TobalJackson
Contributor
Contributor

GDB Stub breakpoints not triggering on MacOS guest

Hello,
I recently upgraded vmware fusion from 11.x to 12.1.2 and it seems as though the
gdb stub kernel debugging feature has some issue regarding the triggering of
breakpoints on Mac OS guest systems.

My host is Mac OS Big Sur 11.3.1, and my guest is Big Sur 11.4 (latest). I have
the KDK installed that matches the version of my guest, as well as make sure to
load the kdk modules in my lldbinit: ("settings set
target.load-script-from-symbol-file true"). My lldb version is lldb-1205.0.27.3.

With all this in place, and after starting up the guest system, running lldb and
using the "gdb-remote 8864" command results in pausing the guest system as well
as loading all the XNU helper scripts. At this point I can resolve symbols and
function names, and even set breakpoints.

The issue is that none of the breakpoints are triggered when they should be.
I've tested with a handful of functions that should be hitting all the time,
however none of them are being broken on like they should.

I set breakpoints on these functions:

mach_call_munger
mach_call_munger64
unix_syscall
unix_syscall64
mach_msg_trap
mach_msg_send
mach_msg_receive

and 'c'ontinued my guest's execution, and yet none of these breakpoints are hit.
When I pause execution with ctrl+c I can inspect memory, disassemble functions,
and do all of the other lldb/debugger commands I try. It seems just that
breakpoints themselves are not working.

Has anyone experienced similar issues or know why this may be happening for me?
I've tried reformatting and doing fresh installs, as well as trying older
versions of lldb but to no avail. I have a feeling that something has gone awry
with the gdb stub subsystem/functionality of VMware Fusion that is preventing it
from triggering breakpoints, but I'm not sure.

If anyone would like additional information in order to discover more about this
issue, or has information that would help me fix this issue, please let me know.

Thank you

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3 Replies
wila
Leadership
Leadership

Hi,

Did you see this post already?
https://communities.vmware.com/t5/VMware-Fusion-Discussions/Using-GDB-stub-for-macOS-11-0-guest-caus...

--
Wil

| Author of Vimalin. The virtual machine Backup app for VMware Fusion, VMware Workstation and Player |
| More info at vimalin.com | Twitter @wilva
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TobalJackson
Contributor
Contributor

Hello wila,

I hadn't seen that post before. However I did just try setting that option to FALSE in my vm's vmx configuration with mixed results. It seems to allow the breakpoints to hit (sometimes), however lldb crashes after hitting a number of breakpoints. I'll continue experimenting with this however.

Thank you for sharing that post though, it did give me something else to try. Please let me know if there have been any updates on the accepted answer of that post, I'm curious if there's been progress from the efforts between VMware and Apple.

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wila
Leadership
Leadership

Hi,

I have no idea, just remembered I had read that thread and figured to point you to it.

Perhaps @covelli is able to share some news about this issue.

--
Wil

| Author of Vimalin. The virtual machine Backup app for VMware Fusion, VMware Workstation and Player |
| More info at vimalin.com | Twitter @wilva
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