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Bare machine
Bare machine
Bare machine
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In information technology, bare machine (or bare-metal computer) is a computer which has no operating system.[1] The software executed by a bare machine, commonly called a "bare metal program" or "bare metal application",[2] is designed to interact directly with hardware. Bare machines are widely used in embedded systems, particularly in cases where resources are limited or high performance is required.[3]

Advantages

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Typically, a bare-metal application will run faster, use less memory and be more power efficient than an equivalent program that relies on an operating system, due to the inherent overhead imposed by system calls. For example, hardware inputs and outputs are directly accessible to bare metal software, whereas they must usually be accessed through system calls when using an OS.[4]

Disadvantages

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Bare metal applications typically require more effort to develop because operating system services such as memory management and task scheduling are not available.

Debugging a bare-metal program may be complicated by factors such as:

  • Lack of a standard output.
  • The target machine may differ from the hardware used for program development (e.g., emulator, simulator). This forces setting up a way to load the bare-metal program onto the target (flashing), start the program execution and access the target resources.

Bare-metal programming is generally done using a close-to-hardware language such as Rust, C++, C, or assembly language.[5]

Examples

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Early computers

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Early computers, such as the PDP-11, allowed programmers to load a program, supplied in machine code, to RAM. The resulting operation of the program could be monitored by lights, and output derived from magnetic tape, print devices, or storage.

Amdahl UTS's performance improves by 25% when run on bare metal without VM, the company said in 1986.[6]

Embedded systems

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The Wikibook Embedded Systems has a page on the topic of: Super Loop Architecture

Bare machine programming is a common practice in embedded systems, in which microcontrollers or microprocessors boot directly into monolithic, single-purpose software without loading an operating system. Such embedded software can vary in structure. For example, one such program paradigm, known as "foreground-background" or "superloop" architecture, consists of an infinite main loop in which each task is executed sequentially.[7]

See also

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References

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Further reading

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Bare machine

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from Grokipedia
A bare machine, in the context of , refers to a hardware system—typically consisting of a (CPU), memory, and (I/O) devices—upon which software applications execute directly without the intervention of an operating system (OS) or kernel. This paradigm, known as Bare Machine Computing (BMC), enables self-supporting applications, termed Application Objects (AOs), to manage hardware resources autonomously, using monolithic executables stored on like USB drives. The concept of bare machine computing traces its roots to the , when early computers operated without modern OS layers, but the formalized BMC paradigm emerged in the early as a response to the growing complexities and vulnerabilities introduced by traditional OS-dependent systems. Pioneering work by researchers such as Uzo Okafor and Ramesh K. Karne, published in 2013, outlined the elimination of OS to allow applications to interface directly with hardware, fostering "ownerless" devices free from persistent storage dependencies. Subsequent studies, including IEEE explorations in remote collaboration and system internals, have built on this foundation, demonstrating practical implementations on platforms like bare PCs and clusters. At its core, bare machine computing operates on principles of and direct control: only a single application runs at a time, leveraging generic interfaces for memory allocation, network communication, and I/O without dynamic libraries, system calls, or virtual machines. This approach enforces a closed, authenticated environment—often termed the "Bare Machine "—where access is restricted to verified users and sites, with no support for downloads, scripts, or open ports. Hardware remains "bare" by design, booting from external media to avoid fixed storage vulnerabilities, and applications are statically linked to minimize external dependencies. Bare machine systems offer significant advantages in , , and longevity: by removing the OS, they inherently mitigate a wide array of cyberattacks, such as buffer overflows, , and infections, rendering 20 out of 22 common threats ineffective through the absence of exploitable layers. This results in smaller code footprints, lower , and reduced hardware obsolescence, as applications are not tied to evolving OS versions. Demonstrated applications include web servers, VoIP soft-phones, chat systems, and educational tools for system internals, with ongoing validating their resilience in pervasive and high-security contexts as of 2024.

