[11/12] aarch64: Make bti pass generic so it can be used by the arm backend

  Hi all,

this patch splits and restructures the aarch64 bti pass code in order
to have it usable by the arm backend as well.  These changes have no
functional impact.

Best Regards

  Andrea

gcc/Changelog

	* config.gcc (aarch64*-*-*): Rename 'aarch64-bti-insert.o' into
	'aarch-bti-insert.o'.
	* config/aarch64/aarch64-protos.h: Remove 'aarch64_bti_enabled'
	proto.
	* config/aarch64/aarch64.cc (aarch_bti_enabled): Rename.
	(aarch_bti_j_insn_p, aarch_pac_insn_p): New functions.
	(aarch64_output_mi_thunk)
	(aarch64_print_patchable_function_entry)
	(aarch64_file_end_indicate_exec_stack): Update renamed function
	calls to renamed functions.
	* config/aarch64/t-aarch64 (aarch-bti-insert.o): Update target.
	* config/arm/aarch-bti-insert.cc: New file including and
	generalizing code from aarch64-bti-insert.cc.
	* config/arm/aarch-common-protos.h: Update.
	* config/arm/arm-passes.def: New file.
  

Andrea Corallo via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> Hi all,
>
> this patch splits and restructures the aarch64 bti pass code in order
> to have it usable by the arm backend as well.  These changes have no
> functional impact.
>
> Best Regards
>
>   Andrea
>
> gcc/Changelog
>
> 	* config.gcc (aarch64*-*-*): Rename 'aarch64-bti-insert.o' into
> 	'aarch-bti-insert.o'.
> 	* config/aarch64/aarch64-protos.h: Remove 'aarch64_bti_enabled'
> 	proto.
> 	* config/aarch64/aarch64.cc (aarch_bti_enabled): Rename.
> 	(aarch_bti_j_insn_p, aarch_pac_insn_p): New functions.
> 	(aarch64_output_mi_thunk)
> 	(aarch64_print_patchable_function_entry)
> 	(aarch64_file_end_indicate_exec_stack): Update renamed function
> 	calls to renamed functions.
> 	* config/aarch64/t-aarch64 (aarch-bti-insert.o): Update target.
> 	* config/arm/aarch-bti-insert.cc: New file including and
> 	generalizing code from aarch64-bti-insert.cc.
> 	* config/arm/aarch-common-protos.h: Update.
> 	* config/arm/arm-passes.def: New file.

Looks good to me, thanks.

