v1.6.0

- Checks error results to determine if a plugin ran out of fuel, if the
fuel is 0 after we get the error, then we return an out of fuel error
message instead.
- Updates `extism_plugin_error` to check `Plugin::error_msg` regardless
of the kernel's error state

.github/workflows/release.yml

@@ -61,10 +61,10 @@ jobs:
             static-pc-in: 'extism-static.pc.in'
           - os: 'ubuntu'
             target: 'x86_64-unknown-linux-musl'
-            artifact: ''
+            artifact: 'libextism.so'
             static-artifact: 'libextism.a'
             static-dll-artifact: ''
-            pc-in: ''
+            pc-in: 'extism.pc.in'
             static-pc-in: 'extism-static.pc.in'
           - os: 'windows'
             target: 'x86_64-pc-windows-gnu'

README.md

@@ -8,7 +8,7 @@
 
 [![Discord](https://img.shields.io/discord/1011124058408112148?color=%23404eed&label=Community%20Chat&logo=Discord&logoColor=%23404eed)](https://extism.org/discord)
 ![GitHub Org's stars](https://img.shields.io/github/stars/extism)
-![Downloads](https://img.shields.io/crates/d/extism)
+![Downloads](https://img.shields.io/crates/d/extism-manifest)
 ![GitHub License](https://img.shields.io/github/license/extism/extism)
 ![GitHub release (with filter)](https://img.shields.io/github/v/release/extism/extism)
 

convert/Cargo.toml

@@ -13,7 +13,7 @@ description = "Traits to make Rust types usable with Extism"
 anyhow = "1.0.75"
 base64 = "~0.22"
 bytemuck = {version = "1.14.0", optional = true }
-prost = { version = "0.12.0", optional = true }
+prost = { version = "0.13.1", optional = true }
 protobuf = { version = "3.2.0", optional = true }
 rmp-serde = { version = "1.1.2", optional = true }
 serde = "1.0.186"

convert/src/tests.rs

@@ -81,10 +81,10 @@ mod tests {
             c: true,
         };
         let raw = Raw(&x).to_bytes().unwrap();
-        let y = Raw::from_bytes(&raw).unwrap();
+        let y = Raw::from_bytes(raw).unwrap();
         assert_eq!(&x, y.0);
 
-        let y: Result<Raw<[u8; std::mem::size_of::<TestRaw>()]>, Error> = Raw::from_bytes(&raw);
+        let y: Result<Raw<[u8; std::mem::size_of::<TestRaw>()]>, Error> = Raw::from_bytes(raw);
         assert!(y.is_ok());
     }
 }

kernel/src/lib.rs

@@ -546,7 +546,8 @@ pub unsafe fn reset() {
     MemoryRoot::new().reset()
 }
 
-/// Set the error message offset
+/// Set the error message offset, the handle passed to this
+/// function should not be freed after this call
 #[no_mangle]
 pub unsafe fn error_set(h: Handle) {
     let root = MemoryRoot::new();

manifest/src/lib.rs

@@ -279,7 +279,7 @@ pub struct Manifest {
     /// the path on disk to the path it should be available inside the plugin.
     /// For example, `".": "/tmp"` would mount the current directory as `/tmp` inside the module
     #[serde(default)]
-    pub allowed_paths: Option<BTreeMap<PathBuf, PathBuf>>,
+    pub allowed_paths: Option<BTreeMap<String, PathBuf>>,
 
     /// The plugin timeout in milliseconds
     #[serde(default)]
@@ -337,8 +337,7 @@ impl Manifest {
     }
 
     /// Add a path to `allowed_paths`
-    pub fn with_allowed_path(mut self, src: impl AsRef<Path>, dest: impl AsRef<Path>) -> Self {
-        let src = src.as_ref().to_path_buf();
+    pub fn with_allowed_path(mut self, src: String, dest: impl AsRef<Path>) -> Self {
         let dest = dest.as_ref().to_path_buf();
         match &mut self.allowed_paths {
             Some(p) => {
@@ -355,7 +354,7 @@ impl Manifest {
     }
 
     /// Set `allowed_paths`
-    pub fn with_allowed_paths(mut self, paths: impl Iterator<Item = (PathBuf, PathBuf)>) -> Self {
+    pub fn with_allowed_paths(mut self, paths: impl Iterator<Item = (String, PathBuf)>) -> Self {
         self.allowed_paths = Some(paths.collect());
         self
     }

runtime/Cargo.toml

@@ -9,8 +9,9 @@ repository.workspace = true
 version.workspace = true
 
 [dependencies]
-wasmtime = ">= 20.0.0, < 22.0.0"
-wasi-common = ">= 20.0.0, < 22.0.0"
+wasmtime = ">= 20.0.0, < 24.0.0"
+wasi-common = ">= 20.0.0, < 24.0.0"
+wiggle = ">= 20.0.0, < 24.0.0"
 anyhow = "1"
 serde = {version = "1", features = ["derive"]}
 serde_json = "1"
@@ -33,7 +34,7 @@ register-filesystem = [] # enables wasm to be loaded from disk
 http = ["ureq"]          # enables extism_http_request
 
 [build-dependencies]
-cbindgen = { version = "0.26", default-features = false }
+cbindgen = { version = "0.27", default-features = false }
 
 [dev-dependencies]
 criterion = "0.5.1"

runtime/README.md

@@ -12,7 +12,7 @@ To use the `extism` crate, you can add it to your Cargo file:
 
 ```toml
 [dependencies]
-extism = "1.2.0"
+extism = "1.4.1"
 ```
 
 ## Environment variables

runtime/benches/bench.rs

@@ -35,6 +35,21 @@ pub fn create_plugin(c: &mut Criterion) {
     });
 }
 
+pub fn create_plugin_no_cache(c: &mut Criterion) {
+    let mut g = c.benchmark_group("create");
+    g.noise_threshold(1.0);
+    g.significance_level(0.2);
+    g.bench_function("create_plugin_no_cache", |b| {
+        b.iter(|| {
+            let _plugin = PluginBuilder::new(COUNT_VOWELS)
+                .with_cache_disabled()
+                .with_wasi(true)
+                .build()
+                .unwrap();
+        })
+    });
+}
+
 #[derive(Debug, serde::Deserialize, PartialEq)]
 struct Count {
     count: u32,
@@ -251,6 +266,7 @@ criterion_group!(
     reflect_linked,
     basic,
     create_plugin,
+    create_plugin_no_cache,
     count_vowels
 );
 criterion_main!(benches);

runtime/examples/fs.rs

@@ -0,0 +1,33 @@
+use extism::*;
+fn main() {
+    let url = Wasm::file("../wasm/read_write.wasm");
+    let manifest = Manifest::new([url])
+        .with_allowed_path("ro:src/tests/data".to_string(), "/data")
+        .with_config_key("path", "/data/data.txt");
+
+    let mut plugin = PluginBuilder::new(manifest)
+        .with_wasi(true)
+        .build()
+        .unwrap();
+
+    println!("trying to read file: ");
+
+    let res = plugin.call::<&str, &str>("try_read", "").unwrap();
+
+    println!("{:?}", res);
+
+    println!("-----------------------------------------------------");
+
+    println!("trying to write file: ");
+    let line = format!(
+        "Hello World at {:?}\n",
+        std::time::SystemTime::now()
+            .duration_since(std::time::SystemTime::UNIX_EPOCH)
+            .unwrap()
+    );
+    let res2 = plugin.call::<&str, &str>("try_write", &line).unwrap();
+
+    println!("{:?}", res2);
+
+    println!("done!");
+}

runtime/extism.h

@@ -195,6 +195,17 @@ ExtismPlugin *extism_plugin_new(const uint8_t *wasm,
                                 bool with_wasi,
                                 char **errmsg);
 
