linux-kernel - Re: [PATCH v2 1/2] arm64: ftrace: stop using kstop

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: <20151203221241.07ff092e@grimm.local.home>
Date:	Thu, 3 Dec 2015 22:12:41 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Li Bin <huawei.libin@...wei.com>
Cc:	<will.deacon@....com>, <catalin.marinas@....com>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <mingo@...hat.com>,
	<guohanjun@...wei.com>, <dingtianhong@...wei.com>
Subject: Re: [PATCH v2 1/2] arm64: ftrace: stop using kstop_machine to
 enable/disable tracing

On Fri, 4 Dec 2015 10:18:38 +0800
Li Bin <huawei.libin@...wei.com> wrote:

> For ftrace on arm64, kstop_machine which is hugely disruptive
> to a running system is not needed to convert nops to ftrace calls
> or back, because that to be modified instrucions, that NOP, B or BL,
> are all safe instructions which called "concurrent modification
> and execution of instructions", that can be executed by one
> thread of execution as they are being modified by another thread
> of execution without requiring explicit synchronization.
> 
> Signed-off-by: Li Bin <huawei.libin@...wei.com>
> ---
>  arch/arm64/kernel/ftrace.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
> index c851be7..9669b33 100644
> --- a/arch/arm64/kernel/ftrace.c
> +++ b/arch/arm64/kernel/ftrace.c
> @@ -93,6 +93,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
>  	return ftrace_modify_code(pc, old, new, true);
>  }
>  
> +void arch_ftrace_update_code(int command)
> +{
> +	ftrace_modify_all_code(command);

Hmm, I wonder why I haven't done this for powerpc. I probably should.

Anyway,

Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

If it is indeed safe not to do any special handling.

-- Steve

> +}
> +
>  int __init ftrace_dyn_arch_init(void)
>  {
>  	return 0;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/