On 10/16/18 10:59 AM, Alexei Starovoitov wrote:
> 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)
Will add a comment.
>
>> + }
>> +
>> 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' ?
Sounds good to me.
>
>> + 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.
Okay.
>
>> + 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.
Okay.
>
>> + 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'
> ?
Okay.
>
