[CRIU] error in VDSO remap

[Cyrill Gorcunov]

On Wed, Jul 15, 2015 at 04:28:46PM +0300, Cyrill Gorcunov wrote:
> On Wed, Jul 15, 2015 at 06:48:53AM -0600, Tycho Andersen wrote:
> > Hy Cyrill,
> > 
> > On Thu, Jun 04, 2015 at 08:09:00PM +0300, Cyrill Gorcunov wrote:
> > > On Thu, Jun 04, 2015 at 10:59:28AM -0600, Tycho Andersen wrote:
> > > > Hi Cyrill,
> > > > > 
> > > > > Could you please give the patch a shot?
> > > > 
> > > > No luck, now I'm getting:
> > > > 
> > > > http://files.tycho.ws/tmp/vdso-crash-after-patch.tar.gz
> > > 
> > > Thank for testing! Will ping if I get some idea.
> > 
> > I'm still hitting this, any ideas?
> 
> Nope yet. Gonna take a look, thanks for reminder (alsmost forgot about it).

Could you please run the patch attached and once fail happen -- send me
both (images and logs) please.

	Cyrill
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>From 0f97e02996f5919f6bac485b2eff5774eb5f0e00 Mon Sep 17 00:00:00 2001
From: Cyrill Gorcunov <gorcunov at openvz.org>
Date: Thu, 16 Jul 2015 11:09:31 +0300
Subject: [PATCH] vdso: debug -- show memory map on remap failure

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 arch/x86/vdso-pie.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/arch/x86/vdso-pie.c b/arch/x86/vdso-pie.c
index 5330531c7623..2d878fabff0b 100644
--- a/arch/x86/vdso-pie.c
+++ b/arch/x86/vdso-pie.c
@@ -248,6 +248,29 @@ err_oob:
 	return -EFAULT;
 }
 
+static void vdso_debug_show_self_maps(void)
+{
+	int fd = sys_open("/proc/self/maps", O_RDONLY, 0);
+	if (fd >= 0) {
+		char buf[128];
+		long len, i, pid = sys_getpid();
+
+		do {
+			len = sys_read(fd, buf, sizeof(buf));
+			if (len > 0) {
+				for (i = 0; i < len; i++) {
+					if (buf[i] != '\n')
+						continue;
+					buf[i] = '\0';
+					sys_lseek(fd, -(len - i - 1), SEEK_CUR);
+					break;
+				}
+				pr_debug("cm: %i: %s\n", (int)pid, buf);
+			}
+		} while (len > 0);
+	}
+}
+
 static int vdso_remap(char *who, unsigned long from, unsigned long to, size_t size)
 {
 	unsigned long addr;
@@ -256,8 +279,8 @@ static int vdso_remap(char *who, unsigned long from, unsigned long to, size_t si
 
 	addr = sys_mremap(from, size, size, MREMAP_MAYMOVE | MREMAP_FIXED, to);
 	if (addr != to) {
-		pr_err("Unable to remap %lx -> %lx %lx\n",
-		       from, to, addr);
+		pr_err("Unable to remap %lx -> %lx %lx\n", from, to, addr);
+		vdso_debug_show_self_maps();
 		return -1;
 	}
 
-- 
2.4.3