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/cpufeature.h>
30 #include <asm/cputype.h>
31 #include <asm/debug-monitors.h>
32 #include <asm/system_misc.h>
34 /* Determine debug architecture. */
35 u8
debug_monitors_arch(void)
37 return cpuid_feature_extract_field(read_system_reg(SYS_ID_AA64DFR0_EL1
),
38 ID_AA64DFR0_DEBUGVER_SHIFT
);
42 * MDSCR access routines.
44 static void mdscr_write(u32 mdscr
)
47 local_dbg_save(flags
);
48 asm volatile("msr mdscr_el1, %0" :: "r" (mdscr
));
49 local_dbg_restore(flags
);
52 static u32
mdscr_read(void)
55 asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr
));
60 * Allow root to disable self-hosted debug from userspace.
61 * This is useful if you want to connect an external JTAG debugger.
63 static bool debug_enabled
= true;
65 static int create_debug_debugfs_entry(void)
67 debugfs_create_bool("debug_enabled", 0644, NULL
, &debug_enabled
);
70 fs_initcall(create_debug_debugfs_entry
);
72 static int __init
early_debug_disable(char *buf
)
74 debug_enabled
= false;
78 early_param("nodebugmon", early_debug_disable
);
81 * Keep track of debug users on each core.
82 * The ref counts are per-cpu so we use a local_t type.
84 static DEFINE_PER_CPU(int, mde_ref_count
);
85 static DEFINE_PER_CPU(int, kde_ref_count
);
87 void enable_debug_monitors(enum dbg_active_el el
)
89 u32 mdscr
, enable
= 0;
91 WARN_ON(preemptible());
93 if (this_cpu_inc_return(mde_ref_count
) == 1)
94 enable
= DBG_MDSCR_MDE
;
96 if (el
== DBG_ACTIVE_EL1
&&
97 this_cpu_inc_return(kde_ref_count
) == 1)
98 enable
|= DBG_MDSCR_KDE
;
100 if (enable
&& debug_enabled
) {
101 mdscr
= mdscr_read();
107 void disable_debug_monitors(enum dbg_active_el el
)
109 u32 mdscr
, disable
= 0;
111 WARN_ON(preemptible());
113 if (this_cpu_dec_return(mde_ref_count
) == 0)
114 disable
= ~DBG_MDSCR_MDE
;
116 if (el
== DBG_ACTIVE_EL1
&&
117 this_cpu_dec_return(kde_ref_count
) == 0)
118 disable
&= ~DBG_MDSCR_KDE
;
121 mdscr
= mdscr_read();
130 static void clear_os_lock(void *unused
)
132 asm volatile("msr oslar_el1, %0" : : "r" (0));
135 static int os_lock_notify(struct notifier_block
*self
,
136 unsigned long action
, void *data
)
138 int cpu
= (unsigned long)data
;
139 if ((action
& ~CPU_TASKS_FROZEN
) == CPU_ONLINE
)
140 smp_call_function_single(cpu
, clear_os_lock
, NULL
, 1);
144 static struct notifier_block os_lock_nb
= {
145 .notifier_call
= os_lock_notify
,
148 static int debug_monitors_init(void)
150 cpu_notifier_register_begin();
152 /* Clear the OS lock. */
153 on_each_cpu(clear_os_lock
, NULL
, 1);
157 /* Register hotplug handler. */
158 __register_cpu_notifier(&os_lock_nb
);
160 cpu_notifier_register_done();
163 postcore_initcall(debug_monitors_init
);
166 * Single step API and exception handling.
168 static void set_regs_spsr_ss(struct pt_regs
*regs
)
173 spsr
&= ~DBG_SPSR_SS
;
178 static void clear_regs_spsr_ss(struct pt_regs
*regs
)
183 spsr
&= ~DBG_SPSR_SS
;
187 /* EL1 Single Step Handler hooks */
188 static LIST_HEAD(step_hook
);
189 static DEFINE_RWLOCK(step_hook_lock
);
191 void register_step_hook(struct step_hook
*hook
)
193 write_lock(&step_hook_lock
);
194 list_add(&hook
->node
, &step_hook
);
195 write_unlock(&step_hook_lock
);
198 void unregister_step_hook(struct step_hook
*hook
)
200 write_lock(&step_hook_lock
);
201 list_del(&hook
->node
);
202 write_unlock(&step_hook_lock
);
206 * Call registered single step handlers
207 * There is no Syndrome info to check for determining the handler.
208 * So we call all the registered handlers, until the right handler is
209 * found which returns zero.
