This is the mail archive of the gdb-patches@sourceware.org mailing list for the GDB project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[PING][PATCH] AArch64: Prevent infinite recursion when checking AAPCS types


Ping.

> On 12 Dec 2018, at 09:59, Alan Hayward <Alan.Hayward@arm.com> wrote:
> 
> gdb.dwarf2/dw2-cp-infcall-ref-static.exp includes a struct which
> contains itself.  Add support to aapcs_is_vfp_call_or_return_candidate to
> prevent infinite recursion.
> 
> The simple solution is to pass a counter through the functions and abort once
> the max limit is reached.  However, this does not catch the case where a
> struct only contains itself and no other members.  That can be solved by
> marking a type as invalid before checking all of it's children.
> 
> Add a count for the call or ret candidate to main_type, restricted to 3
> bits - the value 5 (or above) is used as invalid.
> 
> This code is testsed by both gdb.base/infcall-nested-structs.exp
> and gdb.dwarf2/dw2-cp-infcall-ref-static.exp.
> 
> gdb/ChangeLog:
> 
> 2018-12-12  Alan Hayward  <alan.hayward@arm.com>
> 
> 	* aarch64-tdep.c (HA_MAX_NUM_FLDS): Remove define.
> 	(aapcs_is_vfp_call_or_return_candidate_1): Remember type.
> 	(aapcs_is_vfp_call_or_return_candidate): Likewise.
> 	* gdbtypes.h (AAPCS_VFP_CALL_OR_RET_CAND_MAX): Add define.
> 	(AAPCS_VFP_CALL_OR_RET_CAND_INVALID): Likewise.
> 	(TYPE_AAPCS_VFP_CALL_OR_RET_CANDIDATE): Likewise.
> 	(TYPE_SET_AAPCS_VFP_CALL_OR_RET_CANDIDATE): Likewise.
> 	(struct main_type): Add aapcs_candidate_count.
> ---
> gdb/aarch64-tdep.c | 87 ++++++++++++++++++++++++++--------------------
> gdb/gdbtypes.h     | 23 ++++++++++++
> 2 files changed, 72 insertions(+), 38 deletions(-)
> 
> diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
> index ae56c9ca34..3fc58308d6 100644
> --- a/gdb/aarch64-tdep.c
> +++ b/gdb/aarch64-tdep.c
> @@ -64,10 +64,6 @@
> #define bit(obj,st) (((obj) >> (st)) & 1)
> #define bits(obj,st,fn) (((obj) >> (st)) & submask ((fn) - (st)))
> 
> -/* A Homogeneous Floating-Point or Short-Vector Aggregate may have at most
> -   four members.  */
> -#define HA_MAX_NUM_FLDS		4
> -
> /* All possible aarch64 target descriptors.  */
> struct target_desc *tdesc_aarch64_list[AARCH64_MAX_SVE_VQ + 1];
> 
> @@ -1146,46 +1142,58 @@ aarch64_type_align (struct type *t)
> 
> /* Worker function for aapcs_is_vfp_call_or_return_candidate.
> 
> -   Return the number of register required, or -1 on failure.
> +   Set TYPE_AAPCS_VFP_CALL_OR_RET_CANDIDATE to the number of registers required,
> +   or AAPCS_VFP_CALL_OR_RET_CAND_INVALID on failure.
