[DTrace-devel] [PATCH 4/5] Implement dt_bpf_map_lookup_inner() and dt_bpf_map_update_inner()

[Kris Van Hees]

On Mon, Aug 22, 2022 at 03:18:30PM -0400, Eugene Loh wrote:
> Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
> 
> For the dt_bpf_map_get_fd_by_id() comment, I assume:
> s/based on it id/based on its id/

Thanks.

> Personally, instead of key1/key2, it'd be better to stick to the in/out
> terminology that is otherwise used.  In fact, converting "name[key1][key2]" to
> the in/out terminology would be a nice way of illustrating what in/out mean.

Good point.

> Will dt_bpf_map_get_fd_by_id() be used outside this file?  That is, should it
> be "static" rather than declared in dt_bpf.h?

It is an API function and as such would properly not be declared static, so
that it can be used from coce outside this file.

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> From: Kris Van Hees via DTrace-devel <dtrace-devel at oss.oracle.com>
> Sent: Friday, August 19, 2022 10:26 AM
> To: dtrace-devel at oss.oracle.com <dtrace-devel at oss.oracle.com>
> Subject: [DTrace-devel] [PATCH 4/5] Implement dt_bpf_map_lookup_inner() and
> dt_bpf_map_update_inner()
>  
> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> ---
>  libdtrace/dt_bpf.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++
>  libdtrace/dt_bpf.h |  5 ++++
>  2 files changed, 64 insertions(+)
> 
> diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c
> index 7a886278..66c76022 100644
> --- a/libdtrace/dt_bpf.c
> +++ b/libdtrace/dt_bpf.c
> @@ -164,6 +164,20 @@ dt_bpf_map_create_meta(enum bpf_map_type otype, const char
> *name,
>          return ofd;
>  }
>  
> +/*
> + * Get a file descriptor for a BPF map based on it id.
> + */
> +int
> +dt_bpf_map_get_fd_by_id(uint32_t id)
> +{
> +       union bpf_attr  attr;
> +
> +       memset(&attr, 0, sizeof(attr));
> +       attr.map_id = id;
> +
> +       return bpf(BPF_MAP_GET_FD_BY_ID, &attr);
> +}
> +
>  /*
>   * Load the value for the given key in the map referenced by the given fd.
>   */
> @@ -228,6 +242,51 @@ dt_bpf_map_update(int fd, const void *key, const void
> *val)
>          return bpf(BPF_MAP_UPDATE_ELEM, &attr);
>  }
>  
> +/*
> + * Retrieve the value in a map-of-maps, i.e. map[key1][key2] = value.
> + */
> +int
> +dt_bpf_map_lookup_inner(int fd, const void *key1, const void *key2, void *val)
> +{
> +       uint32_t        id;
> +       int             rc;
> +
> +       if (dt_bpf_map_lookup(fd, key1, &id) < 0)
> +               return -1;
> +
> +       fd = dt_bpf_map_get_fd_by_id(id);
> +       if (fd < 0)
> +               return -1;
> +
> +       rc = dt_bpf_map_lookup(fd, key2, val);
> +       close(fd);
> +
> +       return rc;
> +}
> +
> +/*
> + * Store the value in a map-of-maps, i.e. map[key1][key2] = value.
> + */
> +int
> +dt_bpf_map_update_inner(int fd, const void *key1, const void *key2,
> +                       const void *val)
> +{
> +       uint32_t        id;
> +       int             rc;
> +
> +       if (dt_bpf_map_lookup(fd, key1, &id) < 0)
> +               return -1;
> +
> +       fd = dt_bpf_map_get_fd_by_id(id);
> +       if (fd < 0)
> +               return -1;
> +
> +       rc = dt_bpf_map_update(fd, key2, val);
> +       close(fd);
> +
> +       return rc;
> +}
> +
>  static int
>  have_helper(uint32_t func_id)
>  {
> diff --git a/libdtrace/dt_bpf.h b/libdtrace/dt_bpf.h
> index f8c75012..7a16c03d 100644
> --- a/libdtrace/dt_bpf.h
> +++ b/libdtrace/dt_bpf.h
> @@ -50,6 +50,11 @@ extern int dt_bpf_map_lookup(int fd, const void *key, void
> *val);
>  extern int dt_bpf_map_next_key(int fd, const void *key, void *nxt);
>  extern int dt_bpf_map_update(int fd, const void *key, const void *val);
>  extern int dt_bpf_map_delete(int fd, const void *key);
> +extern int dt_bpf_map_get_fd_by_id(uint32_t id);
> +extern int dt_bpf_map_lookup_inner(int fd, const void *key1, const void *key2,
> +                                  void *val);
> +extern int dt_bpf_map_update_inner(int fd, const void *key1, const void *key2,
> +                                  const void *val);
>  extern int dt_bpf_load_progs(struct dtrace_hdl *, uint_t);
>  extern void dt_bpf_init_helpers(struct dtrace_hdl *dtp);
>  
> --
> 2.34.1
> 
> 
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