- MFC

Add stack_print_short() and stack_print_short_ddb() interfaces to
stack(9), which generate a more compact rendition of a stack trace
via the kernel's printf.

MFC after: 1 week

integrate from head@185615

Make it possible to compile kernel with KTR but without DDB.

Ktr(9) stores format string and arguments in the event circular buffer,
not the string formatted at the time of CTRX() call. Stack_ktr(9) uses
an on-stack buffer for the symbol name, that is supplied

Ktr(9) stores format string and arguments in the event circular buffer,
not the string formatted at the time of CTRX() call. Stack_ktr(9) uses
an on-stack buffer for the symbol name, that is supplied as an argument
to ktr. As result, stack_ktr() traces show garbage or cause page faults.

Fix stack_ktr() by using pointer to module symbol table that is supposed
to have a longer lifetime.

Tested by: pho
MFC after: 1 week

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Staticize M_STACK.

Approved by: rwatson (mentor)
MFC after: 1 month

When a symbol name can't be resolved, return "??" as the name, rather
than "Unknown func", in order to avoid putting spaces in what ideally
is a string separated by white space.

Break out stack(9) from ddb(4):

- Introduce per-architecture stack_machdep.c to hold stack_save(9).
- Introduce per-architecture machine/stack.h to capture any common
definitions required between

Break out stack(9) from ddb(4):

- Introduce per-architecture stack_machdep.c to hold stack_save(9).
- Introduce per-architecture machine/stack.h to capture any common
definitions required between db_trace.c and stack_machdep.c.
- Add new kernel option "options STACK"; we will build in stack(9) if it is
defined, or also if "options DDB" is defined to provide compatibility
with existing users of stack(9).

Add new stack_save_td(9) function, which allows the capture of a stacktrace
of another thread rather than the current thread, which the existing
stack_save(9) was limited to. It requires that the thread be neither
swapped out nor running, which is the responsibility of the consumer to
enforce.

Update stack(9) man page.

Build tested: amd64, arm, i386, ia64, powerpc, sparc64, sun4v
Runtime tested: amd64 (rwatson), arm (cognet), i386 (rwatson)

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Modify stack(9) stack_print() and stack_sbuf_print() routines to use new
linker interfaces for looking up function names and offsets from
instruction pointers. Create two variants of each call: one

Modify stack(9) stack_print() and stack_sbuf_print() routines to use new
linker interfaces for looking up function names and offsets from
instruction pointers. Create two variants of each call: one that is
"DDB-safe" and avoids locking in the linker, and one that is safe for
use in live kernels, by virtue of observing locking, and in particular
safe when kernel modules are being loaded and unloaded simultaneous to
their use. This will allow them to be used outside of debugging
contexts.

Modify two of three current stack(9) consumers to use the DDB-safe
interfaces, as they run in low-level debugging contexts, such as inside
lockmgr(9) and the kernel memory allocator.

Update man page.

show more ...

Correct typos

MFC after: 2 weeks

Add 'depth' argument to CTRSTACK() macro, which allows to reduce number
of ktr slots used. If 'depth' is equal to 0, the whole stack will be
logged, just like before.

- Add support for saving stack traces and displaying them via printf(9)
and KTR.

Contributed by: Antoine Brodin <antoine.brodin@laposte.net>
Concept code from: Neal Fachan <neal@isilon.com>