1 files changed, 231 insertions, 0 deletions
diff --git a/components/script_plugins/unrooted_must_root.rs b/components/script_plugins/unrooted_must_root.rs
new file mode 100644
index 00000000000..660a0c58781
--- /dev/null
+++ b/components/script_plugins/unrooted_must_root.rs
@@ -0,0 +1,231 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use rustc::hir;
+use rustc::hir::intravisit as visit;
+use rustc::hir::map as ast_map;
+use rustc::lint::{LateContext, LintPass, LintArray, LateLintPass, LintContext};
+use rustc::ty;
+use syntax::{ast, codemap};
+use utils::{match_def_path, in_derive_expn};
+
+declare_lint!(UNROOTED_MUST_ROOT, Deny,
+              "Warn and report usage of unrooted jsmanaged objects");
+
+/// Lint for ensuring safe usage of unrooted pointers
+///
+/// This lint (disable with `-A unrooted-must-root`/`#[allow(unrooted_must_root)]`) ensures that `#[must_root]`
+/// values are used correctly.
+///
+/// "Incorrect" usage includes:
+///
+///  - Not being used in a struct/enum field which is not `#[must_root]` itself
+///  - Not being used as an argument to a function (Except onces named `new` and `new_inherited`)
+///  - Not being bound locally in a `let` statement, assignment, `for` loop, or `match` statement.
+///
+/// This helps catch most situations where pointers like `JS<T>` are used in a way that they can be invalidated by a
+/// GC pass.
+///
+/// Structs which have their own mechanism of rooting their unrooted contents (e.g. `ScriptThread`)
+/// can be marked as `#[allow(unrooted_must_root)]`. Smart pointers which root their interior type
+/// can be marked as `#[allow_unrooted_interior]`
+pub struct UnrootedPass;
+
+impl UnrootedPass {
+    pub fn new() -> UnrootedPass {
+        UnrootedPass
+    }
+}
+
+/// Checks if a type is unrooted or contains any owned unrooted types
+fn is_unrooted_ty(cx: &LateContext, ty: &ty::TyS, in_new_function: bool) -> bool {
+    let mut ret = false;
+    ty.maybe_walk(|t| {
+        match t.sty {
+            ty::TyAdt(did, _) => {
+                if cx.tcx.has_attr(did.did, "must_root") {
+                    ret = true;
+                    false
+                } else if cx.tcx.has_attr(did.did, "allow_unrooted_interior") {
+                    false
+                } else if match_def_path(cx, did.did, &["core", "cell", "Ref"])
+                        || match_def_path(cx, did.did, &["core", "cell", "RefMut"])
+                        || match_def_path(cx, did.did, &["core", "slice", "Iter"])
+                        || match_def_path(cx, did.did, &["std", "collections", "hash", "map", "OccupiedEntry"])
+                        || match_def_path(cx, did.did, &["std", "collections", "hash", "map", "VacantEntry"]) {
+                    // Structures which are semantically similar to an &ptr.
+                    false
+                } else if did.is_box() && in_new_function {
+                    // box in new() is okay
+                    false
+                } else {
+                    true
+                }
+            },
+            ty::TyRef(..) => false, // don't recurse down &ptrs
+            ty::TyRawPtr(..) => false, // don't recurse down *ptrs
+            ty::TyFnDef(..) | ty::TyFnPtr(_) => false,
+            _ => true
+        }
+    });
+    ret
+}
+
+impl LintPass for UnrootedPass {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(UNROOTED_MUST_ROOT)
+    }
+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnrootedPass {
+    /// All structs containing #[must_root] types must be #[must_root] themselves
+    fn check_struct_def(&mut self,
+                        cx: &LateContext,
+                        def: &hir::VariantData,
+                        _n: ast::Name,
+                        _gen: &hir::Generics,
+                        id: ast::NodeId) {
+        let item = match cx.tcx.hir.get(id) {
+            ast_map::Node::NodeItem(item) => item,
+            _ => cx.tcx.hir.expect_item(cx.tcx.hir.get_parent(id)),
+        };
+        if item.attrs.iter().all(|a| !a.check_name("must_root")) {
+            for ref field in def.fields() {
+                let def_id = cx.tcx.hir.local_def_id(field.id);
+                if is_unrooted_ty(cx, cx.tcx.item_type(def_id), false) {
+                    cx.span_lint(UNROOTED_MUST_ROOT, field.span,
+                                 "Type must be rooted, use #[must_root] on the struct definition to propagate")
+                }
+            }
+        }
+    }
+
+    /// All enums containing #[must_root] types must be #[must_root] themselves
+    fn check_variant(&mut self, cx: &LateContext, var: &hir::Variant, _gen: &hir::Generics) {
+        let ref map = cx.tcx.hir;
+        if map.expect_item(map.get_parent(var.node.data.id())).attrs.iter().all(|a| !a.check_name("must_root")) {
+            match var.node.data {
+                hir::VariantData::Tuple(ref fields, _) => {
+                    for ref field in fields {
