Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

What:		/sys/kernel/debug/kmemtrace/

Date:		July 2008

Contact:	Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>

Description:

In kmemtrace-enabled kernels, the following files are created:

/sys/kernel/debug/kmemtrace/

	cpu<n>		(0400)	Per-CPU tracing data, see below. (binary)

	total_overruns	(0400)	Total number of bytes which were dropped from

				cpu<n> files because of full buffer condition,

				non-binary. (text)

	abi_version	(0400)	Kernel's kmemtrace ABI version. (text)

Each per-CPU file should be read according to the relay interface. That is,

the reader should set affinity to that specific CPU and, as currently done by

the userspace application (though there are other methods), use poll() with

an infinite timeout before every read(). Otherwise, erroneous data may be

read. The binary data has the following _core_ format:

	Event ID	(1 byte)	Unsigned integer, one of:

		0 - represents an allocation (KMEMTRACE_EVENT_ALLOC)

		1 - represents a freeing of previously allocated memory

		    (KMEMTRACE_EVENT_FREE)

	Type ID		(1 byte)	Unsigned integer, one of:

		0 - this is a kmalloc() / kfree()

		1 - this is a kmem_cache_alloc() / kmem_cache_free()

		2 - this is a __get_free_pages() et al.

	Event size	(2 bytes)	Unsigned integer representing the

					size of this event. Used to extend

					kmemtrace. Discard the bytes you

					don't know about.

	Sequence number	(4 bytes)	Signed integer used to reorder data

					logged on SMP machines. Wraparound

					must be taken into account, although

					it is unlikely.

	Caller address	(8 bytes)	Return address to the caller.

	Pointer to mem	(8 bytes)	Pointer to target memory area. Can be

					NULL, but not all such calls might be

					recorded.

In case of KMEMTRACE_EVENT_ALLOC events, the next fields follow:

	Requested bytes	(8 bytes)	Total number of requested bytes,

					unsigned, must not be zero.

	Allocated bytes (8 bytes)	Total number of actually allocated

					bytes, unsigned, must not be lower

					than requested bytes.

	Requested flags	(4 bytes)	GFP flags supplied by the caller.

	Target CPU	(4 bytes)	Signed integer, valid for event id 1.

					If equal to -1, target CPU is the same

					as origin CPU, but the reverse might

					not be true.

The data is made available in the same endianness the machine has.

Other event ids and type ids may be defined and added. Other fields may be

added by increasing event size, but see below for details.

Every modification to the ABI, including new id definitions, are followed

by bumping the ABI version by one.

Adding new data to the packet (features) is done at the end of the mandatory

data:

	Feature size	(2 byte)

	Feature ID	(1 byte)

	Feature data	(Feature size - 3 bytes)

Users:

	kmemtrace-user - git://repo.or.cz/kmemtrace-user.git

	ISAPNP	ISA PnP code is enabled.

	ISDN	Appropriate ISDN support is enabled.

	JOY	Appropriate joystick support is enabled.

	KMEMTRACE kmemtrace is enabled.

	LIBATA  Libata driver is enabled

	LP	Printer support is enabled.

	LOOP	Loopback device support is enabled.

			use the HighMem zone if it exists, and the Normal

			zone if it does not.

	kmemtrace.enable=	[KNL,KMEMTRACE] Format: { yes | no }

				Controls whether kmemtrace is enabled

				at boot-time.

	kmemtrace.subbufs=n	[KNL,KMEMTRACE] Overrides the number of

			subbufs kmemtrace's relay channel has. Set this

			higher than default (KMEMTRACE_N_SUBBUFS in code) if

			you experience buffer overruns.

	movablecore=nn[KMG]	[KNL,X86-32,IA-64,PPC,X86-64] This parameter

			is similar to kernelcore except it specifies the

			amount of memory used for migratable allocations.

	tp720=		[HW,PS2]

	trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.

	trix=		[HW,OSS] MediaTrix AudioTrix Pro

			Format:

			<io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>

'x'	- Used by xmon interface on ppc/powerpc platforms.

'z'	- Dump the ftrace buffer

'0'-'9' - Sets the console log level, controlling which kernel messages

          will be printed to your console. ('0', for example would make

          it so that only emergency messages like PANICs or OOPSes would

#include <linux/tracepoint.h>

DECLARE_TRACE(subsys_eventname,

	TPPROTO(int firstarg, struct task_struct *p),

	TPARGS(firstarg, p));

	TP_PROTO(int firstarg, struct task_struct *p),

	TP_ARGS(firstarg, p));

In subsys/file.c (where the tracing statement must be added) :

    - subsys is the name of your subsystem.

    - eventname is the name of the event to trace.

- TPPROTO(int firstarg, struct task_struct *p) is the prototype of the

- TP_PROTO(int firstarg, struct task_struct *p) is the prototype of the

  function called by this tracepoint.

- TPARGS(firstarg, p) are the parameters names, same as found in the

- TP_ARGS(firstarg, p) are the parameters names, same as found in the

  prototype.

Connecting a function (probe) to a tracepoint is done by providing a

* Probe / tracepoint example

See the example provided in samples/tracepoints/src

See the example provided in samples/tracepoints

Compile them with your kernel.

Compile them with your kernel.  They are built during 'make' (not

'make modules') when CONFIG_SAMPLE_TRACEPOINTS=m.

Run, as root :

modprobe tracepoint-example (insmod order is not important)

modprobe tracepoint-probe-example

cat /proc/tracepoint-example (returns an expected error)

rmmod tracepoint-example tracepoint-probe-example

modprobe tracepoint-sample (insmod order is not important)

modprobe tracepoint-probe-sample

cat /proc/tracepoint-sample (returns an expected error)

rmmod tracepoint-sample tracepoint-probe-sample

dmesg