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/* Target-dependent code for GNU/Linux on Alpha.
Copyright 2002 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include "defs.h"
#include "gdbcore.h"
#include "value.h"
#include "alpha-tdep.h"
/* Under GNU/Linux, signal handler invocations can be identified by the
designated code sequence that is used to return from a signal
handler. In particular, the return address of a signal handler
points to the following sequence (the first instruction is quadword
aligned):
bis $30,$30,$16
addq $31,0x67,$0
call_pal callsys
Each instruction has a unique encoding, so we simply attempt to
match the instruction the pc is pointing to with any of the above
instructions. If there is a hit, we know the offset to the start
of the designated sequence and can then check whether we really are
executing in a designated sequence. If not, -1 is returned,
otherwise the offset from the start of the desingated sequence is
returned.
There is a slight chance of false hits: code could jump into the
middle of the designated sequence, in which case there is no
guarantee that we are in the middle of a sigreturn syscall. Don't
think this will be a problem in praxis, though. */
LONGEST
alpha_linux_sigtramp_offset (CORE_ADDR pc)
{
unsigned int i[3], w;
long off;
if (read_memory_nobpt (pc, (char *) &w, 4) != 0)
return -1;
off = -1;
switch (w)
{
case 0x47de0410:
off = 0;
break; /* bis $30,$30,$16 */
case 0x43ecf400:
off = 4;
break; /* addq $31,0x67,$0 */
case 0x00000083:
off = 8;
break; /* call_pal callsys */
default:
return -1;
}
pc -= off;
if (pc & 0x7)
{
/* designated sequence is not quadword aligned */
return -1;
}
if (read_memory_nobpt (pc, (char *) i, sizeof (i)) != 0)
return -1;
if (i[0] == 0x47de0410 && i[1] == 0x43ecf400 && i[2] == 0x00000083)
return off;
return -1;
}
static void
alpha_linux_init_abi (struct gdbarch_info info,
struct gdbarch *gdbarch)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset;
}
void
_initialize_alpha_linux_tdep (void)
{
alpha_gdbarch_register_os_abi (ALPHA_ABI_LINUX, alpha_linux_init_abi);
}
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