xref: /openbmc/linux/arch/arm/kernel/stacktrace.c (revision 2d7c11bfc91637e5f9bc5f8c9a82aaffcc0e97aa)
17b104bcbSAl Viro #include <linux/module.h>
2f16fb1ecSRussell King #include <linux/sched.h>
3f16fb1ecSRussell King #include <linux/stacktrace.h>
4f16fb1ecSRussell King 
5*2d7c11bfSCatalin Marinas #include <asm/stacktrace.h>
6f16fb1ecSRussell King 
7*2d7c11bfSCatalin Marinas #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
8*2d7c11bfSCatalin Marinas /*
9*2d7c11bfSCatalin Marinas  * Unwind the current stack frame and store the new register values in the
10*2d7c11bfSCatalin Marinas  * structure passed as argument. Unwinding is equivalent to a function return,
11*2d7c11bfSCatalin Marinas  * hence the new PC value rather than LR should be used for backtrace.
12*2d7c11bfSCatalin Marinas  *
13*2d7c11bfSCatalin Marinas  * With framepointer enabled, a simple function prologue looks like this:
14*2d7c11bfSCatalin Marinas  *	mov	ip, sp
15*2d7c11bfSCatalin Marinas  *	stmdb	sp!, {fp, ip, lr, pc}
16*2d7c11bfSCatalin Marinas  *	sub	fp, ip, #4
17*2d7c11bfSCatalin Marinas  *
18*2d7c11bfSCatalin Marinas  * A simple function epilogue looks like this:
19*2d7c11bfSCatalin Marinas  *	ldm	sp, {fp, sp, pc}
20*2d7c11bfSCatalin Marinas  *
21*2d7c11bfSCatalin Marinas  * Note that with framepointer enabled, even the leaf functions have the same
22*2d7c11bfSCatalin Marinas  * prologue and epilogue, therefore we can ignore the LR value in this case.
23*2d7c11bfSCatalin Marinas  */
24*2d7c11bfSCatalin Marinas int unwind_frame(struct stackframe *frame)
25*2d7c11bfSCatalin Marinas {
26*2d7c11bfSCatalin Marinas 	unsigned long high, low;
27*2d7c11bfSCatalin Marinas 	unsigned long fp = frame->fp;
28*2d7c11bfSCatalin Marinas 
29*2d7c11bfSCatalin Marinas 	/* only go to a higher address on the stack */
30*2d7c11bfSCatalin Marinas 	low = frame->sp;
31*2d7c11bfSCatalin Marinas 	high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE;
32*2d7c11bfSCatalin Marinas 
33*2d7c11bfSCatalin Marinas 	/* check current frame pointer is within bounds */
34*2d7c11bfSCatalin Marinas 	if (fp < (low + 12) || fp + 4 >= high)
35*2d7c11bfSCatalin Marinas 		return -EINVAL;
36*2d7c11bfSCatalin Marinas 
37*2d7c11bfSCatalin Marinas 	/* restore the registers from the stack frame */
38*2d7c11bfSCatalin Marinas 	frame->fp = *(unsigned long *)(fp - 12);
39*2d7c11bfSCatalin Marinas 	frame->sp = *(unsigned long *)(fp - 8);
40*2d7c11bfSCatalin Marinas 	frame->pc = *(unsigned long *)(fp - 4);
41*2d7c11bfSCatalin Marinas 
42*2d7c11bfSCatalin Marinas 	return 0;
43*2d7c11bfSCatalin Marinas }
44*2d7c11bfSCatalin Marinas #endif
45*2d7c11bfSCatalin Marinas 
46*2d7c11bfSCatalin Marinas void walk_stackframe(struct stackframe *frame,
47f16fb1ecSRussell King 		     int (*fn)(struct stackframe *, void *), void *data)
48f16fb1ecSRussell King {
49*2d7c11bfSCatalin Marinas 	while (1) {
50*2d7c11bfSCatalin Marinas 		int ret;
51f16fb1ecSRussell King 
52f16fb1ecSRussell King 		if (fn(frame, data))
53f16fb1ecSRussell King 			break;
54*2d7c11bfSCatalin Marinas 		ret = unwind_frame(frame);
55*2d7c11bfSCatalin Marinas 		if (ret < 0)
56*2d7c11bfSCatalin Marinas 			break;
57*2d7c11bfSCatalin Marinas 	}
58f16fb1ecSRussell King }
597b104bcbSAl Viro EXPORT_SYMBOL(walk_stackframe);
60f16fb1ecSRussell King 
61f16fb1ecSRussell King #ifdef CONFIG_STACKTRACE
