diagnostics.rs

use std::fmt::{self, Write};
use std::num::NonZeroU64;

use log::trace;

use rustc_errors::DiagnosticMessage;
use rustc_span::{SpanData, Symbol, DUMMY_SP};
use rustc_target::abi::{Align, Size};

use crate::borrow_tracker::stacked_borrows::diagnostics::TagHistory;
use crate::borrow_tracker::tree_borrows::diagnostics as tree_diagnostics;
use crate::*;

/// Details of premature program termination.
pub enum TerminationInfo {
    Exit {
        code: i64,
        leak_check: bool,
    },
    Abort(String),
    UnsupportedInIsolation(String),
    StackedBorrowsUb {
        msg: String,
        help: Vec<String>,
        history: Option<TagHistory>,
    },
    TreeBorrowsUb {
        title: String,
        details: Vec<String>,
        history: tree_diagnostics::HistoryData,
    },
    Int2PtrWithStrictProvenance,
    Deadlock,
    MultipleSymbolDefinitions {
        link_name: Symbol,
        first: SpanData,
        first_crate: Symbol,
        second: SpanData,
        second_crate: Symbol,
    },
    SymbolShimClashing {
        link_name: Symbol,
        span: SpanData,
    },
    DataRace {
        involves_non_atomic: bool,
        ptr: Pointer<AllocId>,
        op1: RacingOp,
        op2: RacingOp,
        extra: Option<&'static str>,
    },
}

pub struct RacingOp {
    pub action: String,
    pub thread_info: String,
    pub span: SpanData,
}

impl fmt::Display for TerminationInfo {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        use TerminationInfo::*;
        match self {
            Exit { code, .. } => write!(f, "the evaluated program completed with exit code {code}"),
            Abort(msg) => write!(f, "{msg}"),
            UnsupportedInIsolation(msg) => write!(f, "{msg}"),
            Int2PtrWithStrictProvenance =>
                write!(
                    f,
                    "integer-to-pointer casts and `ptr::from_exposed_addr` are not supported with `-Zmiri-strict-provenance`"
                ),
            StackedBorrowsUb { msg, .. } => write!(f, "{msg}"),
            TreeBorrowsUb { title, .. } => write!(f, "{title}"),
            Deadlock => write!(f, "the evaluated program deadlocked"),
            MultipleSymbolDefinitions { link_name, .. } =>
                write!(f, "multiple definitions of symbol `{link_name}`"),
            SymbolShimClashing { link_name, .. } =>
                write!(f, "found `{link_name}` symbol definition that clashes with a built-in shim",),
            DataRace { involves_non_atomic, ptr, op1, op2, .. } =>
                write!(
                    f,
                    "{} detected between (1) {} on {} and (2) {} on {} at {ptr:?}. (2) just happened here",
                    if *involves_non_atomic { "Data race" } else { "Race condition" },
                    op1.action,
                    op1.thread_info,
                    op2.action,
                    op2.thread_info
                ),
        }
    }
}

impl fmt::Debug for TerminationInfo {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{self}")
    }
}

impl MachineStopType for TerminationInfo {
    fn diagnostic_message(&self) -> DiagnosticMessage {
        self.to_string().into()
    }
    fn add_args(
        self: Box<Self>,
        _: &mut dyn FnMut(
            std::borrow::Cow<'static, str>,
            rustc_errors::DiagnosticArgValue<'static>,
        ),
    ) {
    }
}

/// Miri specific diagnostics
pub enum NonHaltingDiagnostic {
    /// (new_tag, new_perm, (alloc_id, base_offset, orig_tag))
    ///
    /// new_perm is `None` for base tags.
    CreatedPointerTag(NonZeroU64, Option<String>, Option<(AllocId, AllocRange, ProvenanceExtra)>),
    /// This `Item` was popped from the borrow stack. The string explains the reason.
    PoppedPointerTag(Item, String),
    CreatedCallId(CallId),
    CreatedAlloc(AllocId, Size, Align, MemoryKind<MiriMemoryKind>),
    FreedAlloc(AllocId),
    RejectedIsolatedOp(String),
    ProgressReport {
        block_count: u64, // how many basic blocks have been run so far
    },
    Int2Ptr {
        details: bool,
    },
    WeakMemoryOutdatedLoad,
}

