linux-kernel - Re: [PATCH 1/9] x86: vdso: Introduce asm/vdso/mman.h

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Message-ID: <710f9663-e99c-40e2-9c0e-2f5e6e854653@csgroup.eu>
Date: Wed, 4 Sep 2024 18:56:35 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Vincenzo Frascino <vincenzo.frascino@....com>,
 linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, linux-mm@...ck.org
Cc: Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
 "Jason A . Donenfeld" <Jason@...c4.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>,
 Naveen N Rao <naveen@...nel.org>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H . Peter Anvin" <hpa@...or.com>, Theodore Ts'o <tytso@....edu>,
 Arnd Bergmann <arnd@...db.de>, Andrew Morton <akpm@...ux-foundation.org>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH 1/9] x86: vdso: Introduce asm/vdso/mman.h

Le 03/09/2024 à 17:14, Vincenzo Frascino a écrit :
> The VDSO implementation includes headers from outside of the
> vdso/ namespace.
> 
> Introduce asm/vdso/mman.h to make sure that the generic library
> uses only the allowed namespace.
> 
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Jason A. Donenfeld <Jason@...c4.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
> ---
>   arch/x86/include/asm/vdso/mman.h | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
>   create mode 100644 arch/x86/include/asm/vdso/mman.h
> 
> diff --git a/arch/x86/include/asm/vdso/mman.h b/arch/x86/include/asm/vdso/mman.h
> new file mode 100644
> index 000000000000..4c936c9d11ab
> --- /dev/null
> +++ b/arch/x86/include/asm/vdso/mman.h
> @@ -0,0 +1,15 @@
> +
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __ASM_VDSO_MMAN_H
> +#define __ASM_VDSO_MMAN_H
> +
> +#ifndef __ASSEMBLY__
> +
> +#include <uapi/linux/mman.h>
> +
> +#define VDSO_MMAP_PROT	PROT_READ | PROT_WRITE
> +#define VDSO_MMAP_FLAGS	MAP_DROPPABLE | MAP_ANONYMOUS

I still can't see the benefit of duplicating those two defines in every 
arch.

I understand your point that some arch might in the future want to use 
different flags, but unless we already have one such architecture in 
mind we shouldn't make things more complicated than needed.

In case such an architecture is already identified it should be said in 
the commit message

> +
> +#endif /* !__ASSEMBLY__ */
> +
> +#endif /* __ASM_VDSO_MMAN_H */