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| 1 | +//! Sprint 28 determinism guardrails. |
| 2 | +//! |
| 3 | +//! Parallel speedups are only safe if they never perturb the final image. This |
| 4 | +//! test repeatedly links one synthetic-section-heavy executable and requires |
| 5 | +//! byte-identical output across concurrent runs. |
| 6 | + |
| 7 | +mod common; |
| 8 | + |
| 9 | +use std::collections::VecDeque; |
| 10 | +use std::fs; |
| 11 | +use std::path::{Path, PathBuf}; |
| 12 | +use std::sync::{Arc, Mutex}; |
| 13 | +use std::thread; |
| 14 | +use std::time::{SystemTime, UNIX_EPOCH}; |
| 15 | + |
| 16 | +use afs_ld::{LinkOptions, Linker, OutputKind}; |
| 17 | +use common::harness::{assemble, have_xcrun, have_xcrun_tool}; |
| 18 | + |
| 19 | +const DEFAULT_RUNS: usize = 100; |
| 20 | + |
| 21 | +#[test] |
| 22 | +fn repeated_parallel_links_are_byte_identical() { |
| 23 | + if !have_xcrun() || !have_xcrun_tool("as") { |
| 24 | + eprintln!("skipping: xcrun as unavailable"); |
| 25 | + return; |
| 26 | + } |
| 27 | + |
| 28 | + let root = unique_temp_dir("determinism").expect("create determinism temp dir"); |
| 29 | + let obj = root.join("input.o"); |
| 30 | + assemble( |
| 31 | + "\ |
| 32 | + .section __TEXT,__text,regular,pure_instructions\n\ |
| 33 | + .globl _main\n\ |
| 34 | + _main:\n\ |
| 35 | + adrp x8, _value@GOTPAGE\n\ |
| 36 | + ldr x8, [x8, _value@GOTPAGEOFF]\n\ |
| 37 | + ldr w0, [x8]\n\ |
| 38 | + ret\n\ |
| 39 | +\n\ |
| 40 | + .section __DATA,__data\n\ |
| 41 | + .globl _value\n\ |
| 42 | + .p2align 2\n\ |
| 43 | + _value:\n\ |
| 44 | + .long 7\n\ |
| 45 | + .subsections_via_symbols\n", |
| 46 | + &obj, |
| 47 | + ) |
| 48 | + .expect("assemble determinism fixture"); |
| 49 | + |
| 50 | + let baseline = link_once(&obj, &root, "baseline").expect("baseline deterministic link"); |
| 51 | + let run_count = determinism_run_count(); |
| 52 | + let jobs = determinism_jobs(run_count); |
| 53 | + let queue = Arc::new(Mutex::new((0..run_count).collect::<VecDeque<_>>())); |
| 54 | + let errors = Arc::new(Mutex::new(Vec::new())); |
| 55 | + |
| 56 | + thread::scope(|scope| { |
| 57 | + for _ in 0..jobs { |
| 58 | + let queue = Arc::clone(&queue); |
| 59 | + let errors = Arc::clone(&errors); |
| 60 | + let baseline = baseline.clone(); |
| 61 | + let root = root.clone(); |
| 62 | + let obj = obj.clone(); |
| 63 | + scope.spawn(move || loop { |
| 64 | + let Some(index) = queue |
| 65 | + .lock() |
| 66 | + .expect("determinism queue mutex poisoned") |
| 67 | + .pop_front() |
| 68 | + else { |
| 69 | + break; |
| 70 | + }; |
| 71 | + match link_once(&obj, &root, &format!("run-{index:03}")) { |
| 72 | + Ok(bytes) if bytes == baseline => {} |
| 73 | + Ok(bytes) => errors |
| 74 | + .lock() |
| 75 | + .expect("determinism errors mutex poisoned") |
| 76 | + .push(format!( |
| 77 | + "run {index} differed: baseline={} bytes, output={} bytes", |
| 78 | + baseline.len(), |
| 79 | + bytes.len() |
| 80 | + )), |
| 81 | + Err(error) => errors |
| 82 | + .lock() |
| 83 | + .expect("determinism errors mutex poisoned") |
| 84 | + .push(format!("run {index} failed: {error}")), |
| 85 | + } |
| 86 | + }); |
| 87 | + } |
| 88 | + }); |
| 89 | + |
| 90 | + let errors = errors |
| 91 | + .lock() |
| 92 | + .expect("determinism errors mutex poisoned") |
| 93 | + .clone(); |
| 94 | + assert!( |
| 95 | + errors.is_empty(), |
| 96 | + "parallel deterministic links diverged:\n{}", |
| 97 | + errors.join("\n") |
| 98 | + ); |
| 99 | + |
| 100 | + let _ = fs::remove_dir_all(root); |
| 101 | +} |
| 102 | + |
| 103 | +fn link_once(obj: &Path, root: &Path, run_name: &str) -> Result<Vec<u8>, String> { |
| 104 | + let dir = root.join(run_name); |
| 105 | + fs::create_dir_all(&dir).map_err(|e| format!("create {}: {e}", dir.display()))?; |
| 106 | + let out = dir.join("deterministic.out"); |
| 107 | + let opts = LinkOptions { |
| 108 | + inputs: vec![obj.to_path_buf()], |
| 109 | + output: Some(out.clone()), |
| 110 | + kind: OutputKind::Executable, |
| 111 | + ..LinkOptions::default() |
| 112 | + }; |
| 113 | + Linker::run(&opts).map_err(|e| format!("link {}: {e}", out.display()))?; |
| 114 | + fs::read(&out).map_err(|e| format!("read {}: {e}", out.display())) |
| 115 | +} |
| 116 | + |
| 117 | +fn determinism_run_count() -> usize { |
| 118 | + std::env::var("AFS_LD_DETERMINISM_RUNS") |
| 119 | + .ok() |
| 120 | + .and_then(|raw| raw.parse::<usize>().ok()) |
| 121 | + .filter(|runs| *runs > 0) |
| 122 | + .unwrap_or(DEFAULT_RUNS) |
| 123 | +} |
| 124 | + |
| 125 | +fn determinism_jobs(run_count: usize) -> usize { |
| 126 | + std::env::var("AFS_LD_DETERMINISM_JOBS") |
| 127 | + .ok() |
| 128 | + .and_then(|raw| raw.parse::<usize>().ok()) |
| 129 | + .filter(|jobs| *jobs > 0) |
| 130 | + .unwrap_or_else(|| { |
| 131 | + thread::available_parallelism() |
| 132 | + .map(usize::from) |
| 133 | + .unwrap_or(1) |
| 134 | + }) |
| 135 | + .min(run_count) |
| 136 | + .max(1) |
| 137 | +} |
| 138 | + |
| 139 | +fn unique_temp_dir(name: &str) -> Result<PathBuf, String> { |
| 140 | + let stamp = SystemTime::now() |
| 141 | + .duration_since(UNIX_EPOCH) |
| 142 | + .map_err(|e| format!("clock error: {e}"))? |
| 143 | + .as_nanos(); |
| 144 | + let dir = std::env::temp_dir().join(format!("afs-ld-{name}-{}-{stamp}", std::process::id())); |
| 145 | + fs::create_dir_all(&dir).map_err(|e| format!("create {}: {e}", dir.display()))?; |
| 146 | + Ok(dir) |
| 147 | +} |