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, 218 insertions, 0 deletions

diff --git a/include/crypto/internal/cipher.h b/include/crypto/internal/cipher.h
new file mode 100644
index 000000000..a9174ba90
--- /dev/null
+++ b/include/crypto/internal/cipher.h
@@ -0,0 +1,218 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
+ * Copyright (c) 2002 David S. Miller (davem@redhat.com)
+ * Copyright (c) 2005 Herbert Xu <herbert@gondor.apana.org.au>
+ *
+ * Portions derived from Cryptoapi, by Alexander Kjeldaas <astor@fast.no>
+ * and Nettle, by Niels Möller.
+ */
+
+#ifndef _CRYPTO_INTERNAL_CIPHER_H
+#define _CRYPTO_INTERNAL_CIPHER_H
+
+#include <crypto/algapi.h>
+
+struct crypto_cipher {
+	struct crypto_tfm base;
+};
+
+/**
+ * DOC: Single Block Cipher API
+ *
+ * The single block cipher API is used with the ciphers of type
+ * CRYPTO_ALG_TYPE_CIPHER (listed as type "cipher" in /proc/crypto).
+ *
+ * Using the single block cipher API calls, operations with the basic cipher
+ * primitive can be implemented. These cipher primitives exclude any block
+ * chaining operations including IV handling.
+ *
+ * The purpose of this single block cipher API is to support the implementation
+ * of templates or other concepts that only need to perform the cipher operation
+ * on one block at a time. Templates invoke the underlying cipher primitive
+ * block-wise and process either the input or the output data of these cipher
+ * operations.
+ */
+
+static inline struct crypto_cipher *__crypto_cipher_cast(struct crypto_tfm *tfm)
+{
+	return (struct crypto_cipher *)tfm;
+}
+
+/**
+ * crypto_alloc_cipher() - allocate single block cipher handle
+ * @alg_name: is the cra_name / name or cra_driver_name / driver name of the
+ *	     single block cipher
+ * @type: specifies the type of the cipher
+ * @mask: specifies the mask for the cipher
+ *
+ * Allocate a cipher handle for a single block cipher. The returned struct
+ * crypto_cipher is the cipher handle that is required for any subsequent API
+ * invocation for that single block cipher.
+ *
+ * Return: allocated cipher handle in case of success; IS_ERR() is true in case
+ *	   of an error, PTR_ERR() returns the error code.
+ */
+static inline struct crypto_cipher *crypto_alloc_cipher(const char *alg_name,
+							u32 type, u32 mask)
+{
+	type &= ~CRYPTO_ALG_TYPE_MASK;
+	type |= CRYPTO_ALG_TYPE_CIPHER;
+	mask |= CRYPTO_ALG_TYPE_MASK;
+
+	return __crypto_cipher_cast(crypto_alloc_base(alg_name, type, mask));
+}
+
+static inline struct crypto_tfm *crypto_cipher_tfm(struct crypto_cipher *tfm)
+{
+	return &tfm->base;
+}
+
+/**
+ * crypto_free_cipher() - zeroize and free the single block cipher handle
+ * @tfm: cipher handle to be freed
+ */
+static inline void crypto_free_cipher(struct crypto_cipher *tfm)
+{
+	crypto_free_tfm(crypto_cipher_tfm(tfm));
+}
+
+/**
+ * crypto_has_cipher() - Search for the availability of a single block cipher
+ * @alg_name: is the cra_name / name or cra_driver_name / driver name of the
+ *	     single block cipher
+ * @type: specifies the type of the cipher
+ * @mask: specifies the mask for the cipher
+ *
+ * Return: true when the single block cipher is known to the kernel crypto API;
+ *	   false otherwise
+ */
+static inline int crypto_has_cipher(const char *alg_name, u32 type, u32 mask)
+{
+	type &= ~CRYPTO_ALG_TYPE_MASK;
+	type |= CRYPTO_ALG_TYPE_CIPHER;
+	mask |= CRYPTO_ALG_TYPE_MASK;
+
+	return crypto_has_alg(alg_name, type, mask);
+}
+
+/**
+ * crypto_cipher_blocksize() - obtain block size for cipher
+ * @tfm: cipher handle
+ *
+ * The block size for the single block cipher referenced with the cipher handle
