Teach BTF to recognized wrong endianness and transparently convert it
internally to host endianness. Original endianness of BTF will be preserved
and used during btf__get_raw_data() to convert resulting raw data to the same
endianness and a source raw_data. This means that little-endian host can parse
big-endian BTF with no issues, all the type data will be presented to the
client application in native endianness, but when it's time for emitting BTF
to persist it in a file (e.g., after BTF deduplication), original non-native
endianness will be preserved and stored.
It's possible to query original endianness of BTF data with new
btf__endianness() API. It's also possible to override desired output
endianness with btf__set_endianness(), so that if application needs to load,
say, big-endian BTF and store it as little-endian BTF, it's possible to
manually override this. If btf__set_endianness() was used to change
endianness, btf__endianness() will reflect overridden endianness.
Given there are no known use cases for supporting cross-endianness for
.BTF.ext, loading .BTF.ext in non-native endianness is not supported.
Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
---
tools/lib/bpf/btf.c | 310 +++++++++++++++++++++++++++++++--------
tools/lib/bpf/btf.h | 7 +
tools/lib/bpf/libbpf.map | 2 +
3 files changed, 255 insertions(+), 64 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index c25f49fad5a6..e1dbd766c698 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/* Copyright (c) 2018 Facebook */
+#include <byteswap.h>
#include <endian.h>
#include <stdio.h>
#include <stdlib.h>
@@ -27,8 +28,13 @@
static struct btf_type btf_void;
struct btf {
+ /* raw BTF data in native endianness */
void *raw_data;
+ /* raw BTF data in non-native endianness */
+ void *raw_data_swapped;
__u32 raw_size;
+ /* whether target endianness differs from the native one */
+ bool swapped_endian;
/*
* When BTF is loaded from an ELF or raw memory it is stored
@@ -153,9 +159,19 @@ static int btf_add_type_idx_entry(struct btf *btf, __u32 type_off)
return 0;
}
+static void btf_bswap_hdr(struct btf_header *h)
+{
+ h->magic = bswap_16(h->magic);
+ h->hdr_len = bswap_32(h->hdr_len);
+ h->type_off = bswap_32(h->type_off);
+ h->type_len = bswap_32(h->type_len);
+ h->str_off = bswap_32(h->str_off);
+ h->str_len = bswap_32(h->str_len);
+}
+
static int btf_parse_hdr(struct btf *btf)
{
- const struct btf_header *hdr = btf->hdr;
+ struct btf_header *hdr = btf->hdr;
__u32 meta_left;
if (btf->raw_size < sizeof(struct btf_header)) {
@@ -163,21 +179,19 @@ static int btf_parse_hdr(struct btf *btf)
return -EINVAL;
}
- if (hdr->magic != BTF_MAGIC) {
+ if (hdr->magic == bswap_16(BTF_MAGIC)) {
+ btf->swapped_endian = true;
+ if (bswap_32(hdr->hdr_len) != sizeof(struct btf_header)) {
+ pr_warn("Can't load BTF with non-native endianness due to unsupported header length %u\n",
+ bswap_32(hdr->hdr_len));
+ return -ENOTSUP;
+ }
+ btf_bswap_hdr(hdr);
+ } else if (hdr->magic != BTF_MAGIC) {
pr_debug("Invalid BTF magic:%x\n", hdr->magic);
return -EINVAL;
}
- if (hdr->version != BTF_VERSION) {
- pr_debug("Unsupported BTF version:%u\n", hdr->version);
- return -ENOTSUP;
- }
-
- if (hdr->flags) {
- pr_debug("Unsupported BTF flags:%x\n", hdr->flags);
- return -ENOTSUP;
