sysdeps/powerpc/powerpc64/backtrace.c

   1 /* Return backtrace of current program state.
   2    Copyright (C) 1998-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If
  17    not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include <execinfo.h>
  20 #include <stddef.h>
  21 #include <string.h>
  22 #include <signal.h>
  23 #include <bits/libc-vdso.h>
  24
  25 /* This is the stack layout we see with every stack frame.
  26    Note that every routine is required by the ABI to lay out the stack
  27    like this.
  28
  29             +----------------+        +-----------------+
  30     %r1  -> | %r1 last frame--------> | %r1 last frame--->...  --> NULL
  31             |                |        |                 |
  32             | cr save        |        | cr save   |
  33             |                |        |                 |
  34             | (unused)       |        | return address  |
  35             +----------------+        +-----------------+
  36 */
  37 struct layout
  38 {
  39   struct layout *next;
  40   long condition_register;
  41   void *return_address;
  42 };
  43
  44 /* Since the signal handler is just like any other function it needs to
  45    save/restore its LR and it will save it into callers stack frame.
  46    Since a signal handler doesn't have a caller, the kernel creates a
  47    dummy frame to make it look like it has a caller.  */
  48 struct signal_frame_64 {
  49 #define SIGNAL_FRAMESIZE 128
  50   char            dummy[SIGNAL_FRAMESIZE];
  51   struct ucontext uc;
  52   /* We don't care about the rest, since the IP value is at 'uc' field.  */
  53 };
  54
  55 static inline int
  56 is_sigtramp_address (unsigned long nip)
  57 {
  58 #ifdef SHARED
  59   if (nip == (unsigned long)__vdso_sigtramp_rt64)
  60     return 1;
  61 #endif
  62   return 0;
  63 }
  64
  65 int
  66 __backtrace (void **array, int size)
  67 {
  68   struct layout *current;
  69   int count;
  70
  71   /* Force gcc to spill LR.  */
  72   asm volatile ("" : "=l"(current));
  73
  74   /* Get the address on top-of-stack.  */
  75   asm volatile ("ld %0,0(1)" : "=r"(current));
  76
  77   for (                         count = 0;
  78        current != NULL &&       count < size;
  79        current = current->next, count++)
  80     {
  81       array[count] = current->return_address;
  82
  83       /* Check if the symbol is the signal trampoline and get the interrupted
  84        * symbol address from the trampoline saved area.  */
  85       if (is_sigtramp_address ((unsigned long)current->return_address))
  86         {
  87           struct signal_frame_64 *sigframe = (struct signal_frame_64*) current;
  88           array[++count] = (void*)sigframe->uc.uc_mcontext.gp_regs[PT_NIP];
  89         }
  90     }
  91
  92   /* It's possible the second-last stack frame can't return
  93      (that is, it's __libc_start_main), in which case
  94      the CRT startup code will have set its LR to 'NULL'.  */
  95   if (count > 0 && array[count-1] == NULL)
  96     count--;
  97
  98   return count;
  99 }
 100 weak_alias (__backtrace, backtrace)
 101 libc_hidden_def (__backtrace)