[mirror_ubuntu-artful-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 <linux/sched/task_stack.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>
68db0cf1	29	#include <linux/sched/task_stack.h>
478fcb2c	30
3085bb01	31	#include <asm/cpufeature.h>
478fcb2c	32	#include <asm/cputype.h>
3085bb01	33	#include <asm/debug-monitors.h>
478fcb2c WD	34	#include <asm/system_misc.h>
478fcb2c WD	35
478fcb2c WD	36	/* Determine debug architecture. */
	37	u8 debug_monitors_arch(void)
	38	{
28c5dcb2	39	return cpuid_feature_extract_unsigned_field(read_system_reg(SYS_ID_AA64DFR0_EL1),
3085bb01	40	ID_AA64DFR0_DEBUGVER_SHIFT);
478fcb2c WD	41	}
	42
	43	/*
	44	* MDSCR access routines.
	45	*/
	46	static void mdscr_write(u32 mdscr)
	47	{
	48	unsigned long flags;
	49	local_dbg_save(flags);
adf75899	50	write_sysreg(mdscr, mdscr_el1);
478fcb2c WD	51	local_dbg_restore(flags);
478fcb2c WD	52	}
44b53f67	53	NOKPROBE_SYMBOL(mdscr_write);
478fcb2c WD	54
	55	static u32 mdscr_read(void)
	56	{
adf75899	57	return read_sysreg(mdscr_el1);
478fcb2c	58	}
44b53f67	59	NOKPROBE_SYMBOL(mdscr_read);
478fcb2c WD	60
	61	/*
	62	* Allow root to disable self-hosted debug from userspace.
	63	* This is useful if you want to connect an external JTAG debugger.
	64	*/
621a5f7a	65	static bool debug_enabled = true;
478fcb2c WD	66
	67	static int create_debug_debugfs_entry(void)
	68	{
	69	debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
	70	return 0;
	71	}
	72	fs_initcall(create_debug_debugfs_entry);
	73
	74	static int __init early_debug_disable(char *buf)
	75	{
621a5f7a	76	debug_enabled = false;
478fcb2c WD	77	return 0;
	78	}
	79
	80	early_param("nodebugmon", early_debug_disable);
	81
	82	/*
	83	* Keep track of debug users on each core.
	84	* The ref counts are per-cpu so we use a local_t type.
	85	*/
1436c1aa CL	86	static DEFINE_PER_CPU(int, mde_ref_count);
1436c1aa CL	87	static DEFINE_PER_CPU(int, kde_ref_count);
478fcb2c	88
6f883d10	89	void enable_debug_monitors(enum dbg_active_el el)
478fcb2c WD	90	{
	91	u32 mdscr, enable = 0;
	92
	93	WARN_ON(preemptible());
	94
1436c1aa	95	if (this_cpu_inc_return(mde_ref_count) == 1)
478fcb2c WD	96	enable = DBG_MDSCR_MDE;
	97
	98	if (el == DBG_ACTIVE_EL1 &&
1436c1aa	99	this_cpu_inc_return(kde_ref_count) == 1)
478fcb2c WD	100	enable \|= DBG_MDSCR_KDE;
	101
	102	if (enable && debug_enabled) {
	103	mdscr = mdscr_read();
	104	mdscr \|= enable;
	105	mdscr_write(mdscr);
	106	}
	107	}
44b53f67	108	NOKPROBE_SYMBOL(enable_debug_monitors);
478fcb2c	109
6f883d10	110	void disable_debug_monitors(enum dbg_active_el el)
478fcb2c WD	111	{
	112	u32 mdscr, disable = 0;
	113
	114	WARN_ON(preemptible());
	115
1436c1aa	116	if (this_cpu_dec_return(mde_ref_count) == 0)
478fcb2c WD	117	disable = ~DBG_MDSCR_MDE;
	118
	119	if (el == DBG_ACTIVE_EL1 &&
1436c1aa	120	this_cpu_dec_return(kde_ref_count) == 0)
478fcb2c WD	121	disable &= ~DBG_MDSCR_KDE;
	122
	123	if (disable) {
	124	mdscr = mdscr_read();
	125	mdscr &= disable;
	126	mdscr_write(mdscr);
	127	}
	128	}
44b53f67	129	NOKPROBE_SYMBOL(disable_debug_monitors);
478fcb2c WD	130
	131	/*
	132	* OS lock clearing.
