in PR kern/52639, as well as some general cleaning-up...
(As proposed on tech-kern@ with additional changes and enhancements.)
Details of changes:
* All history arguments are now stored as uintmax_t values[1], both in
the kernel and in the structures used for exporting the history data
to userland via sysctl(9). This avoids problems on some architectures
where passing a 64-bit (or larger) value to printf(3) can cause it to
process the value as multiple arguments. (This can be particularly
problematic when printf()'s format string is not a literal, since in
that case the compiler cannot know how large each argument should be.)
* Update the data structures used for exporting kernel history data to
include a version number as well as the length of history arguments.
* All [2] existing users of kernhist(9) have had their format strings
updated. Each format specifier now includes an explicit length
modifier 'j' to refer to numeric values of the size of uintmax_t.
* All [2] existing users of kernhist(9) have had their format strings
updated to replace uses of "%p" with "%#jx", and the pointer
arguments are now cast to (uintptr_t) before being subsequently cast
to (uintmax_t). This is needed to avoid compiler warnings about
casting "pointer to integer of a different size."
* All [2] existing users of kernhist(9) have had instances of "%s" or
"%c" format strings replaced with numeric formats; several instances
of mis-match between format string and argument list have been fixed.
* vmstat(1) has been modified to handle the new size of arguments in the
history data as exported by sysctl(9).
* vmstat(1) now provides a warning message if the history requested with
the -u option does not exist (previously, this condition was silently
ignored, with only a single blank line being printed).
* vmstat(1) now checks the version and argument length included in the
data exported via sysctl(9) and exits if they do not match the values
with which vmstat was built.
* The kernhist(9) man-page has been updated to note the additional
requirements imposed on the format strings, along with several other
minor changes and enhancements.
[1] It would have been possible to use an explicit length (for example,
uint64_t) for the history arguments. But that would require another
"rototill" of all the users in the future when we add support for an
architecture that supports a larger size. Also, the printf(3) format
specifiers for explicitly-sized values, such as "%"PRIu64, are much
more verbose (and less aesthetically appealing, IMHO) than simply
using "%ju".
[2] I've tried very hard to find "all [the] existing users of kernhist(9)"
but it is possible that I've missed some of them. I would be glad to
update any stragglers that anyone identifies.
its timestamps.
As this changes storage structures for data passed between kernel and
userland, welcome to 7.99.55!
XXX Output routines still use microsecond resolution when printf()ing.
XXX Possible future feature would be addition of option to use
XXX getbintime(9) for less time-critical histories.
1) really prints all the histories merged together (rather than just the
"first" when no argument specified
2) dumps a single history when an argument is given, e.g.
"show kernhist usbhist"
3) uses db_printf correctly
a kernel history, settable via the SCDEBUG_KERNHIST flag.
this requires a fairly significantly different set of messages than the
normal debug as histories are restricted:
- each message can take one literal format string and upto 4
arguments
- the arguments can not be strings if you want vmstat -u to
work (this could be fixed, and i might, as it would be nice
if we could print syscall names as well as numbers.)
introduce SCDEBUG_DEFAULT that is settable in the kernel config.
fix a problem in kernhist_dump_histories() where it would crash when a
history with no allocated entries was found.
extend kernhist_dumpmask() to handle the usbhist and scdebughist.
rename "UVMHIST" option to enable the uvm histories.
TODO:
- make UVMHIST properly depend upon KERNHIST
- enable dynamic registration of histories. this is mostly just
allocating something in a bitmap, and is only for viewing multiple
histories in a merged form.
tested on amd64 and sparc64.
