commit d8e416b049070463033e5564ee2b3f88cead8a69
parent 9113a280893f9493a01519d7af1510dbc4a36f62
Author: Jared Tobin <jared@jtobin.io>
Date: Wed, 21 Oct 2026 08:44:55 +0400
checks: a probe harness under both instruments, on Linux
etc/probe/harness.c takes its secret in hex and lets it reach a loop's
bound and a table index, beside a constant-time select that reaches
neither. nix/probe.nix builds it, runs it under traceOf and diffOf,
and holds each report's (class, function) pairs in the harness to the
expected ones exactly: a site or origin missing, or one more, fails
the check. The flake exposes it as checks.<system>.probe on Linux,
where both instruments run.
Diffstat:
3 files changed, 110 insertions(+), 1 deletion(-)
diff --git a/etc/probe/harness.c b/etc/probe/harness.c
@@ -0,0 +1,45 @@
+/*
+ * harness.c: the harness the flake's probe check runs under both
+ * instruments.
+ *
+ * Copyright (c) 2026 Jared Tobin
+ * License: MIT
+ *
+ * Its secret, the first argument in hex (of one width for every
+ * secret, so that runs lay out alike), reaches a loop's bound and a
+ * table index; a constant-time select reaches neither.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "vestigia.h"
+
+static unsigned char table[256];
+
+__attribute__((noinline)) unsigned branchy(unsigned s) {
+ unsigned r = 0;
+ for (unsigned i = 0; i < (s & 7); i++) r += i;
+ return r;
+}
+
+__attribute__((noinline)) unsigned lookup(unsigned s) {
+ return table[s & 0xff];
+}
+
+__attribute__((noinline)) unsigned ct(unsigned s, unsigned p) {
+ unsigned m = 0u - (p & 1u);
+ return (s & m) | (~s & ~m);
+}
+
+int main(int argc, char **argv) {
+ unsigned s = (unsigned)strtoul(argc > 1 ? argv[1] : "0", NULL, 16);
+ unsigned out[3];
+ for (int i = 0; i < 256; i++) table[i] = (unsigned char)i;
+ vestigia_secret(&s, sizeof s);
+ out[0] = branchy(s);
+ out[1] = lookup(s);
+ out[2] = ct(s, 1);
+ vestigia_public(out, sizeof out);
+ printf("%u %u %u\n", out[0], out[1], out[2]);
+ return 0;
+}
diff --git a/flake.nix b/flake.nix
@@ -35,7 +35,13 @@
inherit (v) traceOf diffOf valgrindDev version;
};
- checks.default = hpkgs.vestigia;
+ checks = {
+ default = hpkgs.vestigia;
+ }
+ # both instruments run Linux programs
+ // lib.optionalAttrs linux {
+ probe = import ./nix/probe.nix { inherit pkgs; vestigia = v; };
+ };
devShells.default = hpkgs.shellFor {
packages = p: [ p.vestigia ];
diff --git a/nix/probe.nix b/nix/probe.nix
@@ -0,0 +1,58 @@
+# The probe check: etc/probe/harness.c under both instruments, each
+# site and origin it should show found where it should be, and
+# nothing else in the harness.
+{ pkgs, vestigia }:
+
+let
+ lib = pkgs.lib;
+
+ probe = pkgs.runCommandCC "vestigia-probe" {
+ buildInputs = [ vestigia.valgrindDev ];
+ } ''
+ mkdir -p $out/bin
+ cc -O0 -g -fPIE -pie -I${vestigia.include}/include \
+ -o $out/bin/probe ${../etc/probe/harness.c} \
+ ${vestigia.include}/include/vestigia.c
+ '';
+
+ secrets = [ "00000005" "0000003a" "000000c3" ];
+ objects = [ "/bin/probe" ];
+
+ trace = vestigia.traceOf {
+ name = "probe";
+ harness = "${probe}/bin/probe";
+ args = [ (builtins.head secrets) ];
+ inherit objects;
+ };
+
+ diff = vestigia.diffOf {
+ name = "probe";
+ harness = "${probe}/bin/probe";
+ runs = map (s: [ s ]) secrets;
+ inherit objects;
+ };
+
+ # each report's (class, function) pairs in the harness, sorted
+ expected = {
+ trace = [ [ "address" "lookup" ] [ "control" "branchy" ] ];
+ diff = [ [ "address" "lookup" ] [ "control" "branchy" ] ];
+ };
+in
+pkgs.runCommand "vestigia-probe-check" {
+ nativeBuildInputs = [ pkgs.jq ];
+} ''
+ check() {
+ got=$(jq -c "$2" "$1")
+ if [ "$got" != "$3" ]; then
+ echo "probe: $1: expected $3, got $got" >&2
+ exit 1
+ fi
+ }
+ check ${trace}/trace.json \
+ '[.sites[] | [.class, .function]] | unique' \
+ '${builtins.toJSON expected.trace}'
+ check ${diff}/diff.json \
+ '[.origins[] | [.class, .frames[0].function]] | unique' \
+ '${builtins.toJSON expected.diff}'
+ touch $out
+''
