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1 /* Return backtrace of current program state.
2 Copyright (C) 1998-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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.
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.
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 <https://www.gnu.org/licenses/>. */
23 #include <libc-vdso.h>
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
29 +----------------+ +-----------------+
30 %r1 -> | %r1 last frame--------> | %r1 last frame--->... --> NULL
32 | (unused) | | return address |
33 +----------------+ +-----------------+
41 #define SIGNAL_FRAMESIZE 64
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
;
51 /* We don't care about the rest, since IP value is at 'mctx' field. */
55 is_sigtramp_address (void *nip
)
57 #ifdef HAVE_SIGTRAMP_RT32
58 if (nip
== GLRO (dl_vdso_sigtramp_32
))
64 struct rt_signal_frame_32
{
65 char dummy
[SIGNAL_FRAMESIZE
+ 16];
68 /* We don't care about the rest, since IP value is at 'uc' field. */
72 is_sigtramp_address_rt (void * nip
)
74 #ifdef HAVE_SIGTRAMP_32
75 if (nip
== GLRO (dl_vdso_sigtramp_rt32
))
82 __backtrace (void **array
, int size
)
84 struct layout
*current
;
87 /* Force gcc to spill LR. */
88 asm volatile ("" : "=l"(current
));
90 /* Get the address on top-of-stack. */
91 asm volatile ("lwz %0,0(1)" : "=r"(current
));
94 current
!= NULL
&& count
< size
;
95 current
= current
->next
, count
++)
97 gregset_t
*gregset
= NULL
;
99 array
[count
] = current
->return_address
;
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
))
105 struct signal_frame_32
*sigframe
=
106 (struct signal_frame_32
*) current
;
107 gregset
= &sigframe
->mctx
.gregs
;
109 else if (is_sigtramp_address_rt (current
->return_address
))
111 struct rt_signal_frame_32
*sigframe
=
112 (struct rt_signal_frame_32
*) current
;
113 gregset
= &sigframe
->uc
.uc_mcontext
.uc_regs
->gregs
;
117 array
[++count
] = (void*)((*gregset
)[PT_NIP
]);
118 current
= (void*)((*gregset
)[PT_R1
]);
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
)
130 weak_alias (__backtrace
, backtrace
)
131 libc_hidden_def (__backtrace
)
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