add basic coredump generation

docs/en/examples-coredump.md

@@ -0,0 +1,62 @@
+# Using Wasm coredump
+
+The following steps describe how to debug using Wasm coredump in Wasmer:
+
+1. Compile your WebAssembly with debug info enabled; for example: 
+
+    ```sh
+    $ rustc foo.rs --target=wasm32-wasi -C debuginfo=2
+    ```
+
+<details>
+    <summary>foo.rs</summary>
+
+    fn c(v: usize) {
+        a(v - 3);
+    }
+
+    fn b(v: usize) {
+        c(v - 3);
+    }
+
+    fn a(v: usize) {
+        b(v - 3);
+    }
+
+    pub fn main() {
+        a(10);
+    }
+</details>
+
+2. Run with Wasmer and Wasm coredump enabled:
+
+    ```sh
+    $ wasmer --coredump-on-trap=/tmp/coredump foo.wasm
+
+    thread 'main' panicked at 'attempt to subtract with overflow', foo.rs:10:7
+    note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+    Error: failed to run main module `foo.wasm`
+
+    Caused by:
+        0: Core dumped at /tmp/coredump
+        1: failed to invoke command default
+        2: error while executing at wasm backtrace:
+                    ...
+    ```
+
+3. Use [wasmgdb] to debug:
+    ```sh
+    $ wasmgdb foo.wasm /tmp/coredump
+
+    wasmgdb> bt
+    ...
+    #13     000175 as panic () at library/core/src/panicking.rs
+    #12     000010 as a (v=???) at /path/to/foo.rs
+    #11     000009 as c (v=???) at /path/to/foo.rs
+    #10     000011 as b (v=???) at /path/to/foo.rs
+    #9      000010 as a (v=???) at /path/to/foo.rs
+    #8      000012 as main () at /path/to/foo.rs
+    ...
+    ```
+
+[wasmgdb]: https://crates.io/crates/wasmgdb

lib/cli/Cargo.toml

@@ -91,6 +91,7 @@ rpassword = "7.2.0"
 pathdiff = "0.2.1"
 sha2 = "0.10.6"
 object = "0.30.0"
+wasm-coredump-builder = { version = "0.1.11" }
 
 [build-dependencies]
 chrono = { version = "^0.4", default-features = false, features = [ "std", "clock" ] }

lib/cli/src/commands/run.rs

@@ -8,6 +8,8 @@ use crate::suggestions::suggest_function_exports;
 use crate::warning;
 use anyhow::{anyhow, Context, Result};
 use clap::Parser;
+use std::fs::File;
+use std::io::Write;
 use std::ops::Deref;
 use std::path::PathBuf;
 #[cfg(feature = "cache")]
@@ -89,6 +91,10 @@ pub struct RunWithoutFile {
     #[clap(long = "verbose")]
     pub(crate) verbose: Option<u8>,
 
+    /// Enable coredump generation after a WebAssembly trap.
+    #[clap(name = "COREDUMP PATH", long = "coredump-on-trap", parse(from_os_str))]
+    coredump_on_trap: Option<PathBuf>,
+
     /// Application arguments
     #[clap(value_name = "ARGS")]
     pub(crate) args: Vec<String>,
@@ -154,7 +160,7 @@ impl RunWithPathBuf {
         if self.debug {
             logging::set_up_logging(self_clone.verbose.unwrap_or(0)).unwrap();
         }
-        self_clone.inner_execute().with_context(|| {
+        let invoke_res = self_clone.inner_execute().with_context(|| {
             format!(
                 "failed to run `{}`{}",
                 self_clone.path.display(),
@@ -164,7 +170,23 @@ impl RunWithPathBuf {
                     ""
                 }
             )
-        })
+        });
+
+        if let Err(err) = invoke_res {
+            if let Some(coredump_path) = self.coredump_on_trap.as_ref() {
+                let source_name = self.path.to_str().unwrap_or_else(|| "unknown");
+                if let Err(coredump_err) = generate_coredump(&err, &source_name, &coredump_path) {
+                    eprintln!("warning: coredump failed to generate: {}", coredump_err);
+                    Err(err)
+                } else {
+                    Err(err.context(format!("core dumped at {}", coredump_path.display())))
+                }
+            } else {
+                Err(err)
+            }
+        } else {
+            invoke_res
+        }
     }
 
     fn inner_module_run(&self, store: &mut Store, instance: Instance) -> Result<()> {
@@ -632,3 +654,47 @@ impl Run {
         bail!("binfmt_misc is only available on linux.")
     }
 }
+
+fn generate_coredump(
+    err: &anyhow::Error,
+    source_name: &str,
+    coredump_path: &PathBuf,
+) -> Result<()> {
+    let err = err
+        .downcast_ref::<wasmer::RuntimeError>()
+        .ok_or_else(|| anyhow!("no runtime error found to generate coredump with"))?;
+
+    let mut coredump_builder =
+        wasm_coredump_builder::CoredumpBuilder::new().executable_name(source_name);
+
+    {
+        let mut thread_builder = wasm_coredump_builder::ThreadBuilder::new().thread_name("main");
+
+        for frame in err.trace() {
+            let coredump_frame = wasm_coredump_builder::FrameBuilder::new()
+                .codeoffset(frame.func_offset() as u32)
+                .funcidx(frame.func_index())
+                .build();
+            thread_builder.add_frame(coredump_frame);
+        }
+
+        coredump_builder.add_thread(thread_builder.build());
+    }
+
+    let coredump = coredump_builder
+        .serialize()
+        .map_err(|err| anyhow!("failed to serialize coredump: {}", err))?;
+
+    let mut f = File::create(coredump_path).context(format!(
+        "failed to create file at `{}`",
+        coredump_path.display()
+    ))?;
+    f.write_all(&coredump).with_context(|| {
+        format!(
+            "failed to write coredump file at `{}`",
+            coredump_path.display()
+        )
+    })?;
+
+    Ok(())
+}