btf: Add support for the floating-point types
Some BPF programs compiled on s390 fail to load, because s390 arch-specific linux headers contain float and double types. Fix as follows: - Make the DWARF loader fill base_type.float_type. - Introduce the --btf_gen_floats command-line parameter, so that pahole could be used to build both the older and the newer kernels. - libbpf introduced the support for the floating-point types in commit 986962fade5, so update the libbpf submodule to that version and use the new btf__add_float() function in order to emit the floating-point types when not in the compatibility mode. - Make the BTF loader recognize the new BTF kind. Example of the resulting entry in the vmlinux BTF: [7164] FLOAT 'double' size=8 when building with: LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1} --btf_gen_floats Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Yonghong Song <yhs@fb.com> Cc: bpf@vger.kernel.org Cc: dwarves@vger.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
parent
4b7f8c04d0
commit
de708b3311
21
btf_loader.c
21
btf_loader.c
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@ -160,7 +160,7 @@ static struct variable *variable__new(strings_t name, uint32_t linkage)
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return var;
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}
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static int create_new_base_type(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id)
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static int create_new_int_type(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id)
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{
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uint32_t attrs = btf_int_encoding(tp);
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strings_t name = tp->name_off;
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@ -175,6 +175,20 @@ static int create_new_base_type(struct btf_elf *btfe, const struct btf_type *tp,
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return 0;
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}
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static int create_new_float_type(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id)
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{
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strings_t name = tp->name_off;
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struct base_type *base = base_type__new(name, 0, BT_FP_SINGLE, tp->size * 8);
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if (base == NULL)
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return -ENOMEM;
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base->tag.tag = DW_TAG_base_type;
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cu__add_tag_with_id(btfe->priv, &base->tag, id);
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return 0;
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}
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static int create_new_array(struct btf_elf *btfe, const struct btf_type *tp, uint32_t id)
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{
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struct btf_array *ap = btf_array(tp);
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@ -397,7 +411,7 @@ static int btf_elf__load_types(struct btf_elf *btfe)
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switch (type) {
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case BTF_KIND_INT:
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err = create_new_base_type(btfe, type_ptr, type_index);
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err = create_new_int_type(btfe, type_ptr, type_index);
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break;
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case BTF_KIND_ARRAY:
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err = create_new_array(btfe, type_ptr, type_index);
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@ -442,6 +456,9 @@ static int btf_elf__load_types(struct btf_elf *btfe)
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// BTF_KIND_FUNC corresponding to a defined subprogram.
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err = create_new_function(btfe, type_ptr, type_index);
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break;
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case BTF_KIND_FLOAT:
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err = create_new_float_type(btfe, type_ptr, type_index);
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break;
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default:
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fprintf(stderr, "BTF: idx: %d, Unknown kind %d\n", type_index, type);
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fflush(stderr);
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@ -461,6 +461,16 @@ static struct ptr_to_member_type *ptr_to_member_type__new(Dwarf_Die *die,
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return ptr;
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}
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static uint8_t encoding_to_float_type(uint64_t encoding)
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{
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switch (encoding) {
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case DW_ATE_complex_float: return BT_FP_CMPLX;
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case DW_ATE_float: return BT_FP_SINGLE;
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case DW_ATE_imaginary_float: return BT_FP_IMGRY;
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default: return 0;
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}
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}
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static struct base_type *base_type__new(Dwarf_Die *die, struct cu *cu)
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{
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struct base_type *bt = tag__alloc(cu, sizeof(*bt));
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@ -474,6 +484,7 @@ static struct base_type *base_type__new(Dwarf_Die *die, struct cu *cu)
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bt->is_signed = encoding == DW_ATE_signed;
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bt->is_varargs = false;
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bt->name_has_encoding = true;
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bt->float_type = encoding_to_float_type(encoding);
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}
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return bt;
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2
lib/bpf
2
lib/bpf
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@ -1 +1 @@
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Subproject commit 5af3d86b5a2c5fecdc3ab83822d083edd32b4396
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Subproject commit 986962fade5dfa89c2890f3854eb040d2a64ab38
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36
libbtf.c
36
libbtf.c
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@ -40,6 +40,7 @@
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struct btf *base_btf;
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uint8_t btf_elf__verbose;
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uint8_t btf_elf__force;
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bool btf_gen_floats = false;
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static int btf_var_secinfo_cmp(const void *a, const void *b)
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{
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@ -235,6 +236,7 @@ static const char * const btf_kind_str[NR_BTF_KINDS] = {
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[BTF_KIND_FUNC_PROTO] = "FUNC_PROTO",
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[BTF_KIND_VAR] = "VAR",
