[deliverable/binutils-gdb.git] / gdb / nat / linux-ptrace.c

/* Linux-specific ptrace manipulation routines.
   Copyright (C) 2012-2018 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "common-defs.h"
#include "linux-ptrace.h"
#include "linux-procfs.h"
#include "linux-waitpid.h"
#include "buffer.h"
#ifdef HAVE_SYS_PROCFS_H
#include <sys/procfs.h>
#endif

/* Stores the ptrace options supported by the running kernel.
   A value of -1 means we did not check for features yet.  A value
   of 0 means there are no supported features.  */
static int supported_ptrace_options = -1;

/* Find all possible reasons we could fail to attach PID and return these
   as a string.  An empty string is returned if we didn't find any reason.  */

std::string
linux_ptrace_attach_fail_reason (pid_t pid)
{
  pid_t tracerpid = linux_proc_get_tracerpid_nowarn (pid);
  std::string result;

  if (tracerpid > 0)
    string_appendf (result,
		    _("process %d is already traced by process %d"),
		    (int) pid, (int) tracerpid);

  if (linux_proc_pid_is_zombie_nowarn (pid))
    string_appendf (result,
		    _("process %d is a zombie - the process has already "
		      "terminated"),
		    (int) pid);

  return result;
}

/* See linux-ptrace.h.  */

std::string
linux_ptrace_attach_fail_reason_string (ptid_t ptid, int err)
{
  long lwpid = ptid.lwp ();
  std::string reason = linux_ptrace_attach_fail_reason (lwpid);

  if (!reason.empty ())
    return string_printf ("%s (%d), %s", safe_strerror (err), err,
			  reason.c_str ());
  else
    return string_printf ("%s (%d)", safe_strerror (err), err);
}

#if defined __i386__ || defined __x86_64__

/* Address of the 'ret' instruction in asm code block below.  */
EXTERN_C void linux_ptrace_test_ret_to_nx_instr (void);

#include <sys/reg.h>
#include <sys/mman.h>
#include <signal.h>

#endif /* defined __i386__ || defined __x86_64__ */

/* Test broken off-trunk Linux kernel patchset for NX support on i386.  It was
   removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd.

   Test also x86_64 arch for PaX support.  */

static void
linux_ptrace_test_ret_to_nx (void)
{
#if defined __i386__ || defined __x86_64__
  pid_t child, got_pid;
  gdb_byte *return_address, *pc;
  long l;
  int status, kill_status;
  elf_gregset_t regs;

  return_address
    = (gdb_byte *) mmap (NULL, 2, PROT_READ | PROT_WRITE,
			 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  if (return_address == MAP_FAILED)
    {
      warning (_("linux_ptrace_test_ret_to_nx: Cannot mmap: %s"),
	       safe_strerror (errno));
      return;
    }

  /* Put there 'int3'.  */
  *return_address = 0xcc;

  child = fork ();
  switch (child)
    {
    case -1:
      warning (_("linux_ptrace_test_ret_to_nx: Cannot fork: %s"),
	       safe_strerror (errno));
      return;

    case 0:
      l = ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) NULL,
		  (PTRACE_TYPE_ARG4) NULL);
      if (l != 0)
	warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_TRACEME: %s"),
		 safe_strerror (errno));
      else
	{
#if defined __i386__
	  asm volatile ("pushl %0;"
			".globl linux_ptrace_test_ret_to_nx_instr;"
			"linux_ptrace_test_ret_to_nx_instr:"
			"ret"
			: : "r" (return_address) : "%esp", "memory");
#elif defined __x86_64__
	  asm volatile ("pushq %0;"
			".globl linux_ptrace_test_ret_to_nx_instr;"
			"linux_ptrace_test_ret_to_nx_instr:"
			"ret"
			: : "r" ((uint64_t) (uintptr_t) return_address)
			: "%rsp", "memory");
#else
# error "!__i386__ && !__x86_64__"
#endif
	  gdb_assert_not_reached ("asm block did not terminate");
	}

      _exit (1);
    }

  errno = 0;
  got_pid = waitpid (child, &status, 0);
  if (got_pid != child)
    {
      warning (_("linux_ptrace_test_ret_to_nx: waitpid returned %ld: %s"),
	       (long) got_pid, safe_strerror (errno));
      return;
    }

  if (WIFSIGNALED (status))
    {
      if (WTERMSIG (status) != SIGKILL)
	warning (_("linux_ptrace_test_ret_to_nx: WTERMSIG %d is not SIGKILL!"),
		 (int) WTERMSIG (status));
      else
	warning (_("Cannot call inferior functions, Linux kernel PaX "
		   "protection forbids return to non-executable pages!"));
      return;
    }

  if (!WIFSTOPPED (status))
    {
      warning (_("linux_ptrace_test_ret_to_nx: status %d is not WIFSTOPPED!"),
	       status);
      return;
    }

