[deliverable/linux.git] / arch / arm64 / kernel / debug-monitors.c

/*
 * ARMv8 single-step debug support and mdscr context switching.
 *
 * Copyright (C) 2012 ARM Limited
 *
 * 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, see <http://www.gnu.org/licenses/>.
 *
 * Author: Will Deacon <will.deacon@arm.com>
 */

#include <linux/cpu.h>
#include <linux/debugfs.h>
#include <linux/hardirq.h>
#include <linux/init.h>
#include <linux/ptrace.h>
#include <linux/kprobes.h>
#include <linux/stat.h>
#include <linux/uaccess.h>

#include <asm/cpufeature.h>
#include <asm/cputype.h>
#include <asm/debug-monitors.h>
#include <asm/system_misc.h>

/* Determine debug architecture. */
u8 debug_monitors_arch(void)
{
	return cpuid_feature_extract_unsigned_field(read_system_reg(SYS_ID_AA64DFR0_EL1),
						ID_AA64DFR0_DEBUGVER_SHIFT);
}

/*
 * MDSCR access routines.
 */
static void mdscr_write(u32 mdscr)
{
	unsigned long flags;
	local_dbg_save(flags);
	asm volatile("msr mdscr_el1, %0" :: "r" (mdscr));
	local_dbg_restore(flags);
}
NOKPROBE_SYMBOL(mdscr_write);

static u32 mdscr_read(void)
{
	u32 mdscr;
	asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr));
	return mdscr;
}
NOKPROBE_SYMBOL(mdscr_read);

/*
 * Allow root to disable self-hosted debug from userspace.
 * This is useful if you want to connect an external JTAG debugger.
 */
static bool debug_enabled = true;

static int create_debug_debugfs_entry(void)
{
	debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
	return 0;
}
fs_initcall(create_debug_debugfs_entry);

static int __init early_debug_disable(char *buf)
{
	debug_enabled = false;
	return 0;
}

early_param("nodebugmon", early_debug_disable);

/*
 * Keep track of debug users on each core.
 * The ref counts are per-cpu so we use a local_t type.
 */
static DEFINE_PER_CPU(int, mde_ref_count);
static DEFINE_PER_CPU(int, kde_ref_count);

void enable_debug_monitors(enum dbg_active_el el)
{
	u32 mdscr, enable = 0;

	WARN_ON(preemptible());

	if (this_cpu_inc_return(mde_ref_count) == 1)
		enable = DBG_MDSCR_MDE;

	if (el == DBG_ACTIVE_EL1 &&
	    this_cpu_inc_return(kde_ref_count) == 1)
		enable |= DBG_MDSCR_KDE;

	if (enable && debug_enabled) {
		mdscr = mdscr_read();
		mdscr |= enable;
		mdscr_write(mdscr);
	}
}
NOKPROBE_SYMBOL(enable_debug_monitors);

void disable_debug_monitors(enum dbg_active_el el)
{
	u32 mdscr, disable = 0;

	WARN_ON(preemptible());

	if (this_cpu_dec_return(mde_ref_count) == 0)
		disable = ~DBG_MDSCR_MDE;

	if (el == DBG_ACTIVE_EL1 &&
	    this_cpu_dec_return(kde_ref_count) == 0)
		disable &= ~DBG_MDSCR_KDE;

	if (disable) {
		mdscr = mdscr_read();
		mdscr &= disable;
		mdscr_write(mdscr);
	}
}
NOKPROBE_SYMBOL(disable_debug_monitors);

/*
 * OS lock clearing.
 */
static void clear_os_lock(void *unused)
{
	asm volatile("msr oslar_el1, %0" : : "r" (0));
}

static int os_lock_notify(struct notifier_block *self,
				    unsigned long action, void *data)
{
	if ((action & ~CPU_TASKS_FROZEN) == CPU_ONLINE)
		clear_os_lock(NULL);
	return NOTIFY_OK;
}

static struct notifier_block os_lock_nb = {
	.notifier_call = os_lock_notify,
};

static int debug_monitors_init(void)
{
	cpu_notifier_register_begin();

	/* Clear the OS lock. */
	on_each_cpu(clear_os_lock, NULL, 1);
	isb();

	/* Register hotplug handler. */
	__register_cpu_notifier(&os_lock_nb);

	cpu_notifier_register_done();
	return 0;
}
postcore_initcall(debug_monitors_init);