/// Level of Miri specific diagnostics
pub enum DiagLevel {
    Error,
    Warning,
    Note,
}

/// Attempts to prune a stacktrace to omit the Rust runtime, and returns a bool indicating if any
/// frames were pruned. If the stacktrace does not have any local frames, we conclude that it must
/// be pointing to a problem in the Rust runtime itself, and do not prune it at all.
pub fn prune_stacktrace<'tcx>(
    mut stacktrace: Vec<FrameInfo<'tcx>>,
    machine: &MiriMachine<'_, 'tcx>,
) -> (Vec<FrameInfo<'tcx>>, bool) {
    match machine.backtrace_style {
        BacktraceStyle::Off => {
            // Remove all frames marked with `caller_location` -- that attribute indicates we
            // usually want to point at the caller, not them.
            stacktrace.retain(|frame| !frame.instance.def.requires_caller_location(machine.tcx));
            // Retain one frame so that we can print a span for the error itself
            stacktrace.truncate(1);
            (stacktrace, false)
        }
        BacktraceStyle::Short => {
            let original_len = stacktrace.len();
            // Only prune frames if there is at least one local frame. This check ensures that if
            // we get a backtrace that never makes it to the user code because it has detected a
            // bug in the Rust runtime, we don't prune away every frame.
            let has_local_frame = stacktrace.iter().any(|frame| machine.is_local(frame));
            if has_local_frame {
                // Remove all frames marked with `caller_location` -- that attribute indicates we
                // usually want to point at the caller, not them.
                stacktrace
                    .retain(|frame| !frame.instance.def.requires_caller_location(machine.tcx));

                // This is part of the logic that `std` uses to select the relevant part of a
                // backtrace. But here, we only look for __rust_begin_short_backtrace, not
                // __rust_end_short_backtrace because the end symbol comes from a call to the default
                // panic handler.
                stacktrace = stacktrace
                    .into_iter()
                    .take_while(|frame| {
                        let def_id = frame.instance.def_id();
                        let path = machine.tcx.def_path_str(def_id);
                        !path.contains("__rust_begin_short_backtrace")
                    })
                    .collect::<Vec<_>>();

                // After we prune frames from the bottom, there are a few left that are part of the
                // Rust runtime. So we remove frames until we get to a local symbol, which should be
                // main or a test.
                // This len check ensures that we don't somehow remove every frame, as doing so breaks
                // the primary error message.
                while stacktrace.len() > 1
                    && stacktrace.last().map_or(false, |frame| !machine.is_local(frame))
                {
                    stacktrace.pop();
                }
            }
            let was_pruned = stacktrace.len() != original_len;
            (stacktrace, was_pruned)
        }
        BacktraceStyle::Full => (stacktrace, false),
    }
}

/// Emit a custom diagnostic without going through the miri-engine machinery.
///
/// Returns `Some` if this was regular program termination with a given exit code and a `bool` indicating whether a leak check should happen; `None` otherwise.
pub fn report_error<'tcx, 'mir>(
    ecx: &InterpCx<'mir, 'tcx, MiriMachine<'mir, 'tcx>>,
    e: InterpErrorInfo<'tcx>,
) -> Option<(i64, bool)> {
    use InterpError::*;
    use UndefinedBehaviorInfo::*;

    let mut msg = vec![];