  /* We may get SIGSEGV due to missing PROT_EXEC of the return_address.  */
  if (WSTOPSIG (status) != SIGTRAP && WSTOPSIG (status) != SIGSEGV)
    {
      warning (_("linux_ptrace_test_ret_to_nx: "
		 "WSTOPSIG %d is neither SIGTRAP nor SIGSEGV!"),
	       (int) WSTOPSIG (status));
      return;
    }

  if (ptrace (PTRACE_GETREGS, child, (PTRACE_TYPE_ARG3) 0,
	      (PTRACE_TYPE_ARG4) &regs) < 0)
    {
      warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_GETREGS: %s"),
	       safe_strerror (errno));
    }
#if defined __i386__
  pc = (gdb_byte *) (uintptr_t) regs[EIP];
#elif defined __x86_64__
  pc = (gdb_byte *) (uintptr_t) regs[RIP];
#else
# error "!__i386__ && !__x86_64__"
#endif

  kill (child, SIGKILL);
  ptrace (PTRACE_KILL, child, (PTRACE_TYPE_ARG3) NULL,
	  (PTRACE_TYPE_ARG4) NULL);

  errno = 0;
  got_pid = waitpid (child, &kill_status, 0);
  if (got_pid != child)
    {
      warning (_("linux_ptrace_test_ret_to_nx: "
		 "PTRACE_KILL waitpid returned %ld: %s"),
	       (long) got_pid, safe_strerror (errno));
      return;
    }
  if (!WIFSIGNALED (kill_status))
    {
      warning (_("linux_ptrace_test_ret_to_nx: "
		 "PTRACE_KILL status %d is not WIFSIGNALED!"),
	       status);
      return;
    }

  /* + 1 is there as x86* stops after the 'int3' instruction.  */
  if (WSTOPSIG (status) == SIGTRAP && pc == return_address + 1)
    {
      /* PASS */
      return;
    }

  /* We may get SIGSEGV due to missing PROT_EXEC of the RETURN_ADDRESS page.  */
  if (WSTOPSIG (status) == SIGSEGV && pc == return_address)
    {
      /* PASS */
      return;
    }

  if ((void (*) (void)) pc != &linux_ptrace_test_ret_to_nx_instr)
    warning (_("linux_ptrace_test_ret_to_nx: PC %p is neither near return "
	       "address %p nor is the return instruction %p!"),
	     pc, return_address, &linux_ptrace_test_ret_to_nx_instr);
  else
    warning (_("Cannot call inferior functions on this system - "
	       "Linux kernel with broken i386 NX (non-executable pages) "
	       "support detected!"));
#endif /* defined __i386__ || defined __x86_64__ */
}

/* Helper function to fork a process and make the child process call
   the function FUNCTION, passing CHILD_STACK as parameter.

   For MMU-less targets, clone is used instead of fork, and
   CHILD_STACK is used as stack space for the cloned child.  If NULL,
   stack space is allocated via malloc (and subsequently passed to
   FUNCTION).  For MMU targets, CHILD_STACK is ignored.  */

static int
linux_fork_to_function (gdb_byte *child_stack, int (*function) (void *))
{
  int child_pid;

  /* Sanity check the function pointer.  */
  gdb_assert (function != NULL);

#if defined(__UCLIBC__) && defined(HAS_NOMMU)
#define STACK_SIZE 4096

    if (child_stack == NULL)
      child_stack = (gdb_byte *) xmalloc (STACK_SIZE * 4);

    /* Use CLONE_VM instead of fork, to support uClinux (no MMU).  */
#ifdef __ia64__
      child_pid = __clone2 (function, child_stack, STACK_SIZE,
			    CLONE_VM | SIGCHLD, child_stack + STACK_SIZE * 2);
#else /* !__ia64__ */
      child_pid = clone (function, child_stack + STACK_SIZE,
			 CLONE_VM | SIGCHLD, child_stack + STACK_SIZE * 2);
#endif /* !__ia64__ */
#else /* !defined(__UCLIBC) && defined(HAS_NOMMU) */
  child_pid = fork ();

  if (child_pid == 0)
    function (NULL);
#endif /* defined(__UCLIBC) && defined(HAS_NOMMU) */

  if (child_pid == -1)
    perror_with_name (("fork"));

  return child_pid;
}

/* A helper function for linux_check_ptrace_features, called after
   the child forks a grandchild.  */

static int
linux_grandchild_function (void *child_stack)
{
  /* Free any allocated stack.  */
  xfree (child_stack);

  /* This code is only reacheable by the grandchild (child's child)
     process.  */
  _exit (0);
}

/* A helper function for linux_check_ptrace_features, called after
   the parent process forks a child.  The child allows itself to
   be traced by its parent.  */

static int
linux_child_function (void *child_stack)
{
  ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
  kill (getpid (), SIGSTOP);

  /* Fork a grandchild.  */
  linux_fork_to_function ((gdb_byte *) child_stack, linux_grandchild_function);

  /* This code is only reacheable by the child (grandchild's parent)
     process.  */
  _exit (0);
}

static void linux_test_for_tracesysgood (int child_pid);
static void linux_test_for_tracefork (int child_pid);
static void linux_test_for_exitkill (int child_pid);

/* Determine ptrace features available on this target.  */

void
linux_check_ptrace_features (void)
{
  int child_pid, ret, status;

  /* Initialize the options.  */
  supported_ptrace_options = 0;

