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/local.h>
31 #include <asm/cputype.h>
32 #include <asm/system_misc.h>
34 /* Low-level stepping controls. */
35 #define DBG_MDSCR_SS (1 << 0)
36 #define DBG_SPSR_SS (1 << 21)
38 /* MDSCR_EL1 enabling bits */
39 #define DBG_MDSCR_KDE (1 << 13)
40 #define DBG_MDSCR_MDE (1 << 15)
41 #define DBG_MDSCR_MASK ~(DBG_MDSCR_KDE | DBG_MDSCR_MDE)
43 /* Determine debug architecture. */
44 u8 debug_monitors_arch(void)
46 return read_cpuid(ID_AA64DFR0_EL1) & 0xf;
50 * MDSCR access routines.
52 static void mdscr_write(u32 mdscr)
55 local_dbg_save(flags);
56 asm volatile("msr mdscr_el1, %0" :: "r" (mdscr));
57 local_dbg_restore(flags);
60 static u32 mdscr_read(void)
63 asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr));
68 * Allow root to disable self-hosted debug from userspace.
69 * This is useful if you want to connect an external JTAG debugger.
71 static u32 debug_enabled = 1;
73 static int create_debug_debugfs_entry(void)
75 debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
78 fs_initcall(create_debug_debugfs_entry);
80 static int __init early_debug_disable(char *buf)
86 early_param("nodebugmon", early_debug_disable);
89 * Keep track of debug users on each core.
90 * The ref counts are per-cpu so we use a local_t type.
92 static DEFINE_PER_CPU(local_t, mde_ref_count);
93 static DEFINE_PER_CPU(local_t, kde_ref_count);
95 void enable_debug_monitors(enum debug_el el)
97 u32 mdscr, enable = 0;
99 WARN_ON(preemptible());
101 if (local_inc_return(&__get_cpu_var(mde_ref_count)) == 1)
102 enable = DBG_MDSCR_MDE;
104 if (el == DBG_ACTIVE_EL1 &&
105 local_inc_return(&__get_cpu_var(kde_ref_count)) == 1)
106 enable |= DBG_MDSCR_KDE;
108 if (enable && debug_enabled) {
109 mdscr = mdscr_read();
115 void disable_debug_monitors(enum debug_el el)
117 u32 mdscr, disable = 0;
119 WARN_ON(preemptible());
121 if (local_dec_and_test(&__get_cpu_var(mde_ref_count)))
122 disable = ~DBG_MDSCR_MDE;
124 if (el == DBG_ACTIVE_EL1 &&
125 local_dec_and_test(&__get_cpu_var(kde_ref_count)))
126 disable &= ~DBG_MDSCR_KDE;
129 mdscr = mdscr_read();
138 static void clear_os_lock(void *unused)
140 asm volatile("msr oslar_el1, %0" : : "r" (0));
143 static int __cpuinit 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 __cpuinitdata os_lock_nb = {
153 .notifier_call = os_lock_notify,
156 static int __cpuinit debug_monitors_init(void)
158 /* Clear the OS lock. */
159 on_each_cpu(clear_os_lock, NULL, 1);
163 /* Register hotplug handler. */
164 register_cpu_notifier(&os_lock_nb);
167 postcore_initcall(debug_monitors_init);
170 * Single step API and exception handling.
172 static void set_regs_spsr_ss(struct pt_regs *regs)
177 spsr &= ~DBG_SPSR_SS;
182 static void clear_regs_spsr_ss(struct pt_regs *regs)
187 spsr &= ~DBG_SPSR_SS;
191 /* EL1 Single Step Handler hooks */
192 static LIST_HEAD(step_hook);
193 DEFINE_RWLOCK(step_hook_lock);
195 void register_step_hook(struct step_hook *hook)
197 write_lock(&step_hook_lock);
198 list_add(&hook->node, &step_hook);
199 write_unlock(&step_hook_lock);
202 void unregister_step_hook(struct step_hook *hook)
204 write_lock(&step_hook_lock);
205 list_del(&hook->node);
206 write_unlock(&step_hook_lock);
210 * Call registered single step handers
211 * There is no Syndrome info to check for determining the handler.
212 * So we call all the registered handlers, until the right handler is
213 * found which returns zero.
