linux-kernel - Re: [PATCH v11 02/12] scs: add accounting

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Date:   Mon, 20 Apr 2020 18:17:55 +0100
From:   Will Deacon <will@...nel.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dave Martin <Dave.Martin@....com>,
        Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        clang-built-linux@...glegroups.com,
        kernel-hardening@...ts.openwall.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 02/12] scs: add accounting

On Thu, Apr 16, 2020 at 09:12:35AM -0700, Sami Tolvanen wrote:
> This change adds accounting for the memory allocated for shadow stacks.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> ---
>  drivers/base/node.c    |  6 ++++++
>  fs/proc/meminfo.c      |  4 ++++
>  include/linux/mmzone.h |  3 +++
>  kernel/scs.c           | 20 ++++++++++++++++++++
>  mm/page_alloc.c        |  6 ++++++
>  mm/vmstat.c            |  3 +++
>  6 files changed, 42 insertions(+)
> 
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 10d7e818e118..502ab5447c8d 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -415,6 +415,9 @@ static ssize_t node_read_meminfo(struct device *dev,
>  		       "Node %d AnonPages:      %8lu kB\n"
>  		       "Node %d Shmem:          %8lu kB\n"
>  		       "Node %d KernelStack:    %8lu kB\n"
> +#ifdef CONFIG_SHADOW_CALL_STACK
> +		       "Node %d ShadowCallStack:%8lu kB\n"
> +#endif
>  		       "Node %d PageTables:     %8lu kB\n"
>  		       "Node %d NFS_Unstable:   %8lu kB\n"
>  		       "Node %d Bounce:         %8lu kB\n"
> @@ -438,6 +441,9 @@ static ssize_t node_read_meminfo(struct device *dev,
>  		       nid, K(node_page_state(pgdat, NR_ANON_MAPPED)),
>  		       nid, K(i.sharedram),
>  		       nid, sum_zone_node_page_state(nid, NR_KERNEL_STACK_KB),
> +#ifdef CONFIG_SHADOW_CALL_STACK
> +		       nid, sum_zone_node_page_state(nid, NR_KERNEL_SCS_BYTES) / 1024,
> +#endif

Why not just use KB everywhere instead of repeated division by 1024?

Will