1 /* Debug register code for x86 (i386 and x86-64).
3 Copyright (C) 2001-2017 Free Software Foundation, Inc.
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>. */
20 #include "common-defs.h"
21 #include "x86-dregs.h"
22 #include "break-common.h"
24 /* Support for hardware watchpoints and breakpoints using the x86
27 This provides several functions for inserting and removing
28 hardware-assisted breakpoints and watchpoints, testing if one or
29 more of the watchpoints triggered and at what address, checking
30 whether a given region can be watched, etc.
32 The functions below implement debug registers sharing by reference
33 counts, and allow to watch regions up to 16 bytes long. */
35 /* Accessor macros for low-level function vector. */
37 /* Can we update the inferior's debug registers? */
38 #define x86_dr_low_can_set_addr() (x86_dr_low.set_addr != NULL)
40 /* Update the inferior's debug register REGNUM from STATE. */
41 #define x86_dr_low_set_addr(new_state, i) \
42 (x86_dr_low.set_addr ((i), (new_state)->dr_mirror[(i)]))
44 /* Return the inferior's debug register REGNUM. */
45 #define x86_dr_low_get_addr(i) (x86_dr_low.get_addr ((i)))
47 /* Can we update the inferior's DR7 control register? */
48 #define x86_dr_low_can_set_control() (x86_dr_low.set_control != NULL)
50 /* Update the inferior's DR7 debug control register from STATE. */
51 #define x86_dr_low_set_control(new_state) \
52 (x86_dr_low.set_control ((new_state)->dr_control_mirror))
54 /* Return the value of the inferior's DR7 debug control register. */
55 #define x86_dr_low_get_control() (x86_dr_low.get_control ())
57 /* Return the value of the inferior's DR6 debug status register. */
58 #define x86_dr_low_get_status() (x86_dr_low.get_status ())
60 /* Return the debug register size, in bytes. */
61 #define x86_get_debug_register_length() \
62 (x86_dr_low.debug_register_length)
64 /* Support for 8-byte wide hw watchpoints. */
65 #define TARGET_HAS_DR_LEN_8 (x86_get_debug_register_length () == 8)
67 /* DR7 Debug Control register fields. */
69 /* How many bits to skip in DR7 to get to R/W and LEN fields. */
70 #define DR_CONTROL_SHIFT 16
71 /* How many bits in DR7 per R/W and LEN field for each watchpoint. */
72 #define DR_CONTROL_SIZE 4
74 /* Watchpoint/breakpoint read/write fields in DR7. */
75 #define DR_RW_EXECUTE (0x0) /* Break on instruction execution. */
76 #define DR_RW_WRITE (0x1) /* Break on data writes. */
77 #define DR_RW_READ (0x3) /* Break on data reads or writes. */
79 /* This is here for completeness. No platform supports this
80 functionality yet (as of March 2001). Note that the DE flag in the
81 CR4 register needs to be set to support this. */
83 #define DR_RW_IORW (0x2) /* Break on I/O reads or writes. */
86 /* Watchpoint/breakpoint length fields in DR7. The 2-bit left shift
87 is so we could OR this with the read/write field defined above. */
88 #define DR_LEN_1 (0x0 << 2) /* 1-byte region watch or breakpoint. */
89 #define DR_LEN_2 (0x1 << 2) /* 2-byte region watch. */
90 #define DR_LEN_4 (0x3 << 2) /* 4-byte region watch. */
91 #define DR_LEN_8 (0x2 << 2) /* 8-byte region watch (AMD64). */
93 /* Local and Global Enable flags in DR7.
95 When the Local Enable flag is set, the breakpoint/watchpoint is
96 enabled only for the current task; the processor automatically
97 clears this flag on every task switch. When the Global Enable flag
98 is set, the breakpoint/watchpoint is enabled for all tasks; the
99 processor never clears this flag.
101 Currently, all watchpoint are locally enabled. If you need to
102 enable them globally, read the comment which pertains to this in
103 x86_insert_aligned_watchpoint below. */
104 #define DR_LOCAL_ENABLE_SHIFT 0 /* Extra shift to the local enable bit. */
105 #define DR_GLOBAL_ENABLE_SHIFT 1 /* Extra shift to the global enable bit. */
106 #define DR_ENABLE_SIZE 2 /* Two enable bits per debug register. */
108 /* Local and global exact breakpoint enable flags (a.k.a. slowdown
109 flags). These are only required on i386, to allow detection of the
110 exact instruction which caused a watchpoint to break; i486 and
111 later processors do that automatically. We set these flags for
112 backwards compatibility. */
113 #define DR_LOCAL_SLOWDOWN (0x100)
114 #define DR_GLOBAL_SLOWDOWN (0x200)
116 /* Fields reserved by Intel. This includes the GD (General Detect
117 Enable) flag, which causes a debug exception to be generated when a
118 MOV instruction accesses one of the debug registers.
120 FIXME: My Intel manual says we should use 0xF800, not 0xFC00. */
121 #define DR_CONTROL_RESERVED (0xFC00)
123 /* Auxiliary helper macros. */
125 /* A value that masks all fields in DR7 that are reserved by Intel. */
126 #define X86_DR_CONTROL_MASK (~DR_CONTROL_RESERVED)
128 /* The I'th debug register is vacant if its Local and Global Enable
129 bits are reset in the Debug Control register. */
130 #define X86_DR_VACANT(state, i) \
131 (((state)->dr_control_mirror & (3 << (DR_ENABLE_SIZE * (i)))) == 0)
133 /* Locally enable the break/watchpoint in the I'th debug register. */
134 #define X86_DR_LOCAL_ENABLE(state, i) \
136 (state)->dr_control_mirror |= \
137 (1 << (DR_LOCAL_ENABLE_SHIFT + DR_ENABLE_SIZE * (i))); \
140 /* Globally enable the break/watchpoint in the I'th debug register. */
141 #define X86_DR_GLOBAL_ENABLE(state, i) \
143 (state)->dr_control_mirror |= \
144 (1 << (DR_GLOBAL_ENABLE_SHIFT + DR_ENABLE_SIZE * (i))); \
147 /* Disable the break/watchpoint in the I'th debug register. */
148 #define X86_DR_DISABLE(state, i) \
150 (state)->dr_control_mirror &= \
151 ~(3 << (DR_ENABLE_SIZE * (i))); \
154 /* Set in DR7 the RW and LEN fields for the I'th debug register. */
155 #define X86_DR_SET_RW_LEN(state, i, rwlen) \
157 (state)->dr_control_mirror &= \
158 ~(0x0f << (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))); \
159 (state)->dr_control_mirror |= \
160 ((rwlen) << (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))); \
163 /* Get from DR7 the RW and LEN fields for the I'th debug register. */
164 #define X86_DR_GET_RW_LEN(dr7, i) \
166 >> (DR_CONTROL_SHIFT + DR_CONTROL_SIZE * (i))) & 0x0f)
168 /* Did the watchpoint whose address is in the I'th register break? */
169 #define X86_DR_WATCH_HIT(dr6, i) ((dr6) & (1 << (i)))
171 /* Types of operations supported by x86_handle_nonaligned_watchpoint. */
172 typedef enum { WP_INSERT
, WP_REMOVE
, WP_COUNT
} x86_wp_op_t
;
174 /* Print the values of the mirrored debug registers. */
177 x86_show_dr (struct x86_debug_reg_state
*state
,
178 const char *func
, CORE_ADDR addr
,
179 int len
, enum target_hw_bp_type type
)
183 debug_printf ("%s", func
);
185 debug_printf (" (addr=%s, len=%d, type=%s)",
187 type
== hw_write
? "data-write"
188 : (type
== hw_read
? "data-read"
189 : (type
== hw_access
? "data-read/write"
190 : (type
== hw_execute
? "instruction-execute"
191 /* FIXME: if/when I/O read/write
192 watchpoints are supported, add them
195 debug_printf (":\n");
197 debug_printf ("\tCONTROL (DR7): 0x%s\n", phex (state
->dr_control_mirror
, 8));
198 debug_printf ("\tSTATUS (DR6): 0x%s\n", phex (state
->dr_status_mirror
, 8));
200 ALL_DEBUG_ADDRESS_REGISTERS (i
)
