On Thu, Jun 25, 2015 at 06:49:44PM +0200, Cédric Bosdonnat wrote:
> So far a mount with / as target doesn't change anything: the host / is
> still the one mounted as /. libvirt-sandbox-init-qemu now detects the
> presence of a / target in mounts.cfg and mounts it instead of
> sandbox:root.
> ---
> libvirt-sandbox/libvirt-sandbox-init-qemu.c | 69 ++++++++++++++++++++++++++++-
> 1 file changed, 67 insertions(+), 2 deletions(-)
>
> diff --git a/libvirt-sandbox/libvirt-sandbox-init-qemu.c b/libvirt-sandbox/libvirt-sandbox-init-qemu.c
> index 9acea5f..02fb980 100644
> --- a/libvirt-sandbox/libvirt-sandbox-init-qemu.c
> +++ b/libvirt-sandbox/libvirt-sandbox-init-qemu.c
> @@ -264,6 +264,70 @@ mount_entry(const char *source,
> }
> }
>
> +static void
> +mount_root(const char *path)
> +{
> + int foundRoot = 0;
> +
> + /* Loop over mounts.cfg to see if we have a candidate for / */
> + mount_mkdir(SANDBOXCONFIGDIR, 0755);
> + mount_9pfs("sandbox:config", SANDBOXCONFIGDIR, 0755, 1);
> +
> + FILE *fp = fopen(SANDBOXCONFIGDIR "/mounts.cfg", "r");
> + while (fgets(line, sizeof line, fp) && !foundRoot) {
> + char *source = line;
> + char *target = strchr(source, '\t');
> + *target = '\0';
> + target++;
> + char *type = strchr(target, '\t');
> + *type = '\0';
> + type++;
> + char *opts = strchr(type, '\t');
> + *opts = '\0';
> + opts++;
> + char *tmp = strchr(opts, '\n');
> + *tmp = '\0';
> +
> + if (STREQ(target, "/")) {
> + int needsDev = strncmp(source, "/dev/", 5) == 0;
> +
> + if (debug)
> + fprintf(stderr, "libvirt-sandbox-init-qemu: found root from %s\n",
> + source);
> +
> + /* In this case, we need to have a /dev before the chroot */
> + if (needsDev) {
> + mount_other("/proc", "proc", 0755);
> + mount_other("/dev", "tmpfs", 0755);
Should this be 'devtmpfs' instead of just 'tmpfs' now ?
> + }
> +
> + mount_entry(source, path, type, opts);
> +
> + if (needsDev && umount("/dev") < 0) {
> + fprintf(stderr,
> + "libvirt-sandbox-init-qemu: %s: "
> + "cannot unmount temporary /dev: %s\n",
> + __func__, strerror(errno));
> + exit_poweroff();
> + }
Do we need to unmount the temporary /proc too, to just avoid
polluting /proc/mounts with multiple instances of it
> + foundRoot = 1;
> + }
> + }
> + fclose(fp);
> +
> + if (umount(SANDBOXCONFIGDIR) < 0) {
> + fprintf(stderr,
> + "libvirt-sandbox-init-qemu: %s: "
> + "cannot unmount temporary %s: %s\n",
> + __func__, SANDBOXCONFIGDIR, strerror(errno));
> + exit_poweroff();
> + }
> +
> + /* If we couldn't get a / in the mounts, then use the host one */
> + if (!foundRoot)
> + mount_9pfs("sandbox:root", path, 0755, 1);
> +}
> +
> int
> main(int argc ATTR_UNUSED, char **argv ATTR_UNUSED)
> {
> @@ -308,7 +372,7 @@ main(int argc ATTR_UNUSED, char **argv ATTR_UNUSED)
> if (debug)
> fprintf(stderr, "libvirt-sandbox-init-qemu: mounting new root on /tmproot\n");
>
> - mount_9pfs("sandbox:root", "/tmproot", 0755, 1);
> + mount_root("/tmproot");
>
> /* Note that pivot_root won't work. See the note in
> * Documentation/filesystems/ramfs-rootfs-initramfs.txt
> @@ -412,7 +476,8 @@ main(int argc ATTR_UNUSED, char **argv ATTR_UNUSED)
> fprintf(stderr, "libvirt-sandbox-init-qemu: %s: %s -> %s (%s, %s)\n",
> __func__, source, target, type, opts);
>
> - mount_entry(source, target, type, opts);
> + if (STREQ(target, "/"))
Shouldn't this be inverted, ie STRNEQ instead of STREQ - ie we
need to skip '/'
> + mount_entry(source, target, type, opts);
> }
> fclose(fp);
>
Regards,
Daniel
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