Re: [PATCH] btf: Add support to BTF_KIND_ENUM64 type

["Guillermo E. Martinez" <guillermo.e.martinez@oracle.com>]

ping


On 8/29/22 16:11, Guillermo E. Martinez wrote:
> Hello GCC team,
> 
> The following patch update BTF/CTF backend to support
> BTF_KIND_ENUM64 type.
> 
> Comments will be welcomed and appreciated!,
> 
> Kind regards,
> guillermo
> --
> 
> BTF supports 64-bits enumerators with following encoding:
> 
>    struct btf_type:
>      name_off: 0 or offset to a valid C identifier
>      info.kind_flag: 0 for unsigned, 1 for signed
>      info.kind: BTF_KIND_ENUM64
>      info.vlen: number of enum values
>      size: 1/2/4/8
> 
> The btf_type is followed by info.vlen number of:
> 
>      struct btf_enum64
>      {
>        uint32_t name_off;   /* Offset in string section of enumerator name.  */
>        uint32_t val_lo32;   /* lower 32-bit value for a 64-bit value Enumerator */
>        uint32_t val_hi32;   /* high 32-bit value for a 64-bit value Enumerator */
>      };
> 
> So, a new btf_enum64 structure was added to represent BTF_KIND_ENUM64
> and a new field in ctf_dtdef to represent specific type's properties, in
> the particular case for CTF enums it helps to distinguish when its
> enumerators values are signed or unsigned, later that information is
> used to encode the BTF enum type.
> 
> gcc/ChangeLog:
> 
> 	* btfout.cc (btf_calc_num_vbytes): Compute enumeration size depending of
> 	enumerator type btf_enum{,64}.
> 	(btf_asm_type): Update btf_kflag according to enumerators sign,
> 	using correct BPF type in BTF_KIND_ENUMi{,64}.
> 	(btf_asm_enum_const): New argument to represent the size of
> 	the BTF enum type.
> 	* ctfc.cc (ctf_add_enum): Use and initialization of flag field to
> 	CTF_ENUM_F_NONE.
> 	(ctf_add_enumerator): New argument to represent CTF flags,
> 	updating the comment and flag vaue according to enumerators
> 	sing.
> 	* ctfc.h (ctf_dmdef): Update dmd_value to HOST_WIDE_INT to allow
> 	use 32/64 bits enumerators.
> 	(ctf_dtdef): Add flags to to describe specifyc type's properties.
> 	* dwarf2ctf.cc (gen_ctf_enumeration_type): Update flags field
> 	depending when a signed enumerator value is found.
> 	include/btf.h (btf_enum64): Add new definition and new symbolic
> 	constant to BTF_KIND_ENUM64 and BTF_KF_ENUM_{UN,}SIGNED.
> 
> gcc/testsuite/ChangeLog:
> 
> 	gcc.dg/debug/btf/btf-enum-1.c: Update testcase, with correct
> 	info.kflags encoding.
> 	gcc.dg/debug/btf/btf-enum64-1.c: New testcase.
