| Message ID | 20210920141526.3940002-8-memxor@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | Support kernel module function calls from eBPF | expand |
| Context | Check | Description |
|---|---|---|
| bpf/vmtest-bpf-next | fail | VM_Test |
| bpf/vmtest-bpf-next-PR | fail | PR summary |
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 2 maintainers not CCed: john.fastabend@gmail.com kpsingh@kernel.org |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | warning | CHECK: multiple assignments should be avoided |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
On Mon, Sep 20, 2021 at 7:15 AM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote: > > 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> > --- Looks good with few nits below Acked-by: Andrii Nakryiko <andrii@kernel.org> > 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 3049dfc6088e..3c195eaadf56 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -3413,11 +3413,6 @@ 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, > @@ -5366,8 +5361,12 @@ 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; it's a bit too easy to miss this, please write as two separate statements > + } > break; > case RELO_SUBPROG_ADDR: > if (insn[0].src_reg != BPF_PSEUDO_FUNC) { > @@ -6768,8 +6767,10 @@ 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) { nit: there is return above, no need for "else if", please drop that part. It would be nice if you could clean this up in bpf_object__resolve_ksym_var_btf_id() as well. Thanks! > + pr_warn("extern (func ksym) '%s': not found in kernel or module BTFs\n", > ext->name); > return kfunc_id; > } > -- > 2.33.0 >
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 3049dfc6088e..3c195eaadf56 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -3413,11 +3413,6 @@ 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, @@ -5366,8 +5361,12 @@ 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) { @@ -6768,8 +6767,10 @@ 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; }
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(-)