Re: [RFC PATCH v7 05/16] arm64/mm: Add support for XPFO
From: Laura Abbott
Date: Tue Feb 12 2019 - 15:01:45 EST
On 2/12/19 7:52 AM, Khalid Aziz wrote:
On 1/23/19 7:24 AM, Konrad Rzeszutek Wilk wrote:
On Thu, Jan 10, 2019 at 02:09:37PM -0700, Khalid Aziz wrote:
From: Juerg Haefliger <juerg.haefliger@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Juerg Haefliger <juerg.haefliger@xxxxxxxxxxxxx>
Signed-off-by: Tycho Andersen <tycho@xxxxxxxxxx>
Signed-off-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
---
arch/arm64/Kconfig | 1 +
arch/arm64/mm/Makefile | 2 ++
arch/arm64/mm/xpfo.c | 58 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 61 insertions(+)
create mode 100644 arch/arm64/mm/xpfo.c
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ea2ab0330e3a..f0a9c0007d23 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -171,6 +171,7 @@ config ARM64
select SWIOTLB
select SYSCTL_EXCEPTION_TRACE
select THREAD_INFO_IN_TASK
+ select ARCH_SUPPORTS_XPFO
help
ARM 64-bit (AArch64) Linux support.
diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index 849c1df3d214..cca3808d9776 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -12,3 +12,5 @@ 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@xxxxxxx>
+ * Vasileios P. Kemerlis <vpk@xxxxxxxxxxxx>
+ *
+ * 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.
+ */
+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;
+
+ pmd = pmd_offset(pud, addr);
+ if (pmd_none(*pmd))
+ return NULL;
+
+ return pte_offset_kernel(pmd, addr);
+}
+
+/* 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));
Thought on the other hand.. what if the page is PMD? Do you really want
to do this?
What if 'pte' is NULL?
+}
+
+inline void xpfo_flush_kernel_tlb(struct page *page, int order)
+{
+ unsigned long kaddr = (unsigned long)page_address(page);
+ unsigned long size = PAGE_SIZE;
+
+ flush_tlb_kernel_range(kaddr, kaddr + (1 << order) * size);
Ditto here. You are assuming it is PTE, but it may be PMD or such.
Or worts - the lookup_address could be NULL.
+}
--
2.17.1
Hi Konrad,
This makes sense. x86 version of set_kpte() checks pte for NULL and also
checks if the page is PMD. Now what you said about adding level to
lookup_address() for arm makes more sense.
Can someone with knowledge of arm64 mmu make recommendations here?
Thanks,
Khalid
arm64 can't split larger pages and requires everything must be
mapped as pages (see [RFC PATCH v7 08/16] arm64/mm: disable
section/contiguous mappings if XPFO is enabled) . Any
situation where we would get something other than a pte
would be a bug.
Thanks,
Laura