1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/export.h>
3 #include <linux/kprobes.h>
4 #include <linux/sched.h>
5 #include <linux/sched/debug.h>
6 #include <linux/stacktrace.h>
8 #include <asm/sections.h>
9 #include <asm/stacktrace.h>
10 #include <asm/traps.h>
14 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
16 * Unwind the current stack frame and store the new register values in the
17 * structure passed as argument. Unwinding is equivalent to a function return,
18 * hence the new PC value rather than LR should be used for backtrace.
20 * With framepointer enabled, a simple function prologue looks like this:
22 * stmdb sp!, {fp, ip, lr, pc}
25 * A simple function epilogue looks like this:
26 * ldm sp, {fp, sp, pc}
28 * When compiled with clang, pc and sp are not pushed. A simple function
29 * prologue looks like this when built with clang:
35 * A simple function epilogue looks like this when built with clang:
41 * Note that with framepointer enabled, even the leaf functions have the same
42 * prologue and epilogue, therefore we can ignore the LR value in this case.
45 extern unsigned long call_with_stack_end;
47 static int frame_pointer_check(struct stackframe *frame)
49 unsigned long high, low;
50 unsigned long fp = frame->fp;
51 unsigned long pc = frame->pc;
54 * call_with_stack() is the only place we allow SP to jump from one
55 * stack to another, with FP and SP pointing to different stacks,
56 * skipping the FP boundary check at this point.
58 if (pc >= (unsigned long)&call_with_stack &&
59 pc < (unsigned long)&call_with_stack_end)
62 /* only go to a higher address on the stack */
64 high = ALIGN(low, THREAD_SIZE);
66 /* check current frame pointer is within bounds */
67 #ifdef CONFIG_CC_IS_CLANG
68 if (fp < low + 4 || fp > high - 4)
71 if (fp < low + 12 || fp > high - 4)
78 int notrace unwind_frame(struct stackframe *frame)
80 unsigned long fp = frame->fp;
82 if (frame_pointer_check(frame))
86 * When we unwind through an exception stack, include the saved PC
87 * value into the stack trace.
89 if (frame->ex_frame) {
90 struct pt_regs *regs = (struct pt_regs *)frame->sp;
93 * We check that 'regs + sizeof(struct pt_regs)' (that is,
94 * ®s[1]) does not exceed the bottom of the stack to avoid
95 * accessing data outside the task's stack. This may happen
96 * when frame->ex_frame is a false positive.
98 if ((unsigned long)®s[1] > ALIGN(frame->sp, THREAD_SIZE))
101 frame->pc = regs->ARM_pc;
102 frame->ex_frame = false;
106 /* restore the registers from the stack frame */
107 #ifdef CONFIG_CC_IS_CLANG
108 frame->sp = frame->fp;
109 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
110 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 4));
112 frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 12));
113 frame->sp = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 8));
114 frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp - 4));
116 #ifdef CONFIG_KRETPROBES
117 if (is_kretprobe_trampoline(frame->pc))
118 frame->pc = kretprobe_find_ret_addr(frame->tsk,
119 (void *)frame->fp, &frame->kr_cur);
122 if (in_entry_text(frame->pc))
123 frame->ex_frame = true;
129 void notrace walk_stackframe(struct stackframe *frame,
130 int (*fn)(struct stackframe *, void *), void *data)
137 ret = unwind_frame(frame);
142 EXPORT_SYMBOL(walk_stackframe);
144 #ifdef CONFIG_STACKTRACE
145 struct stack_trace_data {
146 struct stack_trace *trace;
147 unsigned int no_sched_functions;
151 static int save_trace(struct stackframe *frame, void *d)
153 struct stack_trace_data *data = d;
154 struct stack_trace *trace = data->trace;
155 unsigned long addr = frame->pc;
157 if (data->no_sched_functions && in_sched_functions(addr))
164 trace->entries[trace->nr_entries++] = addr;
165 return trace->nr_entries >= trace->max_entries;
168 /* This must be noinline to so that our skip calculation works correctly */
169 static noinline void __save_stack_trace(struct task_struct *tsk,
170 struct stack_trace *trace, unsigned int nosched)
172 struct stack_trace_data data;
173 struct stackframe frame;
176 data.skip = trace->skip;
177 data.no_sched_functions = nosched;
179 if (tsk != current) {
182 * What guarantees do we have here that 'tsk' is not
183 * running on another CPU? For now, ignore it as we
184 * can't guarantee we won't explode.
188 frame.fp = thread_saved_fp(tsk);
189 frame.sp = thread_saved_sp(tsk);
190 frame.lr = 0; /* recovered from the stack */
191 frame.pc = thread_saved_pc(tsk);
194 /* We don't want this function nor the caller */
196 frame.fp = (unsigned long)__builtin_frame_address(0);
197 frame.sp = current_stack_pointer;
198 frame.lr = (unsigned long)__builtin_return_address(0);
200 frame.pc = (unsigned long)&&here;
202 #ifdef CONFIG_KRETPROBES
206 #ifdef CONFIG_UNWINDER_FRAME_POINTER
207 frame.ex_frame = false;
210 walk_stackframe(&frame, save_trace, &data);
213 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
215 struct stack_trace_data data;
216 struct stackframe frame;
219 data.skip = trace->skip;
220 data.no_sched_functions = 0;
222 frame.fp = regs->ARM_fp;
223 frame.sp = regs->ARM_sp;
224 frame.lr = regs->ARM_lr;
225 frame.pc = regs->ARM_pc;
226 #ifdef CONFIG_KRETPROBES
230 #ifdef CONFIG_UNWINDER_FRAME_POINTER
231 frame.ex_frame = in_entry_text(frame.pc);
234 walk_stackframe(&frame, save_trace, &data);
237 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
239 __save_stack_trace(tsk, trace, 1);
241 EXPORT_SYMBOL(save_stack_trace_tsk);
243 void save_stack_trace(struct stack_trace *trace)
245 __save_stack_trace(current, trace, 0);
247 EXPORT_SYMBOL_GPL(save_stack_trace);