Re: [bpf-next 2/2] libbpf: Add pathname_concat() helper

[wangyufen]

在 2022/9/10 1:16, sdf@xxxxxxxxxx 写道:
> On 09/09, Wang Yufen wrote:
> > Move snprintf and len check to common helper pathname_concat() to 
> > make the
> > code simpler.
>
> > Signed-off-by: Wang Yufen <wangyufen@xxxxxxxxxx>
> > ---
> >   tools/lib/bpf/libbpf.c | 74 
> > ++++++++++++++++++--------------------------------
> >   1 file changed, 27 insertions(+), 47 deletions(-)
>
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 5854b92..238a03e 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -2096,20 +2096,31 @@ static bool get_map_field_int(const char 
> > *map_name, const struct btf *btf,
> >       return true;
> >   }
>
> > -static int build_map_pin_path(struct bpf_map *map, const char *path)
> > +static int pathname_concat(const char *path, const char *name, char 
> > *buf)
> >   {
> > -    char buf[PATH_MAX];
> >       int len;
>
> > -    if (!path)
> > -        path = "/sys/fs/bpf";
> > -
> > -    len = snprintf(buf, PATH_MAX, "%s/%s", path, bpf_map__name(map));
> > +    len = snprintf(buf, PATH_MAX, "%s/%s", path, name);
> >       if (len < 0)
> >           return -EINVAL;
> >       else if (len >= PATH_MAX)
> >           return -ENAMETOOLONG;
>
> > +    return 0;
> > +}
> > +
> > +static int build_map_pin_path(struct bpf_map *map, const char *path)
> > +{
> > +    char buf[PATH_MAX];
> > +    int err;
> > +
> > +    if (!path)
> > +        path = "/sys/fs/bpf";
> > +
> > +    err = pathname_concat(path, bpf_map__name(map), buf);
> > +    if (err)
> > +        return err;
> > +
> >       return bpf_map__set_pin_path(map, buf);
> >   }
>
> > @@ -7959,17 +7970,8 @@ int bpf_object__pin_maps(struct bpf_object 
> > *obj, const char *path)
> >               continue;
>
> >           if (path) {
> > -            int len;
> > -
> > -            len = snprintf(buf, PATH_MAX, "%s/%s", path,
> > -                       bpf_map__name(map));
> > -            if (len < 0) {
> > -                err = -EINVAL;
> > -                goto err_unpin_maps;
> > -            } else if (len >= PATH_MAX) {
> > -                err = -ENAMETOOLONG;
>
> [..]
>
> > +            if (pathname_concat(path, bpf_map__name(map), buf))
> >                   goto err_unpin_maps;
> > -            }
>
> You're breaking error reporting here and in a bunch of other places.
> Should be:
>
> err = pathname_concat();
> if (err)
>     goto err_unpin_maps;
Thanks for your comments.

Sure, my bad.

> I have the same attitude towards this patch as the first one in the
> series: not worth it. Nothing is currently broken, the code as is 
> relatively
> readable, this version is not much simpler, it just looks slightly 
> different
> taste-wise..
>
> How about this: if you really want to push this kind of cleanup, send
> selftests that exercise all these error cases? :-)

Ok. I will try.  :-)

> >               sanitize_pin_path(buf);
> >               pin_path = buf;
> >           } else if (!map->pin_path) {
> > @@ -8007,14 +8009,9 @@ int bpf_object__unpin_maps(struct bpf_object 
> > *obj, const char *path)
> >           char buf[PATH_MAX];
>
> >           if (path) {
> > -            int len;
> > -
> > -            len = snprintf(buf, PATH_MAX, "%s/%s", path,
> > -                       bpf_map__name(map));
> > -            if (len < 0)
> > -                return libbpf_err(-EINVAL);
> > -            else if (len >= PATH_MAX)
> > -                return libbpf_err(-ENAMETOOLONG);
> > +            err = pathname_concat(path, bpf_map__name(map), buf);
> > +            if (err)
> > +                return err;
> >               sanitize_pin_path(buf);
> >               pin_path = buf;
> >           } else if (!map->pin_path) {
> > @@ -8032,6 +8029,7 @@ int bpf_object__unpin_maps(struct bpf_object 
> > *obj, const char *path)
> >   int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
> >   {
> >       struct bpf_program *prog;
> > +    char buf[PATH_MAX];
> >       int err;
>
> >       if (!obj)
> > @@ -8043,17 +8041,8 @@ int bpf_object__pin_programs(struct bpf_object 
> > *obj, const char *path)
> >       }
>
> >       bpf_object__for_each_program(prog, obj) {
> > -        char buf[PATH_MAX];
> > -        int len;
> > -
> > -        len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
> > -        if (len < 0) {
> > -            err = -EINVAL;
> > +        if (pathname_concat(path, prog->name, buf))
> >               goto err_unpin_programs;
> > -        } else if (len >= PATH_MAX) {
> > -            err = -ENAMETOOLONG;
> > -            goto err_unpin_programs;
> > -        }
>
> >           err = bpf_program__pin(prog, buf);
> >           if (err)
> > @@ -8064,13 +8053,7 @@ int bpf_object__pin_programs(struct bpf_object 
> > *obj, const char *path)
>
> >   err_unpin_programs:
> >       while ((prog = bpf_object__prev_program(obj, prog))) {
> > -        char buf[PATH_MAX];
> > -        int len;
> > -
> > -        len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
> > -        if (len < 0)
> > -            continue;
> > -        else if (len >= PATH_MAX)
> > +        if (pathname_concat(path, prog->name, buf))
> >               continue;
>
> >           bpf_program__unpin(prog, buf);
> > @@ -8089,13 +8072,10 @@ int bpf_object__unpin_programs(struct 
> > bpf_object *obj, const char *path)
>
> >       bpf_object__for_each_program(prog, obj) {
> >           char buf[PATH_MAX];
> > -        int len;
>
> > -        len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
> > -        if (len < 0)
> > -            return libbpf_err(-EINVAL);
> > -        else if (len >= PATH_MAX)
> > -            return libbpf_err(-ENAMETOOLONG);
> > +        err = pathname_concat(path, prog->name, buf);
> > +        if (err)
> > +            return libbpf_err(err);
>
> >           err = bpf_program__unpin(prog, buf);
> >           if (err)
> > --
> > 1.8.3.1