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clang-p2996/libunwind/src/Unwind_AppleExtras.cpp
Saleem Abdulrasool 9ebbda838f SjLj: make the SjLj implementation more portable 
This moves the definition of the internal helpers
`__Unwind_SjLj_GetTopOfFunctionStack` and
`__Unwind_SjLj_SetTopOfFunctionStack` into `Unwind-sjlj.c`.  These are
not extra functions specific to Apple, but rather are internal
implementation details of SjLj support in the LLVM libunwind
implementation.

This allows us to remove the internal header unwind_ext.h, as these
functions are not meant to be used as SPI either.  Because they are
static, they will be given implicit hidden visibility, but due to the
simplicity should get fully inlined into the actual use.

Use the C11 standard static TLS annotation (`_Thread_local`) if
possible, otherwise, use the Windows specific `__declspec(thread)` when
targeting Windows or the GNU `__thread` extension.  In theory, it should
be possible for this implementation to use a `pthread_setspecific` and
`pthread_getspecific` on platforms with pthreads or `SetFlsValue` and
`GetFlsValue` on Windows for non-static TLS.  However, static TLS tends
to be significantly faster, so we really should prefer that over the
dynamic TLS approach.  On Apple environments, when not building for the
loader (dyld), use the pre-allocated TLS slot in the loader rather than
the local static TLS variable.

Note that the un-threaded support of libunwind is still present as
before, however, it is unsafe to use in a threaded environment as the
cleanup stack may be mutated incorrectly due to lack of locking across
threads.  In the static TLS model, the lock is unneeded as each thread
of execution retains its own copy of the cleanup stack.

Take the opportunity to clean up the comment block, removing the iOS
specific note as the SjLj implementation can be used outside of the
context of iOS.  Convert the rest of the explanation to a doxygen style
comment block.

