btf: Support BTF_KIND_ENUM64

BTF_KIND_ENUM64 is supported with latest libbpf, which supports 64-bit
enum values. Latest libbpf also supports signedness for enum values. Add
enum64 support in dwarf-to-btf conversion.

The following is an example of new encoding which covers signed/unsigned
enum64/enum variations.

  $ cat t.c
  enum { /* signed, enum64 */
    A = -1,
    B = 0xffffffff,
  } g1;
  enum { /* unsigned, enum64 */
    C = 1,
    D = 0xfffffffff,
  } g2;
  enum { /* signed, enum */
    E = -1,
    F = 0xfffffff,
  } g3;
  enum { /* unsigned, enum */
    G = 1,
    H = 0xfffffff,
  } g4;
  $ clang -g -c t.c
  $ pahole -JV t.o
  btf_encoder__new: 't.o' doesn't have '.data..percpu' section
  Found 0 per-CPU variables!
  File t.o:
  [1] ENUM64 (anon) size=8
          A val=-1
          B val=4294967295
  [2] INT long size=8 nr_bits=64 encoding=SIGNED
  [3] ENUM64 (anon) size=8
          C val=1
          D val=68719476735
  [4] INT unsigned long size=8 nr_bits=64 encoding=(none)
  [5] ENUM (anon) size=4
          E val=-1
          F val=268435455
  [6] INT int size=4 nr_bits=32 encoding=SIGNED
  [7] ENUM (anon) size=4
          G val=1
          H val=268435455
  [8] INT unsigned int size=4 nr_bits=32 encoding=(none)

With the flag to skip enum64 encoding,

  $ pahole -JV t.o --skip_encoding_btf_enum64
  btf_encoder__new: 't.o' doesn't have '.data..percpu' section
  Found 0 per-CPU variables!
  File t.o:
  [1] ENUM (anon) size=8
        A val=4294967295
        B val=4294967295
  [2] INT long size=8 nr_bits=64 encoding=SIGNED
  [3] ENUM (anon) size=8
        C val=1
        D val=4294967295
  [4] INT unsigned long size=8 nr_bits=64 encoding=(none)
  [5] ENUM (anon) size=4
        E val=4294967295
        F val=268435455
  [6] INT int size=4 nr_bits=32 encoding=SIGNED
  [7] ENUM (anon) size=4
        G val=1
        H val=268435455
  [8] INT unsigned int size=4 nr_bits=32 encoding=(none)

In the above BTF encoding without enum64, all enum types with the same
type size as the corresponding enum64. All these enum types have
unsigned type (kflag = 0) which is required before kernel enum64
support.

Committer notes:

Add entry about --skip_encoding_btf_enum64 in the man page.

Committer testing:

  $ clang -g -c enum64.c

Before this patch:

  $ pahole -JV enum64.o
  btf_encoder__new: 'enum64.o' doesn't have '.data..percpu' section
  Found 0 per-CPU variables!
  File enum64.o:
  [1] ENUM (anon) size=8
	  A val=-1
	  B val=-1
  [2] INT long size=8 nr_bits=64 encoding=SIGNED
  [3] ENUM (anon) size=8
	  C val=1
	  D val=-1
  [4] INT unsigned long size=8 nr_bits=64 encoding=(none)
  [5] ENUM (anon) size=4
	  E val=-1
	  F val=268435455
  [6] INT int size=4 nr_bits=32 encoding=SIGNED
  [7] ENUM (anon) size=4
	  G val=1
	  H val=268435455
  [8] INT unsigned int size=4 nr_bits=32 encoding=(none)
  $

After:

  $ pahole -JV enum64.o
  btf_encoder__new: 'enum64.o' doesn't have '.data..percpu' section
  Found 0 per-CPU variables!
  File enum64.o:
  [1] ENUM64 (anon) size=8
  	A val=-1
  	B val=4294967295
  [2] INT long size=8 nr_bits=64 encoding=SIGNED
  [3] ENUM64 (anon) size=8
  	C val=1
  	D val=68719476735
  [4] INT unsigned long size=8 nr_bits=64 encoding=(none)
  [5] ENUM (anon) size=4
  	E val=-1
  	F val=268435455
  [6] INT int size=4 nr_bits=32 encoding=SIGNED
  [7] ENUM (anon) size=4
  	G val=1
  	H val=268435455
  [8] INT unsigned int size=4 nr_bits=32 encoding=(none)
  $

