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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * 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/. */
+
+#ifndef js_friend_StackLimits_h
+#define js_friend_StackLimits_h
+
+#include "mozilla/Attributes.h" // MOZ_ALWAYS_INLINE, MOZ_COLD
+#include "mozilla/Likely.h" // MOZ_LIKELY
+#include "mozilla/Variant.h" // mozilla::Variant, mozilla::AsVariant
+
+#include <stddef.h> // size_t
+
+#include "jstypes.h" // JS_PUBLIC_API
+
+#include "js/HeapAPI.h" // JS::StackKind, JS::StackForTrustedScript, JS::StackForUntrustedScript
+#include "js/RootingAPI.h" // JS::RootingContext
+#include "js/Stack.h" // JS::NativeStackLimit
+#include "js/Utility.h" // JS_STACK_OOM_POSSIBLY_FAIL
+
+struct JS_PUBLIC_API JSContext;
+
+#ifndef JS_STACK_GROWTH_DIRECTION
+# ifdef __hppa
+# define JS_STACK_GROWTH_DIRECTION (1)
+# else
+# define JS_STACK_GROWTH_DIRECTION (-1)
+# endif
+#endif
+
+namespace js {
+
+class FrontendContext;
+
+#ifdef __wasi__
+extern MOZ_COLD JS_PUBLIC_API void IncWasiRecursionDepth(JSContext* cx);
+extern MOZ_COLD JS_PUBLIC_API void DecWasiRecursionDepth(JSContext* cx);
+extern MOZ_COLD JS_PUBLIC_API bool CheckWasiRecursionLimit(JSContext* cx);
+
+extern MOZ_COLD JS_PUBLIC_API void IncWasiRecursionDepth(FrontendContext* fc);
+extern MOZ_COLD JS_PUBLIC_API void DecWasiRecursionDepth(FrontendContext* fc);
+extern MOZ_COLD JS_PUBLIC_API bool CheckWasiRecursionLimit(FrontendContext* fc);
+#endif // __wasi__
+
+// AutoCheckRecursionLimit can be used to check whether we're close to using up
+// the C++ stack.
+//
+// Typical usage is like this:
+//
+// AutoCheckRecursionLimit recursion(cx);
+// if (!recursion.check(cx)) {
+// return false;
+// }
+//
+// The check* functions return |false| if we are close to the stack limit.
+// They also report an overrecursion error, except for the DontReport variants.
+//
+// The checkSystem variant gives us a little extra space so we can ensure that
+// crucial code is able to run.
+//
+// checkConservative allows less space than any other check, including a safety
+// buffer (as in, it uses the untrusted limit and subtracts a little more from
+// it).
+class MOZ_RAII AutoCheckRecursionLimit {
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkLimitImpl(
+ JS::NativeStackLimit limit, void* sp) const;
+
+ MOZ_ALWAYS_INLINE JS::NativeStackLimit getStackLimitSlow(JSContext* cx) const;
+ MOZ_ALWAYS_INLINE JS::NativeStackLimit getStackLimitHelper(
+ JSContext* cx, JS::StackKind kind, int extraAllowance) const;
+
+ JS::NativeStackLimit getStackLimit(FrontendContext* fc) const;
+
+ JS_PUBLIC_API JS::StackKind stackKindForCurrentPrincipal(JSContext* cx) const;
+
+ JS_PUBLIC_API void assertMainThread(JSContext* cx) const;
+
+#ifdef __wasi__
+ // The JSContext outlives AutoCheckRecursionLimit so it is safe to use raw
+ // pointer here.
