Fix mkdir syscall issue and implement mkdirat

Signed-off-by: David Smith <d7878291@gmail.com>
Message-Id: <20210115133359.119099-1-d7878291@gmail.com>

fs/vfs/main.cc

@@ -833,6 +833,43 @@ mkdir(const char *pathname, mode_t mode)
     return -1;
 }
 
+int mkdirat(int dirfd, const char *pathname, mode_t mode)
+{
+    mode = apply_umask(mode);
+
+	if (pathname[0] == '/' || dirfd == AT_FDCWD) {
+        // Supplied path is either absolute or relative to cwd
+        return mkdir(pathname, mode);
+    }
+
+    // Supplied path is relative to folder specified by dirfd
+    struct file *fp;
+    int error = fget(dirfd, &fp);
+    if (error) {
+        errno = error;
+        return -1;
+    }
+
+    struct vnode *vp = fp->f_dentry->d_vnode;
+    vn_lock(vp);
+
+    std::unique_ptr<char []> up (new char[PATH_MAX]);
+    char *p = up.get();
+
+    /* build absolute path */
+    strlcpy(p, fp->f_dentry->d_mount->m_path, PATH_MAX);
+    strlcat(p, fp->f_dentry->d_path, PATH_MAX);
+    strlcat(p, "/", PATH_MAX);
+    strlcat(p, pathname, PATH_MAX);
+
+    error = mkdir(p, mode);
+
+    vn_unlock(vp);
+    fdrop(fp);
+
+    return error;
+}
+
 TRACEPOINT(trace_vfs_rmdir, "\"%s\"", const char*);
 TRACEPOINT(trace_vfs_rmdir_ret, "");
 TRACEPOINT(trace_vfs_rmdir_err, "%d", int);

libc/syscall_to_function.h

@@ -19,6 +19,8 @@
 #define __OSV_TO_FUNCTION_SYS_writev        writev
 #define __OSV_TO_FUNCTION_SYS_fstatat       fstatat
 #define __OSV_TO_FUNCTION_SYS_unlinkat      unlinkat
+#define __OSV_TO_FUNCTION_SYS_mkdir         mkdir
+#define __OSV_TO_FUNCTION_SYS_mkdirat       mkdirat
 
 #undef __syscall
 #define __syscall(sys_number, ...) (__OSV_TO_FUNCTION_##sys_number(__VA_ARGS__) < 0 ? -errno : 0)

linux.cc

@@ -447,6 +447,8 @@ long syscall(long number, ...)
     SYSCALL0(getpid);
     SYSCALL3(set_mempolicy, int, unsigned long *, unsigned long);
     SYSCALL3(sched_setaffinity_syscall, pid_t, unsigned, unsigned long *);
+    SYSCALL2(mkdir, char*, mode_t);
+    SYSCALL3(mkdirat, int, char*, mode_t);
     }
 
     debug_always("syscall(): unimplemented system call %d\n", number);