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: bpf@vger.kernel.org
Cc: dwarves@vger.kernel.org
Cc: kernel-team@fb.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

7 files changed, 84 insertions, 21 deletions

diff --git a/btf_encoder.c b/btf_encoder.c
index 9e708e49..daa8e3b5 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -144,6 +144,7 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
 	[BTF_KIND_FLOAT]        = "FLOAT",
 	[BTF_KIND_DECL_TAG]     = "DECL_TAG",
 	[BTF_KIND_TYPE_TAG]     = "TYPE_TAG",
+	[BTF_KIND_ENUM64]	= "ENUM64",
 };
 
 static const char *btf__printable_name(const struct btf *btf, uint32_t offset)
@@ -490,34 +491,64 @@ static int32_t btf_encoder__add_struct(struct btf_encoder *encoder, uint8_t kind
 	return id;
 }
 
-static int32_t btf_encoder__add_enum(struct btf_encoder *encoder, const char *name, uint32_t bit_size)
+static int32_t btf_encoder__add_enum(struct btf_encoder *encoder, const char *name, struct type *etype,
+				     struct conf_load *conf_load)
 {
 	struct btf *btf = encoder->btf;
 	const struct btf_type *t;
 	int32_t id, size;
+	bool is_enum32;
 
-	size = BITS_ROUNDUP_BYTES(bit_size);
-	id = btf__add_enum(btf, name, size);
+	size = BITS_ROUNDUP_BYTES(etype->size);
+	is_enum32 = size <= 4 || conf_load->skip_encoding_btf_enum64;
+	if (is_enum32)
+		id = btf__add_enum(btf, name, size);
+	else
+		id = btf__add_enum64(btf, name, size, etype->is_signed_enum);
 	if (id > 0) {
 		t = btf__type_by_id(btf, id);
 		btf_encoder__log_type(encoder, t, false, true, "size=%u", t->size);
 	} else {
-		btf__log_err(btf, BTF_KIND_ENUM, name, true,
+		btf__log_err(btf, is_enum32 ? BTF_KIND_ENUM : BTF_KIND_ENUM64, name, true,
 			      "size=%u Error emitting BTF type", size);
 	}
 	return id;
 }
 
-static int btf_encoder__add_enum_val(struct btf_encoder *encoder, const char *name, int32_t value)
+static int btf_encoder__add_enum_val(struct btf_encoder *encoder, const char *name, int64_t value,
+				     struct type *etype, struct conf_load *conf_load)
 {
-	int err = btf__add_enum_value(encoder->btf, name, value);
+	const char *fmt_str;
+	int err;
+
+	/* If enum64 is not allowed, generate enum32 with unsigned int value. In enum64-supported
+	 * libbpf library, btf__add_enum_value() will set the kflag (sign bit) in common_type
+	 * if the value is negative.
+	 */
+	if (conf_load->skip_encoding_btf_enum64)
+		err = btf__add_enum_value(encoder->btf, name, (uint32_t)value);
+	else if (etype->size > 32)
+		err = btf__add_enum64_value(encoder->btf, name, value);
+	else
+		err = btf__add_enum_value(encoder->btf, name, value);
 
 	if (!err) {
-		if (encoder->verbose)
-			printf("\t%s val=%d\n", name, value);
+		if (encoder->verbose) {
+			if (conf_load->skip_encoding_btf_enum64) {
+				printf("\t%s val=%u\n", name, (uint32_t)value);
+			} else {
+				fmt_str = etype->is_signed_enum ? "\t%s val=%lld\n" : "\t%s val=%llu\n";
+				printf(fmt_str, name, (unsigned long long)value);
+			}
+		}
 	} else {
-		fprintf(stderr, "\t%s val=%d Error emitting BTF enum value\n",
-			name, value);
+		if (conf_load->skip_encoding_btf_enum64) {
+			fprintf(stderr, "\t%s val=%u Error emitting BTF enum value\n", name, (uint32_t)value);
+		} else {
+			fmt_str = etype->is_signed_enum ? "\t%s val=%lld Error emitting BTF enum value\n"
+							: "\t%s val=%llu Error emitting BTF enum value\n";
+			fprintf(stderr, fmt_str, name, (unsigned long long)value);
+		}
 	}
 	return err;
 }
@@ -844,27 +875,29 @@ static uint32_t array_type__nelems(struct tag *tag)
 	return nelem;
 }
 