+/**
+ * Create a new plugin and set the number of instructions a plugin is allowed to execute
+ */
+ExtismPlugin *extism_plugin_new_with_fuel_limit(const uint8_t *wasm,
+                                                ExtismSize wasm_size,
+                                                const ExtismFunction **functions,
+                                                ExtismSize n_functions,
+                                                bool with_wasi,
+                                                uint64_t fuel_limit,
+                                                char **errmsg);
+
 /**
  * Free the error returned by `extism_plugin_new`, errors returned from `extism_plugin_error` don't need to be freed
  */
@@ -302,5 +313,5 @@ bool extism_plugin_reset(ExtismPlugin *plugin);
 const char *extism_version(void);
 
 #ifdef __cplusplus
-} // extern "C"
-#endif // __cplusplus
+}  // extern "C"
+#endif  // __cplusplus

runtime/src/current_plugin.rs

@@ -1,3 +1,5 @@
+use anyhow::Context;
+
 use crate::*;
 
 /// CurrentPlugin stores data that is available to the caller in PDK functions, this should
@@ -160,10 +162,10 @@ impl CurrentPlugin {
     }
 
     pub fn memory_bytes_mut(&mut self, handle: MemoryHandle) -> Result<&mut [u8], Error> {
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(mem) = linker.get(&mut store, EXTISM_ENV_MODULE, "memory") {
+        let (linker, store) = self.linker_and_store();
+        if let Some(mem) = linker.get(&mut *store, EXTISM_ENV_MODULE, "memory") {
             let mem = mem.into_memory().unwrap();
-            let ptr = unsafe { mem.data_ptr(&store).add(handle.offset() as usize) };
+            let ptr = unsafe { mem.data_ptr(&*store).add(handle.offset() as usize) };
             if ptr.is_null() {
                 return Ok(&mut []);
             }
@@ -174,10 +176,10 @@ impl CurrentPlugin {
     }
 
     pub fn memory_bytes(&mut self, handle: MemoryHandle) -> Result<&[u8], Error> {
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(mem) = linker.get(&mut store, EXTISM_ENV_MODULE, "memory") {
+        let (linker, store) = self.linker_and_store();
+        if let Some(mem) = linker.get(&mut *store, EXTISM_ENV_MODULE, "memory") {
             let mem = mem.into_memory().unwrap();
-            let ptr = unsafe { mem.data_ptr(&store).add(handle.offset() as usize) };
+            let ptr = unsafe { mem.data_ptr(&*store).add(handle.offset() as usize) };
             if ptr.is_null() {
                 return Ok(&[]);
             }
@@ -187,20 +189,26 @@ impl CurrentPlugin {
         anyhow::bail!("{} unable to locate extism memory", self.id)
     }
 
-    pub fn host_context<T: Clone + 'static>(&mut self) -> Result<T, Error> {
-        let (linker, mut store) = self.linker_and_store();
-        let Some(Extern::Global(xs)) = linker.get(&mut store, EXTISM_ENV_MODULE, "extism_context")
+    pub fn host_context<T: 'static>(&mut self) -> Result<&mut T, Error> {
+        let (linker, store) = self.linker_and_store();
+        let Some(Extern::Global(xs)) = linker.get(&mut *store, EXTISM_ENV_MODULE, "extism_context")
         else {
             anyhow::bail!("unable to locate an extism kernel global: extism_context",)
         };
 
-        let Val::ExternRef(Some(xs)) = xs.get(&mut store) else {
+        let Val::ExternRef(Some(xs)) = xs.get(&mut *store) else {
             anyhow::bail!("expected extism_context to be an externref value",)
         };
 
-        match xs.data(&mut store)?.downcast_ref::<T>().cloned() {
-            Some(xs) => Ok(xs.clone()),
-            None => anyhow::bail!("could not downcast extism_context",),
+        match xs
+            .data_mut(&mut *store)?
+            .downcast_mut::<Box<dyn std::any::Any + Send + Sync>>()
+        {
+            Some(xs) => match xs.downcast_mut::<T>() {
+                Some(xs) => Ok(xs),
+                None => anyhow::bail!("could not downcast extism_context inner value"),
+            },
+            None => anyhow::bail!("could not downcast extism_context"),
         }
     }
 
@@ -214,9 +222,13 @@ impl CurrentPlugin {
         let (linker, mut store) = self.linker_and_store();
         let output = &mut [Val::I64(0)];
         if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "alloc") {
-            f.into_func()
-                .unwrap()
-                .call(&mut store, &[Val::I64(n as i64)], output)?;
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(n as i64)], output)
+                    .context("failed to allocate extism memory")
+            )?;
         } else {
             anyhow::bail!("{} unable to allocate memory", self.id);
         }
@@ -238,11 +250,15 @@ impl CurrentPlugin {
 
     /// Free a block of Extism plugin memory
     pub fn memory_free(&mut self, handle: MemoryHandle) -> Result<(), Error> {
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "free") {
-            f.into_func()
-                .unwrap()
-                .call(&mut store, &[Val::I64(handle.offset as i64)], &mut [])?;
+        let (linker, store) = self.linker_and_store();
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "free") {
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(handle.offset as i64)], &mut [])
+                    .context("failed to free extism memory")
+            )?;
         } else {
             anyhow::bail!("unable to locate an extism kernel function: free",)
         }
@@ -250,12 +266,16 @@ impl CurrentPlugin {
     }
 
     pub fn memory_length(&mut self, offs: u64) -> Result<u64, Error> {
-        let (linker, mut store) = self.linker_and_store();
+        let (linker, store) = self.linker_and_store();
         let output = &mut [Val::I64(0)];
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "length") {
-            f.into_func()
-                .unwrap()
-                .call(&mut store, &[Val::I64(offs as i64)], output)?;
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "length") {
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(offs as i64)], output)
+                    .context("failed to get length of extism memory handle")
+            )?;
         } else {
             anyhow::bail!("unable to locate an extism kernel function: length",)
         }
@@ -270,12 +290,16 @@ impl CurrentPlugin {
     }
 
     pub fn memory_length_unsafe(&mut self, offs: u64) -> Result<u64, Error> {
-        let (linker, mut store) = self.linker_and_store();
+        let (linker, store) = self.linker_and_store();
         let output = &mut [Val::I64(0)];
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "length_unsafe") {
-            f.into_func()
-                .unwrap()
-                .call(&mut store, &[Val::I64(offs as i64)], output)?;
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "length_unsafe") {
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(offs as i64)], output)
+                    .context("failed to get length of extism memory using length_unsafe")
+            )?;
         } else {
             anyhow::bail!("unable to locate an extism kernel function: length_unsafe",)
         }
@@ -320,9 +344,20 @@ impl CurrentPlugin {
 
             if let Some(a) = &manifest.allowed_paths {
                 for (k, v) in a.iter() {
-                    let file = Box::new(wasi_common::sync::dir::Dir::from_cap_std(
-                        wasi_common::sync::Dir::open_ambient_dir(k, auth)?,
-                    ));
+                    let readonly = k.starts_with("ro:");
+
+                    let dir_path = if readonly { &k[3..] } else { k };
+
+                    let dir = wasi_common::sync::dir::Dir::from_cap_std(
+                        wasi_common::sync::Dir::open_ambient_dir(dir_path, auth)?,
+                    );
+
+                    let file: Box<dyn wasi_common::dir::WasiDir> = if readonly {
+                        Box::new(readonly_dir::ReadOnlyDir::new(dir))
+                    } else {
+                        Box::new(dir)
+                    };
+
                     ctx.push_preopened_dir(file, v)?;
                 }
             }
@@ -340,7 +375,7 @@ impl CurrentPlugin {
 