/*
 * Single step API and exception handling.
 */
static void set_regs_spsr_ss(struct pt_regs *regs)
{
	regs->pstate |= DBG_SPSR_SS;
}
NOKPROBE_SYMBOL(set_regs_spsr_ss);

static void clear_regs_spsr_ss(struct pt_regs *regs)
{
	regs->pstate &= ~DBG_SPSR_SS;
}
NOKPROBE_SYMBOL(clear_regs_spsr_ss);

/* EL1 Single Step Handler hooks */
static LIST_HEAD(step_hook);
static DEFINE_SPINLOCK(step_hook_lock);

void register_step_hook(struct step_hook *hook)
{
	spin_lock(&step_hook_lock);
	list_add_rcu(&hook->node, &step_hook);
	spin_unlock(&step_hook_lock);
}

void unregister_step_hook(struct step_hook *hook)
{
	spin_lock(&step_hook_lock);
	list_del_rcu(&hook->node);
	spin_unlock(&step_hook_lock);
	synchronize_rcu();
}

/*
 * Call registered single step handlers
 * There is no Syndrome info to check for determining the handler.
 * So we call all the registered handlers, until the right handler is
 * found which returns zero.
 */
static int call_step_hook(struct pt_regs *regs, unsigned int esr)
{
	struct step_hook *hook;
	int retval = DBG_HOOK_ERROR;

	rcu_read_lock();

	list_for_each_entry_rcu(hook, &step_hook, node)	{
		retval = hook->fn(regs, esr);
		if (retval == DBG_HOOK_HANDLED)
			break;
	}

	rcu_read_unlock();

	return retval;
}
NOKPROBE_SYMBOL(call_step_hook);

static void send_user_sigtrap(int si_code)
{
	struct pt_regs *regs = current_pt_regs();
	siginfo_t info = {
		.si_signo	= SIGTRAP,
		.si_errno	= 0,
		.si_code	= si_code,
		.si_addr	= (void __user *)instruction_pointer(regs),
	};

	if (WARN_ON(!user_mode(regs)))
		return;

	if (interrupts_enabled(regs))
		local_irq_enable();

	force_sig_info(SIGTRAP, &info, current);
}

static int single_step_handler(unsigned long addr, unsigned int esr,
			       struct pt_regs *regs)
{
	/*
	 * If we are stepping a pending breakpoint, call the hw_breakpoint
	 * handler first.
	 */
	if (!reinstall_suspended_bps(regs))
		return 0;

	if (user_mode(regs)) {
		send_user_sigtrap(TRAP_HWBKPT);

		/*
		 * ptrace will disable single step unless explicitly
		 * asked to re-enable it. For other clients, it makes
		 * sense to leave it enabled (i.e. rewind the controls
		 * to the active-not-pending state).
		 */
		user_rewind_single_step(current);
	} else {
#ifdef	CONFIG_KPROBES
		if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
			return 0;
#endif
		if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
			return 0;

		pr_warning("Unexpected kernel single-step exception at EL1\n");
		/*
		 * Re-enable stepping since we know that we will be
		 * returning to regs.
		 */
		set_regs_spsr_ss(regs);
	}

	return 0;
}
NOKPROBE_SYMBOL(single_step_handler);

/*
 * Breakpoint handler is re-entrant as another breakpoint can
 * hit within breakpoint handler, especically in kprobes.
 * Use reader/writer locks instead of plain spinlock.
 */
static LIST_HEAD(break_hook);
static DEFINE_SPINLOCK(break_hook_lock);

void register_break_hook(struct break_hook *hook)
{
	spin_lock(&break_hook_lock);
	list_add_rcu(&hook->node, &break_hook);
	spin_unlock(&break_hook_lock);
}

void unregister_break_hook(struct break_hook *hook)
{
	spin_lock(&break_hook_lock);
	list_del_rcu(&hook->node);
	spin_unlock(&break_hook_lock);
	synchronize_rcu();
}

static int call_break_hook(struct pt_regs *regs, unsigned int esr)
{
	struct break_hook *hook;
	int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;

	rcu_read_lock();
	list_for_each_entry_rcu(hook, &break_hook, node)
		if ((esr & hook->esr_mask) == hook->esr_val)
			fn = hook->fn;
	rcu_read_unlock();

	return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
}
NOKPROBE_SYMBOL(call_break_hook);

