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Assign crypto aliases to different AES implementation modules

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The kernel modules aes-neon-blk and aes-neon-bs perform poorly, at least on
Cortex-A72 without crypto extensions. In fact, aes-arm64 outperforms them
on benchmarks, despite it being a simpler implementation (only accelerating
the single-block AES cipher).

For modes of operation where multiple cipher blocks can be processed in
parallel, aes-neon-bs outperforms aes-neon-blk by around 60-70% and aes-arm64
is another 10-20% faster still. But the difference is even more marked with
modes of operation with dependencies between neighbouring blocks, such as
CBC encryption, which defeat parallelism: in these cases, aes-arm64 is
typically around 250% faster than either aes-neon-blk or aes-neon-bs.

The key trade-off with aes-arm64 is that the look-up tables are situated in
RAM. This leaves them potentially open to cache timing attacks. The two other
modules, by contrast, load the look-up tables into NEON registers and so are
able to perform in constant time.

This patch aims to load aes-arm64 more often.

If none of the currently-loaded crypto modules implement a given algorithm,
a new one is typically selected for loading using a platform-neutral alias
describing the required algorithm. To enable users to still
load aes-neon-blk or aes-neon-bs if they really want them, while still
ensuring that aes-arm64 is usually selected, remove the aliases from
aes-neonbs-glue.c and aes-glue.c and apply them to aes-cipher-glue.c, but
still build the two NEON modules.

Since aes-glue.c can also be used to build aes-ce-blk, leave them enabled
if USE_V8_CRYPTO_EXTENSIONS is defined, to ensure they are selected if we
in future use a CPU which has the crypto extensions enabled.

Note that the algorithm priority specifiers are unchanged, so if
aes-neon-bs is loaded at the same time as aes-arm64, the former will be
used in preference. However, aes-neon-blk and aes-arm64 have tied priority,
so whichever module was loaded first will be used (assuming aes-neon-bs is
not loaded).

Signed-off-by: Ben Avison <bavison@riscosopen.org>
This commit is contained in:
Ben Avison
2021-03-08 15:32:25 +00:00
committed by Dom Cobley
parent 933357eeca
commit 1ccd66f926
3 changed files with 13 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
arch/arm64/crypto/aes-cipher-glue.c
View File

@@ -9,6 +9,17 @@
#include <crypto/algapi.h>
#include <linux/module.h>
MODULE_ALIAS_CRYPTO("ecb(aes)");
MODULE_ALIAS_CRYPTO("cbc(aes)");
MODULE_ALIAS_CRYPTO("ctr(aes)");
MODULE_ALIAS_CRYPTO("xts(aes)");
MODULE_ALIAS_CRYPTO("xctr(aes)");
MODULE_ALIAS_CRYPTO("cts(cbc(aes))");
MODULE_ALIAS_CRYPTO("essiv(cbc(aes),sha256)");
MODULE_ALIAS_CRYPTO("cmac(aes)");
MODULE_ALIAS_CRYPTO("xcbc(aes)");
MODULE_ALIAS_CRYPTO("cbcmac(aes)");
asmlinkage void __aes_arm64_encrypt(u32 *rk, u8 *out, const u8 *in, int rounds);
asmlinkage void __aes_arm64_decrypt(u32 *rk, u8 *out, const u8 *in, int rounds);

4
arch/arm64/crypto/aes-glue.c
View File

@@ -58,18 +58,18 @@ MODULE_DESCRIPTION("AES-ECB/CBC/CTR/XTS/XCTR using ARMv8 Crypto Extensions");
#define aes_mac_update neon_aes_mac_update
MODULE_DESCRIPTION("AES-ECB/CBC/CTR/XTS/XCTR using ARMv8 NEON");
#endif
#if defined(USE_V8_CRYPTO_EXTENSIONS) || !IS_ENABLED(CONFIG_CRYPTO_AES_ARM64_BS)
#if defined(USE_V8_CRYPTO_EXTENSIONS)
MODULE_ALIAS_CRYPTO("ecb(aes)");
MODULE_ALIAS_CRYPTO("cbc(aes)");
MODULE_ALIAS_CRYPTO("ctr(aes)");
MODULE_ALIAS_CRYPTO("xts(aes)");
MODULE_ALIAS_CRYPTO("xctr(aes)");
#endif
MODULE_ALIAS_CRYPTO("cts(cbc(aes))");
MODULE_ALIAS_CRYPTO("essiv(cbc(aes),sha256)");
MODULE_ALIAS_CRYPTO("cmac(aes)");
MODULE_ALIAS_CRYPTO("xcbc(aes)");
MODULE_ALIAS_CRYPTO("cbcmac(aes)");
#endif
MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
MODULE_LICENSE("GPL v2");

5
arch/arm64/crypto/aes-neonbs-glue.c
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@@ -19,11 +19,6 @@ MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
MODULE_DESCRIPTION("Bit sliced AES using NEON instructions");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS_CRYPTO("ecb(aes)");
MODULE_ALIAS_CRYPTO("cbc(aes)");
MODULE_ALIAS_CRYPTO("ctr(aes)");
MODULE_ALIAS_CRYPTO("xts(aes)");
asmlinkage void aesbs_convert_key(u8 out[], u32 const rk[], int rounds);
asmlinkage void aesbs_ecb_encrypt(u8 out[], u8 const in[], u8 const rk[],