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

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Message-ID: <Zs3V3FYwz57tyGgp@zx2c4.com>
Date: Tue, 27 Aug 2024 15:34:20 +0200
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>
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 Tue, Aug 27, 2024 at 10:17:18AM -0300, Adhemerval Zanella Netto wrote:
> 
> 
> 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

You get that even with the latest random.git? I thought Christophe's
patch fixed that, but maybe not and I should just remove the dependency
on the sodium header instead.

Jason