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425 lines
14 KiB
C
425 lines
14 KiB
C
/* Target-dependent code for GNU/Linux i386.
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Copyright 2000, 2001, 2002, 2003, 2004 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 2 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, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#include "defs.h"
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#include "gdbcore.h"
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#include "frame.h"
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#include "value.h"
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#include "regcache.h"
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#include "inferior.h"
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#include "osabi.h"
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#include "reggroups.h"
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#include "gdb_string.h"
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#include "i386-tdep.h"
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#include "i386-linux-tdep.h"
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#include "glibc-tdep.h"
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#include "solib-svr4.h"
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/* Return the name of register REG. */
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static const char *
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i386_linux_register_name (int reg)
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{
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/* Deal with the extra "orig_eax" pseudo register. */
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if (reg == I386_LINUX_ORIG_EAX_REGNUM)
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return "orig_eax";
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return i386_register_name (reg);
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}
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/* Return non-zero, when the register is in the corresponding register
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group. Put the LINUX_ORIG_EAX register in the system group. */
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static int
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i386_linux_register_reggroup_p (struct gdbarch *gdbarch, int regnum,
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struct reggroup *group)
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{
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if (regnum == I386_LINUX_ORIG_EAX_REGNUM)
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return (group == system_reggroup
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|| group == save_reggroup
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|| group == restore_reggroup);
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return i386_register_reggroup_p (gdbarch, regnum, group);
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}
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/* Recognizing signal handler frames. */
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/* GNU/Linux has two flavors of signals. Normal signal handlers, and
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"realtime" (RT) signals. The RT signals can provide additional
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information to the signal handler if the SA_SIGINFO flag is set
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when establishing a signal handler using `sigaction'. It is not
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unlikely that future versions of GNU/Linux will support SA_SIGINFO
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for normal signals too. */
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/* When the i386 Linux kernel calls a signal handler and the
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SA_RESTORER flag isn't set, the return address points to a bit of
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code on the stack. This function returns whether the PC appears to
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be within this bit of code.
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The instruction sequence for normal signals is
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pop %eax
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mov $0x77, %eax
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int $0x80
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or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80.
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Checking for the code sequence should be somewhat reliable, because
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the effect is to call the system call sigreturn. This is unlikely
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to occur anywhere other than in a signal trampoline.
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It kind of sucks that we have to read memory from the process in
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order to identify a signal trampoline, but there doesn't seem to be
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any other way. Therefore we only do the memory reads if no
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function name could be identified, which should be the case since
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the code is on the stack.
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Detection of signal trampolines for handlers that set the
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SA_RESTORER flag is in general not possible. Unfortunately this is
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what the GNU C Library has been doing for quite some time now.
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However, as of version 2.1.2, the GNU C Library uses signal
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trampolines (named __restore and __restore_rt) that are identical
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to the ones used by the kernel. Therefore, these trampolines are
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supported too. */
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#define LINUX_SIGTRAMP_INSN0 0x58 /* pop %eax */
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#define LINUX_SIGTRAMP_OFFSET0 0
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#define LINUX_SIGTRAMP_INSN1 0xb8 /* mov $NNNN, %eax */
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#define LINUX_SIGTRAMP_OFFSET1 1
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#define LINUX_SIGTRAMP_INSN2 0xcd /* int */
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#define LINUX_SIGTRAMP_OFFSET2 6
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static const unsigned char linux_sigtramp_code[] =
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{
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LINUX_SIGTRAMP_INSN0, /* pop %eax */
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LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77, %eax */
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LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */
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};
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#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code)
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/* If PC is in a sigtramp routine, return the address of the start of
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the routine. Otherwise, return 0. */
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static CORE_ADDR
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i386_linux_sigtramp_start (CORE_ADDR pc)
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{
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unsigned char buf[LINUX_SIGTRAMP_LEN];
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/* We only recognize a signal trampoline if PC is at the start of
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one of the three instructions. We optimize for finding the PC at
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the start, as will be the case when the trampoline is not the
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first frame on the stack. We assume that in the case where the
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PC is not at the start of the instruction sequence, there will be
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a few trailing readable bytes on the stack. */
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if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
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return 0;
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if (buf[0] != LINUX_SIGTRAMP_INSN0)
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{
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int adjust;
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switch (buf[0])
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{
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case LINUX_SIGTRAMP_INSN1:
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adjust = LINUX_SIGTRAMP_OFFSET1;
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break;
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case LINUX_SIGTRAMP_INSN2:
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adjust = LINUX_SIGTRAMP_OFFSET2;
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break;
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default:
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return 0;
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}
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pc -= adjust;
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if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
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return 0;
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}
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if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0)
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return 0;
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return pc;
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}
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/* This function does the same for RT signals. Here the instruction
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sequence is
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mov $0xad, %eax
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int $0x80
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or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80.
