Re: [PATCH bpf-next v5 4/9] bpftool: Add struct definitions and helpers for BTFGen

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Fri, Jan 28, 2022 at 2:33 PM Mauricio Vásquez <mauricio@kinvolk.io> wrote:
>
> Add some structs and helpers that will be used by BTFGen in the next
> commits.
>
> Signed-off-by: Mauricio Vásquez <mauricio@kinvolk.io>
> Signed-off-by: Rafael David Tinoco <rafael.tinoco@aquasec.com>
> Signed-off-by: Lorenzo Fontana <lorenzo.fontana@elastic.co>
> Signed-off-by: Leonardo Di Donato <leonardo.didonato@elastic.co>
> ---

Similar considerations with unused static functions. It's also harder
to review when I don't see how these types are actually used, so
probably better to put it in relevant patches that are using this?

>  tools/bpf/bpftool/gen.c | 75 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 75 insertions(+)
>
> diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
> index 64371f466fa6..68bb88e86b27 100644
> --- a/tools/bpf/bpftool/gen.c
> +++ b/tools/bpf/bpftool/gen.c
> @@ -1118,6 +1118,81 @@ static int btf_save_raw(const struct btf *btf, const char *path)
>         return err;
>  }
>
> +struct btfgen_type {
> +       struct btf_type *type;
> +       unsigned int id;
> +};
> +
> +struct btfgen_info {
> +       struct hashmap *types;
> +       struct btf *src_btf;
> +};
> +
> +static size_t btfgen_hash_fn(const void *key, void *ctx)
> +{
> +       return (size_t)key;
> +}
> +
> +static bool btfgen_equal_fn(const void *k1, const void *k2, void *ctx)
> +{
> +       return k1 == k2;
> +}
> +
> +static void *uint_as_hash_key(int x)
> +{
> +       return (void *)(uintptr_t)x;
> +}
> +
> +static void btfgen_free_type(struct btfgen_type *type)
> +{
> +       free(type);
> +}
> +
> +static void btfgen_free_info(struct btfgen_info *info)
> +{
> +       struct hashmap_entry *entry;
> +       size_t bkt;
> +
> +       if (!info)
> +               return;
> +
> +       if (!IS_ERR_OR_NULL(info->types)) {
> +               hashmap__for_each_entry(info->types, entry, bkt) {
> +                       btfgen_free_type(entry->value);
> +               }
> +               hashmap__free(info->types);
> +       }
> +
> +       btf__free(info->src_btf);
> +
> +       free(info);
> +}
> +
> +static struct btfgen_info *
> +btfgen_new_info(const char *targ_btf_path)
> +{
> +       struct btfgen_info *info;
> +
> +       info = calloc(1, sizeof(*info));
> +       if (!info)
> +               return NULL;
> +
> +       info->src_btf = btf__parse(targ_btf_path, NULL);
> +       if (libbpf_get_error(info->src_btf)) {

bpftool is using libbpf 1.0 mode, so don't use libbpf_get_error()
anymore, just check for NULL

also, if you are using errno for propagating error, you need to store
it locally before btfgen_free_info() call, otherwise it can be
clobbered

> +               btfgen_free_info(info);
> +               return NULL;
> +       }
> +
> +       info->types = hashmap__new(btfgen_hash_fn, btfgen_equal_fn, NULL);
> +       if (IS_ERR(info->types)) {
> +               errno = -PTR_ERR(info->types);
> +               btfgen_free_info(info);
> +               return NULL;
> +       }
> +
> +       return info;
> +}
> +
>  /* Create BTF file for a set of BPF objects */
>  static int btfgen(const char *src_btf, const char *dst_btf, const char *objspaths[])
>  {
> --
> 2.25.1
>