ktrace: Record namei violations with KTR_CAPFAIL

[jfree]

Summary

Report namei path lookups while Capsicum violation tracing with
CAPFAIL_NAMEI. vfs caching is also ignored when tracing to mimic
capability mode behavior.

Programs that are not yet Capsicumized may be traced to discover
potential capability failures. With `ktrace -t p` and kdump, you
are given a list of syscalls as a starting point for program
Capsicumization.

[jfree]

Change NI_LCF_STRICTRELATIVE to NI_LCF_STRICTREL where applicable.

[markj]

sys/kern/uipc_syscalls.c

496

Consider making it a bit clearer that this is symbolic by writing "<AT_FDCWD>" instead, same above.

sys/kern/vfs_lookup.c

245

Are you sure that this string is nul-terminated?

[jfree]

sys/kern/vfs_lookup.c

245

Are you sure that this string is nul-terminated?

It looks like cn_pnbuf is copied in using copyinstr(9) inside of namei_getpath(). A quick look at some copyinstr(9) assembly indicates that its return buffer will be nul-terminated upon success.

namei_getpath() is called at the beginning of the namei() routine, so I'm pretty certain that cn_pnbuf should always be nul-terminated.

[jfree]

sys/kern/vfs_lookup.c

245

I should also note that it doesn't look like cn_pnbuf is modified anywhere, so its nul-terminator should never be overwritten.

[jfree]

Replace all instances of "AT_FDCWD" with "<AT_FDCWD>" when reporting a violation via ktrcapfail().

[jfree]

• Record *namei* violations instead of vfs. Slight wording change for clarity.
• Rebase on main after several months