         let memory_limiter = if let Some(pgs) = available_pages {
             let n = pgs as usize * 65536;
-            Some(crate::current_plugin::MemoryLimiter {
+            Some(MemoryLimiter {
                 max_bytes: n,
                 bytes_left: n,
             })
@@ -403,12 +438,12 @@ impl CurrentPlugin {
     /// Clear the current plugin error
     pub fn clear_error(&mut self) {
         trace!(plugin = self.id.to_string(), "CurrentPlugin::clear_error");
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "error_set") {
+        let (linker, store) = self.linker_and_store();
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "error_set") {
             let res = f
                 .into_func()
                 .unwrap()
-                .call(&mut store, &[Val::I64(0)], &mut []);
+                .call(&mut *store, &[Val::I64(0)], &mut []);
             if let Err(e) = res {
                 error!(
                     plugin = self.id.to_string(),
@@ -439,13 +474,15 @@ impl CurrentPlugin {
     pub fn set_error(&mut self, s: impl AsRef<str>) -> Result<(u64, u64), Error> {
         let s = s.as_ref();
         debug!(plugin = self.id.to_string(), "set error: {:?}", s);
-        let handle = self.current_plugin_mut().memory_new(s)?;
-        let (linker, mut store) = self.linker_and_store();
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "error_set") {
-            f.into_func().unwrap().call(
-                &mut store,
-                &[Val::I64(handle.offset() as i64)],
-                &mut [],
+        let handle = self.memory_new(s)?;
+        let (linker, store) = self.linker_and_store();
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "error_set") {
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[Val::I64(handle.offset() as i64)], &mut [])
+                    .context("failed to set extism error")
             )?;
             Ok((handle.offset(), s.len() as u64))
         } else {
@@ -454,10 +491,13 @@ impl CurrentPlugin {
     }
 
     pub(crate) fn get_error_position(&mut self) -> (u64, u64) {
-        let (linker, mut store) = self.linker_and_store();
+        let (linker, store) = self.linker_and_store();
         let output = &mut [Val::I64(0)];
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "error_get") {
-            if let Err(e) = f.into_func().unwrap().call(&mut store, &[], output) {
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "error_get") {
+            if let Err(e) = catch_out_of_fuel!(
+                &store,
+                f.into_func().unwrap().call(&mut *store, &[], output)
+            ) {
                 error!(
                     plugin = self.id.to_string(),
                     "unable to call extism:host/env::error_get: {:?}", e

runtime/src/function.rs

@@ -279,7 +279,7 @@ impl Function {
 /// For example, the following defines a host function named `add_newline` that takes a
 /// string parameter and returns a string result:
 /// ```rust
-/// extism::host_fn!(add_newline(_user_data: (), a: String) -> String { Ok(a + "\n") });
+/// extism::host_fn!(add_newline(_user_data: (); a: String) -> String { Ok(a + "\n") });
 /// ```
 /// A few things worth noting:
 /// - The function always returns a `Result` that wraps the specified return type

runtime/src/lib.rs

@@ -1,6 +1,17 @@
 // Makes proc-macros able to resolve `::extism` correctly
 extern crate self as extism;
 
+macro_rules! catch_out_of_fuel {
+    ($store: expr, $x:expr) => {{
+        let y = $x;
+        if y.is_err() && $store.get_fuel().is_ok_and(|x| x == 0) {
+            Err(Error::msg("plugin ran out of fuel"))
+        } else {
+            y
+        }
+    }};
+}
+
 pub(crate) use extism_convert::*;
 pub(crate) use std::collections::BTreeMap;
 use std::str::FromStr;
@@ -18,6 +29,7 @@ pub(crate) mod manifest;
 pub(crate) mod pdk;
 mod plugin;
 mod plugin_builder;
+mod readonly_dir;
 mod timer;
 
 /// Extism C API
@@ -77,11 +89,16 @@ pub fn set_log_callback<F: 'static + Clone + Fn(&str)>(
     filter: impl AsRef<str>,
 ) -> Result<(), Error> {
     let filter = filter.as_ref();
-    let cfg = tracing_subscriber::FmtSubscriber::builder().with_env_filter(
-        tracing_subscriber::EnvFilter::builder()
-            .with_default_directive(tracing::Level::ERROR.into())
-            .parse_lossy(filter),
-    );
+    let is_level = tracing::Level::from_str(filter).is_ok();
+    let cfg = tracing_subscriber::FmtSubscriber::builder().with_env_filter({
+        let x = tracing_subscriber::EnvFilter::builder()
+            .with_default_directive(tracing::Level::ERROR.into());
+        if is_level {
+            x.parse_lossy(format!("extism={}", filter))
+        } else {
+            x.parse_lossy(filter)
+        }
+    });
     let w = LogFunction { func };
     cfg.with_ansi(false)
         .with_writer(move || w.clone())

runtime/src/pdk.rs

@@ -301,6 +301,13 @@ pub fn log(
     _output: &mut [Val],
 ) -> Result<(), Error> {
     let data: &mut CurrentPlugin = caller.data_mut();
+
+    // Check if the current log level should be logged
+    let global_log_level = tracing::level_filters::LevelFilter::current();
+    if global_log_level == tracing::level_filters::LevelFilter::OFF || level > global_log_level {
+        return Ok(());
+    }
+
     let offset = args!(input, 0, i64) as u64;
 
     let handle = match data.memory_handle(offset) {
@@ -377,3 +384,44 @@ pub(crate) fn log_error(
 ) -> Result<(), Error> {
     log(tracing::Level::ERROR, caller, input, _output)
 }
+
+/// Write to logs (trace)
+/// Params: i64 (offset)
+/// Returns: none
+pub(crate) fn log_trace(
+    caller: Caller<CurrentPlugin>,
+    input: &[Val],
+    _output: &mut [Val],
+) -> Result<(), Error> {
+    log(tracing::Level::TRACE, caller, input, _output)
+}
+
+/// Get the log level
+/// Params: none
+/// Returns: i32 (log level)
+pub(crate) fn get_log_level(
+    mut _caller: Caller<CurrentPlugin>,
+    _input: &[Val],
+    output: &mut [Val],
+) -> Result<(), Error> {
+    let level = tracing::level_filters::LevelFilter::current();
+    if level == tracing::level_filters::LevelFilter::OFF {
+        output[0] = Val::I32(i32::MAX)
+    } else {
+        output[0] = Val::I32(log_level_to_int(
+            level.into_level().unwrap_or(tracing::Level::ERROR),
+        ));
+    }
+    Ok(())
+}
+
+/// Convert log level to integer
+pub(crate) const fn log_level_to_int(level: tracing::Level) -> i32 {
+    match level {
+        tracing::Level::TRACE => 0,
+        tracing::Level::DEBUG => 1,
+        tracing::Level::INFO => 2,
+        tracing::Level::WARN => 3,
+        tracing::Level::ERROR => 4,
+    }
+}

runtime/src/plugin.rs

@@ -4,6 +4,8 @@ use std::{
     path::PathBuf,
 };
 
+use anyhow::Context;
+
 use crate::*;
 
 pub const EXTISM_ENV_MODULE: &str = "extism:host/env";
@@ -81,6 +83,12 @@ pub struct Plugin {
     pub(crate) store_needs_reset: bool,
 
     pub(crate) debug_options: DebugOptions,
+
+    pub(crate) error_msg: Option<Vec<u8>>,
+
+    pub(crate) fuel: Option<u64>,
+
+    pub(crate) host_context: Rooted<ExternRef>,
 }
 
 unsafe impl Send for Plugin {}
@@ -212,14 +220,24 @@ fn add_module<T: 'static>(
     Ok(())
 }
 
+#[allow(clippy::type_complexity)]
 fn relink(
     engine: &Engine,
     mut store: &mut Store<CurrentPlugin>,
     imports: &[Function],
     modules: &BTreeMap<String, Module>,
     with_wasi: bool,
-) -> Result<(InstancePre<CurrentPlugin>, Linker<CurrentPlugin>), Error> {
+) -> Result<
+    (
+        InstancePre<CurrentPlugin>,
+        Linker<CurrentPlugin>,
+        Rooted<ExternRef>,
+    ),
+    Error,
+> {
     let mut linker = Linker::new(engine);
+    linker.allow_shadowing(true);
+
     // Define PDK functions
     macro_rules! add_funcs {
             ($($name:ident($($args:expr),*) $(-> $($r:expr),*)?);* $(;)?) => {
@@ -242,6 +260,8 @@ fn relink(
         log_info(I64);
         log_debug(I64);
         log_error(I64);
+        log_trace(I64);
+        get_log_level() -> I32;
     );
 
     let mut linked = BTreeSet::new();
@@ -274,9 +294,12 @@ fn relink(
         )?;
     }
 