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The effect is to call the system call rt_sigreturn. */
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#define LINUX_RT_SIGTRAMP_INSN0 0xb8 /* mov $NNNN, %eax */
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#define LINUX_RT_SIGTRAMP_OFFSET0 0
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#define LINUX_RT_SIGTRAMP_INSN1 0xcd /* int */
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#define LINUX_RT_SIGTRAMP_OFFSET1 5
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static const unsigned char linux_rt_sigtramp_code[] =
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{
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LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad, %eax */
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LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */
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};
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#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code)
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/* If PC is in a RT sigtramp routine, return the address of the start
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of the routine. Otherwise, return 0. */
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static CORE_ADDR
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i386_linux_rt_sigtramp_start (CORE_ADDR pc)
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{
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unsigned char buf[LINUX_RT_SIGTRAMP_LEN];
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/* We only recognize a signal trampoline if PC is at the start of
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one of the two instructions. We optimize for finding the PC at
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the start, as will be the case when the trampoline is not the
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first frame on the stack. We assume that in the case where the
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PC is not at the start of the instruction sequence, there will be
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a few trailing readable bytes on the stack. */
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if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
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return 0;
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if (buf[0] != LINUX_RT_SIGTRAMP_INSN0)
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{
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if (buf[0] != LINUX_RT_SIGTRAMP_INSN1)
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return 0;
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pc -= LINUX_RT_SIGTRAMP_OFFSET1;
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if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
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return 0;
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}
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if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0)
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return 0;
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return pc;
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}
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/* Return whether the frame preceding NEXT_FRAME corresponds to a
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GNU/Linux sigtramp routine. */
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static int
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i386_linux_sigtramp_p (struct frame_info *next_frame)
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{
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CORE_ADDR pc = frame_pc_unwind (next_frame);
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char *name;
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find_pc_partial_function (pc, &name, NULL, NULL);
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/* If we have NAME, we can optimize the search. The trampolines are
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named __restore and __restore_rt. However, they aren't dynamically
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exported from the shared C library, so the trampoline may appear to
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be part of the preceding function. This should always be sigaction,
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__sigaction, or __libc_sigaction (all aliases to the same function). */
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if (name == NULL || strstr (name, "sigaction") != NULL)
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return (i386_linux_sigtramp_start (pc) != 0
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|| i386_linux_rt_sigtramp_start (pc) != 0);
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return (strcmp ("__restore", name) == 0
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|| strcmp ("__restore_rt", name) == 0);
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}
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/* Offset to struct sigcontext in ucontext, from <asm/ucontext.h>. */
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#define I386_LINUX_UCONTEXT_SIGCONTEXT_OFFSET 20
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/* Assuming NEXT_FRAME is a frame following a GNU/Linux sigtramp
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routine, return the address of the associated sigcontext structure. */
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static CORE_ADDR
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i386_linux_sigcontext_addr (struct frame_info *next_frame)
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{
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CORE_ADDR pc;
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CORE_ADDR sp;
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char buf[4];
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frame_unwind_register (next_frame, I386_ESP_REGNUM, buf);
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sp = extract_unsigned_integer (buf, 4);
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pc = i386_linux_sigtramp_start (frame_pc_unwind (next_frame));
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if (pc)
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{
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/* The sigcontext structure lives on the stack, right after
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the signum argument. We determine the address of the
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sigcontext structure by looking at the frame's stack
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pointer. Keep in mind that the first instruction of the
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sigtramp code is "pop %eax". If the PC is after this
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instruction, adjust the returned value accordingly. */
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if (pc == frame_pc_unwind (next_frame))
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return sp + 4;
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return sp;
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}
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pc = i386_linux_rt_sigtramp_start (frame_pc_unwind (next_frame));
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if (pc)
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{
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CORE_ADDR ucontext_addr;
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/* The sigcontext structure is part of the user context. A
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pointer to the user context is passed as the third argument
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to the signal handler. */
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read_memory (sp + 8, buf, 4);
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ucontext_addr = extract_unsigned_integer (buf, 4);
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return ucontext_addr + I386_LINUX_UCONTEXT_SIGCONTEXT_OFFSET;
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}
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error ("Couldn't recognize signal trampoline.");
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return 0;
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}
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/* Set the program counter for process PTID to PC. */
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static void
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i386_linux_write_pc (CORE_ADDR pc, ptid_t ptid)
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{
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write_register_pid (I386_EIP_REGNUM, pc, ptid);
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/* We must be careful with modifying the program counter. If we
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just interrupted a system call, the kernel might try to restart
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it when we resume the inferior. On restarting the system call,
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the kernel will try backing up the program counter even though it
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no longer points at the system call. This typically results in a
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SIGSEGV or SIGILL. We can prevent this by writing `-1' in the
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"orig_eax" pseudo-register.
