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Provide filename/line number information in Trap (#2452)

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* Provide filename/line number information in `Trap`

This commit extends the `Trap` type and `Store` to retain DWARF debug
information found in a wasm file unconditionally, if it's present. This
then enables us to print filenames and line numbers which point back to
actual source code when a trap backtrace is printed. Additionally the
`FrameInfo` type has been souped up to return filename/line number
information as well.

The implementation here is pretty simplistic currently. The meat of all
the work happens in `gimli` and `addr2line`, and otherwise wasmtime is
just schlepping around bytes of dwarf debuginfo here and there!

The general goal here is to assist with debugging when using wasmtime
because filenames and line numbers are generally orders of magnitude
better even when you already have a stack trace. Another nicety here is
that backtraces will display inlined frames (learned through debug
information), improving the experience in release mode as well.

An example of this is that with this file:

```rust
fn main() {
    panic!("hello");
}
```

we get this stack trace:

```
$ rustc foo.rs --target wasm32-wasi -g
$ cargo run foo.wasm
    Finished dev [unoptimized + debuginfo] target(s) in 0.16s
     Running `target/debug/wasmtime foo.wasm`
thread 'main' panicked at 'hello', foo.rs:2:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Error: failed to run main module `foo.wasm`

Caused by:
    0: failed to invoke command default
    1: wasm trap: unreachable
       wasm backtrace:
           0: 0x6c1c - panic_abort::__rust_start_panic::abort::h2d60298621b1ccbf
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/panic_abort/src/lib.rs:77:17
                     - __rust_start_panic
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/panic_abort/src/lib.rs:32:5
           1: 0x68c7 - rust_panic
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panicking.rs:626:9
           2: 0x65a1 - std::panicking::rust_panic_with_hook::h2345fb0909b53e12
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panicking.rs:596:5
           3: 0x1436 - std::panicking::begin_panic::{{closure}}::h106f151a6db8c8fb
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panicking.rs:506:9
           4:  0xda8 - std::sys_common::backtrace::__rust_end_short_backtrace::he55aa13f22782798
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/sys_common/backtrace.rs:153:18
           5: 0x1324 - std::panicking::begin_panic::h1727e7d1d719c76f
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panicking.rs:505:12
           6:  0xfde - foo::main::h2db1313a64510850
                           at /Users/acrichton/code/wasmtime/foo.rs:2:5
           7: 0x11d5 - core::ops::function::FnOnce::call_once::h20ee1cc04aeff1fc
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/ops/function.rs:227:5
           8:  0xddf - std::sys_common::backtrace::__rust_begin_short_backtrace::h054493e41e27e69c
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/sys_common/backtrace.rs:137:18
           9: 0x1d5a - std::rt::lang_start::{{closure}}::hd83784448d3fcb42
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/rt.rs:66:18
          10: 0x69d8 - core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &F>::call_once::h564d3dad35014917
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/core/src/ops/function.rs:259:13
                     - std::panicking::try::do_call::hdca4832ace5a8603
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panicking.rs:381:40
                     - std::panicking::try::ha8624a1a6854b456
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panicking.rs:345:19
                     - std::panic::catch_unwind::h71421f57cf2bc688
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/panic.rs:382:14
                     - std::rt::lang_start_internal::h260050c92cd470af
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/rt.rs:51:25
          11: 0x1d0c - std::rt::lang_start::h0b4bcf3c5e498224
                           at /rustc/7eac88abb2e57e752f3302f02be5f3ce3d7adfb4/library/std/src/rt.rs:65:5
          12:  0xffc - <unknown>!__original_main
          13:  0x393 - __muloti4
                           at /cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.35/src/macros.rs:269
```

This is relatively noisy by default but there's filenames and line
numbers! Additionally frame 10 can be seen to have lots of frames
inlined into it. All information is always available to the embedder but
we could try to handle the `__rust_begin_short_backtrace` and
`__rust_end_short_backtrace` markers to trim the backtrace by default as
well.

The only gotcha here is that it looks like `__muloti4` is out of place.
That's because the libc that Rust ships with doesn't have dwarf
information, although I'm not sure why we land in that function for
symbolizing it...

