1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/sched/debug.h>
4 #include <linux/sched/task_stack.h>
5 #include <linux/stacktrace.h>
6 #include <linux/ftrace.h>
7 #include <linux/ptrace.h>
8
9 #ifdef CONFIG_FRAME_POINTER
10
11 struct stackframe {
12 unsigned long fp;
13 unsigned long ra;
14 };
15
walk_stackframe(struct task_struct * task,struct pt_regs * regs,bool (* fn)(unsigned long,void *),void * arg)16 void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
17 bool (*fn)(unsigned long, void *), void *arg)
18 {
19 unsigned long fp, sp, pc;
20
21 if (regs) {
22 fp = frame_pointer(regs);
23 sp = user_stack_pointer(regs);
24 pc = instruction_pointer(regs);
25 } else if (task == NULL || task == current) {
26 const register unsigned long current_sp __asm__ ("sp");
27 const register unsigned long current_fp __asm__ ("r8");
28 fp = current_fp;
29 sp = current_sp;
30 pc = (unsigned long)walk_stackframe;
31 } else {
32 /* task blocked in __switch_to */
33 fp = thread_saved_fp(task);
34 sp = thread_saved_sp(task);
35 pc = thread_saved_lr(task);
36 }
37
38 for (;;) {
39 unsigned long low, high;
40 struct stackframe *frame;
41
42 if (unlikely(!__kernel_text_address(pc) || fn(pc, arg)))
43 break;
44
45 /* Validate frame pointer */
46 low = sp;
47 high = ALIGN(sp, THREAD_SIZE);
48 if (unlikely(fp < low || fp > high || fp & 0x3))
49 break;
50 /* Unwind stack frame */
51 frame = (struct stackframe *)fp;
52 sp = fp;
53 fp = frame->fp;
54 pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
55 (unsigned long *)(fp - 8));
56 }
57 }
58
59 #else /* !CONFIG_FRAME_POINTER */
60
walk_stackframe(struct task_struct * task,struct pt_regs * regs,bool (* fn)(unsigned long,void *),void * arg)61 static void notrace walk_stackframe(struct task_struct *task,
62 struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
63 {
64 unsigned long sp, pc;
65 unsigned long *ksp;
66
67 if (regs) {
68 sp = user_stack_pointer(regs);
69 pc = instruction_pointer(regs);
70 } else if (task == NULL || task == current) {
71 const register unsigned long current_sp __asm__ ("sp");
72 sp = current_sp;
73 pc = (unsigned long)walk_stackframe;
74 } else {
75 /* task blocked in __switch_to */
76 sp = thread_saved_sp(task);
77 pc = thread_saved_lr(task);
78 }
79
80 if (unlikely(sp & 0x3))
81 return;
82
83 ksp = (unsigned long *)sp;
84 while (!kstack_end(ksp)) {
85 if (__kernel_text_address(pc) && unlikely(fn(pc, arg)))
86 break;
87 pc = (*ksp++) - 0x4;
88 }
89 }
90 #endif /* CONFIG_FRAME_POINTER */
91
print_trace_address(unsigned long pc,void * arg)92 static bool print_trace_address(unsigned long pc, void *arg)
93 {
94 print_ip_sym((const char *)arg, pc);
95 return false;
96 }
97
show_stack(struct task_struct * task,unsigned long * sp,const char * loglvl)98 void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
99 {
100 pr_cont("Call Trace:\n");
101 walk_stackframe(task, NULL, print_trace_address, (void *)loglvl);
102 }
103
save_wchan(unsigned long pc,void * arg)104 static bool save_wchan(unsigned long pc, void *arg)
105 {
106 if (!in_sched_functions(pc)) {
107 unsigned long *p = arg;
108 *p = pc;
109 return true;
110 }
111 return false;
112 }
113
get_wchan(struct task_struct * task)114 unsigned long get_wchan(struct task_struct *task)
115 {
116 unsigned long pc = 0;
117
118 if (likely(task && task != current && task->state != TASK_RUNNING))
119 walk_stackframe(task, NULL, save_wchan, &pc);
120 return pc;
121 }
122
123 #ifdef CONFIG_STACKTRACE
__save_trace(unsigned long pc,void * arg,bool nosched)124 static bool __save_trace(unsigned long pc, void *arg, bool nosched)
125 {
126 struct stack_trace *trace = arg;
127
128 if (unlikely(nosched && in_sched_functions(pc)))
129 return false;
130 if (unlikely(trace->skip > 0)) {
131 trace->skip--;
132 return false;
133 }
134
135 trace->entries[trace->nr_entries++] = pc;
136 return (trace->nr_entries >= trace->max_entries);
137 }
138
save_trace(unsigned long pc,void * arg)139 static bool save_trace(unsigned long pc, void *arg)
140 {
141 return __save_trace(pc, arg, false);
142 }
143
144 /*
145 * Save stack-backtrace addresses into a stack_trace buffer.
146 */
save_stack_trace_tsk(struct task_struct * tsk,struct stack_trace * trace)147 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
148 {
149 walk_stackframe(tsk, NULL, save_trace, trace);
150 }
151 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
152
save_stack_trace(struct stack_trace * trace)153 void save_stack_trace(struct stack_trace *trace)
154 {
155 save_stack_trace_tsk(NULL, trace);
156 }
157 EXPORT_SYMBOL_GPL(save_stack_trace);
158
159 #endif /* CONFIG_STACKTRACE */
160