    let (title, helps) = if let MachineStop(info) = e.kind() {
        let info = info.downcast_ref::<TerminationInfo>().expect("invalid MachineStop payload");
        use TerminationInfo::*;
        let title = match info {
            Exit { code, leak_check } => return Some((*code, *leak_check)),
            Abort(_) => Some("abnormal termination"),
            UnsupportedInIsolation(_) | Int2PtrWithStrictProvenance =>
                Some("unsupported operation"),
            StackedBorrowsUb { .. } | TreeBorrowsUb { .. } | DataRace { .. } =>
                Some("Undefined Behavior"),
            Deadlock => Some("deadlock"),
            MultipleSymbolDefinitions { .. } | SymbolShimClashing { .. } => None,
        };
        #[rustfmt::skip]
        let helps = match info {
            UnsupportedInIsolation(_) =>
                vec![
                    (None, format!("pass the flag `-Zmiri-disable-isolation` to disable isolation;")),
                    (None, format!("or pass `-Zmiri-isolation-error=warn` to configure Miri to return an error code from isolated operations (if supported for that operation) and continue with a warning")),
                ],
            StackedBorrowsUb { help, history, .. } => {
                msg.extend(help.clone());
                let mut helps = vec![
                    (None, format!("this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental")),
                    (None, format!("see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information")),
                ];
                if let Some(TagHistory {created, invalidated, protected}) = history.clone() {
                    helps.push((Some(created.1), created.0));
                    if let Some((msg, span)) = invalidated {
                        helps.push((Some(span), msg));
                    }
                    if let Some((protector_msg, protector_span)) = protected {
                        helps.push((Some(protector_span), protector_msg));
                    }
                }
                helps
            },
            TreeBorrowsUb { title: _, details, history } => {
                let mut helps = vec![
                    (None, format!("this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental"))
                ];
                for m in details {
                    helps.push((None, m.clone()));
                }
                for event in history.events.clone() {
                    helps.push(event);
                }
                helps
            }
            MultipleSymbolDefinitions { first, first_crate, second, second_crate, .. } =>
                vec![
                    (Some(*first), format!("it's first defined here, in crate `{first_crate}`")),
                    (Some(*second), format!("then it's defined here again, in crate `{second_crate}`")),
                ],
            SymbolShimClashing { link_name, span } =>
                vec![(Some(*span), format!("the `{link_name}` symbol is defined here"))],
            Int2PtrWithStrictProvenance =>
                vec![(None, format!("use Strict Provenance APIs (https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance, https://crates.io/crates/sptr) instead"))],
            DataRace { op1, extra, .. } => {
                let mut helps = vec![(Some(op1.span), format!("and (1) occurred earlier here"))];
                if let Some(extra) = extra {
                    helps.push((None, format!("{extra}")));
                    helps.push((None, format!("see https://doc.rust-lang.org/nightly/std/sync/atomic/index.html#memory-model-for-atomic-accesses for more information about the Rust memory model")));
                }
                helps.push((None, format!("this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior")));
                helps.push((None, format!("see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information")));
                helps
            }
                ,
            _ => vec![],
        };
        (title, helps)
    } else {
        let title = match e.kind() {
            UndefinedBehavior(ValidationError(validation_err))
                if matches!(
                    validation_err.kind,
                    ValidationErrorKind::PointerAsInt { .. } | ValidationErrorKind::PartialPointer
                ) =>
            {
                ecx.handle_ice(); // print interpreter backtrace
                bug!("This validation error should be impossible in Miri: {}", ecx.format_error(e));
            }
            UndefinedBehavior(_) => "Undefined Behavior",
            ResourceExhaustion(_) => "resource exhaustion",
            Unsupported(
                // We list only the ones that can actually happen.
                UnsupportedOpInfo::Unsupported(_) | UnsupportedOpInfo::UnsizedLocal,
            ) => "unsupported operation",
            InvalidProgram(
                // We list only the ones that can actually happen.
                InvalidProgramInfo::AlreadyReported(_) | InvalidProgramInfo::Layout(..),
            ) => "post-monomorphization error",
            _ => {
                ecx.handle_ice(); // print interpreter backtrace
                bug!("This error should be impossible in Miri: {}", ecx.format_error(e));
            }
        };
        #[rustfmt::skip]
        let helps = match e.kind() {
            Unsupported(_) =>
                vec![(None, format!("this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support"))],
            UndefinedBehavior(AlignmentCheckFailed { .. })
                if ecx.machine.check_alignment == AlignmentCheck::Symbolic
            =>
                vec![
                    (None, format!("this usually indicates that your program performed an invalid operation and caused Undefined Behavior")),
                    (None, format!("but due to `-Zmiri-symbolic-alignment-check`, alignment errors can also be false positives")),
                ],
            UndefinedBehavior(info) => {
                let mut helps = vec![
                    (None, format!("this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior")),
                    (None, format!("see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information")),
                ];
                match info {
                    PointerUseAfterFree(alloc_id, _) | PointerOutOfBounds { alloc_id, .. } => {
                        if let Some(span) = ecx.machine.allocated_span(*alloc_id) {
                            helps.push((Some(span), format!("{:?} was allocated here:", alloc_id)));
                        }
                        if let Some(span) = ecx.machine.deallocated_span(*alloc_id) {
                            helps.push((Some(span), format!("{:?} was deallocated here:", alloc_id)));
                        }
                    }
                    AbiMismatchArgument { .. } | AbiMismatchReturn { .. } => {
                        helps.push((None, format!("this means these two types are not *guaranteed* to be ABI-compatible across all targets")));
                        helps.push((None, format!("if you think this code should be accepted anyway, please report an issue")));
                    }
                    _ => {},
                }
                helps
            }
            InvalidProgram(
                InvalidProgramInfo::AlreadyReported(_)
            ) => {
                // This got already reported. No point in reporting it again.
                return None;
            }
            _ =>
                vec![],
        };
        (Some(title), helps)
    };