	133	*/
e937dd57	134	static int clear_os_lock(unsigned int cpu)
478fcb2c	135	{
adf75899	136	write_sysreg(0, oslar_el1);
e937dd57 WD	137	isb();
e937dd57 WD	138	return 0;
478fcb2c WD	139	}
478fcb2c WD	140
b8c6453a	141	static int debug_monitors_init(void)
478fcb2c	142	{
e937dd57	143	return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
73c1b41e	144	"arm64/debug_monitors:starting",
e937dd57	145	clear_os_lock, NULL);
478fcb2c WD	146	}
	147	postcore_initcall(debug_monitors_init);
	148
	149	/*
	150	* Single step API and exception handling.
	151	*/
	152	static void set_regs_spsr_ss(struct pt_regs *regs)
	153	{
6b68e14e	154	regs->pstate \|= DBG_SPSR_SS;
478fcb2c	155	}
44b53f67	156	NOKPROBE_SYMBOL(set_regs_spsr_ss);
478fcb2c WD	157
	158	static void clear_regs_spsr_ss(struct pt_regs *regs)
	159	{
6b68e14e	160	regs->pstate &= ~DBG_SPSR_SS;
478fcb2c	161	}
44b53f67	162	NOKPROBE_SYMBOL(clear_regs_spsr_ss);
478fcb2c	163
ee6214ce SP	164	/* EL1 Single Step Handler hooks */
ee6214ce SP	165	static LIST_HEAD(step_hook);
cf0a2543	166	static DEFINE_SPINLOCK(step_hook_lock);
ee6214ce SP	167
	168	void register_step_hook(struct step_hook *hook)
	169	{
cf0a2543 YS	170	spin_lock(&step_hook_lock);
	171	list_add_rcu(&hook->node, &step_hook);
	172	spin_unlock(&step_hook_lock);
ee6214ce SP	173	}
	174
	175	void unregister_step_hook(struct step_hook *hook)
	176	{
cf0a2543 YS	177	spin_lock(&step_hook_lock);
	178	list_del_rcu(&hook->node);
	179	spin_unlock(&step_hook_lock);
	180	synchronize_rcu();
ee6214ce SP	181	}
	182
	183	/*
95485fdc	184	* Call registered single step handlers
ee6214ce SP	185	* There is no Syndrome info to check for determining the handler.
	186	* So we call all the registered handlers, until the right handler is
	187	* found which returns zero.
	188	*/
	189	static int call_step_hook(struct pt_regs *regs, unsigned int esr)
	190	{
	191	struct step_hook *hook;
	192	int retval = DBG_HOOK_ERROR;
	193
cf0a2543	194	rcu_read_lock();
ee6214ce	195
cf0a2543	196	list_for_each_entry_rcu(hook, &step_hook, node) {
ee6214ce SP	197	retval = hook->fn(regs, esr);
	198	if (retval == DBG_HOOK_HANDLED)
	199	break;
	200	}
	201
cf0a2543	202	rcu_read_unlock();
ee6214ce SP	203
	204	return retval;
	205	}
44b53f67	206	NOKPROBE_SYMBOL(call_step_hook);
ee6214ce	207
e04a28d4 WD	208	static void send_user_sigtrap(int si_code)
	209	{
	210	struct pt_regs *regs = current_pt_regs();
	211	siginfo_t info = {
	212	.si_signo = SIGTRAP,
	213	.si_errno = 0,
	214	.si_code = si_code,
	215	.si_addr = (void __user *)instruction_pointer(regs),
	216	};
	217
	218	if (WARN_ON(!user_mode(regs)))
	219	return;
	220
	221	if (interrupts_enabled(regs))
	222	local_irq_enable();
	223
	224	force_sig_info(SIGTRAP, &info, current);
	225	}
	226
478fcb2c WD	227	static int single_step_handler(unsigned long addr, unsigned int esr,
	228	struct pt_regs *regs)
	229	{
3fb69640 PA	230	bool handler_found = false;
3fb69640 PA	231
478fcb2c WD	232	/*
	233	* If we are stepping a pending breakpoint, call the hw_breakpoint
	234	* handler first.
