Commit 8fc3d2d8 authored by Emil Tsalapatis's avatar Emil Tsalapatis Committed by Alexei Starovoitov
Browse files

bpf/arena: add bpf_arena_reserve_pages kfunc 



Add a new BPF arena kfunc for reserving a range of arena virtual
addresses without backing them with pages. This prevents the range from
being populated using bpf_arena_alloc_pages().

Acked-by: default avatarYonghong Song <yonghong.song@linux.dev>
Signed-off-by: default avatarEmil Tsalapatis <emil@etsalapatis.com>
Acked-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250709191312.29840-2-emil@etsalapatis.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent ad97cb2e

kernel/bpf/arena.c

+43 −0
Original line number Diff line number Diff line
@@ -550,6 +550,34 @@ static void arena_free_pages(struct bpf_arena *arena, long uaddr, long page_cnt) 
	}

}



/*

 * Reserve an arena virtual address range without populating it. This call stops

 * bpf_arena_alloc_pages from adding pages to this range.

 */

static int arena_reserve_pages(struct bpf_arena *arena, long uaddr, u32 page_cnt)

{

	long page_cnt_max = (arena->user_vm_end - arena->user_vm_start) >> PAGE_SHIFT;

	long pgoff;

	int ret;



	if (uaddr & ~PAGE_MASK)

		return 0;



	pgoff = compute_pgoff(arena, uaddr);

	if (pgoff + page_cnt > page_cnt_max)

		return -EINVAL;



	guard(mutex)(&arena->lock);



	/* Cannot guard already allocated pages. */

	ret = is_range_tree_set(&arena->rt, pgoff, page_cnt);

	if (ret)

		return -EBUSY;



	/* "Allocate" the region to prevent it from being allocated. */

	return range_tree_clear(&arena->rt, pgoff, page_cnt);

}



__bpf_kfunc_start_defs();



__bpf_kfunc void *bpf_arena_alloc_pages(void *p__map, void *addr__ign, u32 page_cnt,
@@ -573,11 +601,26 @@ __bpf_kfunc void bpf_arena_free_pages(void *p__map, void *ptr__ign, u32 page_cnt 
		return;

	arena_free_pages(arena, (long)ptr__ign, page_cnt);

}



__bpf_kfunc int bpf_arena_reserve_pages(void *p__map, void *ptr__ign, u32 page_cnt)

{

	struct bpf_map *map = p__map;

	struct bpf_arena *arena = container_of(map, struct bpf_arena, map);



	if (map->map_type != BPF_MAP_TYPE_ARENA)

		return -EINVAL;



	if (!page_cnt)

		return 0;



	return arena_reserve_pages(arena, (long)ptr__ign, page_cnt);

}

__bpf_kfunc_end_defs();



BTF_KFUNCS_START(arena_kfuncs)

BTF_ID_FLAGS(func, bpf_arena_alloc_pages, KF_TRUSTED_ARGS | KF_SLEEPABLE | KF_ARENA_RET | KF_ARENA_ARG2)

BTF_ID_FLAGS(func, bpf_arena_free_pages, KF_TRUSTED_ARGS | KF_SLEEPABLE | KF_ARENA_ARG2)

BTF_ID_FLAGS(func, bpf_arena_reserve_pages, KF_TRUSTED_ARGS | KF_SLEEPABLE | KF_ARENA_ARG2)

BTF_KFUNCS_END(arena_kfuncs)



static const struct btf_kfunc_id_set common_kfunc_set = {