path: root/arch/x86/kernel/ds.c

/*
 * Debug Store support
 *
 * This provides a low-level interface to the hardware's Debug Store
 * feature that is used for branch trace store (BTS) and
 * precise-event based sampling (PEBS).
 *
 * It manages:
 * - DS and BTS hardware configuration
 * - buffer overflow handling (to be done)
 * - buffer access
 *
 * It does not do:
 * - security checking (is the caller allowed to trace the task)
 * - buffer allocation (memory accounting)
 *
 *
 * Copyright (C) 2007-2009 Intel Corporation.
 * Markus Metzger <markus.t.metzger@intel.com>, 2007-2009
 */

#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/trace_clock.h>

#include <asm/ds.h>

#include "ds_selftest.h"

/*
 * The configuration for a particular DS hardware implementation:
 */
struct ds_configuration {
	/* The name of the configuration: */
	const char		*name;

	/* The size of pointer-typed fields in DS, BTS, and PEBS: */
	unsigned char		sizeof_ptr_field;

	/* The size of a BTS/PEBS record in bytes: */
	unsigned char		sizeof_rec[2];

	/* The number of pebs counter reset values in the DS structure. */
	unsigned char		nr_counter_reset;

	/* Control bit-masks indexed by enum ds_feature: */
	unsigned long		ctl[dsf_ctl_max];
};
static struct ds_configuration ds_cfg __read_mostly;


/* Maximal size of a DS configuration: */
#define MAX_SIZEOF_DS		0x80

/* Maximal size of a BTS record: */
#define MAX_SIZEOF_BTS		(3 * 8)

/* BTS and PEBS buffer alignment: */
#define DS_ALIGNMENT		(1 << 3)

/* Number of buffer pointers in DS: */
#define NUM_DS_PTR_FIELDS	8

/* Size of a pebs reset value in DS: */
#define PEBS_RESET_FIELD_SIZE	8

/* Mask of control bits in the DS MSR register: */
#define BTS_CONTROL				  \
	( ds_cfg.ctl[dsf_bts]			| \
	  ds_cfg.ctl[dsf_bts_kernel]		| \
	  ds_cfg.ctl[dsf_bts_user]		| \
	  ds_cfg.ctl[dsf_bts_overflow] )

/*
 * A BTS or PEBS tracer.
 *
 * This holds the configuration of the tracer and serves as a handle
 * to identify tracers.
 */
struct ds_tracer {
	/* The DS context (partially) owned by this tracer. */
	struct ds_context	*context;
	/* The buffer provided on ds_request() and its size in bytes. */
	void			*buffer;
	size_t			size;
};

struct bts_tracer {
	/* The common DS part: */
	struct ds_tracer	ds;

	/* The trace including the DS configuration: */
	struct bts_trace	trace;

	/* Buffer over