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Linux/arch/arm/kernel/stacktrace.c

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  1 #include <linux/export.h>
  2 #include <linux/sched.h>
  3 #include <linux/sched/debug.h>
  4 #include <linux/stacktrace.h>
  5 
  6 #include <asm/sections.h>
  7 #include <asm/stacktrace.h>
  8 #include <asm/traps.h>
  9 
 10 #if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
 11 /*
 12  * Unwind the current stack frame and store the new register values in the
 13  * structure passed as argument. Unwinding is equivalent to a function return,
 14  * hence the new PC value rather than LR should be used for backtrace.
 15  *
 16  * With framepointer enabled, a simple function prologue looks like this:
 17  *      mov     ip, sp
 18  *      stmdb   sp!, {fp, ip, lr, pc}
 19  *      sub     fp, ip, #4
 20  *
 21  * A simple function epilogue looks like this:
 22  *      ldm     sp, {fp, sp, pc}
 23  *
 24  * Note that with framepointer enabled, even the leaf functions have the same
 25  * prologue and epilogue, therefore we can ignore the LR value in this case.
 26  */
 27 int notrace unwind_frame(struct stackframe *frame)
 28 {
 29         unsigned long high, low;
 30         unsigned long fp = frame->fp;
 31 
 32         /* only go to a higher address on the stack */
 33         low = frame->sp;
 34         high = ALIGN(low, THREAD_SIZE);
 35 
 36         /* check current frame pointer is within bounds */
 37         if (fp < low + 12 || fp > high - 4)
 38                 return -EINVAL;
 39 
 40         /* restore the registers from the stack frame */
 41         frame->fp = *(unsigned long *)(fp - 12);
 42         frame->sp = *(unsigned long *)(fp - 8);
 43         frame->pc = *(unsigned long *)(fp - 4);
 44 
 45         return 0;
 46 }
 47 #endif
 48 
 49 void notrace walk_stackframe(struct stackframe *frame,
 50                      int (*fn)(struct stackframe *, void *), void *data)
 51 {
 52         while (1) {
 53                 int ret;
 54 
 55                 if (fn(frame, data))
 56                         break;
 57                 ret = unwind_frame(frame);
 58                 if (ret < 0)
 59                         break;
 60         }
 61 }
 62 EXPORT_SYMBOL(walk_stackframe);
 63 
 64 #ifdef CONFIG_STACKTRACE
 65 struct stack_trace_data {
 66         struct stack_trace *trace;
 67         unsigned int no_sched_functions;
 68         unsigned int skip;
 69 };
 70 
 71 static int save_trace(struct stackframe *frame, void *d)
 72 {
 73         struct stack_trace_data *data = d;
 74         struct stack_trace *trace = data->trace;
 75         struct pt_regs *regs;
 76         unsigned long addr = frame->pc;
 77 
 78         if (data->no_sched_functions && in_sched_functions(addr))
 79                 return 0;
 80         if (data->skip) {
 81                 data->skip--;
 82                 return 0;
 83         }
 84 
 85         trace->entries[trace->nr_entries++] = addr;
 86 
 87         if (trace->nr_entries >= trace->max_entries)
 88                 return 1;
 89 
 90         if (!in_entry_text(frame->pc))
 91                 return 0;
 92 
 93         regs = (struct pt_regs *)frame->sp;
 94 
 95         trace->entries[trace->nr_entries++] = regs->ARM_pc;
 96 
 97         return trace->nr_entries >= trace->max_entries;
 98 }
 99 
100 /* This must be noinline to so that our skip calculation works correctly */
101 static noinline void __save_stack_trace(struct task_struct *tsk,
102         struct stack_trace *trace, unsigned int nosched)
103 {
104         struct stack_trace_data data;
105         struct stackframe frame;
106 
107         data.trace = trace;
108         data.skip = trace->skip;
109         data.no_sched_functions = nosched;
110 
111         if (tsk != current) {
112 #ifdef CONFIG_SMP
113                 /*
114                  * What guarantees do we have here that 'tsk' is not
115                  * running on another CPU?  For now, ignore it as we
116                  * can't guarantee we won't explode.
117                  */
118                 if (trace->nr_entries < trace->max_entries)
119                         trace->entries[trace->nr_entries++] = ULONG_MAX;
120                 return;
121 #else
122                 frame.fp = thread_saved_fp(tsk);
123                 frame.sp = thread_saved_sp(tsk);
124                 frame.lr = 0;           /* recovered from the stack */
125                 frame.pc = thread_saved_pc(tsk);
126 #endif
127         } else {
128                 /* We don't want this function nor the caller */
129                 data.skip += 2;
130                 frame.fp = (unsigned long)__builtin_frame_address(0);
131                 frame.sp = current_stack_pointer;
132                 frame.lr = (unsigned long)__builtin_return_address(0);
133                 frame.pc = (unsigned long)__save_stack_trace;
134         }
135 
136         walk_stackframe(&frame, save_trace, &data);
137         if (trace->nr_entries < trace->max_entries)
138                 trace->entries[trace->nr_entries++] = ULONG_MAX;
139 }
140 
141 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
142 {
143         struct stack_trace_data data;
144         struct stackframe frame;
145 
146         data.trace = trace;
147         data.skip = trace->skip;
148         data.no_sched_functions = 0;
149 
150         frame.fp = regs->ARM_fp;
151         frame.sp = regs->ARM_sp;
152         frame.lr = regs->ARM_lr;
153         frame.pc = regs->ARM_pc;
154 
155         walk_stackframe(&frame, save_trace, &data);
156         if (trace->nr_entries < trace->max_entries)
157                 trace->entries[trace->nr_entries++] = ULONG_MAX;
158 }
159 
160 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
161 {
162         __save_stack_trace(tsk, trace, 1);
163 }
164 EXPORT_SYMBOL(save_stack_trace_tsk);
165 
166 void save_stack_trace(struct stack_trace *trace)
167 {
168         __save_stack_trace(current, trace, 0);
169 }
170 EXPORT_SYMBOL_GPL(save_stack_trace);
171 #endif
172 

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