> ---
>   gcc/btfout.cc                                 | 24 ++++++++---
>   gcc/ctfc.cc                                   | 14 ++++---
>   gcc/ctfc.h                                    |  9 +++-
>   gcc/dwarf2ctf.cc                              |  9 +++-
>   gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c   |  2 +-
>   gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c | 41 +++++++++++++++++++
>   include/btf.h                                 | 19 +++++++--
>   7 files changed, 99 insertions(+), 19 deletions(-)
>   create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c
> 
> diff --git a/gcc/btfout.cc b/gcc/btfout.cc
> index 997a33fa089..4b11c867c23 100644
> --- a/gcc/btfout.cc
> +++ b/gcc/btfout.cc
> @@ -223,7 +223,9 @@ btf_calc_num_vbytes (ctf_dtdef_ref dtd)
>         break;
>   
>       case BTF_KIND_ENUM:
> -      vlen_bytes += vlen * sizeof (struct btf_enum);
> +      vlen_bytes += (dtd->dtd_data.ctti_size == 0x8)
> +			? vlen * sizeof (struct btf_enum64)
> +			: vlen * sizeof (struct btf_enum);
>         break;
>   
>       case BTF_KIND_FUNC_PROTO:
> @@ -622,6 +624,15 @@ btf_asm_type (ctf_container_ref ctfc, ctf_dtdef_ref dtd)
>         btf_size_type = 0;
>       }
>   
> + if (btf_kind == BTF_KIND_ENUM)
> +   {
> +     btf_kflag = (dtd->flags & CTF_ENUM_F_ENUMERATORS_SIGNED)
> +		    ? BTF_KF_ENUM_SIGNED
> +		    : BTF_KF_ENUM_UNSIGNED;
> +     if (dtd->dtd_data.ctti_size == 0x8)
> +       btf_kind = BTF_KIND_ENUM64;
> +   }
> +
>     dw2_asm_output_data (4, dtd->dtd_data.ctti_name, "btt_name");
>     dw2_asm_output_data (4, BTF_TYPE_INFO (btf_kind, btf_kflag, btf_vlen),
>   		       "btt_info: kind=%u, kflag=%u, vlen=%u",
> @@ -634,6 +645,7 @@ btf_asm_type (ctf_container_ref ctfc, ctf_dtdef_ref dtd)
>       case BTF_KIND_UNION:
>       case BTF_KIND_ENUM:
>       case BTF_KIND_DATASEC:
> +    case BTF_KIND_ENUM64:
>         dw2_asm_output_data (4, dtd->dtd_data.ctti_size, "btt_size: %uB",
>   			   dtd->dtd_data.ctti_size);
>         return;
> @@ -707,13 +719,13 @@ btf_asm_sou_member (ctf_container_ref ctfc, ctf_dmdef_t * dmd)
>       }
>   }
>   
> -/* Asm'out an enum constant following a BTF_KIND_ENUM.  */
> +/* Asm'out an enum constant following a BTF_KIND_ENUM{,64}.  */
>   
>   static void
> -btf_asm_enum_const (ctf_dmdef_t * dmd)
> +btf_asm_enum_const (unsigned int size, ctf_dmdef_t * dmd)
>   {
>     dw2_asm_output_data (4, dmd->dmd_name_offset, "bte_name");
> -  dw2_asm_output_data (4, dmd->dmd_value, "bte_value");
> +  dw2_asm_output_data (size, dmd->dmd_value, "bte_value");
>   }
>   
>   /* Asm'out a function parameter description following a BTF_KIND_FUNC_PROTO.  */
> @@ -871,7 +883,7 @@ output_asm_btf_sou_fields (ctf_container_ref ctfc, ctf_dtdef_ref dtd)
>         btf_asm_sou_member (ctfc, dmd);
>   }
>   
> -/* Output all enumerator constants following a BTF_KIND_ENUM.  */
> +/* Output all enumerator constants following a BTF_KIND_ENUM{,64}.  */
>   
>   static void
>   output_asm_btf_enum_list (ctf_container_ref ARG_UNUSED (ctfc),
> @@ -881,7 +893,7 @@ output_asm_btf_enum_list (ctf_container_ref ARG_UNUSED (ctfc),
>   
>     for (dmd = dtd->dtd_u.dtu_members;
>          dmd != NULL; dmd = (ctf_dmdef_t *) ctf_dmd_list_next (dmd))
> -    btf_asm_enum_const (dmd);
