wasmer_compiler/engine/trap/
stack.rs

1use super::frame_info::{GlobalFrameInfo, FRAME_INFO};
2use backtrace::Backtrace;
3use wasmer_types::{FrameInfo, TrapCode};
4use wasmer_vm::Trap;
5
6/// Given a `Trap`, this function returns the Wasm trace and the trap code.
7pub fn get_trace_and_trapcode(trap: &Trap) -> (Vec<FrameInfo>, Option<TrapCode>) {
8    let info = FRAME_INFO.read().unwrap();
9    match &trap {
10        // A user error
11        Trap::User(_err) => (wasm_trace(&info, None, &Backtrace::new_unresolved()), None),
12        // A trap caused by the VM being Out of Memory
13        Trap::OOM { backtrace } => (wasm_trace(&info, None, backtrace), None),
14        // A trap caused by an error on the generated machine code for a Wasm function
15        Trap::Wasm {
16            pc,
17            signal_trap,
18            backtrace,
19        } => {
20            let trap_code = info
21                .lookup_trap_info(*pc)
22                .map_or(signal_trap.unwrap_or(TrapCode::StackOverflow), |info| {
23                    info.trap_code
24                });
25
26            (wasm_trace(&info, Some(*pc), backtrace), Some(trap_code))
27        }
28        // A trap triggered manually from the Wasmer runtime
29        Trap::Lib {
30            trap_code,
31            backtrace,
32        } => (wasm_trace(&info, None, backtrace), Some(*trap_code)),
33    }
34}
35
36fn wasm_trace(
37    info: &GlobalFrameInfo,
38    trap_pc: Option<usize>,
39    backtrace: &Backtrace,
40) -> Vec<FrameInfo> {
41    // Let's construct the trace
42    backtrace
43        .frames()
44        .iter()
45        .filter_map(|frame| {
46            let pc = frame.ip() as usize;
47            if pc == 0 {
48                None
49            } else {
50                // Note that we need to be careful about the pc we pass in here to
51                // lookup frame information. This program counter is used to
52                // translate back to an original source location in the origin wasm
53                // module. If this pc is the exact pc that the trap happened at,
54                // then we look up that pc precisely. Otherwise backtrace
55                // information typically points at the pc *after* the call
56                // instruction (because otherwise it's likely a call instruction on
57                // the stack). In that case we want to lookup information for the
58                // previous instruction (the call instruction) so we subtract one as
59                // the lookup.
60                let pc_to_lookup = if Some(pc) == trap_pc { pc } else { pc - 1 };
61                Some(pc_to_lookup)
62            }
63        })
64        .filter_map(|pc| info.lookup_frame_info(pc))
65        .collect::<Vec<_>>()
66}
wasmer_compiler/engine/trap/stack.rs

wasmer_compiler/engine/trap/
stack.rs
