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 asm volatile("msr mdscr_el1, %0" :: "r" (mdscr
));
50 local_dbg_restore(flags
);
52 NOKPROBE_SYMBOL(mdscr_write
);
54 static u32
mdscr_read(void)
57 asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr
));
60 NOKPROBE_SYMBOL(mdscr_read
);
63 * Allow root to disable self-hosted debug from userspace.
64 * This is useful if you want to connect an external JTAG debugger.
66 static bool debug_enabled
= true;
68 static int create_debug_debugfs_entry(void)
70 debugfs_create_bool("debug_enabled", 0644, NULL
, &debug_enabled
);
73 fs_initcall(create_debug_debugfs_entry
);
75 static int __init
early_debug_disable(char *buf
)
77 debug_enabled
= false;
81 early_param("nodebugmon", early_debug_disable
);
84 * Keep track of debug users on each core.
85 * The ref counts are per-cpu so we use a local_t type.
87 static DEFINE_PER_CPU(int, mde_ref_count
);
88 static DEFINE_PER_CPU(int, kde_ref_count
);
90 void enable_debug_monitors(enum dbg_active_el el
)
92 u32 mdscr
, enable
= 0;
94 WARN_ON(preemptible());
96 if (this_cpu_inc_return(mde_ref_count
) == 1)
97 enable
= DBG_MDSCR_MDE
;
99 if (el
== DBG_ACTIVE_EL1
&&
100 this_cpu_inc_return(kde_ref_count
) == 1)
101 enable
|= DBG_MDSCR_KDE
;
103 if (enable
&& debug_enabled
) {
104 mdscr
= mdscr_read();
109 NOKPROBE_SYMBOL(enable_debug_monitors
);
111 void disable_debug_monitors(enum dbg_active_el el
)
113 u32 mdscr
, disable
= 0;
115 WARN_ON(preemptible());
117 if (this_cpu_dec_return(mde_ref_count
) == 0)
118 disable
= ~DBG_MDSCR_MDE
;
120 if (el
== DBG_ACTIVE_EL1
&&
121 this_cpu_dec_return(kde_ref_count
) == 0)
122 disable
&= ~DBG_MDSCR_KDE
;
125 mdscr
= mdscr_read();
130 NOKPROBE_SYMBOL(disable_debug_monitors
);
135 static void clear_os_lock(void *unused
)
137 asm volatile("msr oslar_el1, %0" : : "r" (0));
140 static int os_lock_notify(struct notifier_block
*self
,
141 unsigned long action
, void *data
)
143 if ((action
& ~CPU_TASKS_FROZEN
) == CPU_ONLINE
)
148 static struct notifier_block os_lock_nb
= {
149 .notifier_call
= os_lock_notify
,
152 static int debug_monitors_init(void)
154 cpu_notifier_register_begin();
156 /* Clear the OS lock. */
157 on_each_cpu(clear_os_lock
, NULL
, 1);
160 /* Register hotplug handler. */
161 __register_cpu_notifier(&os_lock_nb
);
163 cpu_notifier_register_done();
166 postcore_initcall(debug_monitors_init
);
169 * Single step API and exception handling.
171 static void set_regs_spsr_ss(struct pt_regs
*regs
)
173 regs
->pstate
|= DBG_SPSR_SS
;
175 NOKPROBE_SYMBOL(set_regs_spsr_ss
);
177 static void clear_regs_spsr_ss(struct pt_regs
*regs
)
179 regs
->pstate
&= ~DBG_SPSR_SS
;
181 NOKPROBE_SYMBOL(clear_regs_spsr_ss
);
183 /* EL1 Single Step Handler hooks */
184 static LIST_HEAD(step_hook
);
185 static DEFINE_SPINLOCK(step_hook_lock
);
187 void register_step_hook(struct step_hook
*hook
)
189 spin_lock(&step_hook_lock
);
190 list_add_rcu(&hook
->node
, &step_hook
);
191 spin_unlock(&step_hook_lock
);
194 void unregister_step_hook(struct step_hook
*hook
)
196 spin_lock(&step_hook_lock
);
197 list_del_rcu(&hook
->node
);
198 spin_unlock(&step_hook_lock
);
203 * Call registered single step handlers
204 * There is no Syndrome info to check for determining the handler.
