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/stack_pointer.h>
26 #include <asm/stacktrace.h>
29 * AArch64 PCS assigns the frame pointer to x29.
31 * A simple function prologue looks like this:
36 * A simple function epilogue looks like this:
41 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
43 unsigned long high, low;
44 unsigned long fp = frame->fp;
45 unsigned long irq_stack_ptr;
51 * Switching between stacks is valid when tracing current and in
52 * non-preemptible context.
54 if (tsk == current && !preemptible())
55 irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
60 /* irq stacks are not THREAD_SIZE aligned */
61 if (on_irq_stack(frame->sp, raw_smp_processor_id()))
64 high = ALIGN(low, THREAD_SIZE) - 0x20;
66 if (fp < low || fp > high || fp & 0xf)
69 frame->sp = fp + 0x10;
70 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
71 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
73 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
75 (frame->pc == (unsigned long)return_to_handler)) {
77 * This is a case where function graph tracer has
78 * modified a return address (LR) in a stack frame
79 * to hook a function return.
80 * So replace it to an original value.
82 frame->pc = tsk->ret_stack[frame->graph--].ret;
84 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
87 * Check whether we are going to walk through from interrupt stack
89 * If we reach the end of the stack - and its an interrupt stack,
90 * unpack the dummy frame to find the original elr.
92 * Check the frame->fp we read from the bottom of the irq_stack,
93 * and the original task stack pointer are both in current->stack.
95 if (frame->sp == irq_stack_ptr) {
96 struct pt_regs *irq_args;
97 unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
99 if (object_is_on_stack((void *)orig_sp) &&
100 object_is_on_stack((void *)frame->fp)) {
103 /* orig_sp is the saved pt_regs, find the elr */
104 irq_args = (struct pt_regs *)orig_sp;
105 frame->pc = irq_args->pc;
108 * This frame has a non-standard format, and we
109 * didn't fix it, because the data looked wrong.
110 * Refuse to output this frame.
119 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
120 int (*fn)(struct stackframe *, void *), void *data)
127 ret = unwind_frame(tsk, frame);
132 EXPORT_SYMBOL(walk_stackframe);
134 #ifdef CONFIG_STACKTRACE
135 struct stack_trace_data {
136 struct stack_trace *trace;
137 unsigned int no_sched_functions;
141 static int save_trace(struct stackframe *frame, void *d)
143 struct stack_trace_data *data = d;
144 struct stack_trace *trace = data->trace;
145 unsigned long addr = frame->pc;
147 if (data->no_sched_functions && in_sched_functions(addr))
154 trace->entries[trace->nr_entries++] = addr;
156 return trace->nr_entries >= trace->max_entries;
159 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
161 struct stack_trace_data data;
162 struct stackframe frame;
165 data.skip = trace->skip;
166 data.no_sched_functions = 0;
168 frame.fp = regs->regs[29];
171 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
172 frame.graph = current->curr_ret_stack;
175 walk_stackframe(current, &frame, save_trace, &data);
176 if (trace->nr_entries < trace->max_entries)
177 trace->entries[trace->nr_entries++] = ULONG_MAX;
180 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
182 struct stack_trace_data data;
183 struct stackframe frame;
186 data.skip = trace->skip;
188 if (tsk != current) {
189 data.no_sched_functions = 1;
190 frame.fp = thread_saved_fp(tsk);
191 frame.sp = thread_saved_sp(tsk);
192 frame.pc = thread_saved_pc(tsk);
194 data.no_sched_functions = 0;
195 frame.fp = (unsigned long)__builtin_frame_address(0);
196 frame.sp = current_stack_pointer;
197 frame.pc = (unsigned long)save_stack_trace_tsk;
199 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
200 frame.graph = tsk->curr_ret_stack;
203 walk_stackframe(tsk, &frame, save_trace, &data);
204 if (trace->nr_entries < trace->max_entries)
205 trace->entries[trace->nr_entries++] = ULONG_MAX;
208 void save_stack_trace(struct stack_trace *trace)
210 save_stack_trace_tsk(current, trace);
212 EXPORT_SYMBOL_GPL(save_stack_trace);