src: enable V8's WASM trap handlers #27246

devsnek · 2019-04-15T21:12:27Z

This uses SIGSEGV handlers to catch WASM out of bound (OOB) memory
accesses instead of inserting OOB checks inline, resulting in a 25%-30%
speed increase.

Note that installing a custom SIGSEGV handler will break this, resulting
in potentially scary behaviour. Users should use node::RegisterSignalHandler instead.

Refs: #14927

Closes #14927

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
commit message follows commit guidelines

nodejs-github-bot · 2019-04-15T21:12:29Z

Lite-CI: https://ci.nodejs.org/job/node-test-pull-request-lite-pipeline/3265

addaleax · 2019-04-15T21:20:06Z

My gut feeling would be that @ofrobots’s comment in #14927 (comment) is a good approach – using our own signal handler, and providing a public C++ API for forwarding that to addons/embedders? That would mean that those would not have to carry the responsibility of integrating with V8’s APIs.

I’d say this is semver-major because of the conflicts with existing published versions of segfault-handler – do you agree? If yes, then I’m happy with any approach, because we should have more than enough time to update that package.

devsnek · 2019-04-15T21:26:10Z

@addaleax we already have node::RegisterSignalHandler, i guess i could set this up with that, although i think this then becomes uh... not platform independent.

we'll need to add a bunch of platform specific switches for calling TryWasmTrapHanderPosix vs TryWasmTrapHandlerWin but if that complexity is okay then we can go for it.

devsnek · 2019-04-15T22:03:42Z

@addaleax set up to use RegisterSignalHandler, unfortunately we only have that for posix atm, so maybe we can expand to win in the future? (although i don't think people on windows are expecting great performance anyway 🤷‍♂️)

addaleax · 2019-04-15T22:54:24Z

@devsnek Yeah, we’d need to find some common API (or expose 2 variants) for both Windows and POSIX; and maybe find some API constraints, e.g. what happens if it is called multiple times, is the registering function threadsafe, etc. and document that

src/node.cc

joyeecheung · 2019-04-16T06:14:36Z

src/node.cc

@@ -452,9 +456,24 @@ void LoadEnvironment(Environment* env) {


 #ifdef __POSIX__
+
+struct sigaction previous_sigsegv_action;


Can you put this into the per_process namespace and make it static?

src/node.cc

bnoordhuis · 2019-04-16T09:07:06Z

Sorry, I forgot to mention something important: you must re-raise the SIGSEGV when V8 doesn't handle it and there's no other handler for it.

bnoordhuis · 2019-04-30T07:20:28Z

src/node.cc

+    } else {
+      uv_tty_reset_mode();
+#ifdef __FreeBSD__
+      // FreeBSD has a nasty bug, see RegisterSignalHandler for details


Not a blocker, just an observation, but I expect that's no longer relevant for the freebsd versions we support.

@nodejs/platform-freebsd can anyone confirm or deny?

@bnoordhuis do you know if there's any more background/detail on the issue?

@kostikbel any insight? The referenced comment is:

// FreeBSD has a nasty bug with SA_RESETHAND reseting the SA_SIGINFO, that is // in turn set for a libthr wrapper. This leads to a crash. // Work around the issue by manually setting SIG_DFL in the signal handler

From my copy of POSIX 1003.1-2017 AKA SUSv7:

SA_RESETHAND If set, the disposition of the signal shall be reset to SIG_DFL and the SA_SIGINFO flag shall be cleared on entry to the signal handler.

And we do exactly that. Am I reading right that this behavior causes some troubles, when combined with libthr ? Can you give a minimal example ?

@emaste @kostikbel The bug report is nodejs/node-v0.x-archive#9326, triage starts in nodejs/node-v0.x-archive#9326 (comment).

I'm reasonably sure that bug was fixed in fbsd 11 but you probably know for sure, @kostikbel, since you authored the fix.

Ok, so should this comment (and possibly some code) removed ? Since I believe all supported FreeBSD versions have the SA_RESETHAND | SA_SIGINFO fix.

That sounds about right (removing code & comment.) I've opened #27515 to track it.

src/node.cc

devsnek · 2019-04-30T13:42:13Z

@bnoordhuis do you know why this compiles fine on macos but has issues finding those atomic symbols on the linux build?

bnoordhuis · 2019-05-01T04:56:35Z

Reproducing here because scrolling trough Travis really is quite horrid:

/home/travis/build/nodejs/node/out/Release/obj.target/libnode/src/node.o: In function `node::TrapWebAssemblyOrContinue(int, siginfo_t*, void*) [clone .part.36]':
node.cc:(.text+0xce): undefined reference to `__atomic_load'
/home/travis/build/nodejs/node/out/Release/obj.target/libnode/src/node.o: In function `node::RegisterSignalHandler(int, void (*)(int, siginfo_t*, void*), bool, sigaction*)':
node.cc:(.text+0x2484): undefined reference to `__atomic_exchange'
collect2: error: ld returned 1 exit status
cctest.target.mk:226: recipe for target '/home/travis/build/nodejs/node/out/Release/cctest' failed
make[1]: *** [/home/travis/build/nodejs/node/out/Release/cctest] Error 1
make[1]: *** Waiting for unfinished jobs....
/home/travis/build/nodejs/node/out/Release/obj.target/libnode/src/node.o: In function `node::TrapWebAssemblyOrContinue(int, siginfo_t*, void*) [clone .part.36]':
node.cc:(.text+0xce): undefined reference to `__atomic_load'
/home/travis/build/nodejs/node/out/Release/obj.target/libnode/src/node.o: In function `node::RegisterSignalHandler(int, void (*)(int, siginfo_t*, void*), bool, sigaction*)':
node.cc:(.text+0x2484): undefined reference to `__atomic_exchange'
collect2: error: ld returned 1 exit status