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Note that "orig_eax" is saved when setting up a dummy call frame.
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This means that it is properly restored when that frame is
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popped, and that the interrupted system call will be restarted
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when we resume the inferior on return from a function call from
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within GDB. In all other cases the system call will not be
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restarted. */
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write_register_pid (I386_LINUX_ORIG_EAX_REGNUM, -1, ptid);
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}
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/* The register sets used in GNU/Linux ELF core-dumps are identical to
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the register sets in `struct user' that are used for a.out
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core-dumps. These are also used by ptrace(2). The corresponding
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types are `elf_gregset_t' for the general-purpose registers (with
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`elf_greg_t' the type of a single GP register) and `elf_fpregset_t'
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for the floating-point registers.
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Those types used to be available under the names `gregset_t' and
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`fpregset_t' too, and GDB used those names in the past. But those
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names are now used for the register sets used in the `mcontext_t'
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type, which have a different size and layout. */
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/* Mapping between the general-purpose registers in `struct user'
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format and GDB's register cache layout. */
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/* From <sys/reg.h>. */
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static int i386_linux_gregset_reg_offset[] =
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{
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6 * 4, /* %eax */
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1 * 4, /* %ecx */
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2 * 4, /* %edx */
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0 * 4, /* %ebx */
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15 * 4, /* %esp */
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5 * 4, /* %ebp */
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3 * 4, /* %esi */
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4 * 4, /* %edi */
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12 * 4, /* %eip */
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14 * 4, /* %eflags */
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13 * 4, /* %cs */
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16 * 4, /* %ss */
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7 * 4, /* %ds */
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8 * 4, /* %es */
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9 * 4, /* %fs */
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10 * 4, /* %gs */
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1,
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-1,
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11 * 4 /* "orig_eax" */
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};
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/* Mapping between the general-purpose registers in `struct
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sigcontext' format and GDB's register cache layout. */
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/* From <asm/sigcontext.h>. */
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static int i386_linux_sc_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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7 * 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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14 * 4, /* %eip */
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16 * 4, /* %eflags */
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15 * 4, /* %cs */
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18 * 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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static void
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i386_linux_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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/* GNU/Linux uses ELF. */
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i386_elf_init_abi (info, gdbarch);
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/* Since we have the extra "orig_eax" register on GNU/Linux, we have
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to adjust a few things. */
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set_gdbarch_write_pc (gdbarch, i386_linux_write_pc);
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set_gdbarch_num_regs (gdbarch, I386_LINUX_NUM_REGS);
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set_gdbarch_register_name (gdbarch, i386_linux_register_name);
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set_gdbarch_register_reggroup_p (gdbarch, i386_linux_register_reggroup_p);
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tdep->gregset_reg_offset = i386_linux_gregset_reg_offset;
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tdep->gregset_num_regs = ARRAY_SIZE (i386_linux_gregset_reg_offset);
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tdep->sizeof_gregset = 17 * 4;
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tdep->jb_pc_offset = 20; /* From <bits/setjmp.h>. */
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tdep->sigtramp_p = i386_linux_sigtramp_p;
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tdep->sigcontext_addr = i386_linux_sigcontext_addr;
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tdep->sc_reg_offset = i386_linux_sc_reg_offset;
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tdep->sc_num_regs = ARRAY_SIZE (i386_linux_sc_reg_offset);
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/* GNU/Linux 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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/* GNU/Linux uses the dynamic linker included in the GNU C Library. */
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set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver);
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}
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/* Provide a prototype to silence -Wmissing-prototypes. */
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extern void _initialize_i386_linux_tdep (void);
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void
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_initialize_i386_linux_tdep (void)
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{
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gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_LINUX,
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i386_linux_init_abi);
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}
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