[mirror_ubuntu-zesty-kernel.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);
	write_sysreg(mdscr, mdscr_el1);
	local_dbg_restore(flags);
}
NOKPROBE_SYMBOL(mdscr_write);

static u32 mdscr_read(void)
{
	return read_sysreg(mdscr_el1);
}
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 int clear_os_lock(unsigned int cpu)
{
	write_sysreg(0, oslar_el1);
	isb();
	return 0;
}

static int debug_monitors_init(void)
{
	return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
				 "arm64/debug_monitors:starting",
				 clear_os_lock, NULL);
}
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)
{
	bool handler_found = false;

	/*
	 * If we are stepping a pending breakpoint, call the hw_breakpoint
	 * handler first.
	 */
	if (!reinstall_suspended_bps(regs))
		return 0;

#ifdef	CONFIG_KPROBES
	if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
		handler_found = true;
#endif
	if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
		handler_found = true;

	if (!handler_found && user_mode(regs)) {
		send_user_sigtrap(TRAP_TRACE);

		/*
		 * 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 if (!handler_found) {
		pr_warn("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)
{
	bool handler_found = false;

#ifdef	CONFIG_KPROBES
	if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
		if (kprobe_breakpoint_handler(regs, esr) == DBG_HOOK_HANDLED)
			handler_found = true;
	}
#endif
	if (!handler_found && call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
		handler_found = true;