205 * So we call all the registered handlers, until the right handler is
206 * found which returns zero.
208 static int call_step_hook(struct pt_regs
*regs
, unsigned int esr
)
210 struct step_hook
*hook
;
211 int retval
= DBG_HOOK_ERROR
;
215 list_for_each_entry_rcu(hook
, &step_hook
, node
) {
216 retval
= hook
->fn(regs
, esr
);
217 if (retval
== DBG_HOOK_HANDLED
)
225 NOKPROBE_SYMBOL(call_step_hook
);
227 static void send_user_sigtrap(int si_code
)
229 struct pt_regs
*regs
= current_pt_regs();
234 .si_addr
= (void __user
*)instruction_pointer(regs
),
237 if (WARN_ON(!user_mode(regs
)))
240 if (interrupts_enabled(regs
))
243 force_sig_info(SIGTRAP
, &info
, current
);
246 static int single_step_handler(unsigned long addr
, unsigned int esr
,
247 struct pt_regs
*regs
)
250 * If we are stepping a pending breakpoint, call the hw_breakpoint
253 if (!reinstall_suspended_bps(regs
))
256 if (user_mode(regs
)) {
257 send_user_sigtrap(TRAP_HWBKPT
);
260 * ptrace will disable single step unless explicitly
261 * asked to re-enable it. For other clients, it makes
262 * sense to leave it enabled (i.e. rewind the controls
263 * to the active-not-pending state).
265 user_rewind_single_step(current
);
267 #ifdef CONFIG_KPROBES
268 if (kprobe_single_step_handler(regs
, esr
) == DBG_HOOK_HANDLED
)
271 if (call_step_hook(regs
, esr
) == DBG_HOOK_HANDLED
)
274 pr_warning("Unexpected kernel single-step exception at EL1\n");
276 * Re-enable stepping since we know that we will be
279 set_regs_spsr_ss(regs
);
284 NOKPROBE_SYMBOL(single_step_handler
);
287 * Breakpoint handler is re-entrant as another breakpoint can
288 * hit within breakpoint handler, especically in kprobes.
289 * Use reader/writer locks instead of plain spinlock.
291 static LIST_HEAD(break_hook
);
292 static DEFINE_SPINLOCK(break_hook_lock
);
294 void register_break_hook(struct break_hook
*hook
)
296 spin_lock(&break_hook_lock
);
297 list_add_rcu(&hook
->node
, &break_hook
);
298 spin_unlock(&break_hook_lock
);
301 void unregister_break_hook(struct break_hook
*hook
)
303 spin_lock(&break_hook_lock
);
304 list_del_rcu(&hook
->node
);
305 spin_unlock(&break_hook_lock
);
309 static int call_break_hook(struct pt_regs
*regs
, unsigned int esr
)
311 struct break_hook
*hook
;
312 int (*fn
)(struct pt_regs
*regs
, unsigned int esr
) = NULL
;
315 list_for_each_entry_rcu(hook
, &break_hook
, node
)
316 if ((esr
& hook
->esr_mask
) == hook
->esr_val
)
320 return fn
? fn(regs
, esr
) : DBG_HOOK_ERROR
;
322 NOKPROBE_SYMBOL(call_break_hook
);
324 static int brk_handler(unsigned long addr
, unsigned int esr
,
325 struct pt_regs
*regs
)
327 if (user_mode(regs
)) {
328 send_user_sigtrap(TRAP_BRKPT
);
330 #ifdef CONFIG_KPROBES
331 else if ((esr
& BRK64_ESR_MASK
) == BRK64_ESR_KPROBES
) {
332 if (kprobe_breakpoint_handler(regs
, esr
) != DBG_HOOK_HANDLED
)
336 else if (call_break_hook(regs
, esr
) != DBG_HOOK_HANDLED
) {
