[libunwind][AArch64][ELF][PAC] Fix ptrauth-specific stuff

- Fix build when __APPLE__ is not defined and libc_private.h header is
  absent.
- Do not treat GOT pointers as signed on ELF.

Author: kovdan01

libunwind/src/DwarfParser.hpp

@@ -387,16 +387,22 @@ const char *CFI_Parser<A>::parseCIE(A &addressSpace, pint_t cie,
             .getEncodedP(p, cieContentEnd, cieInfo->personalityEncoding,
                          /*datarelBase=*/0, &resultAddr);
 #if __has_feature(ptrauth_calls)
-              // The GOT for the personality function was signed address authenticated.
-              // Resign is as a regular function pointer.
-              if (cieInfo->personality) {
-                  void* signedPtr = ptrauth_auth_and_resign((void*)cieInfo->personality,
-                                                            ptrauth_key_function_pointer,
-                                                            resultAddr,
-                                                            ptrauth_key_function_pointer,
-                                                            0);
-                  cieInfo->personality = (__typeof(cieInfo->personality))signedPtr;
-              }
+        if (cieInfo->personality) {
+#ifdef __APPLE__
+          // The GOT for the personality function was signed address
+          // authenticated. Resign is as a regular function pointer.
+          void* signedPtr = ptrauth_auth_and_resign((void*)cieInfo->personality,
+                                                     ptrauth_key_function_pointer,
+                                                     resultAddr,
+                                                     ptrauth_key_function_pointer,
+                                                     0);
+#else
+          void* signedPtr = ptrauth_sign_unauthenticated((void*)cieInfo->personality,
+                                                    ptrauth_key_function_pointer,
+                                                    0);
+#endif
+          cieInfo->personality = (__typeof(cieInfo->personality))signedPtr;
+        }
 #endif
         break;
       case 'L':

libunwind/src/Registers.hpp

@@ -1886,7 +1886,7 @@ class _LIBUNWIND_HIDDEN Registers_arm64 {
   void      normalizeNewLinkRegister(reg_t& linkRegister, unw_word_t procInfoFlags) {
     (void)linkRegister;
     (void)procInfoFlags;
-#if __has_feature(ptrauth_calls)
+#if __has_feature(ptrauth_calls) && defined(__APPLE__)
     if (procInfoFlags == ProcInfoFlags_IsARM64Image) {
       // If the current frame is arm64e then the LR should have been signed by
       // the SP.  In this case, we'll just leave it as is.  For other frames,

libunwind/src/UnwindCursor.hpp

@@ -1030,7 +1030,7 @@ class UnwindCursor : public AbstractUnwindCursor{
 #endif
 
   void setProcInfoFlags() {
-#if __has_feature(ptrauth_calls)
+#if __has_feature(ptrauth_calls) && defined(__APPLE__)
     // If the extra field is set, then it is set to the mach header and we can use
     // that to determine which flags to set
     if (_info.extra) {

libunwind/src/libunwind.cpp

@@ -14,7 +14,7 @@
 #include "config.h"
 #include "libunwind_ext.h"
 
-#if __has_feature(ptrauth_calls)
+#if __has_feature(ptrauth_calls) && defined(__APPLE__)
 #include <libc_private.h>
 #endif
 
@@ -141,17 +141,28 @@ _LIBUNWIND_HIDDEN int __unw_set_reg(unw_cursor_t *cursor, unw_regnum_t regNum,
 #if __has_feature(ptrauth_calls)
     // If we are in an arm64e frame, then the PC should have been signed with the sp
     {
-        const mach_header_64 *mh = (const mach_header_64 *)info.extra;
-        // Note, if we don't have mh, we assume this was created by unw_init_local inside
-        // libunwind.dylib itself, and we know we are arm64e.
-        pint_t pc = (pint_t)co->getReg(UNW_REG_IP);
-        if ((mh->cpusubtype & ~CPU_SUBTYPE_MASK) == CPU_SUBTYPE_ARM64_E) {
-            if (ptrauth_auth_and_resign((void*)pc, ptrauth_key_return_address, sp,
-                                        ptrauth_key_return_address, sp) != (void*)pc) {
-                abort_report_np("Bad unwind through arm64e (0x%llX, 0x%llX)->0x%llX\n",
-                                pc, sp, (pint_t)ptrauth_auth_data((void*)pc, ptrauth_key_return_address, sp));
-            }
+      pint_t pc = (pint_t)co->getReg(UNW_REG_IP);
+#ifdef __APPLE__
+      const mach_header_64 *mh = (const mach_header_64 *)info.extra;
+      // Note, if we don't have mh, we assume this was created by unw_init_local inside
+      // libunwind.dylib itself, and we know we are arm64e.
+      if ((mh->cpusubtype & ~CPU_SUBTYPE_MASK) == CPU_SUBTYPE_ARM64_E) {
+#else
+      // FIXME: we should probably look at PAUTH ABI tag note section
+      bool isAuthElf = true;
+      if (isAuthElf) {
+#endif
+        if (ptrauth_auth_and_resign((void*)pc, ptrauth_key_return_address, sp,
+                                    ptrauth_key_return_address, sp) != (void*)pc) {
+#ifdef __APPLE__
+          abort_report_np("Bad unwind through arm64e (0x%llX, 0x%llX)->0x%llX\n",
+                          pc, sp, (pint_t)ptrauth_auth_data((void*)pc, ptrauth_key_return_address, sp));
+#else
+          // FIXME: we probably want to handle it somehow specially
+          return UNW_EINVALIDIP;
+#endif
         }
+      }
     }
 #endif