Richard

> diff --git a/gcc/config.gcc b/gcc/config.gcc
> index 7b58e1314ff..2021bdf9d2f 100644
> --- a/gcc/config.gcc
> +++ b/gcc/config.gcc
> @@ -329,7 +329,7 @@ aarch64*-*-*)
>  	c_target_objs="aarch64-c.o"
>  	cxx_target_objs="aarch64-c.o"
>  	d_target_objs="aarch64-d.o"
> -	extra_objs="aarch64-builtins.o aarch-common.o aarch64-sve-builtins.o aarch64-sve-builtins-shapes.o aarch64-sve-builtins-base.o aarch64-sve-builtins-sve2.o cortex-a57-fma-steering.o aarch64-speculation.o falkor-tag-collision-avoidance.o aarch64-bti-insert.o aarch64-cc-fusion.o"
> +	extra_objs="aarch64-builtins.o aarch-common.o aarch64-sve-builtins.o aarch64-sve-builtins-shapes.o aarch64-sve-builtins-base.o aarch64-sve-builtins-sve2.o cortex-a57-fma-steering.o aarch64-speculation.o falkor-tag-collision-avoidance.o aarch-bti-insert.o aarch64-cc-fusion.o"
>  	target_gtfiles="\$(srcdir)/config/aarch64/aarch64-builtins.cc \$(srcdir)/config/aarch64/aarch64-sve-builtins.h \$(srcdir)/config/aarch64/aarch64-sve-builtins.cc"
>  	target_has_targetm_common=yes
>  	;;
> diff --git a/gcc/config/aarch64/aarch64-c.cc b/gcc/config/aarch64/aarch64-c.cc
> index b0c5a4fd6b6..a9aad3abdc2 100644
> --- a/gcc/config/aarch64/aarch64-c.cc
> +++ b/gcc/config/aarch64/aarch64-c.cc
> @@ -179,7 +179,7 @@ aarch64_update_cpp_builtins (cpp_reader *pfile)
>    aarch64_def_or_undef (TARGET_RNG, "__ARM_FEATURE_RNG", pfile);
>    aarch64_def_or_undef (TARGET_MEMTAG, "__ARM_FEATURE_MEMORY_TAGGING", pfile);
>  
> -  aarch64_def_or_undef (aarch64_bti_enabled (),
> +  aarch64_def_or_undef (aarch_bti_enabled (),
>  			"__ARM_FEATURE_BTI_DEFAULT", pfile);
>  
>    cpp_undef (pfile, "__ARM_FEATURE_PAC_DEFAULT");
> diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
> index fe2180e95ea..9fdf7f9cc9c 100644
> --- a/gcc/config/aarch64/aarch64-protos.h
> +++ b/gcc/config/aarch64/aarch64-protos.h
> @@ -891,7 +891,6 @@ void aarch64_register_pragmas (void);
>  void aarch64_relayout_simd_types (void);
>  void aarch64_reset_previous_fndecl (void);
>  bool aarch64_return_address_signing_enabled (void);
> -bool aarch64_bti_enabled (void);
>  void aarch64_save_restore_target_globals (tree);
>  void aarch64_addti_scratch_regs (rtx, rtx, rtx *,
>  				 rtx *, rtx *,
> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> index eec743024c1..2f67f3872f6 100644
> --- a/gcc/config/aarch64/aarch64.cc
> +++ b/gcc/config/aarch64/aarch64.cc
> @@ -8534,11 +8534,61 @@ aarch64_return_address_signing_enabled (void)
>  
>  /* Return TRUE if Branch Target Identification Mechanism is enabled.  */
>  bool
> -aarch64_bti_enabled (void)
> +aarch_bti_enabled (void)
>  {
>    return (aarch_enable_bti == 1);
>  }
>  
> +/* Check if INSN is a BTI J insn.  */
> +bool
> +aarch_bti_j_insn_p (rtx_insn *insn)
> +{
> +  if (!insn || !INSN_P (insn))
> +    return false;
> +
> +  rtx pat = PATTERN (insn);
> +  return GET_CODE (pat) == UNSPEC_VOLATILE && XINT (pat, 1) == UNSPECV_BTI_J;
> +}
> +
> +/* Check if X (or any sub-rtx of X) is a PACIASP/PACIBSP instruction.  */
> +bool
> +aarch_pac_insn_p (rtx x)
> +{
> +  if (!INSN_P (x))
> +    return false;
> +
> +  subrtx_var_iterator::array_type array;
> +  FOR_EACH_SUBRTX_VAR (iter, array, PATTERN (x), ALL)
> +    {
> +      rtx sub = *iter;
> +      if (sub && GET_CODE (sub) == UNSPEC)
> +	{
> +	  int unspec_val = XINT (sub, 1);
> +	  switch (unspec_val)
> +	    {
> +	    case UNSPEC_PACIASP:
> +            case UNSPEC_PACIBSP:
> +	      return true;
> +
> +	    default:
> +	      return false;
> +	    }
> +	  iter.skip_subrtxes ();
> +	}
> +    }
> +  return false;
> +}
> +
> +rtx aarch_gen_bti_c (void)
> +{
> +  return gen_bti_c ();
> +}
> +
> +rtx aarch_gen_bti_j (void)
> +{
> +  return gen_bti_j ();
> +}
> +
>  /* The caller is going to use ST1D or LD1D to save or restore an SVE
>     register in mode MODE at BASE_RTX + OFFSET, where OFFSET is in
>     the range [1, 16] * GET_MODE_SIZE (MODE).  Prepare for this by:
> @@ -9918,7 +9968,7 @@ aarch64_output_mi_thunk (FILE *file, tree thunk ATTRIBUTE_UNUSED,
>    rtx_insn *insn;
>    const char *fnname = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (thunk));
>  
