624 lines
18 KiB
C
624 lines
18 KiB
C
/* Linux-specific ptrace manipulation routines.
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Copyright (C) 2012-2015 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 "common-defs.h"
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#include "linux-ptrace.h"
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#include "linux-procfs.h"
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#include "linux-waitpid.h"
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#include "buffer.h"
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#include "gdb_wait.h"
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#include "gdb_ptrace.h"
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/* Stores the ptrace options supported by the running kernel.
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A value of -1 means we did not check for features yet. A value
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of 0 means there are no supported features. */
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static int supported_ptrace_options = -1;
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/* Find all possible reasons we could fail to attach PID and append
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these as strings to the already initialized BUFFER. '\0'
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termination of BUFFER must be done by the caller. */
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void
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linux_ptrace_attach_fail_reason (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_nowarn (pid);
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if (tracerpid > 0)
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buffer_xml_printf (buffer, _("process %d is already traced "
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"by process %d"),
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(int) pid, (int) tracerpid);
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if (linux_proc_pid_is_zombie_nowarn (pid))
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buffer_xml_printf (buffer, _("process %d is a zombie "
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"- the process has already terminated"),
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(int) pid);
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}
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/* See linux-ptrace.h. */
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char *
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linux_ptrace_attach_fail_reason_string (ptid_t ptid, int err)
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{
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static char *reason_string;
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struct buffer buffer;
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char *warnings;
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long lwpid = ptid_get_lwp (ptid);
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xfree (reason_string);
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buffer_init (&buffer);
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linux_ptrace_attach_fail_reason (lwpid, &buffer);
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buffer_grow_str0 (&buffer, "");
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warnings = buffer_finish (&buffer);
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if (warnings[0] != '\0')
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reason_string = xstrprintf ("%s (%d), %s",
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safe_strerror (err), err, warnings);
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else
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reason_string = xstrprintf ("%s (%d)",
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safe_strerror (err), err);
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xfree (warnings);
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return reason_string;
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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_C 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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safe_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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safe_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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safe_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, safe_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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safe_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, safe_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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static void linux_test_for_exitkill (int child_pid);
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/* Determine ptrace features available on this target. */
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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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supported_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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linux_test_for_exitkill (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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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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supported_ptrace_options |= PTRACE_O_TRACESYSGOOD;
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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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/* 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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supported_ptrace_options |= PTRACE_O_TRACEVFORKDONE;
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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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&& linux_ptrace_get_extended_event (status) == 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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supported_ptrace_options |= PTRACE_O_TRACECLONE;
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supported_ptrace_options |= (PTRACE_O_TRACEFORK
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| PTRACE_O_TRACEVFORK
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| PTRACE_O_TRACEEXEC);
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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,
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(PTRACE_TYPE_ARG4) 0);
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if (ret != 0)
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warning (_("linux_test_for_tracefork: "
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"failed to kill second child"));
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my_waitpid (second_pid, &status, 0);
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}
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}
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else
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warning (_("linux_test_for_tracefork: unexpected result from waitpid "
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"(%d, status 0x%x)"), ret, status);
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}
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/* Determine if PTRACE_O_EXITKILL can be used. */
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static void
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linux_test_for_exitkill (int child_pid)
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{
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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_EXITKILL);
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if (ret == 0)
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supported_ptrace_options |= PTRACE_O_EXITKILL;
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}
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/* Enable reporting of all currently supported ptrace events.
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OPTIONS is a bit mask of extended features we want enabled,
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if supported by the kernel. PTRACE_O_TRACECLONE is always
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enabled, if supported. */
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void
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linux_enable_event_reporting (pid_t pid, int options)
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{
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/* Check if we have initialized the ptrace features for this
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target. If not, do it now. */
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if (supported_ptrace_options == -1)
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linux_check_ptrace_features ();
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/* We always want clone events. */
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options |= PTRACE_O_TRACECLONE;
|
|
|
|
/* Filter out unsupported options. */
|
|
options &= supported_ptrace_options;
|
|
|
|
/* Set the options. */
|
|
ptrace (PTRACE_SETOPTIONS, pid, (PTRACE_TYPE_ARG3) 0,
|
|
(PTRACE_TYPE_ARG4) (uintptr_t) options);
|
|
}
|
|
|
|
/* Disable reporting of all currently supported ptrace events. */
|
|
|
|
void
|
|
linux_disable_event_reporting (pid_t pid)
|
|
{
|
|
/* Set the options. */
|
|
ptrace (PTRACE_SETOPTIONS, pid, (PTRACE_TYPE_ARG3) 0, 0);
|
|
}
|
|
|
|
/* Returns non-zero if PTRACE_OPTIONS is contained within
|
|
SUPPORTED_PTRACE_OPTIONS, therefore supported. Returns 0
|
|
otherwise. */
|
|
|
|
static int
|
|
ptrace_supports_feature (int ptrace_options)
|
|
{
|
|
if (supported_ptrace_options == -1)
|
|
linux_check_ptrace_features ();
|
|
|
|
return ((supported_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_EXEC is supported by ptrace,
|
|
0 otherwise. Note that if PTRACE_EVENT_FORK is supported so is
|
|
PTRACE_EVENT_CLONE, PTRACE_EVENT_FORK and PTRACE_EVENT_VFORK,
|
|
since they were all added to the kernel at the same time. */
|
|
|
|
int
|
|
linux_supports_traceexec (void)
|
|
{
|
|
return ptrace_supports_feature (PTRACE_O_TRACEEXEC);
|
|
}
|
|
|
|
/* 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 ();
|
|
}
|
|
|
|
/* Extract extended ptrace event from wait status. */
|
|
|
|
int
|
|
linux_ptrace_get_extended_event (int wstat)
|
|
{
|
|
return (wstat >> 16);
|
|
}
|
|
|
|
/* Determine whether wait status denotes an extended event. */
|
|
|
|
int
|
|
linux_is_extended_waitstatus (int wstat)
|
|
{
|
|
return (linux_ptrace_get_extended_event (wstat) != 0);
|
|
}
|
|
|
|
/* Return true if the event in LP may be caused by breakpoint. */
|
|
|
|
int
|
|
linux_wstatus_maybe_breakpoint (int wstat)
|
|
{
|
|
return (WIFSTOPPED (wstat)
|
|
&& (WSTOPSIG (wstat) == SIGTRAP
|
|
/* SIGILL and SIGSEGV are also treated as traps in case a
|
|
breakpoint is inserted at the current PC. */
|
|
|| WSTOPSIG (wstat) == SIGILL
|
|
|| WSTOPSIG (wstat) == SIGSEGV));
|
|
}
|