support reading in metadata, fixing endian issues on reading;
also support writing metadata section to raw BTF object.
There is not yet an API to populate the metadata with meaningful
information.
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
tools/lib/bpf/btf.c | 141 ++++++++++++++++++++++++++++++++++----------
1 file changed, 111 insertions(+), 30 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 8484b563b53d..036dc1505969 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -16,6 +16,7 @@
#include <linux/err.h>
#include <linux/btf.h>
#include <gelf.h>
+#include <zlib.h>
#include "btf.h"
#include "bpf.h"
#include "libbpf.h"
@@ -39,36 +40,40 @@ struct btf {
/*
* When BTF is loaded from an ELF or raw memory it is stored
- * in a contiguous memory block. The hdr, type_data, and, strs_data
- * point inside that memory region to their respective parts of BTF
- * representation:
+ * in a contiguous memory block. The hdr, type_data, strs_data,
+ * and optional meta_data point inside that memory region to their
+ * respective parts of BTF representation:
*
- * +--------------------------------+
- * | Header | Types | Strings |
- * +--------------------------------+
- * ^ ^ ^
- * | | |
- * hdr | |
- * types_data-+ |
- * strs_data------------+
+ * +--------------------------------+----------+
+ * | Header | Types | Strings | Metadata |
+ * +--------------------------------+----------+
+ * ^ ^ ^ ^
+ * | | | |
+ * hdr | | |
+ * types_data-+ | |
+ * strs_data------------+ |
+ * meta_data------------------------+
+ *
+ * meta_data is optional.
*
* If BTF data is later modified, e.g., due to types added or
* removed, BTF deduplication performed, etc, this contiguous
- * representation is broken up into three independently allocated
- * memory regions to be able to modify them independently.
+ * representation is broken up into three or four independently
+ * allocated memory regions to be able to modify them independently.
* raw_data is nulled out at that point, but can be later allocated
* and cached again if user calls btf__raw_data(), at which point
- * raw_data will contain a contiguous copy of header, types, and
- * strings:
+ * raw_data will contain a contiguous copy of header, types, strings
+ * and (again optionally) metadata:
*
- * +----------+ +---------+ +-----------+
- * | Header | | Types | | Strings |
- * +----------+ +---------+ +-----------+
- * ^ ^ ^
- * | | |
- * hdr | |
- * types_data----+ |
- * strset__data(strs_set)-----+
+ * +----------+ +---------+ +-----------+ +----------+
+ * | Header | | Types | | Strings | | Metadata |
+ * +----------+ +---------+ +-----------+ +---------_+
+ * ^ ^ ^ ^
+ * | | | |
+ * hdr | | |
+ * types_data----+ | |
+ * strset__data(strs_set)-----+ |
+ * meta_data---------------------------------+
*
* +----------+---------+-----------+
* | Header | Types | Strings |
@@ -116,6 +121,8 @@ struct btf {
/* whether strings are already deduplicated */
bool strs_deduped;
+ void *meta_data;
+
/* BTF object FD, if loaded into kernel */
int fd;
@@ -215,6 +222,11 @@ static void btf_bswap_hdr(struct btf_header *h)
h->type_len = bswap_32(h->type_len);
h->str_off = bswap_32(h->str_off);
h->str_len = bswap_32(h->str_len);
+ if (h->hdr_len >= sizeof(struct btf_header)) {
+ h->meta_header.meta_off = bswap_32(h->meta_header.meta_off);
+ h->meta_header.meta_len = bswap_32(h->meta_header.meta_len);
+ }
+
}
static int btf_parse_hdr(struct btf *btf)
@@ -222,14 +234,17 @@ static int btf_parse_hdr(struct btf *btf)
struct btf_header *hdr = btf->hdr;
__u32 meta_left;
- if (btf->raw_size < sizeof(struct btf_header)) {
+ if (btf->raw_size < sizeof(struct btf_header) - sizeof(struct btf_meta_header)) {
pr_debug("BTF header not found\n");
return -EINVAL;
}
if (hdr->magic == bswap_16(BTF_MAGIC)) {
+ int swapped_len = bswap_32(hdr->hdr_len);
+
btf->swapped_endian = true;
- if (bswap_32(hdr->hdr_len) != sizeof(struct btf_header)) {
+ if (swapped_len != sizeof(struct btf_header) &&
+ swapped_len != sizeof(struct btf_header) - sizeof(struct btf_meta_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;
