netdev - Re: [PATCH v7 1/5] add infrastructure for tagging functions as error injectable

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Message-ID: <20171128115841.4958113d@lwn.net>
Date:   Tue, 28 Nov 2017 11:58:41 -0700
From:   Jonathan Corbet <corbet@....net>
To:     Josef Bacik <josef@...icpanda.com>
Cc:     rostedt@...dmis.org, mingo@...hat.com, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ast@...nel.org, kernel-team@...com, daniel@...earbox.net,
        linux-btrfs@...r.kernel.org, Josef Bacik <jbacik@...com>
Subject: Re: [PATCH v7 1/5] add infrastructure for tagging functions as
 error injectable

On Wed, 22 Nov 2017 16:23:30 -0500
Josef Bacik <josef@...icpanda.com> wrote:

> From: Josef Bacik <jbacik@...com>
> 
> Using BPF we can override kprob'ed functions and return arbitrary
> values.  Obviously this can be a bit unsafe, so make this feature opt-in
> for functions.  Simply tag a function with KPROBE_ERROR_INJECT_SYMBOL in
> order to give BPF access to that function for error injection purposes.
> 
> Signed-off-by: Josef Bacik <jbacik@...com>
> Acked-by: Ingo Molnar <mingo@...nel.org>
> ---
>  arch/x86/include/asm/asm.h        |   6 ++
>  include/asm-generic/vmlinux.lds.h |  10 +++
>  include/linux/bpf.h               |  11 +++
>  include/linux/kprobes.h           |   1 +
>  include/linux/module.h            |   5 ++
>  kernel/kprobes.c                  | 163 ++++++++++++++++++++++++++++++++++++++
>  kernel/module.c                   |   6 +-
>  7 files changed, 201 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
> index b0dc91f4bedc..340f4cc43255 100644
> --- a/arch/x86/include/asm/asm.h
> +++ b/arch/x86/include/asm/asm.h
> @@ -85,6 +85,12 @@
>  	_ASM_PTR (entry);					\
>  	.popsection
>  
> +# define _ASM_KPROBE_ERROR_INJECT(entry)			\
> +	.pushsection "_kprobe_error_inject_list","aw" ;		\
> +	_ASM_ALIGN ;						\
> +	_ASM_PTR (entry);					\
> +	.popseciton

So this stuff is not my area of greatest expertise, but I do have to wonder
how ".popseciton" can work ... ?

Thanks,

jon