Merge pull request #70 from dpfens/change_entrypoint

Add WasmEntryPoint directive to change/specify entrypoints

Author: gzurl

mod_wasm/httpd.conf

@@ -187,6 +187,7 @@ LoadModule wasm_module modules/mod_wasm.so
     <Location /hello-wasm>
         SetHandler wasm-handler
         WasmModule /usr/local/apache2/wasm_modules/rust-wasm/hello_wasm.wasm
+        WasmEntryPoint _start
     </Location>
 
     ###################################################################

mod_wasm/modules/wasm/mod_wasm.c

@@ -435,6 +435,7 @@ static void register_hooks(apr_pool_t *p)
 #define WASM_DIRECTIVE_WASMMAPDIR           "WasmMapDir"
 #define WASM_DIRECTIVE_WASMENABLECGI        "WasmEnableCGI"
 #define WASM_DIRECTIVE_WASMMAPCGIFILENAMES  "WasmMapCGIFileNames"
+#define WASM_DIRECTIVE_WASMENTRYPOINT       "WasmEntryPoint"
 
 static const char *wasm_directive_WasmModule(cmd_parms *cmd, void *mconfig, const char *word1)
 {
@@ -518,6 +519,17 @@ static const char *wasm_directive_WasmMapCGIFileNames(cmd_parms *cmd, void *mcon
     return NULL;
 }
 
+static const char *wasm_directive_WasmEntryPoint(cmd_parms *cmd, void *mconfig, const char *entrypoint)
+{
+    x_cfg *cfg = (x_cfg *) mconfig;
+    int ret = wasm_config_entrypoint_set(cfg->loc, entrypoint);
+    if ( ret != OK )
+        ap_log_error(APLOG_MARK, APLOG_ERR, ret, NULL,
+            "wasm_directive_WasmEntryPoint() - ERROR! Couldn't set entrypoint '%s' to Wasm config '%s'!", entrypoint, cfg->loc);
+
+    return NULL;
+}
+
 /*
  * List of directives specific to our module.
  */
@@ -542,7 +554,7 @@ static const command_rec directives[] =
         wasm_directive_WasmEnv,
         NULL,
         OR_OPTIONS,
-        "Set environtment variable for the Wasm Module"
+        "Set environment variable for the Wasm Module"
     ),
     AP_INIT_TAKE1(
         WASM_DIRECTIVE_WASMDIR,
@@ -572,6 +584,13 @@ static const command_rec directives[] =
         OR_OPTIONS,
         "Whether SCRIPT_FILENAME should be mapped based on WasmMapDir mounts when running as a CGI"
     ),
+    AP_INIT_TAKE1(
+        WASM_DIRECTIVE_WASMENTRYPOINT,
+        wasm_directive_WasmEntryPoint,
+        NULL,
+        OR_OPTIONS,
+        "Set entrypoint for the Wasm Module"
+    ),
     {NULL}
 };
 

wasm_runtime/src/c_api.rs

@@ -396,6 +396,38 @@ pub extern "C" fn wasm_executionctx_stdin_set(executionctx_id: *const c_char, bu
 }
 
 
+/// Set the entrypoint for loaded Wasm Module to an existing Wasm Config.
+///
+/// Wasm config must have been previously created.
+///
+/// In case of error, the reason is printed to stderr and returns -1.
+/// Otherwise, it returns 0.
+/// 
+/// Due to String management differences between C and Rust, this function uses `unsafe {}` code.
+/// So `config_id` and `entrypoint` must be a valid pointer to a null-terminated C char array. Otherwise, code might panic.
+/// In addition, `config_id` and `entrypoint` must contain valid ASCII chars that can be converted into UTF-8 encoding.
+///
+/// # Examples (C Code)
+///
+/// ```
+/// wasm_config_entrypoint_set("Drupal", "_start");
+/// wasm_config_entrypoint_set("WordPress", "run");
+/// ```
+#[no_mangle]
+pub extern "C" fn wasm_config_entrypoint_set(config_id: *const c_char, entrypoint: *const c_char) -> c_int {
+    let config_id_str = const_c_char_to_str(config_id);
+    let entrypoint_str = const_c_char_to_str(entrypoint);
+
+    match WasmConfig::set_entrypoint_for_config(config_id_str, entrypoint_str) {
+        Ok(_) => 0,
+        Err(e) => {
+            eprintln!("ERROR! C-API: Couldn't set entrypoint for Wasm config \"{}\": {}", config_id_str, e);
+            -1
+        }
+    } 
+}
+
+
 /// Run the given Wasm execution context
 ///
 /// In case of error, the reason is printed to stderr and returns -1.
@@ -638,4 +670,17 @@ mod tests {
         // assert
         assert_eq!(val, 0);
     }
+
+    #[test]
+    fn wasm_config_entrypoint_set_general() {
+        let config_id = CString::new("test_config").unwrap();
+
+        // test
+        wasm_config_create(config_id.as_ptr());
+        let entrypoint = CString::new("run").unwrap();
+        let val = wasm_config_entrypoint_set(config_id.as_ptr(), entrypoint.as_ptr());
+
+        // asserts
+        assert_eq!(val, 0);
+    }
 }