+                        let def_id = cx.tcx.hir.local_def_id(field.id);
+                        if is_unrooted_ty(cx, cx.tcx.item_type(def_id), false) {
+                            cx.span_lint(UNROOTED_MUST_ROOT, field.ty.span,
+                                         "Type must be rooted, use #[must_root] on \
+                                          the enum definition to propagate")
+                        }
+                    }
+                }
+                _ => () // Struct variants already caught by check_struct_def
+            }
+        }
+    }
+    /// Function arguments that are #[must_root] types are not allowed
+    fn check_fn(&mut self,
+                cx: &LateContext<'a, 'tcx>,
+                kind: visit::FnKind,
+                decl: &'tcx hir::FnDecl,
+                body: &'tcx hir::Body,
+                span: codemap::Span,
+                id: ast::NodeId) {
+        let in_new_function = match kind {
+            visit::FnKind::ItemFn(n, _, _, _, _, _, _) |
+            visit::FnKind::Method(n, _, _, _) => {
+                &*n.as_str() == "new" || n.as_str().starts_with("new_")
+            }
+            visit::FnKind::Closure(_) => return,
+        };
+
+        if !in_derive_expn(cx, span) {
+            let def_id = cx.tcx.hir.local_def_id(id);
+            let ty = cx.tcx.item_type(def_id);
+
+            for (arg, ty) in decl.inputs.iter().zip(ty.fn_args().0.iter()) {
+                if is_unrooted_ty(cx, ty, false) {
+                    cx.span_lint(UNROOTED_MUST_ROOT, arg.span, "Type must be rooted")
+                }
+            }
+
+            if !in_new_function {
+                if is_unrooted_ty(cx, ty.fn_ret().0, false) {
+                    cx.span_lint(UNROOTED_MUST_ROOT, decl.output.span(), "Type must be rooted")
+                }
+            }
+        }
+
+        let mut visitor = FnDefVisitor {
+            cx: cx,
+            in_new_function: in_new_function,
+        };
+        visit::walk_expr(&mut visitor, &body.value);
+    }
+}
+
+struct FnDefVisitor<'a, 'b: 'a, 'tcx: 'a+'b> {
+    cx: &'a LateContext<'b, 'tcx>,
+    in_new_function: bool,
+}
+
+impl<'a, 'b, 'tcx> visit::Visitor<'tcx> for FnDefVisitor<'a, 'b, 'tcx> {
+    fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
+        let cx = self.cx;
+
+        fn require_rooted(cx: &LateContext, in_new_function: bool, subexpr: &hir::Expr) {
+            let ty = cx.tables.expr_ty(&subexpr);
+            if is_unrooted_ty(cx, ty, in_new_function) {
+                cx.span_lint(UNROOTED_MUST_ROOT,
+                             subexpr.span,
+                             &format!("Expression of type {:?} must be rooted", ty))
+            }
+        }
+
+        match expr.node {
+            /// Trait casts from #[must_root] types are not allowed
+            hir::ExprCast(ref subexpr, _) => require_rooted(cx, self.in_new_function, &*subexpr),
+            // This catches assignments... the main point of this would be to catch mutable
+            // references to `JS<T>`.
+            // FIXME: Enable this? Triggers on certain kinds of uses of DOMRefCell.
+            // hir::ExprAssign(_, ref rhs) => require_rooted(cx, self.in_new_function, &*rhs),
+            // This catches calls; basically, this enforces the constraint that only constructors
+            // can call other constructors.
+            // FIXME: Enable this? Currently triggers with constructs involving DOMRefCell, and
+            // constructs like Vec<JS<T>> and RootedVec<JS<T>>.
+            // hir::ExprCall(..) if !self.in_new_function => {
+            //     require_rooted(cx, self.in_new_function, expr);
+            // }
+            _ => {
+                // TODO(pcwalton): Check generics with a whitelist of allowed generics.
+            }
+        }
+
+        visit::walk_expr(self, expr);
+    }
+
+    fn visit_pat(&mut self, pat: &'tcx hir::Pat) {
+        let cx = self.cx;
+
+        if let hir::PatKind::Binding(hir::BindingMode::BindByValue(_), _, _, _) = pat.node {
+            let ty = cx.tables.pat_ty(pat);
+            if is_unrooted_ty(cx, ty, self.in_new_function) {
+                cx.span_lint(UNROOTED_MUST_ROOT,
+                            pat.span,
+                            &format!("Expression of type {:?} must be rooted", ty))
+            }
+        }
+
+        visit::walk_pat(self, pat);
+    }
+
+    fn visit_fn(&mut self, kind: visit::FnKind<'tcx>, decl: &'tcx hir::FnDecl,
+                body: hir::BodyId, span: codemap::Span, id: ast::NodeId) {
+        if let visit::FnKind::Closure(_) = kind {
+            visit::walk_fn(self, kind, decl, body, span, id);
+        }
+    }
+
+    fn visit_foreign_item(&mut self, _: &'tcx hir::ForeignItem) {}
+    fn visit_ty(&mut self, _: &'tcx hir::Ty) { }
+    fn nested_visit_map<'this>(&'this mut self) -> hir::intravisit::NestedVisitorMap<'this, 'tcx> {
+        hir::intravisit::NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir)
+    }
+}