> -  if (aarch64_bti_enabled ())
> +  if (aarch_bti_enabled ())
>      emit_insn (gen_bti_c());
>  
>    reload_completed = 1;
> @@ -22360,7 +22410,7 @@ aarch64_print_patchable_function_entry (FILE *file,
>  					bool record_p)
>  {
>    if (cfun->machine->label_is_assembled
> -      && aarch64_bti_enabled ()
> +      && aarch_bti_enabled ()
>        && !cgraph_node::get (cfun->decl)->only_called_directly_p ())
>      {
>        /* Remove the BTI that follows the patch area and insert a new BTI
> @@ -26689,7 +26739,7 @@ aarch64_file_end_indicate_exec_stack ()
>    file_end_indicate_exec_stack ();
>  
>    unsigned feature_1_and = 0;
> -  if (aarch64_bti_enabled ())
> +  if (aarch_bti_enabled ())
>      feature_1_and |= GNU_PROPERTY_AARCH64_FEATURE_1_BTI;
>  
>    if (aarch_ra_sign_scope != AARCH_FUNCTION_NONE)
> diff --git a/gcc/config/aarch64/t-aarch64 b/gcc/config/aarch64/t-aarch64
> index 75b463d2f03..eb6ad3db955 100644
> --- a/gcc/config/aarch64/t-aarch64
> +++ b/gcc/config/aarch64/t-aarch64
> @@ -149,14 +149,14 @@ falkor-tag-collision-avoidance.o: \
>  	$(COMPILER) -c $(ALL_COMPILERFLAGS) $(ALL_CPPFLAGS) $(INCLUDES) \
>  		$(srcdir)/config/aarch64/falkor-tag-collision-avoidance.cc
>  
> -aarch64-bti-insert.o: $(srcdir)/config/aarch64/aarch64-bti-insert.cc \
> +aarch-bti-insert.o: $(srcdir)/config/arm/aarch-bti-insert.cc \
>      $(CONFIG_H) $(SYSTEM_H) $(TM_H) $(REGS_H) insn-config.h $(RTL_BASE_H) \
>      dominance.h cfg.h cfganal.h $(BASIC_BLOCK_H) $(INSN_ATTR_H) $(RECOG_H) \
>      output.h hash-map.h $(DF_H) $(OBSTACK_H) $(TARGET_H) $(RTL_H) \
>      $(CONTEXT_H) $(TREE_PASS_H) regrename.h \
>      $(srcdir)/config/aarch64/aarch64-protos.h
>  	$(COMPILER) -c $(ALL_COMPILERFLAGS) $(ALL_CPPFLAGS) $(INCLUDES) \
> -		$(srcdir)/config/aarch64/aarch64-bti-insert.cc
> +		$(srcdir)/config/arm/aarch-bti-insert.cc
>  
>  aarch64-cc-fusion.o: $(srcdir)/config/aarch64/aarch64-cc-fusion.cc \
>      $(CONFIG_H) $(SYSTEM_H) $(CORETYPES_H) $(BACKEND_H) $(RTL_H) $(DF_H) \
> diff --git a/gcc/config/aarch64/aarch64-bti-insert.cc b/gcc/config/arm/aarch-bti-insert.cc
> similarity index 80%
> rename from gcc/config/aarch64/aarch64-bti-insert.cc
> rename to gcc/config/arm/aarch-bti-insert.cc
> index 7caed310bbc..2d1d2e334a9 100644
> --- a/gcc/config/aarch64/aarch64-bti-insert.cc
> +++ b/gcc/config/arm/aarch-bti-insert.cc
> @@ -42,10 +42,11 @@
>  #include "tree-pass.h"
>  #include "cgraph.h"
>  
> -/* This pass enables the support for Branch Target Identification Mechanism
> -   for AArch64.  This is a new security feature introduced in ARMv8.5-A
> -   archtitecture.  A BTI instruction is used to guard against the execution
> -   of instructions which are not the intended target of an indirect branch.
> +/* This pass enables the support for Branch Target Identification Mechanism for
> +   Arm/AArch64.  This is a security feature introduced in ARMv8.5-A
> +   architecture and ARMv8.1-M.  A BTI instruction is used to guard against the
> +   execution of instructions which are not the intended target of an indirect
> +   branch.
>  
>     Outside of a guarded memory region, a BTI instruction executes as a NOP.
>     Within a guarded memory region any target of an indirect branch must be
> @@ -53,7 +54,8 @@
>     branch is triggered in a non-guarded memory region).  An incompatibility
>     generates a Branch Target Exception.
>  
> -   The compatibility of the BTI instruction is as follows:
> +   The compatibility of the BTI instruction is as follows (AArch64
> +   examples):
>     BTI j : Can be a target of any indirect jump (BR Xn).
>     BTI c : Can be a target of any indirect call (BLR Xn and BR X16/X17).
>     BTI jc: Can be a target of any indirect call or indirect jump.
> @@ -90,47 +92,6 @@ const pass_data pass_data_insert_bti =
>    0, /* todo_flags_finish.  */
>  };
>  
> -/* Check if X (or any sub-rtx of X) is a PACIASP/PACIBSP instruction.  */
> -static bool
> -aarch64_pac_insn_p (rtx x)
> -{
> -  if (!INSN_P (x))
> -    return false;
> -
> -  subrtx_var_iterator::array_type array;
> -  FOR_EACH_SUBRTX_VAR (iter, array, PATTERN (x), ALL)
> -    {
> -      rtx sub = *iter;
