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08106042d9
I built GDB for all targets on a x86-64/GNU-Linux system, and
then (accidentally) passed GDB a RISC-V binary, and asked GDB to "run"
the binary on the native target. I got this error:
(gdb) show architecture
The target architecture is set to "auto" (currently "i386").
(gdb) file /tmp/hello.rv32.exe
Reading symbols from /tmp/hello.rv32.exe...
(gdb) show architecture
The target architecture is set to "auto" (currently "riscv:rv32").
(gdb) run
Starting program: /tmp/hello.rv32.exe
../../src/gdb/i387-tdep.c:596: internal-error: i387_supply_fxsave: Assertion `tdep->st0_regnum >= I386_ST0_REGNUM' failed.
What's going on here is this; initially the architecture is i386, this
is based on the default architecture, which is set based on the native
target. After loading the RISC-V executable the architecture of the
current inferior is updated based on the architecture of the
executable.
When we "run", GDB does a fork & exec, with the inferior being
controlled through ptrace. GDB sees an initial stop from the inferior
as soon as the inferior comes to life. In response to this stop GDB
ends up calling save_stop_reason (linux-nat.c), which ends up trying
to read register from the inferior, to do this we end up calling
target_ops::fetch_registers, which, for the x86-64 native target,
calls amd64_linux_nat_target::fetch_registers.
After this I eventually end up in i387_supply_fxsave, different x86
based targets will end in different functions to fetch registers, but
it doesn't really matter which function we end up in, the problem is
this line, which is repeated in many places:
i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);
The problem here is that the ARCH in this line comes from the current
inferior, which, as we discussed above, will be a RISC-V gdbarch, the
tdep field will actually be of type riscv_gdbarch_tdep, not
i386_gdbarch_tdep. After this cast we are relying on undefined
behaviour, in my case I happen to trigger an assert, but this might
not always be the case.
The thing I tried that exposed this problem was of course, trying to
start an executable of the wrong architecture on a native target. I
don't think that the correct solution for this problem is to detect,
at the point of cast, that the gdbarch_tdep object is of the wrong
type, but, I did wonder, is there a way that we could protect
ourselves from incorrectly casting the gdbarch_tdep object?
I think that there is something we can do here, and this commit is the
first step in that direction, though no actual check is added by this
commit.
This commit can be split into two parts:
(1) In gdbarch.h and arch-utils.c. In these files I have modified
gdbarch_tdep (the function) so that it now takes a template argument,
like this:
template<typename TDepType>
static inline TDepType *
gdbarch_tdep (struct gdbarch *gdbarch)
{
struct gdbarch_tdep *tdep = gdbarch_tdep_1 (gdbarch);
return static_cast<TDepType *> (tdep);
}
After this change we are no better protected, but the cast is now
done within the gdbarch_tdep function rather than at the call sites,
this leads to the second, much larger change in this commit,
(2) Everywhere gdbarch_tdep is called, we make changes like this:
- i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);
+ i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (arch);
There should be no functional change after this commit.
In the next commit I will build on this change to add an assertion in
gdbarch_tdep that checks we are casting to the correct type.
253 lines
7.3 KiB
C
253 lines
7.3 KiB
C
/* Target-dependent code for FreeBSD/sparc64.