  /* Fork a child so we can do some testing.  The child will call
     linux_child_function and will get traced.  The child will
     eventually fork a grandchild so we can test fork event
     reporting.  */
  child_pid = linux_fork_to_function (NULL, linux_child_function);

  ret = my_waitpid (child_pid, &status, 0);
  if (ret == -1)
    perror_with_name (("waitpid"));
  else if (ret != child_pid)
    error (_("linux_check_ptrace_features: waitpid: unexpected result %d."),
	   ret);
  if (! WIFSTOPPED (status))
    error (_("linux_check_ptrace_features: waitpid: unexpected status %d."),
	   status);

  linux_test_for_tracesysgood (child_pid);

  linux_test_for_tracefork (child_pid);

  linux_test_for_exitkill (child_pid);

  /* Clean things up and kill any pending children.  */
  do
    {
      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"));
      my_waitpid (child_pid, &status, 0);
    }
  while (WIFSTOPPED (status));
}

/* Determine if PTRACE_O_TRACESYSGOOD can be used to catch
   syscalls.  */

static void
linux_test_for_tracesysgood (int child_pid)
{
  int ret;

  ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
		(PTRACE_TYPE_ARG4) PTRACE_O_TRACESYSGOOD);

  if (ret == 0)
    supported_ptrace_options |= PTRACE_O_TRACESYSGOOD;
}

/* Determine if PTRACE_O_TRACEFORK can be used to follow fork
   events.  */

static void
linux_test_for_tracefork (int child_pid)
{
  int ret, status;
  long second_pid;

  /* 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)
    return;

  /* Check if the target supports PTRACE_O_TRACEVFORKDONE.  */
  ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
		(PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
				    | PTRACE_O_TRACEVFORKDONE));
  if (ret == 0)
    supported_ptrace_options |= PTRACE_O_TRACEVFORKDONE;

  /* Setting PTRACE_O_TRACEFORK did not cause an error, however we
     don't know for sure that the feature is available; old
     versions of PTRACE_SETOPTIONS ignored unknown options.
     Therefore, we attach to the child process, use PTRACE_SETOPTIONS
     to enable fork tracing, and let it fork.  If the process exits,
     we assume that we can't use PTRACE_O_TRACEFORK; if we get the
     fork notification, and we can extract the new child's PID, then
     we assume that we can.

     We do not explicitly check for vfork tracing here.  It is
     assumed that vfork tracing is available whenever fork tracing
     is available.  */
  ret = ptrace (PTRACE_CONT, child_pid, (PTRACE_TYPE_ARG3) 0,
		(PTRACE_TYPE_ARG4) 0);
  if (ret != 0)
    warning (_("linux_test_for_tracefork: failed to resume child"));

  ret = my_waitpid (child_pid, &status, 0);

  /* Check if we received a fork event notification.  */
  if (ret == child_pid && WIFSTOPPED (status)
      && linux_ptrace_get_extended_event (status) == PTRACE_EVENT_FORK)
    {
      /* We did receive a fork event notification.  Make sure its PID
	 is reported.  */
      second_pid = 0;
      ret = ptrace (PTRACE_GETEVENTMSG, child_pid, (PTRACE_TYPE_ARG3) 0,
		    (PTRACE_TYPE_ARG4) &second_pid);
      if (ret == 0 && second_pid != 0)
	{
	  int second_status;

	  /* We got the PID from the grandchild, which means fork
	     tracing is supported.  */
	  supported_ptrace_options |= PTRACE_O_TRACECLONE;
	  supported_ptrace_options |= (PTRACE_O_TRACEFORK
				       | PTRACE_O_TRACEVFORK
				       | PTRACE_O_TRACEEXEC);

	  /* Do some cleanup and kill the grandchild.  */
	  my_waitpid (second_pid, &second_status, 0);
	  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);
}

/* Determine if PTRACE_O_EXITKILL can be used.  */

static void
linux_test_for_exitkill (int child_pid)
{
  int ret;

  ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
		(PTRACE_TYPE_ARG4) PTRACE_O_EXITKILL);

  if (ret == 0)
    supported_ptrace_options |= PTRACE_O_EXITKILL;
}

/* Enable reporting of all currently supported ptrace events.
   OPTIONS is a bit mask of extended features we want enabled,
   if supported by the kernel.  PTRACE_O_TRACECLONE is always
   enabled, if supported.  */

void
linux_enable_event_reporting (pid_t pid, int options)
{
  /* Check if we have initialized the ptrace features for this
     target.  If not, do it now.  */
  if (supported_ptrace_options == -1)
    linux_check_ptrace_features ();

