path: root/arch/arm/kernel/hw_breakpoint.c

/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) 2009, 2010 ARM Limited
 *
 * Author: Will Deacon <will.deacon@arm.com>
 */

/*
 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
 * using the CPU's debug registers.
 */
#define pr_fmt(fmt) "hw-breakpoint: " fmt

#include <linux/errno.h>
#include <linux/hardirq.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
#include <linux/smp.h>
#include <linux/cpu_pm.h>

#include <asm/cacheflush.h>
#include <asm/cputype.h>
#include <asm/current.h>
#include <asm/hw_breakpoint.h>
#include <asm/kdebug.h>
#include <asm/traps.h>
#include <asm/hardware/coresight.h>

/* Breakpoint currently in use for each BRP. */
static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);

/* Watchpoint currently in use for each WRP. */
static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);

/* Number of BRP/WRP registers on this CPU. */
static int core_num_brps;
static int core_num_wrps;

/* Debug architecture version. */
static u8 debug_arch;

/* Does debug architecture support OS Save and Restore? */
static bool has_ossr;

/* Maximum supported watchpoint length. */
static u8 max_watchpoint_len;

#define READ_WB_REG_CASE(OP2, M, VAL)			\
	case ((OP2 << 4) + M):				\
		ARM_DBG_READ(c0, c ## M, OP2, VAL);	\
		break

#define WRITE_WB_REG_CASE(OP2, M, VAL)			\
	case ((OP2 << 4) + M):				\
		ARM_DBG_WRITE(c0, c ## M, OP2, VAL);	\
		break

#define GEN_READ_WB_REG_CASES(OP2, VAL)		\
	READ_WB_REG_CASE(OP2, 0, VAL);		\
	READ_WB_REG_CASE(OP2, 1, VAL);		\
	READ_WB_REG_CASE(OP2, 2, VAL);		\
	READ_WB_REG_CASE(OP2, 3, VAL);		\
	READ_WB_REG_CASE(OP2, 4, VAL);		\
	READ_WB_REG_CASE(OP2, 5, VAL);		\
	READ_WB_REG_CASE(OP2, 6, VAL);		\
	READ_WB_REG_CASE(OP2, 7, VAL);		\
	READ_WB_REG_CASE(OP2, 8, VAL);		\
	READ_WB_REG_CASE(OP2, 9, VAL);		\
	READ_WB_REG_CASE(OP2, 10, VAL);		\
	READ_WB_REG_CASE(OP2, 11, VAL);		\
	READ_WB_REG_CASE(OP2, 12, VAL);		\
	READ_WB_REG_CASE(OP2, 13, VAL);		\
	READ_WB_REG_CASE(OP2, 14, VAL);		\
	READ_WB_REG_CASE(OP2, 15, VAL)

#define GEN_WRITE_WB_REG_CASES(OP2, VAL)	\
	WRITE_WB_REG_CASE(OP2, 0, VAL);		\
	WRITE_WB_REG_CASE(OP2, 1, VAL);		\
	WRITE_WB_REG_CASE(OP2, 2, VAL);		\
	WRITE_WB_REG_CASE(OP2, 3, VAL);		\
	WRITE_WB_REG_CASE(OP2, 4, VAL);		\
	WRITE_WB_REG_CASE(OP2, 5, VAL);		\
	WRITE_WB_REG_CASE(OP2, 6, VAL);		\
	WRITE_WB_REG_CASE(OP2, 7, VAL);		\
	WRITE_WB_REG_CASE(OP2, 8, VAL);		\
	WRITE_WB_REG_CASE(OP2, 9, VAL);		\
	WRITE_WB_REG_CASE(OP2, 10, VAL);	\
	WRITE_WB_REG_CASE(OP2, 11, VAL);	\
	WRITE_WB_REG_CASE(OP2, 12, VAL);	\
	WRITE_WB_REG_CASE(OP2, 13, VAL);	\
	WRITE_WB_REG_CASE(OP2, 14, VAL);	\
	WRITE_WB_REG_CASE(OP2, 15, VAL)

static u32 read_wb_reg(int n)
{
	u32 val = 0;

	switch (n) {
	GEN_READ_WB_REG_CASES(ARM_OP2_BVR, val);
	GEN_READ_WB_REG_CASES(ARM_OP2_BCR, val);
	GEN_READ_WB_REG_CASES(ARM_OP2_WVR, val);
	GEN_READ_WB_REG_CASES(ARM_OP2_WCR, val);
	default:
		pr_warning("attempt to read from unknown breakpoint "
				"register %d\n", n);
	}

	return val;
}

static void write_wb_reg(int n, u32 val)
{
	switch (n) {
	GEN_WRITE_WB_REG_CASES(ARM_OP2_BVR, val);
	GEN_WRITE_WB_REG_CASES(ARM_OP2_BCR, val);
	GEN_WRITE_WB_REG_CASES(ARM_OP2_WVR, val);
	GEN_WRITE_WB_REG_CASES(ARM_OP2_WCR, val);
	default:
		pr_warning("attempt to write to unknown breakpoint "
				"register %d\n", n);
	}
	isb();
}

/* Determine debug architecture. */
static u8 get_debug_arch(void)
{
	u32 didr;

	/* Do we implement the extended CPUID interface? */
	if (((read_cpuid_id() >> 16) & 0xf) != 0xf) {
		pr_warn_once("CPUID feature registers not supported. "
			     "Assuming v6 debug is present.\n");
		return ARM_DEBUG_ARCH_V6;
	}

	ARM_DBG_READ(c0, c0, 0, didr);
	return (didr >> 16) & 0xf;
}

u8 arch_get_debug_arch(void)
{
	return debug_arch;
}

static int debug_arch_supported(void)
{
	u8 arch = get_debug_arch();

	/* We don't support the memory-mapped interface. */
	return (arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14) ||
		arch >= ARM_DEBUG_ARCH_V7_1;
}

/* Can we determine the watchpoint access type from the fsr? */
static int debug_exception_updates_fsr(void)
{
	return 0;
}

/* Determine number of WRP registers available. */
static int get_num_wrp_resources(void)
{
	u32 didr;
	ARM_DBG_READ(c0, c0, 0, didr);
	return ((didr >> 28) & 0xf) + 1;
}

/* Determine number of BRP registers available. */
static int get_num_brp_resources(void)
{
	u32 didr;
	ARM_DBG_READ(c0,