-static int32_t btf_encoder__add_enum_type(struct btf_encoder *encoder, struct tag *tag)
+static int32_t btf_encoder__add_enum_type(struct btf_encoder *encoder, struct tag *tag,
+					  struct conf_load *conf_load)
 {
 	struct type *etype = tag__type(tag);
 	struct enumerator *pos;
 	const char *name = type__name(etype);
 	int32_t type_id;
 
-	type_id = btf_encoder__add_enum(encoder, name, etype->size);
+	type_id = btf_encoder__add_enum(encoder, name, etype, conf_load);
 	if (type_id < 0)
 		return type_id;
 
 	type__for_each_enumerator(etype, pos) {
 		name = enumerator__name(pos);
-		if (btf_encoder__add_enum_val(encoder, name, pos->value))
+		if (btf_encoder__add_enum_val(encoder, name, pos->value, etype, conf_load))
 			return -1;
 	}
 
 	return type_id;
 }
 
-static int btf_encoder__encode_tag(struct btf_encoder *encoder, struct tag *tag, uint32_t type_id_off)
+static int btf_encoder__encode_tag(struct btf_encoder *encoder, struct tag *tag, uint32_t type_id_off,
+				   struct conf_load *conf_load)
 {
 	/* single out type 0 as it represents special type "void" */
 	uint32_t ref_type_id = tag->type == 0 ? 0 : type_id_off + tag->type;
@@ -903,7 +936,7 @@ static int btf_encoder__encode_tag(struct btf_encoder *encoder, struct tag *tag,
 		encoder->need_index_type = true;
 		return btf_encoder__add_array(encoder, ref_type_id, encoder->array_index_id, array_type__nelems(tag));
 	case DW_TAG_enumeration_type:
-		return btf_encoder__add_enum_type(encoder, tag);
+		return btf_encoder__add_enum_type(encoder, tag, conf_load);
 	case DW_TAG_subroutine_type:
 		return btf_encoder__add_func_proto(encoder, tag__ftype(tag), type_id_off);
 	default:
@@ -1422,7 +1455,7 @@ void btf_encoder__delete(struct btf_encoder *encoder)
 	free(encoder);
 }
 
-int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu)
+int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu, struct conf_load *conf_load)
 {
 	uint32_t type_id_off = btf__type_cnt(encoder->btf) - 1;
 	struct llvm_annotation *annot;
@@ -1446,7 +1479,7 @@ int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu)
 	}
 
 	cu__for_each_type(cu, core_id, pos) {
-		btf_type_id = btf_encoder__encode_tag(encoder, pos, type_id_off);
+		btf_type_id = btf_encoder__encode_tag(encoder, pos, type_id_off, conf_load);
 
 		if (btf_type_id < 0 ||
 		    tag__check_id_drift(pos, core_id, btf_type_id, type_id_off)) {
diff --git a/btf_encoder.h b/btf_encoder.h
index 339fae20..a65120cc 100644
--- a/btf_encoder.h
+++ b/btf_encoder.h
@@ -21,7 +21,7 @@ void btf_encoder__delete(struct btf_encoder *encoder);
 
 int btf_encoder__encode(struct btf_encoder *encoder);
 
-int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu);
+int btf_encoder__encode_cu(struct btf_encoder *encoder, struct cu *cu, struct conf_load *conf_load);
 
 void btf_encoders__add(struct list_head *encoders, struct btf_encoder *encoder);
 
diff --git a/dwarf_loader.c b/dwarf_loader.c
index a0d964bd..47676028 100644
--- a/dwarf_loader.c
+++ b/dwarf_loader.c
@@ -632,6 +632,18 @@ static void type__init(struct type *type, Dwarf_Die *die, struct cu *cu, struct
 	type->resized		 = 0;
 	type->nr_members	 = 0;
 	type->nr_static_members	 = 0;
+	type->is_signed_enum	 = 0;
+
+	Dwarf_Attribute attr;
+	if (dwarf_attr(die, DW_AT_type, &attr) != NULL) {
+		Dwarf_Die type_die;
+		if (dwarf_formref_die(&attr, &type_die) != NULL) {
+			uint64_t encoding = attr_numeric(&type_die, DW_AT_encoding);
+
+			if (encoding == DW_ATE_signed || encoding == DW_ATE_signed_char)
+				type->is_signed_enum = 1;
+		}
+	}
 }
 
