456 lines
13 KiB
C
456 lines
13 KiB
C
/* Target-dependent code for OpenBSD/i386.
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Copyright (C) 1988-2017 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 "frame-unwind.h"
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#include "gdbcore.h"
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#include "regcache.h"
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#include "regset.h"
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#include "symtab.h"
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#include "objfiles.h"
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#include "osabi.h"
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#include "target.h"
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#include "trad-frame.h"
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#include "obsd-tdep.h"
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#include "i386-tdep.h"
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#include "i387-tdep.h"
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#include "solib-svr4.h"
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#include "bsd-uthread.h"
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/* Support for signal handlers. */
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/* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
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in virtual memory. The randomness makes it somewhat tricky to
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detect it, but fortunately we can rely on the fact that the start
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of the sigtramp routine is page-aligned. We recognize the
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trampoline by looking for the code that invokes the sigreturn
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system call. The offset where we can find that code varies from
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release to release.
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By the way, the mapping mentioned above is read-only, so you cannot
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place a breakpoint in the signal trampoline. */
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/* Default page size. */
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static const int i386obsd_page_size = 4096;
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/* Offset for sigreturn(2). */
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static const int i386obsd_sigreturn_offset[] = {
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0x0a, /* OpenBSD 3.2 */
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0x14, /* OpenBSD 3.6 */
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0x3a, /* OpenBSD 3.8 */
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-1
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};
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/* Return whether THIS_FRAME corresponds to an OpenBSD sigtramp
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routine. */
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static int
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i386obsd_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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CORE_ADDR start_pc = (pc & ~(i386obsd_page_size - 1));
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/* The call sequence invoking sigreturn(2). */
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const gdb_byte sigreturn[] =
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{
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0xb8,
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0x67, 0x00, 0x00, 0x00, /* movl $SYS_sigreturn, %eax */
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0xcd, 0x80 /* int $0x80 */
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};
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size_t buflen = sizeof sigreturn;
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const int *offset;
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gdb_byte *buf;
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const char *name;
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/* If the function has a valid symbol name, it isn't a
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trampoline. */
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find_pc_partial_function (pc, &name, NULL, NULL);
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if (name != NULL)
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return 0;
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/* If the function lives in a valid section (even without a starting
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point) it isn't a trampoline. */
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if (find_pc_section (pc) != NULL)
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return 0;
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/* Allocate buffer. */
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buf = (gdb_byte *) alloca (buflen);
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/* Loop over all offsets. */
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for (offset = i386obsd_sigreturn_offset; *offset != -1; offset++)
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{
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/* If we can't read the instructions, return zero. */
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if (!safe_frame_unwind_memory (this_frame, start_pc + *offset,
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buf, buflen))
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return 0;
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/* Check for sigreturn(2). */
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if (memcmp (buf, sigreturn, buflen) == 0)
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return 1;
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}
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return 0;
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}
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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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static int i386obsd_r_reg_offset[] =
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{
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0 * 4, /* %eax */
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1 * 4, /* %ecx */
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2 * 4, /* %edx */
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3 * 4, /* %ebx */
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4 * 4, /* %esp */
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5 * 4, /* %ebp */
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6 * 4, /* %esi */
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7 * 4, /* %edi */
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8 * 4, /* %eip */
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9 * 4, /* %eflags */
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10 * 4, /* %cs */
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11 * 4, /* %ss */
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12 * 4, /* %ds */
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13 * 4, /* %es */
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14 * 4, /* %fs */
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15 * 4 /* %gs */
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};
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/* Sigtramp routine location for OpenBSD 3.1 and earlier releases. */
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CORE_ADDR i386obsd_sigtramp_start_addr = 0xbfbfdf20;
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CORE_ADDR i386obsd_sigtramp_end_addr = 0xbfbfdff0;
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/* From <machine/signal.h>. */
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int i386obsd_sc_reg_offset[I386_NUM_GREGS] =
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{
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10 * 4, /* %eax */
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9 * 4, /* %ecx */
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8 * 4, /* %edx */
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7 * 4, /* %ebx */
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14 * 4, /* %esp */
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6 * 4, /* %ebp */
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5 * 4, /* %esi */
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4 * 4, /* %edi */
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11 * 4, /* %eip */
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13 * 4, /* %eflags */
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12 * 4, /* %cs */
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15 * 4, /* %ss */
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3 * 4, /* %ds */
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2 * 4, /* %es */
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1 * 4, /* %fs */
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0 * 4 /* %gs */
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};
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/* From /usr/src/lib/libpthread/arch/i386/uthread_machdep.c. */
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static int i386obsd_uthread_reg_offset[] =
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{
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11 * 4, /* %eax */
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10 * 4, /* %ecx */
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9 * 4, /* %edx */