- }
-
meta_left = btf->raw_size - sizeof(*hdr);
if (!meta_left) {
pr_debug("BTF has no data\n");
@@ -224,7 +238,7 @@ static int btf_parse_str_sec(struct btf *btf)
static int btf_type_size(const struct btf_type *t)
{
- int base_size = sizeof(struct btf_type);
+ const int base_size = sizeof(struct btf_type);
__u16 vlen = btf_vlen(t);
switch (btf_kind(t)) {
@@ -257,12 +271,83 @@ static int btf_type_size(const struct btf_type *t)
}
}
+static void btf_bswap_type_base(struct btf_type *t)
+{
+ t->name_off = bswap_32(t->name_off);
+ t->info = bswap_32(t->info);
+ t->type = bswap_32(t->type);
+}
+
+static int btf_bswap_type_rest(struct btf_type *t)
+{
+ struct btf_var_secinfo *v;
+ struct btf_member *m;
+ struct btf_array *a;
+ struct btf_param *p;
+ struct btf_enum *e;
+ __u16 vlen = btf_vlen(t);
+ int i;
+
+ switch (btf_kind(t)) {
+ case BTF_KIND_FWD:
+ case BTF_KIND_CONST:
+ case BTF_KIND_VOLATILE:
+ case BTF_KIND_RESTRICT:
+ case BTF_KIND_PTR:
+ case BTF_KIND_TYPEDEF:
+ case BTF_KIND_FUNC:
+ return 0;
+ case BTF_KIND_INT:
+ *(__u32 *)(t + 1) = bswap_32(*(__u32 *)(t + 1));
+ return 0;
+ case BTF_KIND_ENUM:
+ for (i = 0, e = btf_enum(t); i < vlen; i++, e++) {
+ e->name_off = bswap_32(e->name_off);
+ e->val = bswap_32(e->val);
+ }
+ return 0;
+ case BTF_KIND_ARRAY:
+ a = btf_array(t);
+ a->type = bswap_32(a->type);
+ a->index_type = bswap_32(a->index_type);
+ a->nelems = bswap_32(a->nelems);
+ return 0;
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ for (i = 0, m = btf_members(t); i < vlen; i++, m++) {
+ m->name_off = bswap_32(m->name_off);
+ m->type = bswap_32(m->type);
+ m->offset = bswap_32(m->offset);
+ }
+ return 0;
+ case BTF_KIND_FUNC_PROTO:
+ for (i = 0, p = btf_params(t); i < vlen; i++, p++) {
+ p->name_off = bswap_32(p->name_off);
+ p->type = bswap_32(p->type);
+ }
+ return 0;
+ case BTF_KIND_VAR:
+ btf_var(t)->linkage = bswap_32(btf_var(t)->linkage);
+ return 0;
+ case BTF_KIND_DATASEC:
+ for (i = 0, v = btf_var_secinfos(t); i < vlen; i++, v++) {
+ v->type = bswap_32(v->type);
+ v->offset = bswap_32(v->offset);
+ v->size = bswap_32(v->size);
+ }
+ return 0;
+ default:
+ pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));
+ return -EINVAL;
+ }
+}
+
static int btf_parse_type_sec(struct btf *btf)
{
struct btf_header *hdr = btf->hdr;
void *next_type = btf->types_data;
void *end_type = next_type + hdr->type_len;
- int err, type_size;
+ int err, i, type_size;
/* VOID (type_id == 0) is specially handled by btf__get_type_by_id(),
* so ensure we can never properly use its offset from index by
@@ -272,19 +357,36 @@ static int btf_parse_type_sec(struct btf *btf)
if (err)
return err;
- while (next_type < end_type) {
- err = btf_add_type_idx_entry(btf, next_type - btf->types_data);
- if (err)
- return err;
+ while (next_type + sizeof(struct btf_type) <= end_type) {
+ i++;
+
+ if (btf->swapped_endian)
+ btf_bswap_type_base(next_type);
type_size = btf_type_size(next_type);
if (type_size < 0)
return type_size;
+ if (next_type + type_size > end_type) {
+ pr_warn("BTF type [%d] is malformed\n", i);
+ return -EINVAL;
+ }
+
+ if (btf->swapped_endian && btf_bswap_type_rest(next_type))
+ return -EINVAL;
+
+ err = btf_add_type_idx_entry(btf, next_type - btf->types_data);
+ if (err)
+ return err;
next_type += type_size;
