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));
142 static int os_lock_notify(struct notifier_block *self,
143 unsigned long action, void *data)
145 int cpu = (unsigned long)data;
146 if (action == CPU_ONLINE)
147 smp_call_function_single(cpu, clear_os_lock, NULL, 1);
151 static struct notifier_block os_lock_nb = {
152 .notifier_call = os_lock_notify,
155 static int debug_monitors_init(void)
157 cpu_notifier_register_begin();
159 /* Clear the OS lock. */
160 on_each_cpu(clear_os_lock, NULL, 1);
164 /* Register hotplug handler. */
165 __register_cpu_notifier(&os_lock_nb);
167 cpu_notifier_register_done();
170 postcore_initcall(debug_monitors_init);
173 * Single step API and exception handling.
175 static void set_regs_spsr_ss(struct pt_regs *regs)
180 spsr &= ~DBG_SPSR_SS;
185 static void clear_regs_spsr_ss(struct pt_regs *regs)
190 spsr &= ~DBG_SPSR_SS;
194 /* EL1 Single Step Handler hooks */
195 static LIST_HEAD(step_hook);
196 static DEFINE_RWLOCK(step_hook_lock);
198 void register_step_hook(struct step_hook *hook)
200 write_lock(&step_hook_lock);
201 list_add(&hook->node, &step_hook);
202 write_unlock(&step_hook_lock);
205 void unregister_step_hook(struct step_hook *hook)
207 write_lock(&step_hook_lock);
208 list_del(&hook->node);
209 write_unlock(&step_hook_lock);
213 * Call registered single step handers
214 * There is no Syndrome info to check for determining the handler.
215 * So we call all the registered handlers, until the right handler is
216 * found which returns zero.
218 static int call_step_hook(struct pt_regs *regs, unsigned int esr)
220 struct step_hook *hook;
221 int retval = DBG_HOOK_ERROR;
223 read_lock(&step_hook_lock);
225 list_for_each_entry(hook, &step_hook, node) {
226 retval = hook->fn(regs, esr);
227 if (retval == DBG_HOOK_HANDLED)
231 read_unlock(&step_hook_lock);
236 static int single_step_handler(unsigned long addr, unsigned int esr,
237 struct pt_regs *regs)
242 * If we are stepping a pending breakpoint, call the hw_breakpoint
245 if (!reinstall_suspended_bps(regs))
248 if (user_mode(regs)) {
249 info.si_signo = SIGTRAP;
251 info.si_code = TRAP_HWBKPT;
252 info.si_addr = (void __user *)instruction_pointer(regs);
253 force_sig_info(SIGTRAP, &info, current);
256 * ptrace will disable single step unless explicitly
257 * asked to re-enable it. For other clients, it makes
258 * sense to leave it enabled (i.e. rewind the controls
259 * to the active-not-pending state).
261 user_rewind_single_step(current);
263 if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
266 pr_warning("Unexpected kernel single-step exception at EL1\n");
268 * Re-enable stepping since we know that we will be
271 set_regs_spsr_ss(regs);
278 * Breakpoint handler is re-entrant as another breakpoint can
279 * hit within breakpoint handler, especically in kprobes.
280 * Use reader/writer locks instead of plain spinlock.
282 static LIST_HEAD(break_hook);
283 static DEFINE_RWLOCK(break_hook_lock);
285 void register_break_hook(struct break_hook *hook)
287 write_lock(&break_hook_lock);
288 list_add(&hook->node, &break_hook);
289 write_unlock(&break_hook_lock);
292 void unregister_break_hook(struct break_hook *hook)
294 write_lock(&break_hook_lock);
295 list_del(&hook->node);
296 write_unlock(&break_hook_lock);
299 static int call_break_hook(struct pt_regs *regs, unsigned int esr)
301 struct break_hook *hook;
302 int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;
304 read_lock(&break_hook_lock);
305 list_for_each_entry(hook, &break_hook, node)
306 if ((esr & hook->esr_mask) == hook->esr_val)
308 read_unlock(&break_hook_lock);
310 return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
313 static int brk_handler(unsigned long addr, unsigned int esr,
314 struct pt_regs *regs)
318 if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
321 if (!user_mode(regs))
327 .si_code = TRAP_BRKPT,
328 .si_addr = (void __user *)instruction_pointer(regs),
331 force_sig_info(SIGTRAP, &info, current);
335 int aarch32_break_handler(struct pt_regs *regs)
341 void __user *pc = (void __user *)instruction_pointer(regs);
343 if (!compat_user_mode(regs))
346 if (compat_thumb_mode(regs)) {
347 /* get 16-bit Thumb instruction */
348 get_user(thumb_instr, (u16 __user *)pc);
349 thumb_instr = le16_to_cpu(thumb_instr);
350 if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
351 /* get second half of 32-bit Thumb-2 instruction */
352 get_user(thumb_instr, (u16 __user *)(pc + 2));
353 thumb_instr = le16_to_cpu(thumb_instr);
354 bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
356 bp = thumb_instr == AARCH32_BREAK_THUMB;
359 /* 32-bit ARM instruction */
360 get_user(arm_instr, (u32 __user *)pc);
361 arm_instr = le32_to_cpu(arm_instr);
362 bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
371 .si_code = TRAP_BRKPT,
375 force_sig_info(SIGTRAP, &info, current);
379 static int __init debug_traps_init(void)
381 hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
382 TRAP_HWBKPT, "single-step handler");
383 hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
384 TRAP_BRKPT, "ptrace BRK handler");
387 arch_initcall(debug_traps_init);
389 /* Re-enable single step for syscall restarting. */
390 void user_rewind_single_step(struct task_struct *task)
393 * If single step is active for this thread, then set SPSR.SS
394 * to 1 to avoid returning to the active-pending state.
396 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
397 set_regs_spsr_ss(task_pt_regs(task));
400 void user_fastforward_single_step(struct task_struct *task)
402 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
403 clear_regs_spsr_ss(task_pt_regs(task));
407 void kernel_enable_single_step(struct pt_regs *regs)
409 WARN_ON(!irqs_disabled());
410 set_regs_spsr_ss(regs);
411 mdscr_write(mdscr_read() | DBG_MDSCR_SS);
412 enable_debug_monitors(DBG_ACTIVE_EL1);
415 void kernel_disable_single_step(void)
417 WARN_ON(!irqs_disabled());
418 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
419 disable_debug_monitors(DBG_ACTIVE_EL1);
422 int kernel_active_single_step(void)
424 WARN_ON(!irqs_disabled());
425 return mdscr_read() & DBG_MDSCR_SS;
429 void user_enable_single_step(struct task_struct *task)
431 set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
432 set_regs_spsr_ss(task_pt_regs(task));
435 void user_disable_single_step(struct task_struct *task)
437 clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);