215 static int call_step_hook(struct pt_regs *regs, unsigned int esr)
217 struct step_hook *hook;
218 int retval = DBG_HOOK_ERROR;
220 read_lock(&step_hook_lock);
222 list_for_each_entry(hook, &step_hook, node) {
223 retval = hook->fn(regs, esr);
224 if (retval == DBG_HOOK_HANDLED)
228 read_unlock(&step_hook_lock);
233 static int single_step_handler(unsigned long addr, unsigned int esr,
234 struct pt_regs *regs)
239 * If we are stepping a pending breakpoint, call the hw_breakpoint
242 if (!reinstall_suspended_bps(regs))
245 if (user_mode(regs)) {
246 info.si_signo = SIGTRAP;
248 info.si_code = TRAP_HWBKPT;
249 info.si_addr = (void __user *)instruction_pointer(regs);
250 force_sig_info(SIGTRAP, &info, current);
253 * ptrace will disable single step unless explicitly
254 * asked to re-enable it. For other clients, it makes
255 * sense to leave it enabled (i.e. rewind the controls
256 * to the active-not-pending state).
258 user_rewind_single_step(current);
260 if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
263 pr_warning("Unexpected kernel single-step exception at EL1\n");
265 * Re-enable stepping since we know that we will be
268 set_regs_spsr_ss(regs);
275 * Breakpoint handler is re-entrant as another breakpoint can
276 * hit within breakpoint handler, especically in kprobes.
277 * Use reader/writer locks instead of plain spinlock.
279 static LIST_HEAD(break_hook);
280 DEFINE_RWLOCK(break_hook_lock);
282 void register_break_hook(struct break_hook *hook)
284 write_lock(&break_hook_lock);
285 list_add(&hook->node, &break_hook);
286 write_unlock(&break_hook_lock);
289 void unregister_break_hook(struct break_hook *hook)
291 write_lock(&break_hook_lock);
292 list_del(&hook->node);
293 write_unlock(&break_hook_lock);
296 static int call_break_hook(struct pt_regs *regs, unsigned int esr)
298 struct break_hook *hook;
299 int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;
301 read_lock(&break_hook_lock);
302 list_for_each_entry(hook, &break_hook, node)
303 if ((esr & hook->esr_mask) == hook->esr_val)
305 read_unlock(&break_hook_lock);
307 return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
310 static int brk_handler(unsigned long addr, unsigned int esr,
311 struct pt_regs *regs)
315 if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
318 pr_warn("unexpected brk exception at %lx, esr=0x%x\n",
319 (long)instruction_pointer(regs), esr);
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)
340 void __user *pc = (void __user *)instruction_pointer(regs);
342 if (!compat_user_mode(regs))
345 if (compat_thumb_mode(regs)) {
346 /* get 16-bit Thumb instruction */
347 get_user(instr, (u16 __user *)pc);
348 if (instr == AARCH32_BREAK_THUMB2_LO) {
349 /* get second half of 32-bit Thumb-2 instruction */
350 get_user(instr, (u16 __user *)(pc + 2));
351 bp = instr == AARCH32_BREAK_THUMB2_HI;
353 bp = instr == AARCH32_BREAK_THUMB;
356 /* 32-bit ARM instruction */
357 get_user(instr, (u32 __user *)pc);
358 bp = (instr & ~0xf0000000) == AARCH32_BREAK_ARM;
367 .si_code = TRAP_BRKPT,
371 force_sig_info(SIGTRAP, &info, current);
375 static int __init debug_traps_init(void)
377 hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
378 TRAP_HWBKPT, "single-step handler");
379 hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
380 TRAP_BRKPT, "ptrace BRK handler");
383 arch_initcall(debug_traps_init);
385 /* Re-enable single step for syscall restarting. */
386 void user_rewind_single_step(struct task_struct *task)
389 * If single step is active for this thread, then set SPSR.SS
390 * to 1 to avoid returning to the active-pending state.
392 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
393 set_regs_spsr_ss(task_pt_regs(task));
396 void user_fastforward_single_step(struct task_struct *task)
398 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
399 clear_regs_spsr_ss(task_pt_regs(task));
403 void kernel_enable_single_step(struct pt_regs *regs)
405 WARN_ON(!irqs_disabled());
406 set_regs_spsr_ss(regs);
407 mdscr_write(mdscr_read() | DBG_MDSCR_SS);
408 enable_debug_monitors(DBG_ACTIVE_EL1);
411 void kernel_disable_single_step(void)
413 WARN_ON(!irqs_disabled());
414 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
415 disable_debug_monitors(DBG_ACTIVE_EL1);
418 int kernel_active_single_step(void)
420 WARN_ON(!irqs_disabled());
421 return mdscr_read() & DBG_MDSCR_SS;
425 void user_enable_single_step(struct task_struct *task)
427 set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
428 set_regs_spsr_ss(task_pt_regs(task));
431 void user_disable_single_step(struct task_struct *task)
433 clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);