Make some effort to deal with "signed" PC register for ARM

Just mask off the top 16 bits of the instruction pointer, and add
definitions for the RA signed state.

Author: peadar

dump.cc

@@ -191,9 +191,6 @@ dumpCFAInsn(std::ostream &os, Dwarf::DWARFReader *r)
             jo.field("size", r->getuleb128());
             break;
 
-        case DW_CFA_GNU_window_save:
-            break;
-
         case DW_CFA_GNU_negative_offset_extended:
         case DW_CFA_offset_extended_sf: {
             auto reg = r->getuleb128();
@@ -209,6 +206,14 @@ dumpCFAInsn(std::ostream &os, Dwarf::DWARFReader *r)
         case DW_CFA_restore_state:
             break;
 
+#ifndef __aarch64__
+        case DW_CFA_GNU_window_save:
+            break;
+#else
+	case DW_CFA_AARCH64_negate_ra_state:
+            break;
+#endif
+
         default:
             throw (Exception() << "unknown CFA op " << std::hex << int(op)) << std::dec;
     }

dwarfproc.cc

@@ -26,7 +26,12 @@ StackFrame::getCoreRegs(Elf::CoreRegisters &core) const
 Elf::Addr
 StackFrame::rawIP() const
 {
+#ifdef __aarch64__
+    // remove RA signing artefacts.
+    return 0xffffffffffff & Elf::getReg(regs, IPREG);
+#else
     return Elf::getReg(regs, IPREG);
+#endif
 }
 
 ProcessLocation

libpstack/dwarf.h

@@ -1168,7 +1168,14 @@ CIE::execInsns(const CallFrame &dframe, uintptr_t start, uintptr_t end, uintmax_
             }
 
             // Can't deal with anything else yet.
+#ifdef __aarch64__
+	    case DW_CFA_AARCH64_negate_ra_state:
+	       break;
+
+#else
+	    // systems with register windows, i.e., sparc
             case DW_CFA_GNU_window_save:
+#endif
             case DW_CFA_GNU_negative_offset_extended:
             default:
                 throw (Exception() << "unhandled secondary CFA instruction " << op);

libpstack/dwarf/cfainsns.h

@@ -29,7 +29,12 @@ DWARF_CFA_INSN(DW_CFA_val_expression, 0x16)
     // }
 
 DWARF_CFA_INSN(DW_CFA_lo_user, 0x1c)
+#ifdef __aarch64__
+DWARF_CFA_INSN(DW_CFA_AARCH64_negate_ra_state, 0x2d)
+#else
 DWARF_CFA_INSN(DW_CFA_GNU_window_save, 0x2d)
+#endif
+
 DWARF_CFA_INSN(DW_CFA_GNU_args_size, 0x2e)
 DWARF_CFA_INSN(DW_CFA_GNU_negative_offset_extended, 0x2f)
 DWARF_CFA_INSN(DW_CFA_hi_user, 0x3f)