Build kernel hooks so that the lsof port doesn't need to grovel in kvm and isn't tied to a specific kernel build.
Serial console and polled I/O
When using a serial console, kernel printfs end up calling into a polled I/O path, potentially stalling kernel operations until the output is finished being transmitted. This is a particular problem at 9600 baud. (Examples of kernel printfs include link state messages, aac(4) COMMAND TIMEOUT messages, etc.) Polled I/O is probably still needed for the debugger, panic handling, etc.
Printf() ends up invoking cnputc(), which calls siocnputc() in the default 6.x serial console case and uart_cnputc() in the default 8.x serial console case. These functions spin while waiting for the tx register to be ready.
- Apparently jhb@ has been discussing approaches here
- Attilio has done related work in the past, related to messages output during boot
printf tprintf uprintf log sysctl kern.consmsgbuf_size sysctl kern.msgbuf sysctl kern.msgbuf_clear sysctl security.bsd.unprivileged_read_msgbuf /dev/klog
Kernel core enhancements
Be able to extract the following from a core:
- hash (sha-1 etc.) of kern.bootfile to positively identify the kernel binary that was running
- current time of day
reqst00277326 [debug] Include kernel ident data at panic time reqst00193848 Add softclock backlog text to sw watchdog panic to aid in debugging
Serial debugger use with conserver
A remote serial debugging session can be initiated by using "kgdb -r" if a local serial port is available and connected to the device under test. Extend this to communicate with a device under test connected via the Conserver port.
Add a command to gdb or lldb to allow searching memory for a value or byte string. Now implemented in lldb r186127.
USB kernel debugging
Per-jail release overrides
Allow release-related variables to be set on a jail-wide basis.
kern.osreldate (see https://reviews.freebsd.org/D1948)
- bz and kib interested
- Should be relatively easy to implement in the 9.1+ jail infrastructure
Add support for mounting in jails:
- devfs (Possible in 9.1+ via allow.mount.devfs)
- nullfs (Possible in 9.1+ via allow.mount.nullfs)
Comprehensive time accounting
Completely avoid statclock vs hardclock aliasing and other issues by switching from sampled CPU time accounting to comprehensive (i.e., by recording a CPU counter on each context switch).