> 
>    When encountering a base element, if FUNDAMENTAL_TYPE is not set then set it
>    to the element, else fail if the type of this element does not match the
>    existing value.  */
> 
> -static int
> +static void
> aapcs_is_vfp_call_or_return_candidate_1 (struct type *type,
> 					 struct type **fundamental_type)
> {
>   if (type == nullptr)
> -    return -1;
> +    return;
> +
> +  /* Check if we have already evaluated this TYPE.  */
> +  if (TYPE_AAPCS_VFP_CALL_OR_RET_CANDIDATE (type)
> +      >= AAPCS_VFP_CALL_OR_RET_CAND_INVALID)
> +    return;
> +
> +  /* Set TYPE to invalid to prevent infinite recursion.  */
> +  TYPE_SET_AAPCS_VFP_CALL_OR_RET_CANDIDATE (type,
> +					    AAPCS_VFP_CALL_OR_RET_CAND_INVALID);
> 
>   switch (TYPE_CODE (type))
>     {
>     case TYPE_CODE_FLT:
>       if (TYPE_LENGTH (type) > 16)
> -	return -1;
> +	return;
> 
>       if (*fundamental_type == nullptr)
> 	*fundamental_type = type;
>       else if (TYPE_LENGTH (type) != TYPE_LENGTH (*fundamental_type)
> 	       || TYPE_CODE (type) != TYPE_CODE (*fundamental_type))
> -	return -1;
> +	return;
> 
> -      return 1;
> +      TYPE_SET_AAPCS_VFP_CALL_OR_RET_CANDIDATE (type, 1);
> +      return;
> 
>     case TYPE_CODE_COMPLEX:
>       {
> 	struct type *target_type = check_typedef (TYPE_TARGET_TYPE (type));
> 	if (TYPE_LENGTH (target_type) > 16)
> -	  return -1;
> +	  return;
> 
> 	if (*fundamental_type == nullptr)
> 	  *fundamental_type = target_type;
> 	else if (TYPE_LENGTH (target_type) != TYPE_LENGTH (*fundamental_type)
> 		 || TYPE_CODE (target_type) != TYPE_CODE (*fundamental_type))
> -	  return -1;
> +	  return;
> 
> -	return 2;
> +	TYPE_SET_AAPCS_VFP_CALL_OR_RET_CANDIDATE (type, 2);
> +	return;
>       }
> 
>     case TYPE_CODE_ARRAY:
> @@ -1193,28 +1201,33 @@ aapcs_is_vfp_call_or_return_candidate_1 (struct type *type,
> 	if (TYPE_VECTOR (type))
> 	  {
> 	    if (TYPE_LENGTH (type) != 8 && TYPE_LENGTH (type) != 16)
> -	      return -1;
> +	      return;
> 
> 	    if (*fundamental_type == nullptr)
> 	      *fundamental_type = type;
> 	    else if (TYPE_LENGTH (type) != TYPE_LENGTH (*fundamental_type)
> 		     || TYPE_CODE (type) != TYPE_CODE (*fundamental_type))
> -	      return -1;
> +	      return;
> 
> -	    return 1;
> +	    TYPE_SET_AAPCS_VFP_CALL_OR_RET_CANDIDATE (type, 1);
> 	  }
> 	else
> 	  {
> +	    /* Calculate if type of an element in the array is valid.  */
> 	    struct type *target_type = TYPE_TARGET_TYPE (type);
> -	    int count = aapcs_is_vfp_call_or_return_candidate_1
> -			  (target_type, fundamental_type);
> +	    aapcs_is_vfp_call_or_return_candidate_1 (target_type,
> +						     fundamental_type);
> 
> -	    if (count == -1)
> -	      return count;
> +	    int count = TYPE_AAPCS_VFP_CALL_OR_RET_CANDIDATE (target_type);
> +	    if (count >= AAPCS_VFP_CALL_OR_RET_CAND_INVALID)
> +	      return;
> +
> +	    /* Expand to cover the whole array.  The set handles overflow.  */
> 
> 	    count *= (TYPE_LENGTH (type) / TYPE_LENGTH (target_type));
> -	      return count;
> +	    TYPE_SET_AAPCS_VFP_CALL_OR_RET_CANDIDATE (type, count);
> 	  }
> +	return;
>       }
> 
>     case TYPE_CODE_STRUCT:
> @@ -1226,20 +1239,23 @@ aapcs_is_vfp_call_or_return_candidate_1 (struct type *type,
> 	  {
