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criu/mem: dump: note MADV_GUARD pages as VMA_AREA_GUARD VMAs

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Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
This commit is contained in:
Alexander Mikhalitsyn 2025-08-04 10:48:47 +02:00 committed by Radostin Stoyanov
parent f091422ad6
commit 8619ea2711
3 changed files with 87 additions and 0 deletions
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17
criu/cr-dump.c
View File

@ -130,6 +130,23 @@ int collect_mappings(pid_t pid, struct vm_area_list *vma_area_list, dump_filemap
if (ret < 0)
goto err;
/*
* In addition to real process VMAs we should keep an info about
* madvise(MADV_GUARD_INSTALL) pages. While these are not represented
* as a struct vm_area_struct in the kernel, it is convenient to treat
* them as mappings in CRIU and reuse the same VMA images but with only
* VMA_AREA_GUARD flag set.
*
* Also, we don't need to dump them during pre-dump.
*/
if (dump_file) {
ret = collect_madv_guards(pid, vma_area_list);
if (ret < 0) {
pr_err("Collect MADV_GUARD_INSTALL pages (pid: %d) failed with %d\n", pid, ret);
goto err;
}
}
pr_info("Collected, longest area occupies %lu pages\n", vma_area_list->nr_priv_pages_longest);
pr_info_vma_list(&vma_area_list->h);

1
criu/include/mem.h
View File

@ -31,6 +31,7 @@ extern int do_task_reset_dirty_track(int pid);
extern unsigned long dump_pages_args_size(struct vm_area_list *vmas);
extern int parasite_dump_pages_seized(struct pstree_item *item, struct vm_area_list *vma_area_list,
struct mem_dump_ctl *mdc, struct parasite_ctl *ctl);
extern int collect_madv_guards(pid_t pid, struct vm_area_list *vma_area_list);
#define PME_PRESENT (1ULL << 63)
#define PME_SWAP (1ULL << 62)

69
criu/mem.c
View File

@ -1548,3 +1548,72 @@ int prepare_vmas(struct pstree_item *t, struct task_restore_args *ta)
return prepare_vma_ios(t, ta);
}
int collect_madv_guards(pid_t pid, struct vm_area_list *vma_area_list)
{
int pagemap_fd = -1;
struct page_region *regs = NULL;
long regs_len = 0;
int i, ret = -1;
struct pm_scan_arg args = {
.size = sizeof(struct pm_scan_arg),
.flags = 0,
.start = 0,
.end = kdat.task_size,
.walk_end = 0,
.vec_len = 1000, /* this should be enough for most cases */
.max_pages = 0,
.category_mask = PAGE_IS_GUARD,
.return_mask = PAGE_IS_GUARD,
};
if (!kdat.has_pagemap_scan_guard_pages) {
ret = 0;
goto out;
}
pagemap_fd = open_proc(pid, "pagemap");
if (pagemap_fd < 0)
goto out;
regs = xmalloc(args.vec_len * sizeof(struct page_region));
if (!regs)
goto out;
args.vec = (long)regs;
do {
/* start from where we finished the last time */
args.start = args.walk_end;
regs_len = ioctl(pagemap_fd, PAGEMAP_SCAN, &args);
if (regs_len == -1) {
pr_perror("PAGEMAP_SCAN");
goto out;
}
for (i = 0; i < regs_len; i++) {
struct vma_area *vma;
BUG_ON(!(regs[i].categories & PAGE_IS_GUARD));
vma = alloc_vma_area();
if (!vma)
goto out;
vma->e->start = regs[i].start;
vma->e->end = regs[i].end;
vma->e->status = VMA_AREA_GUARD;
list_add_tail(&vma->list, &vma_area_list->h);
vma_area_list->nr++;
}
} while (args.walk_end != kdat.task_size);
ret = 0;
out:
xfree(regs);
if (pagemap_fd >= 0)
close(pagemap_fd);
return ret;
}