[bpf-next,12/16] libbpf: Allow specifying 64-bit integers in map BTF.

Commit Message

Alexei Starovoitov Feb. 6, 2024, 10:04 p.m. UTC

From: Alexei Starovoitov <[e-mail]>

__uint() macro that is used to specify map attributes like:
  __uint(type, BPF_MAP_TYPE_ARRAY);
  __uint(map_flags, BPF_F_MMAPABLE);
is limited to 32-bit, since BTF_KIND_ARRAY has u32 "number of elements" field.

Introduce __ulong() macro that allows specifying values bigger than 32-bit.
In map definition "map_extra" is the only u64 field.

Signed-off-by: Alexei Starovoitov <[e-mail]>
---
 tools/lib/bpf/bpf_helpers.h |  1 +
 tools/lib/bpf/libbpf.c      | 44 ++++++++++++++++++++++++++++++++++---
 2 files changed, 42 insertions(+), 3 deletions(-)

Comments

Andrii Nakryiko Feb. 8, 2024, 1:16 a.m. UTC | #1

On Tue, Feb 6, 2024 at 2:05 PM Alexei Starovoitov
<[e-mail]> wrote:
>
> From: Alexei Starovoitov <[e-mail]>
>
> __uint() macro that is used to specify map attributes like:
>   __uint(type, BPF_MAP_TYPE_ARRAY);
>   __uint(map_flags, BPF_F_MMAPABLE);
> is limited to 32-bit, since BTF_KIND_ARRAY has u32 "number of elements" field.
>
> Introduce __ulong() macro that allows specifying values bigger than 32-bit.
> In map definition "map_extra" is the only u64 field.
>
> Signed-off-by: Alexei Starovoitov <[e-mail]>
> ---
>  tools/lib/bpf/bpf_helpers.h |  1 +
>  tools/lib/bpf/libbpf.c      | 44 ++++++++++++++++++++++++++++++++++---
>  2 files changed, 42 insertions(+), 3 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> index 9c777c21da28..fb909fc6866d 100644
> --- a/tools/lib/bpf/bpf_helpers.h
> +++ b/tools/lib/bpf/bpf_helpers.h
> @@ -13,6 +13,7 @@
>  #define __uint(name, val) int (*name)[val]
>  #define __type(name, val) typeof(val) *name
>  #define __array(name, val) typeof(val) *name[]
> +#define __ulong(name, val) enum name##__enum { name##__value = val } name

Can you try using __ulong() twice in the same file? enum type and
value names have global visibility, so I suspect second use with the
same field name would cause compilation error

>
>  /*
>   * Helper macro to place programs, maps, license in
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index c5ce5946dc6d..a8c89b2315cd 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2229,6 +2229,39 @@ static bool get_map_field_int(const char *map_name, const struct btf *btf,
>         return true;
>  }
>
> +static bool get_map_field_long(const char *map_name, const struct btf *btf,
> +                              const struct btf_member *m, __u64 *res)
> +{
> +       const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
> +       const char *name = btf__name_by_offset(btf, m->name_off);
> +
> +       if (btf_is_ptr(t))
> +               return false;
> +
> +       if (!btf_is_enum(t) && !btf_is_enum64(t)) {
> +               pr_warn("map '%s': attr '%s': expected enum or enum64, got %s.\n",
> +                       map_name, name, btf_kind_str(t));
> +               return false;
> +       }
> +
> +       if (btf_vlen(t) != 1) {
> +               pr_warn("map '%s': attr '%s': invalid __ulong\n",
> +                       map_name, name);
> +               return false;
> +       }
> +
> +       if (btf_is_enum(t)) {
> +               const struct btf_enum *e = btf_enum(t);
> +
> +               *res = e->val;
> +       } else {
> +               const struct btf_enum64 *e = btf_enum64(t);
> +
> +               *res = btf_enum64_value(e);
> +       }
> +       return true;
> +}
> +
>  static int pathname_concat(char *buf, size_t buf_sz, const char *path, const char *name)
>  {
>         int len;
> @@ -2462,10 +2495,15 @@ int parse_btf_map_def(const char *map_name, struct btf *btf,
>                         map_def->pinning = val;
>                         map_def->parts |= MAP_DEF_PINNING;
>                 } else if (strcmp(name, "map_extra") == 0) {
> -                       __u32 map_extra;
> +                       __u64 map_extra;
>
> -                       if (!get_map_field_int(map_name, btf, m, &map_extra))
> -                               return -EINVAL;
> +                       if (!get_map_field_long(map_name, btf, m, &map_extra)) {
> +                               __u32 map_extra_u32;
> +
> +                               if (!get_map_field_int(map_name, btf, m, &map_extra_u32))
> +                                       return -EINVAL;
> +                               map_extra = map_extra_u32;
> +                       }
>                         map_def->map_extra = map_extra;
>                         map_def->parts |= MAP_DEF_MAP_EXTRA;
>                 } else {
> --
> 2.34.1
>

