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

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Date: Wed, 20 Mar 2024 14:08:25 -0700
From: Kees Cook <keescook@...omium.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Michael Ellerman <mpe@...erman.id.au>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vincenzo Frascino <vincenzo.frascino@....com>,
	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>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vdso: use CONFIG_PAGE_SHIFT in vdso/datapage.h

On Wed, Mar 20, 2024 at 07:02:15PM +0100, Arnd Bergmann wrote:
> 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>

Thanks for tracking this!

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook