Support running WASM+WASI binaries via the wasmi interpreter (#472)

* See `applications/wasm` for examples on how to run WASM binaries.

* Key components and details:
    * `kernel/wasm_interpreter` is the main interface between `wasmi` and the rest of Theseus.
    * `applications/wasm` is the user frontend for invoking a WASM binary, which allows specifying access to directories, preopening files, and passing arguments to the WASM application.
    * Basic WASI system calls are supported.
    *  WASM binaries are currently located in `extra_files/`, as are some test/demo files that are used by those WASM binaries.

Author: vikrammullick

.gitignore

@@ -27,6 +27,7 @@ github_pages/doc/
 *.idea/
 *.vscode/
 *.code-workspace
+*.swp
 
 # log files
 *.pcap

Cargo.lock

@@ -132,7 +132,7 @@ iso: $(iso)
 
 
 ### This target builds an .iso OS image from all of the compiled crates.
-$(iso): clean-old-build build
+$(iso): clean-old-build build extra_files
 # after building kernel and application modules, copy the kernel boot image files
 	@mkdir -p $(GRUB_ISOFILES)/boot/grub
 	@cp $(nano_core_binary) $(GRUB_ISOFILES)/boot/kernel.bin

Makefile

@@ -0,0 +1,24 @@
+[package]
+name = "wasm"
+version = "0.1.0"
+authors = ["Vikram Mullick <vikram1.mullick@gmail.com>"]
+edition = "2018"
+description = "Application for running WASI-compliant WebAssembly binaries from Theseus command line"
+
+[dependencies]
+getopts = "0.2.21"
+
+[dependencies.app_io]
+path = "../../kernel/app_io"
+
+[dependencies.task]
+path = "../../kernel/task"
+
+[dependencies.path]
+path = "../../kernel/path"
+
+[dependencies.fs_node]
+ path = "../../kernel/fs_node"
+
+[dependencies.wasi_interpreter]
+path = "../../kernel/wasi_interpreter"

