linux-kernel - Re: [PATCH] vdso: use CONFIG_PAGE

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Message-ID: <87h6gzzrg9.fsf@mail.lhotse>
Date: Thu, 21 Mar 2024 23:42:46 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Arnd Bergmann <arnd@...nel.org>, Andy Lutomirski <luto@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Vincenzo Frascino
 <vincenzo.frascino@....com>
Cc: Arnd Bergmann <arnd@...db.de>, linuxppc-dev@...ts.ozlabs.org, Anna-Maria
 Behnsen <anna-maria@...utronix.de>, Nicholas Piggin <npiggin@...il.com>,
 Christophe Leroy <christophe.leroy@...roup.eu>, "Aneesh Kumar K.V"
 <aneesh.kumar@...nel.org>, "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
 Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vdso: use CONFIG_PAGE_SHIFT in vdso/datapage.h

Arnd Bergmann <arnd@...nel.org> writes:
> From: Arnd Bergmann <arnd@...db.de>
>
> Both the vdso rework and the CONFIG_PAGE_SHIFT changes were merged during
> the v6.9 merge window, so it is now possible to use CONFIG_PAGE_SHIFT
> instead of including asm/page.h in the vdso.
>
> This avoids the workaround for arm64 and addresses a build warning
> for powerpc64:
>
> In file included from <built-in>:4:
> In file included from /home/arnd/arm-soc/arm-soc/lib/vdso/gettimeofday.c:5:
> In file included from ../include/vdso/datapage.h:25:
> arch/powerpc/include/asm/page.h:230:9: error: result of comparison of constant 13835058055282163712 with expression of type 'unsigned long' is always true [-Werror,-Wtautological-constant-out-of-range-compare]
>   230 |         return __pa(kaddr) >> PAGE_SHIFT;
>       |                ^~~~~~~~~~~
> arch/powerpc/include/asm/page.h:217:37: note: expanded from macro '__pa'
>   217 |         VIRTUAL_WARN_ON((unsigned long)(x) < PAGE_OFFSET);              \
>       |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
> arch/powerpc/include/asm/page.h:202:73: note: expanded from macro 'VIRTUAL_WARN_ON'
>   202 | #define VIRTUAL_WARN_ON(x)      WARN_ON(IS_ENABLED(CONFIG_DEBUG_VIRTUAL) && (x))
>       |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
> arch/powerpc/include/asm/bug.h:88:25: note: expanded from macro 'WARN_ON'
>    88 |         int __ret_warn_on = !!(x);                              \
>       |                                ^
>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Vincenzo Frascino <vincenzo.frascino@....com>
> Cc: Anna-Maria Behnsen <anna-maria@...utronix.de>
> See-also: 8b3843ae3634 ("vdso/datapage: Quick fix - use asm/page-def.h for ARM64")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/powerpc/include/asm/vdso/gettimeofday.h | 3 +--
>  include/vdso/datapage.h                      | 8 +-------
>  2 files changed, 2 insertions(+), 9 deletions(-)

Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)

cheers

> diff --git a/arch/powerpc/include/asm/vdso/gettimeofday.h b/arch/powerpc/include/asm/vdso/gettimeofday.h
> index f0a4cf01e85c..78302f6c2580 100644
> --- a/arch/powerpc/include/asm/vdso/gettimeofday.h
> +++ b/arch/powerpc/include/asm/vdso/gettimeofday.h
> @@ -4,7 +4,6 @@
>  
>  #ifndef __ASSEMBLY__
>  
> -#include <asm/page.h>
>  #include <asm/vdso/timebase.h>
>  #include <asm/barrier.h>
>  #include <asm/unistd.h>
> @@ -95,7 +94,7 @@ const struct vdso_data *__arch_get_vdso_data(void);
>  static __always_inline
>  const struct vdso_data *__arch_get_timens_vdso_data(const struct vdso_data *vd)
>  {
> -	return (void *)vd + PAGE_SIZE;
> +	return (void *)vd + (1U << CONFIG_PAGE_SHIFT);
>  }
>  #endif
>  
> diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
> index 5d5c0b8efff2..c71ddb6d4691 100644
> --- a/include/vdso/datapage.h
> +++ b/include/vdso/datapage.h
> @@ -19,12 +19,6 @@
>  #include <vdso/time32.h>
>  #include <vdso/time64.h>
>  
> -#ifdef CONFIG_ARM64
> -#include <asm/page-def.h>
> -#else
> -#include <asm/page.h>
> -#endif
> -
>  #ifdef CONFIG_ARCH_HAS_VDSO_DATA
>  #include <asm/vdso/data.h>
>  #else
> @@ -132,7 +126,7 @@ extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden
>   */
>  union vdso_data_store {
>  	struct vdso_data	data[CS_BASES];
> -	u8			page[PAGE_SIZE];
> +	u8			page[1U << CONFIG_PAGE_SHIFT];
>  };
>  
>  /*
> -- 
> 2.39.2