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Wed, 20 May 2026 21:08:31 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Thu, 21 May 2026 00:08:30 -0400 Message-Id: Cc: "Peter Zijlstra" , "Catalin Marinas" , "Will Deacon" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Dave Hansen" , "Andrew Morton" , "David Hildenbrand" , "Mike Rapoport" , "Emil Tsalapatis" , , , , , , Subject: Re: [PATCH 5/8] bpf/arena: Add bpf_arena_map_kern_vm_start() and bpf_prog_arena() From: "Emil Tsalapatis" To: "Tejun Heo" , "David Vernet" , "Andrea Righi" , "Changwoo Min" , "Alexei Starovoitov" , "Andrii Nakryiko" , "Daniel Borkmann" , "Martin KaFai Lau" , "Kumar Kartikeya Dwivedi" X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260520235052.4180316-1-tj@kernel.org> <20260520235052.4180316-6-tj@kernel.org> In-Reply-To: <20260520235052.4180316-6-tj@kernel.org> On Wed May 20, 2026 at 7:50 PM EDT, Tejun Heo wrote: > struct bpf_arena is opaque to callers outside arena.c. Add two helpers > for struct_ops subsystems that need to reach into an arena: > > bpf_arena_map_kern_vm_start(struct bpf_map *map) > returns @map's kern_vm_start. A sched_ext follow-up needs this > to translate kern_va <-> uaddr. > > bpf_prog_arena(struct bpf_prog *prog) > returns the bpf_map of the arena referenced by @prog (NULL if > @prog references no arena). The verifier enforces at most one > arena per program. Used by struct_ops callers that auto-discover > an arena from a member prog and need to take a map reference. > > Suggested-by: Kumar Kartikeya Dwivedi > Signed-off-by: Tejun Heo Reviewed-by: Emil Tsalapatis > --- > include/linux/bpf.h | 2 ++ > kernel/bpf/arena.c | 26 ++++++++++++++++++++++++++ > 2 files changed, 28 insertions(+) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index 5b99d786e98c..e1ba57c10aaa 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -618,6 +618,8 @@ void bpf_rb_root_free(const struct btf_field *field, = void *rb_root, > struct bpf_spin_lock *spin_lock); > u64 bpf_arena_get_kern_vm_start(struct bpf_arena *arena); > u64 bpf_arena_get_user_vm_start(struct bpf_arena *arena); > +u64 bpf_arena_map_kern_vm_start(struct bpf_map *map); > +struct bpf_map *bpf_prog_arena(struct bpf_prog *prog); > int bpf_obj_name_cpy(char *dst, const char *src, unsigned int size); > =20 > struct bpf_offload_dev; > diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c > index a811cf6170fa..51b9ae36feb6 100644 > --- a/kernel/bpf/arena.c > +++ b/kernel/bpf/arena.c > @@ -84,6 +84,32 @@ u64 bpf_arena_get_user_vm_start(struct bpf_arena *aren= a) > return arena ? arena->user_vm_start : 0; > } > =20 > +/** > + * bpf_arena_map_kern_vm_start - kern_vm_start lookup by struct bpf_map = * > + * @map: a BPF_MAP_TYPE_ARENA map > + * > + * Return @map's kern_vm_start. > + */ > +u64 bpf_arena_map_kern_vm_start(struct bpf_map *map) > +{ > + return bpf_arena_get_kern_vm_start(container_of(map, struct bpf_arena, = map)); > +} > + > +/** > + * bpf_prog_arena - return the bpf_map of the arena referenced by @prog > + * @prog: a loaded BPF program > + * > + * The verifier enforces at most one arena per program and stores it in > + * prog->aux->arena. Return that arena's underlying bpf_map, or NULL if > + * @prog does not reference an arena. > + */ > +struct bpf_map *bpf_prog_arena(struct bpf_prog *prog) > +{ > + struct bpf_arena *arena =3D prog->aux->arena; > + > + return arena ? &arena->map : NULL; > +} > + > static long arena_map_peek_elem(struct bpf_map *map, void *value) > { > return -EOPNOTSUPP;