NAME
kernhist —
basic low-level kernel
history tracing mechanism
SYNOPSIS
options KERNHIST
#include <sys/kernhist.h>
Below are the functions and macros provided by kernhist.h:
KERNHIST_DECL(
name);
KERNHIST_DEFINE(
name);
KERNHIST_INIT(
name,
unsigned num_entries);
KERNHIST_INITIALIZER(
name,
void *buffer);
KERNHIST_INIT_STATIC(
struct
kern_history name,
void
*buffer);
KERNHIST_LOG(
struct
kern_history name,
const
char *fmt,
u_long
arg0,
u_long arg1,
u_long arg2,
u_long arg3);
KERNHIST_CALLARGS(
struct
kern_history name,
const
char *fmt,
u_long
arg0,
u_long arg1,
u_long arg2,
u_long arg3);
KERNHIST_CALLED(
struct
kern_history name);
KERNHIST_FUNC(
fname);
KERNHIST_DUMP(
struct
kern_history name);
void
kernhist_dump(
struct
kern_history *history);
void
kernhist_dumpmask(
u_int32_t
bitmask);
void
kernhist_print(
void
(*pr)(const char *, ...));
DESCRIPTION
The
kernhist facility provides a very low-level tracing
facility that can be called extremely early in the kernel initialisation. It
provides a simple restricted
printf(3) format syntax with a
maximum of 4 arguments. The format must be a literal string that can be
referenced later as it is not stored with the event, only a pointer to it.
options KERNHIST must be present in the kernel configuration
to enable these functions and macros.
Arguments that require additional dereferences, such as “%s”, will
not work in
vmstat(1), but will
when called from
ddb(4).
A kernel history is a fixed-size buffer of an either statically or dynamically
allocated buffer that is used and read in a cycled basis. It includes the time
an entry was made, the CPU that the entry was recorded from, the
printf(3) like format and
length, the function name and length, the unique call count for this function,
and the 4 argumnts.
These macros provide access to most kernel history functionality:
-
-
- KERNHIST_DECL(name)
- Declare an extern struct kern_history
name.
-
-
- KERNHIST_DEFINE(name)
- Define a struct kern_history
name.
-
-
- KERNHIST_INIT(name,
num_entries)
- Dynamically initialise a kernel history called name with
num_entries entries.
-
-
- KERNHIST_INITIALIZER(name,
buffer)
- Initialise a statically defined kernel history called
name using buffer as a static
allocation used for the buffer.
-
-
- KERNHIST_INIT_STATIC(name,
buffer)
- Initialise a statically declared kernel history
name, using the statically allocated
buffer for history entries.
-
-
- KERNHIST_FUNC(fname)
- Declare necessary variables for kernhist
to be used this function. Callable only once per function.
-
-
- KERNHIST_LOG(name,
fmt, arg0,
arg1, arg2,
arg3)
- For the given kernel history name,
log the format and arguments in the history as a unique event.
-
-
- KERNHIST_CALLED(name)
- Declare a function as being called. Either this or
KERNHIST_CALLARGS() must be used near the function entry
point.
-
-
- KERNHIST_CALLARGS(name,
fmt, arg0,
arg1, arg2,
arg3)
- A frontend to KERNHIST_LOG() that avoids
that “called!” log message in addition to normal
arguments.
-
-
- KERNHIST_DUMP(name)
- Call kernhist_dump() on the named kernel
history.
-
-
- kernhist_dump(history)
- Dump the entire contents of the specified kernel
history.
-
-
- kernhist_dumpmask(bitmask)
- Used to dump a well known list of kernel histories. The
following histories and their respective value (as seen in
kernhist.h) are available:
-
-
- KERNHIST_UVMMAPHIST
- Include events from “maphist”.
-
-
- KERNHIST_UVMPDHIST
- Include events from “pdhist”.
-
-
- KERNHIST_UVMUBCHIST
- Include events from “ubchist”.
-
-
- KERNHIST_UVMLOANHIST
- Include events from “loanhist”.
-
-
- KERNHIST_USBHIST
- Include events from “usbhist”.
-
-
- KERNHIST_SCDEBUGHIST
- Include events from “scdebughist”.
-
-
- kernhist_print(pr)
- Print all the kernel histories to the kernel message
buffer. The pr() argument is currently ignored.
SEE ALSO
vmstat(1),
usbdi(9),
uvm(9)
HISTORY
kernhist was originally written by
Charles D.
Cranor as part of the
uvm(9)
framework, under the name UVMHIST.
Matthew R. Green
generalised it into its current form to be available to non
uvm(9) frameworks.
BUGS
The restriction about using “%s”
printf(3) format strings could
be reduced to literal strings (such as the table of system call names) if
vmstat(1) was extended to
convert “%s” strings into user addresses after copying the strings
out.
KERNHIST_FUNC() could be converted to use __func__ always, as
all the callers already do.
The
kernhist_dumpmask() list of masks could be properly
published and made available, and as such this function may be removed in a
future release.
The
kernhist_print() function currently ignores its
pr argument.