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Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * AES block cipher using AES-NI instructions
4 *
5 * Copyright 2026 Google LLC
6 */
7
8#include <asm/fpu/api.h>
9
10static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_aes);
11
12void aes128_expandkey_aesni(u32 rndkeys[], u32 *inv_rndkeys,
13 const u8 in_key[AES_KEYSIZE_128]);
14void aes256_expandkey_aesni(u32 rndkeys[], u32 *inv_rndkeys,
15 const u8 in_key[AES_KEYSIZE_256]);
16void aes_encrypt_aesni(const u32 rndkeys[], int nrounds,
17 u8 out[AES_BLOCK_SIZE], const u8 in[AES_BLOCK_SIZE]);
18void aes_decrypt_aesni(const u32 inv_rndkeys[], int nrounds,
19 u8 out[AES_BLOCK_SIZE], const u8 in[AES_BLOCK_SIZE]);
20
21/*
22 * Expand an AES key using AES-NI if supported and usable or generic code
23 * otherwise. The expanded key format is compatible between the two cases. The
24 * outputs are @k->rndkeys (required) and @inv_k->inv_rndkeys (optional).
25 *
26 * We could just always use the generic key expansion code. AES key expansion
27 * is usually less performance-critical than AES en/decryption. However,
28 * there's still *some* value in speed here, as well as in non-key-dependent
29 * execution time which AES-NI provides. So, do use AES-NI to expand AES-128
30 * and AES-256 keys. (Don't bother with AES-192, as it's almost never used.)
31 */
32static void aes_preparekey_arch(union aes_enckey_arch *k,
33 union aes_invkey_arch *inv_k,
34 const u8 *in_key, int key_len, int nrounds)
35{
36 u32 *rndkeys = k->rndkeys;
37 u32 *inv_rndkeys = inv_k ? inv_k->inv_rndkeys : NULL;
38
39 if (static_branch_likely(&have_aes) && key_len != AES_KEYSIZE_192 &&
40 irq_fpu_usable()) {
41 kernel_fpu_begin();
42 if (key_len == AES_KEYSIZE_128)
43 aes128_expandkey_aesni(rndkeys, inv_rndkeys, in_key);
44 else
45 aes256_expandkey_aesni(rndkeys, inv_rndkeys, in_key);
46 kernel_fpu_end();
47 } else {
48 aes_expandkey_generic(rndkeys, inv_rndkeys, in_key, key_len);
49 }
50}
51
52static void aes_encrypt_arch(const struct aes_enckey *key,
53 u8 out[AES_BLOCK_SIZE],
54 const u8 in[AES_BLOCK_SIZE])
55{
56 if (static_branch_likely(&have_aes) && irq_fpu_usable()) {
57 kernel_fpu_begin();
58 aes_encrypt_aesni(key->k.rndkeys, key->nrounds, out, in);
59 kernel_fpu_end();
60 } else {
61 aes_encrypt_generic(key->k.rndkeys, key->nrounds, out, in);
62 }
63}
64
65static void aes_decrypt_arch(const struct aes_key *key,
66 u8 out[AES_BLOCK_SIZE],
67 const u8 in[AES_BLOCK_SIZE])
68{
69 if (static_branch_likely(&have_aes) && irq_fpu_usable()) {
70 kernel_fpu_begin();
71 aes_decrypt_aesni(key->inv_k.inv_rndkeys, key->nrounds,
72 out, in);
73 kernel_fpu_end();
74 } else {
75 aes_decrypt_generic(key->inv_k.inv_rndkeys, key->nrounds,
76 out, in);
77 }
78}
79
80#define aes_mod_init_arch aes_mod_init_arch
81static void aes_mod_init_arch(void)
82{
83 if (boot_cpu_has(X86_FEATURE_AES))
84 static_branch_enable(&have_aes);
85}