read(2), which meant that records longer than the buffer passed to read(2)
were dropped. Instead take the approach of allowing partial reads to be
continued across multiple system calls more in the style of streaming
character device.
This means retaining a record on the per-pipe queue in a partially read
state, so maintain a current offset into the record. Keep the record on
the queue during a read, so add a new lock, ap_sx, to serialize removal
of records from the queue by either read(2) or ioctl(2) requesting a pipe
flush. Modify the kqueue handler to return bytes left in the current
record rather than simply the size of the current record.
It is now possible to use praudit, which used the standard FILE * buffer
sizes, to track much larger record sizes from /dev/auditpipe, such as
very long command lines to execve(2).
MFC after: 2 months
Sponsored by: Apple, Inc.
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