[mirror_ubuntu-bionic-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/daifflags.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_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1),
						ID_AA64DFR0_DEBUGVER_SHIFT);
}

/*
 * MDSCR access routines.
 */
static void mdscr_write(u32 mdscr)
{
	unsigned long flags;
	flags = local_daif_save();
	write_sysreg(mdscr, mdscr_el1);
	local_daif_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, osdlr_el1);
	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 */
		__le16 instr;
		get_user(instr, (__le16 __user *)pc);
		thumb_instr = le16_to_cpu(instr);
		if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
			/* get second half of 32-bit Thumb-2 instruction */
			get_user(instr, (__le16 __user *)(pc + 2));
			thumb_instr = le16_to_cpu(instr);
			bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
		} else {
			bp = thumb_instr == AARCH32_BREAK_THUMB;
		}
	} else {
		/* 32-bit ARM instruction */
		__le32 instr;
		get_user(instr, (__le32 __user *)pc);
		arm_instr = le32_to_cpu(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>
65be7a1b	33	#include <asm/daifflags.h>
3085bb01	34	#include <asm/debug-monitors.h>
478fcb2c WD	35	#include <asm/system_misc.h>
478fcb2c WD	36
478fcb2c WD	37	/* Determine debug architecture. */
	38	u8 debug_monitors_arch(void)
	39	{
46823dd1	40	return cpuid_feature_extract_unsigned_field(read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1),
3085bb01	41	ID_AA64DFR0_DEBUGVER_SHIFT);
478fcb2c WD	42	}
	43
	44	/*
	45	* MDSCR access routines.
	46	*/
	47	static void mdscr_write(u32 mdscr)
	48	{
	49	unsigned long flags;
65be7a1b	50	flags = local_daif_save();
adf75899	51	write_sysreg(mdscr, mdscr_el1);
65be7a1b	52	local_daif_restore(flags);
478fcb2c	53	}
44b53f67	54	NOKPROBE_SYMBOL(mdscr_write);
478fcb2c WD	55
	56	static u32 mdscr_read(void)
	57	{
adf75899	58	return read_sysreg(mdscr_el1);
478fcb2c	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	*/
e937dd57	135	static int clear_os_lock(unsigned int cpu)
478fcb2c	136	{
d971ce33	137	write_sysreg(0, osdlr_el1);
adf75899	138	write_sysreg(0, oslar_el1);
e937dd57 WD	139	isb();
e937dd57 WD	140	return 0;
478fcb2c WD	141	}
478fcb2c WD	142
b8c6453a	143	static int debug_monitors_init(void)
478fcb2c	144	{
e937dd57	145	return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
73c1b41e	146	"arm64/debug_monitors:starting",
e937dd57	147	clear_os_lock, NULL);
478fcb2c WD	148	}
	149	postcore_initcall(debug_monitors_init);
	150
	151	/*
	152	* Single step API and exception handling.
	153	*/
	154	static void set_regs_spsr_ss(struct pt_regs *regs)
	155	{
6b68e14e	156	regs->pstate \|= DBG_SPSR_SS;
478fcb2c	157	}
44b53f67	158	NOKPROBE_SYMBOL(set_regs_spsr_ss);
478fcb2c WD	159
	160	static void clear_regs_spsr_ss(struct pt_regs *regs)
	161	{
6b68e14e	162	regs->pstate &= ~DBG_SPSR_SS;
478fcb2c	163	}
44b53f67	164	NOKPROBE_SYMBOL(clear_regs_spsr_ss);
478fcb2c	165
ee6214ce SP	166	/* EL1 Single Step Handler hooks */
ee6214ce SP	167	static LIST_HEAD(step_hook);
cf0a2543	168	static DEFINE_SPINLOCK(step_hook_lock);
ee6214ce SP	169
	170	void register_step_hook(struct step_hook *hook)
	171	{
cf0a2543 YS	172	spin_lock(&step_hook_lock);
	173	list_add_rcu(&hook->node, &step_hook);
	174	spin_unlock(&step_hook_lock);
ee6214ce SP	175	}
	176
	177	void unregister_step_hook(struct step_hook *hook)
	178	{
cf0a2543 YS	179	spin_lock(&step_hook_lock);
	180	list_del_rcu(&hook->node);
	181	spin_unlock(&step_hook_lock);
	182	synchronize_rcu();
ee6214ce SP	183	}
	184
	185	/*
95485fdc	186	* Call registered single step handlers
ee6214ce SP	187	* There is no Syndrome info to check for determining the handler.
	188	* So we call all the registered handlers, until the right handler is
	189	* found which returns zero.
