diff mbox series

[bpf-next,v3,03/15] libbpf: honor autocreate flag for struct_ops maps

Message ID 20240304225156.24765-4-eddyz87@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series libbpf: type suffixes and autocreate flag for struct_ops maps | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/apply fail Patch does not apply to bpf-next-0
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bpf/vmtest-bpf-next-PR fail PR summary
bpf/vmtest-bpf-next-VM_Test-13 fail Logs for s390x-gcc / test (test_maps, false, 360) / test_maps on s390x with gcc
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Commit Message

Eduard Zingerman March 4, 2024, 10:51 p.m. UTC 
Skip load steps for struct_ops maps not marked for automatic creation.
This should allow to load bpf object in situations like below:

    SEC("struct_ops/foo") int BPF_PROG(foo) { ... }
    SEC("struct_ops/bar") int BPF_PROG(bar) { ... }

    struct test_ops___v1 {
    	int (*foo)(void);
    };

    struct test_ops___v2 {
    	int (*foo)(void);
    	int (*does_not_exist)(void);
    };

    SEC(".struct_ops.link")
    struct test_ops___v1 map_for_old = {
    	.test_1 = (void *)foo
    };

    SEC(".struct_ops.link")
    struct test_ops___v2 map_for_new = {
    	.test_1 = (void *)foo,
    	.does_not_exist = (void *)bar
    };

Suppose program is loaded on old kernel that does not have definition
for 'does_not_exist' struct_ops member. After this commit it would be
possible to load such object file after the following tweaks:

    bpf_program__set_autoload(skel->progs.bar, false);
    bpf_map__set_autocreate(skel->maps.map_for_new, false);

Acked-by: David Vernet <void@manifault.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 tools/lib/bpf/libbpf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Andrii Nakryiko March 5, 2024, 7:19 p.m. UTC | #1 
On Mon, Mar 4, 2024 at 2:52 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> Skip load steps for struct_ops maps not marked for automatic creation.
> This should allow to load bpf object in situations like below:
>
>     SEC("struct_ops/foo") int BPF_PROG(foo) { ... }
>     SEC("struct_ops/bar") int BPF_PROG(bar) { ... }
>
>     struct test_ops___v1 {
>         int (*foo)(void);
>     };
>
>     struct test_ops___v2 {
>         int (*foo)(void);
>         int (*does_not_exist)(void);
>     };
>
>     SEC(".struct_ops.link")
>     struct test_ops___v1 map_for_old = {
>         .test_1 = (void *)foo
>     };
>
>     SEC(".struct_ops.link")
>     struct test_ops___v2 map_for_new = {
>         .test_1 = (void *)foo,
>         .does_not_exist = (void *)bar
>     };
>
> Suppose program is loaded on old kernel that does not have definition
> for 'does_not_exist' struct_ops member. After this commit it would be
> possible to load such object file after the following tweaks:
>
>     bpf_program__set_autoload(skel->progs.bar, false);
>     bpf_map__set_autocreate(skel->maps.map_for_new, false);
>
> Acked-by: David Vernet <void@manifault.com>
> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
> ---
>  tools/lib/bpf/libbpf.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 2c0cb72bc7a4..25c452c20d7d 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -1209,7 +1209,7 @@ static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
>         for (i = 0; i < obj->nr_maps; i++) {
>                 map = &obj->maps[i];
>
> -               if (!bpf_map__is_struct_ops(map))
> +               if (!bpf_map__is_struct_ops(map) || !map->autocreate)

tbh, I'd keep them as separate checks (they check very different
aspects, so feels appropriate to not combine them in one check)

>                         continue;
>
>                 err = bpf_map__init_kern_struct_ops(map);
> @@ -8136,7 +8136,7 @@ static int bpf_object_prepare_struct_ops(struct bpf_object *obj)
>         int i;
>
>         for (i = 0; i < obj->nr_maps; i++)
> -               if (bpf_map__is_struct_ops(&obj->maps[i]))
> +               if (bpf_map__is_struct_ops(&obj->maps[i]) && obj->maps[i].autocreate)

especially here, this becomes a bit convoluted

how about we make it a bit more verbose, but also straightforward

map = &obj->maps[i];
if (!bpf_map__is_struct_ops(map))
    continue;
if (!map->autocreate)
    continue;
bpf_map_prepare_vdata(...)


It will also mirror the structure in bpf_object__init_kern_struct_ops_maps()

>                         bpf_map_prepare_vdata(&obj->maps[i]);
>
>         return 0;
> --
> 2.43.0
>
Eduard Zingerman March 5, 2024, 11:50 p.m. UTC | #2 
On Tue, 2024-03-05 at 11:19 -0800, Andrii Nakryiko wrote:
[...]

> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 2c0cb72bc7a4..25c452c20d7d 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -1209,7 +1209,7 @@ static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
> >         for (i = 0; i < obj->nr_maps; i++) {
> >                 map = &obj->maps[i];
> > 
> > -               if (!bpf_map__is_struct_ops(map))
> > +               if (!bpf_map__is_struct_ops(map) || !map->autocreate)
> 
> tbh, I'd keep them as separate checks (they check very different
> aspects, so feels appropriate to not combine them in one check)
> 
> >                         continue;
> > 
> >                 err = bpf_map__init_kern_struct_ops(map);
> > @@ -8136,7 +8136,7 @@ static int bpf_object_prepare_struct_ops(struct bpf_object *obj)
> >         int i;
> > 
> >         for (i = 0; i < obj->nr_maps; i++)
> > -               if (bpf_map__is_struct_ops(&obj->maps[i]))
> > +               if (bpf_map__is_struct_ops(&obj->maps[i]) && obj->maps[i].autocreate)
> 
> especially here, this becomes a bit convoluted
> 
> how about we make it a bit more verbose, but also straightforward
> 
> map = &obj->maps[i];
> if (!bpf_map__is_struct_ops(map))
>     continue;
> if (!map->autocreate)
>     continue;
> bpf_map_prepare_vdata(...)

Ok, will do

[...]
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2c0cb72bc7a4..25c452c20d7d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1209,7 +1209,7 @@  static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
 	for (i = 0; i < obj->nr_maps; i++) {
 		map = &obj->maps[i];
 
-		if (!bpf_map__is_struct_ops(map))
+		if (!bpf_map__is_struct_ops(map) || !map->autocreate)
 			continue;
 
 		err = bpf_map__init_kern_struct_ops(map);
@@ -8136,7 +8136,7 @@  static int bpf_object_prepare_struct_ops(struct bpf_object *obj)
 	int i;
 
 	for (i = 0; i < obj->nr_maps; i++)
-		if (bpf_map__is_struct_ops(&obj->maps[i]))
+		if (bpf_map__is_struct_ops(&obj->maps[i]) && obj->maps[i].autocreate)
 			bpf_map_prepare_vdata(&obj->maps[i]);
 
 	return 0;