Alexei Starovoitov Feb. 8, 2024, 1:58 a.m. UTC | #2

On Wed, Feb 7, 2024 at 5:17 PM Andrii Nakryiko
<[e-mail]> wrote:
>
> On Tue, Feb 6, 2024 at 2:05 PM Alexei Starovoitov
> <[e-mail]> wrote:
> >
> > From: Alexei Starovoitov <[e-mail]>
> >
> > __uint() macro that is used to specify map attributes like:
> >   __uint(type, BPF_MAP_TYPE_ARRAY);
> >   __uint(map_flags, BPF_F_MMAPABLE);
> > is limited to 32-bit, since BTF_KIND_ARRAY has u32 "number of elements" field.
> >
> > Introduce __ulong() macro that allows specifying values bigger than 32-bit.
> > In map definition "map_extra" is the only u64 field.
> >
> > Signed-off-by: Alexei Starovoitov <[e-mail]>
> > ---
> >  tools/lib/bpf/bpf_helpers.h |  1 +
> >  tools/lib/bpf/libbpf.c      | 44 ++++++++++++++++++++++++++++++++++---
> >  2 files changed, 42 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> > index 9c777c21da28..fb909fc6866d 100644
> > --- a/tools/lib/bpf/bpf_helpers.h
> > +++ b/tools/lib/bpf/bpf_helpers.h
> > @@ -13,6 +13,7 @@
> >  #define __uint(name, val) int (*name)[val]
> >  #define __type(name, val) typeof(val) *name
> >  #define __array(name, val) typeof(val) *name[]
> > +#define __ulong(name, val) enum name##__enum { name##__value = val } name
>
> Can you try using __ulong() twice in the same file? enum type and
> value names have global visibility, so I suspect second use with the
> same field name would cause compilation error

Good point will change it to:

#define __ulong(name, val) enum { __PASTE(__unique_value,__COUNTER__)
= val } name

