c55a47e723
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.
134 lines
3.6 KiB
C
134 lines
3.6 KiB
C
/* Target-dependent code for NetBSD/amd64.
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Copyright (C) 2003-2017 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 "arch-utils.h"
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#include "frame.h"
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#include "gdbcore.h"
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#include "osabi.h"
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#include "symtab.h"
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#include "amd64-tdep.h"
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#include "nbsd-tdep.h"
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#include "solib-svr4.h"
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/* Support for signal handlers. */
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/* Return whether THIS_FRAME corresponds to a NetBSD sigtramp
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routine. */
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static int
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amd64nbsd_sigtramp_p (struct frame_info *this_frame)
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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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return nbsd_pc_in_sigtramp (pc, name);
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}
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/* Assuming THIS_FRAME corresponds to a NetBSD sigtramp routine,
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return the address of the associated mcontext structure. */
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static CORE_ADDR
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amd64nbsd_mcontext_addr (struct frame_info *this_frame)
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{
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CORE_ADDR addr;
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/* The register %r15 points at `struct ucontext' upon entry of a
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signal trampoline. */
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addr = get_frame_register_unsigned (this_frame, AMD64_R15_REGNUM);
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/* The mcontext structure lives as offset 56 in `struct ucontext'. */
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return addr + 56;
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}
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/* NetBSD 2.0 or later. */
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/* Mapping between the general-purpose registers in `struct reg'
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format and GDB's register cache layout. */
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/* From <machine/reg.h>. */
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int amd64nbsd_r_reg_offset[] =
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{
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14 * 8, /* %rax */
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13 * 8, /* %rbx */
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3 * 8, /* %rcx */
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2 * 8, /* %rdx */
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1 * 8, /* %rsi */
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0 * 8, /* %rdi */
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12 * 8, /* %rbp */
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24 * 8, /* %rsp */
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4 * 8, /* %r8 .. */
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5 * 8,
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6 * 8,
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7 * 8,
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8 * 8,
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9 * 8,
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10 * 8,
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11 * 8, /* ... %r15 */
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21 * 8, /* %rip */
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23 * 8, /* %eflags */
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22 * 8, /* %cs */
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25 * 8, /* %ss */
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18 * 8, /* %ds */
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17 * 8, /* %es */
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16 * 8, /* %fs */
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15 * 8 /* %gs */
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};
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static void
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amd64nbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
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{
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struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
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/* Initialize general-purpose register set details first. */
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tdep->gregset_reg_offset = amd64nbsd_r_reg_offset;
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tdep->gregset_num_regs = ARRAY_SIZE (amd64nbsd_r_reg_offset);
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tdep->sizeof_gregset = 26 * 8;
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amd64_init_abi (info, gdbarch, tdesc_amd64);
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tdep->jb_pc_offset = 7 * 8;
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/* NetBSD has its own convention for signal trampolines. */
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tdep->sigtramp_p = amd64nbsd_sigtramp_p;
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tdep->sigcontext_addr = amd64nbsd_mcontext_addr;
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tdep->sc_reg_offset = amd64nbsd_r_reg_offset;
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tdep->sc_num_regs = ARRAY_SIZE (amd64nbsd_r_reg_offset);
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/* NetBSD uses SVR4-style shared libraries. */
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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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/* Provide a prototype to silence -Wmissing-prototypes. */
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void _initialize_amd64nbsd_tdep (void);
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void
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_initialize_amd64nbsd_tdep (void)
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{
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/* The NetBSD/amd64 native dependent code makes this assumption. */
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gdb_assert (ARRAY_SIZE (amd64nbsd_r_reg_offset) == AMD64_NUM_GREGS);
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gdbarch_register_osabi (bfd_arch_i386, bfd_mach_x86_64,
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GDB_OSABI_NETBSD, amd64nbsd_init_abi);
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}
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