2 * Stack tracing support
4 * Copyright (C) 2012 ARM Ltd.
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.
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.
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/>.
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>
25 #include <asm/stacktrace.h>
28 * AArch64 PCS assigns the frame pointer to x29.
30 * A simple function prologue looks like this:
35 * A simple function epilogue looks like this:
40 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
42 unsigned long high, low;
43 unsigned long fp = frame->fp;
44 unsigned long irq_stack_ptr;
50 * Switching between stacks is valid when tracing current and in
51 * non-preemptible context.
53 if (tsk == current && !preemptible())
54 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
59 /* irq stacks are not THREAD_SIZE aligned */
60 if (on_irq_stack(frame->sp, raw_smp_processor_id()))
63 high = ALIGN(low, THREAD_SIZE) - 0x20;
65 if (fp < low || fp > high || fp & 0xf)
68 frame->sp = fp + 0x10;
69 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
70 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
72 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
74 (frame->pc == (unsigned long)return_to_handler)) {
76 * This is a case where function graph tracer has
77 * modified a return address (LR) in a stack frame
78 * to hook a function return.
79 * So replace it to an original value.
81 frame->pc = tsk->ret_stack[frame->graph--].ret;
83 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
86 * Check whether we are going to walk through from interrupt stack
88 * If we reach the end of the stack - and its an interrupt stack,
89 * unpack the dummy frame to find the original elr.
91 * Check the frame->fp we read from the bottom of the irq_stack,
92 * and the original task stack pointer are both in current->stack.
94 if (frame->sp == irq_stack_ptr) {
95 struct pt_regs *irq_args;
96 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
98 if (object_is_on_stack((void *)orig_sp) &&
99 object_is_on_stack((void *)frame->fp)) {
102 /* orig_sp is the saved pt_regs, find the elr */
103 irq_args = (struct pt_regs *)orig_sp;
104 frame->pc = irq_args->pc;
107 * This frame has a non-standard format, and we
108 * didn't fix it, because the data looked wrong.
109 * Refuse to output this frame.
118 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
119 int (*fn)(struct stackframe *, void *), void *data)
126 ret = unwind_frame(tsk, frame);
131 EXPORT_SYMBOL(walk_stackframe);
133 #ifdef CONFIG_STACKTRACE
134 struct stack_trace_data {
135 struct stack_trace *trace;
136 unsigned int no_sched_functions;
140 static int save_trace(struct stackframe *frame, void *d)
142 struct stack_trace_data *data = d;
143 struct stack_trace *trace = data->trace;
144 unsigned long addr = frame->pc;
146 if (data->no_sched_functions && in_sched_functions(addr))
153 trace->entries[trace->nr_entries++] = addr;
155 return trace->nr_entries >= trace->max_entries;
158 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
160 struct stack_trace_data data;
161 struct stackframe frame;
164 data.skip = trace->skip;
165 data.no_sched_functions = 0;
167 frame.fp = regs->regs[29];
170 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
171 frame.graph = current->curr_ret_stack;
174 walk_stackframe(current, &frame, save_trace, &data);
175 if (trace->nr_entries < trace->max_entries)
176 trace->entries[trace->nr_entries++] = ULONG_MAX;
179 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
181 struct stack_trace_data data;
182 struct stackframe frame;
185 data.skip = trace->skip;
187 if (tsk != current) {
188 data.no_sched_functions = 1;
189 frame.fp = thread_saved_fp(tsk);
190 frame.sp = thread_saved_sp(tsk);
191 frame.pc = thread_saved_pc(tsk);
193 data.no_sched_functions = 0;
194 frame.fp = (unsigned long)__builtin_frame_address(0);
195 frame.sp = current_stack_pointer;
196 frame.pc = (unsigned long)save_stack_trace_tsk;
198 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
199 frame.graph = tsk->curr_ret_stack;
202 walk_stackframe(tsk, &frame, save_trace, &data);
203 if (trace->nr_entries < trace->max_entries)
204 trace->entries[trace->nr_entries++] = ULONG_MAX;
207 void save_stack_trace(struct stack_trace *trace)
209 save_stack_trace_tsk(current, trace);
211 EXPORT_SYMBOL_GPL(save_stack_trace);