criu/mem.c

#include <unistd.h>
#include <stdio.h>
#include <sys/mman.h>
#include <errno.h>
#include <fcntl.h>

#include "cr_options.h"
#include "servicefd.h"
#include "mem.h"
#include "parasite-syscall.h"
#include "parasite.h"
#include "page-pipe.h"
#include "page-xfer.h"
#include "log.h"
#include "kerndat.h"
#include "stats.h"
#include "vma.h"

#include "protobuf.h"
#include "protobuf/pagemap.pb-c.h"

static int task_reset_dirty_track(int pid)
{
	if (!opts.track_mem)
		return 0;

	BUG_ON(!kerndat_has_dirty_track);

	return do_task_reset_dirty_track(pid);
}

int do_task_reset_dirty_track(int pid)
{
	int fd, ret;
	char cmd[] = "4";

	pr_info("Reset %d's dirty tracking\n", pid);

	fd = open_proc_rw(pid, "clear_refs");
	if (fd < 0)
		return -1;

	ret = write(fd, cmd, sizeof(cmd));
	close(fd);

	if (ret < 0) {
		pr_warn("Can't reset %d's dirty memory tracker (%d)\n", pid, errno);
		return -1;
	}

	pr_info(" ... done\n");
	return 0;
}

unsigned int dump_pages_args_size(struct vm_area_list *vmas)
{
	/*
	 * In the worst case I need one iovec for half of the
	 * pages (e.g. every odd/even)
	 */

	return sizeof(struct parasite_dump_pages_args) +
		vmas->nr * sizeof(struct parasite_vma_entry) +
		(vmas->priv_size + 1) * sizeof(struct iovec) / 2;
}

static inline bool should_dump_page(VmaEntry *vmae, u64 pme)
{
	if (vma_entry_is(vmae, VMA_AREA_VDSO))
		return true;
	/*
	 * Optimisation for private mapping pages, that haven't
	 * yet being COW-ed
	 */
	if (vma_entry_is(vmae, VMA_FILE_PRIVATE) && (pme & PME_FILE))
		return false;
	if (pme & (PME_PRESENT | PME_SWAP))
		return true;

	return false;
}

static inline bool page_in_parent(u64 pme)
{
	/*
	 * If we do memory tracking, but w/o parent images,
	 * then we have to dump all memory
	 */

	return opts.track_mem && opts.img_parent && !(pme & PME_SOFT_DIRTY);
}

/*
 * This routine finds out what memory regions to grab from the
 * dumpee. The iovs generated are then fed into vmsplice to
 * put the memory into the page-pipe's pipe.
 *
 * "Holes" in page-pipe are regions, that should be dumped, but
 * the memory contents is present in the pagent image set.
 */

static int generate_iovs(struct vma_area *vma, int pagemap, struct page_pipe *pp, u64 *map)
{
	unsigned long pfn, nr_to_scan;
	unsigned long pages[2] = {};
	u64 aux;

	aux = vma->vma.start / PAGE_SIZE * sizeof(*map);
	if (lseek(pagemap, aux, SEEK_SET) != aux) {
		pr_perror("Can't rewind pagemap file");
		return -1;
	}

	nr_to_scan = vma_area_len(vma) / PAGE_SIZE;
	aux = nr_to_scan * sizeof(*map);
	if (read(pagemap, map, aux) != aux) {
		pr_perror("Can't read pagemap file");
		return -1;
	}

	for (pfn = 0; pfn < nr_to_scan; pfn++) {
		unsigned long vaddr;
		int ret;

		if (!should_dump_page(&vma->vma, map[pfn]))
			continue;

		vaddr = vma->vma.start + pfn * PAGE_SIZE;

		/*
		 * If we're doing incremental dump (parent images
		 * specified) and page is not soft-dirty -- we dump
		 * hole and expect the parent images to contain this
		 * page. The latter would be checked in page-xfer.
		 */

		if (page_in_parent(map[pfn])) {
			ret = page_pipe_add_hole(pp, vaddr);
			pages[0]++;
		} else {
			ret = page_pipe_add_page(pp, vaddr);
			pages[1]++;
		}

		if (ret)
			return -1;
	}

	cnt_add(CNT_PAGES_SCANNED, nr_to_scan);
	cnt_add(CNT_PAGES_SKIPPED_PARENT, pages[0]);
	cnt_add(CNT_PAGES_WRITTEN, pages[1]);

	pr_info("Pagemap generated: %lu pages %lu holes\n", pages[1], pages[0]);
	return 0;
}

static struct parasite_dump_pages_args *prep_dump_pages_args(struct parasite_ctl *ctl,
		struct vm_area_list *vma_area_list)
{
	struct parasite_dump_pages_args *args;
	struct parasite_vma_entry *p_vma;
	struct vma_area *vma;

	args = parasite_args_s(ctl, dump_pages_args_size(vma_area_list));

	p_vma = pargs_vmas(args);
	args->nr_vmas = 0;

