MemorySanitizer (MSan) is a tool that detects use of uninitialized Memory Wave Routine. MSan in Chromium is unlikely to be usable on programs aside from Ubuntu Precise/Trusty - please see the notice on instrumented libraries below. There are additionally two LKGR builders for ClusterFuzz: no origins, chained origins (see below for clarification). V8 deployment is ongoing. You may seize recent Chrome binaries for Linux built with MSan here. MSan requires using Instrumented system libraries. Be aware that instrumented libraries are supported on Ubuntu Exact/Trusty only. 64: JavaScript code will probably be compiled for ARM64 and run on an ARM64 simulator. This enables MSan to instrument JS code. With out this flag there can be false experiences. Some widespread flags might break a MSAN construct. If you are attempting to reproduce a check run from the Linux ChromiumOS MSan Assessments construct, different GN args might even be wanted. You possibly can look for them via your check run page, under the part "lookup builder GN args". Run the ensuing binaries as traditional.

Chrome must not use hardware OpenGL when running under MSan. SwANGLE can be utilized as a software OpenGL implementation, although it is extremely gradual. This forces Chrome to make use of the software path for compositing and raster. WebGL will nonetheless work utilizing SwANGLE. This switches Chrome to make use of SwANGLE for compositing, (possibly) raster and WebGL. Use this if you don't care concerning the actual pixel output. This exercises the default code paths, nevertheless expensive SwANGLE calls are replaced with stubs (i.e. nothing truly will get drawn to the display). If neither flag is specified, Chrome will fall back to the first possibility after the GPU process crashes with an MSan report. MSan allows the user to trade off execution velocity for the amount of data provided in reports. 0: MSan will inform you the place the uninitialized value was used, but not the place it came from. That is the quickest mode. 1 (deprecated): MSan may even inform you where the uninitialized worth was originally allotted (e.g. which malloc() call, or which native variable).

2, and its use is discouraged. We do not present pre-constructed instrumented libraries for this mode. 2 (default): MSan will even report the chain of stores that copied the uninitialized worth to its ultimate location. If there are more than 7 shops in the chain, solely the primary 7 shall be reported. Note that compilation time may enhance on this mode. MSan does not support suppressions. This is an intentional design selection. We have a blocklist file which is applied at compile time, and is used mainly to compensate for device points. Blocklist guidelines do not work the way suppression guidelines do - fairly than suppressing experiences with matching stack traces, they alter the best way MSan instrumentation is applied to the matched perform. Please refrain from making adjustments to the blocklist file unless you recognize what you're doing. Note additionally that instrumented libraries use separate blocklist files. Please understand that merely studying/copying uninitialized memory is not going to trigger an MSan report.

Even easy arithmetic computations will work. To provide a report, the code has to do something important with the uninitialized value, e.g. department on it, pass it to a libc function or Memory Wave Routine use it to index an array. In the event you see a DSO underneath a system-wide directory (e.g. /lib/), then the report is probably going bogus and should be fastened by simply including that DSO to the list of instrumented libraries (please file a bug under Stability-Memory-MemorySanitizer and/or ping eugenis@). Inline assembly is also likely to trigger bogus stories. If you are attempting to debug a V8-related situation, please remember the fact that MSan builds run V8 in ARM64 mode, as explained under. MSan reserves a separate memory region ("shadow memory") through which it tracks the standing of software memory. The correspondence between the 2 is bit-to-bit: if the shadow bit is ready to 1, the corresponding bit in the application memory is taken into account "poisoned" (i.e. uninitialized). The header file declares interface features which can be utilized to study and manipulate the shadow state without changing the appliance memory, which is available in useful when debugging MSan stories. Die() will stop execution in the debugger after MSan prints diagnostic info, however before this system terminates. Print the whole shadow state of a variety of utility Memory Wave, together with the origins of all uninitialized values, if any. The next forces an MSan test, i.e. if any bits within the memory range are uninitialized the decision will crash with an MSan report. MSan, but please CC eugenis@ if you happen to intend to do so.

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Pub: 12 Aug 2025 04:29 UTC

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