211 static int call_step_hook(struct pt_regs
*regs
, unsigned int esr
)
213 struct step_hook
*hook
;
214 int retval
= DBG_HOOK_ERROR
;
216 read_lock(&step_hook_lock
);
218 list_for_each_entry(hook
, &step_hook
, node
) {
219 retval
= hook
->fn(regs
, esr
);
220 if (retval
== DBG_HOOK_HANDLED
)
224 read_unlock(&step_hook_lock
);
229 static int single_step_handler(unsigned long addr
, unsigned int esr
,
230 struct pt_regs
*regs
)
235 * If we are stepping a pending breakpoint, call the hw_breakpoint
238 if (!reinstall_suspended_bps(regs
))
241 if (user_mode(regs
)) {
242 info
.si_signo
= SIGTRAP
;
244 info
.si_code
= TRAP_HWBKPT
;
245 info
.si_addr
= (void __user
*)instruction_pointer(regs
);
246 force_sig_info(SIGTRAP
, &info
, current
);
249 * ptrace will disable single step unless explicitly
250 * asked to re-enable it. For other clients, it makes
251 * sense to leave it enabled (i.e. rewind the controls
252 * to the active-not-pending state).
254 user_rewind_single_step(current
);
256 if (call_step_hook(regs
, esr
) == DBG_HOOK_HANDLED
)
259 pr_warning("Unexpected kernel single-step exception at EL1\n");
261 * Re-enable stepping since we know that we will be
264 set_regs_spsr_ss(regs
);
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
;
307 static int brk_handler(unsigned long addr
, unsigned int esr
,
308 struct pt_regs
*regs
)
312 if (user_mode(regs
)) {
316 .si_code
= TRAP_BRKPT
,
317 .si_addr
= (void __user
*)instruction_pointer(regs
),
320 force_sig_info(SIGTRAP
, &info
, current
);
321 } else if (call_break_hook(regs
, esr
) != DBG_HOOK_HANDLED
) {
322 pr_warning("Unexpected kernel BRK exception at EL1\n");
329 int aarch32_break_handler(struct pt_regs
*regs
)
335 void __user
*pc
= (void __user
*)instruction_pointer(regs
);
337 if (!compat_user_mode(regs
))
340 if (compat_thumb_mode(regs
)) {
341 /* get 16-bit Thumb instruction */
342 get_user(thumb_instr
, (u16 __user
*)pc
);
343 thumb_instr
= le16_to_cpu(thumb_instr
);
344 if (thumb_instr
== AARCH32_BREAK_THUMB2_LO
) {
345 /* get second half of 32-bit Thumb-2 instruction */
346 get_user(thumb_instr
, (u16 __user
*)(pc
+ 2));
347 thumb_instr
= le16_to_cpu(thumb_instr
);
348 bp
= thumb_instr
== AARCH32_BREAK_THUMB2_HI
;
350 bp
= thumb_instr
== AARCH32_BREAK_THUMB
;
353 /* 32-bit ARM instruction */
354 get_user(arm_instr
, (u32 __user
*)pc
);
355 arm_instr
= le32_to_cpu(arm_instr
);
356 bp
= (arm_instr
& ~0xf0000000) == AARCH32_BREAK_ARM
;
365 .si_code
= TRAP_BRKPT
,
369 force_sig_info(SIGTRAP
, &info
, current
);
373 static int __init
debug_traps_init(void)
375 hook_debug_fault_code(DBG_ESR_EVT_HWSS
, single_step_handler
, SIGTRAP
,
376 TRAP_HWBKPT
, "single-step handler");
377 hook_debug_fault_code(DBG_ESR_EVT_BRK
, brk_handler
, SIGTRAP
,
378 TRAP_BRKPT
, "ptrace BRK handler");
381 arch_initcall(debug_traps_init
);
383 /* Re-enable single step for syscall restarting. */
384 void user_rewind_single_step(struct task_struct
*task
)
387 * If single step is active for this thread, then set SPSR.SS
388 * to 1 to avoid returning to the active-pending state.
390 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
391 set_regs_spsr_ss(task_pt_regs(task
));
394 void user_fastforward_single_step(struct task_struct
*task
)
396 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
397 clear_regs_spsr_ss(task_pt_regs(task
));
401 void kernel_enable_single_step(struct pt_regs
*regs
)
403 WARN_ON(!irqs_disabled());
404 set_regs_spsr_ss(regs
);
405 mdscr_write(mdscr_read() | DBG_MDSCR_SS
);
406 enable_debug_monitors(DBG_ACTIVE_EL1
);
409 void kernel_disable_single_step(void)
411 WARN_ON(!irqs_disabled());
412 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS
);
413 disable_debug_monitors(DBG_ACTIVE_EL1
);
416 int kernel_active_single_step(void)
418 WARN_ON(!irqs_disabled());
419 return mdscr_read() & DBG_MDSCR_SS
;
423 void user_enable_single_step(struct task_struct
*task
)
425 set_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
);
426 set_regs_spsr_ss(task_pt_regs(task
));
429 void user_disable_single_step(struct task_struct
*task
)
431 clear_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
);