202 debug_printf ("\tDR%d: addr=0x%s, ref.count=%d\n",
203 i
, phex (state
->dr_mirror
[i
],
204 x86_get_debug_register_length ()),
205 state
->dr_ref_count
[i
]);
209 /* Return the value of a 4-bit field for DR7 suitable for watching a
210 region of LEN bytes for accesses of type TYPE. LEN is assumed to
211 have the value of 1, 2, or 4. */
214 x86_length_and_rw_bits (int len
, enum target_hw_bp_type type
)
227 internal_error (__FILE__
, __LINE__
,
228 _("The i386 doesn't support "
229 "data-read watchpoints.\n"));
234 /* Not yet supported. */
240 internal_error (__FILE__
, __LINE__
, _("\
241 Invalid hardware breakpoint type %d in x86_length_and_rw_bits.\n"),
248 return (DR_LEN_1
| rw
);
250 return (DR_LEN_2
| rw
);
252 return (DR_LEN_4
| rw
);
254 if (TARGET_HAS_DR_LEN_8
)
255 return (DR_LEN_8
| rw
);
256 /* ELSE FALL THROUGH */
258 internal_error (__FILE__
, __LINE__
, _("\
259 Invalid hardware breakpoint length %d in x86_length_and_rw_bits.\n"), len
);
263 /* Insert a watchpoint at address ADDR, which is assumed to be aligned
264 according to the length of the region to watch. LEN_RW_BITS is the
265 value of the bits from DR7 which describes the length and access
266 type of the region to be watched by this watchpoint. Return 0 on
267 success, -1 on failure. */
270 x86_insert_aligned_watchpoint (struct x86_debug_reg_state
*state
,
271 CORE_ADDR addr
, unsigned len_rw_bits
)
275 if (!x86_dr_low_can_set_addr () || !x86_dr_low_can_set_control ())
278 /* First, look for an occupied debug register with the same address
279 and the same RW and LEN definitions. If we find one, we can
280 reuse it for this watchpoint as well (and save a register). */
281 ALL_DEBUG_ADDRESS_REGISTERS (i
)
283 if (!X86_DR_VACANT (state
, i
)
284 && state
->dr_mirror
[i
] == addr
285 && X86_DR_GET_RW_LEN (state
->dr_control_mirror
, i
) == len_rw_bits
)
287 state
->dr_ref_count
[i
]++;
292 /* Next, look for a vacant debug register. */
293 ALL_DEBUG_ADDRESS_REGISTERS (i
)
295 if (X86_DR_VACANT (state
, i
))
299 /* No more debug registers! */
303 /* Now set up the register I to watch our region. */
305 /* Record the info in our local mirrored array. */
306 state
->dr_mirror
[i
] = addr
;
307 state
->dr_ref_count
[i
] = 1;
308 X86_DR_SET_RW_LEN (state
, i
, len_rw_bits
);
309 /* Note: we only enable the watchpoint locally, i.e. in the current
310 task. Currently, no x86 target allows or supports global
311 watchpoints; however, if any target would want that in the
312 future, GDB should probably provide a command to control whether
313 to enable watchpoints globally or locally, and the code below
314 should use global or local enable and slow-down flags as
316 X86_DR_LOCAL_ENABLE (state
, i
);
317 state
->dr_control_mirror
|= DR_LOCAL_SLOWDOWN
;
318 state
->dr_control_mirror
&= X86_DR_CONTROL_MASK
;
323 /* Remove a watchpoint at address ADDR, which is assumed to be aligned
324 according to the length of the region to watch. LEN_RW_BITS is the
325 value of the bits from DR7 which describes the length and access
326 type of the region watched by this watchpoint. Return 0 on
327 success, -1 on failure. */
330 x86_remove_aligned_watchpoint (struct x86_debug_reg_state
*state
,
331 CORE_ADDR addr
, unsigned len_rw_bits
)
336 ALL_DEBUG_ADDRESS_REGISTERS (i
)
338 if (!X86_DR_VACANT (state
, i
)
339 && state
->dr_mirror
[i
] == addr
340 && X86_DR_GET_RW_LEN (state
->dr_control_mirror
, i
) == len_rw_bits
)
342 if (--state
->dr_ref_count
[i
] == 0) /* No longer in use? */
344 /* Reset our mirror. */
345 state
->dr_mirror
[i
] = 0;
346 X86_DR_DISABLE (state
, i
);
347 /* Even though not strictly necessary, clear out all
348 bits in DR_CONTROL related to this debug register.
