1 /* Return backtrace of current program state.
2 Copyright (C) 2000-2019 Free Software Foundation, Inc.
3 Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>.
4 This file is part of the GNU C Library.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <https://www.gnu.org/licenses/>. */
20 #include <libc-lock.h>
27 /* This is a global variable set at program start time. It marks the
28 highest used stack address. */
29 extern void *__libc_stack_end;
32 /* This is the stack layout we see for every non-leaf function.
34 %r15 -> +------------------+
39 40 | save area r6-r15 | 24
40 16 | save area f4,f6 | 64
43 r14 in the save area holds the return address.
64 static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
65 static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
70 void *handle = __libc_dlopen ("libgcc_s.so.1");
75 unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");
76 unwind_getip = __libc_dlsym (handle, "_Unwind_GetIP");
77 if (unwind_getip == NULL)
78 unwind_backtrace = NULL;
82 __backchain_backtrace (void **array, int size)
84 /* We assume that all the code is generated with frame pointers set. */
88 __asm__ ("LR %0,%%r15" : "=d" (stack) );
89 /* We skip the call to this function, it makes no sense to record it. */
90 stack = (struct layout *) stack->back_chain;
93 if (stack == NULL || (void *) stack > __libc_stack_end)
94 /* This means the address is out of range. Note that for the
95 toplevel we see a frame pointer with value NULL which clearly is
99 array[cnt++] = (void *) (stack->save_grps[8] & 0x7fffffff);
101 stack = (struct layout *) stack->back_chain;
107 # define unwind_backtrace _Unwind_Backtrace
108 # define unwind_getip _Unwind_GetIP
111 static _Unwind_Reason_Code
112 backtrace_helper (struct _Unwind_Context *ctx, void *a)
114 struct trace_arg *arg = a;
116 /* We are first called with address in the __backtrace function.
119 arg->array[arg->cnt] = (void *) unwind_getip (ctx);
120 if (++arg->cnt == arg->size)
121 return _URC_END_OF_STACK;
122 return _URC_NO_REASON;
126 __backtrace (void **array, int size)
128 struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
134 __libc_once_define (static, once);
136 __libc_once (once, init);
138 if (unwind_backtrace == NULL)
139 return __backchain_backtrace (array, size);
142 unwind_backtrace (backtrace_helper, &arg);
144 return arg.cnt != -1 ? arg.cnt : 0;
147 weak_alias (__backtrace, backtrace)
148 libc_hidden_def (__backtrace)