btf->nr_types++;
}
+ if (next_type != end_type) {
+ pr_warn("BTF types data is malformed\n");
+ return -EINVAL;
+ }
+
return 0;
}
@@ -373,6 +475,38 @@ int btf__set_pointer_size(struct btf *btf, size_t ptr_sz)
return 0;
}
+static bool is_host_big_endian(void)
+{
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+ return false;
+#elif __BYTE_ORDER == __BIG_ENDIAN
+ return true;
+#else
+# error "Unrecognized __BYTE_ORDER__"
+#endif
+}
+
+enum btf_endianness btf__endianness(const struct btf *btf)
+{
+ if (is_host_big_endian())
+ return btf->swapped_endian ? BTF_LITTLE_ENDIAN : BTF_BIG_ENDIAN;
+ else
+ return btf->swapped_endian ? BTF_BIG_ENDIAN : BTF_LITTLE_ENDIAN;
+}
+
+int btf__set_endianness(struct btf *btf, enum btf_endianness endian)
+{
+ if (endian != BTF_LITTLE_ENDIAN && endian != BTF_BIG_ENDIAN)
+ return -EINVAL;
+
+ btf->swapped_endian = is_host_big_endian() != (endian == BTF_BIG_ENDIAN);
+ if (!btf->swapped_endian) {
+ free(btf->raw_data_swapped);
+ btf->raw_data_swapped = NULL;
+ }
+ return 0;
+}
+
static bool btf_type_is_void(const struct btf_type *t)
{
return t == &btf_void || btf_is_fwd(t);
@@ -561,6 +695,7 @@ void btf__free(struct btf *btf)
free(btf->strs_data);
}
free(btf->raw_data);
+ free(btf->raw_data_swapped);
free(btf->type_offs);
free(btf);
}
@@ -572,8 +707,10 @@ struct btf *btf__new_empty(void)
btf = calloc(1, sizeof(*btf));
if (!btf)
return ERR_PTR(-ENOMEM);
+
btf->fd = -1;
btf->ptr_sz = sizeof(void *);
+ btf->swapped_endian = false;
/* +1 for empty string at offset 0 */
btf->raw_size = sizeof(struct btf_header) + 1;
@@ -604,8 +741,6 @@ struct btf *btf__new(const void *data, __u32 size)
if (!btf)
return ERR_PTR(-ENOMEM);
- btf->fd = -1;
-
btf->raw_data = malloc(size);
if (!btf->raw_data) {
err = -ENOMEM;
@@ -624,6 +759,10 @@ struct btf *btf__new(const void *data, __u32 size)
err = btf_parse_str_sec(btf);
err = err ?: btf_parse_type_sec(btf);
+ if (err)
+ goto done;
+
+ btf->fd = -1;
done:
if (err) {
@@ -634,17 +773,6 @@ struct btf *btf__new(const void *data, __u32 size)
return btf;
}
-static bool btf_check_endianness(const GElf_Ehdr *ehdr)
-{
-#if __BYTE_ORDER == __LITTLE_ENDIAN
- return ehdr->e_ident[EI_DATA] == ELFDATA2LSB;
-#elif __BYTE_ORDER == __BIG_ENDIAN
- return ehdr->e_ident[EI_DATA] == ELFDATA2MSB;
-#else
-# error "Unrecognized __BYTE_ORDER__"
-#endif
-}
-
struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
{
Elf_Data *btf_data = NULL, *btf_ext_data = NULL;
@@ -677,10 +805,6 @@ struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
pr_warn("failed to get EHDR from %s\n", path);
goto done;
}
- if (!btf_check_endianness(&ehdr)) {
- pr_warn("non-native ELF endianness is not supported\n");
- goto done;
- }
if (!elf_rawdata(elf_getscn(elf, ehdr.e_shstrndx), NULL)) {
pr_warn("failed to get e_shstrndx from %s\n", path);
goto done;
@@ -792,7 +916,7 @@ struct btf *btf__parse_raw(const char *path)
err = -EIO;
goto err_out;
}
- if (magic != BTF_MAGIC) {
+ if (magic != BTF_MAGIC && magic != bswap_16(BTF_MAGIC)) {
/* definitely not a raw BTF */
err = -EPROTO;
goto err_out;
@@ -942,11 +1066,13 @@ int btf__finalize_data(struct bpf_object *obj, struct btf *btf)
return err;
}
+static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endian);
+
int btf__load(struct btf *btf)