    let stacktrace = ecx.generate_stacktrace();
    let (stacktrace, was_pruned) = prune_stacktrace(stacktrace, &ecx.machine);

    // We want to dump the allocation if this is `InvalidUninitBytes`. Since `format_error` consumes `e`, we compute the outut early.
    let mut extra = String::new();
    match e.kind() {
        UndefinedBehavior(InvalidUninitBytes(Some((alloc_id, access)))) => {
            writeln!(
                extra,
                "Uninitialized memory occurred at {alloc_id:?}{range:?}, in this allocation:",
                range = access.bad,
            )
            .unwrap();
            writeln!(extra, "{:?}", ecx.dump_alloc(*alloc_id)).unwrap();
        }
        _ => {}
    }

    msg.insert(0, ecx.format_error(e));

    report_msg(
        DiagLevel::Error,
        if let Some(title) = title { format!("{title}: {}", msg[0]) } else { msg[0].clone() },
        msg,
        vec![],
        helps,
        &stacktrace,
        &ecx.machine,
    );

    // Include a note like `std` does when we omit frames from a backtrace
    if was_pruned {
        ecx.tcx.sess.dcx().note(
            "some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace",
        );
    }

    eprint!("{extra}"); // newlines are already in the string

    // Debug-dump all locals.
    for (i, frame) in ecx.active_thread_stack().iter().enumerate() {
        trace!("-------------------");
        trace!("Frame {}", i);
        trace!("    return: {:?}", frame.return_place);
        for (i, local) in frame.locals.iter().enumerate() {
            trace!("    local {}: {:?}", i, local);
        }
    }

