAUTH_PDD("__cxa_exception::actionRecord") actionRecord;
const unsigned char* _LIBCXXABI_PTRAUTH_PDD("__cxa_exception::languageSpecificData") languageSpecificData;
void* _LIBCXXABI_PTRAUTH_PDD("__cxa_exception::catchTemp") catchTemp;
void* _LIBCXXABI_PTRAUTH_PDD("__cxa_exception::adjustedPtr") adjustedPtr;
#endif

#if !defined(__LP64__) && !defined(_WIN64) && !defined(_LIBCXXABI_ARM_EHABI)
Expand All @@ -79,16 +80,19 @@ struct _LIBCXXABI_HIDDEN __cxa_exception {
// http://sourcery.mentor.com/archives/cxx-abi-dev/msg01924.html
// The layout of this structure MUST match the layout of __cxa_exception, with
// primaryException instead of referenceCount.
// The tags used in the pointer authentication qualifiers also need to match
// those of the corresponding members in __cxa_exception.
struct _LIBCXXABI_HIDDEN __cxa_dependent_exception {
#if defined(__LP64__) || defined(_WIN64) || defined(_LIBCXXABI_ARM_EHABI)
void* reserve; // padding.
void* primaryException;
#endif

std::type_info *exceptionType;
void (_LIBCXXABI_DTOR_FUNC *exceptionDestructor)(void *);
std::unexpected_handler unexpectedHandler;
std::terminate_handler terminateHandler;
void(_LIBCXXABI_DTOR_FUNC* _LIBCXXABI_PTRAUTH_FN("__cxa_exception::exceptionDestructor")
exceptionDestructor)(void*);
std::unexpected_handler _LIBCXXABI_PTRAUTH_FN("__cxa_exception::unexpectedHandler") unexpectedHandler;
std::terminate_handler _LIBCXXABI_PTRAUTH_FN("__cxa_exception::terminateHandler") terminateHandler;

__cxa_exception *nextException;

Expand All @@ -99,10 +103,10 @@ struct _LIBCXXABI_HIDDEN __cxa_dependent_exception {
int propagationCount;
#else
int handlerSwitchValue;
const unsigned char *actionRecord;
const unsigned char *languageSpecificData;
void * catchTemp;
void *adjustedPtr;
const unsigned char* _LIBCXXABI_PTRAUTH_PDD("__cxa_exception::actionRecord") actionRecord;
const unsigned char* _LIBCXXABI_PTRAUTH_PDD("__cxa_exception::languageSpecificData") languageSpecificData;
void* _LIBCXXABI_PTRAUTH_PDD("__cxa_exception::catchTemp") catchTemp;
void* _LIBCXXABI_PTRAUTH_PDD("__cxa_exception::adjustedPtr") adjustedPtr;
#endif

#if !defined(__LP64__) && !defined(_WIN64) && !defined(_LIBCXXABI_ARM_EHABI)
Expand Down
66 changes: 58 additions & 8 deletions libcxxabi/src/cxa_personality.cpp
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Expand Up @@ -22,6 +22,12 @@
#include "private_typeinfo.h"
#include "unwind.h"

#if __has_include(<ptrauth.h>)
# include <ptrauth.h>
#endif

#include "libunwind.h"

// TODO: This is a temporary workaround for libc++abi to recognize that it's being
// built against LLVM's libunwind. LLVM's libunwind started reporting _LIBUNWIND_VERSION
// in LLVM 15 -- we can remove this workaround after shipping LLVM 17. Once we remove
Expand Down Expand Up @@ -527,12 +533,19 @@ get_thrown_object_ptr(_Unwind_Exception* unwind_exception)
namespace
{

#define _LIBCXXABI_PTRAUTH_KEY ptrauth_key_process_dependent_code
typedef const uint8_t* _LIBCXXABI_PTRAUTH_PDD("scan_results::languageSpecificData") lsd_ptr_t;
typedef const uint8_t* _LIBCXXABI_PTRAUTH_PDD("scan_results::actionRecord") action_ptr_t;
#define _LIBCXXABI_PTRAUTH_SCANRESULT_LANDINGPAD_DISC "scan_results::landingPad"
typedef uintptr_t _LIBCXXABI_PTRAUTH_RI_PDD(_LIBCXXABI_PTRAUTH_SCANRESULT_LANDINGPAD_DISC) landing_pad_t;
typedef void* _LIBCXXABI_PTRAUTH_PDD(_LIBCXXABI_PTRAUTH_SCANRESULT_LANDINGPAD_DISC) landing_pad_ptr_t;

struct scan_results
{
int64_t ttypeIndex; // > 0 catch handler, < 0 exception spec handler, == 0 a cleanup
const uint8_t* actionRecord; // Currently unused. Retained to ease future maintenance.
const uint8_t* languageSpecificData; // Needed only for __cxa_call_unexpected
uintptr_t landingPad; // null -> nothing found, else something found
action_ptr_t actionRecord; // Currently unused. Retained to ease future maintenance.
lsd_ptr_t languageSpecificData; // Needed only for __cxa_call_unexpected
landing_pad_t landingPad; // null -> nothing found, else something found
void* adjustedPtr; // Used in cxa_exception.cpp
_Unwind_Reason_Code reason; // One of _URC_FATAL_PHASE1_ERROR,
// _URC_FATAL_PHASE2_ERROR,
Expand All @@ -541,7 +554,33 @@ struct scan_results
};

