* [PATCH] crypto: x86/curve25519 - Remove unused carry variables
@ 2020-07-23 7:50 Herbert Xu
2020-07-23 10:05 ` Jason A. Donenfeld
0 siblings, 1 reply; 5+ messages in thread
From: Herbert Xu @ 2020-07-23 7:50 UTC (permalink / raw)
To: Linux Crypto Mailing List, Jason A. Donenfeld
The carry variables are assigned but never used, which upsets
the compiler. This patch removes them.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/arch/x86/crypto/curve25519-x86_64.c b/arch/x86/crypto/curve25519-x86_64.c
index 8a17621f7d3a..8acbb6584a37 100644
--- a/arch/x86/crypto/curve25519-x86_64.c
+++ b/arch/x86/crypto/curve25519-x86_64.c
@@ -948,10 +948,8 @@ static void store_felem(u64 *b, u64 *f)
{
u64 f30 = f[3U];
u64 top_bit0 = f30 >> (u32)63U;
- u64 carry0;
u64 f31;
u64 top_bit;
- u64 carry;
u64 f0;
u64 f1;
u64 f2;
@@ -970,11 +968,11 @@ static void store_felem(u64 *b, u64 *f)
u64 o2;
u64 o3;
f[3U] = f30 & (u64)0x7fffffffffffffffU;
- carry0 = add_scalar(f, f, (u64)19U * top_bit0);
+ add_scalar(f, f, (u64)19U * top_bit0);
f31 = f[3U];
top_bit = f31 >> (u32)63U;
f[3U] = f31 & (u64)0x7fffffffffffffffU;
- carry = add_scalar(f, f, (u64)19U * top_bit);
+ add_scalar(f, f, (u64)19U * top_bit);
f0 = f[0U];
f1 = f[1U];
f2 = f[2U];
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] crypto: x86/curve25519 - Remove unused carry variables
2020-07-23 7:50 [PATCH] crypto: x86/curve25519 - Remove unused carry variables Herbert Xu
@ 2020-07-23 10:05 ` Jason A. Donenfeld
2020-07-27 15:08 ` Karthik Bhargavan
0 siblings, 1 reply; 5+ messages in thread
From: Jason A. Donenfeld @ 2020-07-23 10:05 UTC (permalink / raw)
To: Herbert Xu; +Cc: Linux Crypto Mailing List, Karthik Bhargavan
Hi Herbert,
On Thu, Jul 23, 2020 at 9:51 AM Herbert Xu <herbert@gondor.apana.org.au> wrote:
>
> The carry variables are assigned but never used, which upsets
> the compiler. This patch removes them.
>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
>
> diff --git a/arch/x86/crypto/curve25519-x86_64.c b/arch/x86/crypto/curve25519-x86_64.c
> index 8a17621f7d3a..8acbb6584a37 100644
> --- a/arch/x86/crypto/curve25519-x86_64.c
> +++ b/arch/x86/crypto/curve25519-x86_64.c
> @@ -948,10 +948,8 @@ static void store_felem(u64 *b, u64 *f)
> {
> u64 f30 = f[3U];
> u64 top_bit0 = f30 >> (u32)63U;
> - u64 carry0;
> u64 f31;
> u64 top_bit;
> - u64 carry;
> u64 f0;
> u64 f1;
> u64 f2;
> @@ -970,11 +968,11 @@ static void store_felem(u64 *b, u64 *f)
> u64 o2;
> u64 o3;
> f[3U] = f30 & (u64)0x7fffffffffffffffU;
> - carry0 = add_scalar(f, f, (u64)19U * top_bit0);
> + add_scalar(f, f, (u64)19U * top_bit0);
> f31 = f[3U];
> top_bit = f31 >> (u32)63U;
> f[3U] = f31 & (u64)0x7fffffffffffffffU;
> - carry = add_scalar(f, f, (u64)19U * top_bit);
> + add_scalar(f, f, (u64)19U * top_bit);
> f0 = f[0U];
> f1 = f[1U];
> f2 = f[2U];
> --
That seems obvious and reasonable, and so I'm inclined to ack this,
but I first wanted to give Karthik (CC'd) a chance to chime in here,
as it's his HACL* project that's responsible, and he might have some
curious insight.
Jason
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] crypto: x86/curve25519 - Remove unused carry variables
2020-07-23 10:05 ` Jason A. Donenfeld
@ 2020-07-27 15:08 ` Karthik Bhargavan
2020-07-27 15:10 ` Karthik Bhargavan
2020-07-27 15:10 ` Jason A. Donenfeld
0 siblings, 2 replies; 5+ messages in thread
From: Karthik Bhargavan @ 2020-07-27 15:08 UTC (permalink / raw)
To: Jason A. Donenfeld; +Cc: Herbert Xu, Linux Crypto Mailing List
Removing unused variables is harmless. (GCC would do this automaticelly.)
So this change seems fine.
-Karthik
> On 23 Jul 2020, at 12:05, Jason A. Donenfeld <jason@zx2c4.com> wrote:
>
> Hi Herbert,
>
> On Thu, Jul 23, 2020 at 9:51 AM Herbert Xu <herbert@gondor.apana.org.au> wrote:
>>
>> The carry variables are assigned but never used, which upsets
>> the compiler. This patch removes them.