349 Debug output is clearer when we don't have stale bits
350 in place. This also allows the assertion below. */
351 X86_DR_SET_RW_LEN (state
, i
, 0);
356 if (!X86_DR_VACANT (state
, i
))
362 /* Even though not strictly necessary, clear out all of
363 DR_CONTROL, so that when we have no debug registers in use,
364 we end up with DR_CONTROL == 0. The Linux support relies on
365 this for an optimization. Plus, it makes for clearer debug
367 state
->dr_control_mirror
&= ~DR_LOCAL_SLOWDOWN
;
369 gdb_assert (state
->dr_control_mirror
== 0);
374 /* Insert or remove a (possibly non-aligned) watchpoint, or count the
375 number of debug registers required to watch a region at address
376 ADDR whose length is LEN for accesses of type TYPE. Return 0 on
377 successful insertion or removal, a positive number when queried
378 about the number of registers, or -1 on failure. If WHAT is not a
379 valid value, bombs through internal_error. */
382 x86_handle_nonaligned_watchpoint (struct x86_debug_reg_state
*state
,
383 x86_wp_op_t what
, CORE_ADDR addr
, int len
,
384 enum target_hw_bp_type type
)
387 int max_wp_len
= TARGET_HAS_DR_LEN_8
? 8 : 4;
389 static const int size_try_array
[8][8] =
391 {1, 1, 1, 1, 1, 1, 1, 1}, /* Trying size one. */
392 {2, 1, 2, 1, 2, 1, 2, 1}, /* Trying size two. */
393 {2, 1, 2, 1, 2, 1, 2, 1}, /* Trying size three. */
394 {4, 1, 2, 1, 4, 1, 2, 1}, /* Trying size four. */
395 {4, 1, 2, 1, 4, 1, 2, 1}, /* Trying size five. */
396 {4, 1, 2, 1, 4, 1, 2, 1}, /* Trying size six. */
397 {4, 1, 2, 1, 4, 1, 2, 1}, /* Trying size seven. */
398 {8, 1, 2, 1, 4, 1, 2, 1}, /* Trying size eight. */
403 int align
= addr
% max_wp_len
;
404 /* Four (eight on AMD64) is the maximum length a debug register
406 int attempt
= (len
> max_wp_len
? (max_wp_len
- 1) : len
- 1);
407 int size
= size_try_array
[attempt
][align
];
409 if (what
== WP_COUNT
)
411 /* size_try_array[] is defined such that each iteration
412 through the loop is guaranteed to produce an address and a
413 size that can be watched with a single debug register.
414 Thus, for counting the registers required to watch a
415 region, we simply need to increment the count on each
421 unsigned len_rw
= x86_length_and_rw_bits (size
, type
);
423 if (what
== WP_INSERT
)
424 retval
= x86_insert_aligned_watchpoint (state
, addr
, len_rw
);
425 else if (what
== WP_REMOVE
)
426 retval
= x86_remove_aligned_watchpoint (state
, addr
, len_rw
);
428 internal_error (__FILE__
, __LINE__
, _("\
429 Invalid value %d of operation in x86_handle_nonaligned_watchpoint.\n"),
442 /* Update the inferior debug registers state, in STATE, with the
443 new debug registers state, in NEW_STATE. */
446 x86_update_inferior_debug_regs (struct x86_debug_reg_state
*state
,
447 struct x86_debug_reg_state
*new_state
)
451 ALL_DEBUG_ADDRESS_REGISTERS (i
)
453 if (X86_DR_VACANT (new_state
, i
) != X86_DR_VACANT (state
, i
))
454 x86_dr_low_set_addr (new_state
, i
);
456 gdb_assert (new_state
->dr_mirror
[i
] == state
->dr_mirror
[i
]);
459 if (new_state
->dr_control_mirror
!= state
->dr_control_mirror
)
460 x86_dr_low_set_control (new_state
);
465 /* Insert a watchpoint to watch a memory region which starts at
466 address ADDR and whose length is LEN bytes. Watch memory accesses
467 of the type TYPE. Return 0 on success, -1 on failure. */
470 x86_dr_insert_watchpoint (struct x86_debug_reg_state
*state
,
471 enum target_hw_bp_type type
,
472 CORE_ADDR addr
, int len
)
475 /* Work on a local copy of the debug registers, and on success,
476 commit the change back to the inferior. */
477 struct x86_debug_reg_state local_state
= *state
;
480 return 1; /* unsupported */
482 if (((len
!= 1 && len
!= 2 && len
!= 4)
483 && !(TARGET_HAS_DR_LEN_8
&& len
== 8))
486 retval
= x86_handle_nonaligned_watchpoint (&local_state
,
492 unsigned len_rw
= x86_length_and_rw_bits (len
, type
);
494 retval
= x86_insert_aligned_watchpoint (&local_state
,
499 x86_update_inferior_debug_regs (state
, &local_state
);
502 x86_show_dr (state
, "insert_watchpoint", addr
, len
, type
);
507 /* Remove a watchpoint that watched the memory region which starts at
508 address ADDR, whose length is LEN bytes, and for accesses of the
