Re: VIRIDIAN CRASH: 3b c0000096 75b12c5 9e7f1580 0

[Jan Beulich <jbeulich@xxxxxxxx>]

On 03.02.2021 16:04, Paul Durrant wrote:
>> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan 
>> Beulich
>> Sent: 03 February 2021 14:55
>>
>> On 01.02.2021 16:26, James Dingwall wrote:
>>> 21244@1612191983.282480:xen_platform_log xen platform: XEN|BUGCHECK: 
>>> EXCEPTION (0000A824848948C2):
>>> 21244@1612191983.282617:xen_platform_log xen platform: XEN|BUGCHECK: 
>>> CONTEXT (FFFFD0014343D580):
>>> 21244@1612191983.282717:xen_platform_log xen platform: XEN|BUGCHECK: - GS = 
>>> 002B
>>> 21244@1612191983.282816:xen_platform_log xen platform: XEN|BUGCHECK: - FS = 
>>> 0053
>>> 21244@1612191983.282914:xen_platform_log xen platform: XEN|BUGCHECK: - ES = 
>>> 002B
>>> 21244@1612191983.283011:xen_platform_log xen platform: XEN|BUGCHECK: - DS = 
>>> 002B
>>> 21244@1612191983.283127:xen_platform_log xen platform: XEN|BUGCHECK: - SS = 
>>> 0018
>>> 21244@1612191983.283226:xen_platform_log xen platform: XEN|BUGCHECK: - CS = 
>>> 0010
>>> 21244@1612191983.283332:xen_platform_log xen platform: XEN|BUGCHECK: - 
>>> EFLAGS = 00000202
>>> 21244@1612191983.283444:xen_platform_log xen platform: XEN|BUGCHECK: - RDI 
>>> = 00000000F64D5C20
>>> 21244@1612191983.283555:xen_platform_log xen platform: XEN|BUGCHECK: - RSI 
>>> = 00000000F6367280
>>> 21244@1612191983.283666:xen_platform_log xen platform: XEN|BUGCHECK: - RBX 
>>> = 000000008011E060
>>> 21244@1612191983.283810:xen_platform_log xen platform: XEN|BUGCHECK: - RDX 
>>> = 00000000F64D5C20
>>> 21244@1612191983.283972:xen_platform_log xen platform: XEN|BUGCHECK: - RCX 
>>> = 0000000000000199
>>> 21244@1612191983.284350:xen_platform_log xen platform: XEN|BUGCHECK: - RAX 
>>> = 0000000000000004
>>> 21244@1612191983.284523:xen_platform_log xen platform: XEN|BUGCHECK: - RBP 
>>> = 000000004343E891
>>> 21244@1612191983.284658:xen_platform_log xen platform: XEN|BUGCHECK: - RIP 
>>> = 00000000A43C72C5
>>> 21244@1612191983.284842:xen_platform_log xen platform: XEN|BUGCHECK: - RSP 
>>> = 000000004343DFA0
>>> 21244@1612191983.284959:xen_platform_log xen platform: XEN|BUGCHECK: - R8 = 
>>> 0000000000000008
>>> 21244@1612191983.285073:xen_platform_log xen platform: XEN|BUGCHECK: - R9 = 
>>> 000000000000000E
>>> 21244@1612191983.285188:xen_platform_log xen platform: XEN|BUGCHECK: - R10 
>>> = 0000000000000002
>>> 21244@1612191983.285304:xen_platform_log xen platform: XEN|BUGCHECK: - R11 
>>> = 000000004343E808
>>> 21244@1612191983.285420:xen_platform_log xen platform: XEN|BUGCHECK: - R12 
>>> = 0000000000000000
>>> 21244@1612191983.285564:xen_platform_log xen platform: XEN|BUGCHECK: - R13 
>>> = 00000000F7964E50
>>> 21244@1612191983.285680:xen_platform_log xen platform: XEN|BUGCHECK: - R14 
>>> = 00000000F64D5C20
>>> 21244@1612191983.285796:xen_platform_log xen platform: XEN|BUGCHECK: - R15 
>>> = 00000000F7964E50
>>
>> I'm also confused by this - the pointer given for CONTEXT suggests this
>> is a 64-bit kernel, yet none of the registers - including RIP and RSP -
>> have non-zero upper 32 bits. Or is qemu truncating these values?
> 
> The logging is coming from the PV drivers (in 
> https://xenbits.xen.org/gitweb/?p=pvdrivers/win/xenbus.git;a=blob;f=src/xen/bug_check.c).
>  The truncated values may just be due to a 32-bit user process I guess.

Since you pointed me at the code and truncation inside a string
not likely being due to some user process, I went and looked:
The driver uses %016X, instead of e.g. converting to (PVOID)
and using %p like code elsewhere in the file does (presumably
because there's no really convenient way to print 64-bit values
in Windows, short of using their custom "%016I64X" format
specifier, and the absence of a uniform specifier allowing to
format pointer-sized integers independent of architecture).

Jan