> +    btf_asm_enum_const (dtd->dtd_data.ctti_size, dmd);
>   }
>   
>   /* Output all function arguments following a BTF_KIND_FUNC_PROTO.  */
> diff --git a/gcc/ctfc.cc b/gcc/ctfc.cc
> index 9773358a475..253c36b6a0a 100644
> --- a/gcc/ctfc.cc
> +++ b/gcc/ctfc.cc
> @@ -604,6 +604,7 @@ ctf_add_enum (ctf_container_ref ctfc, uint32_t flag, const char * name,
>     gcc_assert (size <= CTF_MAX_SIZE);
>   
>     dtd->dtd_data.ctti_size = size;
> +  dtd->flags = CTF_ENUM_F_NONE;
>   
>     ctfc->ctfc_num_stypes++;
>   
> @@ -612,7 +613,7 @@ ctf_add_enum (ctf_container_ref ctfc, uint32_t flag, const char * name,
>   
>   int
>   ctf_add_enumerator (ctf_container_ref ctfc, ctf_id_t enid, const char * name,
> -		    HOST_WIDE_INT value, dw_die_ref die)
> +		    HOST_WIDE_INT value, uint32_t flags, dw_die_ref die)
>   {
>     ctf_dmdef_t * dmd;
>     uint32_t kind, vlen, root;
> @@ -630,10 +631,12 @@ ctf_add_enumerator (ctf_container_ref ctfc, ctf_id_t enid, const char * name,
>   
>     gcc_assert (kind == CTF_K_ENUM && vlen < CTF_MAX_VLEN);
>   
> -  /* Enum value is of type HOST_WIDE_INT in the compiler, dmd_value is int32_t
> -     on the other hand.  Check bounds and skip adding this enum value if out of
> -     bounds.  */
> -  if ((value > INT_MAX) || (value < INT_MIN))
> +  /* Enum value is of type HOST_WIDE_INT in the compiler, CTF enumerators
> +     values in ctf_enum_t is limited to int32_t, BTF supports signed and
> +     unsigned enumerators values of 32 and 64 bits, for both debug formats
> +     we use ctf_dmdef_t.dmd_value entry of HOST_WIDE_INT type. So check
> +     CTF bounds and skip adding this enum value if out of bounds.  */
> +  if (!btf_debuginfo_p() && ((value > INT_MAX) || (value < INT_MIN)))
>       {
>         /* FIXME - Note this TBD_CTF_REPRESENTATION_LIMIT.  */
>         return (1);
> @@ -649,6 +652,7 @@ ctf_add_enumerator (ctf_container_ref ctfc, ctf_id_t enid, const char * name,
>     dmd->dmd_value = value;
>   
>     dtd->dtd_data.ctti_info = CTF_TYPE_INFO (kind, root, vlen + 1);
> +  dtd->flags |= flags;
>     ctf_dmd_list_append (&dtd->dtd_u.dtu_members, dmd);
>   
>     if ((name != NULL) && strcmp (name, ""))
> diff --git a/gcc/ctfc.h b/gcc/ctfc.h
> index bcf3a43ae1b..a22342b2610 100644
> --- a/gcc/ctfc.h
> +++ b/gcc/ctfc.h
> @@ -125,6 +125,10 @@ typedef struct GTY (()) ctf_itype
>   
>   #define CTF_FUNC_VARARG 0x1
>   
> +/* Enum specific flags.  */
> +#define CTF_ENUM_F_NONE                     (0)
> +#define CTF_ENUM_F_ENUMERATORS_SIGNED       (1 << 0)
> +
>   /* Struct/union/enum member definition for CTF generation.  */
>   
>   typedef struct GTY ((chain_next ("%h.dmd_next"))) ctf_dmdef
> @@ -133,7 +137,7 @@ typedef struct GTY ((chain_next ("%h.dmd_next"))) ctf_dmdef
>     ctf_id_t dmd_type;		/* Type of this member (for sou).  */
>     uint32_t dmd_name_offset;	/* Offset of the name in str table.  */
>     uint64_t dmd_offset;		/* Offset of this member in bits (for sou).  */
> -  int dmd_value;		/* Value of this member (for enum).  */
> +  HOST_WIDE_INT dmd_value;	/* Value of this member (for enum).  */
>     struct ctf_dmdef * dmd_next;	/* A list node.  */
>   } ctf_dmdef_t;
>   
> @@ -162,6 +166,7 @@ struct GTY ((for_user)) ctf_dtdef
