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Message-ID: <20170914182205.GA1711@remoulade> Date: Thu, 14 Sep 2017 19:22:08 +0100 From: Mark Rutland <mark.rutland@....com> To: Tycho Andersen <tycho@...ker.com> Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, kernel-hardening@...ts.openwall.com, Marco Benatto <marco.antonio.780@...il.com>, Juerg Haefliger <juerg.haefliger@...onical.com>, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCH v6 05/11] arm64/mm: Add support for XPFO Hi, On Thu, Sep 07, 2017 at 11:36:03AM -0600, Tycho Andersen wrote: > From: Juerg Haefliger <juerg.haefliger@...onical.com> > > Enable support for eXclusive Page Frame Ownership (XPFO) for arm64 and > provide a hook for updating a single kernel page table entry (which is > required by the generic XPFO code). > > v6: use flush_tlb_kernel_range() instead of __flush_tlb_one() > > CC: linux-arm-kernel@...ts.infradead.org > Signed-off-by: Juerg Haefliger <juerg.haefliger@...onical.com> > Signed-off-by: Tycho Andersen <tycho@...ker.com> > --- > arch/arm64/Kconfig | 1 + > arch/arm64/mm/Makefile | 2 ++ > arch/arm64/mm/xpfo.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 61 insertions(+) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index dfd908630631..44fa44ef02ec 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -121,6 +121,7 @@ config ARM64 > select SPARSE_IRQ > select SYSCTL_EXCEPTION_TRACE > select THREAD_INFO_IN_TASK > + select ARCH_SUPPORTS_XPFO A bit of a nit, but this list is (intended to be) organised alphabetically. Could you please try to retain that? i.e. place this between ARCH_SUPPORTS_NUMA_BALANCING and ARCH_WANT_COMPAT_IPC_PARSE_VERSION. > help > ARM 64-bit (AArch64) Linux support. > > diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile > index 9b0ba191e48e..22e5cab543d8 100644 > --- a/arch/arm64/mm/Makefile > +++ b/arch/arm64/mm/Makefile > @@ -11,3 +11,5 @@ KASAN_SANITIZE_physaddr.o += n > > obj-$(CONFIG_KASAN) += kasan_init.o > KASAN_SANITIZE_kasan_init.o := n > + > +obj-$(CONFIG_XPFO) += xpfo.o > diff --git a/arch/arm64/mm/xpfo.c b/arch/arm64/mm/xpfo.c > new file mode 100644 > index 000000000000..678e2be848eb > --- /dev/null > +++ b/arch/arm64/mm/xpfo.c > @@ -0,0 +1,58 @@ > +/* > + * Copyright (C) 2017 Hewlett Packard Enterprise Development, L.P. > + * Copyright (C) 2016 Brown University. All rights reserved. > + * > + * Authors: > + * Juerg Haefliger <juerg.haefliger@....com> > + * Vasileios P. Kemerlis <vpk@...brown.edu> > + * > + * This program is free software; you can redistribute it and/or modify it > + * under the terms of the GNU General Public License version 2 as published by > + * the Free Software Foundation. > + */ > + > +#include <linux/mm.h> > +#include <linux/module.h> > + > +#include <asm/tlbflush.h> > + > +/* > + * Lookup the page table entry for a virtual address and return a pointer to > + * the entry. Based on x86 tree. > + */ Is this intended for kernel VAs, user VAs, or both? There are different constraints for fiddling with either (e.g. holding mmap_sem), so we should be clear regarding the intended use-case. > +static pte_t *lookup_address(unsigned long addr) > +{ > + pgd_t *pgd; > + pud_t *pud; > + pmd_t *pmd; > + > + pgd = pgd_offset_k(addr); > + if (pgd_none(*pgd)) > + return NULL; > + > + pud = pud_offset(pgd, addr); > + if (pud_none(*pud)) > + return NULL; What if it's not none, but not a table? I think we chould check pud_sect() here, and/or pud_bad(). > + > + pmd = pmd_offset(pud, addr); > + if (pmd_none(*pmd)) > + return NULL; Likewise. > + > + return pte_offset_kernel(pmd, addr); > +} Given this expects a pte, it might make more sense to call this lookup_address_pte() to make that clear. > + > +/* Update a single kernel page table entry */ > +inline void set_kpte(void *kaddr, struct page *page, pgprot_t prot) > +{ > + pte_t *pte = lookup_address((unsigned long)kaddr); > + > + set_pte(pte, pfn_pte(page_to_pfn(page), prot)); We can get NULL from lookup_address(), so this doesn't look right. If NULL implies an error, drop a BUG_ON(!pte) before the set_pte. > +} > + > +inline void xpfo_flush_kernel_tlb(struct page *page, int order) > +{ > + unsigned long kaddr = (unsigned long)page_address(page); > + unsigned long size = PAGE_SIZE; unsigned long size = PAGE_SIZE << order; > + > + flush_tlb_kernel_range(kaddr, kaddr + (1 << order) * size); ... and this can be simpler. I haven't brought myself back up to speed, so it might not be possible, but I still think it would be preferable for XPFO to call flush_tlb_kernel_range() directly. Thanks, Mark.
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