	list_for_each_entry(vma, &vma_area_list->h, list) {
		if (!privately_dump_vma(vma))
			continue;
		if (vma->vma.prot & PROT_READ)
			continue;

		p_vma->start = vma->vma.start;
		p_vma->len = vma_area_len(vma);
		p_vma->prot = vma->vma.prot;

		args->nr_vmas++;
		p_vma++;
	}

	return args;
}

static int __parasite_dump_pages_seized(struct parasite_ctl *ctl,
		struct parasite_dump_pages_args *args,
		struct vm_area_list *vma_area_list,
		struct page_pipe **pp_ret)
{
	u64 *map;
	int pagemap;
	struct page_pipe *pp;
	struct page_pipe_buf *ppb;
	struct vma_area *vma_area;
	int ret = -1;

	pr_info("\n");
	pr_info("Dumping pages (type: %d pid: %d)\n", CR_FD_PAGES, ctl->pid.real);
	pr_info("----------------------------------------\n");

	timing_start(TIME_MEMDUMP);

	pr_debug("   Private vmas %lu/%lu pages\n",
			vma_area_list->longest, vma_area_list->priv_size);

	/*
	 * Step 0 -- prepare
	 */

	map = xmalloc(vma_area_list->longest * sizeof(*map));
	if (!map)
		goto out;

	ret = pagemap = open_proc(ctl->pid.real, "pagemap");
	if (ret < 0)
		goto out_free;

	ret = -1;
	pp = create_page_pipe(vma_area_list->priv_size / 2, pargs_iovs(args));
	if (!pp)
		goto out_close;

	/*
	 * Step 1 -- generate the pagemap
	 */

	list_for_each_entry(vma_area, &vma_area_list->h, list) {
		if (!privately_dump_vma(vma_area))
			continue;

		ret = generate_iovs(vma_area, pagemap, pp, map);
		if (ret < 0)
			goto out_pp;
	}

	debug_show_page_pipe(pp);

	/*
	 * Step 2 -- grab pages into page-pipe
	 */

	args->off = 0;
	list_for_each_entry(ppb, &pp->bufs, l) {
		args->nr_segs = ppb->nr_segs;
		args->nr_pages = ppb->pages_in;
		pr_debug("PPB: %d pages %d segs %u pipe %d off\n",
				args->nr_pages, args->nr_segs, ppb->pipe_size, args->off);

		ret = __parasite_execute_daemon(PARASITE_CMD_DUMPPAGES, ctl);
		if (ret < 0)
			goto out_pp;
		ret = parasite_send_fd(ctl, ppb->p[1]);
		if (ret)
			goto out_pp;

		ret = __parasite_wait_daemon_ack(PARASITE_CMD_DUMPPAGES, ctl);
		if (ret < 0)
			goto out_pp;

		args->off += args->nr_segs;
	}

	timing_stop(TIME_MEMDUMP);

	/*
	 * Step 3 -- write pages into image (or delay writing for
	 *           pre-dump action (see pre_dump_one_task)
	 */

	if (pp_ret)
		*pp_ret = pp;
	else {
		struct page_xfer xfer;

		timing_start(TIME_MEMWRITE);
		ret = open_page_xfer(&xfer, CR_FD_PAGEMAP, ctl->pid.virt);
		if (ret < 0)
			goto out_pp;

		ret = page_xfer_dump_pages(&xfer, pp, 0);
		if (ret < 0)
			goto out_pp;

		xfer.close(&xfer);
		timing_stop(TIME_MEMWRITE);
	}

	/*
	 * Step 4 -- clean up
	 */

	ret = task_reset_dirty_track(ctl->pid.real);
out_pp:
	if (ret || !pp_ret)
		destroy_page_pipe(pp);
out_close:
	close(pagemap);
out_free:
	xfree(map);
out:
	pr_info("----------------------------------------\n");
	return ret;
}

int parasite_dump_pages_seized(struct parasite_ctl *ctl,
		struct vm_area_list *vma_area_list, struct page_pipe **pp)
{
	int ret;
	struct parasite_dump_pages_args *pargs;

	pargs = prep_dump_pages_args(ctl, vma_area_list);

	/*
	 * Add PROT_READ protection for all VMAs we're about to
	 * dump if they don't have one. Otherwise we'll not be
	 * able to read the memory contents.
	 *
	 * Afterwards -- reprotect memory back.
	 */

	pargs->add_prot = PROT_READ;
	ret = parasite_execute_daemon(PARASITE_CMD_MPROTECT_VMAS, ctl);
	if (ret) {
		pr_err("Can't dump unprotect vmas with parasite\n");
		return ret;
	}

	ret = __parasite_dump_pages_seized(ctl, pargs, vma_area_list, pp);
	if (ret)
		pr_err("Can't dump page with parasite\n");

	pargs->add_prot = 0;
	if (parasite_execute_daemon(PARASITE_CMD_MPROTECT_VMAS, ctl)) {
		pr_err("Can't rollback unprotected vmas with parasite\n");
		ret = -1;
	}

	return ret;
}