>     bool from_global_func; /* Whether this type was added from a global
>   			    function.  */
>     uint32_t linkage;           /* Used in function types.  0=local, 1=global.  */
> +  uint32_t flags;             /* Flags to describe specific type's properties.  */
>     union GTY ((desc ("ctf_dtu_d_union_selector (&%1)")))
>     {
>       /* struct, union, or enum.  */
> @@ -429,7 +434,7 @@ extern ctf_id_t ctf_add_sou (ctf_container_ref, uint32_t, const char *,
>   			     uint32_t, size_t, dw_die_ref);
>   
>   extern int ctf_add_enumerator (ctf_container_ref, ctf_id_t, const char *,
> -			       HOST_WIDE_INT, dw_die_ref);
> +			       HOST_WIDE_INT, uint32_t, dw_die_ref);
>   extern int ctf_add_member_offset (ctf_container_ref, dw_die_ref, const char *,
>   				  ctf_id_t, uint64_t);
>   extern int ctf_add_function_arg (ctf_container_ref, dw_die_ref,
> diff --git a/gcc/dwarf2ctf.cc b/gcc/dwarf2ctf.cc
> index 397100004c2..0ef96dd48fd 100644
> --- a/gcc/dwarf2ctf.cc
> +++ b/gcc/dwarf2ctf.cc
> @@ -772,6 +772,7 @@ gen_ctf_enumeration_type (ctf_container_ref ctfc, dw_die_ref enumeration)
>   	  const char *enumerator_name;
>   	  dw_attr_node *enumerator_value;
>   	  HOST_WIDE_INT value_wide_int;
> +	  uint32_t flags = 0;
>   
>   	  c = dw_get_die_sib (c);
>   
> @@ -785,10 +786,14 @@ gen_ctf_enumeration_type (ctf_container_ref ctfc, dw_die_ref enumeration)
>   		  == dw_val_class_unsigned_const_implicit))
>   	    value_wide_int = AT_unsigned (enumerator_value);
>   	  else
> -	    value_wide_int = AT_int (enumerator_value);
> +	    {
> +	      value_wide_int = AT_int (enumerator_value);
> +	      flags |= CTF_ENUM_F_ENUMERATORS_SIGNED;
> +	    }
>   
>   	  ctf_add_enumerator (ctfc, enumeration_type_id,
> -			      enumerator_name, value_wide_int, enumeration);
> +			      enumerator_name, value_wide_int,
> +			      flags, enumeration);
>   	}
>         while (c != dw_get_die_child (enumeration));
>     }
> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c b/gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c
> index 728493b0804..7e940529f1b 100644
> --- a/gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c
> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-enum-1.c
> @@ -4,7 +4,7 @@
>   /* { dg-options "-O0 -gbtf -dA" } */
>   
>   /* { dg-final { scan-assembler-times "\[\t \]0x6000004\[\t \]+\[^\n\]*btt_info" 1 } } */
> -/* { dg-final { scan-assembler-times "\[\t \]0x6000003\[\t \]+\[^\n\]*btt_info" 1 } } */
> +/* { dg-final { scan-assembler-times "\[\t \]0x86000003\[\t \]+\[^\n\]*btt_info" 1 } } */
>   /* { dg-final { scan-assembler-times "ascii \"QAD.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
>   /* { dg-final { scan-assembler-times "ascii \"QED.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
>   /* { dg-final { scan-assembler-times "ascii \"QOD.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c b/gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c
> new file mode 100644
> index 00000000000..da103842807
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-enum64-1.c
> @@ -0,0 +1,41 @@
> +/* Test BTF generation for 64 bits enums.  */
> +
> +/* { dg-do compile } */
> +/* { dg-options "-O0 -gbtf -dA" } */
> +