@@ -285,6 +300,42 @@ static int btf_parse_str_sec(struct btf *btf)
return 0;
}
+static void btf_bswap_meta(struct btf_metadata *meta, int len)
+{
+ struct btf_kind_meta *m = &meta->kind_meta[0];
+ struct btf_kind_meta *end = (void *)meta + len;
+
+ meta->flags = bswap_32(meta->flags);
+ meta->crc = bswap_32(meta->crc);
+ meta->base_crc = bswap_32(meta->base_crc);
+ meta->description_off = bswap_32(meta->description_off);
+
+ while (m < end) {
+ m->name_off = bswap_32(m->name_off);
+ m->flags = bswap_16(m->flags);
+ m++;
+ }
+}
+
+static int btf_parse_meta_sec(struct btf *btf)
+{
+ const struct btf_header *hdr = btf->hdr;
+
+ if (hdr->hdr_len < sizeof(struct btf_header) ||
+ !hdr->meta_header.meta_off || !hdr->meta_header.meta_len)
+ return 0;
+ if (hdr->meta_header.meta_len < sizeof(struct btf_metadata)) {
+ pr_debug("Invalid BTF metadata section\n");
+ return -EINVAL;
+ }
+ btf->meta_data = btf->raw_data + btf->hdr->hdr_len + btf->hdr->meta_header.meta_off;
+
+ if (btf->swapped_endian)
+ btf_bswap_meta(btf->meta_data, hdr->meta_header.meta_len);
+
+ return 0;
+}
+
static int btf_type_size(const struct btf_type *t)
{
const int base_size = sizeof(struct btf_type);
@@ -904,6 +955,7 @@ static struct btf *btf_new(const void *data, __u32 size, struct btf *base_btf)
err = err ?: btf_parse_type_sec(btf);
if (err)
goto done;
+ err = btf_parse_meta_sec(btf);
done:
if (err) {
@@ -1267,6 +1319,11 @@ static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endi
}
data_sz = hdr->hdr_len + hdr->type_len + hdr->str_len;
+ if (btf->meta_data) {
+ data_sz = roundup(data_sz, 8);
+ data_sz += hdr->meta_header.meta_len;
+ hdr->meta_header.meta_off = roundup(hdr->type_len + hdr->str_len, 8);
+ }
data = calloc(1, data_sz);
if (!data)
return NULL;
@@ -1293,8 +1350,21 @@ static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endi
p += hdr->type_len;
memcpy(p, btf_strs_data(btf), hdr->str_len);
- p += hdr->str_len;
+ /* round up to 8 byte alignment to match offset above */
+ p = data + hdr->hdr_len + roundup(hdr->type_len + hdr->str_len, 8);
+
+ if (btf->meta_data) {
+ struct btf_metadata *meta = p;
+ memcpy(p, btf->meta_data, hdr->meta_header.meta_len);
+ if (!swap_endian) {
+ meta->crc = crc32(0L, (const Bytef *)&data, sizeof(data));
+ meta->flags |= BTF_META_CRC_SET;
+ }
+ if (swap_endian)
+ btf_bswap_meta(p, hdr->meta_header.meta_len);
+ p += hdr->meta_header.meta_len;
+ }
*size = data_sz;
return data;
err_out:
@@ -1425,13 +1495,13 @@ static void btf_invalidate_raw_data(struct btf *btf)
}
}
-/* 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.
+/* Ensure BTF is ready to be modified (by splitting into a three or four memory
+ * regions for header, types, strings and optional metadata). Also invalidate
+ * cached raw_data, if any.
*/
static int btf_ensure_modifiable(struct btf *btf)
{
- void *hdr, *types;
+ void *hdr, *types, *meta = NULL;
struct strset *set = NULL;
int err = -ENOMEM;
@@ -1446,9 +1516,17 @@ static int btf_ensure_modifiable(struct btf *btf)
types = malloc(btf->hdr->type_len);
if (!hdr || !types)
goto err_out;
+ if (btf->hdr->hdr_len >= sizeof(struct btf_header) &&
+ btf->hdr->meta_header.meta_off && btf->hdr->meta_header.meta_len) {
+ meta = calloc(1, btf->hdr->meta_header.meta_len);
+ if (!meta)
+ goto err_out;
+ }
memcpy(hdr, btf->hdr, btf->hdr->hdr_len);
memcpy(types, btf->types_data, btf->hdr->type_len);
+ if (meta)
+ memcpy(meta, btf->meta_data, btf->hdr->meta_header.meta_len);
/* build lookup index for all strings */
set = strset__new(BTF_MAX_STR_OFFSET, btf->strs_data, btf->hdr->str_len);
@@ -1463,6 +1541,8 @@ static int btf_ensure_modifiable(struct btf *btf)
btf->types_data_cap = btf->hdr->type_len;
btf->strs_data = NULL;
btf->strs_set = set;
+ btf->meta_data = meta;
+
/* if BTF was created from scratch, all strings are guaranteed to be
* unique and deduplicated
*/
@@ -1480,6 +1560,7 @@ static int btf_ensure_modifiable(struct btf *btf)
strset__free(set);
free(hdr);
free(types);
+ free(meta);
return err;
}
--
2.31.1
