[3/7,ARM,V8M] ARMv8-M Security Extension's cmse_nonsecure_entry: __acle_se label and bxns return

On 26/10/16 11:03, Kyrill Tkachov wrote:
> Hi Andre,
> 
> On 25/10/16 17:28, Andre Vieira (lists) wrote:
>> On 25/07/16 14:23, Andre Vieira (lists) wrote:
>>> This patch extends support for the ARMv8-M Security Extensions
>>> 'cmse_nonsecure_entry' attribute in two ways:
>>>
>>> 1) Generate two labels for the function, the regular function name and
>>> one with the function's name appended to '__acle_se_', this will trigger
>>> the linker to create a secure gateway veneer for this entry function.
>>> 2) Return from cmse_nonsecure_entry marked functions using bxns.
>>>
>>> See Section 5.4 of ARM®v8-M Security Extensions
>>> (http://infocenter.arm.com/help/topic/com.arm.doc.ecm0359818/index.html).
>>>
>>>
>>>
>>> *** gcc/ChangeLog ***
>>> 2016-07-25  Andre Vieira        <andre.simoesdiasvieira@arm.com>
>>>              Thomas Preud'homme  <thomas.preudhomme@arm.com>
>>>
>>>          * config/arm/arm.c (use_return_insn): Change to return with 
>>> bxns
>>>          when cmse_nonsecure_entry.
>>>          (output_return_instruction): Likewise.
>>>          (arm_output_function_prologue): Likewise.
>>>          (thumb_pop): Likewise.
>>>          (thumb_exit): Likewise.
>>>          (arm_function_ok_for_sibcall): Disable sibcall for entry
>>> functions.
>>>          (arm_asm_declare_function_name): New.
>>>          * config/arm/arm-protos.h (arm_asm_declare_function_name): New.
>>>          * config/arm/elf.h (ASM_DECLARE_FUNCTION_NAME): Redefine to
>>>          use arm_asm_declare_function_name.
>>>
>>> *** gcc/testsuite/ChangeLog ***
>>> 2016-07-25  Andre Vieira        <andre.simoesdiasvieira@arm.com>
>>>              Thomas Preud'homme  <thomas.preudhomme@arm.com>
>>>
>>>          * gcc.target/arm/cmse/cmse-2.c: New.
>>>          * gcc.target/arm/cmse/cmse-4.c: New.
>>>
>> Hi,
>>
>> Rebased previous patch on top of trunk as requested. No changes to
>> ChangeLog.
>>
>> Cheers,
>> Andre
> 
> @@ -19919,6 +19932,42 @@ output_return_instruction (rtx operand, bool
> really_return, bool reverse,
>    return "";
>  }
>  
> +/* Output in FILE asm statements needed to declare the NAME of the
> function
> +   defined by its DECL node.  */
> +
> +void
> +arm_asm_declare_function_name (FILE *file, const char *name, tree decl)
> +{
> +  size_t cmse_name_len;
> +  char *cmse_name = 0;
> +  char cmse_prefix[] = "__acle_se_";
> +
> +  if (use_cmse && lookup_attribute ("cmse_nonsecure_entry",
> +                    DECL_ATTRIBUTES (decl)))
> +    {
> +      cmse_name_len = sizeof (cmse_prefix) + strlen (name);
> +      cmse_name = XALLOCAVEC (char, cmse_name_len);
> +      snprintf (cmse_name, cmse_name_len, "%s%s", cmse_prefix, name);
> +      targetm.asm_out.globalize_label (file, cmse_name);
> +    }
> +
> 
> I think this definitely warrants a quick comment explaining why you're
> adding
> __acle_se_ to the function label
> 
>  
>  /* Scan INSN just before assembler is output for it.
> @@ -25247,6 +25301,12 @@ thumb2_expand_return (bool simple_return)
>  
>    if (!simple_return && saved_regs_mask)
>      {
> +      /* TODO: Verify that this path is never taken for
> cmse_nonsecure_entry
> +     functions or adapt code to handle according to ACLE.  This path
> should
> +     not be reachable for cmse_nonsecure_entry functions though we prefer
> +     to guard it for now to ensure that future code changes do not
> silently
> +     change this behavior.  */
> 
> I think you mean s/guard/assert/
> 
>  +      gcc_assert (!IS_CMSE_ENTRY (arm_current_func_type ()));
>        if (num_regs == 1)
>          {
>            rtx par = gen_rtx_PARALLEL (VOIDmode, rtvec_alloc (2));
> 
> This is ok with those changes.
> Thanks,
> Kyrill
> 
Hi,

Reworked comments. Also got rid of a redundant 'if (cmse_name)' in
'arm_asm_declare_function_name'. No change to ChangeLogs.

Cheers,
Andre

[3/7,ARM,V8M] ARMv8-M Security Extension's cmse_nonsecure_entry: __acle_se label and bxns return

Commit Message

Patch