+ * tfm is returned. The caller may use that information to allocate appropriate
+ * memory for the data returned by the encryption or decryption operation
+ *
+ * Return: block size of cipher
+ */
+static inline unsigned int crypto_cipher_blocksize(struct crypto_cipher *tfm)
+{
+	return crypto_tfm_alg_blocksize(crypto_cipher_tfm(tfm));
+}
+
+static inline unsigned int crypto_cipher_alignmask(struct crypto_cipher *tfm)
+{
+	return crypto_tfm_alg_alignmask(crypto_cipher_tfm(tfm));
+}
+
+static inline u32 crypto_cipher_get_flags(struct crypto_cipher *tfm)
+{
+	return crypto_tfm_get_flags(crypto_cipher_tfm(tfm));
+}
+
+static inline void crypto_cipher_set_flags(struct crypto_cipher *tfm,
+					   u32 flags)
+{
+	crypto_tfm_set_flags(crypto_cipher_tfm(tfm), flags);
+}
+
+static inline void crypto_cipher_clear_flags(struct crypto_cipher *tfm,
+					     u32 flags)
+{
+	crypto_tfm_clear_flags(crypto_cipher_tfm(tfm), flags);
+}
+
+/**
+ * crypto_cipher_setkey() - set key for cipher
+ * @tfm: cipher handle
+ * @key: buffer holding the key
+ * @keylen: length of the key in bytes
+ *
+ * The caller provided key is set for the single block cipher referenced by the
+ * cipher handle.
+ *
+ * Note, the key length determines the cipher type. Many block ciphers implement
+ * different cipher modes depending on the key size, such as AES-128 vs AES-192
+ * vs. AES-256. When providing a 16 byte key for an AES cipher handle, AES-128
+ * is performed.
+ *
+ * Return: 0 if the setting of the key was successful; < 0 if an error occurred
+ */
+int crypto_cipher_setkey(struct crypto_cipher *tfm,
+			 const u8 *key, unsigned int keylen);
+
+/**
+ * crypto_cipher_encrypt_one() - encrypt one block of plaintext
+ * @tfm: cipher handle
+ * @dst: points to the buffer that will be filled with the ciphertext
+ * @src: buffer holding the plaintext to be encrypted
+ *
+ * Invoke the encryption operation of one block. The caller must ensure that
+ * the plaintext and ciphertext buffers are at least one block in size.
+ */
+void crypto_cipher_encrypt_one(struct crypto_cipher *tfm,
+			       u8 *dst, const u8 *src);
+
+/**
+ * crypto_cipher_decrypt_one() - decrypt one block of ciphertext
+ * @tfm: cipher handle
+ * @dst: points to the buffer that will be filled with the plaintext
+ * @src: buffer holding the ciphertext to be decrypted
+ *
+ * Invoke the decryption operation of one block. The caller must ensure that
+ * the plaintext and ciphertext buffers are at least one block in size.
+ */
+void crypto_cipher_decrypt_one(struct crypto_cipher *tfm,
+			       u8 *dst, const u8 *src);
+
+struct crypto_cipher_spawn {
+	struct crypto_spawn base;
+};
+
+static inline int crypto_grab_cipher(struct crypto_cipher_spawn *spawn,
+				     struct crypto_instance *inst,
+				     const char *name, u32 type, u32 mask)
+{
+	type &= ~CRYPTO_ALG_TYPE_MASK;
+	type |= CRYPTO_ALG_TYPE_CIPHER;
+	mask |= CRYPTO_ALG_TYPE_MASK;
+	return crypto_grab_spawn(&spawn->base, inst, name, type, mask);
+}
+
+static inline void crypto_drop_cipher(struct crypto_cipher_spawn *spawn)
+{
+	crypto_drop_spawn(&spawn->base);
+}
+
+static inline struct crypto_alg *crypto_spawn_cipher_alg(
+       struct crypto_cipher_spawn *spawn)
+{
+	return spawn->base.alg;
+}
+
+static inline struct crypto_cipher *crypto_spawn_cipher(
+	struct crypto_cipher_spawn *spawn)
+{
+	u32 type = CRYPTO_ALG_TYPE_CIPHER;
+	u32 mask = CRYPTO_ALG_TYPE_MASK;
+
+	return __crypto_cipher_cast(crypto_spawn_tfm(&spawn->base, type, mask));
+}
+
+static inline struct cipher_alg *crypto_cipher_alg(struct crypto_cipher *tfm)
+{
+	return &crypto_cipher_tfm(tfm)->__crt_alg->cra_cipher;
+}
+
+#endif