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/kprobes.h>
27 #include <linux/stat.h>
28 #include <linux/uaccess.h>
30 #include <asm/cpufeature.h>
31 #include <asm/cputype.h>
32 #include <asm/debug-monitors.h>
33 #include <asm/system_misc.h>
35 /* Determine debug architecture. */
36 u8 debug_monitors_arch(void)
38 return cpuid_feature_extract_unsigned_field(read_system_reg(SYS_ID_AA64DFR0_EL1),
39 ID_AA64DFR0_DEBUGVER_SHIFT);
43 * MDSCR access routines.
45 static void mdscr_write(u32 mdscr)
48 local_dbg_save(flags);
49 write_sysreg(mdscr, mdscr_el1);
50 local_dbg_restore(flags);
52 NOKPROBE_SYMBOL(mdscr_write);
54 static u32 mdscr_read(void)
56 return read_sysreg(mdscr_el1);
58 NOKPROBE_SYMBOL(mdscr_read);
61 * Allow root to disable self-hosted debug from userspace.
62 * This is useful if you want to connect an external JTAG debugger.
64 static bool debug_enabled = true;
66 static int create_debug_debugfs_entry(void)
68 debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
71 fs_initcall(create_debug_debugfs_entry);
73 static int __init early_debug_disable(char *buf)
75 debug_enabled = false;
79 early_param("nodebugmon", early_debug_disable);
82 * Keep track of debug users on each core.
83 * The ref counts are per-cpu so we use a local_t type.
85 static DEFINE_PER_CPU(int, mde_ref_count);
86 static DEFINE_PER_CPU(int, kde_ref_count);
88 void enable_debug_monitors(enum dbg_active_el el)
90 u32 mdscr, enable = 0;
92 WARN_ON(preemptible());
94 if (this_cpu_inc_return(mde_ref_count) == 1)
95 enable = DBG_MDSCR_MDE;
97 if (el == DBG_ACTIVE_EL1 &&
98 this_cpu_inc_return(kde_ref_count) == 1)
99 enable |= DBG_MDSCR_KDE;
101 if (enable && debug_enabled) {
102 mdscr = mdscr_read();
107 NOKPROBE_SYMBOL(enable_debug_monitors);
109 void disable_debug_monitors(enum dbg_active_el el)
111 u32 mdscr, disable = 0;
113 WARN_ON(preemptible());
115 if (this_cpu_dec_return(mde_ref_count) == 0)
116 disable = ~DBG_MDSCR_MDE;
118 if (el == DBG_ACTIVE_EL1 &&
119 this_cpu_dec_return(kde_ref_count) == 0)
120 disable &= ~DBG_MDSCR_KDE;
123 mdscr = mdscr_read();
128 NOKPROBE_SYMBOL(disable_debug_monitors);
133 static int clear_os_lock(unsigned int cpu)
135 write_sysreg(0, osdlr_el1);
136 write_sysreg(0, oslar_el1);
141 static int debug_monitors_init(void)
143 return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
144 "CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING",
145 clear_os_lock, NULL);
147 postcore_initcall(debug_monitors_init);
150 * Single step API and exception handling.
152 static void set_user_regs_spsr_ss(struct user_pt_regs *regs)
154 regs->pstate |= DBG_SPSR_SS;
156 NOKPROBE_SYMBOL(set_user_regs_spsr_ss);
158 static void clear_user_regs_spsr_ss(struct user_pt_regs *regs)
160 regs->pstate &= ~DBG_SPSR_SS;
162 NOKPROBE_SYMBOL(clear_user_regs_spsr_ss);
164 #define set_regs_spsr_ss(r) set_user_regs_spsr_ss(&(r)->user_regs)
165 #define clear_regs_spsr_ss(r) clear_user_regs_spsr_ss(&(r)->user_regs)
167 /* EL1 Single Step Handler hooks */
168 static LIST_HEAD(step_hook);
169 static DEFINE_SPINLOCK(step_hook_lock);
171 void register_step_hook(struct step_hook *hook)
173 spin_lock(&step_hook_lock);
174 list_add_rcu(&hook->node, &step_hook);
175 spin_unlock(&step_hook_lock);
178 void unregister_step_hook(struct step_hook *hook)
180 spin_lock(&step_hook_lock);
181 list_del_rcu(&hook->node);
182 spin_unlock(&step_hook_lock);
187 * Call registered single step handlers
188 * There is no Syndrome info to check for determining the handler.
189 * So we call all the registered handlers, until the right handler is
190 * found which returns zero.
192 static int call_step_hook(struct pt_regs *regs, unsigned int esr)
194 struct step_hook *hook;
195 int retval = DBG_HOOK_ERROR;
199 list_for_each_entry_rcu(hook, &step_hook, node) {
200 retval = hook->fn(regs, esr);
201 if (retval == DBG_HOOK_HANDLED)
209 NOKPROBE_SYMBOL(call_step_hook);
211 static void send_user_sigtrap(int si_code)
213 struct pt_regs *regs = current_pt_regs();
218 .si_addr = (void __user *)instruction_pointer(regs),
221 if (WARN_ON(!user_mode(regs)))
224 if (interrupts_enabled(regs))
227 force_sig_info(SIGTRAP, &info, current);
230 static int single_step_handler(unsigned long addr, unsigned int esr,
231 struct pt_regs *regs)
234 * If we are stepping a pending breakpoint, call the hw_breakpoint
237 if (!reinstall_suspended_bps(regs))
240 if (user_mode(regs)) {
241 send_user_sigtrap(TRAP_TRACE);
244 * ptrace will disable single step unless explicitly
245 * asked to re-enable it. For other clients, it makes
246 * sense to leave it enabled (i.e. rewind the controls
247 * to the active-not-pending state).
