[CRIU] [PATCH 2/8] dump: Dont read prohibited kernel files

[Cyrill Gorcunov]

From: Pavel Emelyanov <xemul at parallels.com>

In particular, we won't be able to do memory tracking,
zero page detection and vdso fixup (need help from Cyrill
on the latter thing).

Signed-off-by: Pavel Emelyanov <xemul at parallels.com>
---
 kerndat.c | 11 ++++++++---
 mem.c     |  2 --
 vdso.c    | 13 +++++++++++--
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/kerndat.c b/kerndat.c
index b791a8f2b1ec..51d801bef096 100644
--- a/kerndat.c
+++ b/kerndat.c
@@ -222,7 +222,9 @@ int kerndat_get_dirty_track(void)
 	 * was at least once re-set. (this is to be removed in
 	 * a couple of kernel releases)
 	 */
-	do_task_reset_dirty_track(getpid());
+	if (do_task_reset_dirty_track(getpid()) < 0)
+		goto no_dt;
+
 	pm2 = open("/proc/self/pagemap", O_RDONLY);
 	if (pm2 < 0) {
 		pr_perror("Can't open pagemap file");
@@ -244,6 +246,7 @@ int kerndat_get_dirty_track(void)
 		pr_info("Dirty track supported on kernel\n");
 		kdat.has_dirty_track = true;
 	} else {
+no_dt:
 		pr_info("Dirty tracking support is OFF\n");
 		if (opts.track_mem) {
 			pr_err("Tracking memory is not available\n");
@@ -312,8 +315,10 @@ static int init_zero_page_pfn()
 	ret = vaddr_to_pfn((unsigned long)addr, &kdat.zero_page_pfn);
 	munmap(addr, PAGE_SIZE);
 
-	if (kdat.zero_page_pfn == 0)
-		ret = -1;
+	if (ret < 0 || kdat.zero_page_pfn == 0) {
+		pr_info("Zero page detection failed, optimization turns off.\n");
+		ret = 0;
+	}
 
 	return ret;
 }
diff --git a/mem.c b/mem.c
index 989efc3a7d21..4b0d998ba99b 100644
--- a/mem.c
+++ b/mem.c
@@ -251,8 +251,6 @@ static int __parasite_dump_pages_seized(struct parasite_ctl *ctl,
 	pr_info("Dumping pages (type: %d pid: %d)\n", CR_FD_PAGES, ctl->pid.real);
 	pr_info("----------------------------------------\n");
 
-	BUG_ON(kdat.zero_page_pfn == 0);
-
 	timing_start(TIME_MEMDUMP);
 
 	pr_debug("   Private vmas %lu/%lu pages\n",
diff --git a/vdso.c b/vdso.c
index 1524d475cb01..a7cfc8027869 100644
--- a/vdso.c
+++ b/vdso.c
@@ -50,8 +50,14 @@ int parasite_fixup_vdso(struct parasite_ctl *ctl, pid_t pid,
 
 	args = parasite_args(ctl, struct parasite_vdso_vma_entry);
 	fd = open_proc(pid, "pagemap");
-	if (fd < 0)
+	if (fd < 0) {
+		if (errno == EPERM) {
+			pr_info("No VDSO fixup possible :(\n");
+			return 0;
+		}
+
 		return -1;
+	}
 
 	list_for_each_entry(vma, &vma_area_list->h, list) {
 		if (!vma_area_is(vma, VMA_AREA_REGULAR))
@@ -290,5 +296,8 @@ int vdso_init(void)
 {
 	if (vdso_fill_self_symtable(&vdso_sym_rt))
 		return -1;
-	return vaddr_to_pfn(vdso_sym_rt.vma_start, &vdso_pfn);
+	if (vaddr_to_pfn(vdso_sym_rt.vma_start, &vdso_pfn) < 0)
+		pr_info("VDSO detection turned off\n");
+
+	return 0;
 }
-- 
2.4.3