[libunwind] Remove old keymgr related logic

[ldionne]

Summary

keymgr used to be used on MacOSX <= 10.6, however we don't build libunwind
from scratch for such old systems anymore. Hence, this code isn't useful
anymore.

[kledzik]

LGTM

[ldionne]

Can I get someone from the libunwind review group to vet this change?

[mstorsjo]

Sure, I guess this is fine, 10.6 is rather old at this point...

[vtjnash]

I'm glad to see this is gone. I was just about to file a bug report that this code used to incur a deadlock risk when unw_step was used from a signal handler since macOS 10.9.0 on x86_64, since Apple had removed the other side of this code circa keymgr-28, so it now had been attempting to call malloc. (I'd observed this deadlock occur in testing, and implemented a work around for it downstream, in https://github.com/JuliaLang/julia/pull/37101/commits/fad04d39d592d8e0fcbfba439e8157f582bbc850#diff-86a37833b03dbe7f0874e30469cb1d46R93-R102)

[ldionne]

In D84677#2249914, @vtjnash wrote:

I'm glad to see this is gone. I was just about to file a bug report that this code used to incur a deadlock risk when unw_step was used from a signal handler since macOS 10.9.0 on x86_64, since Apple had removed the other side of this code circa keymgr-28, so it now had been attempting to call malloc. (I'd observed this deadlock occur in testing, and implemented a work around for it downstream, in https://github.com/JuliaLang/julia/pull/37101/commits/fad04d39d592d8e0fcbfba439e8157f582bbc850#diff-86a37833b03dbe7f0874e30469cb1d46R93-R102)

Yay for removing old cruft! :)

libunwind/src/AddressSpace.hpp

 
 #if defined(_LIBUNWIND_ARM_EHABI)
 struct EHABIIndexEntry {
   uint32_t functionOffset;
   uint32_t data;
 };
 #endif
 
-#ifdef __APPLE__
-#include <mach-o/getsect.h>
-namespace libunwind {
-   bool checkKeyMgrRegisteredFDEs(uintptr_t targetAddr, void *&fde);
-}
-#endif
-
 #include "libunwind.h"
 #include "config.h"
 #include "dwarf2.h"
 #include "EHHeaderParser.hpp"
 #include "Registers.hpp"
 
 #ifdef __APPLE__
 
#elif defined(_LIBUNWIND_ARM_EHABI) || defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
   return static_cast<bool>(found);
 #endif
 
   return false;
 }
 
 
 inline bool LocalAddressSpace::findOtherFDE(pint_t targetAddr, pint_t &fde) {
-#ifdef __APPLE__
-  return checkKeyMgrRegisteredFDEs(targetAddr, *((void**)&fde));
-#else
   // TO DO: if OS has way to dynamically register FDEs, check that.
   (void)targetAddr;
   (void)fde;
   return false;
-#endif
 }
 
 inline bool LocalAddressSpace::findFunctionName(pint_t addr, char *buf,
                                                 size_t bufLen,
                                                 unw_word_t *offset) {
 #if _LIBUNWIND_USE_DLADDR
   Dl_info dyldInfo;
   if (dladdr((void *)addr, &dyldInfo)) {

libunwind/src/Unwind_AppleExtras.cpp

 //===--------------------- Unwind_AppleExtras.cpp -------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //
 //===----------------------------------------------------------------------===//
 
 #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 );\

 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;
-}
-
-}
-