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2023-12-09 95099d4622f8cb224d94e314c7a8e0df60b13f87 
 kernel/arch/x86/kernel/hw_breakpoint.c
....@@ -1,17 +1,5 @@
1
+// SPDX-License-Identifier: GPL-2.0-or-later
12 /*
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.
6
- *
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.
11
- *
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.
153  *
164  * Copyright (C) 2007 Alan Stern
175  * Copyright (C) 2009 IBM Corporation
....@@ -44,6 +32,8 @@
4432 #include <asm/processor.h>
4533 #include <asm/debugreg.h>
4634 #include <asm/user.h>
35
+#include <asm/desc.h>
36
+#include <asm/tlbflush.h>
4737 
4838 /* Per cpu debug control register value */
4939 DEFINE_PER_CPU(unsigned long, cpu_dr7);
....@@ -109,6 +99,8 @@
10999 	unsigned long *dr7;
110100 	int i;
111101 
102
+	lockdep_assert_irqs_disabled();
103
+
112104 	for (i = 0; i < HBP_NUM; i++) {
113105 		struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
114106 
....@@ -126,6 +118,12 @@
126118 
127119 	dr7 = this_cpu_ptr(&cpu_dr7);
128120 	*dr7 |= encode_dr7(i, info->len, info->type);
121
+
122
+	/*
123
+	 * Ensure we first write cpu_dr7 before we set the DR7 register.
124
+	 * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
125
+	 */
126
+	barrier();
129127 
130128 	set_debugreg(*dr7, 7);
131129 	if (info->mask)
....@@ -146,8 +144,10 @@
146144 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
147145 {
148146 	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
149
-	unsigned long *dr7;
147
+	unsigned long dr7;
150148 	int i;
149
+
150
+	lockdep_assert_irqs_disabled();
151151 
152152 	for (i = 0; i < HBP_NUM; i++) {
153153 		struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
....@@ -161,12 +161,20 @@
161161 	if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
162162 		return;
163163 
164
-	dr7 = this_cpu_ptr(&cpu_dr7);
165
-	*dr7 &= ~__encode_dr7(i, info->len, info->type);
164
+	dr7 = this_cpu_read(cpu_dr7);
165
+	dr7 &= ~__encode_dr7(i, info->len, info->type);
166166 
167
-	set_debugreg(*dr7, 7);
167
+	set_debugreg(dr7, 7);
168168 	if (info->mask)
169169 		set_dr_addr_mask(0, i);
170
+
171
+	/*
172
+	 * Ensure the write to cpu_dr7 is after we've set the DR7 register.
173
+	 * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
174
+	 */
175
+	barrier();
176
+
177
+	this_cpu_write(cpu_dr7, dr7);
170178 }
171179 
172180 static int arch_bp_generic_len(int x86_len)
....@@ -239,10 +247,98 @@
239247 	return (va >= TASK_SIZE_MAX) || ((va + len - 1) >= TASK_SIZE_MAX);
240248 }
241249 
250
+/*
251
+ * Checks whether the range [addr, end], overlaps the area [base, base + size).
252
+ */
253
+static inline bool within_area(unsigned long addr, unsigned long end,
254
+			       unsigned long base, unsigned long size)
255
+{
256
+	return end >= base && addr < (base + size);
257
+}
258
+
259
+/*
260
+ * Checks whether the range from addr to end, inclusive, overlaps the fixed
261
+ * mapped CPU entry area range or other ranges used for CPU entry.
262
+ */
263
+static inline bool within_cpu_entry(unsigned long addr, unsigned long end)
264
+{
265
+	int cpu;
266
+
267
+	/* CPU entry erea is always used for CPU entry */
268
+	if (within_area(addr, end, CPU_ENTRY_AREA_BASE,
269
+			CPU_ENTRY_AREA_TOTAL_SIZE))
270
+		return true;
271
+
272
+	/*
273
+	 * When FSGSBASE is enabled, paranoid_entry() fetches the per-CPU
274
+	 * GSBASE value via __per_cpu_offset or pcpu_unit_offsets.
275
+	 */
276
+#ifdef CONFIG_SMP
277
+	if (within_area(addr, end, (unsigned long)__per_cpu_offset,
278
+			sizeof(unsigned long) * nr_cpu_ids))
279
+		return true;
280
+#else
281
+	if (within_area(addr, end, (unsigned long)&pcpu_unit_offsets,
282
+			sizeof(pcpu_unit_offsets)))
283
+		return true;
284
+#endif
285
+
286
+	for_each_possible_cpu(cpu) {
287
+		/* The original rw GDT is being used after load_direct_gdt() */
288
+		if (within_area(addr, end, (unsigned long)get_cpu_gdt_rw(cpu),
289
+				GDT_SIZE))
290
+			return true;
291
+
292
+		/*
293
+		 * cpu_tss_rw is not directly referenced by hardware, but
294
+		 * cpu_tss_rw is also used in CPU entry code,
295
+		 */
296
+		if (within_area(addr, end,
297
+				(unsigned long)&per_cpu(cpu_tss_rw, cpu),
298
+				sizeof(struct tss_struct)))
299
+			return true;
300
+
301
+		/*
302
+		 * cpu_tlbstate.user_pcid_flush_mask is used for CPU entry.