Andrii Nakryiko Feb. 8, 2024, 6:16 p.m. UTC | #3

On Wed, Feb 7, 2024 at 5:59 PM Alexei Starovoitov
<[e-mail]> wrote:
>
> On Wed, Feb 7, 2024 at 5:17 PM Andrii Nakryiko
> <[e-mail]> wrote:
> >
> > On Tue, Feb 6, 2024 at 2:05 PM Alexei Starovoitov
> > <[e-mail]> wrote:
> > >
> > > From: Alexei Starovoitov <[e-mail]>
> > >
> > > __uint() macro that is used to specify map attributes like:
> > >   __uint(type, BPF_MAP_TYPE_ARRAY);
> > >   __uint(map_flags, BPF_F_MMAPABLE);
> > > is limited to 32-bit, since BTF_KIND_ARRAY has u32 "number of elements" field.
> > >
> > > Introduce __ulong() macro that allows specifying values bigger than 32-bit.
> > > In map definition "map_extra" is the only u64 field.
> > >
> > > Signed-off-by: Alexei Starovoitov <[e-mail]>
> > > ---
> > >  tools/lib/bpf/bpf_helpers.h |  1 +
> > >  tools/lib/bpf/libbpf.c      | 44 ++++++++++++++++++++++++++++++++++---
> > >  2 files changed, 42 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> > > index 9c777c21da28..fb909fc6866d 100644
> > > --- a/tools/lib/bpf/bpf_helpers.h
> > > +++ b/tools/lib/bpf/bpf_helpers.h
> > > @@ -13,6 +13,7 @@
> > >  #define __uint(name, val) int (*name)[val]
> > >  #define __type(name, val) typeof(val) *name
> > >  #define __array(name, val) typeof(val) *name[]
> > > +#define __ulong(name, val) enum name##__enum { name##__value = val } name
> >
> > Can you try using __ulong() twice in the same file? enum type and
> > value names have global visibility, so I suspect second use with the
> > same field name would cause compilation error
>
> Good point will change it to:
>
> #define __ulong(name, val) enum { __PASTE(__unique_value,__COUNTER__)
> = val } name

yep, that should work. We still can have name collisions across
multiple files, but it doesn't matter when linking two .bpf.o files.

Patch

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index 9c777c21da28..fb909fc6866d 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -13,6 +13,7 @@ 
 #define __uint(name, val) int (*name)[val]
 #define __type(name, val) typeof(val) *name
 #define __array(name, val) typeof(val) *name[]
+#define __ulong(name, val) enum name##__enum { name##__value = val } name
 
 /*
  * Helper macro to place programs, maps, license in
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index c5ce5946dc6d..a8c89b2315cd 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2229,6 +2229,39 @@  static bool get_map_field_int(const char *map_name, const struct btf *btf,
 	return true;
 }
 
+static bool get_map_field_long(const char *map_name, const struct btf *btf,
+			       const struct btf_member *m, __u64 *res)
+{
+	const struct btf_type *t = skip_mods_and_typedefs(btf, m->type, NULL);
+	const char *name = btf__name_by_offset(btf, m->name_off);
+
+	if (btf_is_ptr(t))
+		return false;
+
+	if (!btf_is_enum(t) && !btf_is_enum64(t)) {
+		pr_warn("map '%s': attr '%s': expected enum or enum64, got %s.\n",
+			map_name, name, btf_kind_str(t));
+		return false;
+	}
+
+	if (btf_vlen(t) != 1) {
+		pr_warn("map '%s': attr '%s': invalid __ulong\n",
+			map_name, name);
+		return false;
+	}
+
+	if (btf_is_enum(t)) {
+		const struct btf_enum *e = btf_enum(t);
+
+		*res = e->val;
+	} else {
+		const struct btf_enum64 *e = btf_enum64(t);
+
+		*res = btf_enum64_value(e);
+	}
+	return true;
+}
+
 static int pathname_concat(char *buf, size_t buf_sz, const char *path, const char *name)
 {
 	int len;
@@ -2462,10 +2495,15 @@  int parse_btf_map_def(const char *map_name, struct btf *btf,
 			map_def->pinning = val;
 			map_def->parts |= MAP_DEF_PINNING;
 		} else if (strcmp(name, "map_extra") == 0) {
-			__u32 map_extra;
+			__u64 map_extra;
 
-			if (!get_map_field_int(map_name, btf, m, &map_extra))
-				return -EINVAL;
+			if (!get_map_field_long(map_name, btf, m, &map_extra)) {
+				__u32 map_extra_u32;
+
+				if (!get_map_field_int(map_name, btf, m, &map_extra_u32))
+					return -EINVAL;
+				map_extra = map_extra_u32;
+			}
 			map_def->map_extra = map_extra;
 			map_def->parts |= MAP_DEF_MAP_EXTRA;
 		} else {