WebAssembly: limit slow memories

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[JF Bastien]

Bug #170628 limits the number of fast memories, partly because ASLR.

The code then falls back to slow memories. It first tries to virtually allocated any declared maximum (and in there, physically the initial), and if that fails it tries to physically allocate the initial without any extra.

This can still be used to cause a bunch of virtual allocation. We should probably impose a soft limit on slow memories as well. I think that limit should be against whole-process sum of virtually allocated slow memory (don't forget to include calls to grow!).

I'm not sure what the number should be, but I'll guess something around what the maximum for fast memory virtual allocation is.

Anything exceeding that limit would cause allocation/grow to fail.

[JF Bastien]

Created attachment 307473 [details]
patch

[Saam Barati]

Comment on attachment 307473 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=307473&action=review

r=me. I'd like to at least see a test we run on Mac, and if it's flaky, we can consider what to do next. But let's land it before assuming it'll be flaky.

> Source/JavaScriptCore/ChangeLog:21
> +        I haven't added a test because the bots will likely be unhappy /

What about at least making it run on Mac?

> Source/JavaScriptCore/wasm/WasmMemory.cpp:203
> +    size_t maximum = fastMemoryAllocationSoftLimit * Memory::fastMappedBytes();

I would really add a new variable for this, even if initially it's the same value. That way we can change them independent of one another.

[JF Bastien]

Created attachment 307488 [details]
patch

Add test and factor out function as suggested.

[WebKit Commit Bot]

Comment on attachment 307488 [details]
patch

Rejecting attachment 307488 [details] from commit-queue.

Failed to run "['/Volumes/Data/EWS/WebKit/Tools/Scripts/webkit-patch', '--status-host=webkit-queues.webkit.org', '--bot-id=webkit-cq-03', 'apply-attachment', '--no-update', '--non-interactive', 307488, '--port=mac']" exit_code: 2 cwd: /Volumes/Data/EWS/WebKit

Last 500 characters of output:
 succeeded at 1 with fuzz 3.
patching file JSTests/wasm.yaml
Hunk #1 FAILED at 1.
Hunk #2 succeeded at 31 (offset 2 lines).
1 out of 2 hunks FAILED -- saving rejects to file JSTests/wasm.yaml.rej
patching file JSTests/wasm/stress/oom.js
patching file Source/JavaScriptCore/ChangeLog
Hunk #1 succeeded at 1 with fuzz 3.
patching file Source/JavaScriptCore/wasm/WasmMemory.cpp

Failed to run "[u'/Volumes/Data/EWS/WebKit/Tools/Scripts/svn-apply', '--force']" exit_code: 1 cwd: /Volumes/Data/EWS/WebKit

Full output: http://webkit-queues.webkit.org/results/3564516

[JF Bastien]

Created attachment 307489 [details]
patch

Rebase. I self-merge-conflicted.

[WebKit Commit Bot]

The commit-queue encountered the following flaky tests while processing attachment 307489 [details]:

The commit-queue is continuing to process your patch.

[WebKit Commit Bot]

The commit-queue encountered the following flaky tests while processing attachment 307489 [details]:

media/modern-media-controls/macos-fullscreen-media-controls/macos-fullscreen-media-controls-buttons-styles.html bug 168317 (author: [e-mail])
The commit-queue is continuing to process your patch.

[WebKit Commit Bot]

Comment on attachment 307489 [details]
patch

Clearing flags on attachment: 307489

Committed r215525: <http://trac.webkit.org/changeset/215525>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.