249 user_rewind_single_step(current);
251 #ifdef CONFIG_KPROBES
252 if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
255 if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
258 pr_warning("Unexpected kernel single-step exception at EL1\n");
260 * Re-enable stepping since we know that we will be
263 set_regs_spsr_ss(regs);
268 NOKPROBE_SYMBOL(single_step_handler);
271 * Breakpoint handler is re-entrant as another breakpoint can
272 * hit within breakpoint handler, especically in kprobes.
273 * Use reader/writer locks instead of plain spinlock.
275 static LIST_HEAD(break_hook);
276 static DEFINE_SPINLOCK(break_hook_lock);
278 void register_break_hook(struct break_hook *hook)
280 spin_lock(&break_hook_lock);
281 list_add_rcu(&hook->node, &break_hook);
282 spin_unlock(&break_hook_lock);
285 void unregister_break_hook(struct break_hook *hook)
287 spin_lock(&break_hook_lock);
288 list_del_rcu(&hook->node);
289 spin_unlock(&break_hook_lock);
293 static int call_break_hook(struct pt_regs *regs, unsigned int esr)
295 struct break_hook *hook;
296 int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;
299 list_for_each_entry_rcu(hook, &break_hook, node)
300 if ((esr & hook->esr_mask) == hook->esr_val)
304 return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
306 NOKPROBE_SYMBOL(call_break_hook);
308 static int brk_handler(unsigned long addr, unsigned int esr,
309 struct pt_regs *regs)
311 if (user_mode(regs)) {
312 send_user_sigtrap(TRAP_BRKPT);
314 #ifdef CONFIG_KPROBES
315 else if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
316 if (kprobe_breakpoint_handler(regs, esr) != DBG_HOOK_HANDLED)
320 else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
321 pr_warn("Unexpected kernel BRK exception at EL1\n");
327 NOKPROBE_SYMBOL(brk_handler);
329 int aarch32_break_handler(struct pt_regs *regs)
334 void __user *pc = (void __user *)instruction_pointer(regs);
336 if (!compat_user_mode(regs))
339 if (compat_thumb_mode(regs)) {
340 /* get 16-bit Thumb instruction */
341 get_user(thumb_instr, (u16 __user *)pc);
342 thumb_instr = le16_to_cpu(thumb_instr);
343 if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
344 /* get second half of 32-bit Thumb-2 instruction */
345 get_user(thumb_instr, (u16 __user *)(pc + 2));
346 thumb_instr = le16_to_cpu(thumb_instr);
347 bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
349 bp = thumb_instr == AARCH32_BREAK_THUMB;
352 /* 32-bit ARM instruction */
353 get_user(arm_instr, (u32 __user *)pc);
354 arm_instr = le32_to_cpu(arm_instr);
355 bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
361 send_user_sigtrap(TRAP_BRKPT);
364 NOKPROBE_SYMBOL(aarch32_break_handler);
366 static int __init debug_traps_init(void)
368 hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
369 TRAP_TRACE, "single-step handler");
370 hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
371 TRAP_BRKPT, "ptrace BRK handler");
374 arch_initcall(debug_traps_init);
376 /* Re-enable single step for syscall restarting. */
377 void user_rewind_single_step(struct task_struct *task)
380 * If single step is active for this thread, then set SPSR.SS
381 * to 1 to avoid returning to the active-pending state.
383 if (test_tsk_thread_flag(task, TIF_SINGLESTEP))
384 set_regs_spsr_ss(task_pt_regs(task));
386 NOKPROBE_SYMBOL(user_rewind_single_step);
388 void user_fastforward_single_step(struct task_struct *task)
390 if (test_tsk_thread_flag(task, TIF_SINGLESTEP))
391 clear_regs_spsr_ss(task_pt_regs(task));
394 void user_regs_reset_single_step(struct user_pt_regs *regs,
395 struct task_struct *task)
397 if (test_tsk_thread_flag(task, TIF_SINGLESTEP))
398 set_user_regs_spsr_ss(regs);
400 clear_user_regs_spsr_ss(regs);
404 void kernel_enable_single_step(struct pt_regs *regs)
406 WARN_ON(!irqs_disabled());
407 set_regs_spsr_ss(regs);
408 mdscr_write(mdscr_read() | DBG_MDSCR_SS);
409 enable_debug_monitors(DBG_ACTIVE_EL1);
411 NOKPROBE_SYMBOL(kernel_enable_single_step);
413 void kernel_disable_single_step(void)
415 WARN_ON(!irqs_disabled());
416 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
417 disable_debug_monitors(DBG_ACTIVE_EL1);
419 NOKPROBE_SYMBOL(kernel_disable_single_step);
421 int kernel_active_single_step(void)
423 WARN_ON(!irqs_disabled());
424 return mdscr_read() & DBG_MDSCR_SS;
426 NOKPROBE_SYMBOL(kernel_active_single_step);
429 void user_enable_single_step(struct task_struct *task)
431 struct thread_info *ti = task_thread_info(task);
433 if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
434 set_regs_spsr_ss(task_pt_regs(task));
436 NOKPROBE_SYMBOL(user_enable_single_step);
438 void user_disable_single_step(struct task_struct *task)
440 clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
442 NOKPROBE_SYMBOL(user_disable_single_step);