commit c049419d96d82e4f5834133d5f68f6054e46f789
Author: Mark Wielaard <mark@klomp.org>
Date:   Tue Apr 10 16:13:34 2018 +0200

    libdwfl: Handle unwind frame when the return address register isn't set.
    
    When we have unwound the frame and then cannot set the return address
    we wouldn't set any error. That meant that a dwfl_thread_getframes ()
    call could end in an error, but without any dwfl_errno set, producing
    the "no error" error message.
    
    If we cannot set the return address at the end of unwinding the frame
    that means that either the return address register is bogus (error),
    or that the return address is undefined (end of the call stack).
    
    This fixes the run-backtrace-native-biarch.sh testcase for me on an
    i386 on x86_64 setup with gcc 7.2.1 and glibc 2.17.
    
    Signed-off-by: Mark Wielaard <mark@klomp.org>

diff --git a/libdwfl/frame_unwind.c b/libdwfl/frame_unwind.c
index eaea495..8da691e 100644
--- a/libdwfl/frame_unwind.c
+++ b/libdwfl/frame_unwind.c
@@ -632,24 +632,38 @@ handle_cfi (Dwfl_Frame *state, Dwarf_Addr pc, Dwarf_CFI *cfi, Dwarf_Addr bias)
 	    ra_set = true;
 	}
     }
-  if (unwound->pc_state == DWFL_FRAME_STATE_ERROR
-      && __libdwfl_frame_reg_get (unwound,
-				  frame->fde->cie->return_address_register,
-				  &unwound->pc))
+  if (unwound->pc_state == DWFL_FRAME_STATE_ERROR)
     {
-      /* PPC32 __libc_start_main properly CFI-unwinds PC as zero.  Currently
-	 none of the archs supported for unwinding have zero as a valid PC.  */
-      if (unwound->pc == 0)
-	unwound->pc_state = DWFL_FRAME_STATE_PC_UNDEFINED;
+      if (__libdwfl_frame_reg_get (unwound,
+				   frame->fde->cie->return_address_register,
+				   &unwound->pc))
+	{
+	  /* PPC32 __libc_start_main properly CFI-unwinds PC as zero.
+	     Currently none of the archs supported for unwinding have
+	     zero as a valid PC.  */
+	  if (unwound->pc == 0)
+	    unwound->pc_state = DWFL_FRAME_STATE_PC_UNDEFINED;
+	  else
+	    {
+	      unwound->pc_state = DWFL_FRAME_STATE_PC_SET;
+	      /* In SPARC the return address register actually contains
+		 the address of the call instruction instead of the return
+		 address.  Therefore we add here an offset defined by the
+		 backend.  Most likely 0.  */
+	      unwound->pc += ebl_ra_offset (ebl);
+	    }
+	}
       else
-        {
-          unwound->pc_state = DWFL_FRAME_STATE_PC_SET;
-          /* In SPARC the return address register actually contains
-             the address of the call instruction instead of the return
-             address.  Therefore we add here an offset defined by the
-             backend.  Most likely 0.  */
-          unwound->pc += ebl_ra_offset (ebl);
-        }
+	{
+	  /* We couldn't set the return register, either it was bogus,
+	     or the return pc is undefined, maybe end of call stack.  */
+	  unsigned pcreg = frame->fde->cie->return_address_register;
+	  if (! ebl_dwarf_to_regno (ebl, &pcreg)
+	      || pcreg >= ebl_frame_nregs (ebl))
+	    __libdwfl_seterrno (DWFL_E_INVALID_REGISTER);
+	  else
+	    unwound->pc_state = DWFL_FRAME_STATE_PC_UNDEFINED;
+	}
     }
   free (frame);
 }

commit 7be459fa531b1284408bf16616422b8dbf193278
Author: Mark Wielaard <mark@klomp.org>
Date:   Wed Apr 11 10:37:45 2018 +0200

    aarch64: Add default cfi rule to restore SP from CFA address.
    
    The CFA is set by default to the stack pointer of the previous frame.
    So that is also how we can always restore the SP. This default aarch64
    CFI rule is necessary on Fedora 28 with GCC8 to make the run-deleted.sh
    and run-backtrace-dwarf.sh testcases work.
    
    Signed-off-by: Mark Wielaard <mark@klomp.org>

diff --git a/backends/aarch64_cfi.c b/backends/aarch64_cfi.c
index acbb9b6..a5579ab 100644
--- a/backends/aarch64_cfi.c
+++ b/backends/aarch64_cfi.c
@@ -1,5 +1,5 @@
-/* arm ABI-specified defaults for DWARF CFI.
-   Copyright (C) 2013 Red Hat, Inc.
+/* arm64 ABI-specified defaults for DWARF CFI.
+   Copyright (C) 2013, 2018 Red Hat, Inc.
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -62,6 +62,9 @@ aarch64_abi_cfi (Ebl *ebl __attribute__ ((unused)), Dwarf_CIE *abi_info)
       /* The Frame Pointer (FP, r29) and Link Register (LR, r30).  */
       SV (29), SV (30),
 
+      /* The Stack Pointer (r31) is restored from CFA address by default.  */
+      DW_CFA_val_offset, ULEB128_7 (31), ULEB128_7 (0),
+
       /* Callee-saved fpregs v8-v15.  v0 == 64.  */
       SV (72), SV (73), SV (74), SV (75),
       SV (76), SV (77), SV (78), SV (79),
diff --git a/tests/run-addrcfi.sh b/tests/run-addrcfi.sh
index 376a6dc..fd89d02 100755
--- a/tests/run-addrcfi.sh
+++ b/tests/run-addrcfi.sh
@@ -3637,7 +3637,7 @@ dwarf_cfi_addrframe (.eh_frame): no matching address range
 	integer reg28 (x28): same_value
 	integer reg29 (x29): same_value
 	integer reg30 (x30): same_value
-	integer reg31 (sp): undefined
+	integer reg31 (sp): location expression: call_frame_cfa stack_value
 	integer reg33 (elr): undefined
 	FP/SIMD reg64 (v0): undefined
 	FP/SIMD reg65 (v1): undefined