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
is_final_pt_regs(struct unwind_state * state,struct pt_regs * regs)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 /* Avoid KMSAN false positives from touching uninitialized frames. */
53 __no_kmsan_checks
unwind_next_frame(struct unwind_state * state)54 bool unwind_next_frame(struct unwind_state *state)
55 {
56 struct stack_info *info = &state->stack_info;
57 struct stack_frame *sf;
58 struct pt_regs *regs;
59 unsigned long sp, ip;
60 bool reliable;
61
62 regs = state->regs;
63 if (unlikely(regs)) {
64 sp = state->sp;
65 sf = (struct stack_frame *) sp;
66 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
67 reliable = false;
68 regs = NULL;
69 /* skip bogus %r14 or if is the same as regs->psw.addr */
70 if (!__kernel_text_address(ip) || state->ip == unwind_recover_ret_addr(state, ip)) {
71 state->regs = NULL;
72 return unwind_next_frame(state);
73 }
74 } else {
75 sf = (struct stack_frame *) state->sp;
76 sp = READ_ONCE_NOCHECK(sf->back_chain);
77 if (likely(sp)) {
78 /* Non-zero back-chain points to the previous frame */
79 if (unlikely(outside_of_stack(state, sp))) {
80 if (!update_stack_info(state, sp))
81 goto out_err;
82 }
83 sf = (struct stack_frame *) sp;
84 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
85 reliable = true;
86 } else {
87 /* No back-chain, look for a pt_regs structure */
88 sp = state->sp + STACK_FRAME_OVERHEAD;
89 if (!on_stack(info, sp, sizeof(struct pt_regs)))
90 goto out_err;
91 regs = (struct pt_regs *) sp;
92 if (is_final_pt_regs(state, regs))
93 goto out_stop;
94 ip = READ_ONCE_NOCHECK(regs->psw.addr);
95 sp = READ_ONCE_NOCHECK(regs->gprs[15]);
96 if (unlikely(outside_of_stack(state, sp))) {
97 if (!update_stack_info(state, sp))
98 goto out_err;
99 }
100 reliable = true;
101 }
102 }
103
104 /* Sanity check: ABI requires SP to be aligned 8 bytes. */
105 if (sp & 0x7)
106 goto out_err;
107
108 /* Update unwind state */
109 state->sp = sp;
110 state->regs = regs;
111 state->reliable = reliable;
112 state->ip = unwind_recover_ret_addr(state, ip);
113 return true;
114
115 out_err:
116 state->error = true;
117 out_stop:
118 state->stack_info.type = STACK_TYPE_UNKNOWN;
119 return false;
120 }
121 EXPORT_SYMBOL_GPL(unwind_next_frame);
122
123 /* Avoid KMSAN false positives from touching uninitialized frames. */
124 __no_kmsan_checks
__unwind_start(struct unwind_state * state,struct task_struct * task,struct pt_regs * regs,unsigned long first_frame)125 void __unwind_start(struct unwind_state *state, struct task_struct *task,
126 struct pt_regs *regs, unsigned long first_frame)
127 {
128 struct stack_info *info = &state->stack_info;
129 struct stack_frame *sf;
130 unsigned long ip, sp;
131
132 memset(state, 0, sizeof(*state));
133 state->task = task;
134 state->regs = regs;
135
136 /* Don't even attempt to start from user mode regs: */
137 if (regs && user_mode(regs)) {
138 info->type = STACK_TYPE_UNKNOWN;
139 return;
140 }
141
142 /* Get the instruction pointer from pt_regs or the stack frame */
143 if (regs) {
144 ip = regs->psw.addr;
145 sp = regs->gprs[15];
146 } else if (task == current) {
147 sp = current_frame_address();
148 } else {
149 sp = task->thread.ksp;
150 }
151
152 /* Get current stack pointer and initialize stack info */
153 if (!update_stack_info(state, sp)) {
154 /* Something is wrong with the stack pointer */
155 info->type = STACK_TYPE_UNKNOWN;
156 state->error = true;
157 return;
158 }
159
160 if (!regs) {
161 /* Stack frame is within valid stack */
162 sf = (struct stack_frame *)sp;
163 ip = READ_ONCE_NOCHECK(sf->gprs[8]);
164 }
165
166 /* Update unwind state */
167 state->sp = sp;
168 state->reliable = true;
169 state->ip = unwind_recover_ret_addr(state, ip);
170
171 if (!first_frame)
172 return;
173 /* Skip through the call chain to the specified starting frame */
174 while (!unwind_done(state)) {
175 if (on_stack(&state->stack_info, first_frame, sizeof(struct stack_frame))) {
176 if (state->sp >= first_frame)
177 break;
178 }
179 unwind_next_frame(state);
180 }
181 }
182 EXPORT_SYMBOL_GPL(__unwind_start);
183