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8 * 4, /* %ebx */
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-1, /* %esp */
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6 * 4, /* %ebp */
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5 * 4, /* %esi */
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4 * 4, /* %edi */
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12 * 4, /* %eip */
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-1, /* %eflags */
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13 * 4, /* %cs */
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-1, /* %ss */
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3 * 4, /* %ds */
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2 * 4, /* %es */
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1 * 4, /* %fs */
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0 * 4 /* %gs */
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};
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/* Offset within the thread structure where we can find the saved
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stack pointer (%esp). */
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#define I386OBSD_UTHREAD_ESP_OFFSET 176
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static void
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i386obsd_supply_uthread (struct regcache *regcache,
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int regnum, CORE_ADDR addr)
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{
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struct gdbarch *gdbarch = get_regcache_arch (regcache);
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enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
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CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
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CORE_ADDR sp = 0;
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gdb_byte buf[4];
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int i;
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gdb_assert (regnum >= -1);
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if (regnum == -1 || regnum == I386_ESP_REGNUM)
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{
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int offset;
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/* Fetch stack pointer from thread structure. */
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sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
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/* Adjust the stack pointer such that it looks as if we just
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returned from _thread_machdep_switch. */
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offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;
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store_unsigned_integer (buf, 4, byte_order, sp + offset);
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regcache_raw_supply (regcache, I386_ESP_REGNUM, buf);
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}
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for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
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{
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if (i386obsd_uthread_reg_offset[i] != -1
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&& (regnum == -1 || regnum == i))
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{
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/* Fetch stack pointer from thread structure (if we didn't
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do so already). */
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if (sp == 0)
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sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
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/* Read the saved register from the stack frame. */
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read_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
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regcache_raw_supply (regcache, i, buf);
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}
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}
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}
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static void
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i386obsd_collect_uthread (const struct regcache *regcache,
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int regnum, CORE_ADDR addr)
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{
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struct gdbarch *gdbarch = get_regcache_arch (regcache);
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enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
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CORE_ADDR sp_addr = addr + I386OBSD_UTHREAD_ESP_OFFSET;
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CORE_ADDR sp = 0;
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gdb_byte buf[4];
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int i;
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gdb_assert (regnum >= -1);
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if (regnum == -1 || regnum == I386_ESP_REGNUM)
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{
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int offset;
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/* Calculate the stack pointer (frame pointer) that will be
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stored into the thread structure. */
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offset = i386obsd_uthread_reg_offset[I386_EIP_REGNUM] + 4;
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regcache_raw_collect (regcache, I386_ESP_REGNUM, buf);
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sp = extract_unsigned_integer (buf, 4, byte_order) - offset;
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/* Store the stack pointer. */
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write_memory_unsigned_integer (sp_addr, 4, byte_order, sp);
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/* The stack pointer was (potentially) modified. Make sure we
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build a proper stack frame. */
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regnum = -1;
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}
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for (i = 0; i < ARRAY_SIZE (i386obsd_uthread_reg_offset); i++)
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{
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if (i386obsd_uthread_reg_offset[i] != -1
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&& (regnum == -1 || regnum == i))
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{
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/* Fetch stack pointer from thread structure (if we didn't
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calculate it already). */
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if (sp == 0)
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sp = read_memory_unsigned_integer (sp_addr, 4, byte_order);
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/* Write the register into the stack frame. */
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regcache_raw_collect (regcache, i, buf);
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write_memory (sp + i386obsd_uthread_reg_offset[i], buf, 4);
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}
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}
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}
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/* Kernel debugging support. */
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/* From <machine/frame.h>. Note that %esp and %ess are only saved in
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a trap frame when entering the kernel from user space. */
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static int i386obsd_tf_reg_offset[] =
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{
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10 * 4, /* %eax */
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9 * 4, /* %ecx */
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8 * 4, /* %edx */
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7 * 4, /* %ebx */
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-1, /* %esp */
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6 * 4, /* %ebp */
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5 * 4, /* %esi */
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4 * 4, /* %edi */
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13 * 4, /* %eip */
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15 * 4, /* %eflags */
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14 * 4, /* %cs */
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-1, /* %ss */
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3 * 4, /* %ds */
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2 * 4, /* %es */
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0 * 4, /* %fs */
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1 * 4 /* %gs */
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};
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static struct trad_frame_cache *
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i386obsd_trapframe_cache (struct frame_info *this_frame, void **this_cache)
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{
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struct gdbarch *gdbarch = get_frame_arch (this_frame);
