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
unwind_get_return_address(struct unwind_state * state)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(state->ip) ? state->ip : 0;
17 }
18 EXPORT_SYMBOL_GPL(unwind_get_return_address);
19
outside_of_stack(struct unwind_state * state,unsigned long sp)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
update_stack_info(struct unwind_state * state,unsigned long sp)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(sp, state->task, info, mask) != 0 ||
33 !on_stack(info, sp, sizeof(struct stack_frame)))
34 /* 'sp' does not point to a valid stack */
35 return false;
36 return true;
37 }
38
unwind_next_frame(struct unwind_state * state)39 bool unwind_next_frame(struct unwind_state *state)
40 {
41 struct stack_info *info = &state->stack_info;
42 struct stack_frame *sf;
43 struct pt_regs *regs;
44 unsigned long sp, ip;
45 bool reliable;
46
47 regs = state->regs;
48 if (unlikely(regs)) {
49 if (state->reuse_sp) {
50 sp = state->sp;
51 state->reuse_sp = false;
52 } else {
53 sp = READ_ONCE_NOCHECK(regs->gprs[15]);
54 if (unlikely(outside_of_stack(state, sp))) {
55 if (!update_stack_info(state, sp))
56 goto out_err;
57 }
58 }
59 sf = (struct stack_frame *) sp;
60 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
61 reliable = false;
62 regs = NULL;
63 } else {
64 sf = (struct stack_frame *) state->sp;
65 sp = READ_ONCE_NOCHECK(sf->back_chain);
66 if (likely(sp)) {
67 /* Non-zero back-chain points to the previous frame */
68 if (unlikely(outside_of_stack(state, sp))) {
69 if (!update_stack_info(state, sp))
70 goto out_err;
71 }
72 sf = (struct stack_frame *) sp;
73 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
74 reliable = true;
75 } else {
76 /* No back-chain, look for a pt_regs structure */
77 sp = state->sp + STACK_FRAME_OVERHEAD;
78 if (!on_stack(info, sp, sizeof(struct pt_regs)))
79 goto out_stop;
80 regs = (struct pt_regs *) sp;
81 if (READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE)
82 goto out_stop;
83 ip = READ_ONCE_NOCHECK(regs->psw.addr);
84 reliable = true;
85 }
86 }
87
88 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
89 /* Decode any ftrace redirection */
90 if (ip == (unsigned long) return_to_handler)
91 ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
92 ip, (void *) sp);
93 #endif
94
95 /* Update unwind state */
96 state->sp = sp;
97 state->ip = ip;
98 state->regs = regs;
99 state->reliable = reliable;
100 return true;
101
102 out_err:
103 state->error = true;
104 out_stop:
105 state->stack_info.type = STACK_TYPE_UNKNOWN;
106 return false;
107 }
108 EXPORT_SYMBOL_GPL(unwind_next_frame);
109
__unwind_start(struct unwind_state * state,struct task_struct * task,struct pt_regs * regs,unsigned long sp)110 void __unwind_start(struct unwind_state *state, struct task_struct *task,
111 struct pt_regs *regs, unsigned long sp)
112 {
113 struct stack_info *info = &state->stack_info;
114 unsigned long *mask = &state->stack_mask;
115 bool reliable, reuse_sp;
116 struct stack_frame *sf;
117 unsigned long ip;
118
119 memset(state, 0, sizeof(*state));
120 state->task = task;
121 state->regs = regs;
122
123 /* Don't even attempt to start from user mode regs: */
124 if (regs && user_mode(regs)) {
125 info->type = STACK_TYPE_UNKNOWN;
126 return;
127 }
128
129 /* Get current stack pointer and initialize stack info */
130 if (get_stack_info(sp, task, info, mask) != 0 ||
131 !on_stack(info, sp, sizeof(struct stack_frame))) {
132 /* Something is wrong with the stack pointer */
133 info->type = STACK_TYPE_UNKNOWN;
134 state->error = true;
135 return;
136 }
137
138 /* Get the instruction pointer from pt_regs or the stack frame */
139 if (regs) {
140 ip = READ_ONCE_NOCHECK(regs->psw.addr);
141 reliable = true;
142 reuse_sp = true;
143 } else {
144 sf = (struct stack_frame *) sp;
145 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
146 reliable = false;
147 reuse_sp = false;
148 }
149
150 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
151 /* Decode any ftrace redirection */
152 if (ip == (unsigned long) return_to_handler)
153 ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
154 ip, NULL);
155 #endif
156
157 /* Update unwind state */
158 state->sp = sp;
159 state->ip = ip;
160 state->reliable = reliable;
161 state->reuse_sp = reuse_sp;
162 }
163 EXPORT_SYMBOL_GPL(__unwind_start);
164
