Messages in this thread | | | Date | Tue, 22 Nov 2011 18:23:06 +0100 | From | Marco Stornelli <> | Subject | Re: [PATCH 2/2] ramoops: remove module parameters |
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Il 21/11/2011 19:11, Kees Cook ha scritto: > On Sat, Nov 19, 2011 at 1:25 AM, Marco Stornelli > <marco.stornelli@gmail.com> wrote: >> Il 18/11/2011 20:31, Kees Cook ha scritto: >>> >>> The ramoops driver is intended to be used with platforms that define >>> persistent memory regions. If memory regions were configurable with >>> module parameters, it would be possible to read some RAM regions via >>> the pstore interface without access to /dev/mem (which would result >>> in a loss of kernel memory privacy when a system is built with >>> STRICT_DEVMEM), so remove this ability completely. >>> >> >> I don't like it very much. The loss of module parameters give us less >> flexibility. The main goal of this driver is debug, so I think it should be >> fast to use. I mean it's not more possible reserve a memory region and load >> the module "on-the-fly", it needs a platform device, it's ok but I think >> it's a little bit more complicated, (without talking about platforms without >> a device tree source). >> I don't understand the problem of strict devmem. We shouldn't use kernel >> memory region but only reserved ones and the driver doesn't use the >> request_mem_region_exclusive, am I wrong? > > Hmmm, maybe I'm reading it backwards, but I think we want it to use > ..._exclusive(). > > int devmem_is_allowed(unsigned long pagenr) > { > if (pagenr<= 256) > return 1; > if (iomem_is_exclusive(pagenr<< PAGE_SHIFT)) > return 0; > if (!page_is_ram(pagenr)) > return 1; > return 0; > } > > If the region is exclusive, access is not allowed (return 0). ramoops > currently uses request_mem_region() instead of > request_mem_region_exclusive(). If we made that switch, I think I'd be > happy. Would this create some problem I'm not seeing? > > -Kees >
I don't understand why we should use the exclusive version, to protect debug data? You should provide a more valid reason to change, because the fact you will be happier with this change is not enough for me :)
Marco
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