	if (!handler_found && user_mode(regs)) {
		send_user_sigtrap(TRAP_BRKPT);
	} else if (!handler_found) {
		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_TRACE, "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);
adf75899	49	write_sysreg(mdscr, mdscr_el1);
478fcb2c WD	50	local_dbg_restore(flags);
478fcb2c WD	51	}
44b53f67	52	NOKPROBE_SYMBOL(mdscr_write);
478fcb2c WD	53
	54	static u32 mdscr_read(void)
	55	{
adf75899	56	return read_sysreg(mdscr_el1);
478fcb2c	57	}
44b53f67	58	NOKPROBE_SYMBOL(mdscr_read);
478fcb2c WD	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	}
44b53f67	107	NOKPROBE_SYMBOL(enable_debug_monitors);
478fcb2c	108
6f883d10	109	void disable_debug_monitors(enum dbg_active_el el)
478fcb2c WD	110	{
	111	u32 mdscr, disable = 0;
	112
	113	WARN_ON(preemptible());
	114
1436c1aa	115	if (this_cpu_dec_return(mde_ref_count) == 0)
478fcb2c WD	116	disable = ~DBG_MDSCR_MDE;
	117
	118	if (el == DBG_ACTIVE_EL1 &&
1436c1aa	119	this_cpu_dec_return(kde_ref_count) == 0)
478fcb2c WD	120	disable &= ~DBG_MDSCR_KDE;
	121
	122	if (disable) {
	123	mdscr = mdscr_read();
	124	mdscr &= disable;
	125	mdscr_write(mdscr);
	126	}
	127	}
44b53f67	128	NOKPROBE_SYMBOL(disable_debug_monitors);
478fcb2c WD	129
	130	/*
	131	* OS lock clearing.
	132	*/
e937dd57	133	static int clear_os_lock(unsigned int cpu)
478fcb2c	134	{
adf75899	135	write_sysreg(0, oslar_el1);
e937dd57 WD	136	isb();
e937dd57 WD	137	return 0;
478fcb2c WD	138	}
478fcb2c WD	139
b8c6453a	140	static int debug_monitors_init(void)
478fcb2c	141	{
e937dd57	142	return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
73c1b41e	143	"arm64/debug_monitors:starting",
e937dd57	144	clear_os_lock, NULL);
478fcb2c WD	145	}
	146	postcore_initcall(debug_monitors_init);
	147
	148	/*
	149	* Single step API and exception handling.
	150	*/
	151	static void set_regs_spsr_ss(struct pt_regs *regs)
	152	{
6b68e14e	153	regs->pstate \|= DBG_SPSR_SS;
478fcb2c	154	}
44b53f67	155	NOKPROBE_SYMBOL(set_regs_spsr_ss);
478fcb2c WD	156
	157	static void clear_regs_spsr_ss(struct pt_regs *regs)
	158	{
6b68e14e	159	regs->pstate &= ~DBG_SPSR_SS;
478fcb2c	160	}
44b53f67	161	NOKPROBE_SYMBOL(clear_regs_spsr_ss);
478fcb2c	162
ee6214ce SP	163	/* EL1 Single Step Handler hooks */
ee6214ce SP	164	static LIST_HEAD(step_hook);
cf0a2543	165	static DEFINE_SPINLOCK(step_hook_lock);
ee6214ce SP	166
	167	void register_step_hook(struct step_hook *hook)
	168	{
cf0a2543 YS	169	spin_lock(&step_hook_lock);
	170	list_add_rcu(&hook->node, &step_hook);
	171	spin_unlock(&step_hook_lock);
ee6214ce SP	172	}
	173
	174	void unregister_step_hook(struct step_hook *hook)
	175	{
cf0a2543 YS	176	spin_lock(&step_hook_lock);
	177	list_del_rcu(&hook->node);
	178	spin_unlock(&step_hook_lock);
	179	synchronize_rcu();
ee6214ce SP	180	}
	181
	182	/*
95485fdc	183	* Call registered single step handlers
ee6214ce SP	184	* There is no Syndrome info to check for determining the handler.
	185	* So we call all the registered handlers, until the right handler is
	186	* found which returns zero.
	187	*/
	188	static int call_step_hook(struct pt_regs *regs, unsigned int esr)
	189	{
	190	struct step_hook *hook;
	191	int retval = DBG_HOOK_ERROR;
	192
cf0a2543	193	rcu_read_lock();
ee6214ce	194
cf0a2543	195	list_for_each_entry_rcu(hook, &step_hook, node) {
ee6214ce SP	196	retval = hook->fn(regs, esr);
	197	if (retval == DBG_HOOK_HANDLED)
	198	break;
	199	}
	200
cf0a2543	201	rcu_read_unlock();
ee6214ce SP	202
	203	return retval;
	204	}
44b53f67	205	NOKPROBE_SYMBOL(call_step_hook);
ee6214ce	206
e04a28d4 WD	207	static void send_user_sigtrap(int si_code)
	208	{
	209	struct pt_regs *regs = current_pt_regs();
	210	siginfo_t info = {
	211	.si_signo = SIGTRAP,
	212	.si_errno = 0,
