[PATCH v2 3/5] libdwfl, aarch64: Demangle return addresses using a PAC mask

[Steve Capper]

From: German Gomez <german.go...@arm.com>

Demangle mangled return addresses on AARCH64. The value of the masks is
stored in the struct Dwfl_Thread.

Signed-off-by: German Gomez <german.go...@arm.com>
[SteveC: remove dwfl_thread_state_aarch64_pauth]
Signed-off-by: Steve Capper <steve.cap...@arm.com>
---
 libdwfl/dwfl_frame.c   |  3 +++
 libdwfl/frame_unwind.c | 14 +++++++++++++-
 libdwfl/libdwflP.h     |  6 ++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/libdwfl/dwfl_frame.c b/libdwfl/dwfl_frame.c
index 5ee71dd4..8af8843f 100644
--- a/libdwfl/dwfl_frame.c
+++ b/libdwfl/dwfl_frame.c
@@ -269,6 +269,8 @@ dwfl_getthreads (Dwfl *dwfl, int (*callback) (Dwfl_Thread 
*thread, void *arg),
   thread.process = process;
   thread.unwound = NULL;
   thread.callbacks_arg = NULL;
+  thread.aarch64.pauth_insn_mask = 0;
+
   for (;;)
     {
       thread.tid = process->callbacks->next_thread (dwfl,
@@ -339,6 +341,7 @@ getthread (Dwfl *dwfl, pid_t tid,
       thread.process = process;
       thread.unwound = NULL;
       thread.callbacks_arg = NULL;
+      thread.aarch64.pauth_insn_mask = 0;
 
       if (process->callbacks->get_thread (dwfl, tid, process->callbacks_arg,
                                          &thread.callbacks_arg))
diff --git a/libdwfl/frame_unwind.c b/libdwfl/frame_unwind.c
index 1e2f0255..ab444d25 100644
--- a/libdwfl/frame_unwind.c
+++ b/libdwfl/frame_unwind.c
@@ -599,7 +599,19 @@ handle_cfi (Dwfl_Frame *state, Dwarf_Addr pc, Dwarf_CFI 
*cfi, Dwarf_Addr bias)
 
       /* Some architectures encode some extra info in the return address.  */
       if (regno == frame->fde->cie->return_address_register)
-       regval &= ebl_func_addr_mask (ebl);
+       {
+         regval &= ebl_func_addr_mask (ebl);
+
+         /* In aarch64, pseudo-register RA_SIGN_STATE indicates whether the
+            return address needs demangling using the PAC mask from the
+            thread. */
+         if (cfi->e_machine == EM_AARCH64 &&
+             frame->nregs > DW_AARCH64_RA_SIGN_STATE &&
+             frame->regs[DW_AARCH64_RA_SIGN_STATE].value & 0x1)
+           {
+             regval &= ~(state->thread->aarch64.pauth_insn_mask);
+           }
+       }
 
       /* This is another strange PPC[64] case.  There are two
         registers numbers that can represent the same DWARF return
diff --git a/libdwfl/libdwflP.h b/libdwfl/libdwflP.h
index e0055d65..d0a5f056 100644
--- a/libdwfl/libdwflP.h
+++ b/libdwfl/libdwflP.h
@@ -244,6 +244,12 @@ struct Dwfl_Thread
   /* Bottom (innermost) frame while we're initializing, NULL afterwards.  */
   Dwfl_Frame *unwound;
   void *callbacks_arg;
+
+  /* Data for handling AARCH64 (currently limited to demangling PAC from
+     return addresses). */
+  struct {
+    Dwarf_Addr pauth_insn_mask;
+  } aarch64;
 };
 
 /* See its typedef in libdwfl.h.  */
-- 
2.43.0