LXR linux/arch/arm/kernel/stacktrace.c

   1#include <linux/module.h>
   2#include <linux/sched.h>
   3#include <linux/stacktrace.h>
   4
   5#include <asm/stacktrace.h>
   6
   7#if defined(CONFIG_FRAME_POINTER) && !defined(CONFIG_ARM_UNWIND)
   8/*
   9 * Unwind the current stack frame and store the new register values in the
  10 * structure passed as argument. Unwinding is equivalent to a function return,
  11 * hence the new PC value rather than LR should be used for backtrace.
  12 *
  13 * With framepointer enabled, a simple function prologue looks like this:
  14 *      mov     ip, sp
  15 *      stmdb   sp!, {fp, ip, lr, pc}
  16 *      sub     fp, ip, #4
  17 *
  18 * A simple function epilogue looks like this:
  19 *      ldm     sp, {fp, sp, pc}
  20 *
  21 * Note that with framepointer enabled, even the leaf functions have the same
  22 * prologue and epilogue, therefore we can ignore the LR value in this case.
  23 */
  24int notrace unwind_frame(struct stackframe *frame)
  25{
  26        unsigned long high, low;
  27        unsigned long fp = frame->fp;
  28
  29        /* only go to a higher address on the stack */
  30        low = frame->sp;
  31        high = ALIGN(low, THREAD_SIZE) + THREAD_SIZE;
  32
  33        /* check current frame pointer is within bounds */
  34        if (fp < (low + 12) || fp + 4 >= high)
  35                return -EINVAL;
  36
  37        /* restore the registers from the stack frame */
  38        frame->fp = *(unsigned long *)(fp - 12);
  39        frame->sp = *(unsigned long *)(fp - 8);
  40        frame->pc = *(unsigned long *)(fp - 4);
  41
  42        return 0;
  43}
  44#endif
  45
  46void notrace walk_stackframe(struct stackframe *frame,
  47                     int (*fn)(struct stackframe *, void *), void *data)
  48{
  49        while (1) {
  50                int ret;
  51
  52                if (fn(frame, data))
  53                        break;
  54                ret = unwind_frame(frame);
  55                if (ret < 0)
  56                        break;
  57        }
  58}
  59EXPORT_SYMBOL(walk_stackframe);
  60
  61#ifdef CONFIG_STACKTRACE
  62struct stack_trace_data {
  63        struct stack_trace *trace;
  64        unsigned int no_sched_functions;
  65        unsigned int skip;
  66};
  67
  68static int save_trace(struct stackframe *frame, void *d)
  69{
  70        struct stack_trace_data *data = d;
  71        struct stack_trace *trace = data->trace;
  72        unsigned long addr = frame->pc;
  73
  74        if (data->no_sched_functions && in_sched_functions(addr))
  75                return 0;
  76        if (data->skip) {
  77                data->skip--;
  78                return 0;
  79        }
  80
  81        trace->entries[trace->nr_entries++] = addr;
  82
  83        return trace->nr_entries >= trace->max_entries;
  84}
  85
  86void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
  87{
  88        struct stack_trace_data data;
  89        struct stackframe frame;
  90
  91        data.trace = trace;
  92        data.skip = trace->skip;
  93
  94        if (tsk != current) {
  95#ifdef CONFIG_SMP
  96                /*
  97                 * What guarantees do we have here that 'tsk'
  98                 * is not running on another CPU?
  99                 */
 100                BUG();
 101#else
 102                data.no_sched_functions = 1;
 103                frame.fp = thread_saved_fp(tsk);
 104                frame.sp = thread_saved_sp(tsk);
 105                frame.lr = 0;           /* recovered from the stack */
 106                frame.pc = thread_saved_pc(tsk);
 107#endif
 108        } else {
 109                register unsigned long current_sp asm ("sp");
 110
 111                data.no_sched_functions = 0;
 112                frame.fp = (unsigned long)__builtin_frame_address(0);
 113                frame.sp = current_sp;
 114                frame.lr = (unsigned long)__builtin_return_address(0);
 115                frame.pc = (unsigned long)save_stack_trace_tsk;
 116        }
 117
 118        walk_stackframe(&frame, save_trace, &data);
 119        if (trace->nr_entries < trace->max_entries)
 120                trace->entries[trace->nr_entries++] = ULONG_MAX;
 121}
 122
 123void save_stack_trace(struct stack_trace *trace)
 124{
 125        save_stack_trace_tsk(current, trace);
 126}
 127EXPORT_SYMBOL_GPL(save_stack_trace);
 128#endif
 129