  /* We always want clone events.  */
  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));
}
Commit	Line	Data
5f572dec	1	/* Linux-specific ptrace manipulation routines.
e2882c85	2	Copyright (C) 2012-2018 Free Software Foundation, Inc.
5f572dec JK	3
	4	This file is part of GDB.
	5
	6	This program is free software; you can redistribute it and/or modify
	7	it under the terms of the GNU General Public License as published by
	8	the Free Software Foundation; either version 3 of the License, or
	9	(at your option) any later version.
	10
	11	This program is distributed in the hope that it will be useful,
	12	but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	GNU General Public License for more details.
	15
	16	You should have received a copy of the GNU General Public License
	17	along with this program. If not, see <http://www.gnu.org/licenses/>. */
	18
727605ca	19	#include "common-defs.h"
5f572dec	20	#include "linux-ptrace.h"
87b0bb13	21	#include "linux-procfs.h"
125f8a3d	22	#include "linux-waitpid.h"
87b0bb13	23	#include "buffer.h"
2132fe85	24	#ifdef HAVE_SYS_PROCFS_H
39b22471	25	#include <sys/procfs.h>
2132fe85	26	#endif
87b0bb13	27
de0d863e DB	28	/* Stores the ptrace options supported by the running kernel.
	29	A value of -1 means we did not check for features yet. A value
	30	of 0 means there are no supported features. */
	31	static int supported_ptrace_options = -1;
8009206a	32
4d9b86e1 SM	33	/* Find all possible reasons we could fail to attach PID and return these
4d9b86e1 SM	34	as a string. An empty string is returned if we didn't find any reason. */
87b0bb13	35
4d9b86e1 SM	36	std::string
4d9b86e1 SM	37	linux_ptrace_attach_fail_reason (pid_t pid)
87b0bb13	38	{
4d9b86e1 SM	39	pid_t tracerpid = linux_proc_get_tracerpid_nowarn (pid);
4d9b86e1 SM	40	std::string result;
87b0bb13	41
87b0bb13	42	if (tracerpid > 0)
4d9b86e1 SM	43	string_appendf (result,
	44	_("process %d is already traced by process %d"),
	45	(int) pid, (int) tracerpid);
87b0bb13	46
8784d563	47	if (linux_proc_pid_is_zombie_nowarn (pid))
4d9b86e1 SM	48	string_appendf (result,
	49	_("process %d is a zombie - the process has already "
	50	"terminated"),
	51	(int) pid);
	52
	53	return result;
87b0bb13	54	}
aa7c7447	55
8784d563 PA	56	/* See linux-ptrace.h. */
8784d563 PA	57
4d9b86e1	58	std::string
8784d563 PA	59	linux_ptrace_attach_fail_reason_string (ptid_t ptid, int err)
8784d563 PA	60	{
4d9b86e1 SM	61	long lwpid = ptid.lwp ();
	62	std::string reason = linux_ptrace_attach_fail_reason (lwpid);
	63
	64	if (!reason.empty ())
	65	return string_printf ("%s (%d), %s", safe_strerror (err), err,
	66	reason.c_str ());
8784d563	67	else
4d9b86e1	68	return string_printf ("%s (%d)", safe_strerror (err), err);
8784d563 PA	69	}
8784d563 PA	70
6e3c039e	71	#if defined __i386__ \|\| defined __x86_64__
aa7c7447 JK	72
aa7c7447 JK	73	/* Address of the 'ret' instruction in asm code block below. */
56000a98	74	EXTERN_C void linux_ptrace_test_ret_to_nx_instr (void);
aa7c7447 JK	75
	76	#include <sys/reg.h>
	77	#include <sys/mman.h>
	78	#include <signal.h>
aa7c7447	79
6e3c039e	80	#endif /* defined __i386__ \|\| defined __x86_64__ */
aa7c7447 JK	81
aa7c7447 JK	82	/* Test broken off-trunk Linux kernel patchset for NX support on i386. It was
6e3c039e JK	83	removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd.
	84
	85	Test also x86_64 arch for PaX support. */
aa7c7447 JK	86
	87	static void
	88	linux_ptrace_test_ret_to_nx (void)
	89	{
6e3c039e	90	#if defined __i386__ \|\| defined __x86_64__
aa7c7447 JK	91	pid_t child, got_pid;
	92	gdb_byte return_address, pc;
	93	long l;
61a31a67	94	int status, kill_status;
40c31709	95	elf_gregset_t regs;
aa7c7447	96
224c3ddb SM	97	return_address
224c3ddb SM	98	= (gdb_byte *) mmap (NULL, 2, PROT_READ \| PROT_WRITE,
aa7c7447 JK	99	MAP_PRIVATE \| MAP_ANONYMOUS, -1, 0);
	100	if (return_address == MAP_FAILED)
	101	{
	102	warning (_("linux_ptrace_test_ret_to_nx: Cannot mmap: %s"),
049bb5de	103	safe_strerror (errno));
aa7c7447 JK	104	return;
	105	}
	106
	107	/* Put there 'int3'. */