	235	*/
	236	if (!reinstall_suspended_bps(regs))
	237	return 0;
	238
3fb69640 PA	239	#ifdef CONFIG_KPROBES
	240	if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
	241	handler_found = true;
	242	#endif
	243	if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
	244	handler_found = true;
	245
	246	if (!handler_found && user_mode(regs)) {
adeb68ef	247	send_user_sigtrap(TRAP_TRACE);
478fcb2c WD	248
	249	/*
	250	* ptrace will disable single step unless explicitly
	251	* asked to re-enable it. For other clients, it makes
	252	* sense to leave it enabled (i.e. rewind the controls
	253	* to the active-not-pending state).
	254	*/
	255	user_rewind_single_step(current);
3fb69640 PA	256	} else if (!handler_found) {
3fb69640 PA	257	pr_warn("Unexpected kernel single-step exception at EL1\n");
478fcb2c WD	258	/*
	259	* Re-enable stepping since we know that we will be
	260	* returning to regs.
	261	*/
	262	set_regs_spsr_ss(regs);
	263	}
	264
	265	return 0;
	266	}
44b53f67	267	NOKPROBE_SYMBOL(single_step_handler);
478fcb2c	268
ee6214ce SP	269	/*
	270	* Breakpoint handler is re-entrant as another breakpoint can
	271	* hit within breakpoint handler, especically in kprobes.
	272	* Use reader/writer locks instead of plain spinlock.
	273	*/
	274	static LIST_HEAD(break_hook);
62c6c61a	275	static DEFINE_SPINLOCK(break_hook_lock);
ee6214ce SP	276
	277	void register_break_hook(struct break_hook *hook)
	278	{
62c6c61a YS	279	spin_lock(&break_hook_lock);
	280	list_add_rcu(&hook->node, &break_hook);
	281	spin_unlock(&break_hook_lock);
ee6214ce SP	282	}
	283
	284	void unregister_break_hook(struct break_hook *hook)
	285	{
62c6c61a YS	286	spin_lock(&break_hook_lock);
	287	list_del_rcu(&hook->node);
	288	spin_unlock(&break_hook_lock);
	289	synchronize_rcu();
ee6214ce SP	290	}
	291
	292	static int call_break_hook(struct pt_regs *regs, unsigned int esr)
	293	{
	294	struct break_hook *hook;
	295	int (fn)(struct pt_regs regs, unsigned int esr) = NULL;
	296
62c6c61a YS	297	rcu_read_lock();
62c6c61a YS	298	list_for_each_entry_rcu(hook, &break_hook, node)
ee6214ce SP	299	if ((esr & hook->esr_mask) == hook->esr_val)
ee6214ce SP	300	fn = hook->fn;
62c6c61a	301	rcu_read_unlock();
ee6214ce SP	302
	303	return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
	304	}
44b53f67	305	NOKPROBE_SYMBOL(call_break_hook);
ee6214ce	306
1442b6ed WD	307	static int brk_handler(unsigned long addr, unsigned int esr,
	308	struct pt_regs *regs)
	309	{
53d07e21 PA	310	bool handler_found = false;
53d07e21 PA	311
2dd0e8d2	312	#ifdef CONFIG_KPROBES
53d07e21 PA	313	if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
	314	if (kprobe_breakpoint_handler(regs, esr) == DBG_HOOK_HANDLED)
	315	handler_found = true;
2dd0e8d2 SP	316	}
2dd0e8d2 SP	317	#endif
53d07e21 PA	318	if (!handler_found && call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
	319	handler_found = true;
	320
	321	if (!handler_found && user_mode(regs)) {
	322	send_user_sigtrap(TRAP_BRKPT);
	323	} else if (!handler_found) {
2dd0e8d2	324	pr_warn("Unexpected kernel BRK exception at EL1\n");
1442b6ed	325	return -EFAULT;
c878e0cf	326	}
1442b6ed	327
1442b6ed WD	328	return 0;
1442b6ed WD	329	}
44b53f67	330	NOKPROBE_SYMBOL(brk_handler);
1442b6ed WD	331
	332	int aarch32_break_handler(struct pt_regs *regs)
	333	{
2dacab73 ML	334	u32 arm_instr;
2dacab73 ML	335	u16 thumb_instr;
1442b6ed WD	336	bool bp = false;
	337	void __user pc = (void __user )instruction_pointer(regs);
