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Diffstat (limited to 'js/public/friend/StackLimits.h')
| -rw-r--r-- | js/public/friend/StackLimits.h | 323 |
1 files changed, 323 insertions, 0 deletions
diff --git a/js/public/friend/StackLimits.h b/js/public/friend/StackLimits.h new file mode 100644 index 0000000000..061c0efcf0 --- /dev/null +++ b/js/public/friend/StackLimits.h @@ -0,0 +1,323 @@ +/* -*- 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 |