337 pr_warn("Unexpected kernel BRK exception at EL1\n");
343 NOKPROBE_SYMBOL(brk_handler
);
345 int aarch32_break_handler(struct pt_regs
*regs
)
350 void __user
*pc
= (void __user
*)instruction_pointer(regs
);
352 if (!compat_user_mode(regs
))
355 if (compat_thumb_mode(regs
)) {
356 /* get 16-bit Thumb instruction */
357 get_user(thumb_instr
, (u16 __user
*)pc
);
358 thumb_instr
= le16_to_cpu(thumb_instr
);
359 if (thumb_instr
== AARCH32_BREAK_THUMB2_LO
) {
360 /* get second half of 32-bit Thumb-2 instruction */
361 get_user(thumb_instr
, (u16 __user
*)(pc
+ 2));
362 thumb_instr
= le16_to_cpu(thumb_instr
);
363 bp
= thumb_instr
== AARCH32_BREAK_THUMB2_HI
;
365 bp
= thumb_instr
== AARCH32_BREAK_THUMB
;
368 /* 32-bit ARM instruction */
369 get_user(arm_instr
, (u32 __user
*)pc
);
370 arm_instr
= le32_to_cpu(arm_instr
);
371 bp
= (arm_instr
& ~0xf0000000) == AARCH32_BREAK_ARM
;
377 send_user_sigtrap(TRAP_BRKPT
);
380 NOKPROBE_SYMBOL(aarch32_break_handler
);
382 static int __init
debug_traps_init(void)
384 hook_debug_fault_code(DBG_ESR_EVT_HWSS
, single_step_handler
, SIGTRAP
,
385 TRAP_HWBKPT
, "single-step handler");
386 hook_debug_fault_code(DBG_ESR_EVT_BRK
, brk_handler
, SIGTRAP
,
387 TRAP_BRKPT
, "ptrace BRK handler");
390 arch_initcall(debug_traps_init
);
392 /* Re-enable single step for syscall restarting. */
393 void user_rewind_single_step(struct task_struct
*task
)
396 * If single step is active for this thread, then set SPSR.SS
397 * to 1 to avoid returning to the active-pending state.
399 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
400 set_regs_spsr_ss(task_pt_regs(task
));
402 NOKPROBE_SYMBOL(user_rewind_single_step
);
404 void user_fastforward_single_step(struct task_struct
*task
)
406 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
407 clear_regs_spsr_ss(task_pt_regs(task
));
411 void kernel_enable_single_step(struct pt_regs
*regs
)
413 WARN_ON(!irqs_disabled());
414 set_regs_spsr_ss(regs
);
415 mdscr_write(mdscr_read() | DBG_MDSCR_SS
);
416 enable_debug_monitors(DBG_ACTIVE_EL1
);
418 NOKPROBE_SYMBOL(kernel_enable_single_step
);
420 void kernel_disable_single_step(void)
422 WARN_ON(!irqs_disabled());
423 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS
);
424 disable_debug_monitors(DBG_ACTIVE_EL1
);
426 NOKPROBE_SYMBOL(kernel_disable_single_step
);
428 int kernel_active_single_step(void)
430 WARN_ON(!irqs_disabled());
431 return mdscr_read() & DBG_MDSCR_SS
;
433 NOKPROBE_SYMBOL(kernel_active_single_step
);
436 void user_enable_single_step(struct task_struct
*task
)
438 struct thread_info
*ti
= task_thread_info(task
);
440 if (!test_and_set_ti_thread_flag(ti
, TIF_SINGLESTEP
))
441 set_regs_spsr_ss(task_pt_regs(task
));
443 NOKPROBE_SYMBOL(user_enable_single_step
);
445 void user_disable_single_step(struct task_struct
*task
)
447 clear_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
);
449 NOKPROBE_SYMBOL(user_disable_single_step
);