1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Copyright (C) 2012 ARM Ltd.
4  */
5 #ifndef __ASM_STACKTRACE_H
6 #define __ASM_STACKTRACE_H
7 
8 #include <linux/percpu.h>
9 #include <linux/sched.h>
10 #include <linux/sched/task_stack.h>
11 #include <linux/types.h>
12 
13 #include <asm/memory.h>
14 #include <asm/ptrace.h>
15 #include <asm/sdei.h>
16 
17 enum stack_type {
18 	STACK_TYPE_UNKNOWN,
19 	STACK_TYPE_TASK,
20 	STACK_TYPE_IRQ,
21 	STACK_TYPE_OVERFLOW,
22 	STACK_TYPE_SDEI_NORMAL,
23 	STACK_TYPE_SDEI_CRITICAL,
24 	__NR_STACK_TYPES
25 };
26 
27 struct stack_info {
28 	unsigned long low;
29 	unsigned long high;
30 	enum stack_type type;
31 };
32 
33 /*
34  * A snapshot of a frame record or fp/lr register values, along with some
35  * accounting information necessary for robust unwinding.
36  *
37  * @fp:          The fp value in the frame record (or the real fp)
38  * @pc:          The fp value in the frame record (or the real lr)
39  *
40  * @stacks_done: Stacks which have been entirely unwound, for which it is no
41  *               longer valid to unwind to.
42  *
43  * @prev_fp:     The fp that pointed to this frame record, or a synthetic value
44  *               of 0. This is used to ensure that within a stack, each
45  *               subsequent frame record is at an increasing address.
46  * @prev_type:   The type of stack this frame record was on, or a synthetic
47  *               value of STACK_TYPE_UNKNOWN. This is used to detect a
48  *               transition from one stack to another.
49  *
50  * @graph:       When FUNCTION_GRAPH_TRACER is selected, holds the index of a
51  *               replacement lr value in the ftrace graph stack.
52  */
53 struct stackframe {
54 	unsigned long fp;
55 	unsigned long pc;
56 	DECLARE_BITMAP(stacks_done, __NR_STACK_TYPES);
57 	unsigned long prev_fp;
58 	enum stack_type prev_type;
59 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
60 	int graph;
61 #endif
62 };
63 
64 extern int unwind_frame(struct task_struct *tsk, struct stackframe *frame);
65 extern void walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
66 			    int (*fn)(struct stackframe *, void *), void *data);
67 extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
68 			   const char *loglvl);
69 
70 DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
71 
72 static inline bool on_stack(unsigned long sp, unsigned long low,
73 				unsigned long high, enum stack_type type,
74 				struct stack_info *info)
75 {
76 	if (!low)
77 		return false;
78 
79 	if (sp < low || sp >= high)
80 		return false;
81 
82 	if (info) {
83 		info->low = low;
84 		info->high = high;
85 		info->type = type;
86 	}
87 	return true;
88 }
89 
90 static inline bool on_irq_stack(unsigned long sp,
91 				struct stack_info *info)
92 {
93 	unsigned long low = (unsigned long)raw_cpu_read(irq_stack_ptr);
94 	unsigned long high = low + IRQ_STACK_SIZE;
95 
96 	return on_stack(sp, low, high, STACK_TYPE_IRQ, info);
97 }
98 
99 static inline bool on_task_stack(const struct task_struct *tsk,
100 				 unsigned long sp,
101 				 struct stack_info *info)
102 {
103 	unsigned long low = (unsigned long)task_stack_page(tsk);
104 	unsigned long high = low + THREAD_SIZE;
105 
106 	return on_stack(sp, low, high, STACK_TYPE_TASK, info);
107 }
108 
109 #ifdef CONFIG_VMAP_STACK
110 DECLARE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack);
111 
112 static inline bool on_overflow_stack(unsigned long sp,
113 				struct stack_info *info)
114 {
115 	unsigned long low = (unsigned long)raw_cpu_ptr(overflow_stack);
116 	unsigned long high = low + OVERFLOW_STACK_SIZE;
117 
118 	return on_stack(sp, low, high, STACK_TYPE_OVERFLOW, info);
119 }
120 #else
121 static inline bool on_overflow_stack(unsigned long sp,
122 			struct stack_info *info) { return false; }
123 #endif
124 
125 
126 /*
127  * We can only safely access per-cpu stacks from current in a non-preemptible
128  * context.
129  */
130 static inline bool on_accessible_stack(const struct task_struct *tsk,
131 				       unsigned long sp,
132 				       struct stack_info *info)
133 {
134 	if (info)
135 		info->type = STACK_TYPE_UNKNOWN;
136 
137 	if (on_task_stack(tsk, sp, info))
138 		return true;
139 	if (tsk != current || preemptible())
140 		return false;
141 	if (on_irq_stack(sp, info))
142 		return true;
143 	if (on_overflow_stack(sp, info))
144 		return true;
145 	if (on_sdei_stack(sp, info))
146 		return true;
147 
148 	return false;
149 }
150 
151 static inline void start_backtrace(struct stackframe *frame,
152 				   unsigned long fp, unsigned long pc)
153 {
154 	frame->fp = fp;
155 	frame->pc = pc;
156 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
157 	frame->graph = 0;
158 #endif
159 
160 	/*
161 	 * Prime the first unwind.
162 	 *
163 	 * In unwind_frame() we'll check that the FP points to a valid stack,
164 	 * which can't be STACK_TYPE_UNKNOWN, and the first unwind will be
165 	 * treated as a transition to whichever stack that happens to be. The
166 	 * prev_fp value won't be used, but we set it to 0 such that it is
167 	 * definitely not an accessible stack address.
168 	 */
169 	bitmap_zero(frame->stacks_done, __NR_STACK_TYPES);
170 	frame->prev_fp = 0;
171 	frame->prev_type = STACK_TYPE_UNKNOWN;
172 }
173 
174 #endif	/* __ASM_STACKTRACE_H */
175