From: Andrii Nakryiko <andriin@fb.com>
Date: Tue, 18 Aug 2020 15:39:14 -0700
Subject: libbpf: Clean up and improve CO-RE reloc logging
Patch-mainline: v5.10-rc1
Git-commit: 28b93c64499ae09d9dc8c04123b15f8654a93c4c
References: bsc#1177028
Add logging of local/target type kind (struct/union/typedef/etc). Preserve
unresolved root type ID (for cases of typedef). Improve the format of CO-RE
reloc spec output format to contain only relevant and succinct info.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200818223921.2911963-3-andriin@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
tools/lib/bpf/btf.c | 17 +---
tools/lib/bpf/btf.h | 38 --------
tools/lib/bpf/libbpf.c | 169 ++++++++++++++++++++++++----------------
tools/lib/bpf/libbpf_internal.h | 78 +++++++++++++-----
4 files changed, 171 insertions(+), 131 deletions(-)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1137,14 +1137,14 @@ static int btf_ext_setup_line_info(struc
return btf_ext_setup_info(btf_ext, ¶m);
}
-static int btf_ext_setup_field_reloc(struct btf_ext *btf_ext)
+static int btf_ext_setup_core_relos(struct btf_ext *btf_ext)
{
struct btf_ext_sec_setup_param param = {
- .off = btf_ext->hdr->field_reloc_off,
- .len = btf_ext->hdr->field_reloc_len,
- .min_rec_size = sizeof(struct bpf_field_reloc),
- .ext_info = &btf_ext->field_reloc_info,
- .desc = "field_reloc",
+ .off = btf_ext->hdr->core_relo_off,
+ .len = btf_ext->hdr->core_relo_len,
+ .min_rec_size = sizeof(struct bpf_core_relo),
+ .ext_info = &btf_ext->core_relo_info,
+ .desc = "core_relo",
};
return btf_ext_setup_info(btf_ext, ¶m);
@@ -1223,10 +1223,9 @@ struct btf_ext *btf_ext__new(__u8 *data,
if (err)
goto done;
- if (btf_ext->hdr->hdr_len <
- offsetofend(struct btf_ext_header, field_reloc_len))
+ if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len))
goto done;
- err = btf_ext_setup_field_reloc(btf_ext);
+ err = btf_ext_setup_core_relos(btf_ext);
if (err)
goto done;
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -24,44 +24,6 @@ struct btf_type;
struct bpf_object;
-/*
- * The .BTF.ext ELF section layout defined as
- * struct btf_ext_header
- * func_info subsection
- *
- * The func_info subsection layout:
- * record size for struct bpf_func_info in the func_info subsection
- * struct btf_sec_func_info for section #1
- * a list of bpf_func_info records for section #1
- * where struct bpf_func_info mimics one in include/uapi/linux/bpf.h
- * but may not be identical
- * struct btf_sec_func_info for section #2
- * a list of bpf_func_info records for section #2
- * ......
- *
- * Note that the bpf_func_info record size in .BTF.ext may not
- * be the same as the one defined in include/uapi/linux/bpf.h.
- * The loader should ensure that record_size meets minimum
- * requirement and pass the record as is to the kernel. The
- * kernel will handle the func_info properly based on its contents.
