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[wasm] Automate patching the emsdk installation to add controlled ind… #75532

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merged 1 commit into from
Sep 13, 2022
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[wasm] Automate patching the emsdk installation to add controlled ind… #75532

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10 changes: 3 additions & 7 deletions docs/workflow/debugging/mono/wasm-debugging.md
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Original file line number Diff line number Diff line change
Expand Up @@ -83,14 +83,10 @@ and change the
This will hopefully cause the failure to happen reliably.

There is another random number generator in `upstream/emscripten/src/deterministic.js`
which needs the same treatment:
```
var randomBuffer3 = new Uint8Array(2);
crypto.getRandomValues(randomBuffer3);
which needs the same treatment.

var MAGIC = (randomBuffer3 [0] << 8) | randomBuffer3 [1];
console.log ("SEED2: " + MAGIC);
```
Running `make patch-deterministic` in `src/mono/wasm` will patch the
emscripten installation in `src/mono/wasm/emsdk` with these changes.

# Debugging signature mismatch errors

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3 changes: 3 additions & 0 deletions src/mono/wasm/Makefile
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Expand Up @@ -140,3 +140,6 @@ build-dbg-proxy:
$(DOTNET) build $(TOP)/src/mono/wasm/debugger/BrowserDebugHost $(MSBUILD_ARGS)
build-dbg-testsuite:
$(DOTNET) build $(TOP)/src/mono/wasm/debugger/DebuggerTestSuite $(MSBUILD_ARGS)

patch-deterministic:
cd emsdk/upstream/emscripten/ && patch -p1 < ../../../runtime/deterministic.diff
41 changes: 41 additions & 0 deletions src/mono/wasm/runtime/deterministic.diff
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@@ -0,0 +1,41 @@
diff --git a/src/deterministic.js b/src/deterministic.js
index 0b894b4ac..05f50abba 100644
--- a/src/deterministic.js
+++ b/src/deterministic.js
@@ -4,7 +4,13 @@
* SPDX-License-Identifier: MIT
*/

-var MAGIC = 0;
+var randomBuffer3 = new Uint8Array(2);
+crypto.getRandomValues(randomBuffer3);
+
+var MAGIC = (randomBuffer3 [0] << 8) | randomBuffer3 [1];
+console.log ("SEED2: " + MAGIC);
+
+//var MAGIC = 0;
Math.random = () => {
MAGIC = Math.pow(MAGIC + 1.8912, 3) % 1;
return MAGIC;
diff --git a/src/library.js b/src/library.js
index 603f94dbf..698e9fe29 100644
--- a/src/library.js
+++ b/src/library.js
@@ -2196,6 +2196,17 @@ mergeInto(LibraryManager.library, {
// TODO: consider allowing the API to get a parameter for the number of
// bytes.
$getRandomDevice: function() {
+ var randomBuffer2 = new Uint8Array(2);
+ crypto.getRandomValues(randomBuffer2);
+
+ if (FS.seed2 == null)
+ FS.seed2 = (randomBuffer2 [0] << 8) | randomBuffer2 [1];
+ console.log('SEED: ' + FS.seed2);
+ return function() {
+ FS.seed2 = FS.seed2 * 16807 % 2147483647;
+ return FS.seed2;
+ };
+
if (typeof crypto == 'object' && typeof crypto['getRandomValues'] == 'function') {
// for modern web browsers
var randomBuffer = new Uint8Array(1);