	108	*return_address = 0xcc;
	109
	110	child = fork ();
	111	switch (child)
	112	{
	113	case -1:
	114	warning (_("linux_ptrace_test_ret_to_nx: Cannot fork: %s"),
049bb5de	115	safe_strerror (errno));
aa7c7447 JK	116	return;
	117
	118	case 0:
96d7229d LM	119	l = ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) NULL,
96d7229d LM	120	(PTRACE_TYPE_ARG4) NULL);
aa7c7447 JK	121	if (l != 0)
aa7c7447 JK	122	warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_TRACEME: %s"),
049bb5de	123	safe_strerror (errno));
aa7c7447 JK	124	else
aa7c7447 JK	125	{
6e3c039e	126	#if defined __i386__
aa7c7447 JK	127	asm volatile ("pushl %0;"
	128	".globl linux_ptrace_test_ret_to_nx_instr;"
	129	"linux_ptrace_test_ret_to_nx_instr:"
	130	"ret"
	131	: : "r" (return_address) : "%esp", "memory");
6e3c039e JK	132	#elif defined __x86_64__
	133	asm volatile ("pushq %0;"
	134	".globl linux_ptrace_test_ret_to_nx_instr;"
	135	"linux_ptrace_test_ret_to_nx_instr:"
	136	"ret"
bdad4180 MF	137	: : "r" ((uint64_t) (uintptr_t) return_address)
bdad4180 MF	138	: "%rsp", "memory");
6e3c039e JK	139	#else
	140	# error "!__i386__ && !__x86_64__"
	141	#endif
aa7c7447 JK	142	gdb_assert_not_reached ("asm block did not terminate");
	143	}
	144
	145	_exit (1);
	146	}
	147
6e3c039e	148	errno = 0;
aa7c7447	149	got_pid = waitpid (child, &status, 0);
6e3c039e JK	150	if (got_pid != child)
	151	{
	152	warning (_("linux_ptrace_test_ret_to_nx: waitpid returned %ld: %s"),
049bb5de	153	(long) got_pid, safe_strerror (errno));
6e3c039e JK	154	return;
	155	}
	156
	157	if (WIFSIGNALED (status))
	158	{
	159	if (WTERMSIG (status) != SIGKILL)
	160	warning (_("linux_ptrace_test_ret_to_nx: WTERMSIG %d is not SIGKILL!"),
	161	(int) WTERMSIG (status));
	162	else
	163	warning (_("Cannot call inferior functions, Linux kernel PaX "
	164	"protection forbids return to non-executable pages!"));
	165	return;
	166	}
	167
	168	if (!WIFSTOPPED (status))
	169	{
	170	warning (_("linux_ptrace_test_ret_to_nx: status %d is not WIFSTOPPED!"),
	171	status);
	172	return;
	173	}
aa7c7447 JK	174
aa7c7447 JK	175	/* We may get SIGSEGV due to missing PROT_EXEC of the return_address. */
6e3c039e JK	176	if (WSTOPSIG (status) != SIGTRAP && WSTOPSIG (status) != SIGSEGV)
	177	{
	178	warning (_("linux_ptrace_test_ret_to_nx: "
	179	"WSTOPSIG %d is neither SIGTRAP nor SIGSEGV!"),
	180	(int) WSTOPSIG (status));
	181	return;
	182	}
aa7c7447	183
40c31709 PA	184	if (ptrace (PTRACE_GETREGS, child, (PTRACE_TYPE_ARG3) 0,
	185	(PTRACE_TYPE_ARG4) &regs) < 0)
	186	{
	187	warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_GETREGS: %s"),
	188	safe_strerror (errno));
	189	}
6e3c039e	190	#if defined __i386__
40c31709	191	pc = (gdb_byte *) (uintptr_t) regs[EIP];
6e3c039e	192	#elif defined __x86_64__
40c31709	193	pc = (gdb_byte *) (uintptr_t) regs[RIP];
6e3c039e JK	194	#else
	195	# error "!__i386__ && !__x86_64__"
	196	#endif
aa7c7447	197
61a31a67	198	kill (child, SIGKILL);
96d7229d LM	199	ptrace (PTRACE_KILL, child, (PTRACE_TYPE_ARG3) NULL,
96d7229d LM	200	(PTRACE_TYPE_ARG4) NULL);
61a31a67 JK	201
	202	errno = 0;
	203	got_pid = waitpid (child, &kill_status, 0);
	204	if (got_pid != child)
6e3c039e	205	{
61a31a67 JK	206	warning (_("linux_ptrace_test_ret_to_nx: "
61a31a67 JK	207	"PTRACE_KILL waitpid returned %ld: %s"),
049bb5de	208	(long) got_pid, safe_strerror (errno));
6e3c039e JK	209	return;
6e3c039e JK	210	}
61a31a67	211	if (!WIFSIGNALED (kill_status))
aa7c7447	212	{
61a31a67 JK	213	warning (_("linux_ptrace_test_ret_to_nx: "
	214	"PTRACE_KILL status %d is not WIFSIGNALED!"),
	215	status);
	216	return;
aa7c7447 JK	217	}
	218
	219	/* + 1 is there as x86* stops after the 'int3' instruction. */
	220	if (WSTOPSIG (status) == SIGTRAP && pc == return_address + 1)
	221	{
	222	/* PASS */
	223	return;
	224	}
	225
	226	/* We may get SIGSEGV due to missing PROT_EXEC of the RETURN_ADDRESS page. */
	227	if (WSTOPSIG (status) == SIGSEGV && pc == return_address)
	228	{
	229	/* PASS */
	230	return;
	231	}
	232
6e3c039e JK	233	if ((void (*) (void)) pc != &linux_ptrace_test_ret_to_nx_instr)
