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velzie
b3621e0204
A program that patches its own code with mprotect(RWX) around each write (an old MinGW runtime's pseudo-relocations: one per relocation, the whole .text each time) retired the whole section per patch, the relocator's own code with it, which then came back to translation once per patch: a process that does this for thousands of relocations crawled through startup for minutes. The kernel now notes which retired ranges were retired by being made writable while staying executable (MapLog::writable_code). On x86, the browser host keeps the pages of those ranges whose translations were all made while the page was writable and executable (volatile, so each block checks its bytes against a snapshot) and that hold no unit code; every other page is retired as before. The native host keeps no translation of writable code and retires them all. The diagnostic retire counts now count only pages retired. test/native/textpatch: 300 patches of one function from code on the next page of its section; the last patch is seen natively and on the page, warm and cold, and the patching code does not come to translation again for each patch. Co-Authored-By: Claude Opus 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_e0aa53aa95eb4b86910519b4d14812a5 (cherry picked from commit 030864228b7a57299ada7408dac377148320c774)
38 lines
2.1 KiB
JavaScript
38 lines
2.1 KiB
JavaScript
// A program that patches its own code one write at a time, its section made
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// writable and executable around each write and the code doing it in that
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// section (fixtures/native/textpatch: an old MinGW runtime's pseudo-
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// relocations): the patched function's last patch is seen, natively and on
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// the page; and on the page the code doing the patching is not translated
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// again for each patch (translations made while its page was writable and
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// executable check their bytes, and are kept when it is made so again),
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// which said "came to translation 64 times" and ran each patch through a
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// fresh translation of the loop.
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import { native, trim, tail } from '../lib/native.mjs';
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export const meta = { hosts: ['node'], arches: ['x86'], timeout: 600 };
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const N = 300;
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const SUM = `textpatch before 1234567 after ${N - 1}`;
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const lines = (out) => out.split('\n').filter((l) => l.startsWith('textpatch ')).join('\n');
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export default async function (t) {
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const n = native(t);
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const d = n.dir('textpatch');
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await n.cc(['-O1', '-static', '-o', `${d}/textpatch`, n.src('textpatch/textpatch.c')]);
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const r = await n.gexc(['run', `${d}/textpatch`, String(N)], { timeout: 180000 });
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if (trim(r.stdout) === 'textpatch skip') t.skip('the compiler laid getter out otherwise');
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t.eq('native: the last patch is seen', trim(r.stdout), SUM, tail(r.stderr));
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const g = n.g;
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for (const p of ['gex_browser.x86.shared.wasm', 'gex_kernel.x86.wasm']) g.pub(p);
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// Warm: `getter` and the loop translated before the first patch; cold:
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// only the loop.
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for (const how of ['warm', 'cold']) {
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const p = await g.run(n.seed(), `${d}/textpatch`, how === 'cold' ? [String(N), 'cold'] : [String(N)], { files: { '/g/textpatch': `${d}/textpatch` }, argv0: '/g/textpatch', env: { GEX_SHARED: '1' }, timeout: 300000 });
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t.eq(`page, ${how}: the last patch is seen`, lines(p.stdout), SUM, tail(p.stderr));
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t.check(`page, ${how}: the patching code is not translated again a patch`, !/came to translation \d+ times|retired \d+ times|LIVELOCK/.test(p.stdout + p.stderr), tail(p.stderr));
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}
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n.clean();
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}
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