[RFC 3/5] mm/powerpc: Make VDSO remap generic

[Christopher Covington]

In order to support remapping the VDSO on additional architectures without
duplicating code, move the remap code out from arch/powerpc. Architectures
that wish to use the generic logic must have an unsigned long vdso in
mm->context and can opt in by selecting CONFIG_ARCH_WANT_VDSO_MAP. This
allows PowerPC to use mm-arch-hooks.h from include/asm-generic.

Signed-off-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
---
 arch/powerpc/include/asm/Kbuild          |  1 +
 arch/powerpc/include/asm/mm-arch-hooks.h | 28 ----------------------------
 mm/mremap.c                              | 10 ++++++++--
 3 files changed, 9 insertions(+), 30 deletions(-)
 delete mode 100644 arch/powerpc/include/asm/mm-arch-hooks.h

diff --git a/arch/powerpc/include/asm/Kbuild b/arch/powerpc/include/asm/Kbuild
index ab9f4e0..9dbb372 100644
--- a/arch/powerpc/include/asm/Kbuild
+++ b/arch/powerpc/include/asm/Kbuild
@@ -7,3 +7,4 @@ generic-y += mcs_spinlock.h
 generic-y += preempt.h
 generic-y += rwsem.h
 generic-y += vtime.h
+generic-y += mm-arch-hooks.h
diff --git a/arch/powerpc/include/asm/mm-arch-hooks.h b/arch/powerpc/include/asm/mm-arch-hooks.h
deleted file mode 100644
index ea6da89..0000000
--- a/arch/powerpc/include/asm/mm-arch-hooks.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- * Architecture specific mm hooks
- *
- * 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_POWERPC_MM_ARCH_HOOKS_H
-#define _ASM_POWERPC_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.
-	 */
-	if (old_start == mm->context.vdso)
-		mm->context.vdso = new_start;
-}
-#define arch_remap arch_remap
-
-#endif /* _ASM_POWERPC_MM_ARCH_HOOKS_H */
diff --git a/mm/mremap.c b/mm/mremap.c
index 3fa0a467..59032b7 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -293,8 +293,14 @@ static unsigned long move_vma(struct vm_area_struct *vma,
 		old_addr = new_addr;
 		new_addr = err;
 	} else {
-		arch_remap(mm, old_addr, old_addr + old_len,
-			   new_addr, new_addr + new_len);
+#ifdef CONFIG_ARCH_WANT_VDSO_MAP
+		/*
+		 * 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_ARCH_WANT_VDSO_MAP */
 	}
 
 	/* Conceal VM_ACCOUNT so old reservation is not undone */
-- 
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