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authorDavid Howells <dhowells@redhat.com>2018-11-01 23:36:32 (GMT)
committerAl Viro <viro@zeniv.linux.org.uk>2019-03-20 22:49:06 (GMT)
commitf1b5618e013af28b3c78daf424436a79674423c0 (patch)
tree7fea6c6bb8ef683b92fcabaa9e3f48ed2ec8eeb0
parentcf3cba4a429be43e5527a3f78859b1bfd9ebc5fb (diff)
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vfs: Add a sample program for the new mount API
Add a sample program to demonstrate fsopen/fsmount/move_mount to mount something. To make it compile on all arches, irrespective of whether or not syscall numbers are assigned, define the syscall number to -1 if it isn't to cause the kernel to return -ENOSYS. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--samples/Kconfig9
-rw-r--r--samples/Makefile2
-rw-r--r--samples/vfs/Makefile (renamed from samples/statx/Makefile)5
-rw-r--r--samples/vfs/test-fsmount.c133
-rw-r--r--samples/vfs/test-statx.c (renamed from samples/statx/test-statx.c)11
5 files changed, 153 insertions, 7 deletions
diff --git a/samples/Kconfig b/samples/Kconfig
index d19754c..30a8942 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -154,10 +154,11 @@ config SAMPLE_ANDROID_BINDERFS
Builds a sample program to illustrate the use of the Android binderfs
filesystem.
-config SAMPLE_STATX
- bool "Build example extended-stat using code"
- depends on BROKEN
+config SAMPLE_VFS
+ bool "Build example programs that use new VFS system calls"
help
- Build example userspace program to use the new extended-stat syscall.
+ Build example userspace programs that use new VFS system calls such
+ as mount API and statx(). Note that this is restricted to the x86
+ arch whilst it accesses system calls that aren't yet in all arches.
endif # SAMPLES
diff --git a/samples/Makefile b/samples/Makefile
index b1142a9..95d71ff 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -3,4 +3,4 @@
obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ livepatch/ \
hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/ \
configfs/ connector/ v4l/ trace_printk/ \
- vfio-mdev/ statx/ qmi/ binderfs/
+ vfio-mdev/ vfs/ qmi/ binderfs/
diff --git a/samples/statx/Makefile b/samples/vfs/Makefile
index 59df7c2..4ac9690 100644
--- a/samples/statx/Makefile
+++ b/samples/vfs/Makefile
@@ -1,7 +1,10 @@
# List of programs to build
-hostprogs-$(CONFIG_SAMPLE_STATX) := test-statx
+hostprogs-$(CONFIG_SAMPLE_VFS) := \
+ test-fsmount \
+ test-statx
# Tell kbuild to always build the programs
always := $(hostprogs-y)
+HOSTCFLAGS_test-fsmount.o += -I$(objtree)/usr/include
HOSTCFLAGS_test-statx.o += -I$(objtree)/usr/include
diff --git a/samples/vfs/test-fsmount.c b/samples/vfs/test-fsmount.c
new file mode 100644
index 0000000..266d72b
--- /dev/null
+++ b/samples/vfs/test-fsmount.c
@@ -0,0 +1,133 @@
+/* fd-based mount test.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <linux/mount.h>
+#include <linux/unistd.h>
+
+#define E(x) do { if ((x) == -1) { perror(#x); exit(1); } } while(0)
+
+static void check_messages(int fd)
+{
+ char buf[4096];
+ int err, n;
+
+ err = errno;
+
+ for (;;) {
+ n = read(fd, buf, sizeof(buf));
+ if (n < 0)
+ break;
+ n -= 2;
+
