linux-kernel - Re: [PATCH v3 4/5] powerpc/vdso: Wire up getrandom() vDSO implementation on PPC32

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Message-ID: <b33384e2-088d-4116-81d5-ae895a761c19@csgroup.eu>
Date: Fri, 30 Aug 2024 19:23:18 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 Naveen N Rao <naveen@...nel.org>, Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling
 <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, linux-kselftest@...r.kernel.org,
 llvm@...ts.linux.dev, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
 linux-trace-kernel@...r.kernel.org,
 Adhemerval Zanella <adhemerval.zanella@...aro.org>,
 Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH v3 4/5] powerpc/vdso: Wire up getrandom() vDSO
 implementation on PPC32

Le 30/08/2024 à 18:42, Christophe Leroy a écrit :
> 
> 
> Le 30/08/2024 à 18:14, Jason A. Donenfeld a écrit :
>> On Fri, Aug 30, 2024 at 05:57:08PM +0200, Christophe Leroy wrote:
>>> + *    r5: 8-byte counter input/output (saved on stack)
>>> + *
>>> + *    r14-r15: counter
>>> + */
>>> +SYM_FUNC_START(__arch_chacha20_blocks_nostack)
>>> +    stwu    r1, -96(r1)
>>> +    stw    r5, 20(r1)
>>> +    stmw    r14, 24(r1)
>>> +    li    r31, 4
>>> +    LWZX_LE    r14, 0, r5
>>> +    LWZX_LE    r15, r31, r5
>>
>> Why swap endian on the counter?
> 
> Unlike the keys, the counter is passed to the function as an u8*, not as 
> a u64*, so I thought it was raw data in little endian order, same as 
> when using Sodium. Is it wrong ?

Hum ..... I looked again and it seems it is already a u32 *. Looks like 
I mis-read the 8-byte comment. Or I did it right in the begining then I 
swapped it at the same time as I swapped the keys after my first test 
when the selftest was using Sodium. I can't remember. I'll fix it.

Christophe