+    let inner: Box<dyn std::any::Any + Send + Sync> = Box::new(());
+    let host_context = ExternRef::new(store, inner)?;
+
     let main = &modules[MAIN_KEY];
     let instance_pre = linker.instantiate_pre(main)?;
-    Ok((instance_pre, linker))
+    Ok((instance_pre, linker, host_context))
 }
 
 impl Plugin {
@@ -287,7 +310,14 @@ impl Plugin {
         imports: impl IntoIterator<Item = Function>,
         with_wasi: bool,
     ) -> Result<Plugin, Error> {
-        Self::build_new(wasm.into(), imports, with_wasi, Default::default(), None)
+        Self::build_new(
+            wasm.into(),
+            imports,
+            with_wasi,
+            Default::default(),
+            None,
+            None,
+        )
     }
 
     pub(crate) fn build_new(
@@ -296,6 +326,7 @@ impl Plugin {
         with_wasi: bool,
         debug_options: DebugOptions,
         cache_dir: Option<Option<PathBuf>>,
+        fuel: Option<u64>,
     ) -> Result<Plugin, Error> {
         // Setup wasmtime types
         let mut config = Config::new();
@@ -308,6 +339,10 @@ impl Plugin {
             .wasm_function_references(true)
             .wasm_gc(true);
 
+        if fuel.is_some() {
+            config.consume_fuel(true);
+        }
+
         match cache_dir {
             Some(None) => (),
             Some(Some(path)) => {
@@ -341,10 +376,13 @@ impl Plugin {
             CurrentPlugin::new(manifest, with_wasi, available_pages, id)?,
         );
         store.set_epoch_deadline(1);
+        if let Some(fuel) = fuel {
+            store.set_fuel(fuel)?;
+        }
 
         let imports: Vec<Function> = imports.into_iter().collect();
-        let (instance_pre, linker) = relink(&engine, &mut store, &imports, &modules, with_wasi)?;
-
+        let (instance_pre, linker, host_context) =
+            relink(&engine, &mut store, &imports, &modules, with_wasi)?;
         let timer_tx = Timer::tx();
         let mut plugin = Plugin {
             modules,
@@ -361,6 +399,9 @@ impl Plugin {
             store_needs_reset: false,
             debug_options,
             _functions: imports,
+            error_msg: None,
+            fuel,
+            host_context,
         };
 
         plugin.current_plugin_mut().store = &mut plugin.store;
@@ -394,7 +435,11 @@ impl Plugin {
             );
             self.store.set_epoch_deadline(1);
 
-            let (instance_pre, linker) = relink(
+            if let Some(fuel) = self.fuel {
+                self.store.set_fuel(fuel)?;
+            }
+
+            let (instance_pre, linker, host_context) = relink(
                 &engine,
                 &mut self.store,
                 &self._functions,
@@ -403,6 +448,7 @@ impl Plugin {
             )?;
             self.linker = linker;
             self.instance_pre = instance_pre;
+            self.host_context = host_context;
             let store = &mut self.store as *mut _;
             let linker = &mut self.linker as *mut _;
             let current_plugin = self.current_plugin_mut();
@@ -510,10 +556,16 @@ impl Plugin {
             .linker
             .get(&mut self.store, EXTISM_ENV_MODULE, "input_set")
         {
-            f.into_func().unwrap().call(
-                &mut self.store,
-                &[Val::I64(handle.offset() as i64), Val::I64(len as i64)],
-                &mut [],
+            catch_out_of_fuel!(
+                &self.store,
+                f.into_func()
+                    .unwrap()
+                    .call(
+                        &mut self.store,
+                        &[Val::I64(handle.offset() as i64), Val::I64(len as i64)],
+                        &mut [],
+                    )
+                    .context("unable to set extism input")
             )?;
         }
 
@@ -521,7 +573,8 @@ impl Plugin {
             self.linker
                 .get(&mut self.store, EXTISM_ENV_MODULE, "extism_context")
         {
-            ctxt.set(&mut self.store, Val::ExternRef(host_context))?;
+            ctxt.set(&mut self.store, Val::ExternRef(host_context))
+                .context("unable to set extism host context")?;
         }
 
         Ok(())
@@ -532,7 +585,13 @@ impl Plugin {
         let id = self.id.to_string();
 
         if let Some(f) = self.linker.get(&mut self.store, EXTISM_ENV_MODULE, "reset") {
-            f.into_func().unwrap().call(&mut self.store, &[], &mut [])?;
+            catch_out_of_fuel!(
+                &self.store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut self.store, &[], &mut [])
+                    .context("extism reset failed")
+            )?;
         } else {
             error!(plugin = &id, "call to extism:host/env::reset failed");
         }
@@ -608,19 +667,28 @@ impl Plugin {
 
     // Initialize the guest runtime
     pub(crate) fn initialize_guest_runtime(&mut self) -> Result<(), Error> {
-        let mut store = &mut self.store;
+        let store = &mut self.store;
         if let Some(runtime) = &self.runtime {
             trace!(plugin = self.id.to_string(), "Plugin::initialize_runtime");
             match runtime {
                 GuestRuntime::Haskell { init, reactor_init } => {
                     if let Some(reactor_init) = reactor_init {
-                        reactor_init.call(&mut store, &[], &mut [])?;
+                        catch_out_of_fuel!(
+                            &store,
+                            reactor_init
+                                .call(&mut *store, &[], &mut [])
+                                .context("failed to initialize Haskell reactor runtime")
+                        )?;
                     }
-                    let mut results = vec![Val::I32(0); init.ty(&store).results().len()];
-                    init.call(
-                        &mut store,
-                        &[Val::I32(0), Val::I32(0)],
-                        results.as_mut_slice(),
+                    let mut results = vec![Val::I32(0); init.ty(&*store).results().len()];
+                    catch_out_of_fuel!(
+                        &store,
+                        init.call(
+                            &mut *store,
+                            &[Val::I32(0), Val::I32(0)],
+                            results.as_mut_slice(),
+                        )
+                        .context("failed to initialize Haskell using hs_init")
                     )?;
                     debug!(
                         plugin = self.id.to_string(),
@@ -628,7 +696,11 @@ impl Plugin {
                     );
                 }
                 GuestRuntime::Wasi { init } => {
-                    init.call(&mut store, &[], &mut [])?;
+                    catch_out_of_fuel!(
+                        &store,
+                        init.call(&mut *store, &[], &mut [])
+                            .context("failed to initialize wasi runtime")
+                    )?;
                     debug!(plugin = self.id.to_string(), "initialied WASI runtime");
                 }
             }
@@ -641,20 +713,32 @@ impl Plugin {
     fn output_memory_position(&mut self) -> Result<(u64, u64), Error> {
         let out = &mut [Val::I64(0)];
         let out_len = &mut [Val::I64(0)];
-        let mut store = &mut self.store;
+        let store = &mut self.store;
         if let Some(f) = self
             .linker
-            .get(&mut store, EXTISM_ENV_MODULE, "output_offset")
+            .get(&mut *store, EXTISM_ENV_MODULE, "output_offset")
         {
-            f.into_func().unwrap().call(&mut store, &[], out)?;
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[], out)
+                    .context("call to set extism output offset failed")
+            )?;
         } else {
             anyhow::bail!("unable to set output")
         }
         if let Some(f) = self
             .linker
-            .get(&mut store, EXTISM_ENV_MODULE, "output_length")
+            .get(&mut *store, EXTISM_ENV_MODULE, "output_length")
         {
-            f.into_func().unwrap().call(&mut store, &[], out_len)?;
+            catch_out_of_fuel!(
+                &store,
+                f.into_func()
+                    .unwrap()
+                    .call(&mut *store, &[], out_len)
+                    .context("call to set extism output length failed")
+            )?;
         } else {
             anyhow::bail!("unable to set output length")
         }
@@ -668,10 +752,10 @@ impl Plugin {
     fn output<'a, T: FromBytes<'a>>(&'a mut self) -> Result<T, Error> {
         let offs = self.output.offset;
         let len = self.output.length;
-        T::from_bytes(
-            self.current_plugin_mut()
-                .memory_bytes(unsafe { MemoryHandle::new(offs, len) })?,
-        )
+        let x = self
+            .current_plugin_mut()
+            .memory_bytes(unsafe { MemoryHandle::new(offs, len) })?;
+        T::from_bytes(x)
     }
 
