[v2] rs6000: Error on CPUs and ABIs that don't support the ROP, protection insns [PR114759]

Hi Kewen,

Here's the updated patch per your review comments, minus your suggestion
to disable the ROP mask which I mentioned isn't needed in my other reply.

This passed bootstrap and regtesting with no regressions on powerpc64le-linux.
Ok for trunk?

Peter


Changes from v1:
  * Moved checks for invalid targets from rs6000_override_options_after_change
    to rs6000_option_override_internal.


rs6000: Error on CPUs and ABIs that don't support the ROP, protection insns [PR114759]

We currently silently ignore the -mrop-protect option for old CPUs we don't
support with the ROP hash insns, but we throw an error for unsupported ABIs.
This patch treats unsupported CPUs and ABIs similarly by throwing an error
both both.  This matches clang behavior and allows us to simplify our tests
in the code that generates our prologue and epilogue code.

2024-07-15  Peter Bergner  <bergner@linux.ibm.com>

gcc/
	PR target/114759
	* config/rs6000/rs6000.cc (rs6000_option_override_internal): Disallow
	CPUs and ABIs that do no support the ROP protection insns.
	* config/rs6000/rs6000-logue.cc (rs6000_stack_info): Remove now
	unneeded tests.
	(rs6000_emit_prologue): Likewise.
	Remove unneeded gcc_assert.
	(rs6000_emit_epilogue): Likewise.
	* config/rs6000/rs6000.md: Likewise.

gcc/testsuite/
	PR target/114759
	* gcc.target/powerpc/pr114759-3.c: New test.
---
 gcc/config/rs6000/rs6000-logue.cc             | 22 +++++--------------
 gcc/config/rs6000/rs6000.cc                   | 12 ++++++++++
 gcc/config/rs6000/rs6000.md                   |  4 ++--
 gcc/testsuite/gcc.target/powerpc/pr114759-3.c | 19 ++++++++++++++++
 4 files changed, 39 insertions(+), 18 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr114759-3.c

Hi Peter,

on 2024/7/16 06:07, Peter Bergner wrote:
> Hi Kewen,
> 
> Here's the updated patch per your review comments, minus your suggestion
> to disable the ROP mask which I mentioned isn't needed in my other reply.
> 
> This passed bootstrap and regtesting with no regressions on powerpc64le-linux.
> Ok for trunk?

OK for trunk, thanks!