- */
-struct btf_ext_header {
- __u16 magic;
- __u8 version;
- __u8 flags;
- __u32 hdr_len;
-
- /* All offsets are in bytes relative to the end of this header */
- __u32 func_info_off;
- __u32 func_info_len;
- __u32 line_info_off;
- __u32 line_info_len;
-
- /* optional part of .BTF.ext header */
- __u32 field_reloc_off;
- __u32 field_reloc_len;
-};
-
LIBBPF_API void btf__free(struct btf *btf);
LIBBPF_API struct btf *btf__new(const void *data, __u32 size);
LIBBPF_API struct btf *btf__parse(const char *path, struct btf_ext **btf_ext);
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2522,7 +2522,7 @@ static int bpf_object__load_vmlinux_btf(
int err;
/* CO-RE relocations need kernel BTF */
- if (obj->btf_ext && obj->btf_ext->field_reloc_info.len)
+ if (obj->btf_ext && obj->btf_ext->core_relo_info.len)
need_vmlinux_btf = true;
bpf_object__for_each_program(prog, obj) {
@@ -4047,6 +4047,10 @@ struct bpf_core_spec {
const struct btf *btf;
/* high-level spec: named fields and array indices only */
struct bpf_core_accessor spec[BPF_CORE_SPEC_MAX_LEN];
+ /* original unresolved (no skip_mods_or_typedefs) root type ID */
+ __u32 root_type_id;
+ /* CO-RE relocation kind */
+ enum bpf_core_relo_kind relo_kind;
/* high-level spec length */
int len;
/* raw, low-level spec: 1-to-1 with accessor spec string */
@@ -4077,8 +4081,36 @@ static bool is_flex_arr(const struct btf
return acc->idx == btf_vlen(t) - 1;
}
+static const char *core_relo_kind_str(enum bpf_core_relo_kind kind)
+{
+ switch (kind) {
+ case BPF_FIELD_BYTE_OFFSET: return "byte_off";
+ case BPF_FIELD_BYTE_SIZE: return "byte_sz";
+ case BPF_FIELD_EXISTS: return "field_exists";
+ case BPF_FIELD_SIGNED: return "signed";
+ case BPF_FIELD_LSHIFT_U64: return "lshift_u64";
+ case BPF_FIELD_RSHIFT_U64: return "rshift_u64";
+ default: return "unknown";
+ }
+}
+
+static bool core_relo_is_field_based(enum bpf_core_relo_kind kind)
+{
+ switch (kind) {
+ case BPF_FIELD_BYTE_OFFSET:
+ case BPF_FIELD_BYTE_SIZE:
+ case BPF_FIELD_EXISTS:
+ case BPF_FIELD_SIGNED:
+ case BPF_FIELD_LSHIFT_U64:
+ case BPF_FIELD_RSHIFT_U64:
+ return true;
+ default:
+ return false;
+ }
+}
+
/*
- * Turn bpf_field_reloc into a low- and high-level spec representation,
+ * Turn bpf_core_relo into a low- and high-level spec representation,
* validating correctness along the way, as well as calculating resulting
* field bit offset, specified by accessor string. Low-level spec captures
* every single level of nestedness, including traversing anonymous
@@ -4108,9 +4140,10 @@ static bool is_flex_arr(const struct btf
* - array element #3 access (corresponds to '3' in low-level spec).
*
*/
-static int bpf_core_spec_parse(const struct btf *btf,
+static int bpf_core_parse_spec(const struct btf *btf,
__u32 type_id,
const char *spec_str,
+ enum bpf_core_relo_kind relo_kind,
struct bpf_core_spec *spec)
{
int access_idx, parsed_len, i;
@@ -4125,6 +4158,8 @@ static int bpf_core_spec_parse(const str
memset(spec, 0, sizeof(*spec));
spec->btf = btf;
+ spec->root_type_id = type_id;
+ spec->relo_kind = relo_kind;
/* parse spec_str="0:1:2:3:4" into array raw_spec=[0, 1, 2, 3, 4] */
while (*spec_str) {
@@ -4151,6 +4186,9 @@ static int bpf_core_spec_parse(const str
spec->spec[0].idx = access_idx;
spec->len++;
+ if (!core_relo_is_field_based(relo_kind))
+ return -EINVAL;
+
sz = btf__resolve_size(btf, id);
if (sz < 0)
return sz;
@@ -4258,17 +4296,17 @@ static struct ids_vec *bpf_core_find_can
const struct btf *targ_btf)
{
size_t local_essent_len, targ_essent_len;
- const char *local_name, *targ_name;
- const struct btf_type *t;
+ const char *local_name, *targ_name, *targ_kind;
+ const struct btf_type *t, *local_t;
struct ids_vec *cand_ids;
__u32 *new_ids;
int i, err, n;
- t = btf__type_by_id(local_btf, local_type_id);
- if (!t)
+ local_t = btf__type_by_id(local_btf, local_type_id);
+ if (!local_t)
return ERR_PTR(-EINVAL);
