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crypto: arm64/gcm - remove Wunused-const-variable ghash_cpu_feature

PATCH In review Austin Kim 2 participants 3 messages May 27, 2021 – May 28, 2021

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Crypto API arm64 Security (LSM)
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Austin Kim

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#0 lore raw

PATCH 1/1 crypto: arm64/gcm - remove Wunused-const-variable ghash_cpu_feature

GCC compiler complains with below messages.

warning: ‘ghash_cpu_feature’ defined but not used [-Wunused-const-variable=]

   static const struct cpu_feature ghash_cpu_feature[] = {
			    ^~~~~~~~~~~~~~~~~

The variable with MODULE_DEVICE_TABLE() is registered as platform_driver. But ghash_cpu_feature is not used, so remove ghash_cpu_feature.

Signed-off-by Austin Kim <[email protected]>
---
 arch/arm64/crypto/ghash-ce-glue.c | 5 -----
 1 file changed, 5 deletions(-)
arch/arm64/crypto/ghash-ce-glue.c +0 -5
index 720cd3a58da3..c3f27d0d5329 100644
@@ -615,10 +615,5 @@ static void __exit ghash_ce_mod_exit(void)
 		crypto_unregister_shash(&ghash_alg);
 }
 
-static const struct cpu_feature ghash_cpu_feature[] = {
-	{ cpu_feature(PMULL) }, { }
-};
-MODULE_DEVICE_TABLE(cpu, ghash_cpu_feature);
-
 module_init(ghash_ce_mod_init);
 module_exit(ghash_ce_mod_exit);
Signature · 1 line
2.20.1
#1 lore raw
Quoted 2 lines · Austin Kim

The variable with MODULE_DEVICE_TABLE() is registered as platform_driver.

What does this mean? There is no platform_driver involved here at all.

Quoted 1 line

But ghash_cpu_feature is not used, so remove ghash_cpu_feature.

It is used when the file is built as a module.

arch/arm64/crypto/ghash-ce-glue.c static void __exit ghash_ce_mod_exit(void) · line 622

Quoted 13 lines
arch/arm64/crypto/ghash-ce-glue.c +0 -5
index 720cd3a58da3..c3f27d0d5329 100644
@@ -615,10 +615,5 @@ static void __exit ghash_ce_mod_exit(void)
 		crypto_unregister_shash(&ghash_alg);
 }
 
-static const struct cpu_feature ghash_cpu_feature[] = {
-	{ cpu_feature(PMULL) }, { }
-};
-MODULE_DEVICE_TABLE(cpu, ghash_cpu_feature);
-

Probably adding __maybe_unused to ghash_cpu_feature[] is the right thing to do. That's what module_cpu_feature_match() does.

(Note that module_cpu_feature_match() can't be used here, as it seems the intent is for this module to be autoloaded when PMULL is detected, but still be loadable without it. So, that's apparently the reason for using MODULE_DEVICE_TABLE() directly.)

- Eric

author
#2 lore raw

2021년 5월 28일 (금) 오전 2:46, Eric Biggers <[email protected]>님이 작성:

Quoted 7 lines · Austin Kim
Quoted 2 lines

The variable with MODULE_DEVICE_TABLE() is registered as platform_driver.

What does this mean? There is no platform_driver involved here at all.

What I would like to say is "in many cases, MODULE_DEVICE_TABLE is registered as struct of platform_driver"
ex) [drivers/char/hw_random/meson-rng.c] MODULE_DEVICE_TABLE(of, meson_rng_of_match);

static struct platform_driver meson_rng_driver = { .probe = meson_rng_probe,
.driver = {
.name = "meson-rng",
.of_match_table = meson_rng_of_match,
},
};

Quoted 4 lines
Quoted 1 line

But ghash_cpu_feature is not used, so remove ghash_cpu_feature.

It is used when the file is built as a module.

Thanks for the information. But it looks like this file is compiled as built-in with 'CONFIG_CRYPTO_GHASH_ARM64_CE=y' by default.

Quoted 11 lines

arch/arm64/crypto/ghash-ce-glue.c

Quoted 3 lines
arch/arm64/crypto/ghash-ce-glue.c +0 -0
index 720cd3a58da3..c3f27d0d5329 100644
[...]

Probably adding __maybe_unused to ghash_cpu_feature[] is the right thing to do. That's what module_cpu_feature_match() does.

(Note that module_cpu_feature_match() can't be used here, as it seems the intent is for this module to be autoloaded when PMULL is detected, but still be loadable without it. So, that's apparently the reason for using MODULE_DEVICE_TABLE() directly.)

Thanks for the valuable idea and feedback.

Quoted 2 lines

- Eric