+ switch (buf[0]) {
+ case 'e':
+ fprintf(stderr, "Error: %*.*s\n", n, n, buf + 2);
+ break;
+ case 'w':
+ fprintf(stderr, "Warning: %*.*s\n", n, n, buf + 2);
+ break;
+ case 'i':
+ fprintf(stderr, "Info: %*.*s\n", n, n, buf + 2);
+ break;
+ }
+ }
+
+ errno = err;
+}
+
+static __attribute__((noreturn))
+void mount_error(int fd, const char *s)
+{
+ check_messages(fd);
+ fprintf(stderr, "%s: %m\n", s);
+ exit(1);
+}
+
+/* Hope -1 isn't a syscall */
+#ifndef __NR_fsopen
+#define __NR_fsopen -1
+#endif
+#ifndef __NR_fsmount
+#define __NR_fsmount -1
+#endif
+#ifndef __NR_fsconfig
+#define __NR_fsconfig -1
+#endif
+#ifndef __NR_move_mount
+#define __NR_move_mount -1
+#endif
+
+
+static inline int fsopen(const char *fs_name, unsigned int flags)
+{
+ return syscall(__NR_fsopen, fs_name, flags);
+}
+
+static inline int fsmount(int fsfd, unsigned int flags, unsigned int ms_flags)
+{
+ return syscall(__NR_fsmount, fsfd, flags, ms_flags);
+}
+
+static inline int fsconfig(int fsfd, unsigned int cmd,
+ const char *key, const void *val, int aux)
+{
+ return syscall(__NR_fsconfig, fsfd, cmd, key, val, aux);
+}
+
+static inline int move_mount(int from_dfd, const char *from_pathname,
+ int to_dfd, const char *to_pathname,
+ unsigned int flags)
+{
+ return syscall(__NR_move_mount,
+ from_dfd, from_pathname,
+ to_dfd, to_pathname, flags);
+}
+
+#define E_fsconfig(fd, cmd, key, val, aux) \
+ do { \
+ if (fsconfig(fd, cmd, key, val, aux) == -1) \
+ mount_error(fd, key ?: "create"); \
+ } while (0)
+
+int main(int argc, char *argv[])
+{
+ int fsfd, mfd;
+
+ /* Mount a publically available AFS filesystem */
+ fsfd = fsopen("afs", 0);
+ if (fsfd == -1) {
+ perror("fsopen");
+ exit(1);
+ }
+
+ E_fsconfig(fsfd, FSCONFIG_SET_STRING, "source", "#grand.central.org:root.cell.", 0);
+ E_fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
+
+ mfd = fsmount(fsfd, 0, MOUNT_ATTR_RDONLY);
+ if (mfd < 0)
+ mount_error(fsfd, "fsmount");
+ E(close(fsfd));
+
+ if (move_mount(mfd, "", AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH) < 0) {
+ perror("move_mount");
+ exit(1);
+ }
+
+ E(close(mfd));
+ exit(0);
+}
diff --git a/samples/statx/test-statx.c b/samples/vfs/test-statx.c
index d4d77b09..e91f918 100644
--- a/samples/statx/test-statx.c
+++ b/samples/vfs/test-statx.c
@@ -25,13 +25,21 @@
#include <sys/types.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
+#define statx foo
+#define statx_timestamp foo_timestamp
#include <sys/stat.h>
+#undef statx
+#undef statx_timestamp
#define AT_STATX_SYNC_TYPE 0x6000
#define AT_STATX_SYNC_AS_STAT 0x0000
#define AT_STATX_FORCE_SYNC 0x2000
#define AT_STATX_DONT_SYNC 0x4000
+#ifndef __NR_statx
+#define __NR_statx -1
+#endif
+
static __attribute__((unused))
ssize_t statx(int dfd, const char *filename, unsigned flags,
unsigned int mask, struct statx *buffer)
@@ -157,7 +165,8 @@ static void dump_statx(struct statx *stx)
"?dai?c??" /* 7- 0 0x00000000-000000ff */
;
- printf("Attributes: %016llx (", stx->stx_attributes);
+ printf("Attributes: %016llx (",
+ (unsigned long long)stx->stx_attributes);
for (byte = 64 - 8; byte >= 0; byte -= 8) {
bits = stx->stx_attributes >> byte;
mbits = stx->stx_attributes_mask >> byte;