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use std::fmt;
use std::ops::Range;
use rustc_data_structures::fx::FxHashMap;
use rustc_span::{Span, SpanData};
use crate::borrow_tracker::tree_borrows::{
perms::{PermTransition, Permission},
tree::LocationState,
unimap::UniIndex,
};
use crate::borrow_tracker::ProtectorKind;
use crate::*;
/// Cause of an access: either a real access or one
/// inserted by Tree Borrows due to a reborrow or a deallocation.
#[derive(Clone, Copy, Debug)]
pub enum AccessCause {
Explicit(AccessKind),
Reborrow,
Dealloc,
FnExit(AccessKind),
}
impl fmt::Display for AccessCause {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::Explicit(kind) => write!(f, "{kind}"),
Self::Reborrow => write!(f, "reborrow"),
Self::Dealloc => write!(f, "deallocation"),
// This is dead code, since the protector release access itself can never
// cause UB (while the protector is active, if some other access invalidates
// further use of the protected tag, that is immediate UB).
// Describing the cause of UB is the only time this function is called.
Self::FnExit(_) => unreachable!("protector accesses can never be the source of UB"),
}
}
}
impl AccessCause {
fn print_as_access(self, is_foreign: bool) -> String {
let rel = if is_foreign { "foreign" } else { "child" };
match self {
Self::Explicit(kind) => format!("{rel} {kind}"),
Self::Reborrow => format!("reborrow (acting as a {rel} read access)"),
Self::Dealloc => format!("deallocation (acting as a {rel} write access)"),
Self::FnExit(kind) => format!("protector release (acting as a {rel} {kind})"),
}
}
}
/// Complete data for an event:
#[derive(Clone, Debug)]
pub struct Event {
/// Transformation of permissions that occurred because of this event.
pub transition: PermTransition,
/// Kind of the access that triggered this event.
pub access_cause: AccessCause,
/// Relative position of the tag to the one used for the access.
pub is_foreign: bool,
/// User-visible range of the access.
/// `None` means that this is an implicit access to the entire allocation
/// (used for the implicit read on protector release).
pub access_range: Option<AllocRange>,
/// The transition recorded by this event only occurred on a subrange of
/// `access_range`: a single access on `access_range` triggers several events,
/// each with their own mutually disjoint `transition_range`. No-op transitions
/// should not be recorded as events, so the union of all `transition_range` is not
/// necessarily the entire `access_range`.
///
/// No data from any `transition_range` should ever be user-visible, because
/// both the start and end of `transition_range` are entirely dependent on the
/// internal representation of `RangeMap` which is supposed to be opaque.
/// What will be shown in the error message is the first byte `error_offset` of
/// the `TbError`, which should satisfy
/// `event.transition_range.contains(error.error_offset)`.
pub transition_range: Range<u64>,
/// Line of code that triggered this event.
pub span: Span,
}
/// List of all events that affected a tag.
/// NOTE: not all of these events are relevant for a particular location,
/// the events should be filtered before the generation of diagnostics.
/// Available filtering methods include `History::forget` and `History::extract_relevant`.
#[derive(Clone, Debug)]
pub struct History {
tag: BorTag,
created: (Span, Permission),
events: Vec<Event>,
}
/// History formatted for use by `src/diagnostics.rs`.
///
/// NOTE: needs to be `Send` because of a bound on `MachineStopType`, hence
/// the use of `SpanData` rather than `Span`.
#[derive(Debug, Clone, Default)]
pub struct HistoryData {
pub events: Vec<(Option<SpanData>, String)>, // includes creation
}
impl History {
/// Record an additional event to the history.
pub fn push(&mut self, event: Event) {
self.events.push(event);
}
}
impl HistoryData {
// Format events from `new_history` into those recorded by `self`.
