Previously, only the top-level exception code was reported via the
Crashpad.ExceptionCode.Mac histogram. Making this histogram work
(https://crbug.com/678720) has revealed that Chrome is triggering
EXC_RESOURCE exceptions at a rate in excess of 4x that of ordinary
crashes. These exceptions were not previously visible because they are
not uploaded unless the system treats them as fatal, which it does not
normally do absent an explicit request.
In order to learn more about the problem, this change augments the data
reported via the Crashpad.ExceptionCode.Mac histogram to report (at
least) second-level exception data. This means that we will no longer
see just EXC_RESOURCE, but potentially more useful information such as
EXC_RESOURCE / RESOURCE_TYPE_IO / FLAVOR_IO_PHYSICAL_WRITES. This also
applies to other exception types, so that the majority of crashes
currently falling into the EXC_CRASH bucket will now have additional
information decoded and will be reported as, for example, EXC_BAD_ACCESS
/ KERN_INVALID_ADDRESS, EXC_BAD_INSTRUCTION / EXC_I386_INVOP, and
EXC_CRASH / SIGABRT.
Because the old mechanism was only live (in an “it works” sense) for
several days, and the new mechanism does not overlap with histogram
values used by the old one, there’s no need to invent a new histogram
name.
BUG=chromium:684051
Change-Id: Ia0a372b4127f7b3b2e7dbbaac9304cce3b5aadfe
Reviewed-on: https://chromium-review.googlesource.com/430933
Reviewed-by: Scott Graham <scottmg@chromium.org>
This adds IsExceptionNonfatalResource() and its test, and uses it in
crashpad_handler. When non-fatal resource exceptions are encountered, no
crash report is generated. crashpad_handler swallows these exceptions.
Alternatively, it could allow them to be sent to the system’s host-level
resource exception handler, normally com.apple.ReportCrash.root, which
would allow them to be processed in the same way as when Crashpad is not
in use. I’m not sure which option is better. I chose to swallow them
because there doesn’t appear to be much value in letting
com.apple.ReportCrash.root and spindump look at them.
This also moves ExcCrashRecoverOriginalException() to the new file as a
sibling of IsExceptionNonfatalResource(). This provides better
organization.
BUG=crashpad:35, chromium:474163, chromium:474326
TEST=crashpad_util_test ExceptionTypes.IsExceptionNonfatalResource
R=rsesek@chromium.org
Review URL: https://codereview.chromium.org/1066243002
These two exception types use all 64 bits of the code[0] field. The
ExceptionSnapshot was unprepared to stuff this into a 32-bit field. To
resolve the discrepancy, the more-significant data is taken from the
high 32 bits of code[0]. No information is lost because the full code[0]
is made available as part of the Codes() vector.
BUG=crashpad:34
R=rsesek@chromium.org
Review URL: https://codereview.chromium.org/1050313003
