[AArch64][4/4] libgcc unwinder support for return address signing

libgcc/
	* config/aarch64/aarch64-unwind.h: New file.
	(DWARF_REGNUM_AARCH64_RA_STATE): Define.
	(MD_POST_EXTRACT_ROOT_ADDR): New target marcro and define it on AArch64.
	(MD_POST_EXTRACT_FRAME_ADDR): Likewise.
	(MD_POST_FROB_EH_HANDLER_ADDR): Likewise.
	(MD_FROB_UPDATE_CONTEXT): Define it on AArch64.
	(aarch64_post_extract_frame_addr): New function.
	(aarch64_post_frob_eh_handler_addr): New function.
	(aarch64_frob_update_context): New function.
	* config/aarch64/linux-unwind.h: Include aarch64-unwind.h
	* config.host (aarch64*-*-elf, aarch64*-*-rtems*,
	aarch64*-*-freebsd*):
	Initialize md_unwind_header to include aarch64-unwind.h.
	* unwind-dw2.c (struct _Unwind_Context): Define "RA_A_SIGNED_BIT".
	(execute_cfa_program): Multiplex DW_CFA_GNU_window_save for
	__aarch64__.
	(uw_update_context): Honor MD_POST_EXTRACT_FRAME_ADDR.
	(uw_init_context_1): Honor MD_POST_EXTRACT_ROOT_ADDR.
	(uw_frob_return_addr): New function.
	(uw_install_context): Use uw_frob_return_addr.

From-SVN: r244673

libgcc/ChangeLog

@@ -1,3 +1,26 @@
+2017-01-19  Jiong Wang  <jiong.wang@arm.com>
+
+	* config/aarch64/aarch64-unwind.h: New file.
+	(DWARF_REGNUM_AARCH64_RA_STATE): Define.
+	(MD_POST_EXTRACT_ROOT_ADDR): New target marcro and define it on AArch64.
+	(MD_POST_EXTRACT_FRAME_ADDR): Likewise.
+	(MD_POST_FROB_EH_HANDLER_ADDR): Likewise.
+	(MD_FROB_UPDATE_CONTEXT): Define it on AArch64.
+	(aarch64_post_extract_frame_addr): New function.
+	(aarch64_post_frob_eh_handler_addr): New function.
+	(aarch64_frob_update_context): New function.
+	* config/aarch64/linux-unwind.h: Include aarch64-unwind.h
+	* config.host (aarch64*-*-elf, aarch64*-*-rtems*,
+	aarch64*-*-freebsd*):
+	Initialize md_unwind_header to include aarch64-unwind.h.
+	* unwind-dw2.c (struct _Unwind_Context): Define "RA_A_SIGNED_BIT".
+	(execute_cfa_program): Multiplex DW_CFA_GNU_window_save for
+	__aarch64__.
+	(uw_update_context): Honor MD_POST_EXTRACT_FRAME_ADDR.
+	(uw_init_context_1): Honor MD_POST_EXTRACT_ROOT_ADDR.
+	(uw_frob_return_addr): New function.
+	(uw_install_context): Use uw_frob_return_addr.
+
 2017-01-17  Jakub Jelinek  <jakub@redhat.com>
 
 	PR other/79046

libgcc/config.host

@@ -331,11 +331,13 @@ aarch64*-*-elf | aarch64*-*-rtems*)
 	extra_parts="$extra_parts crtfastmath.o"
 	tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
 	tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp t-crtfm"
+	md_unwind_header=aarch64/aarch64-unwind.h
 	;;
 aarch64*-*-freebsd*)
 	extra_parts="$extra_parts crtfastmath.o"
 	tmake_file="${tmake_file} ${cpu_type}/t-aarch64"
 	tmake_file="${tmake_file} ${cpu_type}/t-softfp t-softfp t-crtfm"
+	md_unwind_header=aarch64/aarch64-unwind.h
 	;;
 aarch64*-*-linux*)
 	extra_parts="$extra_parts crtfastmath.o"

libgcc/config/aarch64/linux-unwind.h

@@ -24,6 +24,7 @@
 
 #include <signal.h>
 #include <sys/ucontext.h>
+#include "config/aarch64/aarch64-unwind.h"
 