//
// NOTE: also converts `Span` to `SpanData`.
fn extend(&mut self, new_history: History, tag_name: &'static str, show_initial_state: bool) {
let History { tag, created, events } = new_history;
let this = format!("the {tag_name} tag {tag:?}");
let msg_initial_state = format!(", in the initial state {}", created.1);
let msg_creation = format!(
"{this} was created here{maybe_msg_initial_state}",
maybe_msg_initial_state = if show_initial_state { &msg_initial_state } else { "" },
);
self.events.push((Some(created.0.data()), msg_creation));
for &Event {
transition,
is_foreign,
access_cause,
access_range,
span,
transition_range: _,
} in &events
{
// NOTE: `transition_range` is explicitly absent from the error message, it has no significance
// to the user. The meaningful one is `access_range`.
let access = access_cause.print_as_access(is_foreign);
let access_range_text = match access_range {
Some(r) => format!("at offsets {r:?}"),
None => format!("on every location previously accessed by this tag"),
};
self.events.push((
Some(span.data()),
format!(
"{this} later transitioned to {endpoint} due to a {access} {access_range_text}",
endpoint = transition.endpoint()
),
));
self.events
.push((None, format!("this transition corresponds to {}", transition.summary())));
}
}
}
/// Some information that is irrelevant for the algorithm but very
/// convenient to know about a tag for debugging and testing.
#[derive(Clone, Debug)]
pub struct NodeDebugInfo {
/// The tag in question.
pub tag: BorTag,
/// Name(s) that were associated with this tag (comma-separated).
/// Typically the name of the variable holding the corresponding
/// pointer in the source code.
/// Helps match tag numbers to human-readable names.
pub name: Option<String>,
/// Notable events in the history of this tag, used for
/// diagnostics.
///
/// NOTE: by virtue of being part of `NodeDebugInfo`,
/// the history is automatically cleaned up by the GC.
/// NOTE: this is `!Send`, it needs to be converted before displaying
/// the actual diagnostics because `src/diagnostics.rs` requires `Send`.
pub history: History,
}
impl NodeDebugInfo {
/// Information for a new node. By default it has no
/// name and an empty history.
pub fn new(tag: BorTag, initial: Permission, span: Span) -> Self {
let history = History { tag, created: (span, initial), events: Vec::new() };
Self { tag, name: None, history }
}
/// Add a name to the tag. If a same tag is associated to several pointers,
/// it can have several names which will be separated by commas.
pub fn add_name(&mut self, name: &str) {
if let Some(ref mut prev_name) = &mut self.name {
prev_name.push_str(", ");
prev_name.push_str(name);
} else {
self.name = Some(String::from(name));
}
}
}
impl fmt::Display for NodeDebugInfo {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if let Some(ref name) = self.name {
write!(f, "{tag:?} ({name})", tag = self.tag)
} else {
write!(f, "{tag:?}", tag = self.tag)
}
}
}
impl<'tcx> Tree {
/// Climb the tree to get the tag of a distant ancestor.
/// Allows operations on tags that are unreachable by the program
/// but still exist in the tree. Not guaranteed to perform consistently
/// if `provenance-gc=1`.
fn nth_parent(&self, tag: BorTag, nth_parent: u8) -> Option<BorTag> {
let mut idx = self.tag_mapping.get(&tag).unwrap();
for _ in 0..nth_parent {
let node = self.nodes.get(idx).unwrap();
idx = node.parent?;
}
Some(self.nodes.get(idx).unwrap().tag)
}
/// Debug helper: assign name to tag.
pub fn give_pointer_debug_name(
&mut self,
tag: BorTag,
nth_parent: u8,
name: &str,
) -> InterpResult<'tcx> {
let tag = self.nth_parent(tag, nth_parent).unwrap();
let idx = self.tag_mapping.get(&tag).unwrap();
if let Some(node) = self.nodes.get_mut(idx) {
node.debug_info.add_name(name);
} else {
eprintln!("Tag {tag:?} (to be named '{name}') not found!");
}
Ok(())
}
/// Debug helper: determines if the tree contains a tag.
pub fn is_allocation_of(&self, tag: BorTag) -> bool {
self.tag_mapping.contains_key(&tag)
}
}
#[derive(Debug, Clone, Copy)]
pub(super) enum TransitionError {
/// This access is not allowed because some parent tag has insufficient permissions.
/// For example, if a tag is `Frozen` and encounters a child write this will
/// produce a `ChildAccessForbidden(Frozen)`.
/// This kind of error can only occur on child accesses.
ChildAccessForbidden(Permission),
/// A protector was triggered due to an invalid transition that loses
/// too much permissions.
/// For example, if a protected tag goes from `Active` to `Disabled` due
/// to a foreign write this will produce a `ProtectedDisabled(Active)`.
