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2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10 * GNU General Public License for more details.
12 * You should have received a copy of the GNU General Public License
13 * along with this program; if not, write to the Free Software
14 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
16 * Copyright (C) 2007 Alan Stern
17 * Copyright (C) 2009 IBM Corporation
18 * Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
20 * Authors: Alan Stern <stern@rowland.harvard.edu>
21 * K.Prasad <prasad@linux.vnet.ibm.com>
22 * Frederic Weisbecker <fweisbec@gmail.com>
26 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
27 * using the CPU's debug registers.
30 #include <linux/perf_event.h>
31 #include <linux/hw_breakpoint.h>
32 #include <linux/irqflags.h>
33 #include <linux/notifier.h>
34 #include <linux/kallsyms.h>
35 #include <linux/kprobes.h>
36 #include <linux/percpu.h>
37 #include <linux/kdebug.h>
38 #include <linux/kernel.h>
39 #include <linux/module.h>
40 #include <linux/sched.h>
41 #include <linux/init.h>
42 #include <linux/smp.h>
44 #include <asm/hw_breakpoint.h>
45 #include <asm/processor.h>
46 #include <asm/debugreg.h>
48 /* Per cpu debug control register value */
49 DEFINE_PER_CPU(unsigned long, cpu_dr7
);
50 EXPORT_PER_CPU_SYMBOL(cpu_dr7
);
52 /* Per cpu debug address registers values */
53 static DEFINE_PER_CPU(unsigned long, cpu_debugreg
[HBP_NUM
]);
56 * Stores the breakpoints currently in use on each breakpoint address
57 * register for each cpus
59 static DEFINE_PER_CPU(struct perf_event
*, bp_per_reg
[HBP_NUM
]);
62 static inline unsigned long
63 __encode_dr7(int drnum
, unsigned int len
, unsigned int type
)
65 unsigned long bp_info
;
67 bp_info
= (len
| type
) & 0xf;
68 bp_info
<<= (DR_CONTROL_SHIFT
+ drnum
* DR_CONTROL_SIZE
);
69 bp_info
|= (DR_GLOBAL_ENABLE
<< (drnum
* DR_ENABLE_SIZE
));
75 * Encode the length, type, Exact, and Enable bits for a particular breakpoint
76 * as stored in debug register 7.
78 unsigned long encode_dr7(int drnum
, unsigned int len
, unsigned int type
)
80 return __encode_dr7(drnum
, len
, type
) | DR_GLOBAL_SLOWDOWN
;
84 * Decode the length and type bits for a particular breakpoint as
85 * stored in debug register 7. Return the "enabled" status.
87 int decode_dr7(unsigned long dr7
, int bpnum
, unsigned *len
, unsigned *type
)
89 int bp_info
= dr7
>> (DR_CONTROL_SHIFT
+ bpnum
* DR_CONTROL_SIZE
);
91 *len
= (bp_info
& 0xc) | 0x40;
92 *type
= (bp_info
& 0x3) | 0x80;
94 return (dr7
>> (bpnum
* DR_ENABLE_SIZE
)) & 0x3;
98 * Install a perf counter breakpoint.
100 * We seek a free debug address register and use it for this
101 * breakpoint. Eventually we enable it in the debug control register.
103 * Atomic: we hold the counter->ctx->lock and we only handle variables
104 * and registers local to this cpu.
106 int arch_install_hw_breakpoint(struct perf_event
*bp
)
108 struct arch_hw_breakpoint
*info
= counter_arch_bp(bp
);
112 for (i
= 0; i
< HBP_NUM
; i
++) {
113 struct perf_event
**slot
= &__get_cpu_var(bp_per_reg
[i
]);
121 if (WARN_ONCE(i
== HBP_NUM
, "Can't find any breakpoint slot"))
124 set_debugreg(info
->address
, i
);
125 __get_cpu_var(cpu_debugreg
[i
]) = info
->address
;
127 dr7
= &__get_cpu_var(cpu_dr7
);
128 *dr7
|= encode_dr7(i
, info
->len
, info
->type
);
130 set_debugreg(*dr7
, 7);
136 * Uninstall the breakpoint contained in the given counter.
138 * First we search the debug address register it uses and then we disable
141 * Atomic: we hold the counter->ctx->lock and we only handle variables
142 * and registers local to this cpu.
144 void arch_uninstall_hw_breakpoint(struct perf_event
*bp
)
146 struct arch_hw_breakpoint
*info
= counter_arch_bp(bp
);
150 for (i
= 0; i
< HBP_NUM
; i
++) {
151 struct perf_event
**slot
= &__get_cpu_var(bp_per_reg
[i
]);
159 if (WARN_ONCE(i
== HBP_NUM
, "Can't find any breakpoint slot"))
162 dr7
= &__get_cpu_var(cpu_dr7
);
163 *dr7
&= ~__encode_dr7(i
, info
->len
, info
->type
);
165 set_debugreg(*dr7
, 7);
168 static int get_hbp_len(u8 hbp_len
)
170 unsigned int len_in_bytes
= 0;
173 case X86_BREAKPOINT_LEN_1
:
176 case X86_BREAKPOINT_LEN_2
:
179 case X86_BREAKPOINT_LEN_4
:
183 case X86_BREAKPOINT_LEN_8
:
192 * Check for virtual address in user space.
