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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c 
 kernel/arch/x86/kernel/unwind_orc.c
....@@ -1,3 +1,5 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
2
+#include <linux/objtool.h>
13 #include <linux/module.h>
24 #include <linux/sort.h>
35 #include <asm/ptrace.h>
....@@ -7,19 +9,21 @@
79 #include <asm/orc_lookup.h>
810 
911 #define orc_warn(fmt, ...) \
10
-	printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__)
12
+	printk_deferred_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
13
+
14
+#define orc_warn_current(args...)					\
15
+({									\
16
+	if (state->task == current)					\
17
+		orc_warn(args);						\
18
+})
1119 
1220 extern int __start_orc_unwind_ip[];
1321 extern int __stop_orc_unwind_ip[];
1422 extern struct orc_entry __start_orc_unwind[];
1523 extern struct orc_entry __stop_orc_unwind[];
1624 
17
-static DEFINE_MUTEX(sort_mutex);
18
-int *cur_orc_ip_table = __start_orc_unwind_ip;
19
-struct orc_entry *cur_orc_table = __start_orc_unwind;
20
-
21
-unsigned int lookup_num_blocks;
22
-bool orc_init;
25
+static bool orc_init __ro_after_init;
26
+static unsigned int lookup_num_blocks __ro_after_init;
2327 
2428 static inline unsigned long orc_ip(const int *ip)
2529 {
....@@ -81,30 +85,35 @@
8185  * But they are copies of the ftrace entries that are static and
8286  * defined in ftrace_*.S, which do have orc entries.
8387  *
84
- * If the undwinder comes across a ftrace trampoline, then find the
88
+ * If the unwinder comes across a ftrace trampoline, then find the
8589  * ftrace function that was used to create it, and use that ftrace
86
- * function's orc entrie, as the placement of the return code in
90
+ * function's orc entry, as the placement of the return code in
8791  * the stack will be identical.
8892  */
8993 static struct orc_entry *orc_ftrace_find(unsigned long ip)
9094 {
9195 	struct ftrace_ops *ops;
92
-	unsigned long caller;
96
+	unsigned long tramp_addr, offset;
9397 
9498 	ops = ftrace_ops_trampoline(ip);
9599 	if (!ops)
96100 		return NULL;
97101 
102
+	/* Set tramp_addr to the start of the code copied by the trampoline */
98103 	if (ops->flags & FTRACE_OPS_FL_SAVE_REGS)
99
-		caller = (unsigned long)ftrace_regs_call;
104
+		tramp_addr = (unsigned long)ftrace_regs_caller;
100105 	else
101
-		caller = (unsigned long)ftrace_call;
106
+		tramp_addr = (unsigned long)ftrace_caller;
107
+
108
+	/* Now place tramp_addr to the location within the trampoline ip is at */
109
+	offset = ip - ops->trampoline;
110
+	tramp_addr += offset;
102111 
103112 	/* Prevent unlikely recursion */
104
-	if (ip == caller)
113
+	if (ip == tramp_addr)
105114 		return NULL;
106115 
107
-	return orc_find(caller);
116
+	return orc_find(tramp_addr);
108117 }
109118 #else
110119 static struct orc_entry *orc_ftrace_find(unsigned long ip)
....@@ -124,7 +133,17 @@
124133 	.sp_offset = sizeof(long),
125134 	.sp_reg = ORC_REG_SP,
126135 	.bp_reg = ORC_REG_UNDEFINED,
127
-	.type = ORC_TYPE_CALL
136
+	.type = UNWIND_HINT_TYPE_CALL
137
+};
138
+
139
+/* Fake frame pointer entry -- used as a fallback for generated code */
140
+static struct orc_entry orc_fp_entry = {
141
+	.type		= UNWIND_HINT_TYPE_CALL,
142
+	.sp_reg		= ORC_REG_BP,
143
+	.sp_offset	= 16,
144
+	.bp_reg		= ORC_REG_PREV_SP,
145
+	.bp_offset	= -16,
146
+	.end		= 0,
128147 };
129148 
130149 static struct orc_entry *orc_find(unsigned long ip)
....@@ -173,6 +192,12 @@
173192 	return orc_ftrace_find(ip);
174193 }
175194 
195
+#ifdef CONFIG_MODULES
196
+
197
+static DEFINE_MUTEX(sort_mutex);
198
+static int *cur_orc_ip_table = __start_orc_unwind_ip;
199
+static struct orc_entry *cur_orc_table = __start_orc_unwind;
200
+
176201 static void orc_sort_swap(void *_a, void *_b, int size)
177202 {
178203 	struct orc_entry *orc_a, *orc_b;
....@@ -215,7 +240,6 @@
215240 	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
216241 }
217242 
218
-#ifdef CONFIG_MODULES
219243 void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,
220244 			void *_orc, size_t orc_size)
221245 {
....@@ -259,9 +283,11 @@
259283 		return;
260284 	}
261285 
262
-	/* Sort the .orc_unwind and .orc_unwind_ip tables: */
263
-	sort(__start_orc_unwind_ip, num_entries, sizeof(int), orc_sort_cmp,
264
-	     orc_sort_swap);
286
+	/*
287
+	 * Note, the orc_unwind and orc_unwind_ip tables were already
288
+	 * sorted at build time via the 'sorttable' tool.
289
+	 * It's ready for binary search straight away, no need to sort it.
290
+	 */
265291 
266292 	/* Initialize the fast lookup table: */
267293 	lookup_num_blocks = orc_lookup_end - orc_lookup;
....@@ -420,8 +446,16 @@
420446 	 * call instruction itself.
