1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/export.h>
3 #include <linux/sched.h>
4 #include <linux/sched/debug.h>
5 #include <linux/stacktrace.h>
7 #include <asm/sections.h>
8 #include <asm/stacktrace.h>
11 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
13 * Unwind the current stack frame and store the new register values in the
14 * structure passed as argument. Unwinding is equivalent to a function return,
15 * hence the new PC value rather than LR should be used for backtrace.
17 * With framepointer enabled, a simple function prologue looks like this:
19 * stmdb sp!, {fp, ip, lr, pc}
22 * A simple function epilogue looks like this:
23 * ldm sp, {fp, sp, pc}
25 * Note that with framepointer enabled, even the leaf functions have the same
26 * prologue and epilogue, therefore we can ignore the LR value in this case.
28 int notrace unwind_frame(struct stackframe *frame)
30 unsigned long high, low;
31 unsigned long fp = frame->fp;
33 /* only go to a higher address on the stack */
35 high = ALIGN(low, THREAD_SIZE);
37 /* check current frame pointer is within bounds */
38 if (fp < low + 12 || fp > high - 4)
41 /* restore the registers from the stack frame */
42 frame->fp = *(unsigned long *)(fp - 12);
43 frame->sp = *(unsigned long *)(fp - 8);
44 frame->pc = *(unsigned long *)(fp - 4);
50 void notrace walk_stackframe(struct stackframe *frame,
51 int (*fn)(struct stackframe *, void *), void *data)
58 ret = unwind_frame(frame);
63 EXPORT_SYMBOL(walk_stackframe);
65 #ifdef CONFIG_STACKTRACE
66 struct stack_trace_data {
67 struct stack_trace *trace;
68 unsigned int no_sched_functions;
72 static int save_trace(struct stackframe *frame, void *d)
74 struct stack_trace_data *data = d;
75 struct stack_trace *trace = data->trace;
77 unsigned long addr = frame->pc;
79 if (data->no_sched_functions && in_sched_functions(addr))
86 trace->entries[trace->nr_entries++] = addr;
88 if (trace->nr_entries >= trace->max_entries)
91 if (!in_entry_text(frame->pc))
94 regs = (struct pt_regs *)frame->sp;
96 trace->entries[trace->nr_entries++] = regs->ARM_pc;
98 return trace->nr_entries >= trace->max_entries;
101 /* This must be noinline to so that our skip calculation works correctly */
102 static noinline void __save_stack_trace(struct task_struct *tsk,
103 struct stack_trace *trace, unsigned int nosched)
105 struct stack_trace_data data;
106 struct stackframe frame;
109 data.skip = trace->skip;
110 data.no_sched_functions = nosched;
112 if (tsk != current) {
115 * What guarantees do we have here that 'tsk' is not
116 * running on another CPU? For now, ignore it as we
117 * can't guarantee we won't explode.
121 frame.fp = thread_saved_fp(tsk);
122 frame.sp = thread_saved_sp(tsk);
123 frame.lr = 0; /* recovered from the stack */
124 frame.pc = thread_saved_pc(tsk);
127 /* We don't want this function nor the caller */
129 frame.fp = (unsigned long)__builtin_frame_address(0);
130 frame.sp = current_stack_pointer;
131 frame.lr = (unsigned long)__builtin_return_address(0);
132 frame.pc = (unsigned long)__save_stack_trace;
135 walk_stackframe(&frame, save_trace, &data);
138 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
140 struct stack_trace_data data;
141 struct stackframe frame;
144 data.skip = trace->skip;
145 data.no_sched_functions = 0;
147 frame.fp = regs->ARM_fp;
148 frame.sp = regs->ARM_sp;
149 frame.lr = regs->ARM_lr;
150 frame.pc = regs->ARM_pc;
152 walk_stackframe(&frame, save_trace, &data);
155 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
157 __save_stack_trace(tsk, trace, 1);
159 EXPORT_SYMBOL(save_stack_trace_tsk);
161 void save_stack_trace(struct stack_trace *trace)
163 __save_stack_trace(current, trace, 0);
165 EXPORT_SYMBOL_GPL(save_stack_trace);