Re: [PATCH v3 bpf-next 1/2] libbpf: BTF dumper support for typed data
From: Andrii Nakryiko <hidden>
Date: 2021-05-28 01:25:12
Also in:
bpf, linux-kselftest, lkml
On Thu, May 27, 2021 at 9:00 AM Alan Maguire [off-list ref] wrote:
Add a BTF dumper for typed data, so that the user can dump a typed
version of the data provided.
The API is
int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
void *data, size_t byte_sz,
const struct btf_dump_type_data_opts *opts);
...where the id is the BTF id of the data pointed to by the "void *"
argument; for example the BTF id of "struct sk_buff" for a
"struct skb *" data pointer. Options supported are
- a starting indent level (indent_lvl)
- a set of boolean options to control dump display, similar to those
used for BPF helper bpf_snprintf_btf(). Options are
- compact : omit newlines and other indentation
- skip_names: omit member names
- emit_zeroes: show zero-value members
Default output format is identical to that dumped by bpf_snprintf_btf(),
for example a "struct sk_buff" representation would look like this:
struct sk_buff){
(union){
(struct){
.next = (struct sk_buff *)0xffffffffffffffff,
.prev = (struct sk_buff *)0xffffffffffffffff,
(union){
.dev = (struct net_device *)0xffffffffffffffff,
.dev_scratch = (long unsigned int)18446744073709551615,
},
},
...Is the '\t' as a default indentation filler a requirement? With 8 spaces per tab this gets wide really fast. 2 or 4 spaces might be a better default? And it probably would be good to let users specify this as a string (e.g., "indent_str"), which could be anything the user wants, from empty string to multiple tabs to "..." to whatever else. If I needed to dump something with this API, I'd probably use 2 spaces, for instance. But I can see how other users might want something else, so making this customizable seems like a good thing?
If the data structure is larger than the *byte_sz* number of bytes that are available in *data*, as much of the data as possible will be dumped and -E2BIG will be returned. This is useful as tracers will sometimes not be able to capture all of the data associated with a type; for example a "struct task_struct" is ~16k. Being able to specify that only a subset is available is important for such cases. Signed-off-by: Alan Maguire <redacted> ---
I'll do another pass next week, I ran out of time, it's a bit of a big patch, sorry. But left few comments, please take a look.
quoted hunk ↗ jump to hunk
tools/lib/bpf/btf.h | 17 + tools/lib/bpf/btf_dump.c | 901 +++++++++++++++++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.map | 5 + 3 files changed, 923 insertions(+)diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index b54f1c3..234aa97 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h@@ -184,6 +184,23 @@ struct btf_dump_emit_type_decl_opts { btf_dump__emit_type_decl(struct btf_dump *d, __u32 id, const struct btf_dump_emit_type_decl_opts *opts); + +struct btf_dump_type_data_opts { + /* size of this struct, for forward/backward compatibility */ + size_t sz; + int indent_level; + /* below match "show" flags for bpf_show_snprintf() */ + bool compact; /* no newlines/tabs */ + bool skip_names; /* skip member/type names */ + bool emit_zeroes; /* show 0-valued fields */
please add size_t: 0; as the last member to avoid various issues with non-zero padding. We've been doing it for a few not perfectly aligned opts recently and that seems to work good in practice.
+}; +#define btf_dump_type_data_opts__last_field emit_zeroes + +LIBBPF_API int +btf_dump__dump_type_data(struct btf_dump *d, __u32 id, + void *data, size_t byte_sz,
can't get over data vs byte_sz naming inconsistency.... why not data and data_sz? also, const void *data?