	190	*/
	191	static int call_step_hook(struct pt_regs *regs, unsigned int esr)
	192	{
	193	struct step_hook *hook;
	194	int retval = DBG_HOOK_ERROR;
	195
cf0a2543	196	rcu_read_lock();
ee6214ce	197
cf0a2543	198	list_for_each_entry_rcu(hook, &step_hook, node) {
ee6214ce SP	199	retval = hook->fn(regs, esr);
	200	if (retval == DBG_HOOK_HANDLED)
	201	break;
	202	}
	203
cf0a2543	204	rcu_read_unlock();
ee6214ce SP	205
	206	return retval;
	207	}
44b53f67	208	NOKPROBE_SYMBOL(call_step_hook);
ee6214ce	209
e04a28d4 WD	210	static void send_user_sigtrap(int si_code)
	211	{
	212	struct pt_regs *regs = current_pt_regs();
	213	siginfo_t info = {
	214	.si_signo = SIGTRAP,
	215	.si_errno = 0,
	216	.si_code = si_code,
	217	.si_addr = (void __user *)instruction_pointer(regs),
	218	};
	219
	220	if (WARN_ON(!user_mode(regs)))
	221	return;
	222
	223	if (interrupts_enabled(regs))
	224	local_irq_enable();
	225
	226	force_sig_info(SIGTRAP, &info, current);
	227	}
	228
478fcb2c WD	229	static int single_step_handler(unsigned long addr, unsigned int esr,
	230	struct pt_regs *regs)
	231	{
3fb69640 PA	232	bool handler_found = false;
3fb69640 PA	233
478fcb2c WD	234	/*
	235	* If we are stepping a pending breakpoint, call the hw_breakpoint
	236	* handler first.
	237	*/
	238	if (!reinstall_suspended_bps(regs))
	239	return 0;
	240
3fb69640 PA	241	#ifdef CONFIG_KPROBES
	242	if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
	243	handler_found = true;
	244	#endif
	245	if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
	246	handler_found = true;
	247
	248	if (!handler_found && user_mode(regs)) {
adeb68ef	249	send_user_sigtrap(TRAP_TRACE);
478fcb2c WD	250
	251	/*
	252	* ptrace will disable single step unless explicitly
	253	* asked to re-enable it. For other clients, it makes
	254	* sense to leave it enabled (i.e. rewind the controls
	255	* to the active-not-pending state).
	256	*/
	257	user_rewind_single_step(current);
3fb69640 PA	258	} else if (!handler_found) {
3fb69640 PA	259	pr_warn("Unexpected kernel single-step exception at EL1\n");
478fcb2c WD	260	/*
	261	* Re-enable stepping since we know that we will be
	262	* returning to regs.
	263	*/
	264	set_regs_spsr_ss(regs);
	265	}
	266
	267	return 0;
	268	}
44b53f67	269	NOKPROBE_SYMBOL(single_step_handler);
478fcb2c	270
ee6214ce SP	271	/*
	272	* Breakpoint handler is re-entrant as another breakpoint can
	273	* hit within breakpoint handler, especically in kprobes.
	274	* Use reader/writer locks instead of plain spinlock.
	275	*/
	276	static LIST_HEAD(break_hook);
62c6c61a	277	static DEFINE_SPINLOCK(break_hook_lock);
ee6214ce SP	278
	279	void register_break_hook(struct break_hook *hook)
	280	{
62c6c61a YS	281	spin_lock(&break_hook_lock);
	282	list_add_rcu(&hook->node, &break_hook);
	283	spin_unlock(&break_hook_lock);
ee6214ce SP	284	}
	285
	286	void unregister_break_hook(struct break_hook *hook)
	287	{
62c6c61a YS	288	spin_lock(&break_hook_lock);
	289	list_del_rcu(&hook->node);
	290	spin_unlock(&break_hook_lock);
	291	synchronize_rcu();
ee6214ce SP	292	}
	293
	294	static int call_break_hook(struct pt_regs *regs, unsigned int esr)
	295	{
	296	struct break_hook *hook;
	297	int (fn)(struct pt_regs regs, unsigned int esr) = NULL;
	298
62c6c61a YS	299	rcu_read_lock();
62c6c61a YS	300	list_for_each_entry_rcu(hook, &break_hook, node)
ee6214ce SP	301	if ((esr & hook->esr_mask) == hook->esr_val)
ee6214ce SP	302	fn = hook->fn;
62c6c61a	303	rcu_read_unlock();
ee6214ce SP	304
	305	return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
	306	}
44b53f67	307	NOKPROBE_SYMBOL(call_break_hook);
ee6214ce	308
1442b6ed WD	309	static int brk_handler(unsigned long addr, unsigned int esr,
	310	struct pt_regs *regs)
	311	{
53d07e21 PA	312	bool handler_found = false;
53d07e21 PA	313
2dd0e8d2	314	#ifdef CONFIG_KPROBES
53d07e21 PA	315	if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
	316	if (kprobe_breakpoint_handler(regs, esr) == DBG_HOOK_HANDLED)
	317	handler_found = true;
2dd0e8d2 SP	318	}
2dd0e8d2 SP	319	#endif
53d07e21 PA	320	if (!handler_found && call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
