From: Kaitao Cheng <[email protected]> Allow bpf_kptr_xchg to directly operate on pointers marked with NON_OWN_REF | MEM_RCU.
In the example demonstrated in this patch, as long as "struct bpf_refcount ref" exists, the __kptr pointer is guaranteed to carry the MEM_RCU flag. The ref member itself does not need to be explicitly used. Signed-off-by: Kaitao Cheng <[email protected]> --- .../selftests/bpf/progs/rbtree_search_kptr.c | 123 ++++++++++++++++++ 1 file changed, 123 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/rbtree_search_kptr.c b/tools/testing/selftests/bpf/progs/rbtree_search_kptr.c index 069fc64b0167..610aae45e2dc 100644 --- a/tools/testing/selftests/bpf/progs/rbtree_search_kptr.c +++ b/tools/testing/selftests/bpf/progs/rbtree_search_kptr.c @@ -18,11 +18,21 @@ struct tree_node { struct node_data __kptr * node_data; }; +struct tree_node_ref { + struct bpf_refcount ref; + struct bpf_rb_node node; + u64 key; + struct node_data __kptr * node_data; +}; + #define private(name) SEC(".data." #name) __hidden __aligned(8) private(A) struct bpf_rb_root root __contains(tree_node, node); private(A) struct bpf_spin_lock lock; +private(B) struct bpf_rb_root root_r __contains(tree_node_ref, node); +private(B) struct bpf_spin_lock lock_r; + static bool less(struct bpf_rb_node *a, const struct bpf_rb_node *b) { struct tree_node *node_a, *node_b; @@ -130,6 +140,119 @@ long rbtree_search_kptr(void *ctx) return ret; } +static bool less_r(struct bpf_rb_node *a, const struct bpf_rb_node *b) +{ + struct tree_node_ref *node_a, *node_b; + + node_a = container_of(a, struct tree_node_ref, node); + node_b = container_of(b, struct tree_node_ref, node); + + return node_a->key < node_b->key; +} + +SEC("syscall") +__retval(0) +long rbtree_search_kptr_ref(void *ctx) +{ + struct tree_node_ref *tnode_r, *tnode_m; + struct bpf_rb_node *rb_n; + struct node_data __kptr * node_data; + int lookup_key = NR_NODES / 2; + int lookup_data = NR_NODES / 2; + int i, data, ret = 0; + + for (i = 0; i < NR_NODES && can_loop; i++) { + tnode_r = bpf_obj_new(typeof(*tnode_r)); + if (!tnode_r) + return __LINE__; + + node_data = bpf_obj_new(typeof(*node_data)); + if (!node_data) { + bpf_obj_drop(tnode_r); + return __LINE__; + } + + tnode_r->key = i; + node_data->data = i; + + node_data = bpf_kptr_xchg(&tnode_r->node_data, node_data); + if (node_data) + bpf_obj_drop(node_data); + + /* Unused reference */ + tnode_m = bpf_refcount_acquire(tnode_r); + if (!tnode_m) + return __LINE__; + + bpf_spin_lock(&lock_r); + bpf_rbtree_add(&root_r, &tnode_r->node, less_r); + bpf_spin_unlock(&lock_r); + + bpf_obj_drop(tnode_m); + } + + bpf_spin_lock(&lock_r); + rb_n = bpf_rbtree_root(&root_r); + while (rb_n && can_loop) { + tnode_r = container_of(rb_n, struct tree_node_ref, node); + node_data = bpf_kptr_xchg(&tnode_r->node_data, NULL); + if (!node_data) { + ret = __LINE__; + goto fail; + } + + data = node_data->data; + node_data = bpf_kptr_xchg(&tnode_r->node_data, node_data); + if (node_data) { + bpf_spin_unlock(&lock_r); + bpf_obj_drop(node_data); + return __LINE__; + } + + if (lookup_key == tnode_r->key) { + if (data == lookup_data) + break; + + ret = __LINE__; + goto fail; + } + + if (lookup_key < tnode_r->key) + rb_n = bpf_rbtree_left(&root_r, rb_n); + else + rb_n = bpf_rbtree_right(&root_r, rb_n); + } + bpf_spin_unlock(&lock_r); + + while (can_loop) { + bpf_spin_lock(&lock_r); + rb_n = bpf_rbtree_first(&root_r); + if (!rb_n) { + bpf_spin_unlock(&lock_r); + return 0; + } + + rb_n = bpf_rbtree_remove(&root_r, rb_n); + if (!rb_n) { + ret = __LINE__; + goto fail; + } + bpf_spin_unlock(&lock_r); + + tnode_r = container_of(rb_n, struct tree_node_ref, node); + + node_data = bpf_kptr_xchg(&tnode_r->node_data, NULL); + if (node_data) + bpf_obj_drop(node_data); + + bpf_obj_drop(tnode_r); + } + + return 0; +fail: + bpf_spin_unlock(&lock_r); + return ret; +} SEC("syscall") __failure __msg("R1 type=scalar expected=map_value, ptr_, ptr_") -- 2.50.1 (Apple Git-155)