/// This kind of error can only occur on foreign accesses.
ProtectedDisabled(Permission),
/// Cannot deallocate because some tag in the allocation is strongly protected.
/// This kind of error can only occur on deallocations.
ProtectedDealloc,
}
impl History {
/// Keep only the tag and creation
fn forget(&self) -> Self {
History { events: Vec::new(), created: self.created, tag: self.tag }
}
/// Reconstruct the history relevant to `error_offset` by filtering
/// only events whose range contains the offset we are interested in.
fn extract_relevant(&self, error_offset: u64, error_kind: TransitionError) -> Self {
History {
events: self
.events
.iter()
.filter(|e| e.transition_range.contains(&error_offset))
.filter(|e| e.transition.is_relevant(error_kind))
.cloned()
.collect::<Vec<_>>(),
created: self.created,
tag: self.tag,
}
}
}
/// Failures that can occur during the execution of Tree Borrows procedures.
pub(super) struct TbError<'node> {
/// What failure occurred.
pub error_kind: TransitionError,
/// The allocation in which the error is happening.
pub alloc_id: AllocId,
/// The offset (into the allocation) at which the conflict occurred.
pub error_offset: u64,
/// The tag on which the error was triggered.
/// On protector violations, this is the tag that was protected.
/// On accesses rejected due to insufficient permissions, this is the
/// tag that lacked those permissions.
pub conflicting_info: &'node NodeDebugInfo,
// What kind of access caused this error (read, write, reborrow, deallocation)
pub access_cause: AccessCause,
/// Which tag the access that caused this error was made through, i.e.
/// which tag was used to read/write/deallocate.
pub accessed_info: &'node NodeDebugInfo,
}
impl TbError<'_> {
/// Produce a UB error.
pub fn build<'tcx>(self) -> InterpError<'tcx> {
use TransitionError::*;
let cause = self.access_cause;
let accessed = self.accessed_info;
let conflicting = self.conflicting_info;
let accessed_is_conflicting = accessed.tag == conflicting.tag;
let title = format!(
"{cause} through {accessed} at {alloc_id:?}[{offset:#x}] is forbidden",
alloc_id = self.alloc_id,
offset = self.error_offset
);
let (title, details, conflicting_tag_name) = match self.error_kind {
ChildAccessForbidden(perm) => {
let conflicting_tag_name =
if accessed_is_conflicting { "accessed" } else { "conflicting" };
let mut details = Vec::new();
if !accessed_is_conflicting {
details.push(format!(
"the accessed tag {accessed} is a child of the conflicting tag {conflicting}"
));
}
let access = cause.print_as_access(/* is_foreign */ false);
details.push(format!(
"the {conflicting_tag_name} tag {conflicting} has state {perm} which forbids this {access}"
));
(title, details, conflicting_tag_name)
}
ProtectedDisabled(before_disabled) => {
let conflicting_tag_name = "protected";
let access = cause.print_as_access(/* is_foreign */ true);
let details = vec![
format!(
"the accessed tag {accessed} is foreign to the {conflicting_tag_name} tag {conflicting} (i.e., it is not a child)"
),
format!(
"this {access} would cause the {conflicting_tag_name} tag {conflicting} (currently {before_disabled}) to become Disabled"
),
format!("protected tags must never be Disabled"),
];
(title, details, conflicting_tag_name)
}
ProtectedDealloc => {
let conflicting_tag_name = "strongly protected";
let details = vec![
format!(
"the allocation of the accessed tag {accessed} also contains the {conflicting_tag_name} tag {conflicting}"
),
format!("the {conflicting_tag_name} tag {conflicting} disallows deallocations"),
];
(title, details, conflicting_tag_name)
}
};
let mut history = HistoryData::default();
if !accessed_is_conflicting {
history.extend(self.accessed_info.history.forget(), "accessed", false);
}
history.extend(
self.conflicting_info.history.extract_relevant(self.error_offset, self.error_kind),
conflicting_tag_name,
true,
);
err_machine_stop!(TerminationInfo::TreeBorrowsUb { title, details, history })
}
}
type S = &'static str;
/// Pretty-printing details
///
/// Example:
/// ```rust,ignore (private type)
/// DisplayFmtWrapper {
/// top: '>',
/// bot: '<',
/// warning_text: "Some tags have been hidden",
/// }
/// ```
/// will wrap the entire text with
/// ```text
/// >>>>>>>>>>>>>>>>>>>>>>>>>>
/// Some tags have been hidden
///
/// [ main display here ]
///
/// <<<<<<<<<<<<<<<<<<<<<<<<<<
/// ```
struct DisplayFmtWrapper {
/// Character repeated to make the upper border.