	338
	339	if (!compat_user_mode(regs))
	340	return -EFAULT;
	341
	342	if (compat_thumb_mode(regs)) {
	343	/* get 16-bit Thumb instruction */
2dacab73 ML	344	get_user(thumb_instr, (u16 __user *)pc);
	345	thumb_instr = le16_to_cpu(thumb_instr);
	346	if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
1442b6ed	347	/* get second half of 32-bit Thumb-2 instruction */
2dacab73 ML	348	get_user(thumb_instr, (u16 __user *)(pc + 2));
	349	thumb_instr = le16_to_cpu(thumb_instr);
	350	bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
1442b6ed	351	} else {
2dacab73	352	bp = thumb_instr == AARCH32_BREAK_THUMB;
1442b6ed WD	353	}
	354	} else {
	355	/* 32-bit ARM instruction */
2dacab73 ML	356	get_user(arm_instr, (u32 __user *)pc);
	357	arm_instr = le32_to_cpu(arm_instr);
	358	bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
1442b6ed WD	359	}
	360
	361	if (!bp)
	362	return -EFAULT;
	363
e04a28d4	364	send_user_sigtrap(TRAP_BRKPT);
1442b6ed WD	365	return 0;
1442b6ed WD	366	}
44b53f67	367	NOKPROBE_SYMBOL(aarch32_break_handler);
1442b6ed WD	368
1442b6ed WD	369	static int __init debug_traps_init(void)
478fcb2c WD	370	{
478fcb2c WD	371	hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
adeb68ef	372	TRAP_TRACE, "single-step handler");
1442b6ed WD	373	hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
1442b6ed WD	374	TRAP_BRKPT, "ptrace BRK handler");
478fcb2c WD	375	return 0;
478fcb2c WD	376	}
1442b6ed	377	arch_initcall(debug_traps_init);
478fcb2c WD	378
	379	/* Re-enable single step for syscall restarting. */
	380	void user_rewind_single_step(struct task_struct *task)
	381	{
	382	/*
	383	* If single step is active for this thread, then set SPSR.SS
	384	* to 1 to avoid returning to the active-pending state.
	385	*/
	386	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	387	set_regs_spsr_ss(task_pt_regs(task));
	388	}
44b53f67	389	NOKPROBE_SYMBOL(user_rewind_single_step);
478fcb2c WD	390
	391	void user_fastforward_single_step(struct task_struct *task)
	392	{
	393	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	394	clear_regs_spsr_ss(task_pt_regs(task));
	395	}
	396
	397	/* Kernel API */
	398	void kernel_enable_single_step(struct pt_regs *regs)
	399	{
	400	WARN_ON(!irqs_disabled());
	401	set_regs_spsr_ss(regs);
	402	mdscr_write(mdscr_read() \| DBG_MDSCR_SS);
	403	enable_debug_monitors(DBG_ACTIVE_EL1);
	404	}
44b53f67	405	NOKPROBE_SYMBOL(kernel_enable_single_step);
478fcb2c WD	406
	407	void kernel_disable_single_step(void)
	408	{
	409	WARN_ON(!irqs_disabled());
	410	mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
	411	disable_debug_monitors(DBG_ACTIVE_EL1);
	412	}
44b53f67	413	NOKPROBE_SYMBOL(kernel_disable_single_step);
478fcb2c WD	414
	415	int kernel_active_single_step(void)
	416	{
	417	WARN_ON(!irqs_disabled());
	418	return mdscr_read() & DBG_MDSCR_SS;
	419	}
44b53f67	420	NOKPROBE_SYMBOL(kernel_active_single_step);
478fcb2c WD	421
	422	/* ptrace API */
	423	void user_enable_single_step(struct task_struct *task)
	424	{
3a402a70 WD	425	struct thread_info *ti = task_thread_info(task);
	426
	427	if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
	428	set_regs_spsr_ss(task_pt_regs(task));
478fcb2c	429	}
44b53f67	430	NOKPROBE_SYMBOL(user_enable_single_step);
478fcb2c WD	431
	432	void user_disable_single_step(struct task_struct *task)
	433	{
	434	clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
	435	}
44b53f67	436	NOKPROBE_SYMBOL(user_disable_single_step);