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 * When compiled with clang, pc and sp are not pushed. A simple function
26 * prologue looks like this when built with clang:
32 * A simple function epilogue looks like this when built with clang:
38 * Note that with framepointer enabled, even the leaf functions have the same
39 * prologue and epilogue, therefore we can ignore the LR value in this case.
41 int notrace unwind_frame(struct stackframe *frame)
43 unsigned long high, low;
44 unsigned long fp = frame->fp;
46 /* only go to a higher address on the stack */
48 high = ALIGN(low, THREAD_SIZE);
50 #ifdef CONFIG_CC_IS_CLANG
51 /* check current frame pointer is within bounds */
52 if (fp < low + 4 || fp > high - 4)
55 frame->sp = frame->fp;
56 frame->fp = *(unsigned long *)(fp);
57 frame->pc = frame->lr;
58 frame->lr = *(unsigned long *)(fp + 4);
60 /* check current frame pointer is within bounds */
61 if (fp < low + 12 || fp > high - 4)
64 /* restore the registers from the stack frame */
65 frame->fp = *(unsigned long *)(fp - 12);
66 frame->sp = *(unsigned long *)(fp - 8);
67 frame->pc = *(unsigned long *)(fp - 4);
74 void notrace walk_stackframe(struct stackframe *frame,
75 int (*fn)(struct stackframe *, void *), void *data)
82 ret = unwind_frame(frame);
87 EXPORT_SYMBOL(walk_stackframe);
89 #ifdef CONFIG_STACKTRACE
90 struct stack_trace_data {
91 struct stack_trace *trace;
92 unsigned int no_sched_functions;
96 static int save_trace(struct stackframe *frame, void *d)
98 struct stack_trace_data *data = d;
99 struct stack_trace *trace = data->trace;
100 struct pt_regs *regs;
101 unsigned long addr = frame->pc;
103 if (data->no_sched_functions && in_sched_functions(addr))
110 trace->entries[trace->nr_entries++] = addr;
112 if (trace->nr_entries >= trace->max_entries)
115 if (!in_entry_text(frame->pc))
118 regs = (struct pt_regs *)frame->sp;
119 if ((unsigned long)®s[1] > ALIGN(frame->sp, THREAD_SIZE))
122 trace->entries[trace->nr_entries++] = regs->ARM_pc;
124 return trace->nr_entries >= trace->max_entries;
127 /* This must be noinline to so that our skip calculation works correctly */
128 static noinline void __save_stack_trace(struct task_struct *tsk,
129 struct stack_trace *trace, unsigned int nosched)
131 struct stack_trace_data data;
132 struct stackframe frame;
135 data.skip = trace->skip;
136 data.no_sched_functions = nosched;
138 if (tsk != current) {
141 * What guarantees do we have here that 'tsk' is not
142 * running on another CPU? For now, ignore it as we
143 * can't guarantee we won't explode.
147 frame.fp = thread_saved_fp(tsk);
148 frame.sp = thread_saved_sp(tsk);
149 frame.lr = 0; /* recovered from the stack */
150 frame.pc = thread_saved_pc(tsk);
153 /* We don't want this function nor the caller */
155 frame.fp = (unsigned long)__builtin_frame_address(0);
156 frame.sp = current_stack_pointer;
157 frame.lr = (unsigned long)__builtin_return_address(0);
158 frame.pc = (unsigned long)__save_stack_trace;
161 walk_stackframe(&frame, save_trace, &data);
164 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
166 struct stack_trace_data data;
167 struct stackframe frame;
170 data.skip = trace->skip;
171 data.no_sched_functions = 0;
173 frame.fp = regs->ARM_fp;
174 frame.sp = regs->ARM_sp;
175 frame.lr = regs->ARM_lr;
176 frame.pc = regs->ARM_pc;
178 walk_stackframe(&frame, save_trace, &data);
181 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
183 __save_stack_trace(tsk, trace, 1);
185 EXPORT_SYMBOL(save_stack_trace_tsk);
187 void save_stack_trace(struct stack_trace *trace)
189 __save_stack_trace(current, trace, 0);
191 EXPORT_SYMBOL_GPL(save_stack_trace);