A common optimisation used in most Dynamic Binary Modification (DBM) systems is trace generation as these traces improve locality and code layout. We describe an optimised code layout for traces as well as present how to adapt the runtime algorithm to generate it. In this way, we manage to reduce the overhead on all the Arm systems evaluated; 5 different microarchitectures.A major source of overhead for DBMs comes from handling indirect branches. Indirect Branch Inlining (IBI) is a mechanism that attempts to avoid this overhead by using predictions about the target of the indirect branch. We analyse the behaviour of the indirect branch inlining and propose a new predictor, Trace Restricted IBI (TRIBI), and how to optimise IBI given the new trace generation algorithm.Our evaluation shows a geometric mean overhead for SPEC CPU2006 of 9% for a Cortex-A53 (in-order core), and for out-of-order cores 11% on an X-Gene-2, 10% on a Cortex-A57, 7% on a Cortex-A72 and 8% on a Cortex-A73, when compared to native execution. This is a reduction of the overhead between 30% to 50% compared to the publicly available DBM systems MAMBO, and, even higher, against DynamoRIO. Using PARSEC 3.0, we evaluate the scalability across threads on the X-Gene-2 system (server machine with the highest number of cores) and show a geomean overhead between 6-8%.CCS Concepts • Software and its engineering → Justin-time compilers; Runtime environments.

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Dynamic Binary Instrumentation (DBI) is a well-established approach for analysing the execution of applications at the level of machine code. DBI frameworks implement a runtime system capable of modifying running applications without access to their source code. These frameworks provide APIs used by DBI tools to plug in their specific analysis and instrumentation routines. However, the dynamic instrumentation needed by these DBI tools is either challenging to implement, and/or introduces a significant performance overhead.An added complexity beyond the well studied scenario of x86 and x86-64, is that state-of-the-art Arm systems (i.e. Arm v8) introduced a distinct 64-bit execution mode with a new redesigned instruction set. Thus, Arm v8 is a computer architecture which contains three instruction sets. This further complicates the development of DBI tools which can work for both 32-bit Arm (includes the A32 and T32 instruction sets), and 64-bit (the A64 instruction set).This paper presents the design of a novel DBI framework API that provides support both for portable (across A32, T32 and A64), and for native-code-level analysis and instrumentation, which can be intermixed freely. This API allows DBI tool developers to balance performance and productivity at a fine-grain level. The API is implemented on top of the MAMBO DBI system.CCS Concepts • Software and its engineering → Justin-time compilers; Runtime environments.