509 type TYPE. Return 0 on success, -1 on failure. */
512 x86_dr_remove_watchpoint (struct x86_debug_reg_state
*state
,
513 enum target_hw_bp_type type
,
514 CORE_ADDR addr
, int len
)
517 /* Work on a local copy of the debug registers, and on success,
518 commit the change back to the inferior. */
519 struct x86_debug_reg_state local_state
= *state
;
521 if (((len
!= 1 && len
!= 2 && len
!= 4)
522 && !(TARGET_HAS_DR_LEN_8
&& len
== 8))
525 retval
= x86_handle_nonaligned_watchpoint (&local_state
,
531 unsigned len_rw
= x86_length_and_rw_bits (len
, type
);
533 retval
= x86_remove_aligned_watchpoint (&local_state
,
538 x86_update_inferior_debug_regs (state
, &local_state
);
541 x86_show_dr (state
, "remove_watchpoint", addr
, len
, type
);
546 /* Return non-zero if we can watch a memory region that starts at
547 address ADDR and whose length is LEN bytes. */
550 x86_dr_region_ok_for_watchpoint (struct x86_debug_reg_state
*state
,
551 CORE_ADDR addr
, int len
)
555 /* Compute how many aligned watchpoints we would need to cover this
557 nregs
= x86_handle_nonaligned_watchpoint (state
, WP_COUNT
,
558 addr
, len
, hw_write
);
559 return nregs
<= DR_NADDR
? 1 : 0;
562 /* If the inferior has some break/watchpoint that triggered, set the
563 address associated with that break/watchpoint and return non-zero.
564 Otherwise, return zero. */
567 x86_dr_stopped_data_address (struct x86_debug_reg_state
*state
,
573 /* The current thread's DR_STATUS. We always need to read this to
574 check whether some watchpoint caused the trap. */
576 /* We need DR_CONTROL as well, but only iff DR_STATUS indicates a
577 data breakpoint trap. Only fetch it when necessary, to avoid an
578 unnecessary extra syscall when no watchpoint triggered. */
580 unsigned control
= 0;
582 /* In non-stop/async, threads can be running while we change the
583 global dr_mirror (and friends). Say, we set a watchpoint, and
584 let threads resume. Now, say you delete the watchpoint, or
585 add/remove watchpoints such that dr_mirror changes while threads
586 are running. On targets that support non-stop,
587 inserting/deleting watchpoints updates the global dr_mirror only.
588 It does not update the real thread's debug registers; that's only
589 done prior to resume. Instead, if threads are running when the
590 mirror changes, a temporary and transparent stop on all threads
591 is forced so they can get their copy of the debug registers
592 updated on re-resume. Now, say, a thread hit a watchpoint before
593 having been updated with the new dr_mirror contents, and we
594 haven't yet handled the corresponding SIGTRAP. If we trusted
595 dr_mirror below, we'd mistake the real trapped address (from the
596 last time we had updated debug registers in the thread) with
597 whatever was currently in dr_mirror. So to fix this, dr_mirror
598 always represents intention, what we _want_ threads to have in
599 debug registers. To get at the address and cause of the trap, we
600 need to read the state the thread still has in its debug
603 In sum, always get the current debug register values the current
604 thread has, instead of trusting the global mirror. If the thread
605 was running when we last changed watchpoints, the mirror no
606 longer represents what was set in this thread's debug
608 status
= x86_dr_low_get_status ();
610 ALL_DEBUG_ADDRESS_REGISTERS (i
)
612 if (!X86_DR_WATCH_HIT (status
, i
))
617 control
= x86_dr_low_get_control ();
621 /* This second condition makes sure DRi is set up for a data
622 watchpoint, not a hardware breakpoint. The reason is that
623 GDB doesn't call the target_stopped_data_address method
624 except for data watchpoints. In other words, I'm being
626 if (X86_DR_GET_RW_LEN (control
, i
) != 0)
628 addr
= x86_dr_low_get_addr (i
);
631 x86_show_dr (state
, "watchpoint_hit", addr
, -1, hw_write
);
635 if (show_debug_regs
&& addr
== 0)
636 x86_show_dr (state
, "stopped_data_addr", 0, 0, hw_write
);
643 /* Return non-zero if the inferior has some watchpoint that triggered.
644 Otherwise return zero. */
647 x86_dr_stopped_by_watchpoint (struct x86_debug_reg_state
*state
)
650 return x86_dr_stopped_data_address (state
, &addr
);