quoted hunk ↗ jump to hunk
+ const struct btf_dump_type_data_opts *opts); + /* * A set of helpers for easier BTF types handling */diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index 5e2809d..27baa6a 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c@@ -10,6 +10,8 @@ #include <stddef.h> #include <stdlib.h> #include <string.h> +#include <ctype.h> +#include <endian.h> #include <errno.h> #include <linux/err.h> #include <linux/btf.h>@@ -19,6 +21,13 @@ #include "libbpf.h" #include "libbpf_internal.h" +#define BITS_PER_BYTE 8 +#define BITS_PER_U128 128 +#define BITS_PER_BYTE_MASK (BITS_PER_BYTE - 1) +#define BITS_PER_BYTE_MASKED(bits) ((bits) & BITS_PER_BYTE_MASK) +#define BITS_ROUNDDOWN_BYTES(bits) ((bits) / 8) +#define BITS_ROUNDUP_BYTES(bits) (roundup(bits, 8)) + static const char PREFIXES[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t"; static const size_t PREFIX_CNT = sizeof(PREFIXES) - 1;@@ -53,6 +62,25 @@ struct btf_dump_type_aux_state { __u8 referenced: 1; }; +/* + * Common internal data for BTF type data dump operations. + */ +struct btf_dump_data { + void *data_end; /* end of valid data to show */ + bool compact; + bool skip_names; + bool emit_zeroes; + __u8 indent_lvl; /* base indent level */ + /* below are used during iteration */ + struct { + __u8 depth; + __u8 array_member:1, + array_terminated:1, + array_ischar:1; + __u32 bitfield_size; + } state; +}; + struct btf_dump { const struct btf *btf; const struct btf_ext *btf_ext;@@ -89,6 +117,10 @@ struct btf_dump { * name occurrences */ struct hashmap *ident_names; + /* + * data for typed display. + */ + struct btf_dump_data data;
given it's not always used, should this be allocated lazily only if necessary?
quoted hunk ↗ jump to hunk
}; static size_t str_hash_fn(const void *key, void *ctx)@@ -1392,6 +1424,91 @@ static void btf_dump_emit_type_chain(struct btf_dump *d, btf_dump_emit_name(d, fname, last_was_ptr); } +/* show type name as [.fname =] (type_name) */ +static void btf_dump_emit_type_name(struct btf_dump *d, __u32 id, + const char *fname, int lvl, bool toplevel)
Sorry, I didn't get from your cover letter why btf_dump__emit_type_decl() doesn't do what you need it to do. Can you please elaborate with a simple example?
+{
+
+ const struct btf_type *t, *child;
+ const char *name;
+ __u16 kind;
+
+ /* for array members, we don't bother emitting type name for each
+ * member to avoid the redundancy of
+ * .name = (char[])[(char)'f',(char)'o',(char)'o',]
+ */
+ if (d->data.state.array_member)
+ return;
+
+ t = btf__type_by_id(d->btf, id);
+ kind = btf_kind(t);
+
+ /* avoid type name specification for variable/section; it will be done
+ * for the associated variable value(s). Also skip for function
+ * prototypes.
+ */
+ switch (kind) {
+ case BTF_KIND_VAR:
+ case BTF_KIND_DATASEC:
+ case BTF_KIND_FUNC_PROTO:hm... why skipping func_proto? seems useful when printing all kinds of opts struct?
+ return;
+ default:
+ break;
+ }
+
+ if (toplevel) {
+ if (fname && strlen(fname) > 0)
+ btf_dump_printf(d, ".%s = ", fname);
+ btf_dump_printf(d, "(");
+ }".field = " part is not really a type name, can't it be done outside?
quoted hunk ↗ jump to hunk
+ + switch (kind) { + case BTF_KIND_INT: + name = btf_name_of(d, t->name_off); + btf_dump_printf(d, "%s", name); + break; + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + name = btf_dump_type_name(d, id); + btf_dump_printf(d, "%s%s%s", + btf_is_struct(t) ? "struct" : "union", + strlen(name) > 0 ? " " : "", + name); + break; + case BTF_KIND_ENUM: + btf_dump_emit_enum_fwd(d, id, t); + break; + case BTF_KIND_TYPEDEF: + btf_dump_printf(d, "%s", btf_dump_ident_name(d, id)); + break; + case BTF_KIND_VOLATILE: + case BTF_KIND_CONST: + case BTF_KIND_RESTRICT: + /* modifiers are omitted from the cast to save space */ + btf_dump_emit_type_name(d, t->type, NULL, lvl, false); + break; + case BTF_KIND_PTR: + btf_dump_emit_type_name(d, t->type, NULL, lvl, false); + child = btf__type_by_id(d->btf, t->type); + btf_dump_printf(d, + btf_kind(child) == BTF_KIND_PTR ? "*" : " *"); + break; + case BTF_KIND_ARRAY: { + const struct btf_array *a = btf_array(t); + + btf_dump_emit_type_name(d, a->type, NULL, lvl, false); + btf_dump_printf(d, "[]"); + break; + } + default: + pr_warn("unexpected type when emitting type name, kind %u, id:[%u]\n", + kind, id); + break; + } + if (toplevel) + btf_dump_printf(d, ")"); +} + /* return number of duplicates (occurrences) of a given name */ static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map, const char *orig_name)@@ -1442,3 +1559,787 @@ static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id) { return btf_dump_resolve_name(d, id, d->ident_names); } + +static int btf_dump_dump_type_data(struct btf_dump *d, + const char *fname, + const struct btf_type *t, + __u32 id, + void *data, + __u8 bits_offset); + +static const char *btf_dump_data_newline(struct btf_dump *d) +{ + return d->data.compact ? "" : "\n"; +} + +static const char *btf_dump_data_delim(struct btf_dump *d) +{ + if (d->data.state.depth == 0) + return ""; + + return ",";
nit: use ternary like for newline?
