flip-link adds zero-cost stack overflow protection to your embedded programs. The problem Bare metal Rust programs may not be memory safe in presence of stack overflows. For example, this is the case for Rust programs based on v0.6.x of the cortex-m-rt crate. The following program, which contains no unsafe code block, can run into undefined behavior if it reaches a stack overflow condition. // static variables placed in the .bss / .data sections static FLAG1: AtomicBool = AtomicU32::new(false); // .bss static FLAG2: AtomicBool = AtomicU32::new(true); // .data fn main() { let _x = fib(100); } #[inline(never)] fn fib(n: u32) -> u32 { // allocate and initialize 4 kilobytes of stack memory let _use_stack = [0xAA; 1024]; if n < 2 { 1 } else { fib(n - 1) + fib(n - 2) // recursion } } #[interrupt] fn interrupt_handler() { // does some operation with `FLAG1` and `FLAG2` } The function call stack, also known as the "stack", grows downwards on function calls and when local variables (e.g. let x) are created (these variables are also placed on the stack). If the stack grows too large it collides with the .bss + .data region, which contains all the program's static variables. The collision results in the static variables being overwritten with unrelated data. This can result in the program observing the static variables in an invalid state: for example an AtomicBool may hold the value 3 -- this is undefined behavior because the Rust ABI expects this single-byte variable to be either 0 or 1. The solution One potential solution is to change the memory layout of the program and place the stack below the .bss+.data region. With this flipped memory layout the stack cannot collide with the static variables. Instead it will collide with the boundary of the physical RAM memory region. In the ARM Cortex-M architecture, trying to read or write past the boundaries of the RAM region produces a "hardware exception". The cortex-m-rt crate provides an API to handle this condition: a HardFault exception handler can be defined; this "handler" (function) will be executed when the invalid memory operation is attempted. flip-link implements this stack overflow solution. Linking your program with flip-link produces the flipped memory layout, which is memory safe in presence of stack overflows. Architecture support flip-link is known to work with ARM Cortex-M programs that link to version 0.6.x of the cortex-m-rt crate and are linked using the linker shipped with the Rust toolchain (LLD). At this time, it hasn't been tested with other architectures or runtime crates.
Binary packages can be installed with the high-level tool pkgin (which can be installed with pkg_add) or pkg_add(1) (installed by default). The NetBSD packages collection is also designed to permit easy installation from source.
The pkg_admin audit command locates any installed package which has been mentioned in security advisories as having vulnerabilities.
Please note the vulnerabilities database might not be fully accurate, and not every bug is exploitable with every configuration.
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