{
__u32 log_buf_size = 0, raw_size;
char *log_buf = NULL;
- const void *raw_data;
+ void *raw_data;
int err = 0;
if (btf->fd >= 0)
@@ -961,11 +1087,14 @@ int btf__load(struct btf *btf)
*log_buf = 0;
}
- raw_data = btf__get_raw_data(btf, &raw_size);
+ raw_data = btf_get_raw_data(btf, &raw_size, false);
if (!raw_data) {
err = -ENOMEM;
goto done;
}
+ /* cache native raw data representation */
+ btf->raw_size = raw_size;
+ btf->raw_data = raw_data;
btf->fd = bpf_load_btf(raw_data, raw_size, log_buf, log_buf_size, false);
if (btf->fd < 0) {
@@ -998,31 +1127,73 @@ void btf__set_fd(struct btf *btf, int fd)
btf->fd = fd;
}
-const void *btf__get_raw_data(const struct btf *btf_ro, __u32 *size)
+static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endian)
{
- struct btf *btf = (struct btf *)btf_ro;
+ struct btf_header *hdr = btf->hdr;
+ struct btf_type *t;
+ void *data, *p;
+ __u32 data_sz;
+ int i;
- if (!btf->raw_data) {
- struct btf_header *hdr = btf->hdr;
- void *data;
+ data = swap_endian ? btf->raw_data_swapped : btf->raw_data;
+ if (data) {
+ *size = btf->raw_size;
+ return data;
+ }
+
+ data_sz = hdr->hdr_len + hdr->type_len + hdr->str_len;
+ data = calloc(1, data_sz);
+ if (!data)
+ return NULL;
+ p = data;
+
+ memcpy(p, hdr, hdr->hdr_len);
+ if (swap_endian)
+ btf_bswap_hdr(p);
+ p += hdr->hdr_len;
+
+ memcpy(p, btf->types_data, hdr->type_len);
+ if (swap_endian) {
+ for (i = 1; i <= btf->nr_types; i++) {
+ t = p + btf->type_offs[i];
+ /* btf_bswap_type_rest() relies on native t->info, so
+ * we swap base type info after we swapped all the
+ * additional information
+ */
+ if (btf_bswap_type_rest(t))
+ goto err_out;
+ btf_bswap_type_base(t);
+ }
+ }
+ p += hdr->type_len;
+
+ memcpy(p, btf->strs_data, hdr->str_len);
+ p += hdr->str_len;
- btf->raw_size = hdr->hdr_len + hdr->type_len + hdr->str_len;
- btf->raw_data = calloc(1, btf->raw_size);
- if (!btf->raw_data)
- return NULL;
- data = btf->raw_data;
+ *size = data_sz;
+ return data;
+err_out:
+ free(data);
+ return NULL;
+}
- memcpy(data, hdr, hdr->hdr_len);
- data += hdr->hdr_len;
+const void *btf__get_raw_data(const struct btf *btf_ro, __u32 *size)
+{
+ struct btf *btf = (struct btf *)btf_ro;
+ __u32 data_sz;
+ void *data;
- memcpy(data, btf->types_data, hdr->type_len);
- data += hdr->type_len;
+ data = btf_get_raw_data(btf, &data_sz, btf->swapped_endian);
+ if (!data)
+ return NULL;
- memcpy(data, btf->strs_data, hdr->str_len);
- data += hdr->str_len;
- }
- *size = btf->raw_size;
- return btf->raw_data;
+ btf->raw_size = data_sz;
+ if (btf->swapped_endian)
+ btf->raw_data_swapped = data;
+ else
+ btf->raw_data = data;
+ *size = data_sz;
+ return data;
}
const char *btf__str_by_offset(const struct btf *btf, __u32 offset)
@@ -1190,6 +1361,18 @@ static bool strs_hash_equal_fn(const void *key1, const void *key2, void *ctx)
return strcmp(str1, str2) == 0;
}
+static void btf_invalidate_raw_data(struct btf *btf)
+{
+ if (btf->raw_data) {
+ free(btf->raw_data);
+ btf->raw_data = NULL;
+ }
+ if (btf->raw_data_swapped) {
+ free(btf->raw_data_swapped);
+ btf->raw_data_swapped = NULL;
+ }
+}
+
/* Ensure BTF is ready to be modified (by splitting into a three memory
* regions for header, types, and strings). Also invalidate cached
* raw_data, if any.