303
+		 * If a data breakpoint on it, it will cause an unwanted #DB.
304
+		 * Protect the full cpu_tlbstate structure to be sure.
305
+		 */
306
+		if (within_area(addr, end,
307
+				(unsigned long)&per_cpu(cpu_tlbstate, cpu),
308
+				sizeof(struct tlb_state)))
309
+			return true;
310
+
311
+		/*
312
+		 * When in guest (X86_FEATURE_HYPERVISOR), local_db_save()
313
+		 * will read per-cpu cpu_dr7 before clear dr7 register.
314
+		 */
315
+		if (within_area(addr, end, (unsigned long)&per_cpu(cpu_dr7, cpu),
316
+				sizeof(cpu_dr7)))
317
+			return true;
318
+	}
319
+
320
+	return false;
321
+}
322
+
242323 static int arch_build_bp_info(struct perf_event *bp,
243324 			      const struct perf_event_attr *attr,
244325 			      struct arch_hw_breakpoint *hw)
245326 {
327
+	unsigned long bp_end;
328
+
329
+	bp_end = attr->bp_addr + attr->bp_len - 1;
330
+	if (bp_end < attr->bp_addr)
331
+		return -EINVAL;
332
+
333
+	/*
334
+	 * Prevent any breakpoint of any type that overlaps the CPU
335
+	 * entry area and data.  This protects the IST stacks and also
336
+	 * reduces the chance that we ever find out what happens if
337
+	 * there's a data breakpoint on the GDT, IDT, or TSS.
338
+	 */
339
+	if (within_cpu_entry(attr->bp_addr, bp_end))
340
+		return -EINVAL;
341
+
246342 	hw->address = attr->bp_addr;
247343 	hw->mask = 0;
248344 
....@@ -261,12 +357,8 @@
261357 		 * allow kernel breakpoints at all.
262358 		 */
263359 		if (attr->bp_addr >= TASK_SIZE_MAX) {
264
-#ifdef CONFIG_KPROBES
265360 			if (within_kprobe_blacklist(attr->bp_addr))
266361 				return -EINVAL;
267
-#else
268
-			return -EINVAL;
269
-#endif
270362 		}
271363 
272364 		hw->type = X86_BREAKPOINT_EXECUTE;
....@@ -279,6 +371,7 @@
279371 			hw->len = X86_BREAKPOINT_LEN_X;
280372 			return 0;
281373 		}
374
+		fallthrough;
282375 	default:
283376 		return -EINVAL;
284377 	}
....@@ -371,42 +464,6 @@
371464 }
372465 
373466 /*
374
- * Dump the debug register contents to the user.
375
- * We can't dump our per cpu values because it
376
- * may contain cpu wide breakpoint, something that
377
- * doesn't belong to the current task.
378
- *
379
- * TODO: include non-ptrace user breakpoints (perf)
380
- */
381
-void aout_dump_debugregs(struct user *dump)
382
-{
383
-	int i;
384
-	int dr7 = 0;
385
-	struct perf_event *bp;
386
-	struct arch_hw_breakpoint *info;
387
-	struct thread_struct *thread = &current->thread;
388
-
389
-	for (i = 0; i < HBP_NUM; i++) {
390
-		bp = thread->ptrace_bps[i];
391
-
392
-		if (bp && !bp->attr.disabled) {
393
-			dump->u_debugreg[i] = bp->attr.bp_addr;
394
-			info = counter_arch_bp(bp);
395
-			dr7 |= encode_dr7(i, info->len, info->type);
396
-		} else {
397
-			dump->u_debugreg[i] = 0;
398
-		}
399
-	}
400
-
401
-	dump->u_debugreg[4] = 0;
402
-	dump->u_debugreg[5] = 0;
403
-	dump->u_debugreg[6] = current->thread.debugreg6;
404
-
405
-	dump->u_debugreg[7] = dr7;
406
-}
407
-EXPORT_SYMBOL_GPL(aout_dump_debugregs);
408
-
409
-/*
410467  * Release the user breakpoints used by ptrace
411468  */
412469 void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
....@@ -419,7 +476,7 @@
419476 		t->ptrace_bps[i] = NULL;
420477 	}
421478 
422
-	t->debugreg6 = 0;
479
+	t->virtual_dr6 = 0;
423480 	t->ptrace_dr7 = 0;
424481 }
425482 
....@@ -429,7 +486,7 @@
429486 	set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
430487 	set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
431488 	set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
432
-	set_debugreg(current->thread.debugreg6, 6);
489
+	set_debugreg(DR6_RESERVED, 6);
