On 6/16/23 10:17 AM, Alan Maguire wrote:
Support encoding of BTF kind layout data and crcs via
btf__new_empty_opts().
Current supported opts are base_btf, add_kind_layout and
add_crc.
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
tools/lib/bpf/btf.c | 99 ++++++++++++++++++++++++++++++++++++++--
tools/lib/bpf/btf.h | 11 +++++
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 108 insertions(+), 3 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 457997c2a43c..060a93809f64 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"
@@ -882,8 +883,58 @@ void btf__free(struct btf *btf)
free(btf);
}
-static struct btf *btf_new_empty(struct btf *base_btf)
+static void btf_add_kind_layout(struct btf *btf, __u8 kind,
+ __u16 flags, __u8 info_sz, __u8 elem_sz)
{
+ struct btf_kind_layout *k = &btf->kind_layout[kind];
+
+ k->flags = flags;
+ k->info_sz = info_sz;
+ k->elem_sz = elem_sz;
+ btf->hdr->kind_layout_len += sizeof(*k);
+}
+
+static int btf_ensure_modifiable(struct btf *btf);
+
+static int btf_add_kind_layouts(struct btf *btf, struct btf_new_opts *opts)
+{
+ if (btf_ensure_modifiable(btf))
+ return libbpf_err(-ENOMEM);
+
+ btf->kind_layout = calloc(NR_BTF_KINDS, sizeof(struct btf_kind_layout));
+
+ if (!btf->kind_layout)
+ return -ENOMEM;
+
+ /* all supported kinds should describe their layout here. */
+ btf_add_kind_layout(btf, BTF_KIND_UNKN, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_INT, 0, sizeof(__u32), 0);
+ btf_add_kind_layout(btf, BTF_KIND_PTR, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_ARRAY, 0, sizeof(struct btf_array), 0);
+ btf_add_kind_layout(btf, BTF_KIND_STRUCT, 0, 0, sizeof(struct btf_member));
+ btf_add_kind_layout(btf, BTF_KIND_UNION, 0, 0, sizeof(struct btf_member));
+ btf_add_kind_layout(btf, BTF_KIND_ENUM, 0, 0, sizeof(struct btf_enum));
+ btf_add_kind_layout(btf, BTF_KIND_FWD, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_TYPEDEF, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_VOLATILE, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_CONST, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_RESTRICT, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_FUNC, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_FUNC_PROTO, 0, 0, sizeof(struct btf_param));
+ btf_add_kind_layout(btf, BTF_KIND_VAR, 0, sizeof(struct btf_var), 0);
+ btf_add_kind_layout(btf, BTF_KIND_DATASEC, 0, 0, sizeof(struct btf_var_secinfo));
+ btf_add_kind_layout(btf, BTF_KIND_FLOAT, 0, 0, 0);
+ btf_add_kind_layout(btf, BTF_KIND_DECL_TAG, BTF_KIND_LAYOUT_OPTIONAL,
+ sizeof(struct btf_decl_tag), 0);
+ btf_add_kind_layout(btf, BTF_KIND_TYPE_TAG, BTF_KIND_LAYOUT_OPTIONAL, 0, 0);
BTF_KIND_TYPE_TAG cannot be optional. For example,
ptr -> type_tag -> const -> int
if type_tag becomes optional, the whole type chain cannot be parsed
properly.
Also, in Patch 3, we have
+static int btf_type_size(const struct btf *btf, const struct btf_type *t)
{
const int base_size = sizeof(struct btf_type);
__u16 vlen = btf_vlen(t);
@@ -363,8 +391,7 @@ static int btf_type_size(const struct btf_type *t)
case BTF_KIND_DECL_TAG:
return base_size + sizeof(struct btf_decl_tag);
default:
- pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));
- return -EINVAL;
+ return btf_type_size_unknown(btf, t);
}
}
Clearly even if we mark decl_tag as optional, it still handled properly
in the above. So decl_tag does not need BTF_KIND_LAYOUT_OPTIONAL, right?
I guess what we really want to test is in the selftest:
- Add a couple of new kinds for testing purpose, e.g.,
BTF_KIND_OPTIONAL, BTF_KIND_NOT_OPTIONAL,
generate two btf's which uses BTF_KIND_OPTIONAL
and BTF_KIND_NOT_OPTIONAL respectively.
- test these two btf's with this patch set to see whether it
works as expected or not.
Does this make sense?
+ btf_add_kind_layout(btf, BTF_KIND_ENUM64, 0, 0, sizeof(struct btf_enum64));
+
+ return 0;
+}
+
[...]