	213	.si_code = si_code,
	214	.si_addr = (void __user *)instruction_pointer(regs),
	215	};
	216
	217	if (WARN_ON(!user_mode(regs)))
	218	return;
	219
	220	if (interrupts_enabled(regs))
	221	local_irq_enable();
	222
	223	force_sig_info(SIGTRAP, &info, current);
	224	}
	225
478fcb2c WD	226	static int single_step_handler(unsigned long addr, unsigned int esr,
	227	struct pt_regs *regs)
	228	{
3fb69640 PA	229	bool handler_found = false;
3fb69640 PA	230
478fcb2c WD	231	/*
	232	* If we are stepping a pending breakpoint, call the hw_breakpoint
	233	* handler first.
	234	*/
	235	if (!reinstall_suspended_bps(regs))
	236	return 0;
	237
3fb69640 PA	238	#ifdef CONFIG_KPROBES
	239	if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
	240	handler_found = true;
	241	#endif
	242	if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
	243	handler_found = true;
	244
	245	if (!handler_found && user_mode(regs)) {
adeb68ef	246	send_user_sigtrap(TRAP_TRACE);
478fcb2c WD	247
	248	/*
	249	* ptrace will disable single step unless explicitly
	250	* asked to re-enable it. For other clients, it makes
	251	* sense to leave it enabled (i.e. rewind the controls
	252	* to the active-not-pending state).
	253	*/
	254	user_rewind_single_step(current);
3fb69640 PA	255	} else if (!handler_found) {
3fb69640 PA	256	pr_warn("Unexpected kernel single-step exception at EL1\n");
478fcb2c WD	257	/*
	258	* Re-enable stepping since we know that we will be
	259	* returning to regs.
	260	*/
	261	set_regs_spsr_ss(regs);
	262	}
	263
	264	return 0;
	265	}
44b53f67	266	NOKPROBE_SYMBOL(single_step_handler);
478fcb2c	267
ee6214ce SP	268	/*
	269	* Breakpoint handler is re-entrant as another breakpoint can
	270	* hit within breakpoint handler, especically in kprobes.
	271	* Use reader/writer locks instead of plain spinlock.
	272	*/
	273	static LIST_HEAD(break_hook);
62c6c61a	274	static DEFINE_SPINLOCK(break_hook_lock);
ee6214ce SP	275
	276	void register_break_hook(struct break_hook *hook)
	277	{
62c6c61a YS	278	spin_lock(&break_hook_lock);
	279	list_add_rcu(&hook->node, &break_hook);
	280	spin_unlock(&break_hook_lock);
ee6214ce SP	281	}
	282
	283	void unregister_break_hook(struct break_hook *hook)
	284	{
62c6c61a YS	285	spin_lock(&break_hook_lock);
	286	list_del_rcu(&hook->node);
	287	spin_unlock(&break_hook_lock);
	288	synchronize_rcu();
ee6214ce SP	289	}
	290
	291	static int call_break_hook(struct pt_regs *regs, unsigned int esr)
	292	{
	293	struct break_hook *hook;
	294	int (fn)(struct pt_regs regs, unsigned int esr) = NULL;
	295
62c6c61a YS	296	rcu_read_lock();
62c6c61a YS	297	list_for_each_entry_rcu(hook, &break_hook, node)
ee6214ce SP	298	if ((esr & hook->esr_mask) == hook->esr_val)
ee6214ce SP	299	fn = hook->fn;
62c6c61a	300	rcu_read_unlock();
ee6214ce SP	301
	302	return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
	303	}
44b53f67	304	NOKPROBE_SYMBOL(call_break_hook);
ee6214ce	305
1442b6ed WD	306	static int brk_handler(unsigned long addr, unsigned int esr,
	307	struct pt_regs *regs)
	308	{
53d07e21 PA	309	bool handler_found = false;
53d07e21 PA	310
2dd0e8d2	311	#ifdef CONFIG_KPROBES
53d07e21 PA	312	if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
	313	if (kprobe_breakpoint_handler(regs, esr) == DBG_HOOK_HANDLED)
	314	handler_found = true;
2dd0e8d2 SP	315	}
2dd0e8d2 SP	316	#endif
53d07e21 PA	317	if (!handler_found && call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
	318	handler_found = true;
	319
	320	if (!handler_found && user_mode(regs)) {
	321	send_user_sigtrap(TRAP_BRKPT);
	322	} else if (!handler_found) {
2dd0e8d2	323	pr_warn("Unexpected kernel BRK exception at EL1\n");
1442b6ed	324	return -EFAULT;
c878e0cf	325	}
1442b6ed	326
1442b6ed WD	327	return 0;
1442b6ed WD	328	}