I'm going to guess that gcc doesn't know how to lower the __atomic_load and __atomic_exchange builtins for compound types (i.e., struct sigaction) and just re-emits them as library calls.

If you switch to function pointers, the problem should hopefully go away.

richardlau · 2019-05-01T07:52:19Z

Or maybe link to libatomic? https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65756#c1

nodejs-github-bot · 2019-05-16T16:19:36Z

CI: https://ci.nodejs.org/job/node-test-pull-request/23146/

This uses SIGSEGV handlers to catch WASM out of bound (OOB) memory accesses instead of inserting OOB checks inline, resulting in a 25%-30% speed increase. Note that installing a custom SIGSEGV handler will break this, resulting in potentially scary behaviour. Refs: nodejs#14927 PR-URL: nodejs#27246 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net>

devsnek · 2019-05-16T17:34:46Z

landed in 70c7686

This uses SIGSEGV handlers to catch WASM out of bound (OOB) memory accesses instead of inserting OOB checks inline, resulting in a 25%-30% speed increase. Note that installing a custom SIGSEGV handler will break this, resulting in potentially scary behaviour. Refs: nodejs#14927 PR-URL: nodejs#27246 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com> Reviewed-By: Anna Henningsen <anna@addaleax.net>

This workaround should no longer be necessary with supported versions of FreeSBD. Originall introduced in commit b64983d ("src: reset signal handler to SIG_DFL on FreeBSD") from March 2015. Fixes: nodejs#27515 Refs: nodejs#27246 (comment)

BridgeAR · 2019-05-21T09:43:57Z

@devsnek @addaleax is there a way to backport this PR with a compatibility patch to remove the breaking change? It would already be helpful if e.g. 50% of the code would be backported.

addaleax · 2019-05-21T10:52:52Z

@BridgeAR I guess it would be possible to backport this in a non-breaking manner, but it should not be released without #27775 as well

BridgeAR · 2019-05-21T11:00:31Z

@addaleax sounds good 👍. Would you be willing to open the backport after #27775 landed?

This workaround should no longer be necessary with supported versions of FreeSBD. Originally introduced in commit b64983d ("src: reset signal handler to SIG_DFL on FreeBSD") from March 2015. Fixes: nodejs#27515 Refs: nodejs#27246 (comment) Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

This workaround should no longer be necessary with supported versions of FreeSBD. Originally introduced in commit b64983d ("src: reset signal handler to SIG_DFL on FreeBSD") from March 2015. Fixes: nodejs#27515 PR-URL: nodejs#27780 Refs: nodejs#27246 (comment) Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

This macro is only defined when building Node.js, so addons cannot use it as a way of detecting feature availability. PR-URL: #27775 Refs: #27246 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

Without this, we would re-enter the signal handler immediately after re-raising the signal, leading to an infinite loop. PR-URL: #27775 Refs: #27246 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

This is not easily implementable, and should be explicitly disallowed. PR-URL: #27775 Refs: #27246 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

Ensure coverage for the different combinations of arguments. PR-URL: #27775 Refs: #27246 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

devsnek · 2019-09-09T17:37:35Z

Notable change:

This speeds up memory operations for WASM by around 25-30%. However, native code must now install the SIGSEGV signal handlers using node::RegisterSignalHandler.