top: char,
/// Character repeated to make the lower border.
bot: char,
/// Warning about some tags (unnamed) being hidden.
warning_text: S,
}
/// Formatting of the permissions on each range.
///
/// Example:
/// ```rust,ignore (private type)
/// DisplayFmtPermission {
/// open: "[",
/// sep: "|",
/// close: "]",
/// uninit: "___",
/// range_sep: "..",
/// }
/// ```
/// will show each permission line as
/// ```text
/// 0.. 1.. 2.. 3.. 4.. 5
/// [Act|Res|Frz|Dis|___]
/// ```
struct DisplayFmtPermission {
/// Text that starts the permission block.
open: S,
/// Text that separates permissions on different ranges.
sep: S,
/// Text that ends the permission block.
close: S,
/// Text to show when a permission is not initialized.
/// Should have the same width as a `Permission`'s `.short_name()`, i.e.
/// 3 if using the `Res/Act/Frz/Dis` notation.
uninit: S,
/// Text to separate the `start` and `end` values of a range.
range_sep: S,
}
/// Formatting of the tree structure.
///
/// Example:
/// ```rust,ignore (private type)
/// DisplayFmtPadding {
/// join_middle: "|-",
/// join_last: "'-",
/// join_haschild: "-+-",
/// join_default: "---",
/// indent_middle: "| ",
/// indent_last: " ",
/// }
/// ```
/// will show the tree as
/// ```text
/// -+- root
/// |--+- a
/// | '--+- b
/// | '---- c
/// |--+- d
/// | '---- e
/// '---- f
/// ```
struct DisplayFmtPadding {
/// Connector for a child other than the last.
join_middle: S,
/// Connector for the last child. Should have the same width as `join_middle`.
join_last: S,
/// Connector for a node that itself has a child.
join_haschild: S,
/// Connector for a node that does not have a child. Should have the same width
/// as `join_haschild`.
join_default: S,
/// Indentation when there is a next child.
indent_middle: S,
/// Indentation for the last child.
indent_last: S,
}
/// How to show whether a location has been accessed
///
/// Example:
/// ```rust,ignore (private type)
/// DisplayFmtAccess {
/// yes: " ",
/// no: "?",
/// meh: "_",
/// }
/// ```
/// will show states as
/// ```text
/// Act
/// ?Res
/// ____
/// ```
struct DisplayFmtAccess {
/// Used when `State.initialized = true`.
yes: S,
/// Used when `State.initialized = false`.
/// Should have the same width as `yes`.
no: S,
/// Used when there is no `State`.
/// Should have the same width as `yes`.
meh: S,
}
/// All parameters to determine how the tree is formatted.
struct DisplayFmt {
wrapper: DisplayFmtWrapper,
perm: DisplayFmtPermission,
padding: DisplayFmtPadding,
accessed: DisplayFmtAccess,
}
impl DisplayFmt {
/// Print the permission with the format
/// ` Res`/` Re*`/` Act`/` Frz`/` Dis` for accessed locations
/// and `?Res`/`?Re*`/`?Act`/`?Frz`/`?Dis` for unaccessed locations.
fn print_perm(&self, perm: Option<LocationState>) -> String {
if let Some(perm) = perm {
format!(
"{ac}{st}",
ac = if perm.is_initialized() { self.accessed.yes } else { self.accessed.no },
st = perm.permission().short_name(),
)
} else {
format!("{}{}", self.accessed.meh, self.perm.uninit)
}
}
/// Print the tag with the format `<XYZ>` if the tag is unnamed,
/// and `<XYZ=name>` if the tag is named.
fn print_tag(&self, tag: BorTag, name: &Option<String>) -> String {
let printable_tag = tag.get();
if let Some(name) = name {
format!("<{printable_tag}={name}>")
} else {
format!("<{printable_tag}>")
}
}
/// Print extra text if the tag has a protector.
