Struct TLBShootdownSource 

pub struct TLBShootdownSource {
    pub config: TLBShootdownConfig,
}

Harvests timing jitter from TLB invalidation broadcasts via mprotect().

What it measures

Nanosecond timing of mprotect() permission toggles (read-write → read-only → read-write) on varying numbers of pages within a pre-allocated memory region.

Why it’s entropic

When mprotect() changes page protection on a multi-core system, the kernel must invalidate stale TLB entries on ALL cores:

• Inter-Processor Interrupt (IPI) — the kernel sends an IPI to every core that might have cached TLB entries for the affected pages
• TLB flush latency — each receiving core must drain its pipeline, flush matching TLB entries, and acknowledge
• Cross-cluster latency — Apple Silicon has separate P-core and E-core clusters with different interconnect latencies
• Concurrent IPI traffic — other processes’ mprotect()/munmap() calls create IPI storms that interfere with our measurements

What makes it unique

TLB shootdowns are a microarchitectural side-channel that has been studied for attacks but never harvested as an entropy source. The IPI broadcast mechanism creates system-wide nondeterminism that depends on the state of EVERY core simultaneously.

Configuration

See TLBShootdownConfig for tunable parameters. Key options:

• measure_variance: delta-of-deltas extraction (recommended: true)
• page_count_range: controls IPI storm intensity
• region_pages: controls physical page diversity

Fields

config: TLBShootdownConfig

Source configuration. Use Default::default() for recommended settings.

Trait Implementations

impl Default for TLBShootdownSource

fn default() -> TLBShootdownSource

Returns the “default value” for a type.

impl EntropySource for TLBShootdownSource

fn info(&self) -> &SourceInfo

Source metadata.

fn is_available(&self) -> bool

Check if this source can operate on the current machine.

fn collect(&self, n_samples: usize) -> Vec<u8>

Collect raw entropy samples. Returns a Vec<u8> of up to n_samples bytes.

fn name(&self) -> &'static str

Convenience: name from info.