From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: "Kumar Kartikeya Dwivedi" <memxor@gmail.com>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"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 v5 07/12] libbpf: Resolve invalid weak kfunc calls with imm = 0, off = 0
Date: Mon, 27 Sep 2021 20:29:36 +0530 [thread overview]
Message-ID: <20210927145941.1383001-8-memxor@gmail.com> (raw)
In-Reply-To: <20210927145941.1383001-1-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.
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
tools/lib/bpf/libbpf.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0f4d203f926e..4b2d0511c1e7 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3416,11 +3416,6 @@ 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,
@@ -5369,8 +5364,13 @@ 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 = 0;
+ insn[0].off = 0;
+ }
break;
case RELO_SUBPROG_ADDR:
if (insn[0].src_reg != BPF_PSEUDO_FUNC) {
@@ -6719,9 +6719,9 @@ static int bpf_object__resolve_ksym_var_btf_id(struct bpf_object *obj,
int id, err;
id = find_ksym_btf_id(obj, ext->name, BTF_KIND_VAR, &btf, &mod_btf);
- if (id == -ESRCH && ext->is_weak) {
- return 0;
- } else if (id < 0) {
+ if (id < 0) {
+ if (id == -ESRCH && ext->is_weak)
+ return 0;
pr_warn("extern (var ksym) '%s': not found in kernel BTF\n",
ext->name);
return id;
@@ -6774,7 +6774,9 @@ 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, &btf, &mod_btf);
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;
+ 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:[~2021-09-27 15:00 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 14:59 [PATCH bpf-next v5 00/12] Support kernel module function calls from eBPF Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 01/12] bpf: Introduce BPF support for kernel module function calls Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 02/12] bpf: Be conservative while processing invalid kfunc calls Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 03/12] bpf: btf: Introduce helpers for dynamic BTF set registration Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 04/12] tools: Allow specifying base BTF file in resolve_btfids Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 05/12] bpf: Enable TCP congestion control kfunc from modules Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 06/12] libbpf: Support kernel module function calls Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` Kumar Kartikeya Dwivedi [this message]
2021-09-27 14:59 ` [PATCH bpf-next v5 08/12] libbpf: Make gen_loader data aligned Kumar Kartikeya Dwivedi
2021-09-29 20:50 ` Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 09/12] libbpf: Update gen_loader to emit BTF_KIND_FUNC relocations Kumar Kartikeya Dwivedi
2021-09-29 0:01 ` Alexei Starovoitov
2021-09-29 0:10 ` Kumar Kartikeya Dwivedi
2021-09-27 14:59 ` [PATCH bpf-next v5 10/12] libbpf: Fix skel_internal.h to set errno on loader retval < 0 Kumar Kartikeya Dwivedi
2021-09-30 3:45 ` Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 11/12] bpf: selftests: Fix fd cleanup in get_branch_snapshot Kumar Kartikeya Dwivedi
2021-09-28 23:58 ` Song Liu
2021-09-29 20:26 ` Alexei Starovoitov
2021-09-27 14:59 ` [PATCH bpf-next v5 12/12] bpf: selftests: Add selftests for module kfunc support Kumar Kartikeya Dwivedi
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