1#include <linux/export.h>
2#include <linux/sched.h>
3#include <linux/stacktrace.h>
4
5#include <asm/stacktrace.h>
6#include <asm/traps.h>
7
8#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
9/*
10 * Unwind the current stack frame and store the new register values in the
11 * structure passed as argument. Unwinding is equivalent to a function return,
12 * hence the new PC value rather than LR should be used for backtrace.
13 *
14 * With framepointer enabled, a simple function prologue looks like this:
15 *	mov	ip, sp
16 *	stmdb	sp!, {fp, ip, lr, pc}
17 *	sub	fp, ip, #4
18 *
19 * A simple function epilogue looks like this:
20 *	ldm	sp, {fp, sp, pc}
21 *
22 * Note that with framepointer enabled, even the leaf functions have the same
23 * prologue and epilogue, therefore we can ignore the LR value in this case.
24 */
25int notrace unwind_frame(struct stackframe *frame)
26{
27	unsigned long high, low;
28	unsigned long fp = frame->fp;
29
30	/* only go to a higher address on the stack */
31	low = frame->sp;
32	high = ALIGN(low, THREAD_SIZE);
33
34	/* check current frame pointer is within bounds */
35	if (fp < low + 12 || fp > high - 4)
36		return -EINVAL;
37
38	/* restore the registers from the stack frame */
39	frame->fp = *(unsigned long *)(fp - 12);
40	frame->sp = *(unsigned long *)(fp - 8);
41	frame->pc = *(unsigned long *)(fp - 4);
42
43	return 0;
44}
45#endif
46
47void notrace walk_stackframe(struct stackframe *frame,
48		     int (*fn)(struct stackframe *, void *), void *data)
49{
50	while (1) {
51		int ret;
52
53		if (fn(frame, data))
54			break;
55		ret = unwind_frame(frame);
56		if (ret < 0)
57			break;
58	}
59}
60EXPORT_SYMBOL(walk_stackframe);
61
62#ifdef CONFIG_STACKTRACE
63struct stack_trace_data {
64	struct stack_trace *trace;
65	unsigned long last_pc;
66	unsigned int no_sched_functions;
67	unsigned int skip;
68};
69
70static int save_trace(struct stackframe *frame, void *d)
71{
72	struct stack_trace_data *data = d;
73	struct stack_trace *trace = data->trace;
74	struct pt_regs *regs;
75	unsigned long addr = frame->pc;
76
77	if (data->no_sched_functions && in_sched_functions(addr))
78		return 0;
79	if (data->skip) {
80		data->skip--;
81		return 0;
82	}
83
84	trace->entries[trace->nr_entries++] = addr;
85
86	if (trace->nr_entries >= trace->max_entries)
87		return 1;
88
89	/*
90	 * in_exception_text() is designed to test if the PC is one of
91	 * the functions which has an exception stack above it, but
92	 * unfortunately what is in frame->pc is the return LR value,
93	 * not the saved PC value.  So, we need to track the previous
94	 * frame PC value when doing this.
95	 */
96	addr = data->last_pc;
97	data->last_pc = frame->pc;
98	if (!in_exception_text(addr))
99		return 0;
100
101	regs = (struct pt_regs *)frame->sp;
102
103	trace->entries[trace->nr_entries++] = regs->ARM_pc;
104
105	return trace->nr_entries >= trace->max_entries;
106}
107
108/* This must be noinline to so that our skip calculation works correctly */
109static noinline void __save_stack_trace(struct task_struct *tsk,
110	struct stack_trace *trace, unsigned int nosched)
111{
112	struct stack_trace_data data;
113	struct stackframe frame;
114
115	data.trace = trace;
116	data.last_pc = ULONG_MAX;
117	data.skip = trace->skip;
118	data.no_sched_functions = nosched;
119
120	if (tsk != current) {
121#ifdef CONFIG_SMP
122		/*
123		 * What guarantees do we have here that 'tsk' is not
124		 * running on another CPU?  For now, ignore it as we
125		 * can't guarantee we won't explode.
126		 */
127		if (trace->nr_entries < trace->max_entries)
128			trace->entries[trace->nr_entries++] = ULONG_MAX;
129		return;
130#else
131		frame.fp = thread_saved_fp(tsk);
132		frame.sp = thread_saved_sp(tsk);
133		frame.lr = 0;		/* recovered from the stack */
134		frame.pc = thread_saved_pc(tsk);
135#endif
136	} else {
137		/* We don't want this function nor the caller */
138		data.skip += 2;
139		frame.fp = (unsigned long)__builtin_frame_address(0);
140		frame.sp = current_stack_pointer;
141		frame.lr = (unsigned long)__builtin_return_address(0);
142		frame.pc = (unsigned long)__save_stack_trace;
143	}
144
145	walk_stackframe(&frame, save_trace, &data);
146	if (trace->nr_entries < trace->max_entries)
147		trace->entries[trace->nr_entries++] = ULONG_MAX;
148}
149
150void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
151{
152	struct stack_trace_data data;
153	struct stackframe frame;
154
155	data.trace = trace;
156	data.skip = trace->skip;
157	data.no_sched_functions = 0;
158
159	frame.fp = regs->ARM_fp;
160	frame.sp = regs->ARM_sp;
161	frame.lr = regs->ARM_lr;
162	frame.pc = regs->ARM_pc;
163
164	walk_stackframe(&frame, save_trace, &data);
165	if (trace->nr_entries < trace->max_entries)
166		trace->entries[trace->nr_entries++] = ULONG_MAX;
167}
168
169void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
170{
171	__save_stack_trace(tsk, trace, 1);
172}
173
174void save_stack_trace(struct stack_trace *trace)
175{
176	__save_stack_trace(current, trace, 0);
177}
178EXPORT_SYMBOL_GPL(save_stack_trace);
179#endif
180