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enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
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struct trad_frame_cache *cache;
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CORE_ADDR func, sp, addr;
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ULONGEST cs;
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const char *name;
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int i;
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if (*this_cache)
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return (struct trad_frame_cache *) *this_cache;
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cache = trad_frame_cache_zalloc (this_frame);
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*this_cache = cache;
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func = get_frame_func (this_frame);
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sp = get_frame_register_unsigned (this_frame, I386_ESP_REGNUM);
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find_pc_partial_function (func, &name, NULL, NULL);
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if (name && startswith (name, "Xintr"))
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addr = sp + 8; /* It's an interrupt frame. */
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else
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addr = sp;
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for (i = 0; i < ARRAY_SIZE (i386obsd_tf_reg_offset); i++)
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if (i386obsd_tf_reg_offset[i] != -1)
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trad_frame_set_reg_addr (cache, i, addr + i386obsd_tf_reg_offset[i]);
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/* Read %cs from trap frame. */
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addr += i386obsd_tf_reg_offset[I386_CS_REGNUM];
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cs = read_memory_unsigned_integer (addr, 4, byte_order);
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if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
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{
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/* Trap from user space; terminate backtrace. */
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trad_frame_set_id (cache, outer_frame_id);
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}
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else
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{
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/* Construct the frame ID using the function start. */
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trad_frame_set_id (cache, frame_id_build (sp + 8, func));
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}
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return cache;
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}
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static void
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i386obsd_trapframe_this_id (struct frame_info *this_frame,
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void **this_cache, struct frame_id *this_id)
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{
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struct trad_frame_cache *cache =
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i386obsd_trapframe_cache (this_frame, this_cache);
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trad_frame_get_id (cache, this_id);
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}
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static struct value *
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i386obsd_trapframe_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 trad_frame_cache *cache =
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i386obsd_trapframe_cache (this_frame, this_cache);
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return trad_frame_get_register (cache, this_frame, regnum);
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}
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static int
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i386obsd_trapframe_sniffer (const struct frame_unwind *self,
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struct frame_info *this_frame,
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void **this_prologue_cache)
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{
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ULONGEST cs;
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const char *name;
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/* Check Current Privilege Level and bail out if we're not executing
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in kernel space. */
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cs = get_frame_register_unsigned (this_frame, I386_CS_REGNUM);
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if ((cs & I386_SEL_RPL) == I386_SEL_UPL)
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return 0;
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find_pc_partial_function (get_frame_pc (this_frame), &name, NULL, NULL);
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return (name && (strcmp (name, "calltrap") == 0
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|| strcmp (name, "syscall1") == 0
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|| startswith (name, "Xintr")
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|| startswith (name, "Xsoft")));
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}
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static const struct frame_unwind i386obsd_trapframe_unwind = {
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/* FIXME: kettenis/20051219: This really is more like an interrupt
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frame, but SIGTRAMP_FRAME would print <signal handler called>,
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which really is not what we want here. */
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NORMAL_FRAME,
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default_frame_unwind_stop_reason,
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i386obsd_trapframe_this_id,
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i386obsd_trapframe_prev_register,
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NULL,
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i386obsd_trapframe_sniffer
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};
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static void
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i386obsd_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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/* Obviously OpenBSD is BSD-based. */
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i386bsd_init_abi (info, gdbarch);
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obsd_init_abi (info, gdbarch);
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i386_elf_init_abi (info, gdbarch);
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/* OpenBSD has a different `struct reg'. */
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tdep->gregset_reg_offset = i386obsd_r_reg_offset;
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tdep->gregset_num_regs = ARRAY_SIZE (i386obsd_r_reg_offset);
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tdep->sizeof_gregset = 16 * 4;
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/* OpenBSD uses -freg-struct-return by default. */
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tdep->struct_return = reg_struct_return;
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/* OpenBSD uses a different memory layout. */
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tdep->sigtramp_start = i386obsd_sigtramp_start_addr;
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tdep->sigtramp_end = i386obsd_sigtramp_end_addr;
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tdep->sigtramp_p = i386obsd_sigtramp_p;
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/* OpenBSD has a `struct sigcontext' that's different from the
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original 4.3 BSD. */
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tdep->sc_reg_offset = i386obsd_sc_reg_offset;
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tdep->sc_num_regs = ARRAY_SIZE (i386obsd_sc_reg_offset);
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/* OpenBSD provides a user-level threads implementation. */
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bsd_uthread_set_supply_uthread (gdbarch, i386obsd_supply_uthread);
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bsd_uthread_set_collect_uthread (gdbarch, i386obsd_collect_uthread);
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/* Unwind kernel trap frames correctly. */
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frame_unwind_prepend_unwinder (gdbarch, &i386obsd_trapframe_unwind);
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/* OpenBSD ELF uses SVR4-style shared libraries. */
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set_solib_svr4_fetch_link_map_offsets
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(gdbarch, svr4_ilp32_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_i386obsd_tdep (void);
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void
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_initialize_i386obsd_tdep (void)
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{
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gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_OPENBSD,
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i386obsd_init_abi);
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}
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