add zeroobj for private anonymous mappings

kernel/Makefile.build

@@ -1,6 +1,7 @@
 IHKDIR=$(IHKBASE)/$(TARGETDIR)
 OBJS = init.o mem.o debug.o mikc.o listeners.o ap.o syscall.o cls.o host.o
 OBJS += process.o copy.o waitq.o futex.o timer.o plist.o fileobj.o shmobj.o
+OBJS += zeroobj.o
 DEPSRCS=$(wildcard $(SRC)/*.c)
 
 CFLAGS += -I$(SRC)/include -mcmodel=kernel -D__KERNEL__

kernel/include/memobj.h

@@ -103,5 +103,6 @@ static inline int memobj_has_pager(struct memobj *obj)
 
 int fileobj_create(int fd, struct memobj **objp, int *maxprotp);
 int shmobj_create(struct shmid_ds *ds, struct memobj **objp);
+int zeroobj_create(struct memobj **objp);
 
 #endif /* HEADER_MEMOBJ_H */

kernel/syscall.c

@@ -795,6 +795,13 @@ SYSCALL_DECLARE(mmap)
 			goto out;
 		}
 	}
+	else {
+		error = zeroobj_create(&memobj);
+		if (error) {
+			ekprintf("sys_mmap:zeroobj_create failed. %d\n", error);
+			goto out;
+		}
+	}
 
 	if ((flags & MAP_PRIVATE) && (maxprot & PROT_READ)) {
 		maxprot |= PROT_WRITE;

