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/sched/debug.h>
23 #include <linux/sched/task_stack.h>
24 #include <linux/stacktrace.h>
27 #include <asm/stack_pointer.h>
28 #include <asm/stacktrace.h>
31 * AArch64 PCS assigns the frame pointer to x29.
33 * A simple function prologue looks like this:
38 * A simple function epilogue looks like this:
43 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
45 unsigned long fp = frame->fp;
53 if (!on_accessible_stack(tsk, fp, NULL))
56 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
57 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
59 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
61 (frame->pc == (unsigned long)return_to_handler)) {
62 struct ftrace_ret_stack *ret_stack;
64 * This is a case where function graph tracer has
65 * modified a return address (LR) in a stack frame
66 * to hook a function return.
67 * So replace it to an original value.
69 ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++);
70 if (WARN_ON_ONCE(!ret_stack))
72 frame->pc = ret_stack->ret;
74 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
77 * Frames created upon entry from EL0 have NULL FP and PC values, so
78 * don't bother reporting these. Frames created by __noreturn functions
79 * might have a valid FP even if PC is bogus, so only terminate where
82 if (!frame->fp && !frame->pc)
88 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
89 int (*fn)(struct stackframe *, void *), void *data)
96 ret = unwind_frame(tsk, frame);
102 #ifdef CONFIG_STACKTRACE
103 struct stack_trace_data {
104 struct stack_trace *trace;
105 unsigned int no_sched_functions;
109 static int save_trace(struct stackframe *frame, void *d)
111 struct stack_trace_data *data = d;
112 struct stack_trace *trace = data->trace;
113 unsigned long addr = frame->pc;
115 if (data->no_sched_functions && in_sched_functions(addr))
122 trace->entries[trace->nr_entries++] = addr;
124 return trace->nr_entries >= trace->max_entries;
127 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
129 struct stack_trace_data data;
130 struct stackframe frame;
133 data.skip = trace->skip;
134 data.no_sched_functions = 0;
136 frame.fp = regs->regs[29];
138 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
142 walk_stackframe(current, &frame, save_trace, &data);
143 if (trace->nr_entries < trace->max_entries)
144 trace->entries[trace->nr_entries++] = ULONG_MAX;
146 EXPORT_SYMBOL_GPL(save_stack_trace_regs);
148 static noinline void __save_stack_trace(struct task_struct *tsk,
149 struct stack_trace *trace, unsigned int nosched)
151 struct stack_trace_data data;
152 struct stackframe frame;
154 if (!try_get_task_stack(tsk))
158 data.skip = trace->skip;
159 data.no_sched_functions = nosched;
161 if (tsk != current) {
162 frame.fp = thread_saved_fp(tsk);
163 frame.pc = thread_saved_pc(tsk);
165 /* We don't want this function nor the caller */
167 frame.fp = (unsigned long)__builtin_frame_address(0);
168 frame.pc = (unsigned long)__save_stack_trace;
170 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
174 walk_stackframe(tsk, &frame, save_trace, &data);
175 if (trace->nr_entries < trace->max_entries)
176 trace->entries[trace->nr_entries++] = ULONG_MAX;
180 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
182 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
184 __save_stack_trace(tsk, trace, 1);
187 void save_stack_trace(struct stack_trace *trace)
189 __save_stack_trace(current, trace, 0);
192 EXPORT_SYMBOL_GPL(save_stack_trace);