fn print_protector(&self, protector: Option<&ProtectorKind>) -> &'static str {
protector
.map(|p| {
match *p {
ProtectorKind::WeakProtector => " Weakly protected",
ProtectorKind::StrongProtector => " Strongly protected",
}
})
.unwrap_or("")
}
}
/// Track the indentation of the tree.
struct DisplayIndent {
curr: String,
}
impl DisplayIndent {
fn new() -> Self {
Self { curr: " ".to_string() }
}
/// Increment the indentation by one. Note: need to know if this
/// is the last child or not because the presence of other children
/// changes the way the indentation is shown.
fn increment(&mut self, formatter: &DisplayFmt, is_last: bool) {
self.curr.push_str(if is_last {
formatter.padding.indent_last
} else {
formatter.padding.indent_middle
});
}
/// Pop the last level of indentation.
fn decrement(&mut self, formatter: &DisplayFmt) {
for _ in 0..formatter.padding.indent_last.len() {
let _ = self.curr.pop();
}
}
/// Print the current indentation.
fn write(&self, s: &mut String) {
s.push_str(&self.curr);
}
}
/// Repeat a character a number of times.
fn char_repeat(c: char, n: usize) -> String {
std::iter::once(c).cycle().take(n).collect::<String>()
}
/// Extracted information from the tree, in a form that is readily accessible
/// for printing. I.e. resolve parent-child pointers into an actual tree,
/// zip permissions with their tag, remove wrappers, stringify data.
struct DisplayRepr {
tag: BorTag,
name: Option<String>,
rperm: Vec<Option<LocationState>>,
children: Vec<DisplayRepr>,
}
impl DisplayRepr {
fn from(tree: &Tree, show_unnamed: bool) -> Option<Self> {
let mut v = Vec::new();
extraction_aux(tree, tree.root, show_unnamed, &mut v);
let Some(root) = v.pop() else {
if show_unnamed {
unreachable!(
"This allocation contains no tags, not even a root. This should not happen."
);
}
eprintln!(
"This allocation does not contain named tags. Use `miri_print_borrow_state(_, true)` to also print unnamed tags."
);
return None;
};
assert!(v.is_empty());
return Some(root);
fn extraction_aux(
tree: &Tree,
idx: UniIndex,
show_unnamed: bool,
acc: &mut Vec<DisplayRepr>,
) {
let node = tree.nodes.get(idx).unwrap();
let name = node.debug_info.name.clone();
let children_sorted = {
let mut children = node.children.iter().cloned().collect::<Vec<_>>();
children.sort_by_key(|idx| tree.nodes.get(*idx).unwrap().tag);
children
};
if !show_unnamed && name.is_none() {
// We skip this node
for child_idx in children_sorted {
extraction_aux(tree, child_idx, show_unnamed, acc);
}
} else {
// We take this node
let rperm = tree
.rperms
.iter_all()
.map(move |(_offset, perms)| {
let perm = perms.get(idx);
perm.cloned()
})
.collect::<Vec<_>>();
let mut children = Vec::new();
for child_idx in children_sorted {
extraction_aux(tree, child_idx, show_unnamed, &mut children);
}
acc.push(DisplayRepr { tag: node.tag, name, rperm, children });
}
}
}
fn print(
&self,
fmt: &DisplayFmt,
indenter: &mut DisplayIndent,
protected_tags: &FxHashMap<BorTag, ProtectorKind>,
ranges: Vec<Range<u64>>,
print_warning: bool,
) {
let mut block = Vec::new();
// Push the header and compute the required paddings for the body.