+}
+
+static const char *btf_dump_data_pfx(struct btf_dump *d)
+{
+ int lvl = d->data.indent_lvl + d->data.state.depth;
+
+ if (d->data.compact)
+ lvl = 0;
+ return pfx(lvl);
+}
+
+/* A macro is used here as btf_type_value[s]() appends format specifiers
+ * to the format specifier passed in; these do the work of appending
+ * delimiters etc while the caller simply has to specify the type values
+ * in the format specifier + value(s).
+ */
+#define btf_dump_type_values(d, fmt, ...) \
+ btf_dump_printf(d, fmt "%s%s", \
+ __VA_ARGS__, \
+ btf_dump_data_delim(d), \
+ btf_dump_data_newline(d))
+
+static int btf_dump_df_data(struct btf_dump *d,what does "df" stand for?
+ const struct btf_type *t,
+ __u32 id,
+ void *data)
+{
+ btf_dump_printf(d, "<unsupported kind:%u>",
+ BTF_INFO_KIND(t->info));
+ return -ENOTSUP;
+}
+
+static void btf_dump_int128(struct btf_dump *d,
+ const struct btf_type *t,
+ void *data)
+{
+ /* data points to a __int128 number.
+ * Suppose
+ * int128_num = *(__int128 *)data;
+ * The below formulas shows what upper_num and lower_num represents:
+ * upper_num = int128_num >> 64;
+ * lower_num = int128_num & 0xffffffffFFFFFFFFULL;
+ */
+ __u64 upper_num, lower_num;
+
+#ifdef __BIG_ENDIAN_BITFIELD
+ upper_num = *(__u64 *)data;
+ lower_num = *(__u64 *)(data + 8);
+#else
+ upper_num = *(__u64 *)(data + 8);
+ lower_num = *(__u64 *)data;
+#endif
+ if (upper_num == 0)
+ btf_dump_type_values(d, "0x%llx", (long long)lower_num);
+ else
+ btf_dump_type_values(d, "0x%llx%016llx", (long long)upper_num,
+ (long long)lower_num);
+}
+
+static void btf_int128_shift(__u64 *print_num, __u16 left_shift_bits,
+ __u16 right_shift_bits)
+{
+ __u64 upper_num, lower_num;
+
+#ifdef __BIG_ENDIAN_BITFIELD
+ upper_num = print_num[0];
+ lower_num = print_num[1];
+#else
+ upper_num = print_num[1];
+ lower_num = print_num[0];
+#endif
+
+ /* shake out un-needed bits by shift/or operations */
+ if (left_shift_bits >= 64) {
+ upper_num = lower_num << (left_shift_bits - 64);
+ lower_num = 0;
+ } else {
+ upper_num = (upper_num << left_shift_bits) |
+ (lower_num >> (64 - left_shift_bits));
+ lower_num = lower_num << left_shift_bits;
+ }
+
+ if (right_shift_bits >= 64) {
+ lower_num = upper_num >> (right_shift_bits - 64);
+ upper_num = 0;
+ } else {
+ lower_num = (lower_num >> right_shift_bits) |
+ (upper_num << (64 - right_shift_bits));
+ upper_num = upper_num >> right_shift_bits;
+ }
+
+#ifdef __BIG_ENDIAN_BITFIELD
+ print_num[0] = upper_num;
+ print_num[1] = lower_num;
+#else
+ print_num[0] = lower_num;
+ print_num[1] = upper_num;
+#endif
+}
+
+static int btf_dump_bitfield_get_data(struct btf_dump *d,
+ void *data,
+ __u8 bits_offset,
+ __u8 nr_bits,
+ __u64 *print_num)
+{
+ __u16 left_shift_bits, right_shift_bits;
+ __u8 nr_copy_bytes;
+ __u8 nr_copy_bits;
+
+ nr_copy_bits = nr_bits + bits_offset;
+ nr_copy_bytes = BITS_ROUNDUP_BYTES(nr_copy_bits);
+
+ memcpy(print_num, data, nr_copy_bytes);
+
+#ifdef __BIG_ENDIAN_BITFIELD
+ left_shift_bits = bits_offset;
+#else
+ left_shift_bits = BITS_PER_U128 - nr_copy_bits;
+#endif
+ right_shift_bits = BITS_PER_U128 - nr_bits;
+
+ btf_int128_shift(print_num, left_shift_bits, right_shift_bits);
+
+ return 0;
+}
+
+static int btf_dump_bitfield_data(struct btf_dump *d,
+ const struct btf_type *t,
+ void *data,
+ __u8 bits_offset,
+ __u8 nr_bits)
+{
+ __u64 print_num[2] = {};
= {} is unnecessary as you always initialize it anyways?+
+ btf_dump_bitfield_get_data(d, data, bits_offset, nr_bits, print_num);
+ btf_dump_int128(d, t, print_num);
+
+ return 0;
+}
+
+static int btf_dump_int_bits(struct btf_dump *d,
+ const struct btf_type *t,
+ void *data,
+ __u8 bits_offset)
+{
+ __u8 nr_bits = d->data.state.bitfield_size ?: btf_int_bits(t);
+ __u8 total_bits_offset;
+
+ /*
+ * bits_offset is at most 7.
