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