bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: John Fastabend <john.fastabend@gmail.com>
To: andriin@fb.com, ast@kernel.org, daniel@iogearbox.net
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, john.fastabend@gmail.com
Subject: [bpf-next PATCH] bpf: libbpf, add kernel version section parsing back
Date: Fri, 18 Oct 2019 07:41:26 -0700	[thread overview]
Message-ID: <157140968634.9073.6407090804163937103.stgit@john-XPS-13-9370> (raw)

With commit "libbpf: stop enforcing kern_version,..." we removed the
kernel version section parsing in favor of querying for the kernel
using uname() and populating the version using the result of the
query. After this any version sections were simply ignored.

Unfortunately, the world of kernels is not so friendly. I've found some
customized kernels where uname() does not match the in kernel version.
To fix this so programs can load in this environment this patch adds
back parsing the section and if it exists uses the user specified
kernel version to override the uname() result. However, keep most the
kernel uname() discovery bits so users are not required to insert the
version except in these odd cases.

Fixes: 5e61f27070292 ("libbpf: stop enforcing kern_version, populate it for users")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
 tools/lib/bpf/libbpf.c |   21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index fcea6988f962..675383131179 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -656,6 +656,21 @@ bpf_object__init_license(struct bpf_object *obj, void *data, size_t size)
 	return 0;
+static int
+bpf_object__init_kversion(struct bpf_object *obj, void *data, size_t size)
+	__u32 kver;
+	if (size != sizeof(kver)) {
+		pr_warning("invalid kver section in %s\n", obj->path);
+	}
+	memcpy(&kver, data, sizeof(kver));
+	obj->kern_version = kver;
+	pr_debug("kernel version of %s is %x\n", obj->path, obj->kern_version);
+	return 0;
 static int compare_bpf_map(const void *_a, const void *_b)
 	const struct bpf_map *a = _a;
@@ -1573,7 +1588,11 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 			if (err)
 				return err;
 		} else if (strcmp(name, "version") == 0) {
-			/* skip, we don't need it anymore */
+			err = bpf_object__init_kversion(obj,
+							data->d_buf,
+							data->d_size);
+			if (err)
+				return err;
 		} else if (strcmp(name, "maps") == 0) {
 			obj->efile.maps_shndx = idx;
 		} else if (strcmp(name, MAPS_ELF_SEC) == 0) {

             reply	other threads:[~2019-10-18 14:41 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18 14:41 John Fastabend [this message]
2019-10-18 16:51 ` Andrii Nakryiko
2019-10-19  1:33   ` Alexei Starovoitov
2019-10-19  4:41     ` John Fastabend
2019-10-18 19:11 ` Daniel Borkmann

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=157140968634.9073.6407090804163937103.stgit@john-XPS-13-9370 \
    --to=john.fastabend@gmail.com \
    --cc=andriin@fb.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=netdev@vger.kernel.org \
    --subject='Re: [bpf-next PATCH] bpf: libbpf, add kernel version section parsing back' \


* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).