Definition and Fundamentals

Core Definition

A bare machine, also referred to as bare-metal , is a system in which application code executes directly on the physical hardware without an intervening operating , kernel, or runtime environment. This paradigm, known as Bare Machine (BMC), allows software to assume complete control of the resources shortly after the boot process, typically initiated by such as the . In a bare machine setup, core components involve direct interaction with the (CPU), memory, and peripheral devices through or low-level . Applications are generally compiled as a single, statically linked monolithic —often under 2 MB in size—that manages all hardware communications autonomously, eliminating dependencies on external libraries or . This approach contrasts with virtual machines or hosted environments, which run within emulated or abstracted layers atop a host operating system, whereas bare machines emphasize execution on unaltered physical hardware. Effective development for bare machines necessitates comprehension of binary execution, whereby the CPU fetches and processes machine instructions directly from , and mechanisms, such as the , to handle hardware events like device signals without OS mediation.

Key Characteristics

A bare machine provides direct hardware control, allowing applications to interact with the underlying hardware without any intervening abstraction layers such as an operating system or kernel, which results in minimal execution overhead. In this , programmers have full authority over hardware resources, enabling precise manipulation of components like processors and peripherals through low-level instructions. Resource management in a bare machine is handled entirely by the application itself, involving manual allocation and deallocation of , operations, and cycles without reliance on system-provided services. Applications are typically compiled into a single, statically linked that incorporates all necessary components, ensuring self-containment and eliminating dependencies on external libraries or mechanisms. This approach customizes the layout and hardware access to the specific needs of the program, optimizing for efficiency in resource-constrained environments. The execution model of a bare machine exhibits deterministic , characterized by predictable timing and sequencing due to the absence of operating scheduling, interrupts from other processes, or preemptive multitasking. Only the intended application functions operate, providing consistent without variability introduced by shared resources. Key constraints of bare machines include the inherent lack of built-in multitasking capabilities, requiring any concurrent operations to be implemented manually within the single application suite, which limits for complex, multi-process workloads. Additionally, without an operating to mediate errors or provide fault isolation, bare machines are particularly vulnerable to hardware faults, such as corruption or device failures, potentially leading to instability if not explicitly handled by the .

Historical Development

Origins in Early Computing

The concept of bare machine execution emerged in the 1940s with the development of the first electronic digital computers, which operated without any operating system layer, running programs directly on the hardware. The (Electronic Numerical Integrator and Computer), completed in 1945 at the , exemplified this approach; it used over 17,000 vacuum tubes and was programmed by manually setting switches and plugging cables into panels, allowing instructions to execute directly via the machine's wiring and electronic circuitry. Similarly, the , delivered in 1951 as the first commercially available computer, relied on direct hardware control, with programs loaded via or punch cards and executed without software mediation, consuming about 125 kilowatts of power across its 5,000 vacuum tubes. This bare execution was necessitated by the technological constraints of vacuum-tube computers and punch-card input systems prevalent in the era. Vacuum tubes served as the core elements, enabling electronic computation but requiring manual intervention for setup, as there were no abstracted layers for or program loading; punch cards, inherited from earlier tabulating machines, provided the primary means of and instruction input, fed directly into the for sequential without intermediary software. A pivotal influence was John von Neumann's "First Draft of a Report on the " in 1945, which proposed the stored-program where instructions and data resided in the same memory, fundamentally enabling software to run directly on hardware without reconfiguration for each task. This design shift from fixed-wiring machines like to modifiable memory laid the groundwork for bare machine operation in subsequent systems. Prior to the 1960s, systems further characterized this era, where jobs were compiled onto punch cards or tapes and submitted in groups for direct hardware execution, simulating bare machine efficiency by minimizing operator intervention between runs.

