8ae377e842
If enabling PTRACE_O_TRACEFORK fails, we never test for PTRACE_O_TRACESYSGOOD support. Before PTRACE_O_TRACESYSGOOD is checked, we have: /* First, set the PTRACE_O_TRACEFORK option. If this fails, we know for sure that it is not supported. */ ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) PTRACE_O_TRACEFORK); if (ret != 0) { ret = ptrace (PTRACE_KILL, child_pid, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0); if (ret != 0) { warning (_("linux_check_ptrace_features: failed to kill child")); return; } ret = my_waitpid (child_pid, &status, 0); if (ret != child_pid) warning (_("linux_check_ptrace_features: failed " "to wait for killed child")); else if (!WIFSIGNALED (status)) warning (_("linux_check_ptrace_features: unexpected " "wait status 0x%x from killed child"), status); return; <<<<<<<<<<<<<<<<< } Note that early return. If PTRACE_O_TRACEFORK isn't supported, we're not checking PTRACE_O_TRACESYSGOOD. This didn't use to be a problem before the unification of this whole detection business in linux-ptrace.c. Before, the sysgood detection was completely separate: static void linux_test_for_tracesysgood (int original_pid) { int ret; sigset_t prev_mask; /* We don't want those ptrace calls to be interrupted. */ block_child_signals (&prev_mask); linux_supports_tracesysgood_flag = 0; ret = ptrace (PTRACE_SETOPTIONS, original_pid, 0, PTRACE_O_TRACESYSGOOD); if (ret != 0) goto out; linux_supports_tracesysgood_flag = 1; out: restore_child_signals_mask (&prev_mask); } So we need to get back the decoupling somehow. I think it's cleaner to split the seperate feature detections to separate functions. This patch does that. The new functions are named for their counterparts that existed before this code was moved to linux-ptrace.c. Note I've used forward declarations for the new functions to make the patch clearer, as otherwise the patch would look like I'd be adding a bunch of new code. A reorder can be done in a follow up patch. Tested on x86_64 Fedora 17. gdb/ 2013-10-03 Pedro Alves <palves@redhat.com> * common/linux-ptrace.c (linux_check_ptrace_features): Factor out the PTRACE_O_TRACESYSGOOD and PTRACE_O_TRACEFORK to separate functions. Always test for PTRACE_O_TRACESYSGOOD even if PTRACE_O_TRACEFORK is not supported. (linux_test_for_tracesysgood): New function. (linux_test_for_tracefork): New function, factored out from linux_check_ptrace_features, and also don't kill child_pid here.
544 lines
16 KiB
C
544 lines
16 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 "nat/linux-waitpid.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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#include <stdint.h>
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/* Stores the currently supported ptrace options. A value of
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-1 means we did not check for features yet. A value of 0 means
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there are no supported features. */
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static int current_ptrace_options = -1;
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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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#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, kill_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, (PTRACE_TYPE_ARG3) NULL,
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(PTRACE_TYPE_ARG4) 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" ((uint64_t) (uintptr_t) return_address)
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: "%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, (PTRACE_TYPE_ARG3) (uintptr_t) (EIP * 4),
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(PTRACE_TYPE_ARG4) NULL);
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#elif defined __x86_64__
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l = ptrace (PTRACE_PEEKUSER, child, (PTRACE_TYPE_ARG3) (uintptr_t) (RIP * 8),
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(PTRACE_TYPE_ARG4) 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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kill (child, SIGKILL);
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ptrace (PTRACE_KILL, child, (PTRACE_TYPE_ARG3) NULL,
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(PTRACE_TYPE_ARG4) NULL);
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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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/* + 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 on this system - "
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"Linux kernel with broken i386 NX (non-executable pages) "
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"support detected!"));
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#endif /* defined __i386__ || defined __x86_64__ */
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}
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/* Helper function to fork a process and make the child process call
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the function FUNCTION, passing CHILD_STACK as parameter.
