linux-kernel - Re: [RFC PATCH v1 16/57] perf: Remove PAGE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c997e5c6-ba45-4492-95ce-28747643bd39@arm.com>
Date: Wed, 16 Oct 2024 15:40:41 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Andrew Morton <akpm@...ux-foundation.org>,
 Anshuman Khandual <anshuman.khandual@....com>,
 Ard Biesheuvel <ardb@...nel.org>, Catalin Marinas <catalin.marinas@....com>,
 David Hildenbrand <david@...hat.com>, Greg Marsden
 <greg.marsden@...cle.com>, Ivan Ivanov <ivan.ivanov@...e.com>,
 Kalesh Singh <kaleshsingh@...gle.com>, Marc Zyngier <maz@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Matthias Brugger <mbrugger@...e.com>,
 Miroslav Benes <mbenes@...e.cz>, Will Deacon <will@...nel.org>,
 Arnaldo Carvalho de Melo <acme@...nel.org>, Ingo Molnar <mingo@...hat.com>,
 Namhyung Kim <namhyung@...nel.org>, Peter Zijlstra <peterz@...radead.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, linux-perf-users@...r.kernel.org
Subject: Re: [RFC PATCH v1 16/57] perf: Remove PAGE_SIZE compile-time constant
 assumption

+ Arnaldo Carvalho de Melo, Ingo Molnar, Namhyung Kim, Peter Zijlstra

This was a rather tricky series to get the recipients correct for and my script
did not realize that "supporter" was a pseudonym for "maintainer" so you were
missed off the original post. Appologies!

More context in cover letter:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/


On 14/10/2024 11:58, Ryan Roberts wrote:
> To prepare for supporting boot-time page size selection, refactor code
> to remove assumptions about PAGE_SIZE being compile-time constant. Code
> intended to be equivalent when compile-time page size is active.
> 
> Refactor a BUILD_BUG_ON() so that we test against the limit; _format is
> invariant to page size so testing it is no bigger than the minimum
> supported size is sufficient.
> 
> Wrap global variables that are initialized with PAGE_SIZE derived values
> using DEFINE_GLOBAL_PAGE_SIZE_VAR() so their initialization can be
> deferred for boot-time page size builds.
> 
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
> 
> ***NOTE***
> Any confused maintainers may want to read the cover note here for context:
> https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/
> 
>  include/linux/perf_event.h | 2 +-
>  kernel/events/core.c       | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 1a8942277ddad..b7972155f93eb 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1872,7 +1872,7 @@ _name##_show(struct device *dev,					\
>  			       struct device_attribute *attr,		\
>  			       char *page)				\
>  {									\
> -	BUILD_BUG_ON(sizeof(_format) >= PAGE_SIZE);			\
> +	BUILD_BUG_ON(sizeof(_format) >= PAGE_SIZE_MIN);			\
>  	return sprintf(page, _format "\n");				\
>  }									\
>  
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 8a6c6bbcd658a..81149663ab7d8 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -419,7 +419,7 @@ static struct kmem_cache *perf_event_cache;
>  int sysctl_perf_event_paranoid __read_mostly = 2;
>  
>  /* Minimum for 512 kiB + 1 user control page */
> -int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
> +__DEFINE_GLOBAL_PAGE_SIZE_VAR(int, sysctl_perf_event_mlock, __read_mostly, 512 + (PAGE_SIZE / 1024)); /* 'free' kiB per user */
>  
>  /*
>   * max perf event sample rate