From 7fe21e06c16e54a8f12cb122f4ad8f12ec5492b1 Mon Sep 17 00:00:00 2001
From: Brett Gordon <beretta42@gmail.com>
Date: Tue, 28 Feb 2017 15:03:06 -0500
Subject: [PATCH] bank16k: add swapping

---
 Kernel/bank16k.c        | 51 +++++++++++++++++++++++++++++++++++++++--
 Kernel/include/kernel.h |  4 ++++
 Kernel/swap.c           | 24 +++++++++++--------
 3 files changed, 68 insertions(+), 11 deletions(-)

diff --git a/Kernel/bank16k.c b/Kernel/bank16k.c
index 799ae8f0..2642b476 100644
--- a/Kernel/bank16k.c
+++ b/Kernel/bank16k.c
@@ -79,12 +79,14 @@ static int maps_needed(uint16_t top)
  *
  *	Use p-> not udata. The udata is not yet swapped in!
  */
-int pagemap_alloc(ptptr p)
+static int pagemap_alloc2(ptptr p, uint8_t c)
 {
 	uint8_t *ptr = (uint8_t *) & p->p_page;
 	int needed = maps_needed(p->p_top);
 	int i;
 
+	if (c)
+		needed--;
 #ifdef SWAPDEV
 	/* Throw our toys out of our pram until we have enough room */
 	while (needed > pfptr)
@@ -99,13 +101,19 @@ int pagemap_alloc(ptptr p)
 	for (i = 0; i < needed; i++)
 		ptr[i] = pfree[--pfptr];
 
+	if (!c)
+		c = ptr[i - 1];
 	while (i < 4) {
-		ptr[i] = ptr[i - 1];
+		ptr[i] = c;
 		i++;
 	}
 	return 0;
 }
 
+int pagemap_alloc( ptptr p ){
+	return pagemap_alloc2(p, 0);
+}
+
 /*
  *	Reallocate the maps for a process
  */
@@ -168,6 +176,45 @@ usize_t pagemap_mem_used(void)
 
 #ifdef SWAPDEV
 
+/* Returns a page with common copied to it
+   used by swapping 16k platforms to procure a common page.
+   platforms will have to provide a void copy_common(uint8_t page)
+   that copies the current common page to the specified page.
+*/
+
+uint8_t get_common()
+{
+	ptptr p = NULL;
+	/* if current context is dead, then reuse it's common */
+	if (udata.u_ptab->p_status == P_ZOMBIE ||
+	    udata.u_ptab->p_status == P_EMPTY){
+		return pfree[--pfptr];
+	}
+	/* otherwise get alloc a page and copy common to it */
+	if (pfptr){
+		int ret = pfree[--pfptr];
+		copy_common(ret);
+		return ret;
+	}
+	/* No free pages so swap something out */
+	/* and return it's common */
+	swapneeded(p, 0);
+	return pfree[--pfptr];
+}
+
+/* Finish swapping in rest of task p, using page as it's common
+   - called from swapping 16k platforms to finish the swapping
+   processes, after starting it with get_common()
+
+*/
+void swap_finish(uint8_t page, ptptr p)
+{
+	uint16_t map = p->p_page2;
+	pagemap_alloc2(p, page);
+	swapper2(p, map);
+}
+
+
 /*
  *	Swap out the memory of a process to make room
  *	for something else. For bank16k do this as four operations
diff --git a/Kernel/include/kernel.h b/Kernel/include/kernel.h
index 5cc48273..e0002a5c 100644
--- a/Kernel/include/kernel.h
+++ b/Kernel/include/kernel.h
@@ -873,6 +873,9 @@ extern void swapmap_add(uint8_t swap);
 extern int swapmap_alloc(void);
 extern ptptr swapneeded(ptptr p, int selfok);
 extern void swapper(ptptr p);
+extern void swapper2(ptptr p, uint16_t map);
+extern uint8_t get_common();
+extern void swap_finish(uint8_t page, ptptr p);
 /* These two are provided by the bank code selected for the port */
 extern int swapout(ptptr p);
 extern void swapin(ptptr p, uint16_t map);
@@ -894,6 +897,7 @@ extern void inittod(void);
 /* provided by architecture or helpers */
 extern void device_init(void);	/* provided by platform */
 extern void pagemap_init(void);
+extern void copy_common(uint8_t page);
 extern void pagemap_add(uint8_t page);	/* FIXME: may need a page type for big boxes */
 extern void pagemap_free(ptptr p);
 extern int pagemap_alloc(ptptr p);
diff --git a/Kernel/swap.c b/Kernel/swap.c
index c8339b89..ef619358 100644
--- a/Kernel/swap.c
+++ b/Kernel/swap.c
@@ -133,16 +133,8 @@ ptptr swapneeded(ptptr p, int notself)
 	return n;
 }
 
-/*
- *	Called from switchin when we discover that we want to run
- *	a swapped process. We let pagemap_alloc cause any needed swap
- *	out of idle processes.
- */
-void swapper(ptptr p)
+void swapper2(ptptr p, uint16_t map)
 {
-        uint16_t map = p->p_page2;
-	pagemap_alloc(p);	/* May cause a swapout. May also destroy
-                                   the old value of p->page2 */
 #ifdef DEBUG
 	kprintf("Swapping in %p (page %d), utab.ptab %p\n", p, p->p_page,
 		udata.u_ptab);
@@ -154,4 +146,18 @@ void swapper(ptptr p)
 		p, p->p_page, udata.u_ptab);
 #endif
 }
+
+/*
+ *	Called from switchin when we discover that we want to run
+ *	a swapped process. We let pagemap_alloc cause any needed swap
+ *	out of idle processes.
+ */
+void swapper(ptptr p)
+{
+        uint16_t map = p->p_page2;
+	pagemap_alloc(p);	/* May cause a swapout. May also destroy
+                                   the old value of p->page2 */
+	return swapper2(p, map);
+}
+
 #endif
-- 
2.34.1