 
 /* Since insns are always stored LE, on a BE system the opcodes will

libgcc/unwind-dw2.c

@@ -136,6 +136,8 @@ struct _Unwind_Context
 #define SIGNAL_FRAME_BIT ((~(_Unwind_Word) 0 >> 1) + 1)
   /* Context which has version/args_size/by_value fields.  */
 #define EXTENDED_CONTEXT_BIT ((~(_Unwind_Word) 0 >> 2) + 1)
+  /* Bit reserved on AArch64, return address has been signed with A key.  */
+#define RA_A_SIGNED_BIT ((~(_Unwind_Word) 0 >> 3) + 1)
   _Unwind_Word flags;
   /* 0 for now, can be increased when further fields are added to
      struct _Unwind_Context.  */
@@ -1185,6 +1187,11 @@ execute_cfa_program (const unsigned char *insn_ptr,
 	  break;
 
 	case DW_CFA_GNU_window_save:
+#ifdef __aarch64__
+	  /* This CFA is multiplexed with Sparc.  On AArch64 it's used to toggle
+	     return address signing status.  */
+	  fs->regs.reg[DWARF_REGNUM_AARCH64_RA_STATE].loc.offset ^= 1;
+#else
 	  /* ??? Hardcoded for SPARC register window configuration.  */
 	  if (__LIBGCC_DWARF_FRAME_REGISTERS__ >= 32)
 	    for (reg = 16; reg < 32; ++reg)
@@ -1192,6 +1199,7 @@ execute_cfa_program (const unsigned char *insn_ptr,
 		fs->regs.reg[reg].how = REG_SAVED_OFFSET;
 		fs->regs.reg[reg].loc.offset = (reg - 16) * sizeof (void *);
 	      }
+#endif
 	  break;
 
 	case DW_CFA_GNU_args_size:
@@ -1513,10 +1521,15 @@ uw_update_context (struct _Unwind_Context *context, _Unwind_FrameState *fs)
        stack frame.  */
     context->ra = 0;
   else
-    /* Compute the return address now, since the return address column
+    {
-       can change from frame to frame.  */
+      /* Compute the return address now, since the return address column
-    context->ra = __builtin_extract_return_addr
+	 can change from frame to frame.  */
-      (_Unwind_GetPtr (context, fs->retaddr_column));
+      context->ra = __builtin_extract_return_addr
+	(_Unwind_GetPtr (context, fs->retaddr_column));
+#ifdef MD_POST_EXTRACT_FRAME_ADDR
+      context->ra = MD_POST_EXTRACT_FRAME_ADDR (context, fs, context->ra);
+#endif
+    }
 }
 
 static void
@@ -1550,6 +1563,9 @@ uw_init_context_1 (struct _Unwind_Context *context,
 		   void *outer_cfa, void *outer_ra)
 {
   void *ra = __builtin_extract_return_addr (__builtin_return_address (0));
+#ifdef MD_POST_EXTRACT_ROOT_ADDR
+  ra = MD_POST_EXTRACT_ROOT_ADDR (ra);
+#endif
   _Unwind_FrameState fs;
   _Unwind_SpTmp sp_slot;
   _Unwind_Reason_Code code;
@@ -1586,6 +1602,9 @@ uw_init_context_1 (struct _Unwind_Context *context,
      initialization context, then we can't see it in the given
      call frame data.  So have the initialization context tell us.  */
   context->ra = __builtin_extract_return_addr (outer_ra);
+#ifdef MD_POST_EXTRACT_ROOT_ADDR
+  context->ra = MD_POST_EXTRACT_ROOT_ADDR (context->ra);
+#endif
 }
 
 static void _Unwind_DebugHook (void *, void *)
@@ -1608,6 +1627,21 @@ _Unwind_DebugHook (void *cfa __attribute__ ((__unused__)),
 #endif
 }
 
+/* Frob exception handler's address kept in TARGET before installing into
+   CURRENT context.  */
+
+static inline void *
+uw_frob_return_addr (struct _Unwind_Context *current
+		     __attribute__ ((__unused__)),
+		     struct _Unwind_Context *target)
+{
+  void *ret_addr = __builtin_frob_return_addr (target->ra);
+#ifdef MD_POST_FROB_EH_HANDLER_ADDR
+  ret_addr = MD_POST_FROB_EH_HANDLER_ADDR (current, target, ret_addr);
+#endif
+  return ret_addr;
+}
+
 /* Install TARGET into CURRENT so that we can return to it.  This is a
    macro because __builtin_eh_return must be invoked in the context of
    our caller.  */
@@ -1616,7 +1650,7 @@ _Unwind_DebugHook (void *cfa __attribute__ ((__unused__)),
   do									\
     {									\
       long offset = uw_install_context_1 ((CURRENT), (TARGET));		\
-      void *handler = __builtin_frob_return_addr ((TARGET)->ra);	\
+      void *handler = uw_frob_return_addr ((CURRENT), (TARGET));	\
       _Unwind_DebugHook ((TARGET)->cfa, handler);			\
       __builtin_eh_return (offset, handler);				\
     }									\