 static struct type *type__new(Dwarf_Die *die, struct cu *cu, struct conf_load *conf)
diff --git a/dwarves.h b/dwarves.h
index 4d0e4b6e..bec9f08c 100644
--- a/dwarves.h
+++ b/dwarves.h
@@ -65,6 +65,7 @@ struct conf_load {
 	bool			skip_encoding_btf_decl_tag;
 	bool			skip_missing;
 	bool			skip_encoding_btf_type_tag;
+	bool			skip_encoding_btf_enum64;
 	uint8_t			hashtable_bits;
 	uint8_t			max_hashtable_bits;
 	uint16_t		kabi_prefix_len;
@@ -1046,6 +1047,7 @@ struct type {
 	uint8_t		 definition_emitted:1;
 	uint8_t		 fwd_decl_emitted:1;
 	uint8_t		 resized:1;
+	uint8_t		 is_signed_enum:1;
 };
 
 void __type__init(struct type *type);
@@ -1365,7 +1367,7 @@ static inline struct string_type *tag__string_type(const struct tag *tag)
 struct enumerator {
 	struct tag	 tag;
 	const char	 *name;
-	uint32_t	 value;
+	uint64_t	 value;
 	struct tag_cu	 type_enum; // To cache the type_enum searches
 };
 
diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c
index 2cec5843..ce64c79b 100644
--- a/dwarves_fprintf.c
+++ b/dwarves_fprintf.c
@@ -437,7 +437,11 @@ size_t enumeration__fprintf(const struct tag *tag, const struct conf_fprintf *co
 	type__for_each_enumerator(type, pos) {
 		printed += fprintf(fp, "%.*s\t%-*s = ", indent, tabs,
 				   max_entry_name_len, enumerator__name(pos));
-		printed += fprintf(fp, conf->hex_fmt ?  "%#x" : "%u", pos->value);
+		if (conf->hex_fmt)
+			printed += fprintf(fp, "%#llx", (unsigned long long)pos->value);
+		else
+			printed += fprintf(fp, type->is_signed_enum ?  "%lld" : "%llu",
+					   (unsigned long long)pos->value);
 		printed += fprintf(fp, ",\n");
 	}
 
diff --git a/man-pages/pahole.1 b/man-pages/pahole.1
index eefa4376..bb88e2f5 100644
--- a/man-pages/pahole.1
+++ b/man-pages/pahole.1
@@ -214,6 +214,10 @@ Do not encode VARs in BTF.
 Do not encode decl tags in BTF.
 
 .TP
+.B \-\-skip_encoding_btf_enum64
+Do not encode enum64 in BTF.
+
+.TP
 .B \-\-skip_encoding_btf_type_tag
 Do not encode type tags in BTF.
 
diff --git a/pahole.c b/pahole.c
index 78caa080..e87d9a47 100644
--- a/pahole.c
+++ b/pahole.c
@@ -1220,6 +1220,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
 #define ARGP_compile		   334
 #define ARGP_languages		   335
 #define ARGP_languages_exclude	   336
+#define ARGP_skip_encoding_btf_enum64 337
 
 static const struct argp_option pahole__options[] = {
 	{
@@ -1623,6 +1624,11 @@ static const struct argp_option pahole__options[] = {
 		.doc  = "Don't consider compilation units written in these languages"
 	},
 	{
+		.name = "skip_encoding_btf_enum64",
+		.key  = ARGP_skip_encoding_btf_enum64,
+		.doc  = "Do not encode ENUM64sin BTF."
+	},
+	{
 		.name = NULL,
 	}
 };
@@ -1787,6 +1793,8 @@ static error_t pahole__options_parser(int key, char *arg,
 		/* fallthru */
 	case ARGP_languages:
 		languages.str = arg;			break;
+	case ARGP_skip_encoding_btf_enum64:
+		conf_load.skip_encoding_btf_enum64 = true;	break;
 	default:
 		return ARGP_ERR_UNKNOWN;
 	}
@@ -3067,7 +3075,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
 			encoder = btf_encoder;
 		}
 
-		if (btf_encoder__encode_cu(encoder, cu)) {
+		if (btf_encoder__encode_cu(encoder, cu, conf_load)) {
 			fprintf(stderr, "Encountered error while encoding BTF.\n");
 			exit(1);
 		}