- local_name = btf__name_by_offset(local_btf, t->name_off);
+ local_name = btf__name_by_offset(local_btf, local_t->name_off);
if (str_is_empty(local_name))
return ERR_PTR(-EINVAL);
local_essent_len = bpf_core_essential_name_len(local_name);
@@ -4283,6 +4321,7 @@ static struct ids_vec *bpf_core_find_can
targ_name = btf__name_by_offset(targ_btf, t->name_off);
if (str_is_empty(targ_name))
continue;
+ targ_kind = btf_kind_str(t);
t = skip_mods_and_typedefs(targ_btf, i, NULL);
if (!btf_is_composite(t) && !btf_is_array(t))
@@ -4293,8 +4332,9 @@ static struct ids_vec *bpf_core_find_can
continue;
if (strncmp(local_name, targ_name, local_essent_len) == 0) {
- pr_debug("[%d] %s: found candidate [%d] %s\n",
- local_type_id, local_name, i, targ_name);
+ pr_debug("CO-RE relocating [%d] %s %s: found target candidate [%d] %s %s\n",
+ local_type_id, btf_kind_str(local_t),
+ local_name, i, targ_kind, targ_name);
new_ids = reallocarray(cand_ids->data,
cand_ids->len + 1,
sizeof(*cand_ids->data));
@@ -4483,6 +4523,8 @@ static int bpf_core_spec_match(struct bp
memset(targ_spec, 0, sizeof(*targ_spec));
targ_spec->btf = targ_btf;
+ targ_spec->root_type_id = targ_id;
+ targ_spec->relo_kind = local_spec->relo_kind;
local_acc = &local_spec->spec[0];
targ_acc = &targ_spec->spec[0];
@@ -4543,7 +4585,7 @@ static int bpf_core_spec_match(struct bp
}
static int bpf_core_calc_field_relo(const struct bpf_program *prog,
- const struct bpf_field_reloc *relo,
+ const struct bpf_core_relo *relo,
const struct bpf_core_spec *spec,
__u32 *val, bool *validate)
{
@@ -4664,7 +4706,7 @@ static int bpf_core_calc_field_relo(cons
* 2. rX += <imm> (arithmetic operations with immediate operand);
*/
static int bpf_core_reloc_insn(struct bpf_program *prog,
- const struct bpf_field_reloc *relo,
+ const struct bpf_core_relo *relo,
int relo_idx,
const struct bpf_core_spec *local_spec,
const struct bpf_core_spec *targ_spec)
@@ -4768,25 +4810,30 @@ static void bpf_core_dump_spec(int level
__u32 type_id;
int i;
- type_id = spec->spec[0].type_id;
+ type_id = spec->root_type_id;
t = btf__type_by_id(spec->btf, type_id);
s = btf__name_by_offset(spec->btf, t->name_off);
- libbpf_print(level, "[%u] %s + ", type_id, s);
- for (i = 0; i < spec->raw_len; i++)
- libbpf_print(level, "%d%s", spec->raw_spec[i],
- i == spec->raw_len - 1 ? " => " : ":");
-
- libbpf_print(level, "%u.%u @ &x",
- spec->bit_offset / 8, spec->bit_offset % 8);
-
- for (i = 0; i < spec->len; i++) {
- if (spec->spec[i].name)
- libbpf_print(level, ".%s", spec->spec[i].name);
+ libbpf_print(level, "[%u] %s %s", type_id, btf_kind_str(t), str_is_empty(s) ? "<anon>" : s);
+
+ if (core_relo_is_field_based(spec->relo_kind)) {
+ for (i = 0; i < spec->len; i++) {
+ if (spec->spec[i].name)
+ libbpf_print(level, ".%s", spec->spec[i].name);
+ else if (i > 0 || spec->spec[i].idx > 0)
+ libbpf_print(level, "[%u]", spec->spec[i].idx);
+ }
+
+ libbpf_print(level, " (");
+ for (i = 0; i < spec->raw_len; i++)
+ libbpf_print(level, "%s%d", i == 0 ? "" : ":", spec->raw_spec[i]);
+
+ if (spec->bit_offset % 8)
+ libbpf_print(level, " @ offset %u.%u)",
+ spec->bit_offset / 8, spec->bit_offset % 8);
else
- libbpf_print(level, "[%u]", spec->spec[i].idx);
+ libbpf_print(level, " @ offset %u)", spec->bit_offset / 8);
}
-
}
static size_t bpf_core_hash_fn(const void *key, void *ctx)
@@ -4850,12 +4897,12 @@ static void *u32_as_hash_key(__u32 x)
* CPU-wise compared to prebuilding a map from all local type names to
* a list of candidate type names. It's also sped up by caching resolved
* list of matching candidates per each local "root" type ID, that has at
- * least one bpf_field_reloc associated with it. This list is shared
+ * least one bpf_core_relo associated with it. This list is shared
* between multiple relocations for the same type ID and is updated as some
* of the candidates are pruned due to structural incompatibility.
