/* * 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/stat.h> #include <asm/debug-monitors.h>#include <asm/local.h>#include <asm/cputype.h>#include <asm/system_misc.h> /* Low-level stepping controls. */#define DBG_MDSCR_SS		(1 << 0)#define DBG_SPSR_SS		(1 << 21) /* MDSCR_EL1 enabling bits */#define DBG_MDSCR_KDE		(1 << 13)#define DBG_MDSCR_MDE		(1 << 15)#define DBG_MDSCR_MASK		~(DBG_MDSCR_KDE | DBG_MDSCR_MDE) /* Determine debug architecture. */u8 debug_monitors_arch(void){	return read_cpuid(ID_AA64DFR0_EL1) & 0xf;} /* * 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 u32 debug_enabled = 1; 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 = 0;	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(local_t, mde_ref_count);static DEFINE_PER_CPU(local_t, kde_ref_count); void enable_debug_monitors(enum debug_el el){	u32 mdscr, enable = 0; 	WARN_ON(preemptible()); 	if (local_inc_return(&__get_cpu_var(mde_ref_count)) == 1)		enable = DBG_MDSCR_MDE; 	if (el == DBG_ACTIVE_EL1 &&	    local_inc_return(&__get_cpu_var(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 debug_el el){	u32 mdscr, disable = 0; 	WARN_ON(preemptible()); 	if (local_dec_and_test(&__get_cpu_var(mde_ref_count)))		disable = ~DBG_MDSCR_MDE; 	if (el == DBG_ACTIVE_EL1 &&	    local_dec_and_test(&__get_cpu_var(kde_ref_count)))		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 mdscr_el1, %0" : : "r" (0));	isb();	asm volatile("msr oslar_el1, %0" : : "r" (0));	isb();} static int __cpuinit os_lock_notify(struct notifier_block *self,				    unsigned long action, void *data){	int cpu = (unsigned long)data;	if (action == CPU_ONLINE)		smp_call_function_single(cpu, clear_os_lock, NULL, 1);	return NOTIFY_OK;} static struct notifier_block __cpuinitdata os_lock_nb = {	.notifier_call = os_lock_notify,}; static int __cpuinit debug_monitors_init(void){	/* Clear the OS lock. */	smp_call_function(clear_os_lock, NULL, 1);	clear_os_lock(NULL); 	/* Register hotplug handler. */	register_cpu_notifier(&os_lock_nb);	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;} static int single_step_handler(unsigned long addr, unsigned int esr,			       struct pt_regs *regs){	siginfo_t info; 	/*	 * If we are stepping a pending breakpoint, call the hw_breakpoint	 * handler first.	 */	if (!reinstall_suspended_bps(regs))		return 0; 	if (user_mode(regs)) {		info.si_signo = SIGTRAP;		info.si_errno = 0;		info.si_code  = TRAP_HWBKPT;		info.si_addr  = (void __user *)instruction_pointer(regs);		force_sig_info(SIGTRAP, &info, current); 		/*		 * 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 {		/* TODO: route to KGDB */		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;} static int __init single_step_init(void){	hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,			      TRAP_HWBKPT, "single-step handler");	return 0;}arch_initcall(single_step_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);}