+ mozilla::Variant<JSContext*, FrontendContext*> context_;
+#endif // __wasi__
+
+ public:
+ explicit MOZ_ALWAYS_INLINE AutoCheckRecursionLimit(JSContext* cx)
+#ifdef __wasi__
+ : context_(mozilla::AsVariant(cx))
+#endif // __wasi__
+ {
+#ifdef __wasi__
+ incWasiRecursionDepth();
+#endif // __wasi__
+ }
+
+ explicit MOZ_ALWAYS_INLINE AutoCheckRecursionLimit(FrontendContext* fc)
+#ifdef __wasi__
+ : context_(mozilla::AsVariant(fc))
+#endif // __wasi__
+ {
+#ifdef __wasi__
+ incWasiRecursionDepth();
+#endif // __wasi__
+ }
+
+ MOZ_ALWAYS_INLINE ~AutoCheckRecursionLimit() {
+#ifdef __wasi__
+ decWasiRecursionDepth();
+#endif // __wasi__
+ }
+
+#ifdef __wasi__
+ MOZ_ALWAYS_INLINE void incWasiRecursionDepth() {
+ if (context_.is<JSContext*>()) {
+ JSContext* cx = context_.as<JSContext*>();
+ IncWasiRecursionDepth(cx);
+ } else {
+ FrontendContext* fc = context_.as<FrontendContext*>();
+ IncWasiRecursionDepth(fc);
+ }
+ }
+
+ MOZ_ALWAYS_INLINE void decWasiRecursionDepth() {
+ if (context_.is<JSContext*>()) {
+ JSContext* cx = context_.as<JSContext*>();
+ DecWasiRecursionDepth(cx);
+ } else {
+ FrontendContext* fc = context_.as<FrontendContext*>();
+ DecWasiRecursionDepth(fc);
+ }
+ }
+
+ MOZ_ALWAYS_INLINE bool checkWasiRecursionLimit() const {
+ if (context_.is<JSContext*>()) {
+ JSContext* cx = context_.as<JSContext*>();
+ if (!CheckWasiRecursionLimit(cx)) {
+ return false;
+ }
+ } else {
+ FrontendContext* fc = context_.as<FrontendContext*>();
+ if (!CheckWasiRecursionLimit(fc)) {
+ return false;
+ }
+ }
+
+ return true;
+ }
+#endif // __wasi__
+
+ AutoCheckRecursionLimit(const AutoCheckRecursionLimit&) = delete;
+ void operator=(const AutoCheckRecursionLimit&) = delete;
+
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool check(JSContext* cx) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool check(FrontendContext* fc) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkDontReport(JSContext* cx) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkDontReport(
+ FrontendContext* fc) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkWithExtra(JSContext* cx,
+ size_t extra) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkWithStackPointerDontReport(
+ JSContext* cx, void* sp) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkWithStackPointerDontReport(
+ FrontendContext* fc, void* sp) const;
+
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkConservative(JSContext* cx) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkConservativeDontReport(
+ JSContext* cx) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkConservativeDontReport(
+ JS::NativeStackLimit limit) const;
+
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkSystem(JSContext* cx) const;
+ [[nodiscard]] MOZ_ALWAYS_INLINE bool checkSystemDontReport(
+ JSContext* cx) const;
+};
+
+extern MOZ_COLD JS_PUBLIC_API void ReportOverRecursed(JSContext* maybecx);
+extern MOZ_COLD JS_PUBLIC_API void ReportOverRecursed(FrontendContext* fc);
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkLimitImpl(
+ JS::NativeStackLimit limit, void* sp) const {
+ JS_STACK_OOM_POSSIBLY_FAIL();
+
+#ifdef __wasi__
+ if (!checkWasiRecursionLimit()) {
+ return false;
+ }
+#endif // __wasi__
+
+#if JS_STACK_GROWTH_DIRECTION > 0
+ return MOZ_LIKELY(JS::NativeStackLimit(sp) < limit);
+#else
+ return MOZ_LIKELY(JS::NativeStackLimit(sp) > limit);
+#endif
+}
+
+MOZ_ALWAYS_INLINE JS::NativeStackLimit
+AutoCheckRecursionLimit::getStackLimitSlow(JSContext* cx) const {
