Add three new kfuncs for the bits iterator:
- bpf_iter_bits_new
Initialize a new bits iterator for a given memory area. Due to the
limitation of bpf memalloc, the max number of bits that can be iterated
over is limited to (4096 * 8).
- bpf_iter_bits_next
Get the next bit in a bpf_iter_bits
- bpf_iter_bits_destroy
Destroy a bpf_iter_bits
The bits iterator facilitates the iteration of the bits of a memory area,
such as cpumask. It can be used in any context and on any address.
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
kernel/bpf/helpers.c | 120 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 120 insertions(+)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 8cde717137bd..421e42663736 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2549,6 +2549,123 @@ __bpf_kfunc void bpf_throw(u64 cookie)
WARN(1, "A call to BPF exception callback should never return\n");
}
+struct bpf_iter_bits {
+ __u64 __opaque[2];
+} __aligned(8);
+
+struct bpf_iter_bits_kern {
+ union {
+ unsigned long *bits;
+ unsigned long bits_copy;
+ };
+ u32 nr_bits;
+ int bit;
+} __aligned(8);
+
+/**
+ * bpf_iter_bits_new() - Initialize a new bits iterator for a given memory area
+ * @it: The new bpf_iter_bits to be created
+ * @unsafe_ptr__ign: A ponter pointing to a memory area to be iterated over
+ * @nr_bits: The number of bits to be iterated over. Due to the limitation of
+ * memalloc, it can't greater than (4096 * 8).
+ *
+ * This function initializes a new bpf_iter_bits structure for iterating over
+ * a memory area which is specified by the @unsafe_ptr__ign and @nr_bits. It
+ * copy the data of the memory area to the newly created bpf_iter_bits @it for
+ * subsequent iteration operations.
+ *
+ * On success, 0 is returned. On failure, ERR is returned.
+ */
+__bpf_kfunc int
+bpf_iter_bits_new(struct bpf_iter_bits *it, const void *unsafe_ptr__ign, u32 nr_bits)
+{
+ u32 size = BITS_TO_LONGS(nr_bits) * sizeof(unsigned long);
+ struct bpf_iter_bits_kern *kit = (void *)it;
+ int err;
+
+ BUILD_BUG_ON(sizeof(struct bpf_iter_bits_kern) != sizeof(struct bpf_iter_bits));
+ BUILD_BUG_ON(__alignof__(struct bpf_iter_bits_kern) !=
+ __alignof__(struct bpf_iter_bits));
+
+ if (!unsafe_ptr__ign || !nr_bits) {
+ kit->bits = NULL;
+ return -EINVAL;
+ }
+
+ kit->nr_bits = 0;
+ kit->bits_copy = 0;
+ /* Optimization for u64/u32 mask */
+ if (nr_bits <= 64) {
+ err = bpf_probe_read_kernel_common(&kit->bits_copy, size, unsafe_ptr__ign);
+ if (err)
+ return -EFAULT;
+
+ kit->nr_bits = nr_bits;
+ kit->bit = -1;
+ return 0;
+ }
+
+ /* Fallback to memalloc */
+ kit->bits = bpf_mem_alloc(&bpf_global_ma, size);
+ if (!kit->bits)
+ return -ENOMEM;
+
+ err = bpf_probe_read_kernel_common(kit->bits, size, unsafe_ptr__ign);
+ if (err) {
+ bpf_mem_free(&bpf_global_ma, kit->bits);
+ return err;
+ }
+
+ kit->nr_bits = nr_bits;
+ kit->bit = -1;
+ return 0;
+}
+
+/**
+ * bpf_iter_bits_next() - Get the next bit in a bpf_iter_bits
+ * @it: The bpf_iter_bits to be checked
+ *
+ * This function returns a pointer to a number representing the value of the
+ * next bit in the bits.
+ *
+ * If there are no further bit available, it returns NULL.
+ */
+__bpf_kfunc int *bpf_iter_bits_next(struct bpf_iter_bits *it)
+{
+ struct bpf_iter_bits_kern *kit = (void *)it;
+ u32 nr_bits = kit->nr_bits;
+ const unsigned long *bits;
+ int bit;
+
+ if (nr_bits == 0)
+ return NULL;
+
+ bits = nr_bits <= 64 ? &kit->bits_copy : kit->bits;
+ bit = find_next_bit(bits, nr_bits, kit->bit + 1);
+ if (bit >= nr_bits) {
+ kit->nr_bits = 0;
+ return NULL;
+ }
+
+ kit->bit = bit;
+ return &kit->bit;
+}
+
+/**
+ * bpf_iter_bits_destroy() - Destroy a bpf_iter_bits
+ * @it: The bpf_iter_bits to be destroyed
+ *
+ * Destroy the resource associated with the bpf_iter_bits.
+ */
+__bpf_kfunc void bpf_iter_bits_destroy(struct bpf_iter_bits *it)
+{
+ struct bpf_iter_bits_kern *kit = (void *)it;
+
+ if (kit->nr_bits <= 64)
+ return;
+ bpf_mem_free(&bpf_global_ma, kit->bits);
+}
+
__bpf_kfunc_end_defs();
BTF_KFUNCS_START(generic_btf_ids)
@@ -2626,6 +2743,9 @@ BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
BTF_ID_FLAGS(func, bpf_dynptr_size)
BTF_ID_FLAGS(func, bpf_dynptr_clone)
BTF_ID_FLAGS(func, bpf_modify_return_test_tp)
+BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW)
+BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)
BTF_KFUNCS_END(common_btf_ids)
static const struct btf_kfunc_id_set common_kfunc_set = {
--
2.39.1