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For MMU-less targets, clone is used instead of fork, and
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CHILD_STACK is used as stack space for the cloned child. If NULL,
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stack space is allocated via malloc (and subsequently passed to
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FUNCTION). For MMU targets, CHILD_STACK is ignored. */
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static int
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linux_fork_to_function (gdb_byte *child_stack, void (*function) (gdb_byte *))
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{
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int child_pid;
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/* Sanity check the function pointer. */
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gdb_assert (function != NULL);
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#if defined(__UCLIBC__) && defined(HAS_NOMMU)
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#define STACK_SIZE 4096
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if (child_stack == NULL)
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child_stack = xmalloc (STACK_SIZE * 4);
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/* Use CLONE_VM instead of fork, to support uClinux (no MMU). */
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#ifdef __ia64__
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child_pid = __clone2 (function, child_stack, STACK_SIZE,
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CLONE_VM | SIGCHLD, child_stack + STACK_SIZE * 2);
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#else /* !__ia64__ */
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child_pid = clone (function, child_stack + STACK_SIZE,
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CLONE_VM | SIGCHLD, child_stack + STACK_SIZE * 2);
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#endif /* !__ia64__ */
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#else /* !defined(__UCLIBC) && defined(HAS_NOMMU) */
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child_pid = fork ();
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if (child_pid == 0)
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function (NULL);
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#endif /* defined(__UCLIBC) && defined(HAS_NOMMU) */
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if (child_pid == -1)
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perror_with_name (("fork"));
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return child_pid;
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}
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/* A helper function for linux_check_ptrace_features, called after
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the child forks a grandchild. */
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static void
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linux_grandchild_function (gdb_byte *child_stack)
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{
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/* Free any allocated stack. */
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xfree (child_stack);
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/* This code is only reacheable by the grandchild (child's child)
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process. */
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_exit (0);
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}
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/* A helper function for linux_check_ptrace_features, called after
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the parent process forks a child. The child allows itself to
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be traced by its parent. */
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static void
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linux_child_function (gdb_byte *child_stack)
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{
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ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
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kill (getpid (), SIGSTOP);
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/* Fork a grandchild. */
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linux_fork_to_function (child_stack, linux_grandchild_function);
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/* This code is only reacheable by the child (grandchild's parent)
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process. */
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_exit (0);
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}
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static void linux_test_for_tracesysgood (int child_pid);
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static void linux_test_for_tracefork (int child_pid);
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/* Determine ptrace features available on this target. */
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static void
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linux_check_ptrace_features (void)
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{
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int child_pid, ret, status;
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/* Initialize the options. */
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current_ptrace_options = 0;
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/* Fork a child so we can do some testing. The child will call
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linux_child_function and will get traced. The child will
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eventually fork a grandchild so we can test fork event
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reporting. */
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child_pid = linux_fork_to_function (NULL, linux_child_function);
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ret = my_waitpid (child_pid, &status, 0);
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if (ret == -1)
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perror_with_name (("waitpid"));
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else if (ret != child_pid)
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error (_("linux_check_ptrace_features: waitpid: unexpected result %d."),
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ret);
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if (! WIFSTOPPED (status))
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error (_("linux_check_ptrace_features: waitpid: unexpected status %d."),
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status);
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linux_test_for_tracesysgood (child_pid);
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linux_test_for_tracefork (child_pid);
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/* Clean things up and kill any pending children. */
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do
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{
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ret = ptrace (PTRACE_KILL, child_pid, (PTRACE_TYPE_ARG3) 0,
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(PTRACE_TYPE_ARG4) 0);
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if (ret != 0)
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warning (_("linux_check_ptrace_features: failed to kill child"));
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my_waitpid (child_pid, &status, 0);
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}
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while (WIFSTOPPED (status));
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}
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/* Determine if PTRACE_O_TRACESYSGOOD can be used to catch
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syscalls. */
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static void
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linux_test_for_tracesysgood (int child_pid)
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{
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#ifdef GDBSERVER
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/* gdbserver does not support PTRACE_O_TRACESYSGOOD. */
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#else
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int ret;
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ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
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(PTRACE_TYPE_ARG4) PTRACE_O_TRACESYSGOOD);
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if (ret == 0)
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current_ptrace_options |= PTRACE_O_TRACESYSGOOD;
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#endif
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}
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/* Determine if PTRACE_O_TRACEFORK can be used to follow fork
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events. */
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static void
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linux_test_for_tracefork (int child_pid)
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{
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int ret, status;
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long second_pid;
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/* First, set the PTRACE_O_TRACEFORK option. If this fails, we
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know for sure that it is not supported. */
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ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
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(PTRACE_TYPE_ARG4) PTRACE_O_TRACEFORK);
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if (ret != 0)
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return;
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#ifdef GDBSERVER
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/* gdbserver does not support PTRACE_O_TRACEVFORKDONE yet. */
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#else
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/* Check if the target supports PTRACE_O_TRACEVFORKDONE. */
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ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
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(PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
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| PTRACE_O_TRACEVFORKDONE));
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if (ret == 0)
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current_ptrace_options |= PTRACE_O_TRACEVFORKDONE;
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#endif
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/* Setting PTRACE_O_TRACEFORK did not cause an error, however we
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don't know for sure that the feature is available; old
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versions of PTRACE_SETOPTIONS ignored unknown options.
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Therefore, we attach to the child process, use PTRACE_SETOPTIONS
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to enable fork tracing, and let it fork. If the process exits,
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we assume that we can't use PTRACE_O_TRACEFORK; if we get the
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fork notification, and we can extract the new child's PID, then
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we assume that we can.