*/
static int bpf_core_reloc_field(struct bpf_program *prog,
- const struct bpf_field_reloc *relo,
+ const struct bpf_core_relo *relo,
int relo_idx,
const struct btf *local_btf,
const struct btf *targ_btf,
@@ -4864,8 +4911,8 @@ static int bpf_core_reloc_field(struct b
const char *prog_name = bpf_program__title(prog, false);
struct bpf_core_spec local_spec, cand_spec, targ_spec;
const void *type_key = u32_as_hash_key(relo->type_id);
- const struct btf_type *local_type, *cand_type;
- const char *local_name, *cand_name;
+ const struct btf_type *local_type;
+ const char *local_name;
struct ids_vec *cand_ids;
__u32 local_id, cand_id;
const char *spec_str;
@@ -4884,24 +4931,24 @@ static int bpf_core_reloc_field(struct b
if (str_is_empty(spec_str))
return -EINVAL;
- err = bpf_core_spec_parse(local_btf, local_id, spec_str, &local_spec);
+ err = bpf_core_parse_spec(local_btf, local_id, spec_str, relo->kind, &local_spec);
if (err) {
- pr_warning("prog '%s': relo #%d: parsing [%d] %s + %s failed: %d\n",
- prog_name, relo_idx, local_id, local_name, spec_str,
- err);
+ pr_warning("prog '%s': relo #%d: parsing [%d] %s %s + %s failed: %d\n",
+ prog_name, relo_idx, local_id, btf_kind_str(local_type),
+ local_name, spec_str, err);
return -EINVAL;
}
- pr_debug("prog '%s': relo #%d: kind %d, spec is ", prog_name, relo_idx,
- relo->kind);
+ pr_debug("prog '%s': relo #%d: kind <%s> (%d), spec is ", prog_name,
+ relo_idx, core_relo_kind_str(relo->kind), relo->kind);
bpf_core_dump_spec(LIBBPF_DEBUG, &local_spec);
libbpf_print(LIBBPF_DEBUG, "\n");
if (!hashmap__find(cand_cache, type_key, (void **)&cand_ids)) {
cand_ids = bpf_core_find_cands(local_btf, local_id, targ_btf);
if (IS_ERR(cand_ids)) {
- pr_warning("prog '%s': relo #%d: target candidate search failed for [%d] %s: %ld",
- prog_name, relo_idx, local_id, local_name,
+ pr_warning("prog '%s': relo #%d: target candidate search failed for [%d] %s %s: %ld",
+ prog_name, relo_idx, local_id, btf_kind_str(local_type), local_name,
PTR_ERR(cand_ids));
return PTR_ERR(cand_ids);
}
@@ -4914,20 +4961,20 @@ static int bpf_core_reloc_field(struct b
for (i = 0, j = 0; i < cand_ids->len; i++) {
cand_id = cand_ids->data[i];
- cand_type = btf__type_by_id(targ_btf, cand_id);
- cand_name = btf__name_by_offset(targ_btf, cand_type->name_off);
-
- err = bpf_core_spec_match(&local_spec, targ_btf,
- cand_id, &cand_spec);
- pr_debug("prog '%s': relo #%d: matching candidate #%d %s against spec ",
- prog_name, relo_idx, i, cand_name);
- bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
- libbpf_print(LIBBPF_DEBUG, ": %d\n", err);
+ err = bpf_core_spec_match(&local_spec, targ_btf, cand_id, &cand_spec);
if (err < 0) {
- pr_warning("prog '%s': relo #%d: matching error: %d\n",
- prog_name, relo_idx, err);
+ pr_warning("prog '%s': relo #%d: error matching candidate #%d ",
