Trampoline (computing)

In computer programming, the word trampoline has quite a few meanings, and is mostly associated with leap directions (i.e. moving to different code paths).

Contents

1 Low-stage programming 2 High-level programming 3 No-execute stacks 4 See additionally 5 References

Low-level programming[edit]

Trampolines (typically known as oblique jump vectors) are memory locations holding addresses pointing to interrupt service routines, I/O routines, and so forth. Execution jumps into the trampoline and then immediately jumps out, or bounces, therefore the term trampoline. They have many makes use of:

- Trampoline can be utilized to overcome the constraints imposed by a central processing unit (CPU) structure that expects to all the time find vectors in fixed places. - When an operating system is booted on a symmetric multiprocessing (SMP) machine, only one processor, the bootstrap processor, might be active. After the working system has configured itself, it should instruct the opposite processors to jump to a bit of trampoline code that can initialize the processors and await the working system to start scheduling threads on them.

Excessive-level programming[edit]

- As utilized in some Lisp implementations, a trampoline is a loop that iteratively invokes thunk-returning capabilities (continuation-passing fashion). A single trampoline suffices to express all management transfers of a program; a program so expressed is trampolined, or in trampolined style; converting a program to trampolined model is trampolining. Programmers can use trampolined functions to implement tail-recursive perform calls in stack-oriented programming languages.[1]

Continuation-passing model is a well-liked intermediate format for compilers of perform languages, as a result of many control circulation constructs might be elegantly expressed and tail call optimization is easy. When compiling to a language without optimized tail calls, one can keep away from stack progress via a method known as trampolining. The idea is to not make the final continuation call contained in the perform, however to exit and to return the continuation to a trampoline. That trampoline is just a loop that invokes the returned continuations. Therefore, there aren't Trampoline Park nested operate calls and the stack won’t grow.[2]

- In Java, trampoline refers to using reflection to avoid using interior courses, for instance in event listeners. The time overhead of a reflection name is traded for the house overhead of an inside class. Trampolines in Java usually involve the creation of a GenericListener to move occasions to an outer class.[3] - When interfacing items of code with incompatible calling conventions, a trampoline is used to convert the caller's convention into the callee's convention. - In embedded programs, trampolines are quick snippets of code that start up different snippets of code. For instance, fairly than write interrupt handlers totally in assembly language, another option is to jot down interrupt handlers largely in C, and use a brief trampoline to transform the assembly-language interrupt calling convention into the C calling convention.[4] - When passing a callback to a system that expects to call a C perform, however one needs it to execute the tactic of a selected occasion of a category written in C++, one uses a brief trampoline to transform the C function-calling convention to the C++ technique-calling convention. One way of writing such a trampoline is to use a thunk.[5] Another method is to make use of a generic listener.[3]

No-execute stacks[edit]

Some implementations of trampolines cause a lack of no-execute stacks (NX stack). In the GNU Compiler Assortment (GCC) specifically, a nested operate builds a trampoline on the stack at runtime, and then calls the nested operate via the information on stack. The trampoline requires the stack to be executable.

No-execute stacks and nested capabilities are mutually exclusive under GCC. If a nested perform is utilized in the event of a program, then the NX stack is silently lost. GCC presents the -Wtrampolines warning to alert of the condition.

Software engineered using secure development lifecycle often don't permit the usage of nested features because of the loss of NX stacks.[11]

See additionally[edit]

DLL trampolining Retpoline

References[edit]

^ Baker, Henry G. (September 1995). "CONS Mustn't CONS Its Arguments, Half II: Cheney on the M.T.A." ACM SIGPLAN Notices. 30 (9): 17-20. doi:10.1145/214448.214454. S2CID 20720831. Archived from the original on 2016-11-11. ^ Asynchronous programming and continuation-passing fashion in JavaScript - 2ality ^ a b Muller, Hans (2005-01-31). "Asserting Control Over the GUI: Commands, Defaults, and Useful resource Bundles". at present.java.internet. Trampolines. Retrieved 2015-11-06. [1] ^ Link, Joseph M. (2001-09-01). "Trampolines for Embedded Techniques: Minimizing interrupt handlers latency". Dr. Dobb's Journal. Archived from the unique on 2018-05-27. Retrieved 2018-05-26. ^ Stangvik, Einar Otto (2006-08-16). "Thunking in Win32 with C++". Archived from the unique on 2012-10-15. ^ Weiher, Marcel (2004). "Increased Order Messaging (HOM)" (PDF). Archived (PDF) from the original on 2018-05-27. Retrieved 2018-05-26. ^ fuz (2011-11-18). "Implementation of nested functions". StackOverflow. Archived from the unique on 2016-03-29. Retrieved 2018-05-26. ^ "Trampolines for Nested Features". Utilizing the GNU Compiler Collection (GCC). 2018 [2002]. 18.11. Archived from the original on 2018-05-27. Retrieved 2018-05-26. ^ "Nested capabilities". Utilizing the GNU Compiler Assortment (GCC). 2018 [2002]. 6.4. Archived from the original on 2018-05-27. Retrieved 2018-05-26. ^ Breuel, Thomas M. (2013). "Lexical Closures for C++" (PDF). Archived (PDF) from the unique on 2017-12-12. Retrieved 2018-05-26. ^ Walton, Jeffrey; Manico, Jim; Wall, Kevin (2018-03-02) [2013]. "C-Based Toolchain Hardening". The Open Net Software Security Challenge (OWASP). Archived from the unique on 2018-05-27. Retrieved 2018-03-02.