When Address Space Layout Randomization (ASLR, randmaps) is enabled, the
address of the VDSO fluctuates from one process to the next. If
Checkpoint/Restore In Userspace (CRIU) is to fully replicate the memory map
of a previous process, it must be able to remap the VDSO of a new process
to the address used by the previous process. Historically this has been
implemented in architecture-specific code for PowerPC and x86. In order to
support 32-bit and 64-bit ARM without further duplication of code, copy
Laurent Dufour's implementation for PowerPC with slight modifications to a
generic location. This is hopefully the beginning of a long process of VDSO
code de-duplication between architectures.
Signed-off-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
---
include/asm-generic/mm_hooks.h | 35 ++++++++++++++++++++++++++++++++---
1 file changed, 32 insertions(+), 3 deletions(-)
diff --git a/include/asm-generic/mm_hooks.h b/include/asm-generic/mm_hooks.h
index cc5d9a1..73f09f1 100644
--- a/include/asm-generic/mm_hooks.h
+++ b/include/asm-generic/mm_hooks.h
@@ -1,7 +1,17 @@
/*
- * Define generic no-op hooks for arch_dup_mmap, arch_exit_mmap
- * and arch_unmap to be included in asm-FOO/mmu_context.h for any
- * arch FOO which doesn't need to hook these.
+ * Define generic hooks for arch_dup_mmap, arch_exit_mmap and arch_unmap to be
+ * included in asm-FOO/mmu_context.h for any arch FOO which doesn't need to
+ * specially hook these.
+ *
+ * arch_remap originally from include/linux-mm-arch-hooks.h
+ * arch_unmap originally from arch/powerpc/include/asm/mmu_context.h
+ * Copyright (C) 2015, IBM Corporation
+ * Author: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
+ *
+ * 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_GENERIC_MM_HOOKS_H
#define _ASM_GENERIC_MM_HOOKS_H
@@ -19,6 +29,25 @@ static inline void arch_unmap(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
+#ifdef CONFIG_GENERIC_VDSO
+ if (start <= mm->context.vdso && mm->context.vdso < end)
+ mm->context.vdso = 0;
+#endif /* CONFIG_GENERIC_VDSO */
+}
+
+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)
+{
+#ifdef CONFIG_GENERIC_VDSO
+ /*
+ * mremap() doesn't allow moving multiple vmas so we can limit the
+ * check to old_addr == vdso.
+ */
+ if (old_addr == mm->context.vdso)
+ mm->context.vdso = new_addr;
+
+#endif /* CONFIG_GENERIC_VDSO */
}
static inline void arch_bprm_mm_init(struct mm_struct *mm,
--
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