+ * BTF_INT_OFFSET() cannot exceed 128 bits.
+ */
+ total_bits_offset = bits_offset + btf_int_offset(t);BTF_INT_OFFSET() is long deprecated, pahole doesn't generate such INTs, many versions of Clang don't generate such int, so I don't think we should bother supporting it.
+ data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
+ bits_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
+ return btf_dump_bitfield_data(d, t, data, bits_offset, nr_bits);
+}
+
+static int btf_dump_int_bits_check_zero(struct btf_dump *d,
+ const struct btf_type *t,
+ void *data,
+ __u8 bits_offset)
+{
+ __u64 print_num[2], zero[2] = { };
+ __u8 nr_bits = d->data.state.bitfield_size ?: btf_int_bits(t);
+ __u8 total_bits_offset;
+
+ total_bits_offset = bits_offset + btf_int_offset(t);
+ data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
+ bits_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
+ btf_dump_bitfield_get_data(d, data, bits_offset, nr_bits,
+ (__u64 *)&print_num);
+ if (memcmp(print_num, zero, sizeof(zero)) == 0)
+ return -ENODATA;
+ return 0;
+}
+
+static int btf_dump_int_check_zero(struct btf_dump *d,
+ const struct btf_type *t,
+ void *data,
+ __u8 bits_offset)
+{
+ __u8 encoding = btf_int_encoding(t);
+ bool sign = encoding & BTF_INT_SIGNED;
+ __u8 nr_bits = btf_int_bits(t);
+ bool zero = false;
+
+ if (bits_offset || btf_int_offset(t) ||
+ BITS_PER_BYTE_MASKED(nr_bits))
+ return btf_dump_int_bits_check_zero(d, t, data, bits_offset);
+
+ switch (nr_bits) {
+ case 128:
+ zero = sign ? (*(__int128 *)data) == 0 :
+ (*(unsigned __int128 *)data) == 0;
+ break;
+ case 64:
+ zero = sign ? (*(__s64 *)data) == 0 :
+ (*(__u64 *)data) == 0;
+ break;
+ case 32:
+ zero = sign ? (*(__s32 *)data) == 0 :
+ (*(__u32 *)data) == 0;
+ break;
+ case 16:
+ zero = sign ? (*(__s16 *)data) == 0 :
+ (*(__u16 *)data) == 0;
+ break;
+ case 8:
+ zero = sign ? (*(__s8 *)data) == 0 :
+ (*(__u8 *)data) == 0;for zero checks sign doesn't matter
+ break;
+ default:
+ break;
+ }
+ if (zero)
+ return -ENODATA;
+ return 0;
+}
+
+static int btf_dump_int_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 type_id,
+ void *data,
+ __u8 bits_offset)
+{
+ __u8 encoding = btf_int_encoding(t);
+ bool sign = encoding & BTF_INT_SIGNED;
+ __u8 nr_bits = btf_int_bits(t);
+
+ if (bits_offset || btf_int_offset(t) ||
+ BITS_PER_BYTE_MASKED(nr_bits))
+ return btf_dump_int_bits(d, t, data, bits_offset);
+
+ switch (nr_bits) {
+ case 128:
+ btf_dump_int128(d, t, data);
+ break;
+ case 64:
+ if (sign)
+ btf_dump_type_values(d, "%lld", *(long long *)data);
+ else
+ btf_dump_type_values(d, "%llu",
+ *(unsigned long long *)data);
+ break;
+ case 32:
+ if (sign)
+ btf_dump_type_values(d, "%d", *(__s32 *)data);
+ else
+ btf_dump_type_values(d, "%u", *(__u32 *)data);
+ break;
+ case 16:
+ if (sign)
+ btf_dump_type_values(d, "%d", *(__s16 *)data);
+ else
+ btf_dump_type_values(d, "%u", *(__u16 *)data);
+ break;
+ case 8:
+ if (d->data.state.array_ischar) {
+ /* check for null terminator */
+ if (d->data.state.array_terminated)
+ break;
+ if (*(char *)data == '\0') {
+ d->data.state.array_terminated = 1;
+ break;
+ }
+ if (isprint(*(char *)data)) {
+ btf_dump_type_values(d, "'%c'",
+ *(char *)data);
+ break;
+ }
+ }
+ if (sign)
+ btf_dump_type_values(d, "%d", *(__s8 *)data);
+ else
+ btf_dump_type_values(d, "%u", *(__u8 *)data);
+ break;
+ default:
+ return btf_dump_int_bits(d, t, data, bits_offset);error out in such case?