> -      if (sub && GET_CODE (sub) == UNSPEC)
> -	{
> -	  int unspec_val = XINT (sub, 1);
> -	  switch (unspec_val)
> -	    {
> -	    case UNSPEC_PACIASP:
> -            /* fall-through.  */
> -            case UNSPEC_PACIBSP:
> -	      return true;
> -
> -	    default:
> -	      return false;
> -	    }
> -	  iter.skip_subrtxes ();
> -	}
> -    }
> -  return false;
> -}
> -
> -/* Check if INSN is a BTI J insn.  */
> -static bool
> -aarch64_bti_j_insn_p (rtx_insn *insn)
> -{
> -  if (!insn || !INSN_P (insn))
> -    return false;
> -
> -  rtx pat = PATTERN (insn);
> -  return GET_CODE (pat) == UNSPEC_VOLATILE && XINT (pat, 1) == UNSPECV_BTI_J;
> -}
> -
>  /* Insert the BTI instruction.  */
>  /* This is implemented as a late RTL pass that runs before branch
>     shortening and does the following.  */
> @@ -155,7 +116,7 @@ rest_of_insert_bti (void)
>  	       && (LABEL_PRESERVE_P (insn)
>  		   || bb->flags & BB_NON_LOCAL_GOTO_TARGET))
>  	    {
> -	      bti_insn = gen_bti_j ();
> +	      bti_insn = aarch_gen_bti_j ();
>  	      emit_insn_after (bti_insn, insn);
>  	      continue;
>  	    }
> @@ -177,10 +138,10 @@ rest_of_insert_bti (void)
>  		    {
>  		      label = as_a <rtx_insn *> (XEXP (RTVEC_ELT (vec, j), 0));
>  		      rtx_insn *next = next_nonnote_nondebug_insn (label);
> -		      if (aarch64_bti_j_insn_p (next))
> +		      if (aarch_bti_j_insn_p (next))
>  			continue;
>  
> -		      bti_insn = gen_bti_j ();
> +		      bti_insn = aarch_gen_bti_j ();
>  		      emit_insn_after (bti_insn, label);
>  		    }
>  		}
> @@ -191,7 +152,7 @@ rest_of_insert_bti (void)
>  	     will return.  */
>  	  if (CALL_P (insn) && (find_reg_note (insn, REG_SETJMP, NULL)))
>  	    {
> -	      bti_insn = gen_bti_j ();
> +	      bti_insn = aarch_gen_bti_j ();
>  	      emit_insn_after (bti_insn, insn);
>  	      continue;
>  	    }
> @@ -207,9 +168,9 @@ rest_of_insert_bti (void)
>      {
>        bb = ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb;
>        insn = BB_HEAD (bb);
> -      if (!aarch64_pac_insn_p (get_first_nonnote_insn ()))
> +      if (!aarch_pac_insn_p (get_first_nonnote_insn ()))
>  	{
> -	  bti_insn = gen_bti_c ();
> +	  bti_insn = aarch_gen_bti_c ();
>  	  emit_insn_before (bti_insn, insn);
>  	}
>      }
> @@ -229,7 +190,7 @@ public:
>    /* opt_pass methods: */
>    virtual bool gate (function *)
>      {
> -      return aarch64_bti_enabled ();
> +      return aarch_bti_enabled ();
>      }
>  
>    virtual unsigned int execute (function *)
> diff --git a/gcc/config/arm/aarch-common-protos.h b/gcc/config/arm/aarch-common-protos.h
> index 17a369f7e99..374982752ad 100644
> --- a/gcc/config/arm/aarch-common-protos.h
> +++ b/gcc/config/arm/aarch-common-protos.h
> @@ -42,6 +42,11 @@ extern int arm_no_early_alu_shift_value_dep (rtx, rtx);
>  extern int arm_no_early_mul_dep (rtx, rtx);
>  extern int arm_no_early_store_addr_dep (rtx, rtx);
>  extern bool arm_rtx_shift_left_p (rtx);
> +extern bool aarch_bti_enabled (void);
> +extern bool aarch_bti_j_insn_p (rtx_insn *);
> +extern bool aarch_pac_insn_p (rtx);
> +extern rtx aarch_gen_bti_c (void);
> +extern rtx aarch_gen_bti_j (void);
>  
>  /* RTX cost table definitions.  These are used when tuning for speed rather
>     than for size and should reflect the _additional_ cost over the cost
> diff --git a/gcc/config/arm/arm-passes.def b/gcc/config/arm/arm-passes.def
> new file mode 100644
> index 00000000000..beecd2b5455
> --- /dev/null
> +++ b/gcc/config/arm/arm-passes.def
> @@ -0,0 +1,21 @@
> +/* Arm-specific passes declarations.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   Contributed by Arm Ltd.
> +
> +   This file is part of GCC.
> +
> +   GCC is free software; you can redistribute it and/or modify it
> +   under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3, or (at your option)
> +   any later version.
> +
> +   GCC is distributed in the hope that it will be useful, but
> +   WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with GCC; see the file COPYING3.  If not see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +INSERT_PASS_BEFORE (pass_shorten_branches, 1, pass_insert_bti);
  