	234	warning (_("linux_ptrace_test_ret_to_nx: PC %p is neither near return "
	235	"address %p nor is the return instruction %p!"),
	236	pc, return_address, &linux_ptrace_test_ret_to_nx_instr);
	237	else
025e6dce PA	238	warning (_("Cannot call inferior functions on this system - "
	239	"Linux kernel with broken i386 NX (non-executable pages) "
	240	"support detected!"));
6e3c039e	241	#endif /* defined __i386__ \|\| defined __x86_64__ */
aa7c7447 JK	242	}
aa7c7447 JK	243
96d7229d LM	244	/* Helper function to fork a process and make the child process call
	245	the function FUNCTION, passing CHILD_STACK as parameter.
	246
	247	For MMU-less targets, clone is used instead of fork, and
	248	CHILD_STACK is used as stack space for the cloned child. If NULL,
	249	stack space is allocated via malloc (and subsequently passed to
	250	FUNCTION). For MMU targets, CHILD_STACK is ignored. */
	251
	252	static int
ba4dd7c4	253	linux_fork_to_function (gdb_byte child_stack, int (function) (void *))
96d7229d LM	254	{
	255	int child_pid;
	256
	257	/* Sanity check the function pointer. */
	258	gdb_assert (function != NULL);
	259
	260	#if defined(__UCLIBC__) && defined(HAS_NOMMU)
	261	#define STACK_SIZE 4096
	262
	263	if (child_stack == NULL)
ffce45d2	264	child_stack = (gdb_byte ) xmalloc (STACK_SIZE 4);
96d7229d LM	265
96d7229d LM	266	/* Use CLONE_VM instead of fork, to support uClinux (no MMU). */
101158d9	267	#ifdef __ia64__
96d7229d LM	268	child_pid = __clone2 (function, child_stack, STACK_SIZE,
96d7229d LM	269	CLONE_VM \| SIGCHLD, child_stack + STACK_SIZE * 2);
101158d9	270	#else /* !__ia64__ */
96d7229d LM	271	child_pid = clone (function, child_stack + STACK_SIZE,
96d7229d LM	272	CLONE_VM \| SIGCHLD, child_stack + STACK_SIZE * 2);
101158d9	273	#endif /* !__ia64__ */
96d7229d LM	274	#else /* !defined(__UCLIBC) && defined(HAS_NOMMU) */
	275	child_pid = fork ();
	276
	277	if (child_pid == 0)
	278	function (NULL);
	279	#endif /* defined(__UCLIBC) && defined(HAS_NOMMU) */
	280
	281	if (child_pid == -1)
	282	perror_with_name (("fork"));
	283
	284	return child_pid;
	285	}
	286
	287	/* A helper function for linux_check_ptrace_features, called after
	288	the child forks a grandchild. */
	289
ba4dd7c4 YQ	290	static int
ba4dd7c4 YQ	291	linux_grandchild_function (void *child_stack)
96d7229d LM	292	{
	293	/* Free any allocated stack. */
	294	xfree (child_stack);
	295
	296	/* This code is only reacheable by the grandchild (child's child)
	297	process. */
	298	_exit (0);
	299	}
	300
	301	/* A helper function for linux_check_ptrace_features, called after
	302	the parent process forks a child. The child allows itself to
	303	be traced by its parent. */
	304
ba4dd7c4 YQ	305	static int
ba4dd7c4 YQ	306	linux_child_function (void *child_stack)
96d7229d LM	307	{
	308	ptrace (PTRACE_TRACEME, 0, (PTRACE_TYPE_ARG3) 0, (PTRACE_TYPE_ARG4) 0);
	309	kill (getpid (), SIGSTOP);
	310
	311	/* Fork a grandchild. */
d18547d8	312	linux_fork_to_function ((gdb_byte *) child_stack, linux_grandchild_function);
96d7229d LM	313
	314	/* This code is only reacheable by the child (grandchild's parent)
	315	process. */
	316	_exit (0);
	317	}
	318
8ae377e8 PA	319	static void linux_test_for_tracesysgood (int child_pid);
8ae377e8 PA	320	static void linux_test_for_tracefork (int child_pid);
beed38b8	321	static void linux_test_for_exitkill (int child_pid);
8ae377e8	322
96d7229d LM	323	/* Determine ptrace features available on this target. */
96d7229d LM	324
89245bc0	325	void
96d7229d LM	326	linux_check_ptrace_features (void)
	327	{
	328	int child_pid, ret, status;
96d7229d LM	329
96d7229d LM	330	/* Initialize the options. */
de0d863e	331	supported_ptrace_options = 0;
96d7229d LM	332
	333	/* Fork a child so we can do some testing. The child will call
	334	linux_child_function and will get traced. The child will
	335	eventually fork a grandchild so we can test fork event
	336	reporting. */
	337	child_pid = linux_fork_to_function (NULL, linux_child_function);
	338
