sysdeps/powerpc/powerpc64/backtrace.c

   1 /* Return backtrace of current program state.
   2    Copyright (C) 1998-2019 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 <stddef.h>
  20 #include <string.h>
  21 #include <signal.h>
  22 #include <stdint.h>
  23
  24 #include <execinfo.h>
  25 #include <libc-vdso.h>
  26
  27 /* This is the stack layout we see with every stack frame.
  28    Note that every routine is required by the ABI to lay out the stack
  29    like this.
  30
  31             +----------------+        +-----------------+
  32     %r1  -> | %r1 last frame--------> | %r1 last frame--->...  --> NULL
  33             |                |        |                 |
  34             | cr save        |        | cr save   |
  35             |                |        |                 |
  36             | (unused)       |        | return address  |
  37             +----------------+        +-----------------+
  38 */
  39 struct layout
  40 {
  41   struct layout *next;
  42   long int condition_register;
  43   void *return_address;
  44 };
  45
  46 /* Since the signal handler is just like any other function it needs to
  47    save/restore its LR and it will save it into callers stack frame.
  48    Since a signal handler doesn't have a caller, the kernel creates a
  49    dummy frame to make it look like it has a caller.  */
  50 struct signal_frame_64 {
  51 #define SIGNAL_FRAMESIZE 128
  52   char dummy[SIGNAL_FRAMESIZE];
  53   ucontext_t uc;
  54   /* We don't care about the rest, since the IP value is at 'uc' field.  */
  55 };
  56
  57 static inline int
  58 is_sigtramp_address (void *nip)
  59 {
  60 #ifdef SHARED
  61   if (nip == VDSO_SYMBOL (sigtramp_rt64))
  62     return 1;
  63 #endif
  64   return 0;
  65 }
  66
  67 int
  68 __backtrace (void **array, int size)
  69 {
  70   struct layout *current;
  71   int count;
  72
  73   /* Force gcc to spill LR.  */
  74   asm volatile ("" : "=l"(current));
  75
  76   /* Get the address on top-of-stack.  */
  77   asm volatile ("ld %0,0(1)" : "=r"(current));
  78
  79   for (                         count = 0;
  80        current != NULL &&       count < size;
  81        current = current->next, count++)
  82     {
  83       array[count] = current->return_address;
  84
  85       /* Check if the symbol is the signal trampoline and get the interrupted
  86        * symbol address from the trampoline saved area.  */
  87       if (is_sigtramp_address (current->return_address))
  88         {
  89           struct signal_frame_64 *sigframe = (struct signal_frame_64*) current;
  90           array[++count] = (void*) sigframe->uc.uc_mcontext.gp_regs[PT_NIP];
  91           current = (void*) sigframe->uc.uc_mcontext.gp_regs[PT_R1];
  92         }
  93     }
  94
  95   /* It's possible the second-last stack frame can't return
  96      (that is, it's __libc_start_main), in which case
  97      the CRT startup code will have set its LR to 'NULL'.  */
  98   if (count > 0 && array[count-1] == NULL)
  99     count--;
 100
 101   return count;
 102 }
 103 weak_alias (__backtrace, backtrace)
 104 libc_hidden_def (__backtrace)