expose vfs in emscripten and impl read syscall, feature flag

Cargo.toml

@@ -39,7 +39,7 @@ glob = "0.2.11"
 
 [features]
 default = ["fast-tests"]
-
+vfs = ["wasmer-runtime-abi", "wasmer-runtime-core/vfs", "wasmer-emscripten/vfs",  "wasmer-clif-backend/vfs"]
 debug = ["wasmer-clif-backend/debug", "wasmer-runtime-core/debug"]
 # This feature will allow cargo test to run much faster
 fast-tests = []

lib/emscripten/Cargo.toml

@@ -10,6 +10,8 @@ build = "build/mod.rs"
 
 [dependencies]
 wasmer-runtime-core = { path = "../runtime-core", version = "0.2.1" }
+wasmer-clif-backend = { path = "../clif-backend", version = "0.2.0" }
+wasmer-runtime-abi = { path = "../runtime-abi", optional = true }
 lazy_static = "1.2.0"
 libc = "0.2.49"
 byteorder = "1"
@@ -19,7 +21,6 @@ time = "0.1.41"
 rand = "0.6"
 
 [dev-dependencies]
-wasmer-clif-backend = { path = "../clif-backend", version = "0.2.0" }
 wabt = "0.7.2"
 
 [target.'cfg(not(windows))'.dev-dependencies]
@@ -30,4 +31,5 @@ glob = "0.2.11"
 
 [features]
 clif = []
-llvm = []
+llvm = []
+vfs = ["wasmer-runtime-core/vfs", "wasmer-clif-backend/vfs", "wasmer-runtime-abi"]

lib/emscripten/emtests/test_vfs.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+int main() {
+    char data[256] = {0};
+    ssize_t fd = open("data.txt", 0);
+    ssize_t result = read((int)fd, &data, 255);
+    printf("content: %s", data);
+    printf("fd: %zd\n", fd);
+    return 0;
+}

lib/emscripten/emtests/test_vfs.md

@@ -0,0 +1,6 @@
+The wasm file `test_vfs.wasm` is generated by compiling the `test_vfs.c` and writing a tar.zst blob with a single file 
+named `data.txt`. 
+
+The program expects to find a file named `data.txt` and reads the contents and the file descriptor. 
+
+The runtime should mount the virtual filesystem and expose the file. 

lib/emscripten/emtests/test_vfs.out

@@ -0,0 +1 @@
+content: wasmer is awesomer

lib/emscripten/src/lib.rs

@@ -54,6 +54,11 @@ pub use self::utils::{
     get_emscripten_table_size, is_emscripten_module,
 };
 
+use std::fs::File;
+use std::io::Write;
+#[cfg(feature = "vfs")]
+use wasmer_runtime_abi::vfs::vfs::VfsBacking;
+
 // TODO: Magic number - how is this calculated?
 const TOTAL_STACK: u32 = 5_242_880;
 // TODO: Magic number - how is this calculated?
@@ -135,6 +140,9 @@ pub struct EmscriptenData<'a> {
     pub dyn_call_viji: Option<Func<'a, (i32, i32, i32, i32, i32)>>,
     pub dyn_call_vijiii: Option<Func<'a, (i32, i32, i32, i32, i32, i32, i32)>>,
     pub dyn_call_vijj: Option<Func<'a, (i32, i32, i32, i32, i32, i32)>>,
+
+    #[cfg(feature = "vfs")]
+    pub vfs: Option<VfsBacking>,
 }
 
 impl<'a> EmscriptenData<'a> {
@@ -231,17 +239,33 @@ impl<'a> EmscriptenData<'a> {
             dyn_call_viji,
             dyn_call_vijiii,
             dyn_call_vijj,
+            #[cfg(feature = "vfs")]
+            vfs: None,
         }
     }
 }
 
 pub fn run_emscripten_instance(
-    _module: &Module,
+    module: &Module,
     instance: &mut Instance,
     path: &str,
     args: Vec<&str>,
 ) -> CallResult<()> {
     let mut data = EmscriptenData::new(instance);
+
+    // Construct a new virtual filesystem and inject it into the emscripten data
+    // This is behind a feature flag for now, but will be default in the future
+    #[cfg(feature = "vfs")]
+    {
+        data.vfs = match module.info().custom_sections.get("wasmer_fs") {
+            Some(bytes) => match VfsBacking::from_tar_zstd_bytes(&bytes[..]) {
+                Ok(vfs_backing) => Some(vfs_backing),
+                Err(_) => None,
+            },
+            None => None,
+        };
+    }
+
     let data_ptr = &mut data as *mut _ as *mut c_void;
     instance.context_mut().data = data_ptr;
 

lib/emscripten/src/syscalls/mod.rs

@@ -29,7 +29,7 @@ use libc::{
     // iovec,
     lseek,
     //    open,
-    read,
+    //    read,
     // readv,
     rmdir,
     // writev,
@@ -40,7 +40,6 @@ use libc::{
 use wasmer_runtime_core::vm::Ctx;
 
 use super::env;
-use std::cell::Cell;
 use std::slice;
 // use std::sys::fd::FileDesc;
 
@@ -67,6 +66,7 @@ pub fn ___syscall1(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) {
 }
 