wasm_runtime/src/config.rs

@@ -19,6 +19,7 @@ use path_slash::PathBufExt as _;
 pub struct WasmConfig {
     pub id:           String,
     pub module_id:    String,
+    pub entrypoint:   String,
     pub wasi_args:    Vec<String>,
     pub wasi_envs:    Vec<(String, String)>,
     pub wasi_dirs:    Vec<String>,
@@ -59,6 +60,7 @@ impl WasmConfig {
             wasi_envs:    Vec::new(),
             wasi_dirs:    Vec::new(),
             wasi_mapdirs: Vec::new(),
+            entrypoint:   "_start".to_string()   // defaults to "_start" 
         };
 
         // insert created WasmConfig object into the HashMap
@@ -212,6 +214,32 @@ impl WasmConfig {
         Ok(())
     }
 
+    // Set the entrypoint for a loaded Wasm Module to an existing Wasm config
+    ///
+    /// It checks for wrong `config_id`
+    /// Returns Result<(), String>, so that in case of error the String will contain the reason.
+    /// 
+    pub fn set_entrypoint_for_config(config_id: &str, entrypoint: &str) -> Result<(), String> {
+
+        // get write access to the WasmConfig HashMap
+        let mut configs = WASM_RUNTIME_CONFIGS.write()
+            .expect("ERROR! Poisoned RwLock WASM_RUNTIME_CONFIGS on write()");
+
+        // check for existing config_id in the loaded configurations
+        let wasm_config = match configs.get_mut(config_id) {
+            Some(c) => c,
+            None => {
+                let error_msg = format!("Wasm config \'{}\' not found while setting entrypoint \'{}\'", config_id, entrypoint);
+                return Err(error_msg);
+            }
+        };
+
+        // setting module in Wasm config
+        wasm_config.entrypoint = entrypoint.to_string();
+
+        Ok(())
+    }
+
     pub fn get_mapped_path(config_id: &str, path: &str) -> Result<Option<String>, String> {
         let configs = WASM_RUNTIME_CONFIGS
             .read()

wasm_runtime/src/execution_ctx.rs

@@ -28,6 +28,7 @@ pub struct WasmExecutionCtx {
     pub wasi_mapdirs: Vec<(String, String)>,
     pub wasi_stdin:   Vec<u8>,
     pub wasi_stdout:  Arc<RwLock<Vec<u8>>>,
+    pub entrypoint:   String
 }
 
 impl WasmExecutionCtx {
@@ -65,6 +66,7 @@ impl WasmExecutionCtx {
             wasi_mapdirs: wasm_config.wasi_mapdirs.clone(),
             wasi_stdin:   Vec::new(),
             wasi_stdout:  Arc::new(RwLock::new(Vec::new())),
+            entrypoint:   wasm_config.entrypoint.clone()
         };
 
         Self::try_insert(wasm_executionctx)
@@ -154,8 +156,8 @@ impl WasmExecutionCtx {
             }
         };
 
-        // invoke default "_start" function for the given Wasm execution context
-        wasm_engine::invoke_wasm_function(&wasm_executionctx, "_start")?;
+        // invoke entrypoint for the given Wasm execution context (default is "_start")
+        wasm_engine::invoke_wasm_function(&wasm_executionctx, &wasm_executionctx.entrypoint)?;
 
         // read stdout from the Wasm execution context and return it
         let wasm_module_stdout = Self::read_stdout(&wasm_executionctx);