linux-kernel - Re: [PATCH] aarch64: vdso: Wire up getrandom() vDSO implementation

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Message-ID: <fd3cd385-131a-43b2-8ce9-05547a4f2d1d@linaro.org>
Date: Tue, 27 Aug 2024 10:17:18 -0300
From: Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: Theodore Ts'o <tytso@....edu>, linux-kernel@...r.kernel.org,
 linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-arch@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>,
 Will Deacon <will@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
 Eric Biggers <ebiggers@...nel.org>,
 Christophe Leroy <christophe.leroy@...roup.eu>
Subject: Re: [PATCH] aarch64: vdso: Wire up getrandom() vDSO implementation



On 26/08/24 17:27, Jason A. Donenfeld wrote:
> Hi Adhemerval,
> 
> Thanks for posting this! Exciting to have it here.
> 
> Just some small nits for now:
> 
> On Mon, Aug 26, 2024 at 06:10:40PM +0000, Adhemerval Zanella wrote:
>> +static __always_inline ssize_t getrandom_syscall(void *buffer, size_t len, unsigned int flags)
>> +{
>> +	register long int x8 asm ("x8") = __NR_getrandom;
>> +	register long int x0 asm ("x0") = (long int) buffer;
>> +	register long int x1 asm ("x1") = (long int) len;
>> +	register long int x2 asm ("x2") = (long int) flags;
> 
> Usually it's written just as `long` or `unsigned long`, and likewise
> with the cast. Also, no space after the cast.

Ack.

> 
>> +#define __VDSO_RND_DATA_OFFSET  480
> 
> This is the size of the data currently there?

Yes, I used the same strategy x86 did.

> 
>>  #include <asm/page.h>
>>  #include <asm/vdso.h>
>>  #include <asm-generic/vmlinux.lds.h>
>> +#include <vdso/datapage.h>
>> +#include <asm/vdso/vsyscall.h>
> 
> Possible to keep the asm/ together?

Ack.

> 
>> + * ARM64 ChaCha20 implementation meant for vDSO.  Produces a given positive
>> + * number of blocks of output with nonnce 0, taking an input key and 8-bytes
> 
> nonnce -> nonce

Ack.

> 
>> -ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/)
>> +ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/ -e s/aarch64.*/arm64/)
>>  SODIUM := $(shell pkg-config --libs libsodium 2>/dev/null)
>>  
>>  TEST_GEN_PROGS := vdso_test_gettimeofday
>> @@ -11,7 +11,7 @@ ifeq ($(ARCH),$(filter $(ARCH),x86 x86_64))
>>  TEST_GEN_PROGS += vdso_standalone_test_x86
>>  endif
>>  TEST_GEN_PROGS += vdso_test_correctness
>> -ifeq ($(uname_M),x86_64)
>> +ifeq ($(uname_M), $(filter x86_64 aarch64, $(uname_M)))
>>  TEST_GEN_PROGS += vdso_test_getrandom
>>  ifneq ($(SODIUM),)
>>  TEST_GEN_PROGS += vdso_test_chacha
> 
> You'll need to add the symlink to get the chacha selftest running:
> 
>   $ ln -s ../../../arch/arm64/kernel/vdso tools/arch/arm64/vdso
>   $ git add tools/arch/arm64/vdso
> 
> Also, can you confirm that the chacha selftest runs and works?

Yes, last time I has to built it manually since the Makefile machinery seem 
to be broken even on x86_64.  In a Ubuntu vm I have:

tools/testing/selftests/vDSO$ make
  CC       vdso_test_gettimeofday
  CC       vdso_test_getcpu
  CC       vdso_test_abi
  CC       vdso_test_clock_getres
  CC       vdso_standalone_test_x86
  CC       vdso_test_correctness
  CC       vdso_test_getrandom
  CC       vdso_test_chacha
In file included from /home/azanella/Projects/linux/linux-git/include/linux/limits.h:7,
                 from /usr/include/x86_64-linux-gnu/bits/local_lim.h:38,
                 from /usr/include/x86_64-linux-gnu/bits/posix1_lim.h:161,
                 from /usr/include/limits.h:195,
                 from /usr/lib/gcc/x86_64-linux-gnu/13/include/limits.h:205,
                 from /usr/lib/gcc/x86_64-linux-gnu/13/include/syslimits.h:7,
                 from /usr/lib/gcc/x86_64-linux-gnu/13/include/limits.h:34,
                 from /usr/include/sodium/export.h:7,
                 from /usr/include/sodium/crypto_stream_chacha20.h:14,
                 from vdso_test_chacha.c:6:
/usr/include/x86_64-linux-gnu/bits/xopen_lim.h:99:6: error: missing binary operator before token "("
   99 | # if INT_MAX == 32767
      |      ^~~~~~~
/usr/include/x86_64-linux-gnu/bits/xopen_lim.h:102:7: error: missing binary operator before token "("
  102 | #  if INT_MAX == 2147483647
      |       ^~~~~~~
/usr/include/x86_64-linux-gnu/bits/xopen_lim.h:126:6: error: missing binary operator before token "("
  126 | # if LONG_MAX == 2147483647
      |      ^~~~~~~~
make: *** [../lib.mk:222: /home/azanella/Projects/linux/linux-git/tools/testing/selftests/vDSO/vdso_test_chacha] Error 1


I will try to figure out to be build it correctly, but I think it would be
better to vgetrandom-chacha.S with a different rule.