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bpf: Introduce internal definitions for UAPI-opaque bpf_{rb,list}_node 

Structs bpf_rb_node and bpf_list_node are opaquely defined in
uapi/linux/bpf.h, as BPF program writers are not expected to touch their
fields - nor does the verifier allow them to do so.

Currently these structs are simple wrappers around structs rb_node and
list_head and linked_list / rbtree implementation just casts and passes
to library functions for those data structures. Later patches in this
series, though, will add an "owner" field to bpf_{rb,list}_node, such
that they're not just wrapping an underlying node type. Moreover, the
bpf linked_list and rbtree implementations will deal with these owner
pointers directly in a few different places.

To avoid having to do

  void *owner = (void*)bpf_list_node + sizeof(struct list_head)

with opaque UAPI node types, add bpf_{list,rb}_node_kern struct
definitions to internal headers and modify linked_list and rbtree to use
the internal types where appropriate.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230718083813.3416104-3-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Dave Marchevsky 2023-07-18 01:38:09 -07:00 committed by Alexei Starovoitov
parent 60cc1f7d06
commit 0a1f7bfe35
2 changed files with 23 additions and 10 deletions
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10
include/linux/bpf.h
View File

@ -228,6 +228,16 @@ struct btf_record {
struct btf_field fields[];
};
/* Non-opaque version of bpf_rb_node in uapi/linux/bpf.h */
struct bpf_rb_node_kern {
struct rb_node rb_node;
} __attribute__((aligned(8)));
/* Non-opaque version of bpf_list_node in uapi/linux/bpf.h */
struct bpf_list_node_kern {
struct list_head list_head;
} __attribute__((aligned(8)));
struct bpf_map {
/* The first two cachelines with read-mostly members of which some
* are also accessed in fast-path (e.g. ops, max_entries).

23
kernel/bpf/helpers.c
View File

@ -1942,10 +1942,11 @@ __bpf_kfunc void *bpf_refcount_acquire_impl(void *p__refcounted_kptr, void *meta
return (void *)p__refcounted_kptr;
}
static int __bpf_list_add(struct bpf_list_node *node, struct bpf_list_head *head,
static int __bpf_list_add(struct bpf_list_node_kern *node,
struct bpf_list_head *head,
bool tail, struct btf_record *rec, u64 off)
{
struct list_head *n = (void *)node, *h = (void *)head;
struct list_head *n = &node->list_head, *h = (void *)head;
/* If list_head was 0-initialized by map, bpf_obj_init_field wasn't
* called on its fields, so init here
@ -1967,20 +1968,20 @@ __bpf_kfunc int bpf_list_push_front_impl(struct bpf_list_head *head,
struct bpf_list_node *node,
void *meta__ign, u64 off)
{
struct bpf_list_node_kern *n = (void *)node;
struct btf_struct_meta *meta = meta__ign;
return __bpf_list_add(node, head, false,
meta ? meta->record : NULL, off);
return __bpf_list_add(n, head, false, meta ? meta->record : NULL, off);
}
__bpf_kfunc int bpf_list_push_back_impl(struct bpf_list_head *head,
struct bpf_list_node *node,
void *meta__ign, u64 off)
{
struct bpf_list_node_kern *n = (void *)node;
struct btf_struct_meta *meta = meta__ign;
return __bpf_list_add(node, head, true,
meta ? meta->record : NULL, off);
return __bpf_list_add(n, head, true, meta ? meta->record : NULL, off);
}
static struct bpf_list_node *__bpf_list_del(struct bpf_list_head *head, bool tail)
@ -2013,7 +2014,7 @@ __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root,
struct bpf_rb_node *node)
{
struct rb_root_cached *r = (struct rb_root_cached *)root;
struct rb_node *n = (struct rb_node *)node;
struct rb_node *n = &((struct bpf_rb_node_kern *)node)->rb_node;
if (RB_EMPTY_NODE(n))
return NULL;
@ -2026,11 +2027,12 @@ __bpf_kfunc struct bpf_rb_node *bpf_rbtree_remove(struct bpf_rb_root *root,
/* Need to copy rbtree_add_cached's logic here because our 'less' is a BPF
* program
*/
static int __bpf_rbtree_add(struct bpf_rb_root *root, struct bpf_rb_node *node,
static int __bpf_rbtree_add(struct bpf_rb_root *root,
struct bpf_rb_node_kern *node,
void *less, struct btf_record *rec, u64 off)
{
struct rb_node **link = &((struct rb_root_cached *)root)->rb_root.rb_node;
struct rb_node *parent = NULL, *n = (struct rb_node *)node;
struct rb_node *parent = NULL, *n = &node->rb_node;
bpf_callback_t cb = (bpf_callback_t)less;
bool leftmost = true;
@ -2060,8 +2062,9 @@ __bpf_kfunc int bpf_rbtree_add_impl(struct bpf_rb_root *root, struct bpf_rb_node
void *meta__ign, u64 off)
{
struct btf_struct_meta *meta = meta__ign;
struct bpf_rb_node_kern *n = (void *)node;
return __bpf_rbtree_add(root, node, (void *)less, meta ? meta->record : NULL, off);
return __bpf_rbtree_add(root, n, (void *)less, meta ? meta->record : NULL, off);
}
__bpf_kfunc struct bpf_rb_node *bpf_rbtree_first(struct bpf_rb_root *root)