llvm-svn: 314632
2017-10-01 20:06:48 +00:00

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//===--------------------- Unwind_AppleExtras.cpp -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//
//===----------------------------------------------------------------------===//
#include "config.h"
#include "AddressSpace.hpp"
#include "DwarfParser.hpp"
// private keymgr stuff
#define KEYMGR_GCC3_DW2_OBJ_LIST 302
extern "C" {
extern void _keymgr_set_and_unlock_processwide_ptr(int key, void *ptr);
extern void *_keymgr_get_and_lock_processwide_ptr(int key);
}
// undocumented libgcc "struct object"
struct libgcc_object {
void *start;
void *unused1;
void *unused2;
void *fde;
unsigned long encoding;
void *fde_end;
libgcc_object *next;
};
// undocumented libgcc "struct km_object_info" referenced by
// KEYMGR_GCC3_DW2_OBJ_LIST
struct libgcc_object_info {
libgcc_object *seen_objects;
libgcc_object *unseen_objects;
unsigned spare[2];
};
// static linker symbols to prevent wrong two level namespace for _Unwind symbols
#if defined(__arm__)
#define NOT_HERE_BEFORE_5_0(sym) \
extern const char sym##_tmp30 __asm("$ld$hide$os3.0$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp30 = 0; \
extern const char sym##_tmp31 __asm("$ld$hide$os3.1$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp31 = 0; \
extern const char sym##_tmp32 __asm("$ld$hide$os3.2$_" #sym );\
__attribute__((visibility("default"))) const char sym##_tmp32 = 0; \
extern const char sym##_tmp40 __asm("$ld$hide$os4.0$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp40 = 0; \
extern const char sym##_tmp41 __asm("$ld$hide$os4.1$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp41 = 0; \
extern const char sym##_tmp42 __asm("$ld$hide$os4.2$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp42 = 0; \
extern const char sym##_tmp43 __asm("$ld$hide$os4.3$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp43 = 0;
#elif defined(__arm64__)
#define NOT_HERE_BEFORE_10_6(sym)
#define NEVER_HERE(sym)
#else
#define NOT_HERE_BEFORE_10_6(sym) \
extern const char sym##_tmp4 __asm("$ld$hide$os10.4$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp4 = 0; \
extern const char sym##_tmp5 __asm("$ld$hide$os10.5$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp5 = 0;
#define NEVER_HERE(sym) \
extern const char sym##_tmp4 __asm("$ld$hide$os10.4$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp4 = 0; \
extern const char sym##_tmp5 __asm("$ld$hide$os10.5$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp5 = 0; \
extern const char sym##_tmp6 __asm("$ld$hide$os10.6$_" #sym ); \
__attribute__((visibility("default"))) const char sym##_tmp6 = 0;
#endif
#if defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)
//
// symbols in libSystem.dylib in 10.6 and later, but are in libgcc_s.dylib in
// earlier versions
//
NOT_HERE_BEFORE_10_6(_Unwind_DeleteException)
NOT_HERE_BEFORE_10_6(_Unwind_Find_FDE)
NOT_HERE_BEFORE_10_6(_Unwind_ForcedUnwind)
NOT_HERE_BEFORE_10_6(_Unwind_GetGR)
NOT_HERE_BEFORE_10_6(_Unwind_GetIP)
NOT_HERE_BEFORE_10_6(_Unwind_GetLanguageSpecificData)
NOT_HERE_BEFORE_10_6(_Unwind_GetRegionStart)
NOT_HERE_BEFORE_10_6(_Unwind_RaiseException)
NOT_HERE_BEFORE_10_6(_Unwind_Resume)
NOT_HERE_BEFORE_10_6(_Unwind_SetGR)
NOT_HERE_BEFORE_10_6(_Unwind_SetIP)
NOT_HERE_BEFORE_10_6(_Unwind_Backtrace)
NOT_HERE_BEFORE_10_6(_Unwind_FindEnclosingFunction)
NOT_HERE_BEFORE_10_6(_Unwind_GetCFA)
NOT_HERE_BEFORE_10_6(_Unwind_GetDataRelBase)
NOT_HERE_BEFORE_10_6(_Unwind_GetTextRelBase)
NOT_HERE_BEFORE_10_6(_Unwind_Resume_or_Rethrow)
NOT_HERE_BEFORE_10_6(_Unwind_GetIPInfo)
NOT_HERE_BEFORE_10_6(__register_frame)
NOT_HERE_BEFORE_10_6(__deregister_frame)
//
// symbols in libSystem.dylib for compatibility, but we don't want any new code
// using them
//
NEVER_HERE(__register_frame_info_bases)
NEVER_HERE(__register_frame_info)
NEVER_HERE(__register_frame_info_table_bases)
NEVER_HERE(__register_frame_info_table)
NEVER_HERE(__register_frame_table)
NEVER_HERE(__deregister_frame_info)
NEVER_HERE(__deregister_frame_info_bases)
#endif // defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)
#if defined(_LIBUNWIND_BUILD_SJLJ_APIS)
//
// symbols in libSystem.dylib in iOS 5.0 and later, but are in libgcc_s.dylib in
// earlier versions
//
NOT_HERE_BEFORE_5_0(_Unwind_GetLanguageSpecificData)
NOT_HERE_BEFORE_5_0(_Unwind_GetRegionStart)
NOT_HERE_BEFORE_5_0(_Unwind_GetIP)
NOT_HERE_BEFORE_5_0(_Unwind_SetGR)
NOT_HERE_BEFORE_5_0(_Unwind_SetIP)
NOT_HERE_BEFORE_5_0(_Unwind_DeleteException)
NOT_HERE_BEFORE_5_0(_Unwind_SjLj_Register)
NOT_HERE_BEFORE_5_0(_Unwind_GetGR)
NOT_HERE_BEFORE_5_0(_Unwind_GetIPInfo)
NOT_HERE_BEFORE_5_0(_Unwind_GetCFA)
NOT_HERE_BEFORE_5_0(_Unwind_SjLj_Resume)
NOT_HERE_BEFORE_5_0(_Unwind_SjLj_RaiseException)
NOT_HERE_BEFORE_5_0(_Unwind_SjLj_Resume_or_Rethrow)
NOT_HERE_BEFORE_5_0(_Unwind_SjLj_Unregister)
#endif // defined(_LIBUNWIND_BUILD_SJLJ_APIS)
namespace libunwind {
_LIBUNWIND_HIDDEN
bool checkKeyMgrRegisteredFDEs(uintptr_t pc, void *&fde) {
#if __MAC_OS_X_VERSION_MIN_REQUIRED
// lastly check for old style keymgr registration of dynamically generated
// FDEs acquire exclusive access to libgcc_object_info
libgcc_object_info *head = (libgcc_object_info *)
_keymgr_get_and_lock_processwide_ptr(KEYMGR_GCC3_DW2_OBJ_LIST);
if (head != NULL) {
// look at each FDE in keymgr
for (libgcc_object *ob = head->unseen_objects; ob != NULL; ob = ob->next) {
CFI_Parser<LocalAddressSpace>::FDE_Info fdeInfo;
CFI_Parser<LocalAddressSpace>::CIE_Info cieInfo;
const char *msg = CFI_Parser<LocalAddressSpace>::decodeFDE(
LocalAddressSpace::sThisAddressSpace,
(uintptr_t)ob->fde, &fdeInfo, &cieInfo);
if (msg == NULL) {
// Check if this FDE is for a function that includes the pc
if ((fdeInfo.pcStart <= pc) && (pc < fdeInfo.pcEnd)) {
fde = (void*)fdeInfo.pcStart;
_keymgr_set_and_unlock_processwide_ptr(KEYMGR_GCC3_DW2_OBJ_LIST,
head);
return true;
}
}
}
}
// release libgcc_object_info
_keymgr_set_and_unlock_processwide_ptr(KEYMGR_GCC3_DW2_OBJ_LIST, head);
#else
(void)pc;
(void)fde;
#endif
return false;
}
}
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