// SPDX-License-Identifier: GPL-2.0-only/* * ARMv8 single-step debug support and mdscr context switching. * * Copyright (C) 2012 ARM Limited * * 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>#include <asm/traps.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_EL1_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 __init 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_user_regs_spsr_ss(struct user_pt_regs *regs){	regs->pstate |= DBG_SPSR_SS;}NOKPROBE_SYMBOL(set_user_regs_spsr_ss); static void clear_user_regs_spsr_ss(struct user_pt_regs *regs){	regs->pstate &= ~DBG_SPSR_SS;}NOKPROBE_SYMBOL(clear_user_regs_spsr_ss); #define set_regs_spsr_ss(r)	set_user_regs_spsr_ss(&(r)->user_regs)#define clear_regs_spsr_ss(r)	clear_user_regs_spsr_ss(&(r)->user_regs) static DEFINE_SPINLOCK(debug_hook_lock);static LIST_HEAD(user_step_hook);static LIST_HEAD(kernel_step_hook); static void register_debug_hook(struct list_head *node, struct list_head *list){	spin_lock(&debug_hook_lock);	list_add_rcu(node, list);	spin_unlock(&debug_hook_lock); } static void unregister_debug_hook(struct list_head *node){	spin_lock(&debug_hook_lock);	list_del_rcu(node);	spin_unlock(&debug_hook_lock);	synchronize_rcu();} void register_user_step_hook(struct step_hook *hook){	register_debug_hook(&hook->node, &user_step_hook);} void unregister_user_step_hook(struct step_hook *hook){	unregister_debug_hook(&hook->node);} void register_kernel_step_hook(struct step_hook *hook){	register_debug_hook(&hook->node, &kernel_step_hook);} void unregister_kernel_step_hook(struct step_hook *hook){	unregister_debug_hook(&hook->node);} /* * 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 long esr){	struct step_hook *hook;	struct list_head *list;	int retval = DBG_HOOK_ERROR; 	list = user_mode(regs) ? &user_step_hook : &kernel_step_hook; 	/*	 * Since single-step exception disables interrupt, this function is	 * entirely not preemptible, and we can use rcu list safely here.	 */	list_for_each_entry_rcu(hook, list, node)	{		retval = hook->fn(regs, esr);		if (retval == DBG_HOOK_HANDLED)			break;	} 	return retval;}NOKPROBE_SYMBOL(call_step_hook); static void send_user_sigtrap(int si_code){	struct pt_regs *regs = current_pt_regs(); 	if (WARN_ON(!user_mode(regs)))		return; 	if (interrupts_enabled(regs))		local_irq_enable(); 	arm64_force_sig_fault(SIGTRAP, si_code, instruction_pointer(regs),			      "User debug trap");} static int single_step_handler(unsigned long unused, unsigned long 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; 	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); static LIST_HEAD(user_break_hook);static LIST_HEAD(kernel_break_hook); void register_user_break_hook(struct break_hook *hook){	register_debug_hook(&hook->node, &user_break_hook);} void unregister_user_break_hook(struct break_hook *hook){	unregister_debug_hook(&hook->node);} void register_kernel_break_hook(struct break_hook *hook){	register_debug_hook(&hook->node, &kernel_break_hook);} void unregister_kernel_break_hook(struct break_hook *hook){	unregister_debug_hook(&hook->node);} static int call_break_hook(struct pt_regs *regs, unsigned long esr){	struct break_hook *hook;	struct list_head *list; 	list = user_mode(regs) ? &user_break_hook : &kernel_break_hook; 	/*	 * Since brk exception disables interrupt, this function is	 * entirely not preemptible, and we can use rcu list safely here.	 */	list_for_each_entry_rcu(hook, list, node) {		if ((esr_brk_comment(esr) & ~hook->mask) == hook->imm)			return hook->fn(regs, esr);	} 	return DBG_HOOK_ERROR;}NOKPROBE_SYMBOL(call_break_hook); static int brk_handler(unsigned long unused, unsigned long esr,		       struct pt_regs *regs){	if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)		return 0; 	if (user_mode(regs)) {		send_user_sigtrap(TRAP_BRKPT);	} else {		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); void __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, "BRK handler");} /* 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_tsk_thread_flag(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_tsk_thread_flag(task, TIF_SINGLESTEP))		clear_regs_spsr_ss(task_pt_regs(task));} void user_regs_reset_single_step(struct user_pt_regs *regs,				 struct task_struct *task){	if (test_tsk_thread_flag(task, TIF_SINGLESTEP))		set_user_regs_spsr_ss(regs);	else		clear_user_regs_spsr_ss(regs);} /* 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); void kernel_rewind_single_step(struct pt_regs *regs){	set_regs_spsr_ss(regs);} void kernel_fastforward_single_step(struct pt_regs *regs){	clear_regs_spsr_ss(regs);} /* 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);