+ JS::StackKind kind = stackKindForCurrentPrincipal(cx);
+ return getStackLimitHelper(cx, kind, 0);
+}
+
+MOZ_ALWAYS_INLINE JS::NativeStackLimit
+AutoCheckRecursionLimit::getStackLimitHelper(JSContext* cx, JS::StackKind kind,
+ int extraAllowance) const {
+ assertMainThread(cx);
+ JS::NativeStackLimit limit =
+ JS::RootingContext::get(cx)->nativeStackLimit[kind];
+#if JS_STACK_GROWTH_DIRECTION > 0
+ limit += extraAllowance;
+#else
+ limit -= extraAllowance;
+#endif
+ return limit;
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::check(JSContext* cx) const {
+ if (MOZ_UNLIKELY(!checkDontReport(cx))) {
+ ReportOverRecursed(cx);
+ return false;
+ }
+ return true;
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::check(
+ FrontendContext* fc) const {
+ if (MOZ_UNLIKELY(!checkDontReport(fc))) {
+ ReportOverRecursed(fc);
+ return false;
+ }
+ return true;
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkDontReport(
+ JSContext* cx) const {
+ int stackDummy;
+ return checkWithStackPointerDontReport(cx, &stackDummy);
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkDontReport(
+ FrontendContext* fc) const {
+ int stackDummy;
+ return checkWithStackPointerDontReport(fc, &stackDummy);
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkWithStackPointerDontReport(
+ JSContext* cx, void* sp) const {
+ // getStackLimitSlow(cx) is pretty slow because it has to do an uninlined
+ // call to stackKindForCurrentPrincipal to determine which stack limit to
+ // use. To work around this, check the untrusted limit first to avoid the
+ // overhead in most cases.
+ JS::NativeStackLimit untrustedLimit =
+ getStackLimitHelper(cx, JS::StackForUntrustedScript, 0);
+ if (MOZ_LIKELY(checkLimitImpl(untrustedLimit, sp))) {
+ return true;
+ }
+ return checkLimitImpl(getStackLimitSlow(cx), sp);
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkWithStackPointerDontReport(
+ FrontendContext* fc, void* sp) const {
+ return checkLimitImpl(getStackLimit(fc), sp);
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkWithExtra(
+ JSContext* cx, size_t extra) const {
+ char stackDummy;
+ char* sp = &stackDummy;
+#if JS_STACK_GROWTH_DIRECTION > 0
+ sp += extra;
+#else
+ sp -= extra;
+#endif
+ if (MOZ_UNLIKELY(!checkWithStackPointerDontReport(cx, sp))) {
+ ReportOverRecursed(cx);
+ return false;
+ }
+ return true;
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkSystem(
+ JSContext* cx) const {
+ if (MOZ_UNLIKELY(!checkSystemDontReport(cx))) {
+ ReportOverRecursed(cx);
+ return false;
+ }
+ return true;
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkSystemDontReport(
+ JSContext* cx) const {
+ JS::NativeStackLimit limit =
+ getStackLimitHelper(cx, JS::StackForSystemCode, 0);
+ int stackDummy;
+ return checkLimitImpl(limit, &stackDummy);
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkConservative(
+ JSContext* cx) const {
+ if (MOZ_UNLIKELY(!checkConservativeDontReport(cx))) {
+ ReportOverRecursed(cx);
+ return false;
+ }
+ return true;
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkConservativeDontReport(
+ JSContext* cx) const {
+ JS::NativeStackLimit limit = getStackLimitHelper(
+ cx, JS::StackForUntrustedScript, -4096 * int(sizeof(size_t)));
+ int stackDummy;
+ return checkLimitImpl(limit, &stackDummy);
+}
+
+MOZ_ALWAYS_INLINE bool AutoCheckRecursionLimit::checkConservativeDontReport(
+ JS::NativeStackLimit limit) const {
+ int stackDummy;
+ return checkLimitImpl(limit, &stackDummy);
+}
+
+} // namespace js
+
+#endif // js_friend_StackLimits_h