static int brk_handler(unsigned long addr, unsigned int esr,
		       struct pt_regs *regs)
{
	if (user_mode(regs)) {
		send_user_sigtrap(TRAP_BRKPT);
	}
#ifdef	CONFIG_KPROBES
	else if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
		if (kprobe_breakpoint_handler(regs, esr) != DBG_HOOK_HANDLED)
			return -EFAULT;
	}
#endif
	else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
		pr_warn("Unexpected kernel BRK exception at EL1\n");
		return -EFAULT;
	}

	return 0;
}
NOKPROBE_SYMBOL(brk_handler);

int aarch32_break_handler(struct pt_regs *regs)
{
	u32 arm_instr;
	u16 thumb_instr;
	bool bp = false;
	void __user *pc = (void __user *)instruction_pointer(regs);

	if (!compat_user_mode(regs))
		return -EFAULT;

	if (compat_thumb_mode(regs)) {
		/* get 16-bit Thumb instruction */
		get_user(thumb_instr, (u16 __user *)pc);
		thumb_instr = le16_to_cpu(thumb_instr);
		if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
			/* get second half of 32-bit Thumb-2 instruction */
			get_user(thumb_instr, (u16 __user *)(pc + 2));
			thumb_instr = le16_to_cpu(thumb_instr);
			bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
		} else {
			bp = thumb_instr == AARCH32_BREAK_THUMB;
		}
	} else {
		/* 32-bit ARM instruction */
		get_user(arm_instr, (u32 __user *)pc);
		arm_instr = le32_to_cpu(arm_instr);
		bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
	}

	if (!bp)
		return -EFAULT;

	send_user_sigtrap(TRAP_BRKPT);
	return 0;
}
NOKPROBE_SYMBOL(aarch32_break_handler);

static int __init debug_traps_init(void)
{
	hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
			      TRAP_HWBKPT, "single-step handler");
	hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
			      TRAP_BRKPT, "ptrace BRK handler");
	return 0;
}
arch_initcall(debug_traps_init);

/* Re-enable single step for syscall restarting. */
void user_rewind_single_step(struct task_struct *task)
{
	/*
	 * If single step is active for this thread, then set SPSR.SS
	 * to 1 to avoid returning to the active-pending state.
	 */
	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
		set_regs_spsr_ss(task_pt_regs(task));
}
NOKPROBE_SYMBOL(user_rewind_single_step);

void user_fastforward_single_step(struct task_struct *task)
{
	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
		clear_regs_spsr_ss(task_pt_regs(task));
}

/* Kernel API */
void kernel_enable_single_step(struct pt_regs *regs)
{
	WARN_ON(!irqs_disabled());
	set_regs_spsr_ss(regs);
	mdscr_write(mdscr_read() | DBG_MDSCR_SS);
	enable_debug_monitors(DBG_ACTIVE_EL1);
}
NOKPROBE_SYMBOL(kernel_enable_single_step);

void kernel_disable_single_step(void)
{
	WARN_ON(!irqs_disabled());
	mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
	disable_debug_monitors(DBG_ACTIVE_EL1);
}
NOKPROBE_SYMBOL(kernel_disable_single_step);

int kernel_active_single_step(void)
{
	WARN_ON(!irqs_disabled());
	return mdscr_read() & DBG_MDSCR_SS;
}
NOKPROBE_SYMBOL(kernel_active_single_step);

/* ptrace API */
void user_enable_single_step(struct task_struct *task)
{
	struct thread_info *ti = task_thread_info(task);

	if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
		set_regs_spsr_ss(task_pt_regs(task));
}
NOKPROBE_SYMBOL(user_enable_single_step);

void user_disable_single_step(struct task_struct *task)
{
	clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
}
NOKPROBE_SYMBOL(user_disable_single_step);
Commit	Line	Data
478fcb2c WD	1	/*
	2	* ARMv8 single-step debug support and mdscr context switching.
	3	*
	4	* Copyright (C) 2012 ARM Limited
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License version 2 as
	8	* published by the Free Software Foundation.
	9	*
	10	* This program is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	13	* GNU General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU General Public License
	16	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	17	*
	18	* Author: Will Deacon <will.deacon@arm.com>
	19	*/
	20
	21	#include <linux/cpu.h>
	22	#include <linux/debugfs.h>
	23	#include <linux/hardirq.h>
	24	#include <linux/init.h>
	25	#include <linux/ptrace.h>
2dd0e8d2	26	#include <linux/kprobes.h>
478fcb2c	27	#include <linux/stat.h>
1442b6ed	28	#include <linux/uaccess.h>
478fcb2c	29
3085bb01	30	#include <asm/cpufeature.h>
478fcb2c	31	#include <asm/cputype.h>
3085bb01	32	#include <asm/debug-monitors.h>
478fcb2c WD	33	#include <asm/system_misc.h>
478fcb2c WD	34
478fcb2c WD	35	/* Determine debug architecture. */
	36	u8 debug_monitors_arch(void)
	37	{
28c5dcb2	38	return cpuid_feature_extract_unsigned_field(read_system_reg(SYS_ID_AA64DFR0_EL1),
3085bb01	39	ID_AA64DFR0_DEBUGVER_SHIFT);
478fcb2c WD	40	}
	41
	42	/*
	43	* MDSCR access routines.
	44	*/
	45	static void mdscr_write(u32 mdscr)
	46	{
	47	unsigned long flags;
	48	local_dbg_save(flags);
	49	asm volatile("msr mdscr_el1, %0" :: "r" (mdscr));
	50	local_dbg_restore(flags);
	51	}
44b53f67	52	NOKPROBE_SYMBOL(mdscr_write);
478fcb2c WD	53
	54	static u32 mdscr_read(void)
	55	{
	56	u32 mdscr;
	57	asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr));
	58	return mdscr;
	59	}
44b53f67	60	NOKPROBE_SYMBOL(mdscr_read);
478fcb2c WD	61
	62	/*
	63	* Allow root to disable self-hosted debug from userspace.
	64	* This is useful if you want to connect an external JTAG debugger.
	65	*/
621a5f7a	66	static bool debug_enabled = true;
478fcb2c WD	67
	68	static int create_debug_debugfs_entry(void)
	69	{
	70	debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
	71	return 0;
	72	}
	73	fs_initcall(create_debug_debugfs_entry);
	74
	75	static int __init early_debug_disable(char *buf)
	76	{
621a5f7a	77	debug_enabled = false;
478fcb2c WD	78	return 0;
	79	}
	80
	81	early_param("nodebugmon", early_debug_disable);
	82
	83	/*
	84	* Keep track of debug users on each core.
	85	* The ref counts are per-cpu so we use a local_t type.
	86	*/
1436c1aa CL	87	static DEFINE_PER_CPU(int, mde_ref_count);
1436c1aa CL	88	static DEFINE_PER_CPU(int, kde_ref_count);
478fcb2c	89
6f883d10	90	void enable_debug_monitors(enum dbg_active_el el)
478fcb2c WD	91	{
	92	u32 mdscr, enable = 0;
	93
	94	WARN_ON(preemptible());
	95
1436c1aa	96	if (this_cpu_inc_return(mde_ref_count) == 1)
478fcb2c WD	97	enable = DBG_MDSCR_MDE;
	98
	99	if (el == DBG_ACTIVE_EL1 &&
1436c1aa	100	this_cpu_inc_return(kde_ref_count) == 1)
478fcb2c WD	101	enable \|= DBG_MDSCR_KDE;
	102
	103	if (enable && debug_enabled) {
	104	mdscr = mdscr_read();
	105	mdscr \|= enable;
	106	mdscr_write(mdscr);
	107	}
	108	}
44b53f67	109	NOKPROBE_SYMBOL(enable_debug_monitors);
478fcb2c	110
6f883d10	111	void disable_debug_monitors(enum dbg_active_el el)
478fcb2c WD	112	{
	113	u32 mdscr, disable = 0;
	114
	115	WARN_ON(preemptible());
	116
1436c1aa	117	if (this_cpu_dec_return(mde_ref_count) == 0)
478fcb2c WD	118	disable = ~DBG_MDSCR_MDE;
	119
	120	if (el == DBG_ACTIVE_EL1 &&
1436c1aa	121	this_cpu_dec_return(kde_ref_count) == 0)
478fcb2c WD	122	disable &= ~DBG_MDSCR_KDE;
	123
	124	if (disable) {
	125	mdscr = mdscr_read();
	126	mdscr &= disable;
	127	mdscr_write(mdscr);
	128	}
	129	}
44b53f67	130	NOKPROBE_SYMBOL(disable_debug_monitors);
478fcb2c WD	131
	132	/*
	133	* OS lock clearing.
	134	*/
	135	static void clear_os_lock(void *unused)
	136	{
478fcb2c	137	asm volatile("msr oslar_el1, %0" : : "r" (0));
478fcb2c WD	138	}
478fcb2c WD	139
b8c6453a	140	static int os_lock_notify(struct notifier_block *self,
478fcb2c WD	141	unsigned long action, void *data)
478fcb2c WD	142	{
e56d82a1	143	if ((action & ~CPU_TASKS_FROZEN) == CPU_ONLINE)
499c8150	144	clear_os_lock(NULL);
478fcb2c WD	145	return NOTIFY_OK;
	146	}
	147
b8c6453a	148	static struct notifier_block os_lock_nb = {
478fcb2c WD	149	.notifier_call = os_lock_notify,
	150	};
	151
b8c6453a	152	static int debug_monitors_init(void)
478fcb2c	153	{
4b0b68af SB	154	cpu_notifier_register_begin();
4b0b68af SB	155
478fcb2c	156	/* Clear the OS lock. */
d8ed442a VK	157	on_each_cpu(clear_os_lock, NULL, 1);
d8ed442a VK	158	isb();
478fcb2c WD	159
478fcb2c WD	160	/* Register hotplug handler. */
4b0b68af SB	161	__register_cpu_notifier(&os_lock_nb);
	162
	163	cpu_notifier_register_done();
478fcb2c WD	164	return 0;
	165	}
	166	postcore_initcall(debug_monitors_init);
	167
	168	/*
	169	* Single step API and exception handling.
	170	*/
	171	static void set_regs_spsr_ss(struct pt_regs *regs)
	172	{
6b68e14e	173	regs->pstate \|= DBG_SPSR_SS;
478fcb2c	174	}
44b53f67	175	NOKPROBE_SYMBOL(set_regs_spsr_ss);
478fcb2c WD	176
	177	static void clear_regs_spsr_ss(struct pt_regs *regs)
	178	{
6b68e14e	179	regs->pstate &= ~DBG_SPSR_SS;
478fcb2c	180	}
44b53f67	181	NOKPROBE_SYMBOL(clear_regs_spsr_ss);
478fcb2c	182
ee6214ce SP	183	/* EL1 Single Step Handler hooks */
ee6214ce SP	184	static LIST_HEAD(step_hook);
cf0a2543	185	static DEFINE_SPINLOCK(step_hook_lock);
ee6214ce SP	186
	187	void register_step_hook(struct step_hook *hook)
	188	{
cf0a2543 YS	189	spin_lock(&step_hook_lock);
	190	list_add_rcu(&hook->node, &step_hook);
	191	spin_unlock(&step_hook_lock);
ee6214ce SP	192	}
	193
	194	void unregister_step_hook(struct step_hook *hook)
	195	{
cf0a2543 YS	196	spin_lock(&step_hook_lock);
	197	list_del_rcu(&hook->node);
	198	spin_unlock(&step_hook_lock);
	199	synchronize_rcu();
ee6214ce SP	200	}
	201
	202	/*
95485fdc	203	* Call registered single step handlers
ee6214ce SP	204	* There is no Syndrome info to check for determining the handler.
	205	* So we call all the registered handlers, until the right handler is
	206	* found which returns zero.
	207	*/
	208	static int call_step_hook(struct pt_regs *regs, unsigned int esr)
	209	{
	210	struct step_hook *hook;
	211	int retval = DBG_HOOK_ERROR;
	212
cf0a2543	213	rcu_read_lock();
ee6214ce	214
cf0a2543	215	list_for_each_entry_rcu(hook, &step_hook, node) {
ee6214ce SP	216	retval = hook->fn(regs, esr);
	217	if (retval == DBG_HOOK_HANDLED)
	218	break;
	219	}
	220
cf0a2543	221	rcu_read_unlock();
ee6214ce SP	222
	223	return retval;
	224	}
44b53f67	225	NOKPROBE_SYMBOL(call_step_hook);
ee6214ce	226
e04a28d4 WD	227	static void send_user_sigtrap(int si_code)
	228	{
	229	struct pt_regs *regs = current_pt_regs();
	230	siginfo_t info = {
	231	.si_signo = SIGTRAP,
	232	.si_errno = 0,
	233	.si_code = si_code,
	234	.si_addr = (void __user *)instruction_pointer(regs),
	235	};
	236
	237	if (WARN_ON(!user_mode(regs)))
	238	return;
	239
	240	if (interrupts_enabled(regs))
	241	local_irq_enable();
	242
	243	force_sig_info(SIGTRAP, &info, current);
	244	}
	245
478fcb2c WD	246	static int single_step_handler(unsigned long addr, unsigned int esr,
	247	struct pt_regs *regs)
	248	{
478fcb2c WD	249	/*
	250	* If we are stepping a pending breakpoint, call the hw_breakpoint
	251	* handler first.
	252	*/
	253	if (!reinstall_suspended_bps(regs))
	254	return 0;
	255
	256	if (user_mode(regs)) {
e04a28d4	257	send_user_sigtrap(TRAP_HWBKPT);
478fcb2c WD	258
	259	/*
	260	* ptrace will disable single step unless explicitly
	261	* asked to re-enable it. For other clients, it makes
	262	* sense to leave it enabled (i.e. rewind the controls
	263	* to the active-not-pending state).
	264	*/
	265	user_rewind_single_step(current);
	266	} else {
2dd0e8d2 SP	267	#ifdef CONFIG_KPROBES
	268	if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
	269	return 0;
	270	#endif
ee6214ce SP	271	if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
	272	return 0;
	273
478fcb2c WD	274	pr_warning("Unexpected kernel single-step exception at EL1\n");
	275	/*
	276	* Re-enable stepping since we know that we will be
	277	* returning to regs.
	278	*/
	279	set_regs_spsr_ss(regs);
	280	}
	281
	282	return 0;
	283	}
44b53f67	284	NOKPROBE_SYMBOL(single_step_handler);
478fcb2c	285
ee6214ce SP	286	/*
	287	* Breakpoint handler is re-entrant as another breakpoint can
	288	* hit within breakpoint handler, especically in kprobes.
	289	* Use reader/writer locks instead of plain spinlock.
	290	*/
	291	static LIST_HEAD(break_hook);
62c6c61a	292	static DEFINE_SPINLOCK(break_hook_lock);
ee6214ce SP	293
	294	void register_break_hook(struct break_hook *hook)
	295	{
62c6c61a YS	296	spin_lock(&break_hook_lock);
	297	list_add_rcu(&hook->node, &break_hook);
	298	spin_unlock(&break_hook_lock);
ee6214ce SP	299	}
	300
	301	void unregister_break_hook(struct break_hook *hook)
	302	{
62c6c61a YS	303	spin_lock(&break_hook_lock);
	304	list_del_rcu(&hook->node);
	305	spin_unlock(&break_hook_lock);
	306	synchronize_rcu();
ee6214ce SP	307	}
	308
	309	static int call_break_hook(struct pt_regs *regs, unsigned int esr)
	310	{
	311	struct break_hook *hook;
	312	int (fn)(struct pt_regs regs, unsigned int esr) = NULL;
	313
62c6c61a YS	314	rcu_read_lock();
62c6c61a YS	315	list_for_each_entry_rcu(hook, &break_hook, node)
ee6214ce SP	316	if ((esr & hook->esr_mask) == hook->esr_val)
ee6214ce SP	317	fn = hook->fn;
62c6c61a	318	rcu_read_unlock();
ee6214ce SP	319
	320	return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
	321	}
44b53f67	322	NOKPROBE_SYMBOL(call_break_hook);
ee6214ce	323
1442b6ed WD	324	static int brk_handler(unsigned long addr, unsigned int esr,
	325	struct pt_regs *regs)
	326	{
c878e0cf	327	if (user_mode(regs)) {
e04a28d4	328	send_user_sigtrap(TRAP_BRKPT);
2dd0e8d2 SP	329	}
	330	#ifdef CONFIG_KPROBES
	331	else if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
	332	if (kprobe_breakpoint_handler(regs, esr) != DBG_HOOK_HANDLED)
	333	return -EFAULT;
	334	}
	335	#endif
	336	else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
	337	pr_warn("Unexpected kernel BRK exception at EL1\n");
1442b6ed	338	return -EFAULT;
c878e0cf	339	}
1442b6ed	340
1442b6ed WD	341	return 0;
1442b6ed WD	342	}
44b53f67	343	NOKPROBE_SYMBOL(brk_handler);
1442b6ed WD	344
	345	int aarch32_break_handler(struct pt_regs *regs)
	346	{
2dacab73 ML	347	u32 arm_instr;
2dacab73 ML	348	u16 thumb_instr;
1442b6ed WD	349	bool bp = false;
	350	void __user pc = (void __user )instruction_pointer(regs);
	351
	352	if (!compat_user_mode(regs))
	353	return -EFAULT;
	354
	355	if (compat_thumb_mode(regs)) {
	356	/* get 16-bit Thumb instruction */
2dacab73 ML	357	get_user(thumb_instr, (u16 __user *)pc);
	358	thumb_instr = le16_to_cpu(thumb_instr);
	359	if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
1442b6ed	360	/* get second half of 32-bit Thumb-2 instruction */
2dacab73 ML	361	get_user(thumb_instr, (u16 __user *)(pc + 2));
	362	thumb_instr = le16_to_cpu(thumb_instr);
	363	bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
1442b6ed	364	} else {
2dacab73	365	bp = thumb_instr == AARCH32_BREAK_THUMB;
1442b6ed WD	366	}
	367	} else {
	368	/* 32-bit ARM instruction */
2dacab73 ML	369	get_user(arm_instr, (u32 __user *)pc);
	370	arm_instr = le32_to_cpu(arm_instr);
	371	bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
1442b6ed WD	372	}
	373
	374	if (!bp)
	375	return -EFAULT;
	376
e04a28d4	377	send_user_sigtrap(TRAP_BRKPT);
1442b6ed WD	378	return 0;
1442b6ed WD	379	}
44b53f67	380	NOKPROBE_SYMBOL(aarch32_break_handler);
1442b6ed WD	381
1442b6ed WD	382	static int __init debug_traps_init(void)
478fcb2c WD	383	{
	384	hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
	385	TRAP_HWBKPT, "single-step handler");
1442b6ed WD	386	hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
1442b6ed WD	387	TRAP_BRKPT, "ptrace BRK handler");
478fcb2c WD	388	return 0;
478fcb2c WD	389	}
1442b6ed	390	arch_initcall(debug_traps_init);
478fcb2c WD	391
	392	/* Re-enable single step for syscall restarting. */
	393	void user_rewind_single_step(struct task_struct *task)
	394	{
	395	/*
	396	* If single step is active for this thread, then set SPSR.SS
	397	* to 1 to avoid returning to the active-pending state.
	398	*/
	399	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	400	set_regs_spsr_ss(task_pt_regs(task));
	401	}
44b53f67	402	NOKPROBE_SYMBOL(user_rewind_single_step);
478fcb2c WD	403
	404	void user_fastforward_single_step(struct task_struct *task)
	405	{
	406	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	407	clear_regs_spsr_ss(task_pt_regs(task));
	408	}
	409
	410	/* Kernel API */
	411	void kernel_enable_single_step(struct pt_regs *regs)
	412	{
	413	WARN_ON(!irqs_disabled());
	414	set_regs_spsr_ss(regs);
	415	mdscr_write(mdscr_read() \| DBG_MDSCR_SS);
	416	enable_debug_monitors(DBG_ACTIVE_EL1);
	417	}
44b53f67	418	NOKPROBE_SYMBOL(kernel_enable_single_step);
478fcb2c WD	419
	420	void kernel_disable_single_step(void)
	421	{
	422	WARN_ON(!irqs_disabled());
	423	mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
	424	disable_debug_monitors(DBG_ACTIVE_EL1);
	425	}
44b53f67	426	NOKPROBE_SYMBOL(kernel_disable_single_step);
478fcb2c WD	427
	428	int kernel_active_single_step(void)
	429	{
	430	WARN_ON(!irqs_disabled());
	431	return mdscr_read() & DBG_MDSCR_SS;
	432	}
44b53f67	433	NOKPROBE_SYMBOL(kernel_active_single_step);
478fcb2c WD	434
	435	/* ptrace API */
	436	void user_enable_single_step(struct task_struct *task)
	437	{
107d026a WD	438	struct thread_info *ti = task_thread_info(task);
	439
	440	if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
	441	set_regs_spsr_ss(task_pt_regs(task));
478fcb2c	442	}
44b53f67	443	NOKPROBE_SYMBOL(user_enable_single_step);
478fcb2c WD	444
	445	void user_disable_single_step(struct task_struct *task)
	446	{
	447	clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
	448	}
44b53f67	449	NOKPROBE_SYMBOL(user_disable_single_step);