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>
28 #include <asm/debug-monitors.h>
29 #include <asm/local.h>
30 #include <asm/cputype.h>
31 #include <asm/system_misc.h>
33 /* Low-level stepping controls. */
34 #define DBG_MDSCR_SS (1 << 0)
35 #define DBG_SPSR_SS (1 << 21)
37 /* MDSCR_EL1 enabling bits */
38 #define DBG_MDSCR_KDE (1 << 13)
39 #define DBG_MDSCR_MDE (1 << 15)
40 #define DBG_MDSCR_MASK ~(DBG_MDSCR_KDE | DBG_MDSCR_MDE)
42 /* Determine debug architecture. */
43 u8
debug_monitors_arch(void)
45 return read_cpuid(ID_AA64DFR0_EL1
) & 0xf;
49 * MDSCR access routines.
51 static void mdscr_write(u32 mdscr
)
54 local_dbg_save(flags
);
55 asm volatile("msr mdscr_el1, %0" :: "r" (mdscr
));
56 local_dbg_restore(flags
);
59 static u32
mdscr_read(void)
62 asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr
));
67 * Allow root to disable self-hosted debug from userspace.
68 * This is useful if you want to connect an external JTAG debugger.
70 static u32 debug_enabled
= 1;
72 static int create_debug_debugfs_entry(void)
74 debugfs_create_bool("debug_enabled", 0644, NULL
, &debug_enabled
);
77 fs_initcall(create_debug_debugfs_entry
);
79 static int __init
early_debug_disable(char *buf
)
85 early_param("nodebugmon", early_debug_disable
);
88 * Keep track of debug users on each core.
89 * The ref counts are per-cpu so we use a local_t type.
91 static DEFINE_PER_CPU(local_t
, mde_ref_count
);
92 static DEFINE_PER_CPU(local_t
, kde_ref_count
);
94 void enable_debug_monitors(enum debug_el el
)
96 u32 mdscr
, enable
= 0;
98 WARN_ON(preemptible());
100 if (local_inc_return(&__get_cpu_var(mde_ref_count
)) == 1)
101 enable
= DBG_MDSCR_MDE
;
103 if (el
== DBG_ACTIVE_EL1
&&
104 local_inc_return(&__get_cpu_var(kde_ref_count
)) == 1)
105 enable
|= DBG_MDSCR_KDE
;
107 if (enable
&& debug_enabled
) {
108 mdscr
= mdscr_read();
114 void disable_debug_monitors(enum debug_el el
)
116 u32 mdscr
, disable
= 0;
118 WARN_ON(preemptible());
120 if (local_dec_and_test(&__get_cpu_var(mde_ref_count
)))
121 disable
= ~DBG_MDSCR_MDE
;
123 if (el
== DBG_ACTIVE_EL1
&&
124 local_dec_and_test(&__get_cpu_var(kde_ref_count
)))
125 disable
&= ~DBG_MDSCR_KDE
;
128 mdscr
= mdscr_read();
137 static void clear_os_lock(void *unused
)
139 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 smp_call_function(clear_os_lock
, NULL
, 1);
162 /* Register hotplug handler. */
163 register_cpu_notifier(&os_lock_nb
);
166 postcore_initcall(debug_monitors_init
);
169 * Single step API and exception handling.
171 static void set_regs_spsr_ss(struct pt_regs
*regs
)
176 spsr
&= ~DBG_SPSR_SS
;
181 static void clear_regs_spsr_ss(struct pt_regs
*regs
)
186 spsr
&= ~DBG_SPSR_SS
;
190 static int single_step_handler(unsigned long addr
, unsigned int esr
,
191 struct pt_regs
*regs
)
196 * If we are stepping a pending breakpoint, call the hw_breakpoint
199 if (!reinstall_suspended_bps(regs
))
202 if (user_mode(regs
)) {
203 info
.si_signo
= SIGTRAP
;
205 info
.si_code
= TRAP_HWBKPT
;
206 info
.si_addr
= (void __user
*)instruction_pointer(regs
);
207 force_sig_info(SIGTRAP
, &info
, current
);
210 * ptrace will disable single step unless explicitly
211 * asked to re-enable it. For other clients, it makes
212 * sense to leave it enabled (i.e. rewind the controls
213 * to the active-not-pending state).
215 user_rewind_single_step(current
);
217 /* TODO: route to KGDB */
218 pr_warning("Unexpected kernel single-step exception at EL1\n");
220 * Re-enable stepping since we know that we will be
223 set_regs_spsr_ss(regs
);
229 static int __init
single_step_init(void)
231 hook_debug_fault_code(DBG_ESR_EVT_HWSS
, single_step_handler
, SIGTRAP
,
232 TRAP_HWBKPT
, "single-step handler");
235 arch_initcall(single_step_init
);
237 /* Re-enable single step for syscall restarting. */
238 void user_rewind_single_step(struct task_struct
*task
)
241 * If single step is active for this thread, then set SPSR.SS
242 * to 1 to avoid returning to the active-pending state.
244 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
245 set_regs_spsr_ss(task_pt_regs(task
));
248 void user_fastforward_single_step(struct task_struct
*task
)
250 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
251 clear_regs_spsr_ss(task_pt_regs(task
));
255 void kernel_enable_single_step(struct pt_regs
*regs
)
257 WARN_ON(!irqs_disabled());
258 set_regs_spsr_ss(regs
);
259 mdscr_write(mdscr_read() | DBG_MDSCR_SS
);
260 enable_debug_monitors(DBG_ACTIVE_EL1
);
263 void kernel_disable_single_step(void)
265 WARN_ON(!irqs_disabled());
266 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS
);
267 disable_debug_monitors(DBG_ACTIVE_EL1
);
270 int kernel_active_single_step(void)
272 WARN_ON(!irqs_disabled());
273 return mdscr_read() & DBG_MDSCR_SS
;
277 void user_enable_single_step(struct task_struct
*task
)
279 set_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
);
280 set_regs_spsr_ss(task_pt_regs(task
));
283 void user_disable_single_step(struct task_struct
*task
)
285 clear_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
);