powerpc/mm: Use generic_get_unmapped_area() and call it from arch_get_unmapped_area()

Use the generic version of arch_get_unmapped_area() which
is now available at all time instead of its copy
radix__arch_get_unmapped_area()

To allow that for PPC64, add arch_get_mmap_base() and
arch_get_mmap_end() macros.

Instead of setting mm->get_unmapped_area() to either
arch_get_unmapped_area() or generic_get_unmapped_area(),
always set it to arch_get_unmapped_area() and call
generic_get_unmapped_area() from there when radix is enabled.

Do the same with radix__arch_get_unmapped_area_topdown()
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/393be1fa386446443682fdb74544d733f68ef3bb.1649523076.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/task_size_64.h

@@ -72,4 +72,12 @@
 #define STACK_TOP_MAX TASK_SIZE_USER64
 #define STACK_TOP (is_32bit_task() ? STACK_TOP_USER32 : STACK_TOP_USER64)
 
+#define arch_get_mmap_base(addr, base) \
+	(((addr) > DEFAULT_MAP_WINDOW) ? (base) + TASK_SIZE - DEFAULT_MAP_WINDOW : (base))
+
+#define arch_get_mmap_end(addr, len, flags) \
+	(((addr) > DEFAULT_MAP_WINDOW) || \
+	 (((flags) & MAP_FIXED) && ((addr) + (len) > DEFAULT_MAP_WINDOW)) ? TASK_SIZE : \
+									    DEFAULT_MAP_WINDOW)
+
 #endif /* _ASM_POWERPC_TASK_SIZE_64_H */

arch/powerpc/mm/mmap.c

@@ -81,115 +81,15 @@ static inline unsigned long mmap_base(unsigned long rnd,
 }
 
 #ifdef HAVE_ARCH_UNMAPPED_AREA
-#ifdef CONFIG_PPC_RADIX_MMU
-/*
- * Same function as generic code used only for radix, because we don't need to overload
- * the generic one. But we will have to duplicate, because hash select
- * HAVE_ARCH_UNMAPPED_AREA
- */
-static unsigned long
-radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
-			     unsigned long len, unsigned long pgoff,
-			     unsigned long flags)
-{
-	struct mm_struct *mm = current->mm;
-	struct vm_area_struct *vma;
-	int fixed = (flags & MAP_FIXED);
-	unsigned long high_limit;
-	struct vm_unmapped_area_info info;
-
-	high_limit = DEFAULT_MAP_WINDOW;
-	if (addr >= high_limit || (fixed && (addr + len > high_limit)))
-		high_limit = TASK_SIZE;
-
-	if (len > high_limit)
-		return -ENOMEM;
-
-	if (fixed) {
-		if (addr > high_limit - len)
-			return -ENOMEM;
-		return addr;
-	}
-
-	if (addr) {
-		addr = PAGE_ALIGN(addr);
-		vma = find_vma(mm, addr);
-		if (high_limit - len >= addr && addr >= mmap_min_addr &&
-		    (!vma || addr + len <= vm_start_gap(vma)))
-			return addr;
-	}
-
-	info.flags = 0;
-	info.length = len;
-	info.low_limit = mm->mmap_base;
-	info.high_limit = high_limit;
-	info.align_mask = 0;
-
-	return vm_unmapped_area(&info);
-}
-
-static unsigned long
-radix__arch_get_unmapped_area_topdown(struct file *filp,
-				     const unsigned long addr0,
-				     const unsigned long len,
-				     const unsigned long pgoff,
-				     const unsigned long flags)
-{
-	struct vm_area_struct *vma;
-	struct mm_struct *mm = current->mm;
-	unsigned long addr = addr0;
-	int fixed = (flags & MAP_FIXED);
-	unsigned long high_limit;
-	struct vm_unmapped_area_info info;
-
-	high_limit = DEFAULT_MAP_WINDOW;
-	if (addr >= high_limit || (fixed && (addr + len > high_limit)))
-		high_limit = TASK_SIZE;
-
-	if (len > high_limit)
-		return -ENOMEM;
-
-	if (fixed) {
-		if (addr > high_limit - len)
-			return -ENOMEM;
-		return addr;
-	}
-
-	if (addr) {
-		addr = PAGE_ALIGN(addr);
-		vma = find_vma(mm, addr);
-		if (high_limit - len >= addr && addr >= mmap_min_addr &&
-		    (!vma || addr + len <= vm_start_gap(vma)))
-			return addr;
-	}
-
-	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
-	info.length = len;
-	info.low_limit = max(PAGE_SIZE, mmap_min_addr);
-	info.high_limit = mm->mmap_base + (high_limit - DEFAULT_MAP_WINDOW);
-	info.align_mask = 0;
-
-	addr = vm_unmapped_area(&info);
-	if (!(addr & ~PAGE_MASK))
-		return addr;
-	VM_BUG_ON(addr != -ENOMEM);
-
-	/*
-	 * A failed mmap() very likely causes application failure,
-	 * so fall back to the bottom-up function here. This scenario
-	 * can happen with large stack limits and large mmap()
-	 * allocations.
-	 */
-	return radix__arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
-}
-#endif
-
 unsigned long arch_get_unmapped_area(struct file *filp,
 				     unsigned long addr,
 				     unsigned long len,
 				     unsigned long pgoff,
 				     unsigned long flags)
 {
+	if (radix_enabled())
+		return generic_get_unmapped_area(filp, addr, len, pgoff, flags);
+
 #ifdef CONFIG_PPC_64S_HASH_MMU
 	return slice_get_unmapped_area(addr, len, flags,
 				       mm_ctx_user_psize(&current->mm->context), 0);
@@ -204,6 +104,9 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 					     const unsigned long pgoff,
 					     const unsigned long flags)
 {
+	if (radix_enabled())
+		return generic_get_unmapped_area_topdown(filp, addr0, len, pgoff, flags);
+
 #ifdef CONFIG_PPC_64S_HASH_MMU
 	return slice_get_unmapped_area(addr0, len, flags,
 				       mm_ctx_user_psize(&current->mm->context), 1);
@@ -213,21 +116,6 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 }
 #endif /* HAVE_ARCH_UNMAPPED_AREA */
 
-static void radix__arch_pick_mmap_layout(struct mm_struct *mm,
-					unsigned long random_factor,
-					struct rlimit *rlim_stack)
-{
-#ifdef CONFIG_PPC_RADIX_MMU
-	if (mmap_is_legacy(rlim_stack)) {
-		mm->mmap_base = TASK_UNMAPPED_BASE;
-		mm->get_unmapped_area = radix__arch_get_unmapped_area;
-	} else {
-		mm->mmap_base = mmap_base(random_factor, rlim_stack);
-		mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;
-	}
-#endif
-}
-
 /*
  * This function, called very early during the creation of a new
  * process VM image, sets up which VM layout function to use:
@@ -239,9 +127,6 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
 	if (current->flags & PF_RANDOMIZE)
 		random_factor = arch_mmap_rnd();
 
-	if (radix_enabled())
-		return radix__arch_pick_mmap_layout(mm, random_factor,
-						    rlim_stack);
 	/*
 	 * Fall back to the standard layout if the personality
 	 * bit is set, or if the expected stack growth is unlimited: