[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);
}

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

/*
 * 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);
	}
}

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);
	}
}

/*
 * 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();
	local_dbg_enable();

	/* 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)
{
	unsigned long spsr;

	spsr = regs->pstate;
	spsr &= ~DBG_SPSR_SS;
	spsr |= DBG_SPSR_SS;
	regs->pstate = spsr;
}

static void clear_regs_spsr_ss(struct pt_regs *regs)
{
	unsigned long spsr;

	spsr = regs->pstate;
	spsr &= ~DBG_SPSR_SS;
	regs->pstate = spsr;
}

/* 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;
}

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;
}

/*
 * 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;
}

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;
}

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;
}

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));
}

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);
}

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

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

/* ptrace API */
void user_enable_single_step(struct task_struct *task)
{
	set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
	set_regs_spsr_ss(task_pt_regs(task));
}

void user_disable_single_step(struct task_struct *task)
{
	clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
}
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	}
	52
	53	static u32 mdscr_read(void)
	54	{
	55	u32 mdscr;
	56	asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr));
	57	return mdscr;
	58	}
	59
	60	/*
	61	* Allow root to disable self-hosted debug from userspace.
	62	* This is useful if you want to connect an external JTAG debugger.
	63	*/
621a5f7a	64	static bool debug_enabled = true;
478fcb2c WD	65
	66	static int create_debug_debugfs_entry(void)
	67	{
	68	debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
	69	return 0;
	70	}
	71	fs_initcall(create_debug_debugfs_entry);
	72
	73	static int __init early_debug_disable(char *buf)
	74	{
621a5f7a	75	debug_enabled = false;
478fcb2c WD	76	return 0;
	77	}
	78
	79	early_param("nodebugmon", early_debug_disable);
	80
	81	/*
	82	* Keep track of debug users on each core.
	83	* The ref counts are per-cpu so we use a local_t type.
	84	*/
1436c1aa CL	85	static DEFINE_PER_CPU(int, mde_ref_count);
1436c1aa CL	86	static DEFINE_PER_CPU(int, kde_ref_count);
478fcb2c	87
6f883d10	88	void enable_debug_monitors(enum dbg_active_el el)
478fcb2c WD	89	{
	90	u32 mdscr, enable = 0;
	91
	92	WARN_ON(preemptible());
	93
1436c1aa	94	if (this_cpu_inc_return(mde_ref_count) == 1)
478fcb2c WD	95	enable = DBG_MDSCR_MDE;
	96
	97	if (el == DBG_ACTIVE_EL1 &&
1436c1aa	98	this_cpu_inc_return(kde_ref_count) == 1)
478fcb2c WD	99	enable \|= DBG_MDSCR_KDE;
	100
	101	if (enable && debug_enabled) {
	102	mdscr = mdscr_read();
	103	mdscr \|= enable;
	104	mdscr_write(mdscr);
	105	}
	106	}
	107
6f883d10	108	void disable_debug_monitors(enum dbg_active_el el)
478fcb2c WD	109	{
	110	u32 mdscr, disable = 0;
	111
	112	WARN_ON(preemptible());
	113
1436c1aa	114	if (this_cpu_dec_return(mde_ref_count) == 0)
478fcb2c WD	115	disable = ~DBG_MDSCR_MDE;
	116
	117	if (el == DBG_ACTIVE_EL1 &&
1436c1aa	118	this_cpu_dec_return(kde_ref_count) == 0)
478fcb2c WD	119	disable &= ~DBG_MDSCR_KDE;
	120
	121	if (disable) {
	122	mdscr = mdscr_read();
	123	mdscr &= disable;
	124	mdscr_write(mdscr);
	125	}
	126	}
	127
	128	/*
	129	* OS lock clearing.
	130	*/
	131	static void clear_os_lock(void *unused)
	132	{
478fcb2c	133	asm volatile("msr oslar_el1, %0" : : "r" (0));
478fcb2c WD	134	}
478fcb2c WD	135
b8c6453a	136	static int os_lock_notify(struct notifier_block *self,
478fcb2c WD	137	unsigned long action, void *data)
478fcb2c WD	138	{
e56d82a1	139	if ((action & ~CPU_TASKS_FROZEN) == CPU_ONLINE)
499c8150	140	clear_os_lock(NULL);
478fcb2c WD	141	return NOTIFY_OK;
	142	}
	143
b8c6453a	144	static struct notifier_block os_lock_nb = {
478fcb2c WD	145	.notifier_call = os_lock_notify,
	146	};
	147
b8c6453a	148	static int debug_monitors_init(void)
478fcb2c	149	{
4b0b68af SB	150	cpu_notifier_register_begin();
4b0b68af SB	151
478fcb2c	152	/* Clear the OS lock. */
d8ed442a VK	153	on_each_cpu(clear_os_lock, NULL, 1);
	154	isb();
	155	local_dbg_enable();
478fcb2c WD	156
478fcb2c WD	157	/* Register hotplug handler. */
4b0b68af SB	158	__register_cpu_notifier(&os_lock_nb);
	159
	160	cpu_notifier_register_done();
478fcb2c WD	161	return 0;
	162	}
	163	postcore_initcall(debug_monitors_init);
	164
	165	/*
	166	* Single step API and exception handling.
	167	*/
	168	static void set_regs_spsr_ss(struct pt_regs *regs)
	169	{
	170	unsigned long spsr;
	171
	172	spsr = regs->pstate;
	173	spsr &= ~DBG_SPSR_SS;
	174	spsr \|= DBG_SPSR_SS;
	175	regs->pstate = spsr;
	176	}
	177
	178	static void clear_regs_spsr_ss(struct pt_regs *regs)
	179	{
	180	unsigned long spsr;
	181
	182	spsr = regs->pstate;
	183	spsr &= ~DBG_SPSR_SS;
	184	regs->pstate = spsr;
	185	}
	186
ee6214ce SP	187	/* EL1 Single Step Handler hooks */
ee6214ce SP	188	static LIST_HEAD(step_hook);
cf0a2543	189	static DEFINE_SPINLOCK(step_hook_lock);
ee6214ce SP	190
	191	void register_step_hook(struct step_hook *hook)
	192	{
cf0a2543 YS	193	spin_lock(&step_hook_lock);
	194	list_add_rcu(&hook->node, &step_hook);
	195	spin_unlock(&step_hook_lock);
ee6214ce SP	196	}
	197
	198	void unregister_step_hook(struct step_hook *hook)
	199	{
cf0a2543 YS	200	spin_lock(&step_hook_lock);
	201	list_del_rcu(&hook->node);
	202	spin_unlock(&step_hook_lock);
	203	synchronize_rcu();
ee6214ce SP	204	}
	205
	206	/*
95485fdc	207	* Call registered single step handlers
ee6214ce SP	208	* There is no Syndrome info to check for determining the handler.
	209	* So we call all the registered handlers, until the right handler is
	210	* found which returns zero.
	211	*/
	212	static int call_step_hook(struct pt_regs *regs, unsigned int esr)
	213	{
	214	struct step_hook *hook;
	215	int retval = DBG_HOOK_ERROR;
	216
cf0a2543	217	rcu_read_lock();
ee6214ce	218
cf0a2543	219	list_for_each_entry_rcu(hook, &step_hook, node) {
ee6214ce SP	220	retval = hook->fn(regs, esr);
	221	if (retval == DBG_HOOK_HANDLED)
	222	break;
	223	}
	224
cf0a2543	225	rcu_read_unlock();
ee6214ce SP	226
	227	return retval;
	228	}
	229
e04a28d4 WD	230	static void send_user_sigtrap(int si_code)
	231	{
	232	struct pt_regs *regs = current_pt_regs();
	233	siginfo_t info = {
	234	.si_signo = SIGTRAP,
	235	.si_errno = 0,
	236	.si_code = si_code,
	237	.si_addr = (void __user *)instruction_pointer(regs),
	238	};
	239
	240	if (WARN_ON(!user_mode(regs)))
	241	return;
	242
	243	if (interrupts_enabled(regs))
	244	local_irq_enable();
	245
	246	force_sig_info(SIGTRAP, &info, current);
	247	}
	248
478fcb2c WD	249	static int single_step_handler(unsigned long addr, unsigned int esr,
	250	struct pt_regs *regs)
	251	{
478fcb2c WD	252	/*
	253	* If we are stepping a pending breakpoint, call the hw_breakpoint
	254	* handler first.
	255	*/
	256	if (!reinstall_suspended_bps(regs))
	257	return 0;
	258
	259	if (user_mode(regs)) {
e04a28d4	260	send_user_sigtrap(TRAP_HWBKPT);
478fcb2c WD	261
	262	/*
	263	* ptrace will disable single step unless explicitly
	264	* asked to re-enable it. For other clients, it makes
	265	* sense to leave it enabled (i.e. rewind the controls
	266	* to the active-not-pending state).
	267	*/
	268	user_rewind_single_step(current);
	269	} else {
2dd0e8d2 SP	270	#ifdef CONFIG_KPROBES
	271	if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
	272	return 0;
	273	#endif
ee6214ce SP	274	if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
	275	return 0;
	276
478fcb2c WD	277	pr_warning("Unexpected kernel single-step exception at EL1\n");
	278	/*
	279	* Re-enable stepping since we know that we will be
	280	* returning to regs.
	281	*/
	282	set_regs_spsr_ss(regs);
	283	}
	284
	285	return 0;
	286	}
	287
ee6214ce SP	288	/*
	289	* Breakpoint handler is re-entrant as another breakpoint can
	290	* hit within breakpoint handler, especically in kprobes.
	291	* Use reader/writer locks instead of plain spinlock.
	292	*/
	293	static LIST_HEAD(break_hook);
62c6c61a	294	static DEFINE_SPINLOCK(break_hook_lock);
ee6214ce SP	295
	296	void register_break_hook(struct break_hook *hook)
	297	{
62c6c61a YS	298	spin_lock(&break_hook_lock);
	299	list_add_rcu(&hook->node, &break_hook);
	300	spin_unlock(&break_hook_lock);
ee6214ce SP	301	}
	302
	303	void unregister_break_hook(struct break_hook *hook)
	304	{
62c6c61a YS	305	spin_lock(&break_hook_lock);
	306	list_del_rcu(&hook->node);
	307	spin_unlock(&break_hook_lock);
	308	synchronize_rcu();
ee6214ce SP	309	}
	310
	311	static int call_break_hook(struct pt_regs *regs, unsigned int esr)
	312	{
	313	struct break_hook *hook;
	314	int (fn)(struct pt_regs regs, unsigned int esr) = NULL;
	315
62c6c61a YS	316	rcu_read_lock();
62c6c61a YS	317	list_for_each_entry_rcu(hook, &break_hook, node)
ee6214ce SP	318	if ((esr & hook->esr_mask) == hook->esr_val)
ee6214ce SP	319	fn = hook->fn;
62c6c61a	320	rcu_read_unlock();
ee6214ce SP	321
	322	return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
	323	}
	324
1442b6ed WD	325	static int brk_handler(unsigned long addr, unsigned int esr,
	326	struct pt_regs *regs)
	327	{
c878e0cf	328	if (user_mode(regs)) {
e04a28d4	329	send_user_sigtrap(TRAP_BRKPT);
2dd0e8d2 SP	330	}
	331	#ifdef CONFIG_KPROBES
	332	else if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
	333	if (kprobe_breakpoint_handler(regs, esr) != DBG_HOOK_HANDLED)
	334	return -EFAULT;
	335	}
	336	#endif
	337	else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
	338	pr_warn("Unexpected kernel BRK exception at EL1\n");
1442b6ed	339	return -EFAULT;
c878e0cf	340	}
1442b6ed	341
1442b6ed WD	342	return 0;
	343	}
	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;
	379	}
	380
	381	static int __init debug_traps_init(void)
478fcb2c WD	382	{
	383	hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
	384	TRAP_HWBKPT, "single-step handler");
1442b6ed WD	385	hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
1442b6ed WD	386	TRAP_BRKPT, "ptrace BRK handler");
478fcb2c WD	387	return 0;
478fcb2c WD	388	}
1442b6ed	389	arch_initcall(debug_traps_init);
478fcb2c WD	390
	391	/* Re-enable single step for syscall restarting. */
	392	void user_rewind_single_step(struct task_struct *task)
	393	{
	394	/*
	395	* If single step is active for this thread, then set SPSR.SS
	396	* to 1 to avoid returning to the active-pending state.
	397	*/
	398	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	399	set_regs_spsr_ss(task_pt_regs(task));
	400	}
	401
	402	void user_fastforward_single_step(struct task_struct *task)
	403	{
	404	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	405	clear_regs_spsr_ss(task_pt_regs(task));
	406	}
	407
	408	/* Kernel API */
	409	void kernel_enable_single_step(struct pt_regs *regs)
	410	{
	411	WARN_ON(!irqs_disabled());
	412	set_regs_spsr_ss(regs);
	413	mdscr_write(mdscr_read() \| DBG_MDSCR_SS);
	414	enable_debug_monitors(DBG_ACTIVE_EL1);
	415	}
	416
	417	void kernel_disable_single_step(void)
	418	{
	419	WARN_ON(!irqs_disabled());
	420	mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
	421	disable_debug_monitors(DBG_ACTIVE_EL1);
	422	}
	423
	424	int kernel_active_single_step(void)
	425	{
	426	WARN_ON(!irqs_disabled());
	427	return mdscr_read() & DBG_MDSCR_SS;
	428	}
	429
	430	/* ptrace API */
	431	void user_enable_single_step(struct task_struct *task)
	432	{
	433	set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
	434	set_regs_spsr_ss(task_pt_regs(task));
	435	}
	436
	437	void user_disable_single_step(struct task_struct *task)
	438	{
	439	clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
	440	}