421447 	 */
422448 	orc = orc_find(state->signal ? state->ip : state->ip - 1);
423
-	if (!orc)
424
-		goto err;
449
+	if (!orc) {
450
+		/*
451
+		 * As a fallback, try to assume this code uses a frame pointer.
452
+		 * This is useful for generated code, like BPF, which ORC
453
+		 * doesn't know about.  This is just a guess, so the rest of
454
+		 * the unwind is no longer considered reliable.
455
+		 */
456
+		orc = &orc_fp_entry;
457
+		state->error = true;
458
+	}
425459 
426460 	/* End-of-stack check for kernel threads: */
427461 	if (orc->sp_reg == ORC_REG_UNDEFINED) {
....@@ -453,38 +487,38 @@
453487 
454488 	case ORC_REG_R10:
455489 		if (!get_reg(state, offsetof(struct pt_regs, r10), &sp)) {
456
-			orc_warn("missing regs for base reg R10 at ip %pB\n",
457
-				 (void *)state->ip);
490
+			orc_warn_current("missing R10 value at %pB\n",
491
+					 (void *)state->ip);
458492 			goto err;
459493 		}
460494 		break;
461495 
462496 	case ORC_REG_R13:
463497 		if (!get_reg(state, offsetof(struct pt_regs, r13), &sp)) {
464
-			orc_warn("missing regs for base reg R13 at ip %pB\n",
465
-				 (void *)state->ip);
498
+			orc_warn_current("missing R13 value at %pB\n",
499
+					 (void *)state->ip);
466500 			goto err;
467501 		}
468502 		break;
469503 
470504 	case ORC_REG_DI:
471505 		if (!get_reg(state, offsetof(struct pt_regs, di), &sp)) {
472
-			orc_warn("missing regs for base reg DI at ip %pB\n",
473
-				 (void *)state->ip);
506
+			orc_warn_current("missing RDI value at %pB\n",
507
+					 (void *)state->ip);
474508 			goto err;
475509 		}
476510 		break;
477511 
478512 	case ORC_REG_DX:
479513 		if (!get_reg(state, offsetof(struct pt_regs, dx), &sp)) {
480
-			orc_warn("missing regs for base reg DX at ip %pB\n",
481
-				 (void *)state->ip);
514
+			orc_warn_current("missing DX value at %pB\n",
515
+					 (void *)state->ip);
482516 			goto err;
483517 		}
484518 		break;
485519 
486520 	default:
487
-		orc_warn("unknown SP base reg %d for ip %pB\n",
521
+		orc_warn("unknown SP base reg %d at %pB\n",
488522 			 orc->sp_reg, (void *)state->ip);
489523 		goto err;
490524 	}
....@@ -496,7 +530,7 @@
496530 
497531 	/* Find IP, SP and possibly regs: */
498532 	switch (orc->type) {
499
-	case ORC_TYPE_CALL:
533
+	case UNWIND_HINT_TYPE_CALL:
500534 		ip_p = sp - sizeof(long);
501535 
502536 		if (!deref_stack_reg(state, ip_p, &state->ip))
....@@ -511,10 +545,10 @@
511545 		state->signal = false;
512546 		break;
513547 
514
-	case ORC_TYPE_REGS:
548
+	case UNWIND_HINT_TYPE_REGS:
515549 		if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
516
-			orc_warn("can't dereference registers at %p for ip %pB\n",
517
-				 (void *)sp, (void *)orig_ip);
550
+			orc_warn_current("can't access registers at %pB\n",
551
+					 (void *)orig_ip);
518552 			goto err;
519553 		}
520554 
....@@ -524,10 +558,10 @@
524558 		state->signal = true;
525559 		break;
526560 
527
-	case ORC_TYPE_REGS_IRET:
561
+	case UNWIND_HINT_TYPE_REGS_PARTIAL:
528562 		if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
529
-			orc_warn("can't dereference iret registers at %p for ip %pB\n",
530
-				 (void *)sp, (void *)orig_ip);
563
+			orc_warn_current("can't access iret registers at %pB\n",
564
+					 (void *)orig_ip);
531565 			goto err;
532566 		}
533567 
....@@ -539,7 +573,7 @@
539573 		break;
540574 
541575 	default:
542
-		orc_warn("unknown .orc_unwind entry type %d for ip %pB\n",
576
+		orc_warn("unknown .orc_unwind entry type %d at %pB\n",
543577 			 orc->type, (void *)orig_ip);
544578 		goto err;
545579 	}
....@@ -571,8 +605,8 @@
571605 	if (state->stack_info.type == prev_type &&
572606 	    on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
573607 	    state->sp <= prev_sp) {
574
-		orc_warn("stack going in the wrong direction? ip=%pB\n",
575
-			 (void *)orig_ip);
608
+		orc_warn_current("stack going in the wrong direction? at %pB\n",
609
+				 (void *)orig_ip);
576610 		goto err;
577611 	}
578612 
....@@ -611,7 +645,7 @@
611645 			goto the_end;
612646 
613647 		state->ip = regs->ip;
614
-		state->sp = kernel_stack_pointer(regs);
648
+		state->sp = regs->sp;
615649 		state->bp = regs->bp;
616650 		state->regs = regs;
617651 		state->full_regs = true;
....@@ -663,7 +697,7 @@
663697 	/* Otherwise, skip ahead to the user-specified starting frame: */
664698 	while (!unwind_done(state) &&
665699 	       (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
666
-			state->sp < (unsigned long)first_frame))
700
+			state->sp <= (unsigned long)first_frame))
667701 		unwind_next_frame(state);
668702 
669703 	return;