compiler/rustc_passes/src/naked_functions.rs

   1 //! Checks validity of naked functions.
   2
   3 use rustc_ast::{Attribute, InlineAsmOptions};
   4 use rustc_errors::{struct_span_err, Applicability};
   5 use rustc_hir as hir;
   6 use rustc_hir::def_id::LocalDefId;
   7 use rustc_hir::intravisit::{FnKind, Visitor};
   8 use rustc_hir::{ExprKind, HirId, InlineAsmOperand, StmtKind};
   9 use rustc_middle::ty::query::Providers;
  10 use rustc_middle::ty::TyCtxt;
  11 use rustc_session::lint::builtin::UNDEFINED_NAKED_FUNCTION_ABI;
  12 use rustc_span::symbol::sym;
  13 use rustc_span::Span;
  14 use rustc_target::spec::abi::Abi;
  15
  16 fn check_mod_naked_functions(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  17     tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckNakedFunctions { tcx });
  18 }
  19
  20 pub(crate) fn provide(providers: &mut Providers) {
  21     *providers = Providers { check_mod_naked_functions, ..*providers };
  22 }
  23
  24 struct CheckNakedFunctions<'tcx> {
  25     tcx: TyCtxt<'tcx>,
  26 }
  27
  28 impl<'tcx> Visitor<'tcx> for CheckNakedFunctions<'tcx> {
  29     fn visit_fn(
  30         &mut self,
  31         fk: FnKind<'_>,
  32         _fd: &'tcx hir::FnDecl<'tcx>,
  33         body_id: hir::BodyId,
  34         span: Span,
  35         hir_id: HirId,
  36     ) {
  37         let ident_span;
  38         let fn_header;
  39
  40         match fk {
  41             FnKind::Closure => {
  42                 // Closures with a naked attribute are rejected during attribute
  43                 // check. Don't validate them any further.
  44                 return;
  45             }
  46             FnKind::ItemFn(ident, _, ref header, ..) => {
  47                 ident_span = ident.span;
  48                 fn_header = header;
  49             }
  50
  51             FnKind::Method(ident, ref sig, ..) => {
  52                 ident_span = ident.span;
  53                 fn_header = &sig.header;
  54             }
  55         }
  56
  57         let attrs = self.tcx.hir().attrs(hir_id);
  58         let naked = attrs.iter().any(|attr| attr.has_name(sym::naked));
  59         if naked {
  60             let body = self.tcx.hir().body(body_id);
  61             check_abi(self.tcx, hir_id, fn_header.abi, ident_span);
  62             check_no_patterns(self.tcx, body.params);
  63             check_no_parameters_use(self.tcx, body);
  64             check_asm(self.tcx, body, span);
  65             check_inline(self.tcx, attrs);
  66         }
  67     }
  68 }
  69
  70 /// Check that the function isn't inlined.
  71 fn check_inline(tcx: TyCtxt<'_>, attrs: &[Attribute]) {
  72     for attr in attrs.iter().filter(|attr| attr.has_name(sym::inline)) {
  73         tcx.sess.struct_span_err(attr.span, "naked functions cannot be inlined").emit();
  74     }
  75 }
  76
  77 /// Checks that function uses non-Rust ABI.
  78 fn check_abi(tcx: TyCtxt<'_>, hir_id: HirId, abi: Abi, fn_ident_span: Span) {
  79     if abi == Abi::Rust {
  80         tcx.struct_span_lint_hir(UNDEFINED_NAKED_FUNCTION_ABI, hir_id, fn_ident_span, |lint| {
  81             lint.build("Rust ABI is unsupported in naked functions").emit();
  82         });
  83     }
  84 }
  85
  86 /// Checks that parameters don't use patterns. Mirrors the checks for function declarations.
  87 fn check_no_patterns(tcx: TyCtxt<'_>, params: &[hir::Param<'_>]) {
  88     for param in params {
  89         match param.pat.kind {
  90             hir::PatKind::Wild
  91             | hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, _, None) => {}
  92             _ => {
  93                 tcx.sess
  94                     .struct_span_err(
  95                         param.pat.span,
  96                         "patterns not allowed in naked function parameters",
  97                     )
  98                     .emit();
  99             }
 100         }
 101     }
 102 }
 103
 104 /// Checks that function parameters aren't used in the function body.