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[BTF_KIND_DATASEC] = "DATASEC",
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[BTF_KIND_FLOAT] = "FLOAT",
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};
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static const char *btf_elf__printable_name(const struct btf_elf *btfe, uint32_t offset)
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@ -375,6 +377,27 @@ static void btf_log_func_param(const struct btf_elf *btfe,
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}
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}
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static int32_t btf_elf__add_float_type(struct btf_elf *btfe,
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const struct base_type *bt,
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const char *name)
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{
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int32_t id;
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id = btf__add_float(btfe->btf, name, BITS_ROUNDUP_BYTES(bt->bit_size));
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if (id < 0) {
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btf_elf__log_err(btfe, BTF_KIND_FLOAT, name, true, "Error emitting BTF type");
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} else {
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const struct btf_type *t;
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t = btf__type_by_id(btfe->btf, id);
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btf_elf__log_type(btfe, t, false, true,
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"size=%u nr_bits=%u",
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t->size, bt->bit_size);
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}
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return id;
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}
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int32_t btf_elf__add_base_type(struct btf_elf *btfe, const struct base_type *bt,
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const char *name)
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{
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@ -388,8 +411,17 @@ int32_t btf_elf__add_base_type(struct btf_elf *btfe, const struct base_type *bt,
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encoding = BTF_INT_SIGNED;
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} else if (bt->is_bool) {
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encoding = BTF_INT_BOOL;
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} else if (bt->float_type) {
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fprintf(stderr, "float_type is not supported\n");
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} else if (bt->float_type && btf_gen_floats) {
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/*
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* Encode floats as BTF_KIND_FLOAT if allowed, otherwise (in
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* compatibility mode) encode them as BTF_KIND_INT - that's not
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* fully correct, but that's what it used to be.
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*/
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if (bt->float_type == BT_FP_SINGLE ||
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bt->float_type == BT_FP_DOUBLE ||
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bt->float_type == BT_FP_LDBL)
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return btf_elf__add_float_type(btfe, bt, name);
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fprintf(stderr, "Complex, interval and imaginary float types are not supported\n");
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return -1;
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}
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1
libbtf.h
1
libbtf.h
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@ -35,6 +35,7 @@ extern struct btf *base_btf;
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extern uint8_t btf_elf__verbose;
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extern uint8_t btf_elf__force;
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#define btf_elf__verbose_log(fmt, ...) { if (btf_elf__verbose) printf(fmt, __VA_ARGS__); }
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extern bool btf_gen_floats;
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#define PERCPU_SECTION ".data..percpu"
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@ -199,6 +199,11 @@ Path to the base BTF file, for instance: vmlinux when encoding kernel module BTF
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This may be inferred when asking for a /sys/kernel/btf/MODULE, when it will be autoconfigured
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to "/sys/kernel/btf/vmlinux".
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.TP
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.B \-\-btf_gen_floats
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Allow producing BTF_KIND_FLOAT entries in systems where the vmlinux DWARF
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information has float types.
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.TP
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.B \-l, \-\-show_first_biggest_size_base_type_member
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Show first biggest size base_type member.
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8
pahole.c
8
pahole.c
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@ -825,6 +825,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
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#define ARGP_just_packed_structs 319
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#define ARGP_numeric_version 320
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#define ARGP_btf_base 321
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#define ARGP_btf_gen_floats 322
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static const struct argp_option pahole__options[] = {
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{
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@ -1119,6 +1120,11 @@ static const struct argp_option pahole__options[] = {
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.key = ARGP_btf_encode_force,
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.doc = "Ignore those symbols found invalid when encoding BTF."
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},
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{
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.name = "btf_gen_floats",
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.key = ARGP_btf_gen_floats,
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.doc = "Allow producing BTF_KIND_FLOAT entries."
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},
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{
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.name = "structs",
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.key = ARGP_just_structs,
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@ -1254,6 +1260,8 @@ static error_t pahole__options_parser(int key, char *arg,
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base_btf_file = arg; break;
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case ARGP_numeric_version:
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print_numeric_version = true; break;
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case ARGP_btf_gen_floats:
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btf_gen_floats = true; break;
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default:
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return ARGP_ERR_UNKNOWN;
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}
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