Re: [PATCH 14(16] pramfs: memory protection
> per-arch?! Wow. Mmm...maybe I have to change something at fs level to > avoid that. An alternative could be to use the follow_pte solution but > avoid the protection via Kconfig if the fs is used on some archs (ia64 > or MIPS), with large pages and so on. An help of the kernel community > to know all these particular cases is welcome. It depends if the protection is a fundamental part of your design (but if it is I would argue that's broken because it's really not very good protection): If it's just an optional nice to have you can stub it out on architectures that don't support it. -Andi -- a...@linux.intel.com -- Speaking for myself only. -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 14(16] pramfs: memory protection
2010/10/12 Andi Kleen : > On Mon, Oct 11, 2010 at 07:32:10PM +0200, Marco Stornelli wrote: >> Il 10/10/2010 18:46, Andi Kleen ha scritto: >> > This won't work at all on x86 because you don't handle large >> > pages. >> > >> > And it doesn't work on x86-64 because the first 2GB are double >> > mapped (direct and kernel text mapping) >> > >> > Thirdly I expect it won't either on architectures that map >> > the direct mapping with special registers (like IA64 or MIPS) >> >> Andi, what do you think to use the already implemented follow_pte >> instead? > > Has all the same problems. Really you need an per architecture > function. Perhaps some architectures could use a common helper, > but certainly not all. > per-arch?! Wow. Mmm...maybe I have to change something at fs level to avoid that. An alternative could be to use the follow_pte solution but avoid the protection via Kconfig if the fs is used on some archs (ia64 or MIPS), with large pages and so on. An help of the kernel community to know all these particular cases is welcome. Regards, Marco -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 14(16] pramfs: memory protection
On Mon, Oct 11, 2010 at 07:32:10PM +0200, Marco Stornelli wrote: > Il 10/10/2010 18:46, Andi Kleen ha scritto: > > This won't work at all on x86 because you don't handle large > > pages. > > > > And it doesn't work on x86-64 because the first 2GB are double > > mapped (direct and kernel text mapping) > > > > Thirdly I expect it won't either on architectures that map > > the direct mapping with special registers (like IA64 or MIPS) > > Andi, what do you think to use the already implemented follow_pte > instead? Has all the same problems. Really you need an per architecture function. Perhaps some architectures could use a common helper, but certainly not all. x86 already has some infrastructure for this, but it currently has serious problems too (like not merging mappings on unmap) and is generally overdesigned ugly code. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