	339	ret = my_waitpid (child_pid, &status, 0);
	340	if (ret == -1)
	341	perror_with_name (("waitpid"));
	342	else if (ret != child_pid)
	343	error (_("linux_check_ptrace_features: waitpid: unexpected result %d."),
	344	ret);
	345	if (! WIFSTOPPED (status))
	346	error (_("linux_check_ptrace_features: waitpid: unexpected status %d."),
	347	status);
	348
8ae377e8	349	linux_test_for_tracesysgood (child_pid);
96d7229d	350
8ae377e8 PA	351	linux_test_for_tracefork (child_pid);
8ae377e8 PA	352
beed38b8 JB	353	linux_test_for_exitkill (child_pid);
beed38b8 JB	354
8ae377e8 PA	355	/* Clean things up and kill any pending children. */
8ae377e8 PA	356	do
96d7229d LM	357	{
	358	ret = ptrace (PTRACE_KILL, child_pid, (PTRACE_TYPE_ARG3) 0,
	359	(PTRACE_TYPE_ARG4) 0);
	360	if (ret != 0)
8ae377e8 PA	361	warning (_("linux_check_ptrace_features: failed to kill child"));
8ae377e8 PA	362	my_waitpid (child_pid, &status, 0);
96d7229d	363	}
8ae377e8 PA	364	while (WIFSTOPPED (status));
8ae377e8 PA	365	}
96d7229d	366
8ae377e8 PA	367	/* Determine if PTRACE_O_TRACESYSGOOD can be used to catch
	368	syscalls. */
	369
	370	static void
	371	linux_test_for_tracesysgood (int child_pid)
	372	{
8ae377e8 PA	373	int ret;
8ae377e8 PA	374
96d7229d LM	375	ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
96d7229d LM	376	(PTRACE_TYPE_ARG4) PTRACE_O_TRACESYSGOOD);
8009206a	377
96d7229d	378	if (ret == 0)
de0d863e	379	supported_ptrace_options \|= PTRACE_O_TRACESYSGOOD;
8ae377e8	380	}
96d7229d	381
8ae377e8 PA	382	/* Determine if PTRACE_O_TRACEFORK can be used to follow fork
	383	events. */
	384
	385	static void
	386	linux_test_for_tracefork (int child_pid)
	387	{
	388	int ret, status;
	389	long second_pid;
	390
	391	/* First, set the PTRACE_O_TRACEFORK option. If this fails, we
	392	know for sure that it is not supported. */
	393	ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
	394	(PTRACE_TYPE_ARG4) PTRACE_O_TRACEFORK);
	395
	396	if (ret != 0)
	397	return;
	398
de0d863e DB	399	/* Check if the target supports PTRACE_O_TRACEVFORKDONE. */
	400	ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
	401	(PTRACE_TYPE_ARG4) (PTRACE_O_TRACEFORK
	402	\| PTRACE_O_TRACEVFORKDONE));
	403	if (ret == 0)
	404	supported_ptrace_options \|= PTRACE_O_TRACEVFORKDONE;
96d7229d LM	405
	406	/* Setting PTRACE_O_TRACEFORK did not cause an error, however we
	407	don't know for sure that the feature is available; old
	408	versions of PTRACE_SETOPTIONS ignored unknown options.
	409	Therefore, we attach to the child process, use PTRACE_SETOPTIONS
	410	to enable fork tracing, and let it fork. If the process exits,
	411	we assume that we can't use PTRACE_O_TRACEFORK; if we get the
	412	fork notification, and we can extract the new child's PID, then
	413	we assume that we can.
	414
	415	We do not explicitly check for vfork tracing here. It is
	416	assumed that vfork tracing is available whenever fork tracing
	417	is available. */
	418	ret = ptrace (PTRACE_CONT, child_pid, (PTRACE_TYPE_ARG3) 0,
	419	(PTRACE_TYPE_ARG4) 0);
	420	if (ret != 0)
8ae377e8	421	warning (_("linux_test_for_tracefork: failed to resume child"));
96d7229d LM	422
	423	ret = my_waitpid (child_pid, &status, 0);
	424
	425	/* Check if we received a fork event notification. */
	426	if (ret == child_pid && WIFSTOPPED (status)
89a5711c	427	&& linux_ptrace_get_extended_event (status) == PTRACE_EVENT_FORK)
96d7229d LM	428	{
	429	/* We did receive a fork event notification. Make sure its PID
	430	is reported. */
	431	second_pid = 0;
	432	ret = ptrace (PTRACE_GETEVENTMSG, child_pid, (PTRACE_TYPE_ARG3) 0,
	433	(PTRACE_TYPE_ARG4) &second_pid);
	434	if (ret == 0 && second_pid != 0)
	435	{
	436	int second_status;
	437
	438	/* We got the PID from the grandchild, which means fork
	439	tracing is supported. */
de0d863e DB	440	supported_ptrace_options \|= PTRACE_O_TRACECLONE;
	441	supported_ptrace_options \|= (PTRACE_O_TRACEFORK
	442	\| PTRACE_O_TRACEVFORK
	443	\| PTRACE_O_TRACEEXEC);
96d7229d LM	444
	445	/* Do some cleanup and kill the grandchild. */
