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149 lines
3.9 KiB
C
149 lines
3.9 KiB
C
/* Return backtrace of current program state.
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Copyright (C) 2000-2020 Free Software Foundation, Inc.
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Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <libc-lock.h>
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#include <dlfcn.h>
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#include <execinfo.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <unwind.h>
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/* This is a global variable set at program start time. It marks the
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highest used stack address. */
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extern void *__libc_stack_end;
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/* This is the stack layout we see for every non-leaf function.
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size offset
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%r15 -> +------------------+
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4 | back chain | 0
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4 | end of stack | 4
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8 | glue | 8
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8 | scratch | 16
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40 | save area r6-r15 | 24
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16 | save area f4,f6 | 64
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16 | empty | 80
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+------------------+
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r14 in the save area holds the return address.
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*/
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struct layout
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{
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int back_chain;
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int end_of_stack;
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int glue[2];
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int scratch[2];
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int save_grps[10];
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int save_fp[4];
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int empty[2];
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};
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struct trace_arg
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{
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void **array;
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int cnt, size;
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};
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#ifdef SHARED
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static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
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static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
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static void
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init (void)
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{
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void *handle = __libc_dlopen ("libgcc_s.so.1");
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if (handle == NULL)
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return;
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unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");
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unwind_getip = __libc_dlsym (handle, "_Unwind_GetIP");
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if (unwind_getip == NULL)
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unwind_backtrace = NULL;
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}
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static int
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__backchain_backtrace (void **array, int size)
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{
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/* We assume that all the code is generated with frame pointers set. */
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struct layout *stack;
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int cnt = 0;
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__asm__ ("LR %0,%%r15" : "=d" (stack) );
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/* We skip the call to this function, it makes no sense to record it. */
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stack = (struct layout *) stack->back_chain;
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while (cnt < size)
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{
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if (stack == NULL || (void *) stack > __libc_stack_end)
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/* This means the address is out of range. Note that for the
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toplevel we see a frame pointer with value NULL which clearly is
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out of range. */
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break;
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array[cnt++] = (void *) (stack->save_grps[8] & 0x7fffffff);
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stack = (struct layout *) stack->back_chain;
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}
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return cnt;
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}
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#else
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# define unwind_backtrace _Unwind_Backtrace
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# define unwind_getip _Unwind_GetIP
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#endif
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static _Unwind_Reason_Code
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backtrace_helper (struct _Unwind_Context *ctx, void *a)
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{
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struct trace_arg *arg = a;
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/* We are first called with address in the __backtrace function.
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Skip it. */
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if (arg->cnt != -1)
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arg->array[arg->cnt] = (void *) unwind_getip (ctx);
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if (++arg->cnt == arg->size)
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return _URC_END_OF_STACK;
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return _URC_NO_REASON;
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}
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int
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__backtrace (void **array, int size)
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{
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struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
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if (size <= 0)
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return 0;
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#ifdef SHARED
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__libc_once_define (static, once);
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__libc_once (once, init);
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if (unwind_backtrace == NULL)
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return __backchain_backtrace (array, size);
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#endif
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unwind_backtrace (backtrace_helper, &arg);
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return arg.cnt != -1 ? arg.cnt : 0;
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}
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weak_alias (__backtrace, backtrace)
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libc_hidden_def (__backtrace)
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