 /// read
+#[cfg(not(feature = "vfs"))]
 pub fn ___syscall3(ctx: &mut Ctx, which: i32, mut varargs: VarArgs) -> i32 {
     // -> ssize_t
     debug!("emscripten::___syscall3 (read) {}", which);
@@ -75,7 +75,27 @@ pub fn ___syscall3(ctx: &mut Ctx, which: i32, mut varargs: VarArgs) -> i32 {
     let count: i32 = varargs.get(ctx);
     debug!("=> fd: {}, buf_offset: {}, count: {}", fd, buf, count);
     let buf_addr = emscripten_memory_pointer!(ctx.memory(0), buf) as *mut c_void;
-    let ret = unsafe { read(fd, buf_addr, count as _) };
+    let ret = unsafe { libc::read(fd, buf_addr, count as _) };
+    debug!("=> ret: {}", ret);
+    ret as _
+}
+
+/// read
+#[cfg(feature = "vfs")]
+pub fn ___syscall3(ctx: &mut Ctx, which: i32, mut varargs: VarArgs) -> i32 {
+    // -> ssize_t
+    debug!("emscripten::___syscall3 (read - vfs) {}", which);
+    let fd: i32 = varargs.get(ctx);
+    let buf: u32 = varargs.get(ctx);
+    let count: i32 = varargs.get(ctx);
+    debug!("=> fd: {}, buf_offset: {}, count: {}", fd, buf, count);
+    let buf_addr = emscripten_memory_pointer!(ctx.memory(0), buf) as *mut u8;
+    let mut buf_slice = unsafe { slice::from_raw_parts_mut(buf_addr, count as _) };
+    let emscripten_data = get_emscripten_data(ctx);
+    let ret = match &mut emscripten_data.vfs {
+        Some(vfs) => vfs.read_file(fd as _, &mut buf_slice).unwrap(),
+        None => 0,
+    };
     debug!("=> ret: {}", ret);
     ret as _
 }
@@ -91,6 +111,23 @@ pub fn ___syscall4(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) -> c_int {
     unsafe { write(fd, buf_addr, count as _) as i32 }
 }
 
+/// open
+#[cfg(feature = "vfs")]
+pub fn ___syscall5(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) -> c_int {
+    debug!("emscripten::___syscall5 (open vfs) {}", which);
+    let pathname: u32 = varargs.get(ctx);
+    let pathname_addr = emscripten_memory_pointer!(ctx.memory(0), pathname) as *const i8;
+    let path_str = unsafe { std::ffi::CStr::from_ptr(pathname_addr).to_str().unwrap() };
+    let emscripten_data = get_emscripten_data(ctx);
+    let fd = if let Some(vfs) = &mut emscripten_data.vfs {
+        vfs.open_file(path_str).unwrap_or(-1)
+    } else {
+        -1
+    };
+    debug!("=> fd: {}", fd);
+    return fd as _;
+}
+
 /// close
 pub fn ___syscall6(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) -> c_int {
     debug!("emscripten::___syscall6 (close) {}", which);
@@ -307,7 +344,7 @@ pub fn ___syscall145(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) -> i32 {
                 as *mut c_void;
             let iov_len = (*guest_iov_addr).iov_len as _;
             // debug!("=> iov_addr: {:?}, {:?}", iov_base, iov_len);
-            let curr = read(fd, iov_base, iov_len);
+            let curr = libc::read(fd, iov_base, iov_len);
             if curr < 0 {
                 return -1;
             }

lib/emscripten/src/syscalls/unix.rs

@@ -78,6 +78,7 @@ use libc::SO_NOSIGPIPE;
 const SO_NOSIGPIPE: c_int = 0;
 
 /// open
+#[cfg(not(feature = "vfs"))]
 pub fn ___syscall5(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) -> c_int {
     debug!("emscripten::___syscall5 (open) {}", which);
     let pathname: u32 = varargs.get(ctx);

lib/emscripten/src/syscalls/windows.rs

@@ -1,3 +1,4 @@
+use crate::env::get_emscripten_data;
 use crate::utils::copy_cstr_into_wasm;
 use crate::utils::read_string_from_wasm;
 use crate::varargs::VarArgs;
@@ -15,6 +16,7 @@ use wasmer_runtime_core::vm::Ctx;
 type pid_t = c_int;
 
 /// open
+#[cfg(not(feature = "vfs"))]
 pub fn ___syscall5(ctx: &mut Ctx, which: c_int, mut varargs: VarArgs) -> c_int {
     debug!("emscripten::___syscall5 (open) {}", which);
     let pathname: u32 = varargs.get(ctx);

lib/emscripten/tests/emtests/mod.rs

@@ -176,6 +176,8 @@ mod test_unary_literal;
 mod test_utf;
 mod test_varargs;
 mod test_varargs_multi;
+#[cfg(feature = "vfs")]
+mod test_vfs;
 mod test_vprintf;
 mod test_vsnprintf;
 mod test_wprintf;

lib/emscripten/tests/emtests/test_vfs.rs

@@ -0,0 +1,9 @@
+#[test]
+fn test_vfs() {
+    assert_emscripten_output!(
+        "../../emtests/test_vfs.wasm",
+        "test_vfs",
+        vec![],
+        "../../emtests/test_vfs.out"
+    );
+}