Evolution Through Mid-20th Century

In the , the computing landscape began shifting toward more sophisticated operating systems, such as , a pioneering system developed jointly by MIT, , and starting in 1965, which introduced concepts like hierarchical file systems and protected memory that influenced later designs. Despite this, bare machine programming—executing code directly on hardware without an intervening OS—persisted in for applications demanding simplicity and low overhead, exemplified by the PDP-8, introduced by in 1965 as the first commercially successful . The PDP-8, with its 12-bit architecture and compact design, was often programmed in machine language via front-panel switches or paper tape loaders, bypassing full OSes to control laboratory instruments, process control, or real-time tasks where resource constraints favored direct hardware interaction. This approach contrasted with the emerging precursors to Unix, which originated in the late at as a response to ' complexity, yet even early Unix implementations on systems like the still relied on minimal loaders akin to bare machine setups for initial bootstrapping. Entering the 1970s and 1980s, bare machine concepts played a crucial role in the revolution, particularly with devices like the , released in 1974 as an enhanced 8-bit CPU that powered early s such as the 8800. These systems frequently operated in bare metal mode, with programmers writing in to toggle switches for loading and executing code directly, enabling hobbyist and industrial applications without OS overhead. This era marked a bridge to embedded technologies, where —non-volatile code running on bare hardware—became standard for controlling peripherals in devices like early kits and process controllers, leveraging the 8080's low power and integration to embed computing in machinery. As general-purpose evolved with the widespread adoption of and multitasking OSes in the and , bare machine programming declined for mainstream applications due to the need for resource sharing and abstraction layers, shifting focus from direct hardware manipulation to higher-level . However, it endured in specialized hardware, such as handheld calculators from manufacturers like and , which used custom microprocessors executing fixed bare machine code for arithmetic operations without any OS, prioritizing efficiency in battery-powered, single-task environments. Similarly, industrial controllers and early embedded systems in the and 1980s relied on bare to manage real-time inputs and outputs in appliances, , and machinery, where predictability trumped the flexibility of full OSes. A pivotal development in the 1980s was the creation of the (Basic Input/Output System) for 's personal computers, first implemented in the IBM PC (model 5150) released in 1981, providing a minimal firmware layer that interfaced directly with hardware components like keyboards, displays, and disks before loading an OS. Developed by engineers using tools like Intel's ISIS-II assembler and completed on April 24, 1981, the embodied bare machine principles by executing POST (Power-On Self-Test) routines and interrupt handlers in ROM, allowing compatible software to run on varied hardware configurations while abstracting low-level details. This approach influenced subsequent PC clones and laid groundwork for evolutions like in later decades, maintaining a thin bare layer amid growing OS complexity.

Technical Implementation

Hardware Interaction

In Bare Machine Computing (BMC), the boot process utilizes the on x86/x64 PCs to load from a removable USB device, starting with the at 0x7C00, which contains initial code (prcycle.exe) to prepare the system before transferring control to the main Application Object (AO) executable loaded at 0x00111000. This process switches from to , sets up the (GDT) for , and initializes essential hardware without an intermediary or OS, ensuring the machine remains "bare" by avoiding fixed storage. The AO, a monolithic suite, then directly manages hardware resources autonomously. Memory addressing in BMC relies on direct physical addressing in a single , without , paging, or dynamic allocation beyond static /data/stack regions. Applications are loaded at predefined physical locations, such as 0x00111000 for the main , granting full access to RAM while using ROM or flash minimally for initial . Programmers use absolute pointers for precision, managing via custom routines within the AO, such as circular buffers for , to support multi-tasking events without OS abstractions. This approach ensures portability across x86 hardware but requires manual alignment to processor constraints like 4 KB pages in . CPU control in BMC involves direct configuration of x86 registers and modes by the AO, including program counter management, task switching via GDT/LDT entries, and privilege levels without scheduler interference. Developers write to control registers using inline assembly, such as setting up protected mode with instructions like LGDT (Load Global Descriptor Table) and enabling interrupts via CLI/STI, to handle execution in ring 0 (kernel mode equivalent). Timing is controlled through hardware-specific latencies, with the AO implementing event-driven loops for deterministic behavior, accounting for instruction cycles (e.g., most x86 instructions in 1-5 cycles) in resource-constrained setups. Input/output (I/O) operations in BMC are handled directly by the AO through custom bare device drivers embedded in the executable, using polling or interrupts for peripherals like network cards, USB devices, keyboards, and displays, without abstracted drivers. For instance, Ethernet I/O employs memory-mapped registers and circular lists (e.g., 4096 entries) for packet handling via direct port I/O instructions like IN/OUT on x86. Interrupt-driven methods configure the (PIC) or Advanced PIC (APIC) to route hardware events to AO handlers, enabling low-latency responses; polling is used for simple devices like keyboards by checking status flags at fixed I/O ports (e.g., 0x60 for PS/2). Access relies on hardware-specific addresses, ensuring a closed environment with no open ports or dynamic connections.

