245 lines
6.5 KiB
C
245 lines
6.5 KiB
C
/* Linux-specific ptrace manipulation routines.
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Copyright (C) 2012-2013 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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#ifdef GDBSERVER
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#include "server.h"
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#else
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#include "defs.h"
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#include "gdb_string.h"
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#endif
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#include "linux-ptrace.h"
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#include "linux-procfs.h"
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#include "buffer.h"
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#include "gdb_assert.h"
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#include "gdb_wait.h"
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/* Find all possible reasons we could fail to attach PID and append these
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newline terminated reason strings to initialized BUFFER. '\0' termination
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of BUFFER must be done by the caller. */
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void
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linux_ptrace_attach_warnings (pid_t pid, struct buffer *buffer)
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{
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pid_t tracerpid;
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tracerpid = linux_proc_get_tracerpid (pid);
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if (tracerpid > 0)
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buffer_xml_printf (buffer, _("warning: process %d is already traced "
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"by process %d\n"),
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(int) pid, (int) tracerpid);
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if (linux_proc_pid_is_zombie (pid))
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buffer_xml_printf (buffer, _("warning: process %d is a zombie "
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"- the process has already terminated\n"),
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(int) pid);
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}
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#if defined __i386__ || defined __x86_64__
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/* Address of the 'ret' instruction in asm code block below. */
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extern void (linux_ptrace_test_ret_to_nx_instr) (void);
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#include <sys/reg.h>
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#include <sys/mman.h>
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#include <signal.h>
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#include <stdint.h>
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#endif /* defined __i386__ || defined __x86_64__ */
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/* Test broken off-trunk Linux kernel patchset for NX support on i386. It was
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removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd.
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Test also x86_64 arch for PaX support. */
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static void
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linux_ptrace_test_ret_to_nx (void)
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{
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#if defined __i386__ || defined __x86_64__
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pid_t child, got_pid;
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gdb_byte *return_address, *pc;
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long l;
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int status;
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return_address = mmap (NULL, 2, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (return_address == MAP_FAILED)
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{
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warning (_("linux_ptrace_test_ret_to_nx: Cannot mmap: %s"),
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strerror (errno));
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return;
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}
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/* Put there 'int3'. */
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*return_address = 0xcc;
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child = fork ();
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switch (child)
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{
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case -1:
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warning (_("linux_ptrace_test_ret_to_nx: Cannot fork: %s"),
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strerror (errno));
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return;
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case 0:
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l = ptrace (PTRACE_TRACEME, 0, NULL, NULL);
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if (l != 0)
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warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_TRACEME: %s"),
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strerror (errno));
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else
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{
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#if defined __i386__
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asm volatile ("pushl %0;"
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".globl linux_ptrace_test_ret_to_nx_instr;"
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"linux_ptrace_test_ret_to_nx_instr:"
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"ret"
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: : "r" (return_address) : "%esp", "memory");
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#elif defined __x86_64__
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asm volatile ("pushq %0;"
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".globl linux_ptrace_test_ret_to_nx_instr;"
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"linux_ptrace_test_ret_to_nx_instr:"
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"ret"
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: : "r" (return_address) : "%rsp", "memory");
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#else
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# error "!__i386__ && !__x86_64__"
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#endif
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gdb_assert_not_reached ("asm block did not terminate");
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}
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_exit (1);
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}
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errno = 0;
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got_pid = waitpid (child, &status, 0);
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if (got_pid != child)
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{
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warning (_("linux_ptrace_test_ret_to_nx: waitpid returned %ld: %s"),
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(long) got_pid, strerror (errno));
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return;
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}
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if (WIFSIGNALED (status))
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{
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if (WTERMSIG (status) != SIGKILL)
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warning (_("linux_ptrace_test_ret_to_nx: WTERMSIG %d is not SIGKILL!"),
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(int) WTERMSIG (status));
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else
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warning (_("Cannot call inferior functions, Linux kernel PaX "
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"protection forbids return to non-executable pages!"));
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return;
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}
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if (!WIFSTOPPED (status))
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{
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warning (_("linux_ptrace_test_ret_to_nx: status %d is not WIFSTOPPED!"),
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status);
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return;
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}
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/* We may get SIGSEGV due to missing PROT_EXEC of the return_address. */
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if (WSTOPSIG (status) != SIGTRAP && WSTOPSIG (status) != SIGSEGV)
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{
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warning (_("linux_ptrace_test_ret_to_nx: "
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"WSTOPSIG %d is neither SIGTRAP nor SIGSEGV!"),
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(int) WSTOPSIG (status));
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return;
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}
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errno = 0;
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#if defined __i386__
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l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (EIP * 4), NULL);
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#elif defined __x86_64__
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l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (RIP * 8), NULL);
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#else
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# error "!__i386__ && !__x86_64__"
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#endif
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if (errno != 0)
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{
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warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_PEEKUSER: %s"),
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strerror (errno));
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return;
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}
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pc = (void *) (uintptr_t) l;
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if (ptrace (PTRACE_KILL, child, NULL, NULL) != 0)
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{
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warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_KILL: %s"),
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strerror (errno));
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return;
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}
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else
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{
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int kill_status;
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errno = 0;
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got_pid = waitpid (child, &kill_status, 0);
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if (got_pid != child)
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{
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warning (_("linux_ptrace_test_ret_to_nx: "
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"PTRACE_KILL waitpid returned %ld: %s"),
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(long) got_pid, strerror (errno));
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return;
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}
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if (!WIFSIGNALED (kill_status))
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{
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warning (_("linux_ptrace_test_ret_to_nx: "
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"PTRACE_KILL status %d is not WIFSIGNALED!"),
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status);
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return;
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}
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}
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/* + 1 is there as x86* stops after the 'int3' instruction. */
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if (WSTOPSIG (status) == SIGTRAP && pc == return_address + 1)
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{
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/* PASS */
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return;
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}
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/* We may get SIGSEGV due to missing PROT_EXEC of the RETURN_ADDRESS page. */
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if (WSTOPSIG (status) == SIGSEGV && pc == return_address)
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{
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/* PASS */
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return;
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}
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if ((void (*) (void)) pc != &linux_ptrace_test_ret_to_nx_instr)
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warning (_("linux_ptrace_test_ret_to_nx: PC %p is neither near return "
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"address %p nor is the return instruction %p!"),
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pc, return_address, &linux_ptrace_test_ret_to_nx_instr);
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else
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warning (_("Cannot call inferior functions, you have broken "
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"Linux kernel i386 NX (non-executable pages) support!"));
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#endif /* defined __i386__ || defined __x86_64__ */
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}
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/* Display possible problems on this system. Display them only once per GDB
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execution. */
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void
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linux_ptrace_init_warnings (void)
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{
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static int warned = 0;
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if (warned)
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return;
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warned = 1;
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linux_ptrace_test_ret_to_nx ();
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}
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