     // Cache output memory and error information after call is complete
@@ -696,26 +780,40 @@ impl Plugin {
 
     // Implements the build of the `call` function, `raw_call` is also used in the SDK
     // code
-    pub(crate) fn raw_call(
+    pub(crate) fn raw_call<T: 'static + Send + Sync>(
         &mut self,
         lock: &mut std::sync::MutexGuard<Option<Instance>>,
         name: impl AsRef<str>,
         input: impl AsRef<[u8]>,
-        host_context: Option<Rooted<ExternRef>>,
+        host_context: Option<T>,
     ) -> Result<i32, (Error, i32)> {
         let name = name.as_ref();
         let input = input.as_ref();
 
-        if let Err(e) = self.reset_store(lock) {
-            error!(
-                plugin = self.id.to_string(),
-                "call to Plugin::reset_store failed: {e:?}"
-            );
+        if let Some(fuel) = self.fuel {
+            self.store.set_fuel(fuel).map_err(|x| (x, -1))?;
         }
 
+        catch_out_of_fuel!(&self.store, self.reset_store(lock)).map_err(|x| (x, -1))?;
+
         self.instantiate(lock).map_err(|e| (e, -1))?;
 
-        self.set_input(input.as_ptr(), input.len(), host_context)
+        // Set host context
+        let r = if let Some(host_context) = host_context {
+            let inner = self
+                .host_context
+                .data_mut(&mut self.store)
+                .map_err(|x| (x, -1))?;
+            if let Some(inner) = inner.downcast_mut::<Box<dyn std::any::Any + Send + Sync>>() {
+                let x: Box<T> = Box::new(host_context);
+                *inner = x;
+            }
+            Some(self.host_context)
+        } else {
+            None
+        };
+
+        self.set_input(input.as_ptr(), input.len(), r)
             .map_err(|x| (x, -1))?;
 
         let func = match self.get_func(lock, name) {
@@ -752,40 +850,57 @@ impl Plugin {
         let mut results = vec![wasmtime::Val::I32(0); n_results];
         let mut res = func.call(self.store_mut(), &[], results.as_mut_slice());
 
+        // Reset host context
+        if let Ok(inner) = self.host_context.data_mut(&mut self.store) {
+            if let Some(inner) = inner.downcast_mut::<Box<dyn std::any::Any + Send + Sync>>() {
+                let x: Box<dyn Any + Send + Sync> = Box::new(());
+                *inner = x;
+            }
+        }
+
         // Stop timer
         self.store
             .epoch_deadline_callback(|_| Ok(UpdateDeadline::Continue(1)));
         let _ = self.timer_tx.send(TimerAction::Stop { id: self.id });
         self.store_needs_reset = name == "_start";
 
-        // Get extism error
-        self.get_output_after_call().map_err(|x| (x, -1))?;
         let mut rc = 0;
-        if !results.is_empty() {
-            rc = results[0].i32().unwrap_or(-1);
-            debug!(plugin = self.id.to_string(), "got return code: {}", rc);
-        }
+        if self.store.get_fuel().is_ok_and(|x| x == 0) {
+            res = Err(Error::msg("plugin ran out of fuel"));
+            rc = -1;
+        } else {
+            // Get extism error
+            self.get_output_after_call().map_err(|x| (x, -1))?;
+            if !results.is_empty() {
+                rc = results[0].i32().unwrap_or(-1);
+                debug!(plugin = self.id.to_string(), "got return code: {}", rc);
+            }
 
-        if self.output.error_offset != 0 && self.output.error_length != 0 {
-            let handle = MemoryHandle {
-                offset: self.output.error_offset,
-                length: self.output.error_length,
-            };
-            if let Ok(e) = self.current_plugin_mut().memory_str(handle) {
-                let x = e.to_string();
-                error!(
-                    plugin = self.id.to_string(),
-                    "call to {name} returned with error message: {}", x
-                );
-                if let Err(e) = res {
-                    res = Err(Error::msg(x).context(e));
-                } else {
-                    res = Err(Error::msg(x))
+            if self.output.error_offset != 0 && self.output.error_length != 0 {
+                let handle = MemoryHandle {
+                    offset: self.output.error_offset,
+                    length: self.output.error_length,
+                };
+                match self.current_plugin_mut().memory_str(handle) {
+                    Ok(e) => {
+                        let x = e.to_string();
+                        error!(
+                            plugin = self.id.to_string(),
+                            "call to {name} returned with error message: {}", x
+                        );
+                        if let Err(e) = res {
+                            res = Err(Error::msg(x).context(e));
+                        } else {
+                            res = Err(Error::msg(x))
+                        }
+                    }
+                    Err(msg) => {
+                        res = Err(Error::msg(format!(
+                            "Call to Extism plugin function {name} encountered an error: {}",
+                            msg,
+                        )));
+                    }
                 }
-            } else {
-                res = Err(Error::msg(format!(
-                    "Call to Extism plugin function {name} encountered an error"
-                )));
             }
         }
 
@@ -897,7 +1012,7 @@ impl Plugin {
         let lock = self.instance.clone();
         let mut lock = lock.lock().unwrap();
         let data = input.to_bytes()?;
-        self.raw_call(&mut lock, name, data, None)
+        self.raw_call(&mut lock, name, data, None::<()>)
             .map_err(|e| e.0)
             .and_then(move |rc| {
                 if rc != 0 {
@@ -922,8 +1037,7 @@ impl Plugin {
         let lock = self.instance.clone();
         let mut lock = lock.lock().unwrap();
         let data = input.to_bytes()?;
-        let ctx = ExternRef::new(&mut self.store, host_context)?;
-        self.raw_call(&mut lock, name, data, Some(ctx))
+        self.raw_call(&mut lock, name, data, Some(host_context))
             .map_err(|e| e.0)
             .and_then(move |_| self.output())
     }
@@ -942,7 +1056,7 @@ impl Plugin {
         let lock = self.instance.clone();
         let mut lock = lock.lock().unwrap();
         let data = input.to_bytes().map_err(|e| (e, -1))?;
-        self.raw_call(&mut lock, name, data, None)
+        self.raw_call(&mut lock, name, data, None::<()>)
             .and_then(move |_| self.output().map_err(|e| (e, -1)))
     }
 
@@ -953,42 +1067,21 @@ impl Plugin {
 
     pub(crate) fn clear_error(&mut self) -> Result<(), Error> {
         trace!(plugin = self.id.to_string(), "clearing error");
+        self.error_msg = None;
         let (linker, mut store) = self.linker_and_store();
-        if let Some(f) = linker.get(&mut store, EXTISM_ENV_MODULE, "error_set") {
-            f.into_func()
+        #[allow(clippy::needless_borrows_for_generic_args)]
+        if let Some(f) = linker.get(&mut *store, EXTISM_ENV_MODULE, "error_set") {
+            let x = f
+                .into_func()
                 .unwrap()
-                .call(&mut store, &[Val::I64(0)], &mut [])?;
+                .call(&mut store, &[Val::I64(0)], &mut [])
+                .context("unable to clear error message");
+            catch_out_of_fuel!(&store, x)?;
             Ok(())
         } else {
             anyhow::bail!("Plugin::clear_error failed, extism:host/env::error_set not found")
         }
     }
-
-    // A convenience method to set the plugin error and return a value
-    pub(crate) fn return_error<E>(
-        &mut self,
-        instance_lock: &mut std::sync::MutexGuard<Option<Instance>>,
-        e: impl std::fmt::Display,
-        x: E,
-    ) -> E {
-        if instance_lock.is_none() {
-            error!(
-                plugin = self.id.to_string(),
-                "no instance, unable to set error: {}", e
-            );
-            return x;
-        }
-        match self.current_plugin_mut().set_error(e.to_string()) {
-            Ok((a, b)) => {
-                self.output.error_offset = a;
-                self.output.error_length = b;
-            }
-            Err(e) => {
-                error!(plugin = self.id.to_string(), "unable to set error: {e:?}")
-            }
-        }
-        x
-    }
 }
 
