Create directory for mount target provided in configuration file

kernel/enter.c

@@ -38,6 +38,7 @@
 #include <myst/procfs.h>
 #include <myst/pubkey.h>
 #include <myst/ramfs.h>
+#include <myst/realpath.h>
 #include <myst/signal.h>
 #include <myst/stack.h>
 #include <myst/strings.h>
@@ -71,6 +72,67 @@ long myst_tcall(long n, long params[6])
     return ret;
 }
 
+/**
+ * Create target directory if do not exist
+ * Then call mount syscall
+ */
+static int _create_and_mount(
+    const char* source,
+    const char* target,
+    const char* fs_type,
+    unsigned long mountflags,
+    const void* data,
+    bool is_auto)
+{
+    int ret = 0;
+    struct locals
+    {
+        myst_path_t normalized_target;
+        myst_path_t suffix;
+    };
+    struct locals* locals = NULL;
+    myst_fs_t* parent_fs;
+
+    if (!(locals = malloc(sizeof(struct locals))))
+        ERAISE(-ENOMEM);
+
+    ECHECK(myst_realpath(target, &locals->normalized_target));
+
+    // target has to be an absolute path
+    if (locals->normalized_target.buf[0] != '/')
+        ERAISE(-EINVAL);
+
+    ECHECK(myst_mount_resolve(
+        locals->normalized_target.buf, locals->suffix.buf, &parent_fs));
+
+    // check if target exists and is directory
+    // if not, create target directory
+    {
+        struct stat buf;
+        int errornum = (*parent_fs->fs_stat)(
+            parent_fs, locals->normalized_target.buf, &buf);
+
+        if (errornum == -ENOENT)
+            // target do not exist, create directory
+            ECHECK(myst_syscall_mkdir(locals->normalized_target.buf, 0777));
+        else if (errornum == 0 && !S_ISDIR(buf.st_mode))
+            // target exists but is not directory
+            ERAISE(-ENOTDIR);
+        else
+            ECHECK(errornum);
+    }
+
+    ret =
+        myst_syscall_mount(source, target, fs_type, mountflags, data, is_auto);
+
+done:
+
+    if (locals)
+        free(locals);
+
+    return ret;
+}
+
 static int _process_mount_configuration(myst_mounts_config_t* mounts)
 {
     size_t i;
@@ -82,13 +144,14 @@ static int _process_mount_configuration(myst_mounts_config_t* mounts)
 
     for (i = 0; i < mounts->mounts_count; i++)
     {
-        ret = myst_syscall_mount(
+        ret = _create_and_mount(
             mounts->mounts[i].source,
             mounts->mounts[i].target,
             mounts->mounts[i].fs_type,
             0,
             NULL,
             true);
+
         if (ret != 0)
         {
             myst_eprintf(

tests/mount/Makefile

@@ -29,22 +29,19 @@ build-extra:
 	$(MKROOTFS) $(SUBBINDIR)/mount rootfs
 	$(MYST) excpio rootfs appdir
 	# Can only mount ramfs that are located INSIDE enclave
-	$(MYST) mkcpio datafs appdir/ramfs
+	$(MYST) mkcpio data appdir/ramfs
 	# Can only mount ext2fs that are located OUTSIDE enclave
-	$(MYST) mkext2 datafs ext2fs
+	$(MYST) mkext2 data ext2fs
 
 	# Make mounting point in rootfs
-	mkdir -p appdir/mnt/datafs
-	mkdir -p appdir/mnt/hostfs
-	mkdir -p appdir/mnt/ramfs
-	mkdir -p appdir/mnt/ext2fs
+	mkdir -p appdir/mnt/
 
 	# Create rootfs
 	sudo chown -R $(USER).$(USER) appdir
 	$(MYST) mkcpio appdir rootfs
 
 tests-hostfs:
-	$(RUNTEST) $(MYST_EXEC) $(OPTS) rootfs /bin/mount hostfs --app-config-path config-hostfs.json --mount $(CURDIR)/datafs=/mnt/hostfs
+	$(RUNTEST) $(MYST_EXEC) $(OPTS) rootfs /bin/mount hostfs --app-config-path config-hostfs.json --mount $(CURDIR)/data=/mnt/hostfs
 
 tests-ramfs:
 	$(RUNTEST) $(MYST_EXEC) $(OPTS) rootfs /bin/mount ramfs --app-config-path config-ramfs.json --mount /ramfs=/mnt/ramfs
@@ -58,4 +55,4 @@ tests: build-extra
 	$(MAKE) tests-ext2fs
 
 gdb:
-	$(MYST_GDB) --args $(MYST_EXEC) $(OPTS) rootfs /bin/mount ext2fs --app-config-path config-ext2fs.json --mount /ext2fs=/mnt/ext2fs
+	$(MYST_GDB) --args $(MYST_EXEC) $(OPTS) rootfs /bin/mount ramfs --app-config-path config-ramfs.json --mount /ramfs=/mnt/ramfs

tests/mount/mount.c

@@ -37,11 +37,17 @@ int validate_file(const char filename[])
     return 0;
 }
 
+// test C mount API
 int test_mount_and_access()
 {
+    const char source[] = "/ramfs";
+    const char target[] = "/mnt/datafs";
     const char filename[] = "/mnt/datafs/myfile";
 
-    if (mount("/ramfs", "/mnt/datafs", "ramfs", 0, NULL) != 0)
+    // create /mnt/datafs
+    assert(mkdir(target, 0777) == 0);
+
+    if (mount(source, target, "ramfs", 0, NULL) != 0)
     {
         printf("errno: %d\n", errno);
         assert(false);
@@ -78,8 +84,10 @@ int main(int argc, const char* argv[])
         return 1;
     }
 
+    // Test C mount API
     test_mount_and_access();
 
+    // Test mount configuration in config.json
     if (0 == strcmp(argv[1], "hostfs"))
     {
         test_access_hostfs();