BR,
Kewen

> 
> Peter
> 
> 
> Changes from v1:
>   * Moved checks for invalid targets from rs6000_override_options_after_change
>     to rs6000_option_override_internal.
> 
> 
> rs6000: Error on CPUs and ABIs that don't support the ROP, protection insns [PR114759]
> 
> We currently silently ignore the -mrop-protect option for old CPUs we don't
> support with the ROP hash insns, but we throw an error for unsupported ABIs.
> This patch treats unsupported CPUs and ABIs similarly by throwing an error
> both both.  This matches clang behavior and allows us to simplify our tests
> in the code that generates our prologue and epilogue code.
> 
> 2024-07-15  Peter Bergner  <bergner@linux.ibm.com>
> 
> gcc/
> 	PR target/114759
> 	* config/rs6000/rs6000.cc (rs6000_option_override_internal): Disallow
> 	CPUs and ABIs that do no support the ROP protection insns.
> 	* config/rs6000/rs6000-logue.cc (rs6000_stack_info): Remove now
> 	unneeded tests.
> 	(rs6000_emit_prologue): Likewise.
> 	Remove unneeded gcc_assert.
> 	(rs6000_emit_epilogue): Likewise.
> 	* config/rs6000/rs6000.md: Likewise.
> 
> gcc/testsuite/
> 	PR target/114759
> 	* gcc.target/powerpc/pr114759-3.c: New test.
> ---
>  gcc/config/rs6000/rs6000-logue.cc             | 22 +++++--------------
>  gcc/config/rs6000/rs6000.cc                   | 12 ++++++++++
>  gcc/config/rs6000/rs6000.md                   |  4 ++--
>  gcc/testsuite/gcc.target/powerpc/pr114759-3.c | 19 ++++++++++++++++
>  4 files changed, 39 insertions(+), 18 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr114759-3.c
> 
> diff --git a/gcc/config/rs6000/rs6000-logue.cc b/gcc/config/rs6000/rs6000-logue.cc
> index bd363b625a4..fdb6414f486 100644
> --- a/gcc/config/rs6000/rs6000-logue.cc
> +++ b/gcc/config/rs6000/rs6000-logue.cc
> @@ -716,17 +716,11 @@ rs6000_stack_info (void)
>    info->calls_p = (!crtl->is_leaf || cfun->machine->ra_needs_full_frame);
>    info->rop_hash_size = 0;
>  
> -  if (TARGET_POWER8
> -      && info->calls_p
> -      && DEFAULT_ABI == ABI_ELFv2
> -      && rs6000_rop_protect)
> +  /* If we want ROP protection and this function makes a call, indicate
> +     we need to create a stack slot to save the hashed return address in.  */
> +  if (rs6000_rop_protect
> +      && info->calls_p)
>      info->rop_hash_size = 8;
> -  else if (rs6000_rop_protect && DEFAULT_ABI != ABI_ELFv2)
> -    {
> -      /* We can't check this in rs6000_option_override_internal since
> -	 DEFAULT_ABI isn't established yet.  */
> -      error ("%qs requires the ELFv2 ABI", "-mrop-protect");
> -    }
>  
>    /* Determine if we need to save the condition code registers.  */
>    if (save_reg_p (CR2_REGNO)
> @@ -3277,9 +3271,8 @@ rs6000_emit_prologue (void)
>    /* NOTE: The hashst isn't needed if we're going to do a sibcall,
>       but there's no way to know that here.  Harmless except for
>       performance, of course.  */
> -  if (TARGET_POWER8 && rs6000_rop_protect && info->rop_hash_size != 0)
> +  if (info->rop_hash_size)
>      {
> -      gcc_assert (DEFAULT_ABI == ABI_ELFv2);
>        rtx stack_ptr = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
>        rtx addr = gen_rtx_PLUS (Pmode, stack_ptr,
>  			       GEN_INT (info->rop_hash_save_offset));
> @@ -5056,12 +5049,9 @@ rs6000_emit_epilogue (enum epilogue_type epilogue_type)
>  
>    /* The ROP hash check must occur after the stack pointer is restored
>       (since the hash involves r1), and is not performed for a sibcall.  */
> -  if (TARGET_POWER8
> -      && rs6000_rop_protect
> -      && info->rop_hash_size != 0
> +  if (info->rop_hash_size
>        && epilogue_type != EPILOGUE_TYPE_SIBCALL)
>      {
> -      gcc_assert (DEFAULT_ABI == ABI_ELFv2);
>        rtx stack_ptr = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
>        rtx addr = gen_rtx_PLUS (Pmode, stack_ptr,
>  			       GEN_INT (info->rop_hash_save_offset));
> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
> index fd6e013c346..1cee9c2011d 100644
> --- a/gcc/config/rs6000/rs6000.cc
> +++ b/gcc/config/rs6000/rs6000.cc
> @@ -4825,6 +4825,18 @@ rs6000_option_override_internal (bool global_init_p)
>  	}
>      }
>  
> +  /* We only support ROP protection on certain targets.  */
> +  if (rs6000_rop_protect)
> +    {
> +      /* Disallow CPU targets we don't support.  */
> +      if (!TARGET_POWER8)
> +	error ("%<-mrop-protect%> requires %<-mcpu=power8%> or later");
> +
> +      /* Disallow ABI targets we don't support.  */
> +      if (DEFAULT_ABI != ABI_ELFv2)
> +	error ("%<-mrop-protect%> requires the ELFv2 ABI");
> +    }
> +
>    /* Initialize all of the registers.  */
>    rs6000_init_hard_regno_mode_ok (global_init_p);
>  
> diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
> index 694076e311f..75fe51b8d43 100644
> --- a/gcc/config/rs6000/rs6000.md
> +++ b/gcc/config/rs6000/rs6000.md
> @@ -15810,7 +15810,7 @@ (define_insn "hashst"
>    [(set (match_operand:DI 0 "simple_offsettable_mem_operand" "=m")
>  	(unspec_volatile:DI [(match_operand:DI 1 "int_reg_operand" "r")]
>  			    UNSPEC_HASHST))]
> -  "TARGET_POWER8 && rs6000_rop_protect"
> +  "rs6000_rop_protect"
>  {
>    static char templ[32];
>    const char *p = rs6000_privileged ? "p" : "";
> @@ -15823,7 +15823,7 @@ (define_insn "hashchk"
>    [(unspec_volatile [(match_operand:DI 0 "int_reg_operand" "r")
>  		     (match_operand:DI 1 "simple_offsettable_mem_operand" "m")]
>  		    UNSPEC_HASHCHK)]
> -  "TARGET_POWER8 && rs6000_rop_protect"
> +  "rs6000_rop_protect"
>  {
>    static char templ[32];
>    const char *p = rs6000_privileged ? "p" : "";
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr114759-3.c b/gcc/testsuite/gcc.target/powerpc/pr114759-3.c
> new file mode 100644
> index 00000000000..6770a9aec3b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr114759-3.c
> @@ -0,0 +1,19 @@
> +/* PR target/114759 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -mdejagnu-cpu=power7 -mrop-protect" } */
> +
> +/* Verify we emit an error if we use -mrop-protect with an unsupported cpu.  */
> +
> +extern void foo (void);
> +
> +int
> +bar (void)
> +{
> +  foo ();
> +  return 5;
> +}
> +
> +/* The correct line number is in the preamble to the error message, not
> +   in the final line (which is all that dg-error inspects). Hence, we have
> +   to tell dg-error to ignore the line number.  */
> +/* { dg-error "'-mrop-protect' requires '-mcpu=power8'" "PR114759" { target *-*-* } 0 } */