sysdeps/powerpc/powerpc32/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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <execinfo.h>
  20 #include <stddef.h>
  21 #include <string.h>
  22 #include <signal.h>
  23 #include <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             | (unused)       |        | return address  |
  33             +----------------+        +-----------------+
  34 */
  35 struct layout
  36 {
  37   struct layout *next;
  38   void *return_address;
  39 };
  40
  41 #define SIGNAL_FRAMESIZE 64
  42
  43 /* Since the signal handler is just like any other function it needs to
  44    save/restore its LR and it will save it into callers stack frame.
  45    Since a signal handler doesn't have a caller, the kernel creates a
  46    dummy frame to make it look like it has a caller.  */
  47 struct signal_frame_32 {
  48   char               dummy[SIGNAL_FRAMESIZE];
  49   struct sigcontext  sctx;
  50   mcontext_t         mctx;
  51   /* We don't care about the rest, since IP value is at 'mctx' field.  */
  52 };
  53
  54 static inline int
  55 is_sigtramp_address (void *nip)
  56 {
  57 #ifdef SHARED
  58   if (nip == VDSO_SYMBOL (sigtramp32))
  59     return 1;
  60 #endif
  61   return 0;
  62 }
  63
  64 struct rt_signal_frame_32 {
  65   char               dummy[SIGNAL_FRAMESIZE + 16];
  66   siginfo_t          info;
  67   ucontext_t         uc;
  68   /* We don't care about the rest, since IP value is at 'uc' field.  */
  69 };
  70
  71 static inline int
  72 is_sigtramp_address_rt (void * nip)
  73 {
  74 #ifdef SHARED
  75   if (nip == VDSO_SYMBOL (sigtramp_rt32))
  76     return 1;
  77 #endif
  78   return 0;
  79 }
  80
  81 int
  82 __backtrace (void **array, int size)
  83 {
  84   struct layout *current;
  85   int count;
  86
  87   /* Force gcc to spill LR.  */
  88   asm volatile ("" : "=l"(current));
  89
  90   /* Get the address on top-of-stack.  */
  91   asm volatile ("lwz %0,0(1)" : "=r"(current));
  92
  93   for (                         count = 0;
  94        current != NULL &&       count < size;
  95        current = current->next, count++)
  96     {
  97       gregset_t *gregset = NULL;
  98
  99       array[count] = current->return_address;
 100
 101       /* Check if the symbol is the signal trampoline and get the interrupted
 102        * symbol address from the trampoline saved area.  */
 103       if (is_sigtramp_address (current->return_address))
 104         {
 105           struct signal_frame_32 *sigframe =
 106             (struct signal_frame_32*) current;
 107           gregset = &sigframe->mctx.gregs;
 108         }
 109       else if (is_sigtramp_address_rt (current->return_address))
 110         {
 111           struct rt_signal_frame_32 *sigframe =
 112             (struct rt_signal_frame_32*) current;
 113           gregset = &sigframe->uc.uc_mcontext.uc_regs->gregs;
 114         }
 115       if (gregset)
 116         {
 117           array[++count] = (void*)((*gregset)[PT_NIP]);
 118           current = (void*)((*gregset)[PT_R1]);
 119         }
 120     }
 121
 122   /* It's possible the second-last stack frame can't return
 123      (that is, it's __libc_start_main), in which case
 124      the CRT startup code will have set its LR to 'NULL'.  */
 125   if (count > 0 && array[count-1] == NULL)
 126     count--;
 127
 128   return count;
 129 }
 130 weak_alias (__backtrace, backtrace)
 131 libc_hidden_def (__backtrace)