[PATCH] arm64: Support VDSO remapping

[Christopher Covington]

Some applications such as Checkpoint/Restore In Userspace (CRIU) remap and
unmap the VDSO. Add support for this to the AArch64 kernel by copying in
the PowerPC code with slight modifications.

Signed-off-by: Christopher Covington <cov at codeaurora.org>
---
 arch/arm64/include/asm/Kbuild          |  1 -
 arch/arm64/include/asm/mm-arch-hooks.h | 28 ++++++++++++++++++++++++++++
 arch/arm64/include/asm/mmu_context.h   | 23 ++++++++++++++++++++++-
 3 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 arch/arm64/include/asm/mm-arch-hooks.h

diff --git a/arch/arm64/include/asm/Kbuild b/arch/arm64/include/asm/Kbuild
index 70fd9ff..b112a39 100644
--- a/arch/arm64/include/asm/Kbuild
+++ b/arch/arm64/include/asm/Kbuild
@@ -25,7 +25,6 @@ generic-y += kvm_para.h
 generic-y += local.h
 generic-y += local64.h
 generic-y += mcs_spinlock.h
-generic-y += mm-arch-hooks.h
 generic-y += mman.h
 generic-y += msgbuf.h
 generic-y += msi.h
diff --git a/arch/arm64/include/asm/mm-arch-hooks.h b/arch/arm64/include/asm/mm-arch-hooks.h
new file mode 100644
index 0000000..e6923fb
--- /dev/null
+++ b/arch/arm64/include/asm/mm-arch-hooks.h
@@ -0,0 +1,28 @@
+/*
+ * Architecture specific mm hooks
+ *
+ * Copyright (C) 2015, IBM Corporation
+ * Author: Laurent Dufour <ldufour at linux.vnet.ibm.com>
+ *
+ * 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.
+ */
+
+#ifndef __ASM_MM_ARCH_HOOKS_H
+#define __ASM_MM_ARCH_HOOKS_H
+
+static inline void arch_remap(struct mm_struct *mm,
+			      unsigned long old_start, unsigned long old_end,
+			      unsigned long new_start, unsigned long new_end)
+{
+	/*
+	 * mremap() doesn't allow moving multiple vmas so we can limit the
+	 * check to old_start == vdso_base.
+	 */
+	if ((void *)old_start == mm->context.vdso)
+		mm->context.vdso = (void *)new_start;
+}
+#define arch_remap arch_remap
+
+#endif /* __ASM_MM_ARCH_HOOKS_H */
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index 2416578..9fe0773 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -24,7 +24,6 @@
 
 #include <asm/cacheflush.h>
 #include <asm/proc-fns.h>
-#include <asm-generic/mm_hooks.h>
 #include <asm/cputype.h>
 #include <asm/pgtable.h>
 
@@ -147,4 +146,26 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next,
 #define deactivate_mm(tsk,mm)	do { } while (0)
 #define activate_mm(prev,next)	switch_mm(prev, next, NULL)
 
+static inline void arch_dup_mmap(struct mm_struct *oldmm,
+				      struct mm_struct *mm)
+{
+}
+
+static inline void arch_exit_mmap(struct mm_struct *mm)
+{
+}
+
+static inline void arch_unmap(struct mm_struct *mm,
+			      struct vm_area_struct *vma,
+			      unsigned long start, unsigned long end)
+{
+	if ((void *)start <= mm->context.vdso && mm->context.vdso < (void *)end)
+		mm->context.vdso = NULL;
+}
+
+static inline void arch_bprm_mm_init(struct mm_struct *mm,
+				     struct vm_area_struct *vma)
+{
+}
+
 #endif
-- 
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