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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "MMPrinter.h"
#include "Logging.h"
#include "jsapi.h"
#include "mozilla/Bootstrap.h"
#include "mozilla/ErrorResult.h"
#include "mozilla/RandomNum.h"
#include "mozilla/dom/ScriptSettings.h"
#include "mozilla/dom/ipc/StructuredCloneData.h"
#include "nsFrameMessageManager.h"
#include "nsJSUtils.h"
#include "prenv.h"
namespace mozilla::dom {
LazyLogModule MMPrinter::sMMLog("MessageManager");
// You can use
// the output of the logs into logs more friendly to reading.
/* static */
Maybe<uint64_t> MMPrinter::PrintHeader(char const* aLocation,
const nsAString& aMsg) {
NS_ConvertUTF16toUTF8 charMsg(aMsg);
/*
* The topic will be skipped if the topic name appears anywhere as a substring
* of the filter.
*
* Example:
* MOZ_LOG_MESSAGEMANAGER_SKIP="foobar|extension"
* Will match the topics 'foobar', 'foo', 'bar', and 'ten' (even though
* you may not have intended to match the latter three) and it will not match
* the topics 'extensionresult' or 'Foo'.
*/
char* mmSkipLog = PR_GetEnv("MOZ_LOG_MESSAGEMANAGER_SKIP");
if (mmSkipLog && strstr(mmSkipLog, charMsg.get())) {
return Nothing();
}
uint64_t aMsgId = RandomUint64OrDie();
MOZ_LOG(MMPrinter::sMMLog, LogLevel::Debug,
("%" PRIu64 " %s Message: %s in process type: %s", aMsgId, aLocation,
charMsg.get(), XRE_GetProcessTypeString()));
return Some(aMsgId);
}
/* static */
void MMPrinter::PrintData(uint64_t aMsgId, ipc::StructuredCloneData* aData) {
if (!MOZ_LOG_TEST(sMMLog, LogLevel::Verbose)) {
return;
}
if (!aData) {
MOZ_LOG(MMPrinter::sMMLog, LogLevel::Verbose,
("%" PRIu64 " (No Data)", aMsgId));
return;
}
// If aData->SupportsTransferring(), we cannot call Read() more than once.
//
// NOTE(Jan 2026): This is true for almost every StructuredCloneData passed in
// here, which greatly limits PrintData's usability. It _may_ be possible to
// dynamically clear the SupportsTransferring flag for instances which did not
// use any transferables when constructed, but that would require changes to
// StructuredCloneHolder's internals.
if (aData->SupportsTransferring()) {
MOZ_LOG(MMPrinter::sMMLog, LogLevel::Verbose,
("%" PRIu64 " (Supports Transferring)", aMsgId));
return;
}
AutoJSAPI jsapi;
// We're using this context to deserialize, stringify, and print a message
// manager message here. Since the messages are always sent from and to system
// scopes, we need to do this in a system scope, or attempting to deserialize
// certain privileged objects will fail.
MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
JSContext* cx = jsapi.cx();
/* Read original StructuredCloneData. */
IgnoredErrorResult rv;
JS::Rooted<JS::Value> scdContent(cx);
aData->Read(cx, &scdContent, rv);
if (rv.Failed()) {
// In testing, the only reason this would fail was if there was no data in
// the message; so it seems like this is safe-ish.
MOZ_LOG(MMPrinter::sMMLog, LogLevel::Verbose,
("%" PRIu64 " (Read Failed)", aMsgId));
return;
}
JS::Rooted<JSString*> unevalObj(cx, JS_ValueToSource(cx, scdContent));
nsAutoJSString srcString;
if (!srcString.init(cx, unevalObj)) return;
MOZ_LOG(MMPrinter::sMMLog, LogLevel::Verbose,
("%" PRIu64 " %s", aMsgId, NS_ConvertUTF16toUTF8(srcString).get()));
}
} // namespace mozilla::dom