    None
}

pub fn report_leaks<'mir, 'tcx>(
    ecx: &InterpCx<'mir, 'tcx, MiriMachine<'mir, 'tcx>>,
    leaks: Vec<(AllocId, MemoryKind<MiriMemoryKind>, Allocation<Provenance, AllocExtra<'tcx>>)>,
) {
    let mut any_pruned = false;
    for (id, kind, mut alloc) in leaks {
        let Some(backtrace) = alloc.extra.backtrace.take() else {
            continue;
        };
        let (backtrace, pruned) = prune_stacktrace(backtrace, &ecx.machine);
        any_pruned |= pruned;
        report_msg(
            DiagLevel::Error,
            format!(
                "memory leaked: {id:?} ({}, size: {:?}, align: {:?}), allocated here:",
                kind,
                alloc.size().bytes(),
                alloc.align.bytes()
            ),
            vec![],
            vec![],
            vec![],
            &backtrace,
            &ecx.machine,
        );
    }
    if any_pruned {
        ecx.tcx.sess.dcx().note(
            "some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace",
        );
    }
}

/// Report an error or note (depending on the `error` argument) with the given stacktrace.
/// Also emits a full stacktrace of the interpreter stack.
/// We want to present a multi-line span message for some errors. Diagnostics do not support this
/// directly, so we pass the lines as a `Vec<String>` and display each line after the first with an
/// additional `span_label` or `note` call.
pub fn report_msg<'tcx>(
    diag_level: DiagLevel,
    title: String,
    span_msg: Vec<String>,
    notes: Vec<(Option<SpanData>, String)>,
    helps: Vec<(Option<SpanData>, String)>,
    stacktrace: &[FrameInfo<'tcx>],
    machine: &MiriMachine<'_, 'tcx>,
) {
    let span = stacktrace.first().map_or(DUMMY_SP, |fi| fi.span);
    let sess = machine.tcx.sess;
    let mut err = match diag_level {
        DiagLevel::Error => sess.struct_span_err(span, title).forget_guarantee(),
        DiagLevel::Warning => sess.struct_span_warn(span, title),
        DiagLevel::Note => sess.dcx().struct_span_note(span, title),
    };

    // Show main message.
    if span != DUMMY_SP {
        for line in span_msg {
            err.span_label(span, line);
        }
    } else {
        // Make sure we show the message even when it is a dummy span.
        for line in span_msg {
            err.note(line);
        }
        err.note("(no span available)");
    }

    // Show note and help messages.
    let mut extra_span = false;
    let notes_len = notes.len();
    for (span_data, note) in notes {
        if let Some(span_data) = span_data {
            err.span_note(span_data.span(), note);
            extra_span = true;
        } else {
            err.note(note);
        }
    }
    let helps_len = helps.len();
    for (span_data, help) in helps {
        if let Some(span_data) = span_data {
            err.span_help(span_data.span(), help);
            extra_span = true;
        } else {
            err.help(help);
        }
    }
    if notes_len + helps_len > 0 {
        // Add visual separator before backtrace.
        err.note(if extra_span { "BACKTRACE (of the first span):" } else { "BACKTRACE:" });
    }

    let (mut err, handler) = err.into_diagnostic().unwrap();

    // Add backtrace
    for (idx, frame_info) in stacktrace.iter().enumerate() {
        let is_local = machine.is_local(frame_info);
        // No span for non-local frames and the first frame (which is the error site).
        if is_local && idx > 0 {
            err.eager_subdiagnostic(handler, frame_info.as_note(machine.tcx));
        } else {
            let sm = sess.source_map();
            let span = sm.span_to_embeddable_string(frame_info.span);
            err.note(format!("{frame_info} at {span}"));
        }
    }

    handler.emit_diagnostic(err);
}

impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
    pub fn emit_diagnostic(&self, e: NonHaltingDiagnostic) {
        use NonHaltingDiagnostic::*;

        let stacktrace =
            MiriInterpCx::generate_stacktrace_from_stack(self.threads.active_thread_stack());
        let (stacktrace, _was_pruned) = prune_stacktrace(stacktrace, self);