+ prog_name, relo_idx, i);
+ bpf_core_dump_spec(LIBBPF_WARN, &cand_spec);
+ libbpf_print(LIBBPF_WARN, ": %d\n", err);
return err;
}
+
+ pr_debug("prog '%s': relo #%d: %s candidate #%d ", prog_name,
+ relo_idx, err == 0 ? "non-matching" : "matching", i);
+ bpf_core_dump_spec(LIBBPF_DEBUG, &cand_spec);
+ libbpf_print(LIBBPF_DEBUG, "\n");
+
if (err == 0)
continue;
@@ -4969,8 +5016,8 @@ static int bpf_core_reloc_field(struct b
* to a specific instruction number in its log.
*/
if (j == 0)
- pr_debug("prog '%s': relo #%d: no matching targets found for [%d] %s + %s\n",
- prog_name, relo_idx, local_id, local_name, spec_str);
+ pr_debug("prog '%s': relo #%d: no matching targets found\n",
+ prog_name, relo_idx);
/* bpf_core_reloc_insn should know how to handle missing targ_spec */
err = bpf_core_reloc_insn(prog, relo, relo_idx, &local_spec,
@@ -4985,10 +5032,10 @@ static int bpf_core_reloc_field(struct b
}
static int
-bpf_core_reloc_fields(struct bpf_object *obj, const char *targ_btf_path)
+bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
{
const struct btf_ext_info_sec *sec;
- const struct bpf_field_reloc *rec;
+ const struct bpf_core_relo *rec;
const struct btf_ext_info *seg;
struct hashmap_entry *entry;
struct hashmap *cand_cache = NULL;
@@ -4997,6 +5044,9 @@ bpf_core_reloc_fields(struct bpf_object
const char *sec_name;
int i, err = 0;
+ if (obj->btf_ext->core_relo_info.len == 0)
+ return 0;
+
if (targ_btf_path)
targ_btf = btf__parse_elf(targ_btf_path, NULL);
else
@@ -5013,7 +5063,7 @@ bpf_core_reloc_fields(struct bpf_object
goto out;
}
- seg = &obj->btf_ext->field_reloc_info;
+ seg = &obj->btf_ext->core_relo_info;
for_each_btf_ext_sec(seg, sec) {
sec_name = btf__name_by_offset(obj->btf, sec->sec_name_off);
if (str_is_empty(sec_name)) {
@@ -5061,17 +5111,6 @@ out:
return err;
}
-static int
-bpf_object__relocate_core(struct bpf_object *obj, const char *targ_btf_path)
-{
- int err = 0;
-
- if (obj->btf_ext->field_reloc_info.len)
- err = bpf_core_reloc_fields(obj, targ_btf_path);
-
- return err;
-}
-
static int
bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
struct reloc_desc *relo)
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -138,6 +138,44 @@ struct btf_ext_info {
i < (sec)->num_info; \
i++, rec = (void *)rec + (seg)->rec_size)
+/*
+ * The .BTF.ext ELF section layout defined as
+ * struct btf_ext_header
+ * func_info subsection
+ *
+ * The func_info subsection layout:
+ * record size for struct bpf_func_info in the func_info subsection
+ * struct btf_sec_func_info for section #1
+ * a list of bpf_func_info records for section #1
+ * where struct bpf_func_info mimics one in include/uapi/linux/bpf.h
+ * but may not be identical
+ * struct btf_sec_func_info for section #2
+ * a list of bpf_func_info records for section #2
+ * ......
