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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: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250709191312.29840-2-emil@etsalapatis.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
pull/1309/head
Emil Tsalapatis 2025-07-09 15:13:11 -04:00 committed by Alexei Starovoitov
parent ad97cb2ed0
commit 8fc3d2d8b5
1 changed files with 43 additions and 0 deletions
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43
kernel/bpf/arena.c
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@ -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_start_defs();
__bpf_kfunc void *bpf_arena_alloc_pages(void *p__map, void *addr__ign, u32 page_cnt, __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; return;
arena_free_pages(arena, (long)ptr__ign, page_cnt); 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(); __bpf_kfunc_end_defs();
BTF_KFUNCS_START(arena_kfuncs) 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_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_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) BTF_KFUNCS_END(arena_kfuncs)
static const struct btf_kfunc_id_set common_kfunc_set = { static const struct btf_kfunc_id_set common_kfunc_set = {