2 * ARMv8 single-step debug support and mdscr context switching.
4 * Copyright (C) 2012 ARM Limited
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.
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.
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/>.
18 * Author: Will Deacon <will.deacon@arm.com>
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>
26 #include <linux/stat.h>
27 #include <linux/uaccess.h>
29 #include <asm/debug-monitors.h>
30 #include <asm/cputype.h>
31 #include <asm/system_misc.h>
33 /* Low-level stepping controls. */
34 #define DBG_MDSCR_SS (1 << 0)
35 #define DBG_SPSR_SS (1 << 21)
37 /* MDSCR_EL1 enabling bits */
38 #define DBG_MDSCR_KDE (1 << 13)
39 #define DBG_MDSCR_MDE (1 << 15)
40 #define DBG_MDSCR_MASK ~(DBG_MDSCR_KDE | DBG_MDSCR_MDE)
42 /* Determine debug architecture. */
43 u8 debug_monitors_arch(void)
45 return read_cpuid(ID_AA64DFR0_EL1) & 0xf;
49 * MDSCR access routines.
51 static void mdscr_write(u32 mdscr)
54 local_dbg_save(flags);
55 asm volatile("msr mdscr_el1, %0" :: "r" (mdscr));
56 local_dbg_restore(flags);
59 static u32 mdscr_read(void)
62 asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr));
67 * Allow root to disable self-hosted debug from userspace.
68 * This is useful if you want to connect an external JTAG debugger.
70 static u32 debug_enabled = 1;
72 static int create_debug_debugfs_entry(void)
74 debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
77 fs_initcall(create_debug_debugfs_entry);
79 static int __init early_debug_disable(char *buf)
85 early_param("nodebugmon", early_debug_disable);
88 * Keep track of debug users on each core.
89 * The ref counts are per-cpu so we use a local_t type.
91 static DEFINE_PER_CPU(int, mde_ref_count);
92 static DEFINE_PER_CPU(int, kde_ref_count);
94 void enable_debug_monitors(enum debug_el el)
96 u32 mdscr, enable = 0;
98 WARN_ON(preemptible());
100 if (this_cpu_inc_return(mde_ref_count) == 1)
101 enable = DBG_MDSCR_MDE;
103 if (el == DBG_ACTIVE_EL1 &&
104 this_cpu_inc_return(kde_ref_count) == 1)
105 enable |= DBG_MDSCR_KDE;
107 if (enable && debug_enabled) {
108 mdscr = mdscr_read();
114 void disable_debug_monitors(enum debug_el el)
116 u32 mdscr, disable = 0;
118 WARN_ON(preemptible());
120 if (this_cpu_dec_return(mde_ref_count) == 0)
121 disable = ~DBG_MDSCR_MDE;
123 if (el == DBG_ACTIVE_EL1 &&
124 this_cpu_dec_return(kde_ref_count) == 0)
125 disable &= ~DBG_MDSCR_KDE;
128 mdscr = mdscr_read();
137 static void clear_os_lock(void *unused)
139 asm volatile("msr oslar_el1, %0" : : "r" (0));
143 static int os_lock_notify(struct notifier_block *self,
144 unsigned long action, void *data)
146 int cpu = (unsigned long)data;
147 if (action == CPU_ONLINE)
148 smp_call_function_single(cpu, clear_os_lock, NULL, 1);
152 static struct notifier_block os_lock_nb = {
153 .notifier_call = os_lock_notify,
156 static int debug_monitors_init(void)
158 /* Clear the OS lock. */
159 smp_call_function(clear_os_lock, NULL, 1);
162 /* Register hotplug handler. */
163 register_cpu_notifier(&os_lock_nb);
166 postcore_initcall(debug_monitors_init);
169 * Single step API and exception handling.
171 static void set_regs_spsr_ss(struct pt_regs *regs)
176 spsr &= ~DBG_SPSR_SS;
181 static void clear_regs_spsr_ss(struct pt_regs *regs)
186 spsr &= ~DBG_SPSR_SS;
190 static int single_step_handler(unsigned long addr, unsigned int esr,
191 struct pt_regs *regs)
196 * If we are stepping a pending breakpoint, call the hw_breakpoint
199 if (!reinstall_suspended_bps(regs))
202 if (user_mode(regs)) {
203 info.si_signo = SIGTRAP;
205 info.si_code = TRAP_HWBKPT;
206 info.si_addr = (void __user *)instruction_pointer(regs);
207 force_sig_info(SIGTRAP, &info, current);
210 * ptrace will disable single step unless explicitly
211 * asked to re-enable it. For other clients, it makes
212 * sense to leave it enabled (i.e. rewind the controls
213 * to the active-not-pending state).
215 user_rewind_single_step(current);
217 /* TODO: route to KGDB */
218 pr_warning("Unexpected kernel single-step exception at EL1\n");
220 * Re-enable stepping since we know that we will be
223 set_regs_spsr_ss(regs);
229 static int brk_handler(unsigned long addr, unsigned int esr,
230 struct pt_regs *regs)
234 if (!user_mode(regs))
240 .si_code = TRAP_BRKPT,
241 .si_addr = (void __user *)instruction_pointer(regs),
244 force_sig_info(SIGTRAP, &info, current);
248 int aarch32_break_handler(struct pt_regs *regs)
253 void __user *pc = (void __user *)instruction_pointer(regs);
255 if (!compat_user_mode(regs))
258 if (compat_thumb_mode(regs)) {
259 /* get 16-bit Thumb instruction */
260 get_user(instr, (u16 __user *)pc);
261 if (instr == AARCH32_BREAK_THUMB2_LO) {
262 /* get second half of 32-bit Thumb-2 instruction */
263 get_user(instr, (u16 __user *)(pc + 2));
264 bp = instr == AARCH32_BREAK_THUMB2_HI;
266 bp = instr == AARCH32_BREAK_THUMB;
269 /* 32-bit ARM instruction */
270 get_user(instr, (u32 __user *)pc);
271 bp = (instr & ~0xf0000000) == AARCH32_BREAK_ARM;
280 .si_code = TRAP_BRKPT,
284 force_sig_info(SIGTRAP, &info, current);
288 static int __init debug_traps_init(void)
290 hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
291 TRAP_HWBKPT, "single-step handler");
292 hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
293 TRAP_BRKPT, "ptrace BRK handler");
296 arch_initcall(debug_traps_init);
298 /* Re-enable single step for syscall restarting. */
299 void user_rewind_single_step(struct task_struct *task)
302 * If single step is active for this thread, then set SPSR.SS
303 * to 1 to avoid returning to the active-pending state.
305 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
306 set_regs_spsr_ss(task_pt_regs(task));
309 void user_fastforward_single_step(struct task_struct *task)
311 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
312 clear_regs_spsr_ss(task_pt_regs(task));
316 void kernel_enable_single_step(struct pt_regs *regs)
318 WARN_ON(!irqs_disabled());
319 set_regs_spsr_ss(regs);
320 mdscr_write(mdscr_read() | DBG_MDSCR_SS);
321 enable_debug_monitors(DBG_ACTIVE_EL1);
324 void kernel_disable_single_step(void)
326 WARN_ON(!irqs_disabled());
327 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
328 disable_debug_monitors(DBG_ACTIVE_EL1);
331 int kernel_active_single_step(void)
333 WARN_ON(!irqs_disabled());
334 return mdscr_read() & DBG_MDSCR_SS;
338 void user_enable_single_step(struct task_struct *task)
340 set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
341 set_regs_spsr_ss(task_pt_regs(task));
344 void user_disable_single_step(struct task_struct *task)
346 clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);