 // Enumerates the PDK languages that need some additional initialization

runtime/src/plugin_builder.rs

@@ -39,6 +39,7 @@ pub struct PluginBuilder<'a> {
     functions: Vec<Function>,
     debug_options: DebugOptions,
     cache_config: Option<Option<PathBuf>>,
+    fuel: Option<u64>,
 }
 
 impl<'a> PluginBuilder<'a> {
@@ -50,6 +51,7 @@ impl<'a> PluginBuilder<'a> {
             functions: vec![],
             debug_options: DebugOptions::default(),
             cache_config: None,
+            fuel: None,
         }
     }
 
@@ -148,6 +150,12 @@ impl<'a> PluginBuilder<'a> {
         self
     }
 
+    // Limit the number of instructions that can be executed
+    pub fn with_fuel_limit(mut self, fuel: u64) -> Self {
+        self.fuel = Some(fuel);
+        self
+    }
+
     /// Generate a new plugin with the configured settings
     pub fn build(self) -> Result<Plugin, Error> {
         Plugin::build_new(
@@ -156,6 +164,7 @@ impl<'a> PluginBuilder<'a> {
             self.wasi,
             self.debug_options,
             self.cache_config,
+            self.fuel,
         )
     }
 }

runtime/src/readonly_dir.rs

@@ -0,0 +1,109 @@
+use crate::*;
+
+use wasi_common::{Error, ErrorExt};
+
+pub struct ReadOnlyDir<D: wasi_common::WasiDir> {
+    inner: std::sync::Arc<D>,
+}
+
+impl<D: wasi_common::WasiDir> ReadOnlyDir<D> {
+    pub fn new(inner: D) -> Self {
+        ReadOnlyDir {
+            inner: std::sync::Arc::new(inner),
+        }
+    }
+}
+
+#[wiggle::async_trait]
+impl<D: wasi_common::WasiDir> wasi_common::WasiDir for ReadOnlyDir<D> {
+    fn as_any(&self) -> &dyn std::any::Any {
+        self.inner.as_any()
+    }
+
+    async fn open_file(
+        &self,
+        symlink_follow: bool,
+        path: &str,
+        oflags: wasi_common::file::OFlags,
+        read: bool,
+        write: bool,
+        fdflags: wasi_common::file::FdFlags,
+    ) -> Result<wasi_common::dir::OpenResult, Error> {
+        if write {
+            return Err(Error::not_supported());
+        }
+        self.inner
+            .open_file(symlink_follow, path, oflags, read, false, fdflags)
+            .await
+    }
+
+    async fn create_dir(&self, _path: &str) -> Result<(), Error> {
+        Err(Error::not_supported())
+    }
+
+    async fn readdir(
+        &self,
+        cursor: wasi_common::dir::ReaddirCursor,
+    ) -> Result<
+        Box<dyn Iterator<Item = Result<wasi_common::dir::ReaddirEntity, Error>> + Send>,
+        Error,
+    > {
+        self.inner.readdir(cursor).await
+    }
+
+    async fn symlink(&self, _old_path: &str, _new_path: &str) -> Result<(), Error> {
+        Err(Error::not_supported())
+    }
+
+    async fn remove_dir(&self, _path: &str) -> Result<(), Error> {
+        Err(Error::not_supported())
+    }
+
+    async fn unlink_file(&self, _path: &str) -> Result<(), Error> {
+        Err(Error::not_supported())
+    }
+
+    async fn read_link(&self, path: &str) -> Result<std::path::PathBuf, Error> {
+        self.inner.read_link(path).await
+    }
+
+    async fn get_filestat(&self) -> Result<wasi_common::file::Filestat, Error> {
+        self.inner.get_filestat().await
+    }
+
+    async fn get_path_filestat(
+        &self,
+        path: &str,
+        follow_symlinks: bool,
+    ) -> Result<wasi_common::file::Filestat, Error> {
+        self.inner.get_path_filestat(path, follow_symlinks).await
+    }
+
+    async fn rename(
+        &self,
+        _path: &str,
+        _dest_dir: &dyn wasi_common::WasiDir,
+        _dest_path: &str,
+    ) -> Result<(), Error> {
+        Err(wasi_common::Error::not_supported())
+    }
+
+    async fn hard_link(
+        &self,
+        _path: &str,
+        _target_dir: &dyn wasi_common::WasiDir,
+        _target_path: &str,
+    ) -> Result<(), Error> {
+        Err(wasi_common::Error::not_supported())
+    }
+
+    async fn set_times(
+        &self,
+        _path: &str,
+        _atime: std::option::Option<wasi_common::SystemTimeSpec>,
+        _mtime: std::option::Option<wasi_common::SystemTimeSpec>,
+        _follow_symlinks: bool,
+    ) -> Result<(), Error> {
+        Err(wasi_common::Error::not_supported())
+    }
+}

runtime/src/sdk.rs

@@ -1,6 +1,6 @@
 #![allow(clippy::missing_safety_doc)]
 
-use std::os::raw::c_char;
+use std::{os::raw::c_char, ptr::null_mut};
 
 use crate::*;
 
@@ -11,6 +11,12 @@ pub struct ExtismFunction(std::cell::Cell<Option<Function>>);
 /// The return code used to specify a successful plugin call
 pub static EXTISM_SUCCESS: i32 = 0;
 
+fn make_error_msg(s: String) -> Vec<u8> {
+    let mut s = s.into_bytes();
+    s.push(0);
+    s
+}
+
 /// A union type for host function argument/return values
 #[repr(C)]
 pub union ValUnion {
@@ -96,7 +102,7 @@ pub unsafe extern "C" fn extism_current_plugin_host_context(
 
     let plugin = &mut *plugin;
     if let Ok(CVoidContainer(ptr)) = plugin.host_context::<CVoidContainer>() {
-        ptr
+        *ptr
     } else {
         std::ptr::null_mut()
     }
@@ -231,12 +237,28 @@ pub unsafe extern "C" fn extism_function_new(
                 })
                 .collect();
 
+            // We cannot simply "get" the Vec's storage pointer because
+            // the underlying storage might be invalid when the Vec is empty.
+            // In that case, we return (null, 0).
+
+            let (inputs_ptr, inputs_len) = if inputs.is_empty() {
+                (core::ptr::null(), 0 as Size)
+            } else {
+                (inputs.as_ptr(), inputs.len() as Size)
+            };
+
+            let (output_ptr, output_len) = if output_tmp.is_empty() {
+                (null_mut(), 0 as Size)
+            } else {
+                (output_tmp.as_mut_ptr(), output_tmp.len() as Size)
+            };
+
             func(
                 plugin,
-                inputs.as_ptr(),
-                inputs.len() as Size,
-                output_tmp.as_mut_ptr(),
-                output_tmp.len() as Size,
+                inputs_ptr,
+                inputs_len,
+                output_ptr,
+                output_len,
                 user_data.as_ptr(),
             );
 