	321	handler_found = true;
	322
	323	if (!handler_found && user_mode(regs)) {
	324	send_user_sigtrap(TRAP_BRKPT);
	325	} else if (!handler_found) {
2dd0e8d2	326	pr_warn("Unexpected kernel BRK exception at EL1\n");
1442b6ed	327	return -EFAULT;
c878e0cf	328	}
1442b6ed	329
1442b6ed WD	330	return 0;
1442b6ed WD	331	}
44b53f67	332	NOKPROBE_SYMBOL(brk_handler);
1442b6ed WD	333
	334	int aarch32_break_handler(struct pt_regs *regs)
	335	{
2dacab73 ML	336	u32 arm_instr;
2dacab73 ML	337	u16 thumb_instr;
1442b6ed WD	338	bool bp = false;
	339	void __user pc = (void __user )instruction_pointer(regs);
	340
	341	if (!compat_user_mode(regs))
	342	return -EFAULT;
	343
	344	if (compat_thumb_mode(regs)) {
	345	/* get 16-bit Thumb instruction */
a5018b0e LVO	346	__le16 instr;
	347	get_user(instr, (__le16 __user *)pc);
	348	thumb_instr = le16_to_cpu(instr);
2dacab73	349	if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
1442b6ed	350	/* get second half of 32-bit Thumb-2 instruction */
a5018b0e LVO	351	get_user(instr, (__le16 __user *)(pc + 2));
a5018b0e LVO	352	thumb_instr = le16_to_cpu(instr);
2dacab73	353	bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
1442b6ed	354	} else {
2dacab73	355	bp = thumb_instr == AARCH32_BREAK_THUMB;
1442b6ed WD	356	}
	357	} else {
	358	/* 32-bit ARM instruction */
a5018b0e LVO	359	__le32 instr;
	360	get_user(instr, (__le32 __user *)pc);
	361	arm_instr = le32_to_cpu(instr);
2dacab73	362	bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
1442b6ed WD	363	}
	364
	365	if (!bp)
	366	return -EFAULT;
	367
e04a28d4	368	send_user_sigtrap(TRAP_BRKPT);
1442b6ed WD	369	return 0;
1442b6ed WD	370	}
44b53f67	371	NOKPROBE_SYMBOL(aarch32_break_handler);
1442b6ed WD	372
1442b6ed WD	373	static int __init debug_traps_init(void)
478fcb2c WD	374	{
478fcb2c WD	375	hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
adeb68ef	376	TRAP_TRACE, "single-step handler");
1442b6ed WD	377	hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
1442b6ed WD	378	TRAP_BRKPT, "ptrace BRK handler");
478fcb2c WD	379	return 0;
478fcb2c WD	380	}
1442b6ed	381	arch_initcall(debug_traps_init);
478fcb2c WD	382
	383	/* Re-enable single step for syscall restarting. */
	384	void user_rewind_single_step(struct task_struct *task)
	385	{
	386	/*
	387	* If single step is active for this thread, then set SPSR.SS
	388	* to 1 to avoid returning to the active-pending state.
	389	*/
	390	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	391	set_regs_spsr_ss(task_pt_regs(task));
	392	}
44b53f67	393	NOKPROBE_SYMBOL(user_rewind_single_step);
478fcb2c WD	394
	395	void user_fastforward_single_step(struct task_struct *task)
	396	{
	397	if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
	398	clear_regs_spsr_ss(task_pt_regs(task));
	399	}
	400
	401	/* Kernel API */
	402	void kernel_enable_single_step(struct pt_regs *regs)
	403	{
	404	WARN_ON(!irqs_disabled());
	405	set_regs_spsr_ss(regs);
	406	mdscr_write(mdscr_read() \| DBG_MDSCR_SS);
	407	enable_debug_monitors(DBG_ACTIVE_EL1);
	408	}
44b53f67	409	NOKPROBE_SYMBOL(kernel_enable_single_step);
478fcb2c WD	410
	411	void kernel_disable_single_step(void)
	412	{
	413	WARN_ON(!irqs_disabled());
	414	mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
	415	disable_debug_monitors(DBG_ACTIVE_EL1);
	416	}
44b53f67	417	NOKPROBE_SYMBOL(kernel_disable_single_step);
478fcb2c WD	418
	419	int kernel_active_single_step(void)
	420	{
	421	WARN_ON(!irqs_disabled());
	422	return mdscr_read() & DBG_MDSCR_SS;
	423	}
44b53f67	424	NOKPROBE_SYMBOL(kernel_active_single_step);
478fcb2c WD	425
	426	/* ptrace API */
	427	void user_enable_single_step(struct task_struct *task)
	428	{
3a402a70 WD	429	struct thread_info *ti = task_thread_info(task);
	430
	431	if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
	432	set_regs_spsr_ss(task_pt_regs(task));
478fcb2c	433	}
44b53f67	434	NOKPROBE_SYMBOL(user_enable_single_step);
478fcb2c WD	435
	436	void user_disable_single_step(struct task_struct *task)
	437	{
	438	clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
	439	}
44b53f67	440	NOKPROBE_SYMBOL(user_disable_single_step);