} // unnamed namespace
}

namespace {
// The logical model for casting authenticated function pointers makes
// it impossible to directly cast them without breaking the authentication,
// as a result we need this pair of helpers.
template <typename PtrType>
void set_landing_pad_as_ptr(scan_results& results, const PtrType& out) {
union {
landing_pad_t* as_landing_pad;
landing_pad_ptr_t* as_pointer;
} u;
u.as_landing_pad = &results.landingPad;
*u.as_pointer = out;
}

static const landing_pad_ptr_t& get_landing_pad_as_ptr(const scan_results& results) {
union {
const landing_pad_t* as_landing_pad;
const landing_pad_ptr_t* as_pointer;
} u;
u.as_landing_pad = &results.landingPad;
return *u.as_pointer;
}
} // unnamed namespace

extern "C" {
static
void
set_registers(_Unwind_Exception* unwind_exception, _Unwind_Context* context,
Expand All @@ -557,7 +596,19 @@ set_registers(_Unwind_Exception* unwind_exception, _Unwind_Context* context,
reinterpret_cast<uintptr_t>(unwind_exception));
_Unwind_SetGR(context, __builtin_eh_return_data_regno(1),
static_cast<uintptr_t>(results.ttypeIndex));
#if defined(__APPLE__) && __has_feature(ptrauth_qualifier)
auto stack_pointer = _Unwind_GetGR(context, UNW_REG_SP);
// We manually re-sign the IP as the __ptrauth qualifiers cannot
// express the required relationship with the destination address
const auto existingDiscriminator = ptrauth_blend_discriminator(
&results.landingPad, ptrauth_string_discriminator(_LIBCXXABI_PTRAUTH_SCANRESULT_LANDINGPAD_DISC));
unw_word_t newIP =
(unw_word_t)ptrauth_auth_and_resign(*(void**)&results.landingPad, _LIBCXXABI_PTRAUTH_KEY, existingDiscriminator,
ptrauth_key_return_address, stack_pointer);
_Unwind_SetIP(context, newIP);
#else
_Unwind_SetIP(context, results.landingPad);
#endif
}

/*
Expand Down Expand Up @@ -691,12 +742,12 @@ static void scan_eh_tab(scan_results &results, _Unwind_Action actions,
// The call sites are ordered in increasing value of start
uintptr_t start = readEncodedPointer(&callSitePtr, callSiteEncoding);
uintptr_t length = readEncodedPointer(&callSitePtr, callSiteEncoding);
uintptr_t landingPad = readEncodedPointer(&callSitePtr, callSiteEncoding);
landing_pad_t landingPad = readEncodedPointer(&callSitePtr, callSiteEncoding);
uintptr_t actionEntry = readULEB128(&callSitePtr);
if ((start <= ipOffset) && (ipOffset < (start + length)))
#else // __USING_SJLJ_EXCEPTIONS__ || __WASM_EXCEPTIONS__
// ip is 1-based index into this table
uintptr_t landingPad = readULEB128(&callSitePtr);
landing_pad_t landingPad = readULEB128(&callSitePtr);
uintptr_t actionEntry = readULEB128(&callSitePtr);
if (--ip == 0)
#endif // __USING_SJLJ_EXCEPTIONS__ || __WASM_EXCEPTIONS__
Expand Down Expand Up @@ -935,8 +986,7 @@ __gxx_personality_v0
results.ttypeIndex = exception_header->handlerSwitchValue;
results.actionRecord = exception_header->actionRecord;
results.languageSpecificData = exception_header->languageSpecificData;
results.landingPad =
reinterpret_cast<uintptr_t>(exception_header->catchTemp);
set_landing_pad_as_ptr(results, exception_header->catchTemp);
results.adjustedPtr = exception_header->adjustedPtr;

// Jump to the handler.
Expand Down Expand Up @@ -970,7 +1020,7 @@ __gxx_personality_v0
exc->handlerSwitchValue = static_cast<int>(results.ttypeIndex);
exc->actionRecord = results.actionRecord;
exc->languageSpecificData = results.languageSpecificData;
exc->catchTemp = reinterpret_cast<void*>(results.landingPad);
exc->catchTemp = get_landing_pad_as_ptr(results);
exc->adjustedPtr = results.adjustedPtr;
#ifdef __WASM_EXCEPTIONS__
// Wasm only uses a single phase (_UA_SEARCH_PHASE), so save the
Expand Down
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