433490 	set_debugreg(__this_cpu_read(cpu_dr7), 7);
434491 }
435492 EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
....@@ -452,61 +509,48 @@
452509  */
453510 static int hw_breakpoint_handler(struct die_args *args)
454511 {
455
-	int i, cpu, rc = NOTIFY_STOP;
512
+	int i, rc = NOTIFY_STOP;
456513 	struct perf_event *bp;
457
-	unsigned long dr7, dr6;
458514 	unsigned long *dr6_p;
515
+	unsigned long dr6;
516
+	bool bpx;
459517 
460518 	/* The DR6 value is pointed by args->err */
461519 	dr6_p = (unsigned long *)ERR_PTR(args->err);
462520 	dr6 = *dr6_p;
463521 
464
-	/* If it's a single step, TRAP bits are random */
465
-	if (dr6 & DR_STEP)
466
-		return NOTIFY_DONE;
467
-
468522 	/* Do an early return if no trap bits are set in DR6 */
469523 	if ((dr6 & DR_TRAP_BITS) == 0)
470524 		return NOTIFY_DONE;
471
-
472
-	get_debugreg(dr7, 7);
473
-	/* Disable breakpoints during exception handling */
474
-	set_debugreg(0UL, 7);
475
-	/*
476
-	 * Assert that local interrupts are disabled
477
-	 * Reset the DRn bits in the virtualized register value.
478
-	 * The ptrace trigger routine will add in whatever is needed.
479
-	 */
480
-	current->thread.debugreg6 &= ~DR_TRAP_BITS;
481
-	cpu = get_cpu();
482525 
483526 	/* Handle all the breakpoints that were triggered */
484527 	for (i = 0; i < HBP_NUM; ++i) {
485528 		if (likely(!(dr6 & (DR_TRAP0 << i))))
486529 			continue;
487530 
488
-		/*
489
-		 * The counter may be concurrently released but that can only
490
-		 * occur from a call_rcu() path. We can then safely fetch
491
-		 * the breakpoint, use its callback, touch its counter
492
-		 * while we are in an rcu_read_lock() path.
493
-		 */
494
-		rcu_read_lock();
531
+		bp = this_cpu_read(bp_per_reg[i]);
532
+		if (!bp)
533
+			continue;
495534 
496
-		bp = per_cpu(bp_per_reg[i], cpu);
535
+		bpx = bp->hw.info.type == X86_BREAKPOINT_EXECUTE;
536
+
537
+		/*
538
+		 * TF and data breakpoints are traps and can be merged, however
539
+		 * instruction breakpoints are faults and will be raised
540
+		 * separately.
541
+		 *
542
+		 * However DR6 can indicate both TF and instruction
543
+		 * breakpoints. In that case take TF as that has precedence and
544
+		 * delay the instruction breakpoint for the next exception.
545
+		 */
546
+		if (bpx && (dr6 & DR_STEP))
547
+			continue;
548
+
497549 		/*
498550 		 * Reset the 'i'th TRAP bit in dr6 to denote completion of
499551 		 * exception handling
500552 		 */
501553 		(*dr6_p) &= ~(DR_TRAP0 << i);
502
-		/*
503
-		 * bp can be NULL due to lazy debug register switching
504
-		 * or due to concurrent perf counter removing.
505
-		 */
506
-		if (!bp) {
507
-			rcu_read_unlock();
508
-			break;
509
-		}
510554 
511555 		perf_bp_event(bp, args->regs);
512556 
....@@ -514,22 +558,18 @@
514558 		 * Set up resume flag to avoid breakpoint recursion when
515559 		 * returning back to origin.
516560 		 */
517
-		if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE)
561
+		if (bpx)
518562 			args->regs->flags |= X86_EFLAGS_RF;
519
-
520
-		rcu_read_unlock();
521563 	}
564
+
522565 	/*
523566 	 * Further processing in do_debug() is needed for a) user-space
524567 	 * breakpoints (to generate signals) and b) when the system has
525568 	 * taken exception due to multiple causes
526569 	 */
527
-	if ((current->thread.debugreg6 & DR_TRAP_BITS) ||
570
+	if ((current->thread.virtual_dr6 & DR_TRAP_BITS) ||
528571 	    (dr6 & (~DR_TRAP_BITS)))
529572 		rc = NOTIFY_DONE;
530
-
531
-	set_debugreg(dr7, 7);
532
-	put_cpu();
533573 
534574 	return rc;
535575 }