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 (user_mode(regs
)) {
319 .si_code
= TRAP_BRKPT
,
320 .si_addr
= (void __user
*)instruction_pointer(regs
),
323 force_sig_info(SIGTRAP
, &info
, current
);
324 } else if (call_break_hook(regs
, esr
) != DBG_HOOK_HANDLED
) {
325 pr_warning("Unexpected kernel BRK exception at EL1\n");
332 int aarch32_break_handler(struct pt_regs
*regs
)
337 void __user
*pc
= (void __user
*)instruction_pointer(regs
);
339 if (!compat_user_mode(regs
))
342 if (compat_thumb_mode(regs
)) {
343 /* get 16-bit Thumb instruction */
344 get_user(instr
, (u16 __user
*)pc
);
345 if (instr
== AARCH32_BREAK_THUMB2_LO
) {
346 /* get second half of 32-bit Thumb-2 instruction */
347 get_user(instr
, (u16 __user
*)(pc
+ 2));
348 bp
= instr
== AARCH32_BREAK_THUMB2_HI
;
350 bp
= instr
== AARCH32_BREAK_THUMB
;
353 /* 32-bit ARM instruction */
354 get_user(instr
, (u32 __user
*)pc
);
355 bp
= (instr
& ~0xf0000000) == AARCH32_BREAK_ARM
;
364 .si_code
= TRAP_BRKPT
,
368 force_sig_info(SIGTRAP
, &info
, current
);
372 static int __init
debug_traps_init(void)
374 hook_debug_fault_code(DBG_ESR_EVT_HWSS
, single_step_handler
, SIGTRAP
,
375 TRAP_HWBKPT
, "single-step handler");
376 hook_debug_fault_code(DBG_ESR_EVT_BRK
, brk_handler
, SIGTRAP
,
377 TRAP_BRKPT
, "ptrace BRK handler");
380 arch_initcall(debug_traps_init
);
382 /* Re-enable single step for syscall restarting. */
383 void user_rewind_single_step(struct task_struct
*task
)
386 * If single step is active for this thread, then set SPSR.SS
387 * to 1 to avoid returning to the active-pending state.
389 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
390 set_regs_spsr_ss(task_pt_regs(task
));
393 void user_fastforward_single_step(struct task_struct
*task
)
395 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
396 clear_regs_spsr_ss(task_pt_regs(task
));
400 void kernel_enable_single_step(struct pt_regs
*regs
)
402 WARN_ON(!irqs_disabled());
403 set_regs_spsr_ss(regs
);
404 mdscr_write(mdscr_read() | DBG_MDSCR_SS
);
405 enable_debug_monitors(DBG_ACTIVE_EL1
);
408 void kernel_disable_single_step(void)
410 WARN_ON(!irqs_disabled());
411 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS
);
412 disable_debug_monitors(DBG_ACTIVE_EL1
);
415 int kernel_active_single_step(void)
417 WARN_ON(!irqs_disabled());
418 return mdscr_read() & DBG_MDSCR_SS
;
422 void user_enable_single_step(struct task_struct
*task
)
424 set_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
);
425 set_regs_spsr_ss(task_pt_regs(task
));
428 void user_disable_single_step(struct task_struct
*task
)
430 clear_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
);