netdev - Re: [PATCH bpf-next v2 2/3] libbpf: add bpf_object__load_xattr() API function to pass log

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Date:   Thu, 23 May 2019 16:29:47 +0000
From:   Yonghong Song <yhs@...com>
To:     Quentin Monnet <quentin.monnet@...ronome.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
CC:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "oss-drivers@...ronome.com" <oss-drivers@...ronome.com>
Subject: Re: [PATCH bpf-next v2 2/3] libbpf: add bpf_object__load_xattr() API
 function to pass log_level



On 5/23/19 9:19 AM, Yonghong Song wrote:
> 
> 
> On 5/23/19 3:54 AM, Quentin Monnet wrote:
>> libbpf was recently made aware of the log_level attribute for programs,
>> used to specify the level of information expected to be dumped by the
>> verifier.
>>
>> Create an API function to pass additional attributes when loading a
>> bpf_object, so we can set this log_level value in programs when loading
>> them, and so that so that applications relying on libbpf but not calling
> "so that so that" => "so that"
>> bpf_prog_load_xattr() can also use that feature.
> 
> Do not fully understand the above statement. From the code below,
> I did not see how the non-zero log_level can be set for bpf_program
> without bpf_prog_load_xattr(). Maybe I miss something?

Looks like next patch uses it when -d is specified.
Probably commit message can be made more clear.

> 
>>
>> v2:
>> - We are in a new cycle, bump libbpf extraversion number.
>>
>> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
>> Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
>> ---
>>   tools/lib/bpf/Makefile   |  2 +-
>>   tools/lib/bpf/libbpf.c   | 20 +++++++++++++++++---
>>   tools/lib/bpf/libbpf.h   |  6 ++++++
>>   tools/lib/bpf/libbpf.map |  5 +++++
>>   4 files changed, 29 insertions(+), 4 deletions(-)
>>
>> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
>> index a2aceadf68db..9312066a1ae3 100644
>> --- a/tools/lib/bpf/Makefile
>> +++ b/tools/lib/bpf/Makefile
>> @@ -3,7 +3,7 @@
>>   BPF_VERSION = 0
>>   BPF_PATCHLEVEL = 0
>> -BPF_EXTRAVERSION = 3
>> +BPF_EXTRAVERSION = 4
>>   MAKEFLAGS += --no-print-directory
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 197b574406b3..1c6fb7a3201e 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -2222,7 +2222,7 @@ static bool 
>> bpf_program__is_function_storage(struct bpf_program *prog,
>>   }
>>   static int
>> -bpf_object__load_progs(struct bpf_object *obj)
>> +bpf_object__load_progs(struct bpf_object *obj, int log_level)
>>   {
>>       size_t i;
>>       int err;
>> @@ -2230,6 +2230,7 @@ bpf_object__load_progs(struct bpf_object *obj)
>>       for (i = 0; i < obj->nr_programs; i++) {
>>           if (bpf_program__is_function_storage(&obj->programs[i], obj))
>>               continue;
>> +        obj->programs[i].log_level = log_level;
>>           err = bpf_program__load(&obj->programs[i],
>>                       obj->license,
>>                       obj->kern_version);
>> @@ -2381,10 +2382,14 @@ int bpf_object__unload(struct bpf_object *obj)
>>       return 0;
>>   }
>> -int bpf_object__load(struct bpf_object *obj)
>> +int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
>>   {
>> +    struct bpf_object *obj;
>>       int err;
>> +    if (!attr)
>> +        return -EINVAL;
>> +    obj = attr->obj;
>>       if (!obj)
>>           return -EINVAL;
>> @@ -2397,7 +2402,7 @@ int bpf_object__load(struct bpf_object *obj)
>>       CHECK_ERR(bpf_object__create_maps(obj), err, out);
>>       CHECK_ERR(bpf_object__relocate(obj), err, out);
>> -    CHECK_ERR(bpf_object__load_progs(obj), err, out);
>> +    CHECK_ERR(bpf_object__load_progs(obj, attr->log_level), err, out);
>>       return 0;
>>   out:
>> @@ -2406,6 +2411,15 @@ int bpf_object__load(struct bpf_object *obj)
>>       return err;
>>   }
>> +int bpf_object__load(struct bpf_object *obj)
>> +{
>> +    struct bpf_object_load_attr attr = {
>> +        .obj = obj,
>> +    };
>> +
>> +    return bpf_object__load_xattr(&attr);
>> +}
>> +
>>   static int check_path(const char *path)
>>   {
>>       char *cp, errmsg[STRERR_BUFSIZE];
>> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
>> index c5ff00515ce7..e1c748db44f6 100644
>> --- a/tools/lib/bpf/libbpf.h
>> +++ b/tools/lib/bpf/libbpf.h
>> @@ -89,8 +89,14 @@ LIBBPF_API int bpf_object__unpin_programs(struct 
>> bpf_object *obj,
>>   LIBBPF_API int bpf_object__pin(struct bpf_object *object, const char 
>> *path);
>>   LIBBPF_API void bpf_object__close(struct bpf_object *object);
>> +struct bpf_object_load_attr {
>> +    struct bpf_object *obj;
>> +    int log_level;
>> +};
>> +
>>   /* Load/unload object into/from kernel */
>>   LIBBPF_API int bpf_object__load(struct bpf_object *obj);
>> +LIBBPF_API int bpf_object__load_xattr(struct bpf_object_load_attr 
>> *attr);
>>   LIBBPF_API int bpf_object__unload(struct bpf_object *obj);
>>   LIBBPF_API const char *bpf_object__name(struct bpf_object *obj);
>>   LIBBPF_API unsigned int bpf_object__kversion(struct bpf_object *obj);
>> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
>> index 673001787cba..6ce61fa0baf3 100644
>> --- a/tools/lib/bpf/libbpf.map
>> +++ b/tools/lib/bpf/libbpf.map
>> @@ -164,3 +164,8 @@ LIBBPF_0.0.3 {
>>           bpf_map_freeze;
>>           btf__finalize_data;
>>   } LIBBPF_0.0.2;
>> +
>> +LIBBPF_0.0.4 {
>> +    global:
>> +        bpf_object__load_xattr;
>> +} LIBBPF_0.0.3;
>>