// Header looks like this: `0.. 1.. 2.. 3.. 4.. 5.. 6.. 7.. 8`,
// and is properly aligned with the `|` of the body.
let (range_header, range_padding) = {
let mut header_top = String::new();
header_top.push_str("0..");
let mut padding = Vec::new();
for (i, range) in ranges.iter().enumerate() {
if i > 0 {
header_top.push_str(fmt.perm.range_sep);
}
let s = range.end.to_string();
let l = s.chars().count() + fmt.perm.range_sep.chars().count();
{
let target_len =
fmt.perm.uninit.chars().count() + fmt.accessed.yes.chars().count() + 1;
let tot_len = target_len.max(l);
let header_top_pad_len = target_len.saturating_sub(l);
let body_pad_len = tot_len.saturating_sub(target_len);
header_top.push_str(&format!("{}{}", char_repeat(' ', header_top_pad_len), s));
padding.push(body_pad_len);
}
}
([header_top], padding)
};
for s in range_header {
block.push(s);
}
// This is the actual work
print_aux(
self,
&range_padding,
fmt,
indenter,
protected_tags,
true, /* root _is_ the last child */
&mut block,
);
// Then it's just prettifying it with a border of dashes.
{
let wr = &fmt.wrapper;
let max_width = {
let block_width = block.iter().map(|s| s.chars().count()).max().unwrap();
if print_warning {
block_width.max(wr.warning_text.chars().count())
} else {
block_width
}
};
eprintln!("{}", char_repeat(wr.top, max_width));
if print_warning {
eprintln!("{}", wr.warning_text,);
}
for line in block {
eprintln!("{line}");
}
eprintln!("{}", char_repeat(wr.bot, max_width));
}
// Here is the function that does the heavy lifting
fn print_aux(
tree: &DisplayRepr,
padding: &[usize],
fmt: &DisplayFmt,
indent: &mut DisplayIndent,
protected_tags: &FxHashMap<BorTag, ProtectorKind>,
is_last_child: bool,
acc: &mut Vec<String>,
) {
let mut line = String::new();
// Format the permissions on each range.
// Looks like `| Act| Res| Res| Act|`.
line.push_str(fmt.perm.open);
for (i, (perm, &pad)) in tree.rperm.iter().zip(padding.iter()).enumerate() {
if i > 0 {
line.push_str(fmt.perm.sep);
}
let show_perm = fmt.print_perm(*perm);
line.push_str(&format!("{}{}", char_repeat(' ', pad), show_perm));
}
line.push_str(fmt.perm.close);
// Format the tree structure.
// Main difficulty is handling the indentation properly.
indent.write(&mut line);
{
// padding
line.push_str(if is_last_child {
fmt.padding.join_last
} else {
fmt.padding.join_middle
});
line.push_str(fmt.padding.join_default);
line.push_str(if tree.children.is_empty() {
fmt.padding.join_default
} else {
fmt.padding.join_haschild
});
line.push_str(fmt.padding.join_default);
line.push_str(fmt.padding.join_default);
}
line.push_str(&fmt.print_tag(tree.tag, &tree.name));
let protector = protected_tags.get(&tree.tag);
line.push_str(fmt.print_protector(protector));
// Push the line to the accumulator then recurse.
acc.push(line);
let nb_children = tree.children.len();
for (i, child) in tree.children.iter().enumerate() {
indent.increment(fmt, is_last_child);
print_aux(child, padding, fmt, indent, protected_tags, i + 1 == nb_children, acc);
indent.decrement(fmt);
}
}
}
}
const DEFAULT_FORMATTER: DisplayFmt = DisplayFmt {
wrapper: DisplayFmtWrapper {
top: '─',
bot: '─',
warning_text: "Warning: this tree is indicative only. Some tags may have been hidden.",
},
perm: DisplayFmtPermission { open: "|", sep: "|", close: "|", uninit: "----", range_sep: ".." },
padding: DisplayFmtPadding {
join_middle: "├",
join_last: "└",
indent_middle: "│ ",
indent_last: " ",
join_haschild: "┬",
join_default: "─",
},
accessed: DisplayFmtAccess { yes: " ", no: "?", meh: "-" },
};
impl<'tcx> Tree {
/// Display the contents of the tree.
pub fn print_tree(
&self,
protected_tags: &FxHashMap<BorTag, ProtectorKind>,
show_unnamed: bool,
) -> InterpResult<'tcx> {
let mut indenter = DisplayIndent::new();
let ranges = self.rperms.iter_all().map(|(range, _perms)| range).collect::<Vec<_>>();
if let Some(repr) = DisplayRepr::from(self, show_unnamed) {
repr.print(
&DEFAULT_FORMATTER,
&mut indenter,
protected_tags,
ranges,
/* print warning message about tags not shown */ !show_unnamed,
);
}
Ok(())
}
}