* Add a configuration switch for debuginfo

* Control debuginfo by default with `WASM_BACKTRACE_DETAILS`

* Try cpp_demangle on demangling as well

* Rename to WASMTIME_BACKTRACE_DETAILS
This commit is contained in:
Alex Crichton
2020-12-01 16:56:23 -06:00
committed by GitHub
parent 88a8a8993a
commit 51c1d4bbd6
16 changed files with 568 additions and 62 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
crates/environ/src/module_environ.rs
View File

@@ -62,6 +62,10 @@ pub struct ModuleTranslation<'data> {
/// this module.
pub submodules: PrimaryMap<ModuleIndex, usize>,
/// Set if debuginfo was found but it was not parsed due to `Tunables`
/// configuration.
pub has_unparsed_debuginfo: bool,
code_index: u32,
}
@@ -81,8 +85,8 @@ pub struct DebugInfoData<'a> {
pub wasm_file: WasmFileInfo,
debug_loc: gimli::DebugLoc<Reader<'a>>,
debug_loclists: gimli::DebugLocLists<Reader<'a>>,
debug_ranges: gimli::DebugRanges<Reader<'a>>,
debug_rnglists: gimli::DebugRngLists<Reader<'a>>,
pub debug_ranges: gimli::DebugRanges<Reader<'a>>,
pub debug_rnglists: gimli::DebugRngLists<Reader<'a>>,
}
#[allow(missing_docs)]
@@ -152,9 +156,11 @@ impl<'data> ModuleEnvironment<'data> {
}
fn register_dwarf_section(&mut self, name: &str, data: &'data [u8]) {
if !self.tunables.debug_info {
if !self.tunables.generate_native_debuginfo && !self.tunables.parse_wasm_debuginfo {
self.result.has_unparsed_debuginfo = true;
return;
}
if !name.starts_with(".debug_") {
return;
}
@@ -493,7 +499,7 @@ impl<'data> cranelift_wasm::ModuleEnvironment<'data> for ModuleEnvironment<'data
validator: FuncValidator<ValidatorResources>,
body: FunctionBody<'data>,
) -> WasmResult<()> {
if self.tunables.debug_info {
if self.tunables.generate_native_debuginfo {
let func_index = self.result.code_index + self.result.module.num_imported_funcs as u32;
let func_index = FuncIndex::from_u32(func_index);
let sig_index = self.result.module.functions[func_index];
@@ -563,7 +569,7 @@ impl<'data> cranelift_wasm::ModuleEnvironment<'data> for ModuleEnvironment<'data
fn declare_module_name(&mut self, name: &'data str) {
self.result.module.name = Some(name.to_string());
if self.tunables.debug_info {
if self.tunables.generate_native_debuginfo {
self.result.debuginfo.name_section.module_name = Some(name);
}
}
@@ -573,7 +579,7 @@ impl<'data> cranelift_wasm::ModuleEnvironment<'data> for ModuleEnvironment<'data
.module
.func_names
.insert(func_index, name.to_string());
if self.tunables.debug_info {
if self.tunables.generate_native_debuginfo {
self.result
.debuginfo
.name_section
@@ -583,7 +589,7 @@ impl<'data> cranelift_wasm::ModuleEnvironment<'data> for ModuleEnvironment<'data
}
fn declare_local_name(&mut self, func_index: FuncIndex, local: u32, name: &'data str) {
if self.tunables.debug_info {
if self.tunables.generate_native_debuginfo {
self.result
.debuginfo
.name_section

10
crates/environ/src/tunables.rs
View File

@@ -10,8 +10,11 @@ pub struct Tunables {
/// The size in bytes of the offset guard for dynamic heaps.
pub dynamic_memory_offset_guard_size: u64,
/// Whether or not to generate DWARF debug information.
pub debug_info: bool,
/// Whether or not to generate native DWARF debug information.
pub generate_native_debuginfo: bool,
/// Whether or not to retain DWARF sections in compiled modules.
pub parse_wasm_debuginfo: bool,
/// Whether or not to enable the ability to interrupt wasm code dynamically.
///
@@ -51,7 +54,8 @@ impl Default for Tunables {
/// wasting too much memory.
dynamic_memory_offset_guard_size: 0x1_0000,
debug_info: false,
generate_native_debuginfo: false,
parse_wasm_debuginfo: true,
interruptable: false,
}
}