+ }
+ return 0;
+}
+
+static int btf_dump_var_data(struct btf_dump *d,
+ const struct btf_type *v,
+ __u32 id,
+ void *data)
+{
+ enum btf_func_linkage linkage = btf_var(v)->linkage;
+ const struct btf_type *t;
+ const char *l = "";
+ __u32 type_id;
+
+ switch (linkage) {
+ case BTF_FUNC_STATIC:
+ l = "static ";
+ break;
+ case BTF_FUNC_EXTERN:
+ l = "extern ";
+ break;
+ case BTF_FUNC_GLOBAL:
+ default:
+ break;
+ }
+
+ /* format of output here is [linkage] [type] [varname] = (type)value,
+ * for example "static int cpu_profile_flip = (int)1"
+ */
+ btf_dump_printf(d, "%s", l);
+ type_id = v->type;
+ t = btf__type_by_id(d->btf, type_id);
+ btf_dump_emit_type_name(d, type_id, NULL, 0, false);
+ btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off));
+ return btf_dump_dump_type_data(d, NULL,
+ t, type_id, data, 0);
+}
+
+static int btf_dump_array_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ void *data)
+{
+ const struct btf_array *array = btf_array(t);
+ const struct btf_type *elem_type;
+ __u32 i, elem_size = 0, elem_type_id;
+ int array_member;
+
+ elem_type_id = array->type;
+ elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
+ if (!elem_type) {can't really happen in well-formed BTF, I don't think libbpf ever checks this for NULL
+ pr_warn("unexpected error skipping mods/typedefs for id [%u]\n",
+ elem_type_id);
+ return -EINVAL;
+ }
+ elem_size = btf__resolve_size(d->btf, elem_type_id);this can actually fail and return -Exxx, so I'd check <= 0 case here, otherwise it might get confusing later
+
+ if (elem_type && btf_is_int(elem_type)) {
+ /*
+ * BTF_INT_CHAR encoding never seems to be set for
+ * char arrays, so if size is 1 and element is
+ * printable as a char, we'll do that.
+ */
+ if (elem_size == 1)
+ d->data.state.array_ischar = true;
+ }
+
+ if (!elem_type)
+ return 0;already checked above
+ + btf_dump_printf(d, "[%s", + btf_dump_data_newline(d));
nit: keep on single line, it's not that long
+ d->data.state.depth++; + + /* may be a multidimemsional array, so store current "is array member"
typo: multidimensional
+ * status so we can restore it correctly later.
