2009-02-17 18:56:50 +01:00
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/* Target-dependent code for DICOS running on x86-64's, for GDB.
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2017-01-01 07:50:51 +01:00
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Copyright (C) 2009-2017 Free Software Foundation, Inc.
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2009-02-17 18:56:50 +01:00
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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 "osabi.h"
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#include "amd64-tdep.h"
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#include "dicos-tdep.h"
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static void
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amd64_dicos_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
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{
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Fix x86-64 GNU/Linux crashes
Ref: https://sourceware.org/ml/gdb-patches/2017-07/msg00162.html
Debugging x86-64 GNU/Linux programs currently crashes GDB in
tdesc_use_registers during gdbarch initialization:
Program received signal SIGSEGV, Segmentation fault.
0x0000000001093eaf in htab_remove_elt_with_hash (htab=0x2ef9fa0, element=0x26af960, hash=557151073) at src/libiberty/hashtab.c:728
728 if (*slot == HTAB_EMPTY_ENTRY)
(top-gdb) p slot
$1 = (void **) 0x0
(top-gdb) bt
#0 0x0000000001093eaf in htab_remove_elt_with_hash (htab=0x2ef9fa0, element=0x26af960, hash=557151073) at src/libiberty/hashtab.c:728
#1 0x0000000001093e79 in htab_remove_elt (htab=0x2ef9fa0, element=0x26af960) at src/libiberty/hashtab.c:714
#2 0x00000000009121b0 in tdesc_use_registers (gdbarch=0x3001240, target_desc=0x2659cb0, early_data=0x2881cb0)
at src/gdb/target-descriptions.c:1328
#3 0x000000000047c93e in i386_gdbarch_init (info=..., arches=0x0) at src/gdb/i386-tdep.c:8634
#4 0x0000000000818d5f in gdbarch_find_by_info (info=...) at src/gdb/gdbarch.c:5394
#5 0x00000000007198a8 in set_gdbarch_from_file (abfd=0x2f48250) at src/gdb/arch-utils.c:618
#6 0x00000000007f21cb in exec_file_attach (filename=0x7fffffffddb0 "/home/pedro/gdb/tests/threads", from_tty=1) at src/gdb/exec.c:380
#7 0x0000000000865c18 in catch_command_errors_const (command=0x7f1d83 <exec_file_attach(char const*, int)>, arg=0x7fffffffddb0 "/home/pedro/gdb/tests/threads",
from_tty=1) at src/gdb/main.c:403
#8 0x00000000008669cf in captured_main_1 (context=0x7fffffffd860) at src/gdb/main.c:1035
#9 0x0000000000866de2 in captured_main (data=0x7fffffffd860) at src/gdb/main.c:1142
#10 0x0000000000866e24 in gdb_main (args=0x7fffffffd860) at src/gdb/main.c:1160
#11 0x000000000041312d in main (argc=3, argv=0x7fffffffd968) at src/gdb/gdb.c:32
The direct cause of the crash is that we tried to remove an element
from the hash which supposedly exists, but does not. (htab_remove_elt
shouldn't really crash in this case, but that's secondary.)
The real problem is that early_data passed to tdesc_use_registers
includes regs from a target description that is not the target_desc,
which violates its assumptions. The registers in question are the
fs_base/gs_base registers, added by amd64_init_abi:
tdesc_numbered_register (feature, tdesc_data_segments,
AMD64_FSBASE_REGNUM, "fs_base");
tdesc_numbered_register (feature, tdesc_data_segments,
AMD64_GSBASE_REGNUM, "gs_base");
and that happens because amd64_linux_init_abi uses amd64_init_abi as
helper, but they don't coordinate on which fallback tdesc to use.
amd64_init_abi does:
if (! tdesc_has_registers (tdesc))
tdesc = tdesc_amd64;
and then adds the fs_base/gs_base registers of the "tdesc_amd64" tdesc
to the tdesc_arch_data.
After amd64_init_abi returns, amd64_linux_init_abi does:
if (! tdesc_has_registers (tdesc))
tdesc = tdesc_amd64_linux;
tdep->tdesc = tdesc;
and we end up tdesc_amd64_linux installed in tdep->tdesc.
The fix is to make sure that amd64_linux_init_abi and amd64_init_abi
agree on default tdesc, by adding a "default tdesc" parameter to
amd64_init_abi, instead of having amd64_init_abi hardcode a default.
With this, amd64_init_abi creates the fs_base/gs_base registers using
the tdesc_amd64_linux tdesc.
Tested on x86-64 GNU/Linux, -m64. I don't have an x32 setup handy.
Thanks to John Baldwin, Yao Qi and Simon Marchi for the investigation.
gdb/ChangeLog:
2017-07-13 Pedro Alves <palves@redhat.com>
* amd64-darwin-tdep.c (x86_darwin_init_abi_64): Pass tdesc_amd64
as default tdesc.
* amd64-dicos-tdep.c (amd64_dicos_init_abi):
* amd64-fbsd-tdep.c (amd64fbsd_init_abi):
* amd64-linux-tdep.c (amd64_linux_init_abi): Pass
tdesc_amd64_linux as default tdesc. Get final tdesc from the
tdep.
(amd64_x32_linux_init_abi): Pass tdesc_x32_linux as default tdesc.
Get final tdesc from the tdep.
* amd64-nbsd-tdep.c (amd64nbsd_init_abi): Pass tdesc_amd64 as
default tdesc.
* amd64-obsd-tdep.c (amd64obsd_init_abi): Likewise.
* amd64-sol2-tdep.c (amd64_sol2_init_abi): Likewise.
* amd64-tdep.c (amd64_init_abi): Add 'default_tdesc' parameter.
Use it as default tdesc.
(amd64_x32_init_abi): Add 'default_tdesc' parameter, and pass it
down to amd_init_abi. No longer handle fallback tdesc here.
* amd64-tdep.h (tdesc_x32): Declare.
(amd64_init_abi, amd64_x32_init_abi): Add 'default_tdesc'
parameter.
* amd64-windows-tdep.c (amd64_windows_init_abi): Pass tdesc_amd64
as default tdesc.
2017-07-13 21:56:42 +02:00
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amd64_init_abi (info, gdbarch, tdesc_amd64);
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2009-02-17 18:56:50 +01:00
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dicos_init_abi (gdbarch);
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}
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static enum gdb_osabi
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amd64_dicos_osabi_sniffer (bfd *abfd)
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{
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char *target_name = bfd_get_target (abfd);
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/* On amd64-DICOS, the Load Module's "header" section is 72
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bytes. */
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if (strcmp (target_name, "elf64-x86-64") == 0
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&& dicos_load_module_p (abfd, 72))
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return GDB_OSABI_DICOS;
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return GDB_OSABI_UNKNOWN;
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}
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/* Provide a prototype to silence -Wmissing-prototypes. */
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void _initialize_amd64_dicos_tdep (void);
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void
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_initialize_amd64_dicos_tdep (void)
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{
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gdbarch_register_osabi_sniffer (bfd_arch_i386, bfd_target_elf_flavour,
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amd64_dicos_osabi_sniffer);
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gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64,
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GDB_OSABI_DICOS,
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amd64_dicos_init_abi);
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}
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