62f16fb1ecSRussell King struct stack_trace_data {
63f16fb1ecSRussell King 	struct stack_trace *trace;
64f76e9154SNicolas Pitre 	unsigned int no_sched_functions;
65f16fb1ecSRussell King 	unsigned int skip;
66f16fb1ecSRussell King };
67f16fb1ecSRussell King 
68f16fb1ecSRussell King static int save_trace(struct stackframe *frame, void *d)
69f16fb1ecSRussell King {
70f16fb1ecSRussell King 	struct stack_trace_data *data = d;
71f16fb1ecSRussell King 	struct stack_trace *trace = data->trace;
72*2d7c11bfSCatalin Marinas 	unsigned long addr = frame->pc;
73f16fb1ecSRussell King 
74f76e9154SNicolas Pitre 	if (data->no_sched_functions && in_sched_functions(addr))
75f76e9154SNicolas Pitre 		return 0;
76f16fb1ecSRussell King 	if (data->skip) {
77f16fb1ecSRussell King 		data->skip--;
78f16fb1ecSRussell King 		return 0;
79f16fb1ecSRussell King 	}
80f16fb1ecSRussell King 
81f76e9154SNicolas Pitre 	trace->entries[trace->nr_entries++] = addr;
82f16fb1ecSRussell King 
83f16fb1ecSRussell King 	return trace->nr_entries >= trace->max_entries;
84f16fb1ecSRussell King }
85f16fb1ecSRussell King 
86f76e9154SNicolas Pitre void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
87f16fb1ecSRussell King {
88f16fb1ecSRussell King 	struct stack_trace_data data;
89*2d7c11bfSCatalin Marinas 	struct stackframe frame;
90f16fb1ecSRussell King 
91f16fb1ecSRussell King 	data.trace = trace;
92f16fb1ecSRussell King 	data.skip = trace->skip;
93f76e9154SNicolas Pitre 
94f76e9154SNicolas Pitre 	if (tsk != current) {
95f76e9154SNicolas Pitre #ifdef CONFIG_SMP
96f76e9154SNicolas Pitre 		/*
97f76e9154SNicolas Pitre 		 * What guarantees do we have here that 'tsk'
98f76e9154SNicolas Pitre 		 * is not running on another CPU?
99f76e9154SNicolas Pitre 		 */
100f76e9154SNicolas Pitre 		BUG();
101f76e9154SNicolas Pitre #else
102f76e9154SNicolas Pitre 		data.no_sched_functions = 1;
103*2d7c11bfSCatalin Marinas 		frame.fp = thread_saved_fp(tsk);
104*2d7c11bfSCatalin Marinas 		frame.sp = thread_saved_sp(tsk);
105*2d7c11bfSCatalin Marinas 		frame.lr = 0;		/* recovered from the stack */
106*2d7c11bfSCatalin Marinas 		frame.pc = thread_saved_pc(tsk);
107f76e9154SNicolas Pitre #endif
108f76e9154SNicolas Pitre 	} else {
109*2d7c11bfSCatalin Marinas 		register unsigned long current_sp asm ("sp");
110*2d7c11bfSCatalin Marinas 
111f76e9154SNicolas Pitre 		data.no_sched_functions = 0;
112*2d7c11bfSCatalin Marinas 		frame.fp = (unsigned long)__builtin_frame_address(0);
113*2d7c11bfSCatalin Marinas 		frame.sp = current_sp;
114*2d7c11bfSCatalin Marinas 		frame.lr = (unsigned long)__builtin_return_address(0);
115*2d7c11bfSCatalin Marinas 		frame.pc = (unsigned long)save_stack_trace_tsk;
116f76e9154SNicolas Pitre 	}
117f16fb1ecSRussell King 
118*2d7c11bfSCatalin Marinas 	walk_stackframe(&frame, save_trace, &data);
119f76e9154SNicolas Pitre 	if (trace->nr_entries < trace->max_entries)
120f76e9154SNicolas Pitre 		trace->entries[trace->nr_entries++] = ULONG_MAX;
121f76e9154SNicolas Pitre }
122f76e9154SNicolas Pitre 
123f76e9154SNicolas Pitre void save_stack_trace(struct stack_trace *trace)
124f76e9154SNicolas Pitre {
125f76e9154SNicolas Pitre 	save_stack_trace_tsk(current, trace);
126f16fb1ecSRussell King }
1277b4c9505SIngo Molnar EXPORT_SYMBOL_GPL(save_stack_trace);
128f16fb1ecSRussell King #endif
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