+ */
+ array_member = d->data.state.array_member;
+ d->data.state.array_member = 1;
+ for (i = 0; i < array->nelems && !d->data.state.array_terminated; i++) {
+
+ btf_dump_dump_type_data(d, NULL, elem_type, elem_type_id,
+ data, 0);
+ data += elem_size;
+ }
+ d->data.state.array_member = array_member;
+ d->data.state.depth--;
+ btf_dump_printf(d, "%s]%s%s",
+ btf_dump_data_pfx(d),
+ btf_dump_data_delim(d),
+ btf_dump_data_newline(d));
+
+ return 0;
+}
+
+static int btf_dump_struct_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ void *data)
+{
+ const struct btf_member *member;
+ __u32 i;
+ int err;
+
+ btf_dump_printf(d, "{%s",
+ btf_dump_data_newline(d));
+ d->data.state.depth++;
+ for (i = 0, member = btf_members(t);
+ i < btf_vlen(t);
+ i++, member++) {
+ const struct btf_type *member_type;
+ __u32 bytes_offset, member_offset;
+ const char *member_name;
+ __u8 bits8_offset;
+
+ member_type = btf__type_by_id(d->btf, member->type);
+ member_name = btf_name_of(d, member->name_off);
+ member_offset = btf_member_bit_offset(t, i);
+ bytes_offset = BITS_ROUNDDOWN_BYTES(member_offset);
+ bits8_offset = BITS_PER_BYTE_MASKED(member_offset);
+
+ /* btf_int_bits() does not store member bitfield size;
+ * bitfield size needs to be stored here so int display
+ * of member can retrieve it.
+ */
+ d->data.state.bitfield_size =
+ btf_member_bitfield_size(t, i);
+ err = btf_dump_dump_type_data(d,
+ member_name,
+ member_type,
+ member->type,
+ data + bytes_offset,
+ bits8_offset);
+ d->data.state.bitfield_size = 0;
+ if (err)
+ return err;
+ }
+ d->data.state.depth--;
+ btf_dump_printf(d, "%s}%s%s",
+ btf_dump_data_pfx(d),
+ btf_dump_data_delim(d),
+ btf_dump_data_newline(d));
+ return err;
+}
+
+static int btf_dump_ptr_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ void *data)
+{
+ btf_dump_type_values(d, "%p", *(void **)data);
+ return 0;
+}
+
+static int btf_dump_get_enum_value(const struct btf_type *t,
+ void *data,
+ __u32 id,
+ __s64 *value)
+{
+ switch (t->size) {
+ case 8:
+ *value = *(__s64 *)data;
+ return 0;
+ case 4:
+ *value = *(__s32 *)data;
+ return 0;
+ case 2:
+ *value = *(__s16 *)data;
+ return 0;
+ case 1:
+ *value = *(__s8 *)data;
+ default:
+ pr_warn("unexpected size %d for enum, id:[%u]\n",
+ t->size, id);
+ return -EINVAL;
+ }
+}
+
+static int btf_dump_enum_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ void *data)
+{
+ const struct btf_enum *e;
+ __s64 value;
+ int i, err;
+
+ err = btf_dump_get_enum_value(t, data, id, &value);
+ if (err)
+ return err;
+
+ for (i = 0, e = btf_enum(t); i < btf_vlen(t); i++, e++) {
+ if (value != e->val)
+ continue;
+ btf_dump_type_values(d, "%s",
+ btf_name_of(d, e->name_off));
+ return 0;
+ }
+
+ btf_dump_type_values(d, "%d", value);
+ return 0;
+}
+
+static int btf_dump_datasec_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ void *data)
+{
+ const struct btf_var_secinfo *vsi;
+ const struct btf_type *var;
+ __u32 i;
+ int err;
+
+ btf_dump_type_values(d, "SEC(\"%s\") ",
+ btf_name_of(d, t->name_off));
+ for (i = 0, vsi = btf_var_secinfos(t);
+ i < btf_vlen(t);
+ i++, vsi++) {
+ var = btf__type_by_id(d->btf, vsi->type);
+ err = btf_dump_dump_type_data(d, NULL, var,
+ vsi->type,
+ data + vsi->offset,
+ 0);
+ if (err)
+ return err;
+ btf_dump_printf(d, ";");
+ }
+ return 0;
+}
+
+static int btf_dump_type_data_check_overflow(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ void *data,
+ __u8 bits_offset)
+{
+ __s64 size;
+
+ /* Only do overflow checking for base types; we do not want to
+ * avoid showing part of a struct, union or array, even if we
+ * do not have enough data to show the full object. By
+ * restricting overflow checking to base types we can ensure
+ * that partial display succeeds, while avoiding overflowing
+ * and using bogus data for display.