        let (title, diag_level) = match &e {
            RejectedIsolatedOp(_) =>
                ("operation rejected by isolation".to_string(), DiagLevel::Warning),
            Int2Ptr { .. } => ("integer-to-pointer cast".to_string(), DiagLevel::Warning),
            CreatedPointerTag(..)
            | PoppedPointerTag(..)
            | CreatedCallId(..)
            | CreatedAlloc(..)
            | FreedAlloc(..)
            | ProgressReport { .. }
            | WeakMemoryOutdatedLoad => ("tracking was triggered".to_string(), DiagLevel::Note),
        };

        let msg = match &e {
            CreatedPointerTag(tag, None, _) => format!("created base tag {tag:?}"),
            CreatedPointerTag(tag, Some(perm), None) =>
                format!("created {tag:?} with {perm} derived from unknown tag"),
            CreatedPointerTag(tag, Some(perm), Some((alloc_id, range, orig_tag))) =>
                format!(
                    "created tag {tag:?} with {perm} at {alloc_id:?}{range:?} derived from {orig_tag:?}"
                ),
            PoppedPointerTag(item, cause) => format!("popped tracked tag for item {item:?}{cause}"),
            CreatedCallId(id) => format!("function call with id {id}"),
            CreatedAlloc(AllocId(id), size, align, kind) =>
                format!(
                    "created {kind} allocation of {size} bytes (alignment {align} bytes) with id {id}",
                    size = size.bytes(),
                    align = align.bytes(),
                ),
            FreedAlloc(AllocId(id)) => format!("freed allocation with id {id}"),
            RejectedIsolatedOp(ref op) =>
                format!("{op} was made to return an error due to isolation"),
            ProgressReport { .. } =>
                format!("progress report: current operation being executed is here"),
            Int2Ptr { .. } => format!("integer-to-pointer cast"),
            WeakMemoryOutdatedLoad =>
                format!("weak memory emulation: outdated value returned from load"),
        };

        let notes = match &e {
            ProgressReport { block_count } => {
                // It is important that each progress report is slightly different, since
                // identical diagnostics are being deduplicated.
                vec![(None, format!("so far, {block_count} basic blocks have been executed"))]
            }
            _ => vec![],
        };

        let helps = match &e {
            Int2Ptr { details: true } =>
                vec![
                    (
                        None,
                        format!(
                            "This program is using integer-to-pointer casts or (equivalently) `ptr::from_exposed_addr`,"
                        ),
                    ),
                    (
                        None,
                        format!("which means that Miri might miss pointer bugs in this program."),
                    ),
                    (
                        None,
                        format!(
                            "See https://doc.rust-lang.org/nightly/std/ptr/fn.from_exposed_addr.html for more details on that operation."
                        ),
                    ),
                    (
                        None,
                        format!(
                            "To ensure that Miri does not miss bugs in your program, use Strict Provenance APIs (https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance, https://crates.io/crates/sptr) instead."
                        ),
                    ),
                    (
                        None,
                        format!(
                            "You can then pass the `-Zmiri-strict-provenance` flag to Miri, to ensure you are not relying on `from_exposed_addr` semantics."
                        ),
                    ),
                    (
                        None,
                        format!(
                            "Alternatively, the `-Zmiri-permissive-provenance` flag disables this warning."
                        ),
                    ),
                ],
            _ => vec![],
        };

        report_msg(diag_level, title, vec![msg], notes, helps, &stacktrace, self);
    }
}

impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {}
pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
    fn emit_diagnostic(&self, e: NonHaltingDiagnostic) {
        let this = self.eval_context_ref();
        this.machine.emit_diagnostic(e);
    }

    /// We had a panic in Miri itself, try to print something useful.
    fn handle_ice(&self) {
        eprintln!();
        eprintln!(
            "Miri caused an ICE during evaluation. Here's the interpreter backtrace at the time of the panic:"
        );
        let this = self.eval_context_ref();
        let stacktrace = this.generate_stacktrace();
        report_msg(
            DiagLevel::Note,
            "the place in the program where the ICE was triggered".to_string(),
            vec![],
            vec![],
            vec![],
            &stacktrace,
            &this.machine,
        );
    }
}