cleanup: host takes ownership of memory blocks it gets as arguments (#743)

This PR changes the host to take ownership of memory blocks passed into
Extism host functions, see:
https://github.com/extism/js-sdk/pull/71#issuecomment-2233687933

kernel/src/lib.rs

@@ -495,6 +495,8 @@ pub unsafe fn store_u64(p: Pointer, x: u64) {
 /// Set the range of the input data in memory
 /// h must always be a handle so that length works on it
 /// len must match length(handle)
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 #[no_mangle]
 pub unsafe fn input_set(h: Handle, len: u64) {
     let root = MemoryRoot::new();
@@ -509,6 +511,8 @@ pub unsafe fn input_set(h: Handle, len: u64) {
 }
 
 /// Set the range of the output data in memory
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 #[no_mangle]
 pub unsafe fn output_set(p: Pointer, len: u64) {
     let root = MemoryRoot::new();
@@ -554,6 +558,8 @@ pub unsafe fn reset() {
 
 /// Set the error message offset, the handle passed to this
 /// function should not be freed after this call
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 #[no_mangle]
 pub unsafe fn error_set(h: Handle) {
     let root = MemoryRoot::new();

runtime/src/pdk.rs

@@ -20,6 +20,8 @@ macro_rules! args {
 /// Get a configuration value
 /// Params: i64 (offset)
 /// Returns: i64 (offset)
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn config_get(
     mut caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -38,6 +40,7 @@ pub(crate) fn config_get(
     };
     let val = data.manifest.config.get(key);
     let ptr = val.map(|x| (x.len(), x.as_ptr()));
+    data.memory_free(handle)?;
     let mem = match ptr {
         Some((len, ptr)) => {
             let bytes = unsafe { std::slice::from_raw_parts(ptr, len) };
@@ -55,6 +58,9 @@ pub(crate) fn config_get(
 /// Get a variable
 /// Params: i64 (offset)
 /// Returns: i64 (offset)
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value, but the return value
+/// will need to be freed
 pub(crate) fn var_get(
     mut caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -73,6 +79,8 @@ pub(crate) fn var_get(
     };
     let val = data.vars.get(key);
     let ptr = val.map(|x| (x.len(), x.as_ptr()));
+    data.memory_free(handle)?;
+
     let mem = match ptr {
         Some((len, ptr)) => {
             let bytes = unsafe { std::slice::from_raw_parts(ptr, len) };
@@ -90,6 +98,8 @@ pub(crate) fn var_get(
 /// Set a variable, if the value offset is 0 then the provided key will be removed
 /// Params: i64 (key offset), i64 (value offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handles passed in
+/// the caller should not `free` these values
 pub(crate) fn var_set(
     mut caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -104,12 +114,12 @@ pub(crate) fn var_set(
     let voffset = args!(input, 1, i64) as u64;
     let key_offs = args!(input, 0, i64) as u64;
 
-    let key = {
+    let key_handle = match data.memory_handle(key_offs) {
-        let handle = match data.memory_handle(key_offs) {
         Some(h) => h,
         None => anyhow::bail!("invalid handle offset for var key: {key_offs}"),
     };
-        let key = data.memory_str(handle)?;
+    let key = {
+        let key = data.memory_str(key_handle)?;
         let key_len = key.len();
         let key_ptr = key.as_ptr();
         unsafe { std::str::from_utf8_unchecked(std::slice::from_raw_parts(key_ptr, key_len)) }
@@ -118,6 +128,7 @@ pub(crate) fn var_set(
     // Remove if the value offset is 0
     if voffset == 0 {
         data.vars.remove(key);
+        data.memory_free(key_handle)?;
         return Ok(());
     }
 
@@ -144,6 +155,9 @@ pub(crate) fn var_set(
 
     let value = data.memory_bytes(handle)?.to_vec();
 
+    data.memory_free(handle)?;
+    data.memory_free(key_handle)?;
+
     // Insert the value from memory into the `vars` map
     data.vars.insert(key.to_string(), value);
 
@@ -153,6 +167,9 @@ pub(crate) fn var_set(
 /// Make an HTTP request
 /// Params: i64 (offset to JSON encoded HttpRequest), i64 (offset to body or 0)
 /// Returns: i64 (offset)
+/// **Note**: this function takes ownership of the handles passed in
+/// the caller should not `free` these values, the result will need to
+/// be freed.
 pub(crate) fn http_request(
     #[allow(unused_mut)] mut caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -166,6 +183,7 @@ pub(crate) fn http_request(
             Some(h) => h,
             None => anyhow::bail!("http_request input is invalid: {http_req_offset}"),
         };
+        data.free(handle)?;
         let req: extism_manifest::HttpRequest = serde_json::from_slice(data.memory_bytes(handle)?)?;
         output[0] = Val::I64(0);
         anyhow::bail!(
@@ -182,6 +200,7 @@ pub(crate) fn http_request(
             None => anyhow::bail!("invalid handle offset for http request: {http_req_offset}"),
         };
         let req: extism_manifest::HttpRequest = serde_json::from_slice(data.memory_bytes(handle)?)?;
+        data.memory_free(handle)?;
 
         let body_offset = args!(input, 1, i64) as u64;
 
@@ -235,6 +254,10 @@ pub(crate) fn http_request(
             r.call()
         };
 
+        if let Some(handle) = data.memory_handle(body_offset) {
+            data.memory_free(handle)?;
+        }
+
         let reader = match res {
             Ok(res) => {
                 data.http_status = res.status();
@@ -302,19 +325,21 @@ pub fn log(
 ) -> Result<(), Error> {
     let data: &mut CurrentPlugin = caller.data_mut();
 
+    let offset = args!(input, 0, i64) as u64;
+
     // 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 {
+        if let Some(handle) = data.memory_handle(offset) {
+            data.memory_free(handle)?;
+        }
         return Ok(());
     }
 
-    let offset = args!(input, 0, i64) as u64;
-
     let handle = match data.memory_handle(offset) {
         Some(h) => h,
         None => anyhow::bail!("invalid handle offset for log message: {offset}"),
     };
-
     let id = data.id.to_string();
     let buf = data.memory_str(handle);
 
@@ -338,12 +363,16 @@ pub fn log(
         },
         Err(_) => tracing::error!(plugin = id, "unable to log message: {:?}", buf),
     }
+
+    data.memory_free(handle)?;
     Ok(())
 }
 
 /// Write to logs (warning)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_warn(
     caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -355,6 +384,8 @@ pub(crate) fn log_warn(
 /// Write to logs (info)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_info(
     caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -366,6 +397,8 @@ pub(crate) fn log_info(
 /// Write to logs (debug)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_debug(
     caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -377,6 +410,8 @@ pub(crate) fn log_debug(
 /// Write to logs (error)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_error(
     caller: Caller<CurrentPlugin>,
     input: &[Val],
@@ -388,6 +423,8 @@ pub(crate) fn log_error(
 /// Write to logs (trace)
 /// Params: i64 (offset)
 /// Returns: none
+/// **Note**: this function takes ownership of the handle passed in
+/// the caller should not `free` this value
 pub(crate) fn log_trace(
     caller: Caller<CurrentPlugin>,
     input: &[Val],