@@ -334,6 +356,66 @@ pub unsafe extern "C" fn extism_plugin_new(
     }
 }
 
+/// Create a new plugin and set the number of instructions a plugin is allowed to execute
+#[no_mangle]
+pub unsafe extern "C" fn extism_plugin_new_with_fuel_limit(
+    wasm: *const u8,
+    wasm_size: Size,
+    functions: *mut *const ExtismFunction,
+    n_functions: Size,
+    with_wasi: bool,
+    fuel_limit: u64,
+    errmsg: *mut *mut std::ffi::c_char,
+) -> *mut Plugin {
+    trace!(
+        "Call to extism_plugin_new_with_fuel_limit with wasm pointer {:?}",
+        wasm
+    );
+    let data = std::slice::from_raw_parts(wasm, wasm_size as usize);
+    let mut funcs = vec![];
+
+    if !functions.is_null() {
+        for i in 0..n_functions {
+            unsafe {
+                let f = *functions.add(i as usize);
+                if f.is_null() {
+                    continue;
+                }
+                if let Some(f) = (*f).0.take() {
+                    funcs.push(f);
+                } else {
+                    let e = std::ffi::CString::new(
+                        "Function cannot be registered with multiple different Plugins",
+                    )
+                    .unwrap();
+                    *errmsg = e.into_raw();
+                }
+            }
+        }
+    }
+
+    let plugin = Plugin::build_new(
+        data.into(),
+        funcs,
+        with_wasi,
+        Default::default(),
+        None,
+        Some(fuel_limit),
+    );
+
+    match plugin {
+        Err(e) => {
+            if !errmsg.is_null() {
+                let e = std::ffi::CString::new(format!("Unable to create Extism plugin: {}", e))
+                    .unwrap();
+                *errmsg = e.into_raw();
+            }
+            std::ptr::null_mut()
+        }
+        Ok(p) => Box::into_raw(Box::new(p)),
+    }
+}
+
 /// Free the error returned by `extism_plugin_new`, errors returned from `extism_plugin_error` don't need to be freed
 #[no_mangle]
 pub unsafe extern "C" fn extism_plugin_new_error_free(err: *mut std::ffi::c_char) {
@@ -394,8 +476,6 @@ pub unsafe extern "C" fn extism_plugin_config(
         return false;
     }
     let plugin = &mut *plugin;
-    let _lock = plugin.instance.clone();
-    let mut lock = _lock.lock().unwrap();
 
     trace!(
         plugin = plugin.id.to_string(),
@@ -406,8 +486,8 @@ pub unsafe extern "C" fn extism_plugin_config(
     let json: std::collections::BTreeMap<String, Option<String>> =
         match serde_json::from_slice(data) {
             Ok(x) => x,
-            Err(e) => {
-                return plugin.return_error(&mut lock, e, false);
+            Err(_) => {
+                return false;
             }
         };
 
@@ -440,9 +520,6 @@ pub unsafe extern "C" fn extism_plugin_function_exists(
         return false;
     }
     let plugin = &mut *plugin;
-    let _lock = plugin.instance.clone();
-    let mut lock = _lock.lock().unwrap();
-
     let name = std::ffi::CStr::from_ptr(func_name);
     trace!(
         plugin = plugin.id.to_string(),
@@ -452,8 +529,8 @@ pub unsafe extern "C" fn extism_plugin_function_exists(
 
     let name = match name.to_str() {
         Ok(x) => x,
-        Err(e) => {
-            return plugin.return_error(&mut lock, e, false);
+        Err(_) => {
+            return false;
         }
     };
 
@@ -509,7 +586,10 @@ pub unsafe extern "C" fn extism_plugin_call_with_host_context(
     let name = std::ffi::CStr::from_ptr(func_name);
     let name = match name.to_str() {
         Ok(name) => name,
-        Err(e) => return plugin.return_error(&mut lock, e, -1),
+        Err(e) => {
+            plugin.error_msg = Some(make_error_msg(e.to_string()));
+            return -1;
+        }
     };
 
     trace!(
@@ -518,13 +598,17 @@ pub unsafe extern "C" fn extism_plugin_call_with_host_context(
         name
     );
     let input = std::slice::from_raw_parts(data, data_len as usize);
-    let r = match ExternRef::new(&mut plugin.store, CVoidContainer(host_context)) {
-        Err(e) => return plugin.return_error(&mut lock, e, -1),
-        Ok(x) => x,
+    let r = if host_context.is_null() {
+        None
+    } else {
+        Some(CVoidContainer(host_context))
     };
-    let res = plugin.raw_call(&mut lock, name, input, Some(r));
+    let res = plugin.raw_call(&mut lock, name, input, r);
     match res {
-        Err((e, rc)) => plugin.return_error(&mut lock, e, rc),
+        Err((e, rc)) => {
+            plugin.error_msg = Some(make_error_msg(e.to_string()));
+            rc
+        }
         Ok(x) => x,
     }
 }
@@ -547,14 +631,26 @@ pub unsafe extern "C" fn extism_plugin_error(plugin: *mut Plugin) -> *const c_ch
     let _lock = _lock.lock().unwrap();
 
     if plugin.output.error_offset == 0 {
+        if let Some(err) = &plugin.error_msg {
+            return err.as_ptr() as *const _;
+        }
         trace!(plugin = plugin.id.to_string(), "error is NULL");
         return std::ptr::null();
     }
 
-    plugin
+    let offs = plugin.output.error_offset;
+
+    let ptr = plugin.current_plugin_mut().memory_ptr().add(offs as usize) as *const _;
+
+    let len = plugin
         .current_plugin_mut()
-        .memory_ptr()
-        .add(plugin.output.error_offset as usize) as *const _
+        .memory_length(offs)
+        .unwrap_or_default();
+
+    let mut data = std::slice::from_raw_parts(ptr, len as usize).to_vec();
+    data.push(0);
+    plugin.error_msg = Some(data);
+    plugin.error_msg.as_ref().unwrap().as_ptr() as *const _
 }
 
 /// Get the length of a plugin's output data
@@ -629,7 +725,6 @@ pub unsafe extern "C" fn extism_log_file(
 fn set_log_file(log_file: impl Into<std::path::PathBuf>, filter: &str) -> Result<(), Error> {
     let log_file = log_file.into();
     let s = log_file.to_str();
-
     let is_level = tracing::Level::from_str(filter).is_ok();
     let cfg = tracing_subscriber::FmtSubscriber::builder().with_env_filter({
         let x = tracing_subscriber::EnvFilter::builder()
@@ -680,6 +775,7 @@ pub unsafe extern "C" fn extism_log_custom(log_level: *const c_char) -> bool {
     } else {
         "error"
     };
+
     set_log_buffer(level).is_ok()
 }
 

runtime/src/tests/data/data.txt

@@ -0,0 +1 @@
+hello world!

runtime/src/tests/kernel.rs

@@ -3,36 +3,32 @@ use quickcheck::*;
 
 const KERNEL: &[u8] = include_bytes!("../extism-runtime.wasm");
 
-fn extism_alloc<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, n: u64) -> u64 {
+fn extism_alloc<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, n: u64) -> u64 {
     let out_alloc = &mut [Val::I64(0)];
     instance
-        .get_func(&mut store, "alloc")
+        .get_func(&mut *store, "alloc")
         .unwrap()
-        .call(&mut store, &[Val::I64(n as i64)], out_alloc)
+        .call(store, &[Val::I64(n as i64)], out_alloc)
         .unwrap();
     out_alloc[0].unwrap_i64() as u64
 }
 
-fn extism_length<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
+fn extism_length<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
     let out = &mut [Val::I64(0)];
     instance
-        .get_func(&mut store, "length")
+        .get_func(&mut *store, "length")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i64() as u64
 }
 
-fn extism_length_unsafe<T>(
-    mut store: &mut wasmtime::Store<T>,
-    instance: &mut Instance,
-    p: u64,
-) -> u64 {
+fn extism_length_unsafe<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
     let out = &mut [Val::I64(0)];
     instance
-        .get_func(&mut store, "length_unsafe")
+        .get_func(&mut *store, "length_unsafe")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i64() as u64
 }
@@ -47,122 +43,96 @@ fn extism_load_u8<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance
     out[0].unwrap_i32() as u8
 }
 
