sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/include/crypto/des.h b/include/crypto/des.h
new file mode 100644
index 000000000..73eec617f
--- /dev/null
+++ b/include/crypto/des.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* 
+ * DES & Triple DES EDE Cipher Algorithms.
+ */
+
+#ifndef __CRYPTO_DES_H
+#define __CRYPTO_DES_H
+
+#include <linux/types.h>
+
+#define DES_KEY_SIZE		8
+#define DES_EXPKEY_WORDS	32
+#define DES_BLOCK_SIZE		8
+
+#define DES3_EDE_KEY_SIZE	(3 * DES_KEY_SIZE)
+#define DES3_EDE_EXPKEY_WORDS	(3 * DES_EXPKEY_WORDS)
+#define DES3_EDE_BLOCK_SIZE	DES_BLOCK_SIZE
+
+struct des_ctx {
+	u32 expkey[DES_EXPKEY_WORDS];
+};
+
+struct des3_ede_ctx {
+	u32 expkey[DES3_EDE_EXPKEY_WORDS];
+};
+
+void des_encrypt(const struct des_ctx *ctx, u8 *dst, const u8 *src);
+void des_decrypt(const struct des_ctx *ctx, u8 *dst, const u8 *src);
+
+void des3_ede_encrypt(const struct des3_ede_ctx *dctx, u8 *dst, const u8 *src);
+void des3_ede_decrypt(const struct des3_ede_ctx *dctx, u8 *dst, const u8 *src);
+
+/**
+ * des_expand_key - Expand a DES input key into a key schedule
+ * @ctx: the key schedule
+ * @key: buffer containing the input key
+ * @keylen: size of the buffer contents
+ *
+ * Returns: 0 on success, -EINVAL if the input key is rejected and -ENOKEY if
+ * the key is accepted but has been found to be weak.
+ */
+int des_expand_key(struct des_ctx *ctx, const u8 *key, unsigned int keylen);
+
+/**
+ * des3_ede_expand_key - Expand a triple DES input key into a key schedule
+ * @ctx: the key schedule
+ * @key: buffer containing the input key
+ * @keylen: size of the buffer contents
+ *
+ * Returns: 0 on success, -EINVAL if the input key is rejected and -ENOKEY if
+ * the key is accepted but has been found to be weak. Note that weak keys will
+ * be rejected (and -EINVAL will be returned) when running in FIPS mode.
+ */
+int des3_ede_expand_key(struct des3_ede_ctx *ctx, const u8 *key,
+			unsigned int keylen);
+
+#endif /* __CRYPTO_DES_H */