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We do not explicitly check for vfork tracing here. It is
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assumed that vfork tracing is available whenever fork tracing
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is available. */
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ret = ptrace (PTRACE_CONT, child_pid, (PTRACE_TYPE_ARG3) 0,
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(PTRACE_TYPE_ARG4) 0);
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if (ret != 0)
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warning (_("linux_test_for_tracefork: failed to resume child"));
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ret = my_waitpid (child_pid, &status, 0);
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/* Check if we received a fork event notification. */
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if (ret == child_pid && WIFSTOPPED (status)
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&& status >> 16 == PTRACE_EVENT_FORK)
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{
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/* We did receive a fork event notification. Make sure its PID
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is reported. */
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second_pid = 0;
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ret = ptrace (PTRACE_GETEVENTMSG, child_pid, (PTRACE_TYPE_ARG3) 0,
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(PTRACE_TYPE_ARG4) &second_pid);
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if (ret == 0 && second_pid != 0)
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{
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int second_status;
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/* We got the PID from the grandchild, which means fork
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tracing is supported. */
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#ifdef GDBSERVER
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/* Do not enable all the options for now since gdbserver does not
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properly support them. This restriction will be lifted when
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gdbserver is augmented to support them. */
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current_ptrace_options |= PTRACE_O_TRACECLONE;
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#else
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current_ptrace_options |= PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK
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| PTRACE_O_TRACECLONE | PTRACE_O_TRACEEXEC;
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/* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to
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support read-only process state. */
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#endif
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/* Do some cleanup and kill the grandchild. */
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my_waitpid (second_pid, &second_status, 0);
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ret = ptrace (PTRACE_KILL, second_pid, (PTRACE_TYPE_ARG3) 0,
|
|
(PTRACE_TYPE_ARG4) 0);
|
|
if (ret != 0)
|
|
warning (_("linux_test_for_tracefork: "
|
|
"failed to kill second child"));
|
|
my_waitpid (second_pid, &status, 0);
|
|
}
|
|
}
|
|
else
|
|
warning (_("linux_test_for_tracefork: unexpected result from waitpid "
|
|
"(%d, status 0x%x)"), ret, status);
|
|
}
|
|
|
|
/* Enable reporting of all currently supported ptrace events. */
|
|
|
|
void
|
|
linux_enable_event_reporting (pid_t pid)
|
|
{
|
|
/* Check if we have initialized the ptrace features for this
|
|
target. If not, do it now. */
|
|
if (current_ptrace_options == -1)
|
|
linux_check_ptrace_features ();
|
|
|
|
/* Set the options. */
|
|
ptrace (PTRACE_SETOPTIONS, pid, (PTRACE_TYPE_ARG3) 0,
|
|
(PTRACE_TYPE_ARG4) (uintptr_t) current_ptrace_options);
|
|
}
|
|
|
|
/* Returns non-zero if PTRACE_OPTIONS is contained within
|
|
CURRENT_PTRACE_OPTIONS, therefore supported. Returns 0
|
|
otherwise. */
|
|
|
|
static int
|
|
ptrace_supports_feature (int ptrace_options)
|
|
{
|
|
gdb_assert (current_ptrace_options >= 0);
|
|
|
|
return ((current_ptrace_options & ptrace_options) == ptrace_options);
|
|
}
|
|
|
|
/* Returns non-zero if PTRACE_EVENT_FORK is supported by ptrace,
|
|
0 otherwise. Note that if PTRACE_EVENT_FORK is supported so is
|
|
PTRACE_EVENT_CLONE, PTRACE_EVENT_EXEC and PTRACE_EVENT_VFORK,
|
|
since they were all added to the kernel at the same time. */
|
|
|
|
int
|
|
linux_supports_tracefork (void)
|
|
{
|
|
return ptrace_supports_feature (PTRACE_O_TRACEFORK);
|
|
}
|
|
|
|
/* Returns non-zero if PTRACE_EVENT_CLONE is supported by ptrace,
|
|
0 otherwise. Note that if PTRACE_EVENT_CLONE is supported so is
|
|
PTRACE_EVENT_FORK, PTRACE_EVENT_EXEC and PTRACE_EVENT_VFORK,
|
|
since they were all added to the kernel at the same time. */
|
|
|
|
int
|
|
linux_supports_traceclone (void)
|
|
{
|
|
return ptrace_supports_feature (PTRACE_O_TRACECLONE);
|
|
}
|
|
|
|
/* Returns non-zero if PTRACE_O_TRACEVFORKDONE is supported by
|
|
ptrace, 0 otherwise. */
|
|
|
|
int
|
|
linux_supports_tracevforkdone (void)
|
|
{
|
|
return ptrace_supports_feature (PTRACE_O_TRACEVFORKDONE);
|
|
}
|
|
|
|
/* Returns non-zero if PTRACE_O_TRACESYSGOOD is supported by ptrace,
|
|
0 otherwise. */
|
|
|
|
int
|
|
linux_supports_tracesysgood (void)
|
|
{
|
|
return ptrace_supports_feature (PTRACE_O_TRACESYSGOOD);
|
|
}
|
|
|
|
/* Display possible problems on this system. Display them only once per GDB
|
|
execution. */
|
|
|
|
void
|
|
linux_ptrace_init_warnings (void)
|
|
{
|
|
static int warned = 0;
|
|
|
|
if (warned)
|
|
return;
|
|
warned = 1;
|
|
|
|
linux_ptrace_test_ret_to_nx ();
|
|
}
|