> 	    struct type *member = check_typedef (TYPE_FIELD_TYPE (type, i));
> 
> -	    int sub_count = aapcs_is_vfp_call_or_return_candidate_1
> -			      (member, fundamental_type);
> -	    if (sub_count == -1)
> -	      return -1;
> +	    aapcs_is_vfp_call_or_return_candidate_1 (member, fundamental_type);
> +
> +	    int sub_count = TYPE_AAPCS_VFP_CALL_OR_RET_CANDIDATE (member);
> +
> +	    if (sub_count + count > AAPCS_VFP_CALL_OR_RET_CAND_MAX)
> +	      return;
> +
> 	    count += sub_count;
> 	  }
> -	return count;
> +
> +	TYPE_SET_AAPCS_VFP_CALL_OR_RET_CANDIDATE (type, count);
> +	return;
>       }
> 
>     default:
> -      break;
> +      return;
>     }
> -
> -  return -1;
> }
> 
> /* Return true if an argument, whose type is described by TYPE, can be passed or
> @@ -1269,16 +1285,11 @@ aapcs_is_vfp_call_or_return_candidate (struct type *type, int *count,
> 
>   *fundamental_type = nullptr;
> 
> -  int ag_count = aapcs_is_vfp_call_or_return_candidate_1 (type,
> -							  fundamental_type);
> +  aapcs_is_vfp_call_or_return_candidate_1 (type, fundamental_type);
> 
> -  if (ag_count > 0 && ag_count <= HA_MAX_NUM_FLDS)
> -    {
> -      *count = ag_count;
> -      return true;
> -    }
> -  else
> -    return false;
> +  *count = TYPE_AAPCS_VFP_CALL_OR_RET_CANDIDATE (type);
> +
> +  return (*count < AAPCS_VFP_CALL_OR_RET_CAND_INVALID);
> }
> 
> /* AArch64 function call information structure.  */
> diff --git a/gdb/gdbtypes.h b/gdb/gdbtypes.h
> index f0adec7a20..600112abf5 100644
> --- a/gdb/gdbtypes.h
> +++ b/gdb/gdbtypes.h
> @@ -391,6 +391,23 @@ DEF_ENUM_FLAGS_TYPE (enum type_instance_flag_value, type_instance_flags);
> #define TYPE_ADDRESS_CLASS_ALL(t) (TYPE_INSTANCE_FLAGS(t) \
> 				   & TYPE_INSTANCE_FLAG_ADDRESS_CLASS_ALL)
> 
> +
> +/* * Is the given TYPE able to be placed in an Aarch64 VFP when used as a call
> +   parameter or return parameter, as per the AAPCS64 5.4.2.C.  Value can be:
> +     0: the type has not been checked.
> +     1 to AAPCS_VFP_CALL_OR_RET_CAND_MAX: Valid, and has that many members.
> +     AAPCS_VFP_CALL_OR_RET_CAND_MAX: Invalid.  */
> +
> +#define AAPCS_VFP_CALL_OR_RET_CAND_MAX 4
> +#define AAPCS_VFP_CALL_OR_RET_CAND_INVALID (AAPCS_VFP_CALL_OR_RET_CAND_MAX + 1)
> +
> +#define TYPE_AAPCS_VFP_CALL_OR_RET_CANDIDATE(thistype) \
> +  (TYPE_MAIN_TYPE (thistype)->aapcs_candidate_count)
> +
> +#define TYPE_SET_AAPCS_VFP_CALL_OR_RET_CANDIDATE(thistype, val) \
> +  TYPE_AAPCS_VFP_CALL_OR_RET_CANDIDATE (thistype) = \
> +    (std::min (val, AAPCS_VFP_CALL_OR_RET_CAND_MAX + 1))
> +
> /* * Information needed for a discriminated union.  A discriminated
>    union is handled somewhat differently from an ordinary union.
> 
> @@ -716,6 +733,12 @@ struct main_type
> 
>   ENUM_BITFIELD(type_specific_kind) type_specific_field : 3;
> 
> +  /* * Is the given TYPE able to be placed in an Aarch64 VFP when used as a call
> +     parameter or return parameter, as per the AAPCS64 5.4.2.C.  Required to
> +     prevent recursive checking.  */
> +
> +  unsigned int aapcs_candidate_count : 3;
> +
>   /* * Number of fields described for this type.  This field appears
>      at this location because it packs nicely here.  */
> 
> -- 
> 2.17.2 (Apple Git-113)
> 


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]