@@ -1203,10 +1386,7 @@ static int btf_ensure_modifiable(struct btf *btf)
if (btf_is_modifiable(btf)) {
/* any BTF modification invalidates raw_data */
- if (btf->raw_data) {
- free(btf->raw_data);
- btf->raw_data = NULL;
- }
+ btf_invalidate_raw_data(btf);
return 0;
}
@@ -1254,8 +1434,7 @@ static int btf_ensure_modifiable(struct btf *btf)
btf->strs_deduped = btf->hdr->str_len <= 1;
/* invalidate raw_data representation */
- free(btf->raw_data);
- btf->raw_data = NULL;
+ btf_invalidate_raw_data(btf);
return 0;
@@ -2275,7 +2454,10 @@ static int btf_ext_parse_hdr(__u8 *data, __u32 data_size)
return -EINVAL;
}
- if (hdr->magic != BTF_MAGIC) {
+ if (hdr->magic == bswap_16(BTF_MAGIC)) {
+ pr_warn("BTF.ext in non-native endianness is not supported\n");
+ return -ENOTSUP;
+ } else if (hdr->magic != BTF_MAGIC) {
pr_debug("Invalid BTF.ext magic:%x\n", hdr->magic);
return -EINVAL;
}
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index f7dec0144c3c..57247240a20a 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -25,6 +25,11 @@ struct btf_type;
struct bpf_object;
+enum btf_endianness {
+ BTF_LITTLE_ENDIAN = 0,
+ BTF_BIG_ENDIAN = 1,
+};
+
LIBBPF_API void btf__free(struct btf *btf);
LIBBPF_API struct btf *btf__new(const void *data, __u32 size);
LIBBPF_API struct btf *btf__new_empty(void);
@@ -42,6 +47,8 @@ LIBBPF_API const struct btf_type *btf__type_by_id(const struct btf *btf,
__u32 id);
LIBBPF_API size_t btf__pointer_size(const struct btf *btf);
LIBBPF_API int btf__set_pointer_size(struct btf *btf, size_t ptr_sz);
+LIBBPF_API enum btf_endianness btf__endianness(const struct btf *btf);
+LIBBPF_API int btf__set_endianness(struct btf *btf, enum btf_endianness endian);
LIBBPF_API __s64 btf__resolve_size(const struct btf *btf, __u32 type_id);
LIBBPF_API int btf__resolve_type(const struct btf *btf, __u32 type_id);
LIBBPF_API int btf__align_of(const struct btf *btf, __u32 id);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 6b10ebad69c6..f7a8ff37ef04 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -325,8 +325,10 @@ LIBBPF_0.2.0 {
btf__add_union;
btf__add_var;
btf__add_volatile;
+ btf__endianness;
btf__find_str;
btf__new_empty;
+ btf__set_endianness;
btf__str_by_offset;
perf_buffer__buffer_cnt;
perf_buffer__buffer_fd;
--
2.24.1
