m68k: mm: Move the pointer table allocator to motorola.c

Only the Motorola MMU makes use of this allocator, it is a waste of
.text to include it for Sun3/ColdFire. Also, this is going to avoid
build issues when we're going to make it more Motorola specific.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Greg Ungerer <gerg@linux-m68k.org>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Greg Ungerer <gerg@linux-m68k.org>
Link: https://lore.kernel.org/r/20200131125403.654652162@infradead.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

1 files changed, 102 insertions, 0 deletions

diff --git a/arch/m68k/mm/motorola.c b/arch/m68k/mm/motorola.c
index be61f35a7432..2102f9397c94 100644
--- a/arch/m68k/mm/motorola.c
+++ b/arch/m68k/mm/motorola.c
@@ -67,6 +67,108 @@ void mmu_page_dtor(void *page)
 	cache_page(page);
 }
 
+/* ++andreas: {get,free}_pointer_table rewritten to use unused fields from
+   struct page instead of separately kmalloced struct.  Stolen from
+   arch/sparc/mm/srmmu.c ... */
+
+typedef struct list_head ptable_desc;
+static LIST_HEAD(ptable_list);
+
+#define PD_PTABLE(page) ((ptable_desc *)&(virt_to_page(page)->lru))
+#define PD_PAGE(ptable) (list_entry(ptable, struct page, lru))
+#define PD_MARKBITS(dp) (*(unsigned char *)&PD_PAGE(dp)->index)
+
+#define PTABLE_SIZE (PTRS_PER_PMD * sizeof(pmd_t))
+
+void __init init_pointer_table(unsigned long ptable)
+{
+	ptable_desc *dp;
+	unsigned long page = ptable & PAGE_MASK;
+	unsigned char mask = 1 << ((ptable - page)/PTABLE_SIZE);
+
+	dp = PD_PTABLE(page);
+	if (!(PD_MARKBITS(dp) & mask)) {
+		PD_MARKBITS(dp) = 0xff;
+		list_add(dp, &ptable_list);
+	}
+
+	PD_MARKBITS(dp) &= ~mask;
+	pr_debug("init_pointer_table: %lx, %x\n", ptable, PD_MARKBITS(dp));
+
+	/* unreserve the page so it's possible to free that page */
+	__ClearPageReserved(PD_PAGE(dp));
+	init_page_count(PD_PAGE(dp));
+
+	return;
+}
+
+pmd_t *get_pointer_table (void)
+{
+	ptable_desc *dp = ptable_list.next;
+	unsigned char mask = PD_MARKBITS (dp);
+	unsigned char tmp;
+	unsigned int off;
+
+	/*
+	 * For a pointer table for a user process address space, a
+	 * table is taken from a page allocated for the purpose.  Each
+	 * page can hold 8 pointer tables.  The page is remapped in
+	 * virtual address space to be noncacheable.
+	 */
+	if (mask == 0) {
+		void *page;
+		ptable_desc *new;
+
+		if (!(page = (void *)get_zeroed_page(GFP_KERNEL)))
+			return NULL;
+
+		mmu_page_ctor(page);
+
+		new = PD_PTABLE(page);
+		PD_MARKBITS(new) = 0xfe;
+		list_add_tail(new, dp);
+
+		return (pmd_t *)page;
+	}
+
+	for (tmp = 1, off = 0; (mask & tmp) == 0; tmp <<= 1, off += PTABLE_SIZE)
+		;
+	PD_MARKBITS(dp) = mask & ~tmp;
+	if (!PD_MARKBITS(dp)) {
+		/* move to end of list */
+		list_move_tail(dp, &ptable_list);
+	}
+	return (pmd_t *) (page_address(PD_PAGE(dp)) + off);
+}
+
+int free_pointer_table (pmd_t *ptable)
+{
+	ptable_desc *dp;
+	unsigned long page = (unsigned long)ptable & PAGE_MASK;
+	unsigned char mask = 1 << (((unsigned long)ptable - page)/PTABLE_SIZE);
+
+	dp = PD_PTABLE(page);
+	if (PD_MARKBITS (dp) & mask)
+		panic ("table already free!");
+
+	PD_MARKBITS (dp) |= mask;
+
+	if (PD_MARKBITS(dp) == 0xff) {
+		/* all tables in page are free, free page */
+		list_del(dp);
+		mmu_page_dtor((void *)page);
+		free_page (page);
+		return 1;
+	} else if (ptable_list.next != dp) {
+		/*
+		 * move this descriptor to the front of the list, since
+		 * it has one or more free tables.
+		 */
+		list_move(dp, &ptable_list);
+	}
+	return 0;
+}
+
 /* size of memory already mapped in head.S */
 extern __initdata unsigned long m68k_init_mapped_size;