Software Execution Model

In a BMC environment, software execution commences after the loads the and AO from USB, initializing the x86 (PC, or EIP in ) to the of the initial code at 0x7C00, then jumping to the main AO at 0x00111000 in non-volatile USB storage. Without an OS, the CPU performs the fetch-decode-execute cycle directly: fetching instructions from physical memory using the PC, decoding operations, executing via register/memory manipulation, and updating the PC, repeating in a single-threaded manner unless the AO implements internal concurrency. This ensures deterministic execution focused on one AO at a time. Developers implement OS-like services manually within the AO, such as timers via hardware timers (e.g., PIT or HPET on x86) configured through port I/O for interrupts, error handling by checking CPU flags (e.g., for exceptions like divide-by-zero) and invoking recovery routines, and limited multi-tasking using event queues or with atomic operations like LOCK prefixes for across threads within the suite. No preemptive scheduling occurs; concurrency relies on cooperative yields or hardware interrupts. BMC programs are developed in C/C++ with inline NASM assembly for hardware access, producing statically linked monoliths without standard libraries, system calls, or runtimes, compiled via tools like GCC for bare x86 targets. This self-contained design minimizes footprint (typically under 2 MB) and dependencies, facilitating direct hardware . The lifecycle of a BMC AO begins with USB and minimal initialization, proceeds to execution in an event-driven loop handling I/O and tasks, and ends with a HLT instruction or controlled shutdown, returning the system to a bare state. Resilience is enhanced by integrated mechanisms like watchdog timers via hardware resets, providing full oversight without external aids.

Advantages and Limitations

Primary Advantages

Bare machine offers enhanced by eliminating the operating and its associated vulnerabilities, which account for approximately 40% of root causes in cyberattacks. This paradigm inherently mitigates 20 out of 22 common threats, including buffer overflows, , infections, and , through the absence of exploitable layers such as calls, dynamic libraries, and open ports. Applications operate in a closed environment with authenticated access only to verified sites, further reducing attack surfaces. Performance benefits arise from direct hardware access without OS overhead, enabling efficient resource utilization and high throughput for single-application execution. The monolithic structure results in smaller code footprints, typically under 2 MB, which contributes to lower and prolonged hardware longevity by avoiding dependencies on evolving OS versions. Simplicity is a core advantage, as developers focus on essential functionality without managing OS abstractions or middleware. This leads to reduced development complexity for domain-specific application suites, such as web servers or VoIP systems, and eliminates licensing or maintenance costs tied to operating systems.

Key Limitations

Development in bare machine computing requires specialized knowledge of hardware architecture, including and interrupt handling, as there are no OS-provided abstractions or standard libraries. Programmers must implement custom drivers and interfaces from scratch, increasing the risk of errors and the need for thorough testing without built-in support. Scalability is constrained by the single-application execution model and domain-specific focus, limiting support for multitasking or general-purpose . Incorporating advanced features like networking requires custom development, and the lack of third-party software or modular frameworks can complicate expansion beyond simple, targeted applications. Portability is restricted primarily to Intel x86/x64 architectures, with code tightly coupled to specific hardware peripherals and interfaces. While generic interfaces aid compatibility within supported platforms, adaptations for other architectures or networking (e.g., no support) necessitate significant rewrites. demands careful measures, such as protecting bootable USB media, to prevent unauthorized access or tampering. Although static executables reduce the need for frequent updates, any modifications require revalidation of the entire application to ensure stability, and the absence of standardized tools can prolong support efforts.

