From 56c00df71036a3560a5f710f527fe7ece54eb665 Mon Sep 17 00:00:00 2001 From: Adam Joseph Date: Tue, 22 Nov 2022 19:42:06 -0800 Subject: feat(tvix/eval): use backtrace-on-stack-overflow crate The backtrace-on-stack-overflow create provides best-effort stack traces when a stack overflow happens. Since it's running on the (usually tiny) signal alternate stack this isn't easy. This is guarded by a new `backtrace_overflow` feature flag and never enabled (even if that feature is selected) for release builds. This is strictly for debugging; there's crazy unsafe voodoo in there. https://lib.rs/crates/backtrace-on-stack-overflow Example output: ``` Stack Overflow: 0: backtrace_on_stack_overflow::handle_sigsegv at /home/amjoseph/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-on-stack-overflow-0.2.0/src/lib.rs:93:40 1: 2: __rust_probestack 3: tvix_eval::vm::VM::run_op at src/vm.rs:399 4: tvix_eval::vm::VM::run at src/vm.rs:388:23 5: tvix_eval::vm::VM::enter_frame at src/vm.rs:360:22 6: tvix_eval::value::thunk::Thunk::force at src/value/thunk.rs:116:25 7: tvix_eval::vm::VM::run_op at src/vm.rs:801:37 8: tvix_eval::vm::VM::run at src/vm.rs:388:23 9: tvix_eval::vm::VM::enter_frame at src/vm.rs:360:22 10: tvix_eval::value::thunk::Thunk::force at src/value/thunk.rs:116:25 ... ``` Signed-off-by: Adam Joseph Change-Id: I1d8a2017f836be7bf91a2223e7adacb86fa1dbb2 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7354 Tested-by: BuildkiteCI Reviewed-by: tazjin --- tvix/eval/src/vm.rs | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'tvix/eval/src') diff --git a/tvix/eval/src/vm.rs b/tvix/eval/src/vm.rs index aa03ffd1eaae..41640a32b3c1 100644 --- a/tvix/eval/src/vm.rs +++ b/tvix/eval/src/vm.rs @@ -148,6 +148,15 @@ macro_rules! cmp_op { impl<'o> VM<'o> { pub fn new(nix_search_path: NixSearchPath, observer: &'o mut dyn RuntimeObserver) -> Self { + // Backtrace-on-stack-overflow is some seriously weird voodoo and + // very unsafe. This double-guard prevents it from accidentally + // being enabled on release builds. + #[cfg(debug_assertions)] + #[cfg(feature = "backtrace_overflow")] + unsafe { + backtrace_on_stack_overflow::enable(); + }; + Self { nix_search_path, observer, -- cgit 1.4.1