1 // SPDX-License-Identifier: GPL-2.0-only
3 * ARMv8 single-step debug support and mdscr context switching.
5 * Copyright (C) 2012 ARM Limited
7 * Author: Will Deacon <will.deacon@arm.com>
10 #include <linux/cpu.h>
11 #include <linux/debugfs.h>
12 #include <linux/hardirq.h>
13 #include <linux/init.h>
14 #include <linux/ptrace.h>
15 #include <linux/kprobes.h>
16 #include <linux/stat.h>
17 #include <linux/uaccess.h>
18 #include <linux/sched/task_stack.h>
20 #include <asm/cpufeature.h>
21 #include <asm/cputype.h>
22 #include <asm/daifflags.h>
23 #include <asm/debug-monitors.h>
24 #include <asm/system_misc.h>
25 #include <asm/traps.h>
27 /* Determine debug architecture. */
28 u8
debug_monitors_arch(void)
30 return cpuid_feature_extract_unsigned_field(read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1
),
31 ID_AA64DFR0_DEBUGVER_SHIFT
);
35 * MDSCR access routines.
37 static void mdscr_write(u32 mdscr
)
40 flags
= local_daif_save();
41 write_sysreg(mdscr
, mdscr_el1
);
42 local_daif_restore(flags
);
44 NOKPROBE_SYMBOL(mdscr_write
);
46 static u32
mdscr_read(void)
48 return read_sysreg(mdscr_el1
);
50 NOKPROBE_SYMBOL(mdscr_read
);
53 * Allow root to disable self-hosted debug from userspace.
54 * This is useful if you want to connect an external JTAG debugger.
56 static bool debug_enabled
= true;
58 static int create_debug_debugfs_entry(void)
60 debugfs_create_bool("debug_enabled", 0644, NULL
, &debug_enabled
);
63 fs_initcall(create_debug_debugfs_entry
);
65 static int __init
early_debug_disable(char *buf
)
67 debug_enabled
= false;
71 early_param("nodebugmon", early_debug_disable
);
74 * Keep track of debug users on each core.
75 * The ref counts are per-cpu so we use a local_t type.
77 static DEFINE_PER_CPU(int, mde_ref_count
);
78 static DEFINE_PER_CPU(int, kde_ref_count
);
80 void enable_debug_monitors(enum dbg_active_el el
)
82 u32 mdscr
, enable
= 0;
84 WARN_ON(preemptible());
86 if (this_cpu_inc_return(mde_ref_count
) == 1)
87 enable
= DBG_MDSCR_MDE
;
89 if (el
== DBG_ACTIVE_EL1
&&
90 this_cpu_inc_return(kde_ref_count
) == 1)
91 enable
|= DBG_MDSCR_KDE
;
93 if (enable
&& debug_enabled
) {
99 NOKPROBE_SYMBOL(enable_debug_monitors
);
101 void disable_debug_monitors(enum dbg_active_el el
)
103 u32 mdscr
, disable
= 0;
105 WARN_ON(preemptible());
107 if (this_cpu_dec_return(mde_ref_count
) == 0)
108 disable
= ~DBG_MDSCR_MDE
;
110 if (el
== DBG_ACTIVE_EL1
&&
111 this_cpu_dec_return(kde_ref_count
) == 0)
112 disable
&= ~DBG_MDSCR_KDE
;
115 mdscr
= mdscr_read();
120 NOKPROBE_SYMBOL(disable_debug_monitors
);
125 static int clear_os_lock(unsigned int cpu
)
127 write_sysreg(0, osdlr_el1
);
128 write_sysreg(0, oslar_el1
);
133 static int debug_monitors_init(void)
135 return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING
,
136 "arm64/debug_monitors:starting",
137 clear_os_lock
, NULL
);
139 postcore_initcall(debug_monitors_init
);
142 * Single step API and exception handling.
