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

Adhemerval Zanella Netto
2024-08-27T13:17:24Z

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.