Notable changes: - **assert**: - do not repeat .throws() code (Ruben Bridgewater) [#28263](#28263) - wrap validation function errors (Ruben Bridgewater) [#28263](#28263) - fix generatedMessage property (Ruben Bridgewater) [#28263](#28263) - improve class instance errors (Ruben Bridgewater) [#28263](#28263) - **benchmark**: - use test/common/tmpdir consistently (João Reis) [#28858](#28858) - **build**: - make full-icu the default for releases (Richard Lau) [#29887](#29887) - update minimum Xcode version for macOS (Michael Dawson) [#29622](#29622) - **child_process**: - runtime deprecate \_channel (cjihrig) [#27949](#27949) - simplify spawn argument parsing (cjihrig) [#27854](#27854) - **console**: - display timeEnd with suitable time unit (Xavier Stouder) [#29251](#29251) - **deps**: - patch V8 to 7.8.279.14 (Myles Borins) [#29694](#29694) - patch V8 to 7.8.279.12 (Myles Borins) [#29694](#29694) - patch V8 to 7.8.279.10 (Myles Borins) [#29694](#29694) - update V8's postmortem script (cjihrig) [#29694](#29694) - V8: cherry-pick 716875d (Myles Borins) [#29694](#29694) - update V8 to 7.8.279.9 (Myles Borins) [#29694](#29694) - V8: cherry-pick b33af60 (Michaël Zasso) [#28016](#28016) - update V8 to 7.6.303.28 (Michaël Zasso) [#28016](#28016) - **domain**: - error handler runs outside of its domain (Julien Gilli) [#26211](#26211) - **fs**: - make FSWatcher.start private (Lucas Holmquist) [#29905](#29905) - add runtime deprecate for file stream open() (Robert Nagy) [#29061](#29061) - allow int64 offset in fs.write/writeSync/fd.write (Zach Bjornson) [#26572](#26572) - use IsSafeJsInt instead of IsNumber for ftruncate (Zach Bjornson) [#26572](#26572) - allow int64 offset in fs.read/readSync/fd.read (Zach Bjornson) [#26572](#26572) - close file descriptor of promisified truncate (João Reis) [#28858](#28858) - **http**: - do not emit end after aborted (Robert Nagy) [#27984](#27984) - don't emit 'data' after 'error' (Robert Nagy) [#28711](#28711) - remove legacy parser (Anna Henningsen) [#29589](#29589) - throw if 'host' agent header is not a string value (Giorgos Ntemiris) [#29568](#29568) - replace superfluous connection property with getter/setter (Robert Nagy) [#29015](#29015) - fix test where aborted should not be emitted (Robert Nagy) [#20077](#20077) - remove default 'timeout' listener on upgrade (Luigi Pinca) [#26030](#26030) - **http, http2**: - remove default server timeout (Ali Ijaz Sheikh) [#27558](#27558) - **http2**: - remove security revert flags (Anna Henningsen) [#29141](#29141) - remove callback-based padding (Anna Henningsen) [#29144](#29144) - **lib**: - rename validateInteger to validateSafeInteger (Zach Bjornson) [#26572](#26572) - correct error.errno to always be numeric (Joyee Cheung) [#28140](#28140) - no need to strip BOM or shebang for scripts (Refael Ackermann) [#27375](#27375) - rework logic of stripping BOM+Shebang from commonjs (Gus Caplan) [#27768](#27768) - **module**: - runtime deprecate createRequireFromPath() (cjihrig) [#27951](#27951) - **readline**: - error on falsy values for callback (Sam Roberts) [#28109](#28109) - **repl**: - close file descriptor of history file (João Reis) [#28858](#28858) - **src**: - bring 425 status code name into accordance with RFC 8470 (Sergei Osipov) [#29880](#29880) - update NODE\_MODULE\_VERSION to 79 (Myles Borins) [#29694](#29694) - update NODE\_MODULE\_VERSION to 78 (Michaël Zasso) [#28918](#28918) - add error codes to errors thrown in C++ (Yaniv Friedensohn) [#27700](#27700) - use non-deprecated overload of V8::SetFlagsFromString (Michaël Zasso) [#28016](#28016) - update NODE\_MODULE\_VERSION to 77 (Michaël Zasso) [#28016](#28016) - update NODE\_MODULE\_VERSION to 74 (Refael Ackermann) [#27375](#27375) - make process.env.TZ setter clear tz cache (Ben Noordhuis) [#20026](#20026) - enable V8's WASM trap handlers (Gus Caplan) [#27246](#27246) - **stream**: - throw unhandled error for readable with autoDestroy (Robert Nagy) [#29806](#29806) - always invoke callback before emitting error (Robert Nagy) [#29293](#29293) - invoke callback before emitting error always (Robert Nagy) [#29293](#29293) - do not flush destroyed writable (Robert Nagy) [#29028](#29028) - don't emit finish on error (Robert Nagy) [#28979](#28979) - disallow stream methods on finished stream (Robert Nagy) [#28687](#28687) - do not emit after 'error' (Robert Nagy) [#28708](#28708) - fix destroy() behavior (Robert Nagy) [#29058](#29058) - simplify `.pipe()` and `.unpipe()` in Readable (Weijia Wang) [#28583](#28583) - **tools**: - patch V8 to run on older XCode versions (Ujjwal Sharma) [#29694](#29694) - update V8 gypfiles (Michaël Zasso) [#29694](#29694) - support full-icu by default (Steven R. Loomis) [#29522](#29522) - **util**: validate formatWithOptions inspectOptions (Ruben Bridgewater) [#29824](#29824) PR-URL: #29504

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addaleax mentioned this pull request May 20, 2019

src: fix segfault handling/RegisterSignalHandler #27775

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src: remove freebsd SA_RESETHAND workaround #27780

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test: skip test-worker-prof on all platforms. #28175

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2019-10-22, Version 13.0.0 (Current) #29504

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src: enable V8's WASM trap handlers #27246

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		@@ -452,9 +456,24 @@ void LoadEnvironment(Environment* env) {


		#ifdef __POSIX__

		struct sigaction previous_sigsegv_action;

src: enable V8's WASM trap handlers #27246

src: enable V8's WASM trap handlers #27246

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