From: Christopher M Riedl <cmr@informatik.wtf>
To: Christophe Leroy <christophe.leroy@c-s.fr>, linuxppc-dev@ozlabs.org
Cc: andonnel@au1.ibm.com
Subject: Re: [PATCH] powerpc/xmon: add read-only mode
Date: Wed, 3 Apr 2019 09:15:41 -0400 (EDT) [thread overview]
Message-ID: <1310218751.18777.1554297341318@privateemail.com> (raw)
In-Reply-To: <ee41455c-0ef8-2b5b-2f61-16bcf5f45d3f@c-s.fr>
> On April 3, 2019 at 12:15 AM Christophe Leroy <christophe.leroy@c-s.fr> wrote:
>
>
>
>
> Le 03/04/2019 à 05:38, Christopher M Riedl a écrit :
> >> On March 29, 2019 at 3:41 AM Christophe Leroy <christophe.leroy@c-s.fr> wrote:
> >>
> >>
> >>
> >>
> >> Le 29/03/2019 à 05:21, cmr a écrit :
> >>> Operations which write to memory should be restricted on secure systems
> >>> and optionally to avoid self-destructive behaviors.
> >>>
> >>> Add a config option, XMON_RO, to control default xmon behavior along
> >>> with kernel cmdline options xmon=ro and xmon=rw for explicit control.
> >>> The default is to enable read-only mode.
> >>>
> >>> The following xmon operations are affected:
> >>> memops:
> >>> disable memmove
> >>> disable memset
> >>> memex:
> >>> no-op'd mwrite
> >>> super_regs:
> >>> no-op'd write_spr
> >>> bpt_cmds:
> >>> disable
> >>> proc_call:
> >>> disable
> >>>
> >>> Signed-off-by: cmr <cmr@informatik.wtf>
> >>
> >> A Fully qualified name should be used.
> >
> > What do you mean by fully-qualified here? PPC_XMON_RO? (PPC_)XMON_READONLY?
>
> I mean it should be
>
> Signed-off-by: Christopher M Riedl <cmr@informatik.wtf>
>
> instead of
>
> Signed-off-by: cmr <cmr@informatik.wtf>
>
Hehe, thanks :)
> >
> >>
> >>> ---
> >>> arch/powerpc/Kconfig.debug | 7 +++++++
> >>> arch/powerpc/xmon/xmon.c | 24 ++++++++++++++++++++++++
> >>> 2 files changed, 31 insertions(+)
> >>>
> >>> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
> >>> index 4e00cb0a5464..33cc01adf4cb 100644
> >>> --- a/arch/powerpc/Kconfig.debug
> >>> +++ b/arch/powerpc/Kconfig.debug
> >>> @@ -117,6 +117,13 @@ config XMON_DISASSEMBLY
> >>> to say Y here, unless you're building for a memory-constrained
> >>> system.
> >>>
> >>> +config XMON_RO
> >>> + bool "Set xmon read-only mode"
> >>> + depends on XMON
> >>> + default y
> >>
> >> Should it really be always default y ?
> >> I would set default 'y' only when some security options are also set.
> >>
> >
> > This is a good point, I based this on an internal Slack suggestion but giving this more thought, disabling read-only mode by default makes more sense. I'm not sure what security options could be set though?
> >
>
> Maybe starting with CONFIG_STRICT_KERNEL_RWX
>
> Another point that may also be addressed by your patch is the definition
> of PAGE_KERNEL_TEXT:
>
> #if defined(CONFIG_KGDB) || defined(CONFIG_XMON) ||
> defined(CONFIG_BDI_SWITCH) ||\
> defined(CONFIG_KPROBES) || defined(CONFIG_DYNAMIC_FTRACE)
> #define PAGE_KERNEL_TEXT PAGE_KERNEL_X
> #else
> #define PAGE_KERNEL_TEXT PAGE_KERNEL_ROX
> #endif
>
> The above let me think that it would be better if you add a config
> XMON_RW instead of XMON_RO, with default !STRICT_KERNEL_RWX
>
> Christophe
Thanks! I like that a lot better, this, along with your other suggestions
in the initial review, will be in the next version.
prev parent reply other threads:[~2019-04-03 13:17 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-29 4:21 [PATCH] powerpc/xmon: add read-only mode cmr
2019-03-29 4:49 ` Andrew Donnellan
2019-04-03 13:02 ` Christopher M Riedl
2019-04-03 23:59 ` Andrew Donnellan
2019-03-29 7:41 ` Christophe Leroy
2019-04-03 3:38 ` Christopher M Riedl
2019-04-03 4:15 ` Christophe Leroy
2019-04-03 13:15 ` Christopher M Riedl [this message]
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