Mount ramfs at '/dev/shm'

deps/sefs

@@ -1 +1 @@
-Subproject commit bb574e0c0bb0a3034f1f4eb48b1d559fe84d2555
+Subproject commit 6bf6fc267b9712a60477727506ed96a37e5f21b2

src/libos/src/fs/dev_fs/dev_shm.rs

@@ -0,0 +1,41 @@
+use super::*;
+
+#[derive(Debug)]
+pub struct DevShm;
+
+impl INode for DevShm {
+    fn read_at(&self, offset: usize, buf: &mut [u8]) -> vfs::Result<usize> {
+        Err(vfs::FsError::NotFile)
+    }
+
+    fn write_at(&self, offset: usize, buf: &[u8]) -> vfs::Result<usize> {
+        Err(vfs::FsError::NotFile)
+    }
+
+    fn poll(&self) -> vfs::Result<vfs::PollStatus> {
+        Err(vfs::FsError::NotFile)
+    }
+
+    fn metadata(&self) -> vfs::Result<Metadata> {
+        Ok(Metadata {
+            dev: 0,
+            inode: 2,
+            size: 0,
+            blk_size: 0,
+            blocks: 0,
+            atime: Timespec { sec: 0, nsec: 0 },
+            mtime: Timespec { sec: 0, nsec: 0 },
+            ctime: Timespec { sec: 0, nsec: 0 },
+            type_: vfs::FileType::Dir,
+            mode: 0o777,
+            nlinks: 1,
+            uid: 0,
+            gid: 0,
+            rdev: 0,
+        })
+    }
+
+    fn as_any_ref(&self) -> &dyn Any {
+        self
+    }
+}

src/libos/src/fs/dev_fs/mod.rs

@@ -1,19 +1,25 @@
+use super::rootfs::mount_fs_at;
 use super::*;
+
 use rcore_fs::vfs;
 use rcore_fs_devfs::DevFS;
+use rcore_fs_mountfs::MountFS;
+use rcore_fs_ramfs::RamFS;
 
 use self::dev_null::DevNull;
 use self::dev_random::DevRandom;
 use self::dev_sgx::DevSgx;
+use self::dev_shm::DevShm;
 use self::dev_zero::DevZero;
 
 mod dev_null;
 mod dev_random;
 mod dev_sgx;
+mod dev_shm;
 mod dev_zero;
 
 /// API to initialize the DevFS
-pub fn init_devfs() -> Result<Arc<DevFS>> {
+pub fn init_devfs() -> Result<Arc<MountFS>> {
     let devfs = DevFS::new();
     let dev_null = Arc::new(DevNull) as _;
     devfs.add("null", dev_null)?;
@@ -25,6 +31,12 @@ pub fn init_devfs() -> Result<Arc<DevFS>> {
     devfs.add("arandom", Arc::clone(&dev_random))?;
     let dev_sgx = Arc::new(DevSgx) as _;
     devfs.add("sgx", dev_sgx)?;
+    let dev_shm = Arc::new(DevShm) as _;
+    devfs.add("shm", dev_shm)?;
+    let mountable_devfs = MountFS::new(devfs);
+    // Mount the ramfs at '/shm'
+    let ramfs = RamFS::new();
+    mount_fs_at(ramfs, &mountable_devfs.root_inode(), &Path::new("/shm"))?;
     // TODO: Add stdio(stdin, stdout, stderr) into DevFS
-    Ok(devfs)
+    Ok(mountable_devfs)
 }

src/libos/src/fs/rootfs.rs

@@ -123,7 +123,7 @@ pub fn mount_nonroot_fs_according_to(
     Ok(())
 }
 
-fn mount_fs_at(fs: Arc<dyn FileSystem>, parent_inode: &MNode, abs_path: &Path) -> Result<()> {
+pub fn mount_fs_at(fs: Arc<dyn FileSystem>, parent_inode: &MNode, abs_path: &Path) -> Result<()> {
     let mut mount_dir = parent_inode.find(false, ".")?;
     // The first component of abs_path is the RootDir, skip it.
     for dirname in abs_path.iter().skip(1) {

test/device/main.c

@@ -4,7 +4,7 @@
 #include <poll.h>
 #include <unistd.h>
 #include <stdio.h>
-#include "test.h"
+#include "test_fs.h"
 
 // ============================================================================
 // Test utilities
@@ -115,6 +115,34 @@ int test_dev_arandom() {
     return 0;
 }
 
+int test_dev_shm() {
+    struct stat stat_buf;
+    if (stat("/dev/shm", &stat_buf) < 0) {
+        THROW_ERROR("failed to stat /dev/shm");
+    }
+    if (!S_ISDIR(stat_buf.st_mode)) {
+        THROW_ERROR("failed to check if it is dir");
+    }
+
+    char *write_str = "Hello World\n";
+    char *file_path = "/dev/shm/test_read_write.txt";
+    int fd = open(file_path, O_WRONLY | O_CREAT | O_TRUNC, 00666);
+    if (fd < 0) {
+        THROW_ERROR("failed to open a file to write");
+    }
+    if (write(fd, write_str, strlen(write_str)) <= 0) {
+        THROW_ERROR("failed to write");
+    }
+    close(fd);
+    if (fs_check_file_content(file_path, write_str) < 0) {
+        THROW_ERROR("failed to check file content");
+    }
+    if (unlink(file_path) < 0) {
+        THROW_ERROR("failed to unlink the file");
+    }
+    return 0;
+}
+
 // ============================================================================
 // Test suite
 // ============================================================================
@@ -127,6 +155,7 @@ static test_case_t test_cases[] = {
     TEST_CASE(test_dev_urandom_fstat),
     TEST_CASE(test_dev_urandom_poll),
     TEST_CASE(test_dev_arandom),
+    TEST_CASE(test_dev_shm),
 };
 
 int main() {