On Fri, Oct 12, 2018 at 11:54:42AM -0700, Yonghong Song wrote:
> This patch added interface to load a program with the following
> additional information:
> . prog_btf_fd
> . func_info and func_info_len
> where func_info will provides function range and type_id
> corresponding to each function.
>
> If verifier agrees with function range provided by the user,
> the bpf_prog ksym for each function will use the func name
> provided in the type_id, which is supposed to provide better
> encoding as it is not limited by 16 bytes program name
> limitation and this is better for bpf program which contains
> multiple subprograms.
>
> The bpf_prog_info interface is also extended to
> return btf_id and jited_func_types, so user spaces can
> print out the function prototype for each jited function.
>
> Signed-off-by: Yonghong Song <y...@fb.com>
...
> BUILD_BUG_ON(sizeof("bpf_prog_") +
> sizeof(prog->tag) * 2 +
> @@ -401,6 +403,13 @@ static void bpf_get_prog_name(const struct bpf_prog
> *prog, char *sym)
>
> sym += snprintf(sym, KSYM_NAME_LEN, "bpf_prog_");
> sym = bin2hex(sym, prog->tag, sizeof(prog->tag));
> +
> + if (prog->aux->btf) {
> + func_name = btf_get_name_by_id(prog->aux->btf,
> prog->aux->type_id);
> + snprintf(sym, (size_t)(end - sym), "_%s", func_name);
> + return;
Would it make sense to add a comment here that prog->aux->name is ignored
when full btf name is available? (otherwise the same name will appear twice in
ksym)
> + }
> +
> if (prog->aux->name[0])
> snprintf(sym, (size_t)(end - sym), "_%s", prog->aux->name);
...
> +static int check_btf_func(struct bpf_prog *prog, struct bpf_verifier_env
> *env,
> + union bpf_attr *attr)
> +{
> + struct bpf_func_info *data;
> + int i, nfuncs, ret = 0;
> +
> + if (!attr->func_info_len)
> + return 0;
> +
> + nfuncs = attr->func_info_len / sizeof(struct bpf_func_info);
> + if (env->subprog_cnt != nfuncs) {
> + verbose(env, "number of funcs in func_info does not match
> verifier\n");
'does not match verifier' is hard to make sense of.
How about 'number of funcs in func_info doesn't match number of subprogs' ?
> + return -EINVAL;
> + }
> +
> + data = kvmalloc(attr->func_info_len, GFP_KERNEL | __GFP_NOWARN);
> + if (!data) {
> + verbose(env, "no memory to allocate attr func_info\n");
I don't think we ever print such warnings for memory allocations.
imo this can be removed, since enomem is enough.
> + return -ENOMEM;
> + }
> +
> + if (copy_from_user(data, u64_to_user_ptr(attr->func_info),
> + attr->func_info_len)) {
> + verbose(env, "memory copy error for attr func_info\n");
similar thing. kernel never warns about copy_from_user errors.
> + ret = -EFAULT;
> + goto cleanup;
> + }
> +
> + for (i = 0; i < nfuncs; i++) {
> + if (env->subprog_info[i].start != data[i].insn_offset) {
> + verbose(env, "func_info subprog start (%d) does not
> match verifier (%d)\n",
> + env->subprog_info[i].start,
> data[i].insn_offset);
I think printing exact insn offset isn't going to be much help
for regular user to debug it. If this happens, it's likely llvm issue.
How about 'func_info BTF section doesn't match subprog layout in BPF program' ?