+ */
+ t = skip_mods_and_typedefs(d->btf, id, NULL);
+ if (!t) {
+ pr_warn("unexpected error skipping mods/typedefs for id [%u]\n",
+ id);
+ return -EINVAL;
+ }
+
+ switch (BTF_INFO_KIND(t->info)) {
+ case BTF_KIND_INT:
+ case BTF_KIND_PTR:
+ case BTF_KIND_ENUM:
+ size = btf__resolve_size(d->btf, id);
+ if (size < 0) {
+ pr_warn("unexpected size [%llu] for id [%u]\n",
+ size, id);
+ return -EINVAL;
+ }
+ if (data + (bits_offset >> 3) + size > d->data.data_end)bits_offset / 8... and considering you have a whole dedicated BITS_PER_BYTE (btw, why?.. are we expecting it to ever change?), it's surprising to see bit shifts instead of division
+ return -E2BIG;
+ return 0;
+ default:
+ return 0;
+ }
+}
+
+static int btf_dump_type_data_check_zero(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ void *data,
+ __u8 bits_offset)
+{
+ __s64 value;
+ int i, err;
+
+ /* toplevel exceptions; we show zero values if
+ * - we ask for them (emit_zeros)
+ * - if we are at top-level so we see "struct empty { }"
+ * - or if we are an array member and the array is non-empty and
+ * not a char array; we don't want to be in a situation where we
+ * have an integer array 0, 1, 0, 1 and only show non-zero values.
+ * If the array contains zeroes only, or is a char array starting
+ * with a '\0', the array-level check_zero() will prevent showing it;
+ * we are concerned with determining zero value at the array member
+ * level here.
+ */
+ if (d->data.emit_zeroes || d->data.state.depth == 0 ||
+ (d->data.state.array_member && !d->data.state.array_ischar))
+ return 0;
+
+ t = skip_mods_and_typedefs(d->btf, id, NULL);
+ if (!t) {don't check, if anything btf_dump_type_data_check_overflow() already validated that it's ok
+ pr_warn("unexpected error skipping mods/typedefs for id [%u]\n",
+ id);
+ return -EINVAL;
+ }
+
+
+ switch (BTF_INFO_KIND(t->info)) {
+ case BTF_KIND_INT:
+ if (d->data.state.bitfield_size)
+ return btf_dump_int_bits_check_zero(d, t, data,
+ bits_offset);
+ return btf_dump_int_check_zero(d, t, data, bits_offset);
+ case BTF_KIND_PTR:
+ if (*((void **)data) == NULL)
+ return -ENODATA;
+ return 0;
+ case BTF_KIND_ARRAY: {
+ const struct btf_array *array = btf_array(t);
+ const struct btf_type *elem_type;
+ __u32 elem_type_id, elem_size;
+ bool ischar;
+
+ elem_type_id = array->type;
+ elem_size = btf__resolve_size(d->btf, elem_type_id);
+ elem_type = btf__type_by_id(d->btf, elem_type_id);
+
+ ischar = btf_is_int(elem_type) && elem_size == 1;
+
+ /* check all elements; if _any_ element is nonzero, all
+ * of array is displayed. We make an exception however
+ * for char arrays where the first element is 0; these
+ * are considered zeroed also, even if later elements are
+ * non-zero because the string is terminated.
+ */
+ for (i = 0; i < array->nelems; i++) {
+ if (i == 0 && ischar && *(char *)data == 0)
+ return -ENODATA;
+ err = btf_dump_type_data_check_zero(d, elem_type,
+ elem_type_id,
+ data +
+ (i * elem_size),
+ bits_offset);
+ if (err != -ENODATA)
+ return err;
+ }
+ return -ENODATA;
+ }
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION: {
+ const struct btf_member *member;
+
+ /* if any struct/union member is non-zero, the struct/union
+ * is considered non-zero and dumped.
+ */
+ for (i = 0, member = btf_members(t);
+ i < btf_vlen(t);
+ i++, member++) {
in a lot of other places in libbpf we use more succinct names and this pattern
n = btf_vlen(t);
m = btf_members(t);
for (i = 0; i < n; i++, m++) {
it's nice, short, and familiar in libbpf code base
+ const struct btf_type *member_type;
+ __u32 bytes_offset, member_offset;
+ __u8 bits8_offset;
+
+ member_type = btf__type_by_id(d->btf, member->type);
+ member_offset = btf_member_bit_offset(t, i);
+ bytes_offset = BITS_ROUNDDOWN_BYTES(member_offset);
+ bits8_offset = BITS_PER_BYTE_MASKED(member_offset);
+
+ /* btf_int_bits() does not store member bitfield size;
+ * bitfield size needs to be stored here so int display
+ * of member can retrieve it.