Applications and Examples

Early Computer Systems

The , completed in 1945, exemplified early bare machine execution through its wired-program architecture, designed specifically for computing artillery firing tables for the Army's [Ballistic Research Laboratory](/page/Ballistic Research Laboratory). Lacking stored-program capability, it required manual reconfiguration via patch cables and switches for each new computation, a process that could take days and involved direct hardware intervention by operators. Its first operational program, executed in December 1945, performed ballistic trajectory calculations that would have otherwise required a year of manual effort by 100 personnel, highlighting the machine's raw computational power without software abstraction layers. Operators controlled execution directly from a console, monitoring and adjusting accumulators and function tables in real time, with no intermediate operating system to manage resources. The , operational from May 1949 at the , marked a pivotal advancement as the first practical stored-program bare machine, enabling direct execution of user code loaded into its memory. Its memory consisted of mercury delay lines—tubes filled with mercury that stored data as acoustic pulses traveling at the —providing 512 17-bit words initially, expandable to 1024. Programs were prepared offline on paper tape using a custom subroutine library and loaded via a photoelectric tape reader at 50 characters per second, after which the initial orders routine transferred the code directly into delay line storage for immediate execution without an overlying OS. On its debut, EDSAC ran a program to compute and print squares of integers from 0 to 100, followed by a list, demonstrating bare machine operation under console oversight by engineers like , who manually initiated runs and cleared memory between jobs. The IBM 701, introduced in 1952 as the company's first commercial scientific computer and initially dubbed the Defense Calculator, relied on bare assembly programming for high-precision simulations in defense and research applications. Users wrote code in a symbolic assembly language, assembled offline into machine instructions punched on cards or magnetic tape, which were then loaded into the electrostatic storage drum via dedicated readers—typically the IBM 726 tape unit at 100 bits per inch or the IBM 711 card reader at 150 cards per minute. Once loaded, programs executed directly on the hardware, with operators using the console's switches and indicator lights for manual intervention, such as halting execution, inspecting registers, or initiating tape rewinds, all without software-mediated control. This setup supported tasks like Los Alamos nuclear simulations, where the 701's 4096-word core memory and vacuum-tube arithmetic units processed floating-point operations at speeds up to 16,000 additions per second, underscoring its role in unadorned hardware computation.

Embedded and Real-Time Systems

In embedded systems, bare machine execution plays a pivotal role in microcontrollers such as PIC and platforms, particularly 8-bit models introduced since the 1970s, where operates directly on hardware to manage sensor control tasks. These microcontrollers, like the PIC16 series from Microchip, enable developers to write bare-metal code that interfaces directly with peripherals for precise from sensors, avoiding the overhead of an operating to ensure efficient resource utilization in resource-constrained environments. For instance, in applications involving environmental monitoring or industrial automation, bare-metal programming on Arduino's AVR-based 8-bit chips allows for direct register manipulation to handle analog-to-digital conversions and interrupt-driven sensor polling, providing deterministic responses essential for real-time data processing. In real-time applications, bare machine code is extensively used in automotive electronic control units (ECUs) for engine management, a practice dating back to the when microprocessor-based systems began integrating and ignition control. These ECUs, such as those in vehicles from manufacturers like and Ford, run interrupt-driven bare-metal on microcontrollers like the MC9S12XEP768 to achieve microsecond-level timing precision for critical operations, including spark timing and throttle response, without OS-induced latency that could compromise safety. systems further exemplify bare machine applications in , where is paramount, often using direct hardware control for rapid fault detection and recovery in flight-critical functions. Techniques like static binary sanitization enhance this by instrumenting to make memory faults observable, thereby improving overall system resilience without relying on higher-level abstractions. Implementation in these embedded contexts typically involves bootloaders that initialize hardware before transitioning to the bare-metal application , ensuring a clean handoff for sustained operation. This process includes verifying the application's and , de-initializing peripherals to a reset state, remapping the vector table, and jumping to the application's via assembly instructions to set the stack pointer and . Such transitions maintain hardware consistency, particularly for write-once registers like watchdogs, enabling reliable bare machine runtime in sensor-driven or control-oriented devices.

Modern Specialized Uses

In modern (IoT) deployments, bare-metal on chips like the enables highly optimized, low-power networking applications by allowing direct hardware control without an operating system overhead. The , introduced in 2016 by Espressif Systems, supports bare-metal programming modes that facilitate custom for energy-efficient tasks such as wireless sensor networks and edge connectivity, where power consumption must be minimized to extend battery life in remote devices. In space and defense applications, radiation-hardened components are critical in satellites and spacecraft, where they provide reliable control in harsh radiation environments. NASA's Artemis program, initiated in the 2020s, incorporates over 300 radiation-hardened integrated circuits (ICs) from Renesas (Intersil-brand) across battery management, engine controls, and abort systems on the Orion spacecraft, supporting deterministic operation and fault tolerance during lunar missions. These systems ensure single-event effect mitigation, enabling extended operations in deep space. Demonstrated applications of bare machine computing include web servers, VoIP soft-phones, and chat systems running directly on bare PCs, as explored in up to , validating resilience in high-security contexts.

References

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