Re: [PATCH bpf-next v3] libbpf: add btf__load_vmlinux_btf/btf__load_module_btf

On 7/31/21 3:26 AM, Andrii Nakryiko wrote:

On Fri, Jul 30, 2021 at 4:40 AM Hengqi Chen [off-list ref] wrote:

quoted

Add two new APIs: btf__load_vmlinux_btf and btf__load_module_btf.
btf__load_vmlinux_btf is just an alias to the existing API named
libbpf_find_kernel_btf, rename to be more precisely and consistent
with existing BTF APIs. btf__load_module_btf can be used to load
module BTF, add it for completeness. These two APIs are useful for
implementing tracing tools and introspection tools. This is part
of the effort towards libbpf 1.0. [1]

[1] https://github.com/libbpf/libbpf/issues/280

I changed this to

[0] Closes: https://github.com/libbpf/libbpf/issues/280

which will close an associated Github issue when we sync sources to
Github next time. Let's see how this works in practice.

quoted

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---

Thanks, applied to bpf-next. But please follow up with a selftest that
would utilize this new module BTF API. It's good to have all APIs
exercised regularly. Look at test_progs.

Thanks, will do.

quoted

 tools/lib/bpf/btf.c      | 15 ++++++++++++++-
 tools/lib/bpf/btf.h      |  6 ++++--
 tools/lib/bpf/libbpf.c   |  4 ++--
 tools/lib/bpf/libbpf.map |  2 ++
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index cafa4f6bd9b1..56e84583e283 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c

@@ -4036,7 +4036,7 @@ static void btf_dedup_merge_hypot_map(struct btf_dedup *d)
                 */
                if (d->hypot_adjust_canon)
                        continue;
-
+
                if (t_kind == BTF_KIND_FWD && c_kind != BTF_KIND_FWD)
                        d->map[t_id] = c_id;

@@ -4410,6 +4410,11 @@ static int btf_dedup_remap_types(struct btf_dedup *d)
  * data out of it to use for target BTF.
  */
 struct btf *libbpf_find_kernel_btf(void)

I switched this to __attribute__((alias("btf__load_vmlinux_btf"))); to
match what Quentin did recently. Also moved comment above to be next
to btf__load_vmlinux_btf.

OK, the alias attribute look nicer.

quoted

+{
+       return btf__load_vmlinux_btf();
+}
+
+struct btf *btf__load_vmlinux_btf(void)
 {
        struct {
                const char *path_fmt;

[...]

quoted

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 5aca3686ca5e..a2f471950213 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map

@@ -380,4 +380,6 @@ LIBBPF_0.5.0 {
                btf__load_into_kernel;
                btf_dump__dump_type_data;
                libbpf_set_strict_mode;
+               btf__load_vmlinux_btf;
+               btf__load_module_btf;

This list needs to be alphabetically sorted. I'll fix it up while
applying, but please remember it for the future.

Yeah, will keep this in mind.

quoted

 } LIBBPF_0.4.0;
--
2.25.1