applications/wasm/Cargo.toml

@@ -0,0 +1,150 @@
+//! Application for running WASI-compliant WebAssembly binaries from Theseus command line.
+//!
+//! USAGE:
+//!     wasm [option]... WASM_BINARY_PATH [arg]...
+//!
+//! EXAMPLES:
+//!
+//! Running a WebAssembly Binary:
+//!     wasm example.wasm
+//!
+//! Preopening Multiple Directories:
+//!     wasm --dir DIR1 --dir DIR2 example.wasm
+//!
+//! Passing Arguments/Flags to WebAssembly Binary:
+//!     wasm --dir . example.wasm ARG1 ARG2 ARG3
+//!
+
+#![no_std]
+
+#[macro_use]
+extern crate alloc;
+#[macro_use]
+extern crate app_io;
+extern crate fs_node;
+extern crate getopts;
+extern crate path;
+extern crate task;
+extern crate wasi_interpreter;
+
+use alloc::{string::String, sync::Arc, vec::Vec};
+use fs_node::FileOrDir;
+use getopts::{Options, ParsingStyle};
+use path::Path;
+
+pub fn main(args: Vec<String>) -> isize {
+    // Parse command line options.
+    let mut opts = Options::new();
+
+    // StopAtFirstFree allows arguments to be passed to WebAssembly program.
+    opts.parsing_style(ParsingStyle::StopAtFirstFree);
+
+    opts.optmulti("d", "dir", "directories to grant file system access", "DIR");
+    opts.optflag("h", "help", "print this help menu");
+
+    let matches = match opts.parse(&args) {
+        Ok(m) => m,
+        Err(_f) => {
+            println!("{}", _f);
+            print_usage(opts);
+            return -1;
+        }
+    };
+
+    if matches.opt_present("h") {
+        print_usage(opts);
+        return 0;
+    }
+
+    let preopened_dirs: Vec<String> = matches.opt_strs("d");
+
+    // Get current working directory.
+    let curr_wr = Arc::clone(
+        &task::get_my_current_task()
+            .unwrap()
+            .get_env()
+            .lock()
+            .working_dir,
+    );
+
+    // Verify passed preopened directories are real directories.
+    for dir in preopened_dirs.iter() {
+        let dir_path = Path::new(dir.clone());
+
+        match dir_path.get(&curr_wr) {
+            Some(file_dir_enum) => match file_dir_enum {
+                FileOrDir::Dir(_) => {}
+                FileOrDir::File(file) => {
+                    println!("{:?} is a file.", file.lock().get_name());
+                    return -1;
+                }
+            },
+            _ => {
+                println!("Couldn't find dir at path '{}'", dir_path);
+                return -1;
+            }
+        };
+    }
+
+    let args: Vec<String> = matches.free;
+
+    // Verify that arguments is non-empty.
+    if args.is_empty() {
+        println!("No WebAssembly path specified.");
+        print_usage(opts);
+        return -1;
+    }
+
+    let wasm_binary_path = Path::new(args[0].clone());
+
+    // Parse inputted WebAssembly binary path into byte array.
+    let wasm_binary: Vec<u8> = match wasm_binary_path.get(&curr_wr) {
+        Some(file_dir_enum) => match file_dir_enum {
+            FileOrDir::Dir(directory) => {
+                println!("{:?} is a directory.", directory.lock().get_name());
+                return -1;
+            }
+            FileOrDir::File(file) => {
+                let file_locked = file.lock();
+                let file_size = file_locked.size();
+                let mut wasm_binary_as_bytes = vec![0; file_size];
+
+                let _num_bytes_read = match file_locked.read(&mut wasm_binary_as_bytes, 0) {
+                    Ok(num) => num,
+                    Err(e) => {
+                        println!("Failed to read {:?}, error {:?}", file_locked.get_name(), e);
+                        return -1;
+                    }
+                };
+                wasm_binary_as_bytes
+            }
+        },
+        _ => {
+            println!("Couldn't find file at path '{}'", wasm_binary_path);
+            return -1;
+        }
+    };
+
+    // Execute wasm binary.
+    wasi_interpreter::execute_binary(wasm_binary, args, preopened_dirs);
+
+    0
+}
+
+fn print_usage(opts: Options) {
+    println!("{}", opts.usage(USAGE));
+}
+
+const USAGE: &'static str = "USAGE:
+    wasm [option]... WASM_BINARY_PATH [arg]...
+
+EXAMPLES:
+
+Running a WebAssembly Binary:
+    wasm example.wasm
+
+Preopening Multiple Directories:
+    wasm --dir DIR1 --dir DIR2 example.wasm
+
+Passing Arguments/Flags to WebAssembly Binary:
+    wasm --dir . example.wasm ARG1 ARG2 ARG3";

applications/wasm/src/lib.rs

@@ -0,0 +1,21 @@
+It is a period of civil war.
+Rebel spaceships, striking
+from a hidden base, have won
+their first victory against
+the evil Galactic Empire.
+
+During the battle, Rebel
+spies managed to steal secret
+plans to the Empire's
+ultimate weapon, the DEATH
+STAR, an armored space
+station with enough power to
+destroy an entire planet.
+
+Pursued by the Empire's
+sinister agents, Princess
+Leia races home aboard her
+starship, custodian of the
+stolen plans that can save
+her people and restore
+freedom to the galaxy....

extra_files/test_files/text/a_new_hope.txt

@@ -0,0 +1,19 @@
+There is unrest in the Galactic
+Senate. Several thousand solar
+systems have declared their
+intentions to leave the Republic.
+
+This separatist movement,
+under the leadership of the
+mysterious Count Dooku, has
+made it difficult for the limited
+number of Jedi Knights to maintain
+peace and order in the galaxy.
+
+Senator Amidala, the former
+Queen of Naboo, is returning
+to the Galactic Senate to vote
+on the critical issue of creating
+an ARMY OF THE REPUBLIC
+to assist the overwhelmed
+Jedi....

extra_files/test_files/text/attack_of_the_clones.txt

@@ -0,0 +1,20 @@
+Luke Skywalker has returned to
+his home planet of Tatooine in
+an attempt to rescue his
+friend Han Solo from the
+clutches of the vile gangster
+Jabba the Hutt.
+
+Little does Luke know that the
+GALACTIC EMPIRE has secretly
+begun construction on a new
+armored space station even
+more powerful than the first
+dreaded Death Star.
+
+When completed, this ultimate
+weapon will spell certain doom
+for the small band of rebels
+struggling to restore freedom
+to the galaxy...
+