194 int arch_check_va_in_userspace(unsigned long va
, u8 hbp_len
)
198 len
= get_hbp_len(hbp_len
);
200 return (va
<= TASK_SIZE
- len
);
204 * Check for virtual address in kernel space.
206 static int arch_check_va_in_kernelspace(unsigned long va
, u8 hbp_len
)
210 len
= get_hbp_len(hbp_len
);
212 return (va
>= TASK_SIZE
) && ((va
+ len
- 1) >= TASK_SIZE
);
215 int arch_bp_generic_fields(int x86_len
, int x86_type
,
216 int *gen_len
, int *gen_type
)
220 case X86_BREAKPOINT_LEN_1
:
221 *gen_len
= HW_BREAKPOINT_LEN_1
;
223 case X86_BREAKPOINT_LEN_2
:
224 *gen_len
= HW_BREAKPOINT_LEN_2
;
226 case X86_BREAKPOINT_LEN_4
:
227 *gen_len
= HW_BREAKPOINT_LEN_4
;
230 case X86_BREAKPOINT_LEN_8
:
231 *gen_len
= HW_BREAKPOINT_LEN_8
;
240 case X86_BREAKPOINT_EXECUTE
:
241 *gen_type
= HW_BREAKPOINT_X
;
243 case X86_BREAKPOINT_WRITE
:
244 *gen_type
= HW_BREAKPOINT_W
;
246 case X86_BREAKPOINT_RW
:
247 *gen_type
= HW_BREAKPOINT_W
| HW_BREAKPOINT_R
;
257 static int arch_build_bp_info(struct perf_event
*bp
)
259 struct arch_hw_breakpoint
*info
= counter_arch_bp(bp
);
261 info
->address
= bp
->attr
.bp_addr
;
264 switch (bp
->attr
.bp_len
) {
265 case HW_BREAKPOINT_LEN_1
:
266 info
->len
= X86_BREAKPOINT_LEN_1
;
268 case HW_BREAKPOINT_LEN_2
:
269 info
->len
= X86_BREAKPOINT_LEN_2
;
271 case HW_BREAKPOINT_LEN_4
:
272 info
->len
= X86_BREAKPOINT_LEN_4
;
275 case HW_BREAKPOINT_LEN_8
:
276 info
->len
= X86_BREAKPOINT_LEN_8
;
284 switch (bp
->attr
.bp_type
) {
285 case HW_BREAKPOINT_W
:
286 info
->type
= X86_BREAKPOINT_WRITE
;
288 case HW_BREAKPOINT_W
| HW_BREAKPOINT_R
:
289 info
->type
= X86_BREAKPOINT_RW
;
291 case HW_BREAKPOINT_X
:
292 info
->type
= X86_BREAKPOINT_EXECUTE
;
301 * Validate the arch-specific HW Breakpoint register settings
303 int arch_validate_hwbkpt_settings(struct perf_event
*bp
,
304 struct task_struct
*tsk
)
306 struct arch_hw_breakpoint
*info
= counter_arch_bp(bp
);
311 ret
= arch_build_bp_info(bp
);
317 if (info
->type
== X86_BREAKPOINT_EXECUTE
)
319 * Ptrace-refactoring code
320 * For now, we'll allow instruction breakpoint only for user-space
323 if ((!arch_check_va_in_userspace(info
->address
, info
->len
)) &&
324 info
->len
!= X86_BREAKPOINT_EXECUTE
)
328 case X86_BREAKPOINT_LEN_1
:
331 case X86_BREAKPOINT_LEN_2
:
334 case X86_BREAKPOINT_LEN_4
:
338 case X86_BREAKPOINT_LEN_8
:
347 * For kernel-addresses, either the address or symbol name can be
351 info
->address
= (unsigned long)
352 kallsyms_lookup_name(info
->name
);
354 * Check that the low-order bits of the address are appropriate
355 * for the alignment implied by len.
357 if (info
->address
& align
)
360 /* Check that the virtual address is in the proper range */
362 if (!arch_check_va_in_userspace(info
->address
, info
->len
))
365 if (!arch_check_va_in_kernelspace(info
->address
, info
->len
))
373 * Dump the debug register contents to the user.
374 * We can't dump our per cpu values because it
375 * may contain cpu wide breakpoint, something that
376 * doesn't belong to the current task.