144 static void set_regs_spsr_ss(struct pt_regs
*regs
)
146 regs
->pstate
|= DBG_SPSR_SS
;
148 NOKPROBE_SYMBOL(set_regs_spsr_ss
);
150 static void clear_regs_spsr_ss(struct pt_regs
*regs
)
152 regs
->pstate
&= ~DBG_SPSR_SS
;
154 NOKPROBE_SYMBOL(clear_regs_spsr_ss
);
156 static DEFINE_SPINLOCK(debug_hook_lock
);
157 static LIST_HEAD(user_step_hook
);
158 static LIST_HEAD(kernel_step_hook
);
160 static void register_debug_hook(struct list_head
*node
, struct list_head
*list
)
162 spin_lock(&debug_hook_lock
);
163 list_add_rcu(node
, list
);
164 spin_unlock(&debug_hook_lock
);
168 static void unregister_debug_hook(struct list_head
*node
)
170 spin_lock(&debug_hook_lock
);
172 spin_unlock(&debug_hook_lock
);
176 void register_user_step_hook(struct step_hook
*hook
)
178 register_debug_hook(&hook
->node
, &user_step_hook
);
181 void unregister_user_step_hook(struct step_hook
*hook
)
183 unregister_debug_hook(&hook
->node
);
186 void register_kernel_step_hook(struct step_hook
*hook
)
188 register_debug_hook(&hook
->node
, &kernel_step_hook
);
191 void unregister_kernel_step_hook(struct step_hook
*hook
)
193 unregister_debug_hook(&hook
->node
);
197 * Call registered single step handlers
198 * There is no Syndrome info to check for determining the handler.
199 * So we call all the registered handlers, until the right handler is
200 * found which returns zero.
202 static int call_step_hook(struct pt_regs
*regs
, unsigned int esr
)
204 struct step_hook
*hook
;
205 struct list_head
*list
;
206 int retval
= DBG_HOOK_ERROR
;
208 list
= user_mode(regs
) ? &user_step_hook
: &kernel_step_hook
;
212 list_for_each_entry_rcu(hook
, list
, node
) {
213 retval
= hook
->fn(regs
, esr
);
214 if (retval
== DBG_HOOK_HANDLED
)
222 NOKPROBE_SYMBOL(call_step_hook
);
224 static void send_user_sigtrap(int si_code
)
226 struct pt_regs
*regs
= current_pt_regs();
228 if (WARN_ON(!user_mode(regs
)))
231 if (interrupts_enabled(regs
))
234 arm64_force_sig_fault(SIGTRAP
, si_code
,
235 (void __user
*)instruction_pointer(regs
),
239 static int single_step_handler(unsigned long unused
, unsigned int esr
,
240 struct pt_regs
*regs
)
242 bool handler_found
= false;
245 * If we are stepping a pending breakpoint, call the hw_breakpoint
248 if (!reinstall_suspended_bps(regs
))
251 if (!handler_found
&& call_step_hook(regs
, esr
) == DBG_HOOK_HANDLED
)
252 handler_found
= true;
254 if (!handler_found
&& user_mode(regs
)) {
255 send_user_sigtrap(TRAP_TRACE
);
258 * ptrace will disable single step unless explicitly
259 * asked to re-enable it. For other clients, it makes
260 * sense to leave it enabled (i.e. rewind the controls
261 * to the active-not-pending state).
263 user_rewind_single_step(current
);
264 } else if (!handler_found
) {
265 pr_warn("Unexpected kernel single-step exception at EL1\n");
267 * Re-enable stepping since we know that we will be
270 set_regs_spsr_ss(regs
);
275 NOKPROBE_SYMBOL(single_step_handler
);
277 static LIST_HEAD(user_break_hook
);
278 static LIST_HEAD(kernel_break_hook
);
280 void register_user_break_hook(struct break_hook
*hook
)
282 register_debug_hook(&hook
->node
, &user_break_hook
);
285 void unregister_user_break_hook(struct break_hook
*hook
)
287 unregister_debug_hook(&hook
->node
);
290 void register_kernel_break_hook(struct break_hook
*hook
)
292 register_debug_hook(&hook
->node
, &kernel_break_hook
);
295 void unregister_kernel_break_hook(struct break_hook
*hook
)
297 unregister_debug_hook(&hook
->node
);
300 static int call_break_hook(struct pt_regs
*regs
, unsigned int esr
)
302 struct break_hook