+ */
+ d->data.state.bitfield_size =
+ btf_member_bitfield_size(t, i);
+
+ err = btf_dump_type_data_check_zero(d, member_type,
+ member->type,
+ data + bytes_offset,
+ bits8_offset);
+ d->data.state.bitfield_size = 0;
+ if (err != ENODATA)
+ return err;
+ }
+ return -ENODATA;
+ }
+ case BTF_KIND_ENUM:
+ if (btf_dump_get_enum_value(t, data, id, &value))
+ return 0;
+ if (value == 0)
+ return -ENODATA;
+ return 0;
+ default:
+ return 0;
+ }
+}
+
+static int btf_dump_dump_type_data(struct btf_dump *d,
+ const char *fname,
+ const struct btf_type *t,
+ __u32 id,
+ void *data,
+ __u8 bits_offset)
+{
+ int err;
+
+ err = btf_dump_type_data_check_overflow(d, t, id, data, bits_offset);
+ if (err)
+ return err;
+ err = btf_dump_type_data_check_zero(d, t, id, data, bits_offset);
+ if (err) {
+ /* zeroed data is expected and not an error, so simply skip
+ * dumping such data. Record other errors however.
+ */
+ if (err == -ENODATA)
+ return 0;
+ return err;
+ }
+ btf_dump_printf(d, "%s", btf_dump_data_pfx(d));
+ if (!d->data.skip_names)
+ btf_dump_emit_type_name(d, id, fname, 0, true);
+
+ t = skip_mods_and_typedefs(d->btf, id, NULL);
+ if (!t) {
+ pr_warn("unexpected error skipping mods/typedefs for id [%u]\n",
+ id);
+ return -EINVAL;
+ }
+
+ switch (BTF_INFO_KIND(t->info)) {
+ case BTF_KIND_UNKN:
+ case BTF_KIND_FWD:
+ case BTF_KIND_FUNC:
+ case BTF_KIND_FUNC_PROTO:
+ return btf_dump_df_data(d, t, id, data);
+ case BTF_KIND_INT:
+ if (d->data.state.bitfield_size)btw, enum can be part of bitfields as well
+ return btf_dump_bitfield_data(d, t, data, + bits_offset, + d->data.state.bitfield_size); + return btf_dump_int_data(d, t, id, data, bits_offset); + case BTF_KIND_PTR: + return btf_dump_ptr_data(d, t, id, data); + case BTF_KIND_ARRAY: + return btf_dump_array_data(d, t, id, data); + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + return btf_dump_struct_data(d, t, id, data); + case BTF_KIND_ENUM: + return btf_dump_enum_data(d, t, id, data); + case BTF_KIND_VAR: + return btf_dump_var_data(d, t, id, data); + case BTF_KIND_DATASEC: + return btf_dump_datasec_data(d, t, id, data); + default:
since last time we also added BTF_KIND_FLOAT
+ pr_warn("unexpected kind [%u] for id [%u]\n",
+ BTF_INFO_KIND(t->info), id);
+ return -EINVAL;
+ }
+}
+
+int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
+ void *data, size_t byte_sz,
+ const struct btf_dump_type_data_opts *opts)
+{
+ const struct btf_type *t;
+ int err;
+
+ if (!OPTS_VALID(opts, btf_dump_type_data_opts))
+ return -EINVAL;
+
+ t = btf__type_by_id(d->btf, id);
+ if (!t)
+ return -ENOENT;public APIs should use libbpf_err() to ensure errno is set properly, see my recent patch set. This should be return libbpf_err(-ENOENT);
+ + d->data.data_end = data + byte_sz; + d->data.indent_lvl = OPTS_GET(opts, indent_level, 0); + d->data.compact = OPTS_GET(opts, compact, false); + d->data.skip_names = OPTS_GET(opts, skip_names, false); + d->data.emit_zeroes = OPTS_GET(opts, emit_zeroes, false); + memset(&d->data.state, 0, sizeof(d->data.state)); + + err = btf_dump_dump_type_data(d, NULL, t, id, data, 0); + + /* We reported all the data; return size of data we reported. */ + if (err == 0) + err = btf__resolve_size(d->btf, id);
hm.. why can't btf_dump_dump_type_data() return the consumed amount of bytes?
quoted hunk ↗ jump to hunk
+ + memset(&d->data, 0, sizeof(d->data)); + + return err; +}diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 0229e01..76cfac6 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map@@ -370,3 +370,8 @@ LIBBPF_0.4.0 { bpf_tc_hook_destroy; bpf_tc_query; } LIBBPF_0.3.0; + +LIBBPF_0.5.0 { + global: + btf_dump__dump_type_data; +} LIBBPF_0.4.0; --1.8.3.1