-fn extism_load_u64<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
+fn extism_load_u64<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u64 {
     let out = &mut [Val::I32(0)];
     instance
-        .get_func(&mut store, "load_u64")
+        .get_func(&mut *store, "load_u64")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i64() as u64
 }
 
-fn extism_input_load_u8<T>(
-    mut store: &mut wasmtime::Store<T>,
-    instance: &mut Instance,
-    p: u64,
-) -> u8 {
+fn extism_input_load_u8<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) -> u8 {
     let out = &mut [Val::I32(0)];
     instance
-        .get_func(&mut store, "input_load_u8")
+        .get_func(&mut *store, "input_load_u8")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i32() as u8
 }
 
 fn extism_input_load_u64<T>(
-    mut store: &mut wasmtime::Store<T>,
+    store: &mut wasmtime::Store<T>,
     instance: &mut Instance,
     p: u64,
 ) -> u64 {
     let out = &mut [Val::I32(0)];
     instance
-        .get_func(&mut store, "input_load_u64")
+        .get_func(&mut *store, "input_load_u64")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], out)
+        .call(store, &[Val::I64(p as i64)], out)
         .unwrap();
     out[0].unwrap_i64() as u64
 }
 
-fn extism_store_u8<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64, x: u8) {
+fn extism_store_u8<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64, x: u8) {
     instance
-        .get_func(&mut store, "store_u8")
+        .get_func(&mut *store, "store_u8")
         .unwrap()
-        .call(
-            &mut store,
-            &[Val::I64(p as i64), Val::I32(x as i32)],
-            &mut [],
-        )
+        .call(store, &[Val::I64(p as i64), Val::I32(x as i32)], &mut [])
         .unwrap();
 }
 
-fn extism_store_u64<T>(
-    mut store: &mut wasmtime::Store<T>,
-    instance: &mut Instance,
-    p: u64,
-    x: u64,
-) {
+fn extism_store_u64<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64, x: u64) {
     instance
-        .get_func(&mut store, "store_u64")
+        .get_func(&mut *store, "store_u64")
         .unwrap()
-        .call(
-            &mut store,
-            &[Val::I64(p as i64), Val::I64(x as i64)],
-            &mut [],
-        )
+        .call(store, &[Val::I64(p as i64), Val::I64(x as i64)], &mut [])
         .unwrap();
 }
 
-fn extism_free<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) {
+fn extism_free<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) {
     instance
-        .get_func(&mut store, "free")
+        .get_func(&mut *store, "free")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], &mut [])
+        .call(store, &[Val::I64(p as i64)], &mut [])
         .unwrap();
 }
 
-fn extism_error_set<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) {
+fn extism_error_set<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64) {
     instance
-        .get_func(&mut store, "error_set")
+        .get_func(&mut *store, "error_set")
         .unwrap()
-        .call(&mut store, &[Val::I64(p as i64)], &mut [])
+        .call(store, &[Val::I64(p as i64)], &mut [])
         .unwrap();
 }
 
-fn extism_error_get<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance) -> u64 {
+fn extism_error_get<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance) -> u64 {
     let out = &mut [Val::I64(0)];
     instance
-        .get_func(&mut store, "error_get")
+        .get_func(&mut *store, "error_get")
         .unwrap()
-        .call(&mut store, &[], out)
+        .call(store, &[], out)
         .unwrap();
 
     out[0].unwrap_i64() as u64
 }
 
-fn extism_reset<T>(mut store: &mut wasmtime::Store<T>, instance: &mut Instance) {
+fn extism_reset<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance) {
     instance
-        .get_func(&mut store, "reset")
+        .get_func(&mut *store, "reset")
         .unwrap()
-        .call(&mut store, &[], &mut [])
+        .call(store, &[], &mut [])
         .unwrap();
 }
 
-fn extism_input_set<T>(
-    mut store: &mut wasmtime::Store<T>,
-    instance: &mut Instance,
-    p: u64,
-    l: u64,
-) {
+fn extism_input_set<T>(store: &mut wasmtime::Store<T>, instance: &mut Instance, p: u64, l: u64) {
     instance
-        .get_func(&mut store, "input_set")
+        .get_func(&mut *store, "input_set")
         .unwrap()
-        .call(
-            &mut store,
-            &[Val::I64(p as i64), Val::I64(l as i64)],
-            &mut [],
-        )
+        .call(store, &[Val::I64(p as i64), Val::I64(l as i64)], &mut [])
         .unwrap();
 }
 

runtime/src/tests/runtime.rs

@@ -9,6 +9,7 @@ const WASM_LOOP: &[u8] = include_bytes!("../../../wasm/loop.wasm");
 const WASM_GLOBALS: &[u8] = include_bytes!("../../../wasm/globals.wasm");
 const WASM_REFLECT: &[u8] = include_bytes!("../../../wasm/reflect.wasm");
 const WASM_HTTP: &[u8] = include_bytes!("../../../wasm/http.wasm");
+const WASM_FS: &[u8] = include_bytes!("../../../wasm/read_write.wasm");
 
 host_fn!(pub hello_world (a: String) -> String { Ok(a) });
 
@@ -241,6 +242,23 @@ fn test_timeout() {
 }
 
 #[test]
+fn test_fuel() {
+    let manifest = Manifest::new([extism_manifest::Wasm::data(WASM_LOOP)]);
+    let mut plugin = PluginBuilder::new(manifest)
+        .with_wasi(true)
+        .with_fuel_limit(1)
+        .build()
+        .unwrap();
+    for _ in 0..10001 {
+        let output: Result<&[u8], Error> = plugin.call("loop_forever", "abc123");
+        let err = output.unwrap_err().root_cause().to_string();
+        println!("Fuel limited plugin exited with error: {:?}", &err);
+        assert!(err.contains("fuel"));
+    }
+}
+
+#[test]
+#[cfg(feature = "http")]
 fn test_http_timeout() {
     let f = Function::new(
         "hello_world",
@@ -316,8 +334,10 @@ fn test_multiple_instantiations() {
 #[test]
 fn test_globals() {
     let mut plugin = Plugin::new(WASM_GLOBALS, [], true).unwrap();
-    for i in 0..100000 {
-        let Json(count) = plugin.call::<_, Json<Count>>("globals", "").unwrap();
+    for i in 0..100001 {
+        let Json(count) = plugin
+            .call_with_host_context::<_, Json<Count>, _>("globals", "", ())
+            .unwrap();
         assert_eq!(count.count, i);
     }
 }
@@ -348,7 +368,7 @@ fn test_call_with_host_context() {
         [PTR],
         UserData::default(),
         |current_plugin, _val, ret, _user_data: UserData<()>| {
-            let foo = current_plugin.host_context::<Foo>()?;
+            let foo = current_plugin.host_context::<Foo>()?.clone();
             let hnd = current_plugin.memory_new(foo.message)?;
             ret[0] = current_plugin.memory_to_val(hnd);
             Ok(())
@@ -750,3 +770,26 @@ fn test_linking() {
         assert_eq!(plugin.call::<&str, i64>("run", "Hello, world!").unwrap(), 1);
     }
 }
+
+#[test]
+fn test_readonly_dirs() {
+    let wasm = Wasm::data(WASM_FS);
+    let manifest = Manifest::new([wasm])
+        .with_allowed_path("ro:src/tests/data".to_string(), "/data")
+        .with_config_key("path", "/data/data.txt");
+
+    let mut plugin = PluginBuilder::new(manifest)
+        .with_wasi(true)
+        .build()
+        .unwrap();
+
+    let res = plugin.call::<&str, &str>("try_read", "").unwrap();
+    assert_eq!(res, "hello world!");
+
+    let line = "hello world 2";
+    let res2 = plugin.call::<&str, &str>("try_write", line);
+    assert!(
+        res2.is_err(),
+        "Expected try_write to fail, but it succeeded."
+    );
+}