elf_runner/
crash_handler.rs

1// Copyright 2021 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use crate::crash_info::{ComponentCrashInfo, CrashRecords};
6use crate::error::ExceptionError;
7use fuchsia_async as fasync;
8use futures::TryStreamExt;
9use log::error;
10use moniker::Moniker;
11use zx::{self as zx, AsHandleRef};
12
13// Registers with the job to catch exceptions raised by it. Whenever we see an exception from this
14// job, record that the crash happened, and inform zircon that it should proceed to the next crash
15// handler. No actual handling of the crash occurs here, we merely save some data on it.
16pub fn run_exceptions_server(
17    component_job: &zx::Job,
18    moniker: Moniker,
19    resolved_url: String,
20    crash_records: CrashRecords,
21) -> Result<(), zx::Status> {
22    let mut task_exceptions_stream =
23        task_exceptions::ExceptionsStream::register_with_task(component_job)?;
24    fasync::Task::spawn(async move {
25        loop {
26            match task_exceptions_stream.try_next().await {
27                Ok(Some(exception_info)) => {
28                    if let Err(error) = record_exception(
29                        resolved_url.clone(),
30                        moniker.clone(),
31                        exception_info,
32                        &crash_records,
33                    )
34                    .await
35                    {
36                        error!(url:% = resolved_url, error:?; "failed to handle exception");
37                    }
38                }
39                Ok(None) => break,
40                Err(error) => {
41                    error!(
42                        url:% = resolved_url, error:?;
43                        "failed to read message stream for fuchsia.sys2.CrashIntrospect",
44                    );
45                    break;
46                }
47            }
48        }
49    })
50    .detach();
51    Ok(())
52}
53
54async fn record_exception(
55    resolved_url: String,
56    moniker: Moniker,
57    exception_info: task_exceptions::ExceptionInfo,
58    crash_records: &CrashRecords,
59) -> Result<(), ExceptionError> {
60    // An exception has occurred, record information about the crash so that it may be retrieved
61    // later.
62    let thread_koid = exception_info.thread.get_koid().map_err(ExceptionError::GetThreadKoid)?;
63    crash_records.add_report(thread_koid, ComponentCrashInfo { url: resolved_url, moniker }).await;
64
65    // We've stored all the information we need, so mark the exception handle such that the next
66    // exception handler should be attempted.
67    exception_info
68        .exception_handle
69        .set_exception_state(&zx::sys::ZX_EXCEPTION_STATE_TRY_NEXT)
70        .map_err(ExceptionError::SetState)?;
71
72    // Returning drops exception_info.exception_handle, which allows zircon to proceed with
73    // exception handling.
74    Ok(())
75}
76
77#[cfg(test)]
78mod tests {
79    use super::*;
80    use anyhow::{Context as _, Error};
81    use fuchsia_component::client as fclient;
82    use zx::HandleBased;
83    use {fidl_fuchsia_io as fio, fidl_fuchsia_process as fprocess, fuchsia_runtime as fruntime};
84
85    #[fuchsia::test]
86    async fn crash_test() -> Result<(), Error> {
87        let crash_records = CrashRecords::new();
88        let url = "example://component#url".to_string();
89        let moniker = Moniker::try_from(["a"]).unwrap();
90
91        let child_job =
92            fruntime::job_default().create_child_job().context("failed to create child job")?;
93
94        run_exceptions_server(&child_job, moniker.clone(), url.clone(), crash_records.clone())?;
95
96        // Connect to the process launcher
97        let launcher_proxy = fclient::connect_to_protocol::<fprocess::LauncherMarker>()?;
98
99        // Set up a new library loader and provide it to the loader service
100        let (ll_client_chan, ll_service_chan) = zx::Channel::create();
101        library_loader::start(
102            fuchsia_fs::directory::open_in_namespace(
103                "/pkg/lib",
104                fio::PERM_READABLE | fio::PERM_EXECUTABLE,
105            )?,
106            ll_service_chan,
107        );
108        let handle_infos = vec![fprocess::HandleInfo {
109            handle: ll_client_chan.into_handle(),
110            id: fruntime::HandleInfo::new(fruntime::HandleType::LdsvcLoader, 0).as_raw(),
111        }];
112        launcher_proxy.add_handles(handle_infos).context("failed to add loader service handle")?;
113
114        // Load the executable into a vmo
115        let executable_file_proxy = fuchsia_fs::file::open_in_namespace(
116            "/pkg/bin/panic_on_start",
117            fio::PERM_READABLE | fio::PERM_EXECUTABLE,
118        )?;
119        let vmo = executable_file_proxy
120            .get_backing_memory(fio::VmoFlags::READ | fio::VmoFlags::EXECUTE)
121            .await?
122            .map_err(zx::Status::from_raw)
123            .context("failed to get VMO of executable")?;
124
125        // Create the process, but don't start it yet
126        let child_job_dup = child_job.duplicate_handle(zx::Rights::SAME_RIGHTS)?;
127        let launch_info = fprocess::LaunchInfo {
128            executable: vmo,
129            job: child_job_dup,
130            name: "panic_on_start".to_string(),
131        };
132        let (status, process_start_data) = launcher_proxy
133            .create_without_starting(launch_info)
134            .await
135            .context("failed to launch process")?;
136        zx::Status::ok(status).context("error returned by process launcher")?;
137        let process_start_data = process_start_data.unwrap();
138
139        // Get the thread's koid, so that we know which thread to look for in the records once it
140        // crashes
141        let thread_koid = process_start_data.thread.get_koid()?;
142
143        // We've got the thread koid, so now we can actually start the process
144        process_start_data.process.start(
145            &process_start_data.thread,
146            // Some of these values are u64, but this function is expecting usize
147            process_start_data.entry.try_into().unwrap(),
148            process_start_data.stack.try_into().unwrap(),
149            process_start_data.bootstrap.into_handle(),
150            process_start_data.vdso_base.try_into().unwrap(),
151        )?;
152
153        // The process panics when it starts, so wait for the job to be killed
154        fasync::OnSignals::new(&process_start_data.process, zx::Signals::PROCESS_TERMINATED)
155            .await?;
156        let crash_info = crash_records
157            .take_report(&thread_koid)
158            .await
159            .expect("crash_records is missing crash information");
160        assert_eq!(ComponentCrashInfo { url, moniker }, crash_info);
161        Ok(())
162    }
163}
elf_runner/crash_handler.rs

elf_runner/
crash_handler.rs
