From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: "Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
netdev@vger.kernel.org
Subject: [PATCH bpf-next v2 08/10] libbpf: Resolve invalid weak kfunc calls with imm = 0, off = 0
Date: Tue, 14 Sep 2021 18:07:47 +0530 [thread overview]
Message-ID: <20210914123750.460750-9-memxor@gmail.com> (raw)
In-Reply-To: <20210914123750.460750-1-memxor@gmail.com>
Preserve these calls as it allows verifier to succeed in loading the
program if they are determined to be unreachable after dead code
elimination during program load. If not, the verifier will fail at
runtime. This is done for ext->is_weak symbols similar to the case for
variable ksyms.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
tools/lib/bpf/libbpf.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e78ae57e4379..9c6c1aa73e35 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3409,11 +3409,6 @@ static int bpf_object__collect_externs(struct bpf_object *obj)
return -ENOTSUP;
}
} else if (strcmp(sec_name, KSYMS_SEC) == 0) {
- if (btf_is_func(t) && ext->is_weak) {
- pr_warn("extern weak function %s is unsupported\n",
- ext->name);
- return -ENOTSUP;
- }
ksym_sec = sec;
ext->type = EXT_KSYM;
skip_mods_and_typedefs(obj->btf, t->type,
@@ -5342,8 +5337,12 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
case RELO_EXTERN_FUNC:
ext = &obj->externs[relo->sym_off];
insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL;
- insn[0].imm = ext->ksym.kernel_btf_id;
- insn[0].off = ext->ksym.offset;
+ if (ext->is_set) {
+ insn[0].imm = ext->ksym.kernel_btf_id;
+ insn[0].off = ext->ksym.offset;
+ } else { /* unresolved weak kfunc */
+ insn[0].imm = insn[0].off = 0;
+ }
break;
case RELO_SUBPROG_ADDR:
if (insn[0].src_reg != BPF_PSEUDO_FUNC) {
@@ -6734,8 +6733,10 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj,
kfunc_id = find_ksym_btf_id(obj, ext->name, BTF_KIND_FUNC,
&kern_btf, &kern_btf_fd);
- if (kfunc_id < 0) {
- pr_warn("extern (func ksym) '%s': not found in kernel BTF\n",
+ if (kfunc_id == -ESRCH && ext->is_weak) {
+ return 0;
+ } else if (kfunc_id < 0) {
+ pr_warn("extern (func ksym) '%s': not found in kernel or module BTFs\n",
ext->name);
return kfunc_id;
}
--
2.33.0
next prev parent reply other threads:[~2021-09-14 12:38 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-14 12:37 [PATCH bpf-next v2 00/10] Support kernel module function calls from eBPF Kumar Kartikeya Dwivedi
2021-09-14 12:37 ` [PATCH bpf-next v2 01/10] bpf: Introduce BPF support for kernel module function calls Kumar Kartikeya Dwivedi
2021-09-14 19:31 ` kernel test robot
2021-09-14 22:01 ` kernel test robot
2021-09-14 12:37 ` [PATCH bpf-next v2 02/10] bpf: Be conservative while processing invalid kfunc calls Kumar Kartikeya Dwivedi
2021-09-14 12:37 ` [PATCH bpf-next v2 03/10] bpf: btf: Introduce helpers for dynamic BTF set registration Kumar Kartikeya Dwivedi
2021-09-14 12:37 ` [PATCH bpf-next v2 04/10] tools: Allow specifying base BTF file in resolve_btfids Kumar Kartikeya Dwivedi
2021-09-14 12:37 ` [PATCH bpf-next v2 05/10] bpf: Enable TCP congestion control kfunc from modules Kumar Kartikeya Dwivedi
2021-09-14 12:37 ` [PATCH bpf-next v2 06/10] bpf: Bump MAX_BPF_STACK size to 768 bytes Kumar Kartikeya Dwivedi
2021-09-14 12:37 ` [PATCH bpf-next v2 07/10] libbpf: Support kernel module function calls Kumar Kartikeya Dwivedi
2021-09-14 12:37 ` Kumar Kartikeya Dwivedi [this message]
2021-09-14 12:37 ` [PATCH bpf-next v2 09/10] libbpf: Update gen_loader to emit BTF_KIND_FUNC relocations Kumar Kartikeya Dwivedi
2021-09-14 12:37 ` [PATCH bpf-next v2 10/10] bpf, selftests: Add basic test for module kfunc call Kumar Kartikeya Dwivedi
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:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210914123750.460750-9-memxor@gmail.com \
--to=memxor@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=brouer@redhat.com \
--cc=daniel@iogearbox.net \
--cc=kafai@fb.com \
--cc=netdev@vger.kernel.org \
--cc=songliubraving@fb.com \
--cc=toke@redhat.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).