 105 fn check_no_parameters_use<'tcx>(tcx: TyCtxt<'tcx>, body: &'tcx hir::Body<'tcx>) {
 106     let mut params = hir::HirIdSet::default();
 107     for param in body.params {
 108         param.pat.each_binding(|_binding_mode, hir_id, _span, _ident| {
 109             params.insert(hir_id);
 110         });
 111     }
 112     CheckParameters { tcx, params }.visit_body(body);
 113 }
 114
 115 struct CheckParameters<'tcx> {
 116     tcx: TyCtxt<'tcx>,
 117     params: hir::HirIdSet,
 118 }
 119
 120 impl<'tcx> Visitor<'tcx> for CheckParameters<'tcx> {
 121     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 122         if let hir::ExprKind::Path(hir::QPath::Resolved(
 123             _,
 124             hir::Path { res: hir::def::Res::Local(var_hir_id), .. },
 125         )) = expr.kind
 126         {
 127             if self.params.contains(var_hir_id) {
 128                 self.tcx
 129                     .sess
 130                     .struct_span_err(
 131                         expr.span,
 132                         "referencing function parameters is not allowed in naked functions",
 133                     )
 134                     .help("follow the calling convention in asm block to use parameters")
 135                     .emit();
 136                 return;
 137             }
 138         }
 139         hir::intravisit::walk_expr(self, expr);
 140     }
 141 }
 142
 143 /// Checks that function body contains a single inline assembly block.
 144 fn check_asm<'tcx>(tcx: TyCtxt<'tcx>, body: &'tcx hir::Body<'tcx>, fn_span: Span) {
 145     let mut this = CheckInlineAssembly { tcx, items: Vec::new() };
 146     this.visit_body(body);
 147     if let [(ItemKind::Asm | ItemKind::Err, _)] = this.items[..] {
 148         // Ok.
 149     } else {
 150         let mut diag = struct_span_err!(
 151             tcx.sess,
 152             fn_span,
 153             E0787,
 154             "naked functions must contain a single asm block"
 155         );
 156
 157         let mut must_show_error = false;
 158         let mut has_asm = false;
 159         let mut has_err = false;
 160         for &(kind, span) in &this.items {
 161             match kind {
 162                 ItemKind::Asm if has_asm => {
 163                     must_show_error = true;
 164                     diag.span_label(span, "multiple asm blocks are unsupported in naked functions");
 165                 }
 166                 ItemKind::Asm => has_asm = true,
 167                 ItemKind::NonAsm => {
 168                     must_show_error = true;
 169                     diag.span_label(span, "non-asm is unsupported in naked functions");
 170                 }
 171                 ItemKind::Err => has_err = true,
 172             }
 173         }
 174
 175         // If the naked function only contains a single asm block and a non-zero number of
 176         // errors, then don't show an additional error. This allows for appending/prepending
 177         // `compile_error!("...")` statements and reduces error noise.
 178         if must_show_error || !has_err {
 179             diag.emit();
 180         } else {
 181             diag.cancel();
 182         }
 183     }
 184 }
 185
 186 struct CheckInlineAssembly<'tcx> {
 187     tcx: TyCtxt<'tcx>,
 188     items: Vec<(ItemKind, Span)>,
 189 }
 190
 191 #[derive(Copy, Clone)]
 192 enum ItemKind {
 193     Asm,
 194     NonAsm,
 195     Err,
 196 }
 197
 198 impl<'tcx> CheckInlineAssembly<'tcx> {
 199     fn check_expr(&mut self, expr: &'tcx hir::Expr<'tcx>, span: Span) {
 200         match expr.kind {
 201             ExprKind::Box(..)
 202             | ExprKind::ConstBlock(..)
 203             | ExprKind::Array(..)
 204             | ExprKind::Call(..)
 205             | ExprKind::MethodCall(..)
 206             | ExprKind::Tup(..)
 207             | ExprKind::Binary(..)
 208             | ExprKind::Unary(..)
 209             | ExprKind::Lit(..)
 210             | ExprKind::Cast(..)
 211             | ExprKind::Type(..)
 212             | ExprKind::Loop(..)
 213             | ExprKind::Match(..)
 214             | ExprKind::If(..)
 215             | ExprKind::Closure { .. }
 216             | ExprKind::Assign(..)
 217             | ExprKind::AssignOp(..)
 218             | ExprKind::Field(..)
 219             | ExprKind::Index(..)
