os_log in kernel

Question

liszt OP

Created Oct ’16

Replies 5

Boosts 0

Views 2.6k

Participants 3

I am not having any success with using

os_log

in my KEXT. I've tried with both the

OS_LOG_DEFAULT

log and creating a specific log with

os_log_create

. Regardless of the code I try, I cannot see the KEXT log messages in Console.app. Same with using the command line

log stream --level debug --predicate 'subsystem == "com.example.subsystem"'

(and without subsystem filtering). Am I missing something here?

Boost

Answer 1

liszt OP

Oct ’16

The

os_log

functions are working in my kext, but it appears that

os_log_create

is not working as expected. Whether I use

OS_LOG_DEFAULT

or a custom subsystem/category from

os_log_create

, the

log

command does not show a subsystem or category attached to os_log messages from my kext. The log config settings do not seem to change the subsystem/category behavior.

0

Answer 2

liszt OP

Oct ’16

As a workaround for what I want (filtering the log stream for my subsystem's messages), I found that I can pass

log stream

a predicate like

--predicate 'senderImagePath == "/Library/Extensions/MyKext.kext/Contents/MacOS/MyKext"'

.

0

Answer 3

liszt OP

Oct ’16

Filed bug report 28948441.

0

Answer 4

DTS Engineer OP

Apple

Oct ’16

Filed bug report 28948441.

I don’t know what’s going on here, alas, but I wanted to thank you for posting follow ups and for filing that bug report.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

0

Answer 5

dmaclach OP

Apr ’21

Raising a thread from the dead, but for folks having issues with os_log and KEXT.

For some reason I can't add an URL directly, but try https://dmaclach.medium.com/logging-in-kernel-extensions-kexts-on-macos-b558472a9d92 for info.

Filed as FB9069234 for better documentation on os_log.

0