kernel/zeroobj.c

@@ -0,0 +1,206 @@
+/**
+ * \file zeroobj.c
+ *  License details are found in the file LICENSE.
+ * \brief
+ *  read-only zeroed page object
+ * \author Gou Nakamura  <go.nakamura.yw@hitachi-solutions.com>
+ */
+/*
+ * HISTORY:
+ */
+
+#include <ihk/atomic.h>
+#include <ihk/debug.h>
+#include <ihk/lock.h>
+#include <ihk/mm.h>
+#include <errno.h>
+#include <kmalloc.h>
+#include <list.h>
+#include <memobj.h>
+#include <memory.h>
+#include <page.h>
+#include <string.h>
+
+#define	dkprintf(...)	do { if (0) kprintf(__VA_ARGS__); } while (0)
+#define	ekprintf(...)	kprintf(__VA_ARGS__)
+#define	fkprintf(...)	kprintf(__VA_ARGS__)
+
+struct zeroobj {
+	struct memobj		memobj;		/* must be first */
+	struct list_head	page_list;
+};
+
+static ihk_spinlock_t the_zeroobj_lock = SPIN_LOCK_UNLOCKED;
+static struct zeroobj *the_zeroobj = NULL;	/* singleton */
+
+static memobj_get_page_func_t zeroobj_get_page;
+
+static struct memobj_ops zeroobj_ops = {
+	.get_page =	&zeroobj_get_page,
+};
+
+static struct zeroobj *to_zeroobj(struct memobj *memobj)
+{
+	return (struct zeroobj *)memobj;
+}
+
+static struct memobj *to_memobj(struct zeroobj *zeroobj)
+{
+	return &zeroobj->memobj;
+}
+
+/***********************************************************************
+ * page_list
+ */
+static void page_list_init(struct zeroobj *obj)
+{
+	INIT_LIST_HEAD(&obj->page_list);
+	return;
+}
+
+static void page_list_insert(struct zeroobj *obj, struct page *page)
+{
+	list_add(&page->list, &obj->page_list);
+	return;
+}
+
+static struct page *page_list_first(struct zeroobj *obj)
+{
+	if (list_empty(&obj->page_list)) {
+		return NULL;
+	}
+
+	return list_first_entry(&obj->page_list, struct page, list);
+}
+
+/***********************************************************************
+ * zeroobj
+ */
+static int alloc_zeroobj(void)
+{
+	int error;
+	struct zeroobj *obj = NULL;
+	void *virt = NULL;
+	uintptr_t phys;
+	struct page *page;
+
+	dkprintf("alloc_zeroobj()\n");
+	ihk_mc_spinlock_lock_noirq(&the_zeroobj_lock);
+	if (the_zeroobj) {
+		error = 0;
+		dkprintf("alloc_zeroobj():already. %d\n", error);
+		goto out;
+	}
+
+	obj = kmalloc(sizeof(*obj), IHK_MC_AP_NOWAIT);
+	if (!obj) {
+		error = -ENOMEM;
+		ekprintf("alloc_zeroobj():kmalloc failed. %d\n", error);
+		goto out;
+	}
+
+	memset(obj, 0, sizeof(*obj));
+	obj->memobj.ops = &zeroobj_ops;
+	page_list_init(obj);
+	ihk_mc_spinlock_init(&obj->memobj.lock);
+
+	virt = ihk_mc_alloc_pages(1, IHK_MC_AP_NOWAIT);	/* XXX:NYI:large page */
+	if (!virt) {
+		error = -ENOMEM;
+		ekprintf("alloc_zeroobj():alloc pages failed. %d\n", error);
+		goto out;
+	}
+	phys = virt_to_phys(virt);
+	page = phys_to_page(phys);
+
+	if (page->mode != PM_NONE) {
+		fkprintf("alloc_zeroobj():"
+				"page %p %#lx %d %d %#lx\n",
+				page, page_to_phys(page), page->mode,
+				page->count, page->offset);
+		panic("alloc_zeroobj:dup alloc");
+	}
+
+	memset(virt, 0, PAGE_SIZE);
+	page->mode = PM_MAPPED;
+	page->offset = 0;
+	ihk_atomic_set(&page->count, 1);
+	page_list_insert(obj, page);
+	virt = NULL;
+
+	error = 0;
+	the_zeroobj = obj;
+	obj = NULL;
+
+out:
+	ihk_mc_spinlock_unlock_noirq(&the_zeroobj_lock);
+	if (virt) {
+		ihk_mc_free_pages(virt, 1);
+	}
+	if (obj) {
+		kfree(obj);
+	}
+	dkprintf("alloc_zeroobj():%d %p\n", error, the_zeroobj);
+	return error;
+}
+
+int zeroobj_create(struct memobj **objp)
+{
+	int error;
+
+	dkprintf("zeroobj_create(%p)\n", objp);
+	if (!the_zeroobj) {
+		error = alloc_zeroobj();
+		if (error) {
+			goto out;
+		}
+	}
+
+	error = 0;
+	*objp = to_memobj(the_zeroobj);
+
+out:
+	dkprintf("zeroobj_create(%p):%d %p\n", objp, error, *objp);
+	return error;
+}
+
+static int zeroobj_get_page(struct memobj *memobj, off_t off, int p2align,
+		uintptr_t *physp)
+{
+	int error;
+	struct zeroobj *obj = to_zeroobj(memobj);
+	struct page *page;
+
+	dkprintf("zeroobj_get_page(%p,%#lx,%d,%p)\n",
+			memobj, off, p2align, physp);
+	if (off & ~PAGE_MASK) {
+		error = -EINVAL;
+		ekprintf("zeroobj_get_page(%p,%#lx,%d,%p):invalid argument. %d\n",
+				memobj, off, p2align, physp, error);
+		goto out;
+	}
+	if (p2align != PAGE_P2ALIGN) {		/* XXX:NYI:large pages */
+		error = -ENOMEM;
+		ekprintf("zeroobj_get_page(%p,%#lx,%d,%p):large page. %d\n",
+				memobj, off, p2align, physp, error);
+		goto out;
+	}
+
+	page = page_list_first(obj);
+	if (!page) {
+		error = -ENOMEM;
+		ekprintf("zeroobj_get_page(%p,%#lx,%d,%p):page not found. %d\n",
+				memobj, off, p2align, physp, error);
+		goto out;
+	}
+
+	ihk_atomic_inc(&page->count);
+
+	error = 0;
+	*physp = page_to_phys(page);
+
+out:
+	dkprintf("zeroobj_get_page(%p,%#lx,%d,%p):%d\n",
+			memobj, off, p2align, physp, error);
+	return error;
+}