1 /*
2 * Stack tracing support
3 *
4 * Copyright (C) 2012 ARM Ltd.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program. If not, see <http://www.gnu.org/licenses/>.
17 */
18 #include <linux/kernel.h>
19 #include <linux/export.h>
20 #include <linux/ftrace.h>
21 #include <linux/sched.h>
22 #include <linux/stacktrace.h>
23
24 #include <asm/irq.h>
25 #include <asm/stack_pointer.h>
26 #include <asm/stacktrace.h>
27
28 /*
29 * AArch64 PCS assigns the frame pointer to x29.
30 *
31 * A simple function prologue looks like this:
32 * sub sp, sp, #0x10
33 * stp x29, x30, [sp]
34 * mov x29, sp
35 *
36 * A simple function epilogue looks like this:
37 * mov sp, x29
38 * ldp x29, x30, [sp]
39 * add sp, sp, #0x10
40 */
unwind_frame(struct task_struct * tsk,struct stackframe * frame)41 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
42 {
43 unsigned long high, low;
44 unsigned long fp = frame->fp;
45 unsigned long irq_stack_ptr;
46
47 /*
48 * Switching between stacks is valid when tracing current and in
49 * non-preemptible context.
50 */
51 if (tsk == current && !preemptible())
52 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
53 else
54 irq_stack_ptr = 0;
55
56 low = frame->sp;
57 /* irq stacks are not THREAD_SIZE aligned */
58 if (on_irq_stack(frame->sp, raw_smp_processor_id()))
59 high = irq_stack_ptr;
60 else
61 high = ALIGN(low, THREAD_SIZE) - 0x20;
62
63 if (fp < low || fp > high || fp & 0xf)
64 return -EINVAL;
65
66 frame->sp = fp + 0x10;
67 frame->fp = *(unsigned long *)(fp);
68 frame->pc = *(unsigned long *)(fp + 8);
69
70 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
71 if (tsk && tsk->ret_stack &&
72 (frame->pc == (unsigned long)return_to_handler)) {
73 if (WARN_ON_ONCE(frame->graph == -1))
74 return -EINVAL;
75 if (frame->graph < -1)
76 frame->graph += FTRACE_NOTRACE_DEPTH;
77
78 /*
79 * This is a case where function graph tracer has
80 * modified a return address (LR) in a stack frame
81 * to hook a function return.
82 * So replace it to an original value.
83 */
84 frame->pc = tsk->ret_stack[frame->graph--].ret;
85 }
86 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
87
88 /*
89 * Check whether we are going to walk through from interrupt stack
90 * to task stack.
91 * If we reach the end of the stack - and its an interrupt stack,
92 * unpack the dummy frame to find the original elr.
93 *
94 * Check the frame->fp we read from the bottom of the irq_stack,
95 * and the original task stack pointer are both in current->stack.
96 */
97 if (frame->sp == irq_stack_ptr) {
98 struct pt_regs *irq_args;
99 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
100
101 if (object_is_on_stack((void *)orig_sp) &&
102 object_is_on_stack((void *)frame->fp)) {
103 frame->sp = orig_sp;
104
105 /* orig_sp is the saved pt_regs, find the elr */
106 irq_args = (struct pt_regs *)orig_sp;
107 frame->pc = irq_args->pc;
108 } else {
109 /*
110 * This frame has a non-standard format, and we
111 * didn't fix it, because the data looked wrong.
112 * Refuse to output this frame.
113 */
114 return -EINVAL;
115 }
116 }
117
118 return 0;
119 }
120
walk_stackframe(struct task_struct * tsk,struct stackframe * frame,int (* fn)(struct stackframe *,void *),void * data)121 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
122 int (*fn)(struct stackframe *, void *), void *data)
123 {
124 while (1) {
125 int ret;
126
127 if (fn(frame, data))
128 break;
129 ret = unwind_frame(tsk, frame);
130 if (ret < 0)
131 break;
132 }
133 }
134
135 #ifdef CONFIG_STACKTRACE
136 struct stack_trace_data {
137 struct stack_trace *trace;
138 unsigned int no_sched_functions;
139 unsigned int skip;
140 };
141
save_trace(struct stackframe * frame,void * d)142 static int save_trace(struct stackframe *frame, void *d)
143 {
144 struct stack_trace_data *data = d;
145 struct stack_trace *trace = data->trace;
146 unsigned long addr = frame->pc;
147
148 if (data->no_sched_functions && in_sched_functions(addr))
149 return 0;
150 if (data->skip) {
151 data->skip--;
152 return 0;
153 }
154
155 trace->entries[trace->nr_entries++] = addr;
156
157 return trace->nr_entries >= trace->max_entries;
158 }
159
save_stack_trace_tsk(struct task_struct * tsk,struct stack_trace * trace)160 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
161 {
162 struct stack_trace_data data;
163 struct stackframe frame;
164
165 if (!try_get_task_stack(tsk))
166 return;
167
168 data.trace = trace;
169 data.skip = trace->skip;
170
171 if (tsk != current) {
172 data.no_sched_functions = 1;
173 frame.fp = thread_saved_fp(tsk);
174 frame.sp = thread_saved_sp(tsk);
175 frame.pc = thread_saved_pc(tsk);
176 } else {
177 data.no_sched_functions = 0;
178 frame.fp = (unsigned long)__builtin_frame_address(0);
179 frame.sp = current_stack_pointer;
180 frame.pc = (unsigned long)save_stack_trace_tsk;
181 }
182 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
183 frame.graph = tsk->curr_ret_stack;
184 #endif
185
186 walk_stackframe(tsk, &frame, save_trace, &data);
187 if (trace->nr_entries < trace->max_entries)
188 trace->entries[trace->nr_entries++] = ULONG_MAX;
189
190 put_task_stack(tsk);
191 }
192
save_stack_trace(struct stack_trace * trace)193 void save_stack_trace(struct stack_trace *trace)
194 {
195 save_stack_trace_tsk(current, trace);
196 }
197 EXPORT_SYMBOL_GPL(save_stack_trace);
198 #endif
199