378 * TODO: include non-ptrace user breakpoints (perf)
380 void aout_dump_debugregs(struct user
*dump
)
384 struct perf_event
*bp
;
385 struct arch_hw_breakpoint
*info
;
386 struct thread_struct
*thread
= ¤t
->thread
;
388 for (i
= 0; i
< HBP_NUM
; i
++) {
389 bp
= thread
->ptrace_bps
[i
];
391 if (bp
&& !bp
->attr
.disabled
) {
392 dump
->u_debugreg
[i
] = bp
->attr
.bp_addr
;
393 info
= counter_arch_bp(bp
);
394 dr7
|= encode_dr7(i
, info
->len
, info
->type
);
396 dump
->u_debugreg
[i
] = 0;
400 dump
->u_debugreg
[4] = 0;
401 dump
->u_debugreg
[5] = 0;
402 dump
->u_debugreg
[6] = current
->thread
.debugreg6
;
404 dump
->u_debugreg
[7] = dr7
;
406 EXPORT_SYMBOL_GPL(aout_dump_debugregs
);
409 * Release the user breakpoints used by ptrace
411 void flush_ptrace_hw_breakpoint(struct task_struct
*tsk
)
414 struct thread_struct
*t
= &tsk
->thread
;
416 for (i
= 0; i
< HBP_NUM
; i
++) {
417 unregister_hw_breakpoint(t
->ptrace_bps
[i
]);
418 t
->ptrace_bps
[i
] = NULL
;
422 void hw_breakpoint_restore(void)
424 set_debugreg(__get_cpu_var(cpu_debugreg
[0]), 0);
425 set_debugreg(__get_cpu_var(cpu_debugreg
[1]), 1);
426 set_debugreg(__get_cpu_var(cpu_debugreg
[2]), 2);
427 set_debugreg(__get_cpu_var(cpu_debugreg
[3]), 3);
428 set_debugreg(current
->thread
.debugreg6
, 6);
429 set_debugreg(__get_cpu_var(cpu_dr7
), 7);
431 EXPORT_SYMBOL_GPL(hw_breakpoint_restore
);
434 * Handle debug exception notifications.
436 * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
438 * NOTIFY_DONE returned if one of the following conditions is true.
439 * i) When the causative address is from user-space and the exception
440 * is a valid one, i.e. not triggered as a result of lazy debug register
442 * ii) When there are more bits than trap<n> set in DR6 register (such
443 * as BD, BS or BT) indicating that more than one debug condition is
444 * met and requires some more action in do_debug().
446 * NOTIFY_STOP returned for all other cases
449 static int __kprobes
hw_breakpoint_handler(struct die_args
*args
)
451 int i
, cpu
, rc
= NOTIFY_STOP
;
452 struct perf_event
*bp
;
453 unsigned long dr7
, dr6
;
454 unsigned long *dr6_p
;
456 /* The DR6 value is pointed by args->err */
457 dr6_p
= (unsigned long *)ERR_PTR(args
->err
);
460 /* Do an early return if no trap bits are set in DR6 */
461 if ((dr6
& DR_TRAP_BITS
) == 0)
464 get_debugreg(dr7
, 7);
465 /* Disable breakpoints during exception handling */
466 set_debugreg(0UL, 7);
468 * Assert that local interrupts are disabled
469 * Reset the DRn bits in the virtualized register value.
470 * The ptrace trigger routine will add in whatever is needed.
472 current
->thread
.debugreg6
&= ~DR_TRAP_BITS
;
475 /* Handle all the breakpoints that were triggered */
476 for (i
= 0; i
< HBP_NUM
; ++i
) {
477 if (likely(!(dr6
& (DR_TRAP0
<< i
))))
481 * The counter may be concurrently released but that can only
482 * occur from a call_rcu() path. We can then safely fetch
483 * the breakpoint, use its callback, touch its counter
484 * while we are in an rcu_read_lock() path.
488 bp
= per_cpu(bp_per_reg
[i
], cpu
);
490 * Reset the 'i'th TRAP bit in dr6 to denote completion of
493 (*dr6_p
) &= ~(DR_TRAP0
<< i
);
495 * bp can be NULL due to lazy debug register switching
496 * or due to concurrent perf counter removing.
503 perf_bp_event(bp
, args
->regs
);
508 * Further processing in do_debug() is needed for a) user-space
509 * breakpoints (to generate signals) and b) when the system has
510 * taken exception due to multiple causes
512 if ((current
->thread
.debugreg6
& DR_TRAP_BITS
) ||
513 (dr6
& (~DR_TRAP_BITS
)))
516 set_debugreg(dr7
, 7);
523 * Handle debug exception notifications.
525 int __kprobes
hw_breakpoint_exceptions_notify(
526 struct notifier_block
*unused
, unsigned long val
, void *data
)
528 if (val
!= DIE_DEBUG
)
531 return hw_breakpoint_handler(data
);
534 void hw_breakpoint_pmu_read(struct perf_event
*bp
)
539 void hw_breakpoint_pmu_unthrottle(struct perf_event
*bp
)