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Copyright (C) 2003-2022 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "defs.h"
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#include "frame.h"
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#include "frame-unwind.h"
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#include "gdbcore.h"
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#include "osabi.h"
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#include "regcache.h"
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#include "regset.h"
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#include "target.h"
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#include "trad-frame.h"
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#include "sparc64-tdep.h"
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#include "fbsd-tdep.h"
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#include "solib-svr4.h"
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#include "gdbarch.h"
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/* From <machine/reg.h>. */
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const struct sparc_gregmap sparc64fbsd_gregmap =
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{
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26 * 8, /* "tstate" */
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25 * 8, /* %pc */
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24 * 8, /* %npc */
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28 * 8, /* %y */
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16 * 8, /* %fprs */
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-1,
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1 * 8, /* %g1 */
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-1, /* %l0 */
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8 /* sizeof (%y) */
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};
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static void
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sparc64fbsd_supply_gregset (const struct regset *regset,
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struct regcache *regcache,
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int regnum, const void *gregs, size_t len)
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{
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sparc64_supply_gregset (&sparc64fbsd_gregmap, regcache, regnum, gregs);
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}
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static void
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sparc64fbsd_collect_gregset (const struct regset *regset,
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const struct regcache *regcache,
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int regnum, void *gregs, size_t len)
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{
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sparc64_collect_gregset (&sparc64fbsd_gregmap, regcache, regnum, gregs);
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}
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static void
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sparc64fbsd_supply_fpregset (const struct regset *regset,
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struct regcache *regcache,
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int regnum, const void *fpregs, size_t len)
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{
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sparc64_supply_fpregset (&sparc64_bsd_fpregmap, regcache, regnum, fpregs);
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}
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static void
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sparc64fbsd_collect_fpregset (const struct regset *regset,
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const struct regcache *regcache,
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int regnum, void *fpregs, size_t len)
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{
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sparc64_collect_fpregset (&sparc64_bsd_fpregmap, regcache, regnum, fpregs);
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}
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/* Signal trampolines. */
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static int
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sparc64fbsd_pc_in_sigtramp (CORE_ADDR pc, const char *name)
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{
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return (name && strcmp (name, "__sigtramp") == 0);
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}
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static struct sparc_frame_cache *
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sparc64fbsd_sigtramp_frame_cache (struct frame_info *this_frame,
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void **this_cache)
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{
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struct sparc_frame_cache *cache;
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CORE_ADDR addr, mcontext_addr, sp;
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LONGEST fprs;
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int regnum;
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if (*this_cache)
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return (struct sparc_frame_cache *) *this_cache;
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cache = sparc_frame_cache (this_frame, this_cache);
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gdb_assert (cache == *this_cache);
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cache->saved_regs = trad_frame_alloc_saved_regs (this_frame);
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/* The third argument is a pointer to an instance of `ucontext_t',
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which has a member `uc_mcontext' that contains the saved
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registers. */
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addr = get_frame_register_unsigned (this_frame, SPARC_O2_REGNUM);
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mcontext_addr = addr + 64;
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/* The following registers travel in the `mc_local' slots of
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`mcontext_t'. */
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addr = mcontext_addr + 16 * 8;
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cache->saved_regs[SPARC64_FPRS_REGNUM].set_addr (addr + 0 * 8);
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cache->saved_regs[SPARC64_FSR_REGNUM].set_addr (addr + 1 * 8);
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/* The following registers travel in the `mc_in' slots of
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`mcontext_t'. */
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addr = mcontext_addr + 24 * 8;
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cache->saved_regs[SPARC64_NPC_REGNUM].set_addr (addr + 0 * 8);
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cache->saved_regs[SPARC64_PC_REGNUM].set_addr (addr + 1 * 8);
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cache->saved_regs[SPARC64_STATE_REGNUM].set_addr (addr + 2 * 8);
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cache->saved_regs[SPARC64_Y_REGNUM].set_addr (addr + 4 * 8);
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/* The `global' and `out' registers travel in the `mc_global' and
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`mc_out' slots of `mcontext_t', except for %g0. Since %g0 is
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always zero, keep the identity encoding. */
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for (regnum = SPARC_G1_REGNUM, addr = mcontext_addr + 8;
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regnum <= SPARC_O7_REGNUM; regnum++, addr += 8)