44b53f67	329	NOKPROBE_SYMBOL(brk_handler);
1442b6ed WD	330
	331	int aarch32_break_handler(struct pt_regs *regs)
	332	{
2dacab73 ML	333	u32 arm_instr;
2dacab73 ML	334	u16 thumb_instr;
1442b6ed WD	335	bool bp = false;
	336	void __user pc = (void __user )instruction_pointer(regs);
	337
	338	if (!compat_user_mode(regs))
	339	return -EFAULT;
	340
	341	if (compat_thumb_mode(regs)) {
	342	/* get 16-bit Thumb instruction */
2dacab73 ML	343	get_user(thumb_instr, (u16 __user *)pc);
	344	thumb_instr = le16_to_cpu(thumb_instr);
	345	if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
1442b6ed	346	/* get second half of 32-bit Thumb-2 instruction */
2dacab73 ML	347	get_user(thumb_instr, (u16 __user *)(pc + 2));
	348	thumb_instr = le16_to_cpu(thumb_instr);
	349	bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
1442b6ed	350	} else {
2dacab73	351	bp = thumb_instr == AARCH32_BREAK_THUMB;
1442b6ed WD	352	}
	353	} else {
	354	/* 32-bit ARM instruction */
2dacab73 ML	355	get_user(arm_instr, (u32 __user *)pc);
	356	arm_instr = le32_to_cpu(arm_instr);
	357	bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
1442b6ed WD	358	}
	359
	360	if (!bp)
	361	return -EFAULT;
	362
e04a28d4	363	send_user_sigtrap(TRAP_BRKPT);
1442b6ed WD	364	return 0;
1442b6ed WD	365	}
44b53f67	366	NOKPROBE_SYMBOL(aarch32_break_handler);
1442b6ed WD	367
1442b6ed WD	368	static int __init debug_traps_init(void)
478fcb2c WD	369	{
478fcb2c WD	370	hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
adeb68ef	371	TRAP_TRACE, "single-step handler");
1442b6ed WD	372	hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
1442b6ed WD	373	TRAP_BRKPT, "ptrace BRK handler");
478fcb2c WD	374	return 0;
478fcb2c WD	375	}
1442b6ed	376	arch_initcall(debug_traps_init);
478fcb2c WD	377
	378	/* Re-enable single step for syscall restarting. */
	379	void user_rewind_single_step(struct task_struct *task)
	380	{
	381	/*
	382	* If single step is active for this thread, then set SPSR.SS
	383	* to 1 to avoid returning to the active-pending state.
	384	*/
	385	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	386	set_regs_spsr_ss(task_pt_regs(task));
	387	}
44b53f67	388	NOKPROBE_SYMBOL(user_rewind_single_step);
478fcb2c WD	389
	390	void user_fastforward_single_step(struct task_struct *task)
	391	{
	392	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	393	clear_regs_spsr_ss(task_pt_regs(task));
	394	}
	395
	396	/* Kernel API */
	397	void kernel_enable_single_step(struct pt_regs *regs)
	398	{
	399	WARN_ON(!irqs_disabled());
	400	set_regs_spsr_ss(regs);
	401	mdscr_write(mdscr_read() \| DBG_MDSCR_SS);
	402	enable_debug_monitors(DBG_ACTIVE_EL1);
	403	}
44b53f67	404	NOKPROBE_SYMBOL(kernel_enable_single_step);
478fcb2c WD	405
	406	void kernel_disable_single_step(void)
	407	{
	408	WARN_ON(!irqs_disabled());
	409	mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
	410	disable_debug_monitors(DBG_ACTIVE_EL1);
	411	}
44b53f67	412	NOKPROBE_SYMBOL(kernel_disable_single_step);
478fcb2c WD	413
	414	int kernel_active_single_step(void)
	415	{
	416	WARN_ON(!irqs_disabled());
	417	return mdscr_read() & DBG_MDSCR_SS;
	418	}
44b53f67	419	NOKPROBE_SYMBOL(kernel_active_single_step);
478fcb2c WD	420
	421	/* ptrace API */
	422	void user_enable_single_step(struct task_struct *task)
	423	{
3a402a70 WD	424	struct thread_info *ti = task_thread_info(task);
	425
	426	if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
	427	set_regs_spsr_ss(task_pt_regs(task));
478fcb2c	428	}
44b53f67	429	NOKPROBE_SYMBOL(user_enable_single_step);
478fcb2c WD	430
	431	void user_disable_single_step(struct task_struct *task)
	432	{
	433	clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
	434	}
44b53f67	435	NOKPROBE_SYMBOL(user_disable_single_step);