1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * Common arm64 stack unwinder code. 4 * 5 * See: arch/arm64/kernel/stacktrace.c for the reference implementation. 6 * 7 * Copyright (C) 2012 ARM Ltd. 8 */ 9 #ifndef __ASM_STACKTRACE_COMMON_H 10 #define __ASM_STACKTRACE_COMMON_H 11 12 #include <linux/kprobes.h> 13 #include <linux/types.h> 14 15 struct stack_info { 16 unsigned long low; 17 unsigned long high; 18 }; 19 20 /** 21 * struct unwind_state - state used for robust unwinding. 22 * 23 * @fp: The fp value in the frame record (or the real fp) 24 * @pc: The lr value in the frame record (or the real lr) 25 * 26 * @kr_cur: When KRETPROBES is selected, holds the kretprobe instance 27 * associated with the most recently encountered replacement lr 28 * value. 29 * 30 * @task: The task being unwound. 31 * 32 * @stack: The stack currently being unwound. 33 * @stacks: An array of stacks which can be unwound. 34 * @nr_stacks: The number of stacks in @stacks. 35 */ 36 struct unwind_state { 37 unsigned long fp; 38 unsigned long pc; 39 #ifdef CONFIG_KRETPROBES 40 struct llist_node *kr_cur; 41 #endif 42 struct task_struct *task; 43 44 struct stack_info stack; 45 struct stack_info *stacks; 46 int nr_stacks; 47 }; 48 49 static inline struct stack_info stackinfo_get_unknown(void) 50 { 51 return (struct stack_info) { 52 .low = 0, 53 .high = 0, 54 }; 55 } 56 57 static inline bool stackinfo_on_stack(const struct stack_info *info, 58 unsigned long sp, unsigned long size) 59 { 60 if (!info->low) 61 return false; 62 63 if (sp < info->low || sp + size < sp || sp + size > info->high) 64 return false; 65 66 return true; 67 } 68 69 static inline void unwind_init_common(struct unwind_state *state, 70 struct task_struct *task) 71 { 72 state->task = task; 73 #ifdef CONFIG_KRETPROBES 74 state->kr_cur = NULL; 75 #endif 76 77 state->stack = stackinfo_get_unknown(); 78 } 79 80 static struct stack_info *unwind_find_next_stack(const struct unwind_state *state, 81 unsigned long sp, 82 unsigned long size) 83 { 84 for (int i = 0; i < state->nr_stacks; i++) { 85 struct stack_info *info = &state->stacks[i]; 86 87 if (stackinfo_on_stack(info, sp, size)) 88 return info; 89 } 90 91 return NULL; 92 } 93 94 /** 95 * unwind_consume_stack() - Check if an object is on an accessible stack, 96 * updating stack boundaries so that future unwind steps cannot consume this 97 * object again. 98 * 99 * @state: the current unwind state. 100 * @sp: the base address of the object. 101 * @size: the size of the object. 102 * 103 * Return: 0 upon success, an error code otherwise. 104 */ 105 static inline int unwind_consume_stack(struct unwind_state *state, 106 unsigned long sp, 107 unsigned long size) 108 { 109 struct stack_info *next; 110 111 if (stackinfo_on_stack(&state->stack, sp, size)) 112 goto found; 113 114 next = unwind_find_next_stack(state, sp, size); 115 if (!next) 116 return -EINVAL; 117 118 /* 119 * Stack transitions are strictly one-way, and once we've 120 * transitioned from one stack to another, it's never valid to 121 * unwind back to the old stack. 122 * 123 * Remove the current stack from the list of stacks so that it cannot 124 * be found on a subsequent transition. 125 * 126 * Note that stacks can nest in several valid orders, e.g. 127 * 128 * TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL 129 * TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW 130 * HYP -> OVERFLOW 131 * 132 * ... so we do not check the specific order of stack 133 * transitions. 134 */ 135 state->stack = *next; 136 *next = stackinfo_get_unknown(); 137 138 found: 139 /* 140 * Future unwind steps can only consume stack above this frame record. 141 * Update the current stack to start immediately above it. 142 */ 143 state->stack.low = sp + size; 144 return 0; 145 } 146 147 /** 148 * unwind_next_frame_record() - Unwind to the next frame record. 149 * 150 * @state: the current unwind state. 151 * 152 * Return: 0 upon success, an error code otherwise. 153 */ 154 static inline int 155 unwind_next_frame_record(struct unwind_state *state) 156 { 157 unsigned long fp = state->fp; 158 int err; 159 160 if (fp & 0x7) 161 return -EINVAL; 162 163 err = unwind_consume_stack(state, fp, 16); 164 if (err) 165 return err; 166 167 /* 168 * Record this frame record's values. 169 */ 170 state->fp = READ_ONCE(*(unsigned long *)(fp)); 171 state->pc = READ_ONCE(*(unsigned long *)(fp + 8)); 172 173 return 0; 174 } 175 176 #endif /* __ASM_STACKTRACE_COMMON_H */ 177