>>
>> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
>>
>> diff --git a/arch/x86/crypto/curve25519-x86_64.c b/arch/x86/crypto/curve25519-x86_64.c
>> index 8a17621f7d3a..8acbb6584a37 100644
>> --- a/arch/x86/crypto/curve25519-x86_64.c
>> +++ b/arch/x86/crypto/curve25519-x86_64.c
>> @@ -948,10 +948,8 @@ static void store_felem(u64 *b, u64 *f)
>> {
>> u64 f30 = f[3U];
>> u64 top_bit0 = f30 >> (u32)63U;
>> - u64 carry0;
>> u64 f31;
>> u64 top_bit;
>> - u64 carry;
>> u64 f0;
>> u64 f1;
>> u64 f2;
>> @@ -970,11 +968,11 @@ static void store_felem(u64 *b, u64 *f)
>> u64 o2;
>> u64 o3;
>> f[3U] = f30 & (u64)0x7fffffffffffffffU;
>> - carry0 = add_scalar(f, f, (u64)19U * top_bit0);
>> + add_scalar(f, f, (u64)19U * top_bit0);
>> f31 = f[3U];
>> top_bit = f31 >> (u32)63U;
>> f[3U] = f31 & (u64)0x7fffffffffffffffU;
>> - carry = add_scalar(f, f, (u64)19U * top_bit);
>> + add_scalar(f, f, (u64)19U * top_bit);
>> f0 = f[0U];
>> f1 = f[1U];
>> f2 = f[2U];
>> --
>
> That seems obvious and reasonable, and so I'm inclined to ack this,
> but I first wanted to give Karthik (CC'd) a chance to chime in here,
> as it's his HACL* project that's responsible, and he might have some
> curious insight.
>
> Jason
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] crypto: x86/curve25519 - Remove unused carry variables
2020-07-27 15:08 ` Karthik Bhargavan
@ 2020-07-27 15:10 ` Karthik Bhargavan
2020-07-27 15:10 ` Jason A. Donenfeld
1 sibling, 0 replies; 5+ messages in thread
From: Karthik Bhargavan @ 2020-07-27 15:10 UTC (permalink / raw)
To: Jason A. Donenfeld; +Cc: Herbert Xu, Linux Crypto Mailing List
Reviewed-by: Karthikeyan Bhargavan <karthik.bhargavan@gmail.com>
> On 27 Jul 2020, at 17:08, Karthik Bhargavan <karthikeyan.bhargavan@inria.fr> wrote:
>
> Removing unused variables is harmless. (GCC would do this automaticelly.)
> So this change seems fine.
>
> -Karthik
>
>> On 23 Jul 2020, at 12:05, Jason A. Donenfeld <jason@zx2c4.com> wrote:
>>
>> Hi Herbert,
>>
>> On Thu, Jul 23, 2020 at 9:51 AM Herbert Xu <herbert@gondor.apana.org.au> wrote:
>>>
>>> The carry variables are assigned but never used, which upsets
>>> the compiler. This patch removes them.
>>>
>>> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
>>>
>>> diff --git a/arch/x86/crypto/curve25519-x86_64.c b/arch/x86/crypto/curve25519-x86_64.c
>>> index 8a17621f7d3a..8acbb6584a37 100644
>>> --- a/arch/x86/crypto/curve25519-x86_64.c
>>> +++ b/arch/x86/crypto/curve25519-x86_64.c
>>> @@ -948,10 +948,8 @@ static void store_felem(u64 *b, u64 *f)
>>> {
>>> u64 f30 = f[3U];
>>> u64 top_bit0 = f30 >> (u32)63U;
>>> - u64 carry0;
>>> u64 f31;
>>> u64 top_bit;
>>> - u64 carry;
>>> u64 f0;
>>> u64 f1;
>>> u64 f2;
>>> @@ -970,11 +968,11 @@ static void store_felem(u64 *b, u64 *f)
>>> u64 o2;
>>> u64 o3;
>>> f[3U] = f30 & (u64)0x7fffffffffffffffU;
>>> - carry0 = add_scalar(f, f, (u64)19U * top_bit0);
>>> + add_scalar(f, f, (u64)19U * top_bit0);
>>> f31 = f[3U];
>>> top_bit = f31 >> (u32)63U;
>>> f[3U] = f31 & (u64)0x7fffffffffffffffU;
>>> - carry = add_scalar(f, f, (u64)19U * top_bit);
>>> + add_scalar(f, f, (u64)19U * top_bit);
>>> f0 = f[0U];
>>> f1 = f[1U];
>>> f2 = f[2U];
>>> --
>>
>> That seems obvious and reasonable, and so I'm inclined to ack this,
>> but I first wanted to give Karthik (CC'd) a chance to chime in here,
>> as it's his HACL* project that's responsible, and he might have some
>> curious insight.
>>
>> Jason
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] crypto: x86/curve25519 - Remove unused carry variables
2020-07-27 15:08 ` Karthik Bhargavan
2020-07-27 15:10 ` Karthik Bhargavan
@ 2020-07-27 15:10 ` Jason A. Donenfeld
1 sibling, 0 replies; 5+ messages in thread
From: Jason A. Donenfeld @ 2020-07-27 15:10 UTC (permalink / raw)
To: Karthik Bhargavan; +Cc: Herbert Xu, Linux Crypto Mailing List
On Mon, Jul 27, 2020 at 5:08 PM Karthik Bhargavan
<karthikeyan.bhargavan@inria.fr> wrote:
>
> Removing unused variables is harmless. (GCC would do this automaticelly.)
> So this change seems fine.
Thanks for confirming. Hopefully we can get that change upstream in
HACL* too, so that the code comes out the same.
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
^ permalink raw reply [flat|nested] 5+ messages in thread
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2020-07-23 7:50 [PATCH] crypto: x86/curve25519 - Remove unused carry variables Herbert Xu
2020-07-23 10:05 ` Jason A. Donenfeld
2020-07-27 15:08 ` Karthik Bhargavan
2020-07-27 15:10 ` Karthik Bhargavan
2020-07-27 15:10 ` Jason A. Donenfeld
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