1 | /* SPDX-License-Identifier: GPL-2.0 */ |
2 | #include <linux/sched.h> |
3 | #include <linux/sched/task.h> |
4 | #include <linux/sched/task_stack.h> |
5 | #include <linux/interrupt.h> |
6 | #include <asm/sections.h> |
7 | #include <asm/ptrace.h> |
8 | #include <asm/bitops.h> |
9 | #include <asm/stacktrace.h> |
10 | #include <asm/unwind.h> |
11 | |
12 | unsigned long unwind_get_return_address(struct unwind_state *state) |
13 | { |
14 | if (unwind_done(state)) |
15 | return 0; |
16 | return __kernel_text_address(addr: state->ip) ? state->ip : 0; |
17 | } |
18 | EXPORT_SYMBOL_GPL(unwind_get_return_address); |
19 | |
20 | static bool outside_of_stack(struct unwind_state *state, unsigned long sp) |
21 | { |
22 | return (sp <= state->sp) || |
23 | (sp > state->stack_info.end - sizeof(struct stack_frame)); |
24 | } |
25 | |
26 | static bool update_stack_info(struct unwind_state *state, unsigned long sp) |
27 | { |
28 | struct stack_info *info = &state->stack_info; |
29 | unsigned long *mask = &state->stack_mask; |
30 | |
31 | /* New stack pointer leaves the current stack */ |
32 | if (get_stack_info(stack: sp, task: state->task, info, visit_mask: mask) != 0 || |
33 | !on_stack(info, addr: sp, len: sizeof(struct stack_frame))) |
34 | /* 'sp' does not point to a valid stack */ |
35 | return false; |
36 | return true; |
37 | } |
38 | |
39 | static inline bool is_final_pt_regs(struct unwind_state *state, |
40 | struct pt_regs *regs) |
41 | { |
42 | /* user mode or kernel thread pt_regs at the bottom of task stack */ |
43 | if (task_pt_regs(state->task) == regs) |
44 | return true; |
45 | |
46 | /* user mode pt_regs at the bottom of irq stack */ |
47 | return state->stack_info.type == STACK_TYPE_IRQ && |
48 | state->stack_info.end - sizeof(struct pt_regs) == (unsigned long)regs && |
49 | READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE; |
50 | } |
51 | |
52 | bool unwind_next_frame(struct unwind_state *state) |
53 | { |
54 | struct stack_info *info = &state->stack_info; |
55 | struct stack_frame *sf; |
56 | struct pt_regs *regs; |
57 | unsigned long sp, ip; |
58 | bool reliable; |
59 | |
60 | regs = state->regs; |
61 | if (unlikely(regs)) { |
62 | sp = state->sp; |
63 | sf = (struct stack_frame *) sp; |
64 | ip = READ_ONCE_NOCHECK(sf->gprs[8]); |
65 | reliable = false; |
66 | regs = NULL; |
67 | /* skip bogus %r14 or if is the same as regs->psw.addr */ |
68 | if (!__kernel_text_address(addr: ip) || state->ip == unwind_recover_ret_addr(state, ip)) { |
69 | state->regs = NULL; |
70 | return unwind_next_frame(state); |
71 | } |
72 | } else { |
73 | sf = (struct stack_frame *) state->sp; |
74 | sp = READ_ONCE_NOCHECK(sf->back_chain); |
75 | if (likely(sp)) { |
76 | /* Non-zero back-chain points to the previous frame */ |
77 | if (unlikely(outside_of_stack(state, sp))) { |
78 | if (!update_stack_info(state, sp)) |
79 | goto out_err; |
80 | } |
81 | sf = (struct stack_frame *) sp; |
82 | ip = READ_ONCE_NOCHECK(sf->gprs[8]); |
83 | reliable = true; |
84 | } else { |
85 | /* No back-chain, look for a pt_regs structure */ |
86 | sp = state->sp + STACK_FRAME_OVERHEAD; |
87 | if (!on_stack(info, addr: sp, len: sizeof(struct pt_regs))) |
88 | goto out_err; |
89 | regs = (struct pt_regs *) sp; |
90 | if (is_final_pt_regs(state, regs)) |
91 | goto out_stop; |
92 | ip = READ_ONCE_NOCHECK(regs->psw.addr); |
93 | sp = READ_ONCE_NOCHECK(regs->gprs[15]); |
94 | if (unlikely(outside_of_stack(state, sp))) { |
95 | if (!update_stack_info(state, sp)) |
96 | goto out_err; |
97 | } |
98 | reliable = true; |
99 | } |
100 | } |
101 | |
102 | /* Sanity check: ABI requires SP to be aligned 8 bytes. */ |
103 | if (sp & 0x7) |
104 | goto out_err; |
105 | |
106 | /* Update unwind state */ |
107 | state->sp = sp; |
108 | state->regs = regs; |
109 | state->reliable = reliable; |
110 | state->ip = unwind_recover_ret_addr(state, ip); |
111 | return true; |
112 | |
113 | out_err: |
114 | state->error = true; |
115 | out_stop: |
116 | state->stack_info.type = STACK_TYPE_UNKNOWN; |
117 | return false; |
118 | } |
119 | EXPORT_SYMBOL_GPL(unwind_next_frame); |
120 | |
121 | void __unwind_start(struct unwind_state *state, struct task_struct *task, |
122 | struct pt_regs *regs, unsigned long first_frame) |
123 | { |
124 | struct stack_info *info = &state->stack_info; |
125 | struct stack_frame *sf; |
126 | unsigned long ip, sp; |
127 | |
128 | memset(state, 0, sizeof(*state)); |
129 | state->task = task; |
130 | state->regs = regs; |
131 | |
132 | /* Don't even attempt to start from user mode regs: */ |
133 | if (regs && user_mode(regs)) { |
134 | info->type = STACK_TYPE_UNKNOWN; |
135 | return; |
136 | } |
137 | |
138 | /* Get the instruction pointer from pt_regs or the stack frame */ |
139 | if (regs) { |
140 | ip = regs->psw.addr; |
141 | sp = regs->gprs[15]; |
142 | } else if (task == current) { |
143 | sp = current_frame_address(); |
144 | } else { |
145 | sp = task->thread.ksp; |
146 | } |
147 | |
148 | /* Get current stack pointer and initialize stack info */ |
149 | if (!update_stack_info(state, sp)) { |
150 | /* Something is wrong with the stack pointer */ |
151 | info->type = STACK_TYPE_UNKNOWN; |
152 | state->error = true; |
153 | return; |
154 | } |
155 | |
156 | if (!regs) { |
157 | /* Stack frame is within valid stack */ |
158 | sf = (struct stack_frame *)sp; |
159 | ip = READ_ONCE_NOCHECK(sf->gprs[8]); |
160 | } |
161 | |
162 | /* Update unwind state */ |
163 | state->sp = sp; |
164 | state->reliable = true; |
165 | state->ip = unwind_recover_ret_addr(state, ip); |
166 | |
167 | if (!first_frame) |
168 | return; |
169 | /* Skip through the call chain to the specified starting frame */ |
170 | while (!unwind_done(state)) { |
171 | if (on_stack(info: &state->stack_info, addr: first_frame, len: sizeof(struct stack_frame))) { |
172 | if (state->sp >= first_frame) |
173 | break; |
174 | } |
175 | unwind_next_frame(state); |
176 | } |
177 | } |
178 | EXPORT_SYMBOL_GPL(__unwind_start); |
179 | |