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cache->saved_regs[regnum].set_addr (addr);
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/* The `local' and `in' registers have been saved in the register
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save area. */
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addr = cache->saved_regs[SPARC_SP_REGNUM].addr ();
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sp = get_frame_memory_unsigned (this_frame, addr, 8);
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for (regnum = SPARC_L0_REGNUM, addr = sp + BIAS;
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regnum <= SPARC_I7_REGNUM; regnum++, addr += 8)
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cache->saved_regs[regnum].set_addr (addr);
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/* The floating-point registers are only saved if the FEF bit in
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%fprs has been set. */
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#define FPRS_FEF (1 << 2)
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addr = cache->saved_regs[SPARC64_FPRS_REGNUM].addr ();
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fprs = get_frame_memory_unsigned (this_frame, addr, 8);
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if (fprs & FPRS_FEF)
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{
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for (regnum = SPARC_F0_REGNUM, addr = mcontext_addr + 32 * 8;
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regnum <= SPARC_F31_REGNUM; regnum++, addr += 4)
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cache->saved_regs[regnum].set_addr (addr);
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for (regnum = SPARC64_F32_REGNUM;
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regnum <= SPARC64_F62_REGNUM; regnum++, addr += 8)
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cache->saved_regs[regnum].set_addr (addr);
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}
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return cache;
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}
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static void
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sparc64fbsd_sigtramp_frame_this_id (struct frame_info *this_frame,
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void **this_cache,
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struct frame_id *this_id)
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{
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struct sparc_frame_cache *cache =
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sparc64fbsd_sigtramp_frame_cache (this_frame, this_cache);
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(*this_id) = frame_id_build (cache->base, cache->pc);
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}
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static struct value *
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sparc64fbsd_sigtramp_frame_prev_register (struct frame_info *this_frame,
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void **this_cache, int regnum)
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{
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struct sparc_frame_cache *cache =
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sparc64fbsd_sigtramp_frame_cache (this_frame, this_cache);
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return trad_frame_get_prev_register (this_frame, cache->saved_regs, regnum);
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}
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static int
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sparc64fbsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
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struct frame_info *this_frame,
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void **this_cache)
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{
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CORE_ADDR pc = get_frame_pc (this_frame);
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const char *name;
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find_pc_partial_function (pc, &name, NULL, NULL);
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if (sparc64fbsd_pc_in_sigtramp (pc, name))
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return 1;
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return 0;
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}
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static const struct frame_unwind sparc64fbsd_sigtramp_frame_unwind =
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{
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"sparc64 freebsd sigtramp",
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SIGTRAMP_FRAME,
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default_frame_unwind_stop_reason,
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sparc64fbsd_sigtramp_frame_this_id,
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sparc64fbsd_sigtramp_frame_prev_register,
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NULL,
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sparc64fbsd_sigtramp_frame_sniffer
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};
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static const struct regset sparc64fbsd_gregset =
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{
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NULL, sparc64fbsd_supply_gregset, sparc64fbsd_collect_gregset
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};
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static const struct regset sparc64fbsd_fpregset =
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{
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NULL, sparc64fbsd_supply_fpregset, sparc64fbsd_collect_fpregset
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};
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static void
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sparc64fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
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{
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sparc_gdbarch_tdep *tdep = gdbarch_tdep<sparc_gdbarch_tdep> (gdbarch);
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/* Generic FreeBSD support. */
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fbsd_init_abi (info, gdbarch);
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tdep->gregset = &sparc64fbsd_gregset;
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tdep->sizeof_gregset = 256;
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tdep->fpregset = &sparc64fbsd_fpregset;
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tdep->sizeof_fpregset = 272;
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frame_unwind_append_unwinder (gdbarch, &sparc64fbsd_sigtramp_frame_unwind);
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sparc64_init_abi (info, gdbarch);
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/* FreeBSD/sparc64 has SVR4-style shared libraries. */
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set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
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set_solib_svr4_fetch_link_map_offsets
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(gdbarch, svr4_lp64_fetch_link_map_offsets);
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}
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void _initialize_sparc64fbsd_tdep ();
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void
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_initialize_sparc64fbsd_tdep ()
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{
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gdbarch_register_osabi (bfd_arch_sparc, bfd_mach_sparc_v9,
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GDB_OSABI_FREEBSD, sparc64fbsd_init_abi);
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}
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