On 28/04/2022 10:51, Andrea Corallo via Gcc-patches wrote:
> Hi all,
> 
> this patch splits and restructures the aarch64 bti pass code in order
> to have it usable by the arm backend as well.  These changes have no
> functional impact.
> 
> Best Regards
> 
>    Andrea
> 
> gcc/Changelog
> 
> 	* config.gcc (aarch64*-*-*): Rename 'aarch64-bti-insert.o' into
> 	'aarch-bti-insert.o'.
> 	* config/aarch64/aarch64-protos.h: Remove 'aarch64_bti_enabled'
> 	proto.
> 	* config/aarch64/aarch64.cc (aarch_bti_enabled): Rename.
> 	(aarch_bti_j_insn_p, aarch_pac_insn_p): New functions.
> 	(aarch64_output_mi_thunk)
> 	(aarch64_print_patchable_function_entry)
> 	(aarch64_file_end_indicate_exec_stack): Update renamed function
> 	calls to renamed functions.
> 	* config/aarch64/t-aarch64 (aarch-bti-insert.o): Update target.
> 	* config/arm/aarch-bti-insert.cc: New file including and
> 	generalizing code from aarch64-bti-insert.cc.
> 	* config/arm/aarch-common-protos.h: Update.
> 	* config/arm/arm-passes.def: New file.
> 

Is this patch fully stand-alone?  It adds arm-passes.def, which adds a 
reference to pass_insert_bti, but that isn't fully wired up until the 
next patch.

R.