+ *
+ * Note that the bpf_func_info record size in .BTF.ext may not
+ * be the same as the one defined in include/uapi/linux/bpf.h.
+ * The loader should ensure that record_size meets minimum
+ * requirement and pass the record as is to the kernel. The
+ * kernel will handle the func_info properly based on its contents.
+ */
+struct btf_ext_header {
+ __u16 magic;
+ __u8 version;
+ __u8 flags;
+ __u32 hdr_len;
+
+ /* All offsets are in bytes relative to the end of this header */
+ __u32 func_info_off;
+ __u32 func_info_len;
+ __u32 line_info_off;
+ __u32 line_info_len;
+
+ /* optional part of .BTF.ext header */
+ __u32 core_relo_off;
+ __u32 core_relo_len;
+};
+
struct btf_ext {
union {
struct btf_ext_header *hdr;
@@ -145,7 +183,7 @@ struct btf_ext {
};
struct btf_ext_info func_info;
struct btf_ext_info line_info;
- struct btf_ext_info field_reloc_info;
+ struct btf_ext_info core_relo_info;
__u32 data_size;
};
@@ -170,32 +208,34 @@ struct bpf_line_info_min {
__u32 line_col;
};
-/* bpf_field_info_kind encodes which aspect of captured field has to be
- * adjusted by relocations. Currently supported values are:
- * - BPF_FIELD_BYTE_OFFSET: field offset (in bytes);
- * - BPF_FIELD_EXISTS: field existence (1, if field exists; 0, otherwise);
+/* bpf_core_relo_kind encodes which aspect of captured field/type/enum value
+ * has to be adjusted by relocations.
*/
-enum bpf_field_info_kind {
+enum bpf_core_relo_kind {
BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */
- BPF_FIELD_BYTE_SIZE = 1,
+ BPF_FIELD_BYTE_SIZE = 1, /* field size in bytes */
BPF_FIELD_EXISTS = 2, /* field existence in target kernel */
- BPF_FIELD_SIGNED = 3,
- BPF_FIELD_LSHIFT_U64 = 4,
- BPF_FIELD_RSHIFT_U64 = 5,
+ BPF_FIELD_SIGNED = 3, /* field signedness (0 - unsigned, 1 - signed) */
+ BPF_FIELD_LSHIFT_U64 = 4, /* bitfield-specific left bitshift */
+ BPF_FIELD_RSHIFT_U64 = 5, /* bitfield-specific right bitshift */
};
-/* The minimum bpf_field_reloc checked by the loader
+/* The minimum bpf_core_relo checked by the loader
*
- * Field relocation captures the following data:
+ * CO-RE relocation captures the following data:
* - insn_off - instruction offset (in bytes) within a BPF program that needs
* its insn->imm field to be relocated with actual field info;
* - type_id - BTF type ID of the "root" (containing) entity of a relocatable
- * field;
+ * type or field;
* - access_str_off - offset into corresponding .BTF string section. String
- * itself encodes an accessed field using a sequence of field and array
- * indicies, separated by colon (:). It's conceptually very close to LLVM's
- * getelementptr ([0]) instruction's arguments for identifying offset to
- * a field.
+ * interpretation depends on specific relocation kind:
+ * - for field-based relocations, string encodes an accessed field using
+ * a sequence of field and array indices, separated by colon (:). It's
+ * conceptually very close to LLVM's getelementptr ([0]) instruction's
+ * arguments for identifying offset to a field.
+ * - for type-based relocations, strings is expected to be just "0";
+ * - for enum value-based relocations, string contains an index of enum
+ * value within its enum type;
*
* Example to provide a better feel.
*
@@ -226,11 +266,11 @@ enum bpf_field_info_kind {
*
* [0] https://llvm.org/docs/LangRef.html#getelementptr-instruction
*/
-struct bpf_field_reloc {
+struct bpf_core_relo {
__u32 insn_off;
__u32 type_id;
__u32 access_str_off;
- enum bpf_field_info_kind kind;
+ enum bpf_core_relo_kind kind;
};
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */