Mobile apps make extensive use of GPUs on smartphones and tablets to access Web content. To support pervasive Web content, we introduce three key OS techniques for binary graphics compatibility necessary to build a real-world system to run iOS and Android apps together on the same smartphone or tablet. First diplomat usage patterns manage resources to bridge proprietary iOS and Android graphics implementations. Second, thread impersonation allows a single thread-specific context to be shared amongst multiple threads using multiple iOS and Android personas. Third, dynamic library replication allows multiple, independent instances of the same library to be loaded in a single process to support iOS apps on Android while using multiple graphics API versions at the same time. We use these techniques to build a system prototype, and demonstrate that it runs widely-used iOS apps, including apps such as Safari that use the popular GPU-accelerated WebKit framework, using a Google Nexus tablet running Android.

The POSIX standard, developed 25 years ago, comprises a set of operating system (OS) abstractions that aid application portability across UNIX-based OSes. While OSes and applications have evolved tremendously over the last 25 years, POSIX, and the basic set of abstractions it provides, has remained largely unchanged. Little has been done to measure how and to what extent traditional POSIX abstractions are being used in modern OSes, and whether new abstractions are taking form, dethroning traditional ones. We explore these questions through a study of POSIX usage in modern desktop and mobile OSes: Android, OS X, and Ubuntu. Our results show that new abstractions are taking form, replacing several prominent traditional abstractions in POSIX. While the changes are driven by common needs and are conceptually similar across the three OSes, they are not converging on any new standard, increasing fragmentation.

We present Cider, an operating system compatibility architecture that can run applications built for different mobile ecosystems, iOS or Android, together on the same smartphone or tablet. Cider enhances the domestic operating system, Android, of a device with kernel-managed, per-thread personas to mimic the application binary interface of a foreign operating system, iOS, enabling it to run unmodified foreign binaries. This is accomplished using a novel combination of binary compatibility techniques including two new mechanisms: compile-time code adaptation, and diplomatic functions. Compile-time code adaptation enables existing unmodified foreign source code to be reused in the domestic kernel, reducing implementation effort required to support multiple binary interfaces for executing domestic and foreign applications. Diplomatic functions leverage per-thread personas, and allow foreign applications to use domestic libraries to access proprietary software and hardware interfaces. We have built a Cider prototype, and demonstrate that it imposes modest performance overhead and runs unmodified iOS and Android applications together on a Google Nexus tablet running the latest version of Android.

The computing landscape is shifting towards mobile devices. To learn about operating systems, it is increasingly important for students to gain hands-on kernel programming experience in these environments, which are quite different from traditional desktops and servers. We present our work at Columbia University to teach operating systems using Android, an open, commercially supported software platform increasingly used on mobile and embedded devices. We introduce a series of five Android kernel programming projects suitable for a one semester introductory operating systems course. Each project teaches a core operating system concept infused with Android or mobile device specific context, such as Android specific process relationships, use of sensors, and design considerations for resource constrained mobile devices. We also introduce an Android virtual laboratory based on virtual appliances, distributed version control, and live demonstrations which gives students hands-on Android experience, with minimal computing infrastructure. We have used these Android kernel programming projects and the Android virtual lab to teach an introductory operating systems course. Although this was our first time teaching the course using Android, over 80% of students surveyed enjoyed using Android and the majority of students preferred Android to traditional desktop development.

Smartphones are increasingly ubiquitous, and many users carry multiple phones to accommodate work, personal, and geographic mobility needs. We present Cells , a virtualization architecture for enabling multiple virtual smartphones to run simultaneously on the same physical cellphone in an isolated, secure manner. Cells introduces a usage model of having one foreground virtual phone and multiple background virtual phones. This model enables a new device namespace mechanism and novel device proxies that integrate with lightweight operating system virtualization to multiplex phone hardware across multiple virtual phones while providing native hardware device performance. Cells virtual phone features include fully accelerated 3D graphics, complete power management features, and full telephony functionality with separately assignable telephone numbers and caller ID support. We have implemented a prototype of Cells that supports multiple Android virtual phones on the same phone. Our performance results demonstrate that Cells imposes only modest runtime and memory overhead, works seamlessly across multiple hardware devices including Google Nexus 1 and Nexus S phones, and transparently runs Android applications at native speed without any modifications.

Smartphones are increasingly ubiquitous, and many users carry multiple phones to accommodate work, personal, and geographic mobility needs. We present Cells, a virtualization architecture for enabling multiple virtual smartphones to run simultaneously on the same physical cellphone in an isolated, secure manner. Cells introduces a usage model of having one foreground virtual phone and multiple background virtual phones. This model enables a new device namespace mechanism and novel device proxies that integrate with lightweight operating system virtualization to multiplex phone hardware across multiple virtual phones while providing native hardware device performance. Cells virtual phone features include fully accelerated 3D graphics, complete power, management features, and full telephony functionality with separately assignable telephone numbers and caller ID support. We have implemented a prototype of Cells that supports multiple Android virtual phones on the same phone. Our performance results demonstrate that Cells imposes only modest runtime and memory overhead, works seamlessly across multiple hardware devices including Google Nexus 1 and Nexus S phones, and transparently runs Android applications at native speed without any modifications.