> +/* { dg-final { scan-assembler-times "\[\t \].size\[\t \]myenum1,\[\t \]8" 1 } } */
> +/* { dg-final { scan-assembler-times "\[\t \].size\[\t \]myenum2,\[\t \]8" 1 } } */
> +/* { dg-final { scan-assembler-times "\[\t \].size\[\t \]myenum3,\[\t \]8" 1 } } */
> +/* { dg-final { scan-assembler-times "\[\t \]0x13000003\[\t \]+\[^\n\]*btt_info" 2 } } */
> +/* { dg-final { scan-assembler-times "\[\t \]0x93000003\[\t \]+\[^\n\]*btt_info" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"B1.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"B2.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"B3.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"C1.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"C2.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"C3.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"D1.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"D2.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "ascii \"D3.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
> +/* { dg-final { scan-assembler-times "bte_value" 9 } } */
> +
> +enum default_enum
> +{
> +  B1 = 0xffffffffaa,
> +  B2 = 0xbbbbbbbb,
> +  B3 = 0xaabbccdd,
> +} myenum1 = B1;
> +
> +enum explicit_unsigned
> +{
> +  C1 = 0xffffffffbbUL,
> +  C2 = 0xbbbbbbbb,
> +  C3 = 0xaabbccdd,
> +} myenum2 = C1;
> +
> +enum signed64
> +{
> +  D1 = 0xffffffffaa,
> +  D2 = 0xbbbbbbbb,
> +  D3 = -0x1,
> +} myenum3 = D1;
> diff --git a/include/btf.h b/include/btf.h
> index 78b551ced23..eba67f9d599 100644
> --- a/include/btf.h
> +++ b/include/btf.h
> @@ -109,7 +109,8 @@ struct btf_type
>   #define BTF_KIND_VAR		14	/* Variable.  */
>   #define BTF_KIND_DATASEC	15	/* Section such as .bss or .data.  */
>   #define BTF_KIND_FLOAT		16	/* Floating point.  */
> -#define BTF_KIND_MAX		BTF_KIND_FLOAT
> +#define BTF_KIND_ENUM64 	19	/* Enumeration up to 64 bits.  */
> +#define BTF_KIND_MAX		BTF_KIND_ENUM64
>   #define NR_BTF_KINDS		(BTF_KIND_MAX + 1)
>   
>   /* For some BTF_KINDs, struct btf_type is immediately followed by
> @@ -130,14 +131,17 @@ struct btf_type
>   #define BTF_INT_BOOL	(1 << 2)
>   
>   /* BTF_KIND_ENUM is followed by VLEN struct btf_enum entries,
> -   which describe the enumerators. Note that BTF currently only
> -   supports signed 32-bit enumerator values.  */
> +   which describe the enumerators. */
>   struct btf_enum
>   {
>     uint32_t name_off;	/* Offset in string section of enumerator name.  */
>     int32_t  val;		/* Enumerator value.  */
>   };
>   
> +/* BTF_KF_ENUM_ holds the flags for kflags in BTF_KIND_ENUM{,64}.  */
> +#define BTF_KF_ENUM_UNSIGNED	(0)
> +#define BTF_KF_ENUM_SIGNED 	(1 << 0)
> +
>   /* BTF_KIND_ARRAY is followed by a single struct btf_array.  */
>   struct btf_array
>   {
> @@ -190,6 +194,15 @@ struct btf_var_secinfo
>     uint32_t size;	/* Size (in bytes) of variable.  */
>   };
>   
> +/* BTF_KIND_ENUM64 is followed by VLEN struct btf_enum64 entries,
> +   which describe the 64 bits enumerators.  */
> +struct btf_enum64
> +{
> +  uint32_t name_off;	/* Offset in string section of enumerator name.  */
> +  uint32_t val_lo32;	/* lower 32-bit value for a 64-bit value Enumerator */
> +  uint32_t val_hi32;	/* high 32-bit value for a 64-bit value Enumerator */
> +};
> +
>   #ifdef	__cplusplus
>   }
>   #endif