 220             | ExprKind::Path(..)
 221             | ExprKind::AddrOf(..)
 222             | ExprKind::Let(..)
 223             | ExprKind::Break(..)
 224             | ExprKind::Continue(..)
 225             | ExprKind::Ret(..)
 226             | ExprKind::Struct(..)
 227             | ExprKind::Repeat(..)
 228             | ExprKind::Yield(..) => {
 229                 self.items.push((ItemKind::NonAsm, span));
 230             }
 231
 232             ExprKind::InlineAsm(ref asm) => {
 233                 self.items.push((ItemKind::Asm, span));
 234                 self.check_inline_asm(asm, span);
 235             }
 236
 237             ExprKind::DropTemps(..) | ExprKind::Block(..) => {
 238                 hir::intravisit::walk_expr(self, expr);
 239             }
 240
 241             ExprKind::Err => {
 242                 self.items.push((ItemKind::Err, span));
 243             }
 244         }
 245     }
 246
 247     fn check_inline_asm(&self, asm: &'tcx hir::InlineAsm<'tcx>, span: Span) {
 248         let unsupported_operands: Vec<Span> = asm
 249             .operands
 250             .iter()
 251             .filter_map(|&(ref op, op_sp)| match op {
 252                 InlineAsmOperand::Const { .. }
 253                 | InlineAsmOperand::SymFn { .. }
 254                 | InlineAsmOperand::SymStatic { .. } => None,
 255                 InlineAsmOperand::In { .. }
 256                 | InlineAsmOperand::Out { .. }
 257                 | InlineAsmOperand::InOut { .. }
 258                 | InlineAsmOperand::SplitInOut { .. } => Some(op_sp),
 259             })
 260             .collect();
 261         if !unsupported_operands.is_empty() {
 262             struct_span_err!(
 263                 self.tcx.sess,
 264                 unsupported_operands,
 265                 E0787,
 266                 "only `const` and `sym` operands are supported in naked functions",
 267             )
 268             .emit();
 269         }
 270
 271         let unsupported_options: Vec<&'static str> = [
 272             (InlineAsmOptions::MAY_UNWIND, "`may_unwind`"),
 273             (InlineAsmOptions::NOMEM, "`nomem`"),
 274             (InlineAsmOptions::NOSTACK, "`nostack`"),
 275             (InlineAsmOptions::PRESERVES_FLAGS, "`preserves_flags`"),
 276             (InlineAsmOptions::PURE, "`pure`"),
 277             (InlineAsmOptions::READONLY, "`readonly`"),
 278         ]
 279         .iter()
 280         .filter_map(|&(option, name)| if asm.options.contains(option) { Some(name) } else { None })
 281         .collect();
 282
 283         if !unsupported_options.is_empty() {
 284             struct_span_err!(
 285                 self.tcx.sess,
 286                 span,
 287                 E0787,
 288                 "asm options unsupported in naked functions: {}",
 289                 unsupported_options.join(", ")
 290             )
 291             .emit();
 292         }
 293
 294         if !asm.options.contains(InlineAsmOptions::NORETURN) {
 295             let last_span = asm
 296                 .operands
 297                 .last()
 298                 .map_or_else(|| asm.template_strs.last().unwrap().2, |op| op.1)
 299                 .shrink_to_hi();
 300
 301             struct_span_err!(
 302                 self.tcx.sess,
 303                 span,
 304                 E0787,
 305                 "asm in naked functions must use `noreturn` option"
 306             )
 307             .span_suggestion(
 308                 last_span,
 309                 "consider specifying that the asm block is responsible \
 310                 for returning from the function",
 311                 ", options(noreturn)",
 312                 Applicability::MachineApplicable,
 313             )
 314             .emit();
 315         }
 316     }
 317 }
 318
 319 impl<'tcx> Visitor<'tcx> for CheckInlineAssembly<'tcx> {
 320     fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) {
 321         match stmt.kind {
 322             StmtKind::Item(..) => {}
 323             StmtKind::Local(..) => {
 324                 self.items.push((ItemKind::NonAsm, stmt.span));
 325             }
 326             StmtKind::Expr(ref expr) | StmtKind::Semi(ref expr) => {
 327                 self.check_expr(expr, stmt.span);
 328             }
 329         }
 330     }
 331
 332     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 333         self.check_expr(&expr, expr.span);
 334     }
 335 }