On Tue, Jun 03, 2025 at 01:37:00PM -0700, Blake Jones wrote: > The BTF dumper code currently displays arrays of characters as just that - > arrays, with each character formatted individually. Sometimes this is what > makes sense, but it's nice to be able to treat that array as a string. > > This change adds a special case to the btf_dump functionality to allow > 0-terminated arrays of single-byte integer values to be printed as > character strings. Characters for which isprint() returns false are > printed as hex-escaped values. This is enabled when the new ".emit_strings" > is set to 1 in the btf_dump_type_data_opts structure. > > As an example, here's what it looks like to dump the string "hello" using > a few different field values for btf_dump_type_data_opts (.compact = 1): > > - .emit_strings = 0, .skip_names = 0: (char[6])['h','e','l','l','o',] > - .emit_strings = 0, .skip_names = 1: ['h','e','l','l','o',] > - .emit_strings = 1, .skip_names = 0: (char[6])"hello" > - .emit_strings = 1, .skip_names = 1: "hello"
hi, could this be used in bpftool map dump? ;-) I checked, but it looks like bpftool map dump is using something else to dump data.. I admit I haven't spent much on time that thanks, jirka > > Here's the string "h\xff", dumped with .compact = 1 and .skip_names = 1: > > - .emit_strings = 0: ['h',-1,] > - .emit_strings = 1: "h\xff" > > Signed-off-by: Blake Jones <[email protected]> > --- > tools/lib/bpf/btf.h | 3 ++- > tools/lib/bpf/btf_dump.c | 55 +++++++++++++++++++++++++++++++++++++++- > 2 files changed, 56 insertions(+), 2 deletions(-) > > diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h > index 4392451d634b..ccfd905f03df 100644 > --- a/tools/lib/bpf/btf.h > +++ b/tools/lib/bpf/btf.h > @@ -326,9 +326,10 @@ struct btf_dump_type_data_opts { > bool compact; /* no newlines/indentation */ > bool skip_names; /* skip member/type names */ > bool emit_zeroes; /* show 0-valued fields */ > + bool emit_strings; /* print char arrays as strings */ > size_t :0; > }; > -#define btf_dump_type_data_opts__last_field emit_zeroes > +#define btf_dump_type_data_opts__last_field emit_strings > > LIBBPF_API int > btf_dump__dump_type_data(struct btf_dump *d, __u32 id, > diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c > index 460c3e57fadb..7c2f1f13f958 100644 > --- a/tools/lib/bpf/btf_dump.c > +++ b/tools/lib/bpf/btf_dump.c > @@ -68,6 +68,7 @@ struct btf_dump_data { > bool compact; > bool skip_names; > bool emit_zeroes; > + bool emit_strings; > __u8 indent_lvl; /* base indent level */ > char indent_str[BTF_DATA_INDENT_STR_LEN]; > /* below are used during iteration */ > @@ -2028,6 +2029,52 @@ static int btf_dump_var_data(struct btf_dump *d, > return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0); > } > > +static int btf_dump_string_data(struct btf_dump *d, > + const struct btf_type *t, > + __u32 id, > + const void *data) > +{ > + const struct btf_array *array = btf_array(t); > + const char *chars = data; > + __u32 i; > + > + /* Make sure it is a NUL-terminated string. */ > + for (i = 0; i < array->nelems; i++) { > + if ((void *)(chars + i) >= d->typed_dump->data_end) > + return -E2BIG; > + if (chars[i] == '\0') > + break; > + } > + if (i == array->nelems) { > + /* The caller will print this as a regular array. */ > + return -EINVAL; > + } > + > + btf_dump_data_pfx(d); > + btf_dump_printf(d, "\""); > + > + for (i = 0; i < array->nelems; i++) { > + char c = chars[i]; > + > + if (c == '\0') { > + /* > + * When printing character arrays as strings, NUL bytes > + * are always treated as string terminators; they are > + * never printed. > + */ > + break; > + } > + if (isprint(c)) > + btf_dump_printf(d, "%c", c); > + else > + btf_dump_printf(d, "\\x%02x", (__u8)c); > + } > + > + btf_dump_printf(d, "\""); > + > + return 0; > +} > + > static int btf_dump_array_data(struct btf_dump *d, > const struct btf_type *t, > __u32 id, > @@ -2055,8 +2102,13 @@ static int btf_dump_array_data(struct btf_dump *d, > * char arrays, so if size is 1 and element is > * printable as a char, we'll do that. > */ > - if (elem_size == 1) > + if (elem_size == 1) { > + if (d->typed_dump->emit_strings && > + btf_dump_string_data(d, t, id, data) == 0) { > + return 0; > + } > d->typed_dump->is_array_char = true; > + } > } > > /* note that we increment depth before calling btf_dump_print() below; > @@ -2544,6 +2596,7 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 > id, > d->typed_dump->compact = OPTS_GET(opts, compact, false); > d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false); > d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false); > + d->typed_dump->emit_strings = OPTS_GET(opts, emit_strings, false); > > ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0); > > -- > 2.49.0.1204.g71687c7c1d-goog >