*hook
;
303 struct list_head
*list
;
304 int (*fn
)(struct pt_regs
*regs
, unsigned int esr
) = NULL
;
306 list
= user_mode(regs
) ? &user_break_hook
: &kernel_break_hook
;
309 list_for_each_entry_rcu(hook
, list
, node
) {
310 unsigned int comment
= esr
& ESR_ELx_BRK64_ISS_COMMENT_MASK
;
312 if ((comment
& ~hook
->mask
) == hook
->imm
)
317 return fn
? fn(regs
, esr
) : DBG_HOOK_ERROR
;
319 NOKPROBE_SYMBOL(call_break_hook
);
321 static int brk_handler(unsigned long unused
, unsigned int esr
,
322 struct pt_regs
*regs
)
324 if (call_break_hook(regs
, esr
) == DBG_HOOK_HANDLED
)
327 if (user_mode(regs
)) {
328 send_user_sigtrap(TRAP_BRKPT
);
330 pr_warn("Unexpected kernel BRK exception at EL1\n");
336 NOKPROBE_SYMBOL(brk_handler
);
338 int aarch32_break_handler(struct pt_regs
*regs
)
343 void __user
*pc
= (void __user
*)instruction_pointer(regs
);
345 if (!compat_user_mode(regs
))
348 if (compat_thumb_mode(regs
)) {
349 /* get 16-bit Thumb instruction */
351 get_user(instr
, (__le16 __user
*)pc
);
352 thumb_instr
= le16_to_cpu(instr
);
353 if (thumb_instr
== AARCH32_BREAK_THUMB2_LO
) {
354 /* get second half of 32-bit Thumb-2 instruction */
355 get_user(instr
, (__le16 __user
*)(pc
+ 2));
356 thumb_instr
= le16_to_cpu(instr
);
357 bp
= thumb_instr
== AARCH32_BREAK_THUMB2_HI
;
359 bp
= thumb_instr
== AARCH32_BREAK_THUMB
;
362 /* 32-bit ARM instruction */
364 get_user(instr
, (__le32 __user
*)pc
);
365 arm_instr
= le32_to_cpu(instr
);
366 bp
= (arm_instr
& ~0xf0000000) == AARCH32_BREAK_ARM
;
372 send_user_sigtrap(TRAP_BRKPT
);
375 NOKPROBE_SYMBOL(aarch32_break_handler
);
377 static int __init
debug_traps_init(void)
379 hook_debug_fault_code(DBG_ESR_EVT_HWSS
, single_step_handler
, SIGTRAP
,
380 TRAP_TRACE
, "single-step handler");
381 hook_debug_fault_code(DBG_ESR_EVT_BRK
, brk_handler
, SIGTRAP
,
382 TRAP_BRKPT
, "ptrace BRK handler");
385 arch_initcall(debug_traps_init
);
387 /* Re-enable single step for syscall restarting. */
388 void user_rewind_single_step(struct task_struct
*task
)
391 * If single step is active for this thread, then set SPSR.SS
392 * to 1 to avoid returning to the active-pending state.
394 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
395 set_regs_spsr_ss(task_pt_regs(task
));
397 NOKPROBE_SYMBOL(user_rewind_single_step
);
399 void user_fastforward_single_step(struct task_struct
*task
)
401 if (test_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
))
402 clear_regs_spsr_ss(task_pt_regs(task
));
406 void kernel_enable_single_step(struct pt_regs
*regs
)
408 WARN_ON(!irqs_disabled());
409 set_regs_spsr_ss(regs
);
410 mdscr_write(mdscr_read() | DBG_MDSCR_SS
);
411 enable_debug_monitors(DBG_ACTIVE_EL1
);
413 NOKPROBE_SYMBOL(kernel_enable_single_step
);
415 void kernel_disable_single_step(void)
417 WARN_ON(!irqs_disabled());
418 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS
);
419 disable_debug_monitors(DBG_ACTIVE_EL1
);
421 NOKPROBE_SYMBOL(kernel_disable_single_step
);
423 int kernel_active_single_step(void)
425 WARN_ON(!irqs_disabled());
426 return mdscr_read() & DBG_MDSCR_SS
;
428 NOKPROBE_SYMBOL(kernel_active_single_step
);
431 void user_enable_single_step(struct task_struct
*task
)
433 struct thread_info
*ti
= task_thread_info(task
);
435 if (!test_and_set_ti_thread_flag(ti
, TIF_SINGLESTEP
))
436 set_regs_spsr_ss(task_pt_regs(task
));
438 NOKPROBE_SYMBOL(user_enable_single_step
);
440 void user_disable_single_step(struct task_struct
*task
)
442 clear_ti_thread_flag(task_thread_info(task
), TIF_SINGLESTEP
);
444 NOKPROBE_SYMBOL(user_disable_single_step
);