	446	my_waitpid (second_pid, &second_status, 0);
	447	ret = ptrace (PTRACE_KILL, second_pid, (PTRACE_TYPE_ARG3) 0,
	448	(PTRACE_TYPE_ARG4) 0);
	449	if (ret != 0)
8ae377e8	450	warning (_("linux_test_for_tracefork: "
96d7229d LM	451	"failed to kill second child"));
	452	my_waitpid (second_pid, &status, 0);
	453	}
	454	}
	455	else
8ae377e8	456	warning (_("linux_test_for_tracefork: unexpected result from waitpid "
96d7229d	457	"(%d, status 0x%x)"), ret, status);
96d7229d LM	458	}
96d7229d LM	459
beed38b8 JB	460	/* Determine if PTRACE_O_EXITKILL can be used. */
	461
	462	static void
	463	linux_test_for_exitkill (int child_pid)
	464	{
	465	int ret;
	466
	467	ret = ptrace (PTRACE_SETOPTIONS, child_pid, (PTRACE_TYPE_ARG3) 0,
	468	(PTRACE_TYPE_ARG4) PTRACE_O_EXITKILL);
	469
	470	if (ret == 0)
de0d863e	471	supported_ptrace_options \|= PTRACE_O_EXITKILL;
beed38b8 JB	472	}
	473
	474	/* Enable reporting of all currently supported ptrace events.
de0d863e DB	475	OPTIONS is a bit mask of extended features we want enabled,
	476	if supported by the kernel. PTRACE_O_TRACECLONE is always
	477	enabled, if supported. */
96d7229d LM	478
96d7229d LM	479	void
de0d863e	480	linux_enable_event_reporting (pid_t pid, int options)
96d7229d LM	481	{
	482	/* Check if we have initialized the ptrace features for this
	483	target. If not, do it now. */
de0d863e	484	if (supported_ptrace_options == -1)
96d7229d LM	485	linux_check_ptrace_features ();
96d7229d LM	486
de0d863e DB	487	/* We always want clone events. */
	488	options \|= PTRACE_O_TRACECLONE;
	489
	490	/* Filter out unsupported options. */
	491	options &= supported_ptrace_options;
beed38b8	492
96d7229d LM	493	/* Set the options. */
96d7229d LM	494	ptrace (PTRACE_SETOPTIONS, pid, (PTRACE_TYPE_ARG3) 0,
de0d863e	495	(PTRACE_TYPE_ARG4) (uintptr_t) options);
96d7229d LM	496	}
96d7229d LM	497
c077881a HZ	498	/* Disable reporting of all currently supported ptrace events. */
	499
	500	void
	501	linux_disable_event_reporting (pid_t pid)
	502	{
	503	/* Set the options. */
	504	ptrace (PTRACE_SETOPTIONS, pid, (PTRACE_TYPE_ARG3) 0, 0);
	505	}
	506
96d7229d	507	/* Returns non-zero if PTRACE_OPTIONS is contained within
de0d863e	508	SUPPORTED_PTRACE_OPTIONS, therefore supported. Returns 0
96d7229d LM	509	otherwise. */
	510
	511	static int
	512	ptrace_supports_feature (int ptrace_options)
	513	{
de0d863e	514	if (supported_ptrace_options == -1)
8784d563	515	linux_check_ptrace_features ();
96d7229d	516
de0d863e	517	return ((supported_ptrace_options & ptrace_options) == ptrace_options);
96d7229d LM	518	}
	519
	520	/* Returns non-zero if PTRACE_EVENT_FORK is supported by ptrace,
	521	0 otherwise. Note that if PTRACE_EVENT_FORK is supported so is
	522	PTRACE_EVENT_CLONE, PTRACE_EVENT_EXEC and PTRACE_EVENT_VFORK,
	523	since they were all added to the kernel at the same time. */
	524
	525	int
	526	linux_supports_tracefork (void)
	527	{
	528	return ptrace_supports_feature (PTRACE_O_TRACEFORK);
	529	}
	530
94585166 DB	531	/* Returns non-zero if PTRACE_EVENT_EXEC is supported by ptrace,
	532	0 otherwise. Note that if PTRACE_EVENT_FORK is supported so is
	533	PTRACE_EVENT_CLONE, PTRACE_EVENT_FORK and PTRACE_EVENT_VFORK,
	534	since they were all added to the kernel at the same time. */
	535
	536	int
	537	linux_supports_traceexec (void)
	538	{
	539	return ptrace_supports_feature (PTRACE_O_TRACEEXEC);
	540	}
	541
96d7229d LM	542	/* Returns non-zero if PTRACE_EVENT_CLONE is supported by ptrace,
	543	0 otherwise. Note that if PTRACE_EVENT_CLONE is supported so is
	544	PTRACE_EVENT_FORK, PTRACE_EVENT_EXEC and PTRACE_EVENT_VFORK,
	545	since they were all added to the kernel at the same time. */
	546
	547	int
	548	linux_supports_traceclone (void)
	549	{
	550	return ptrace_supports_feature (PTRACE_O_TRACECLONE);
	551	}
	552
	553	/* Returns non-zero if PTRACE_O_TRACEVFORKDONE is supported by
	554	ptrace, 0 otherwise. */
	555
	556	int
	557	linux_supports_tracevforkdone (void)
	558	{
	559	return ptrace_supports_feature (PTRACE_O_TRACEVFORKDONE);
	560	}
	561
	562	/* Returns non-zero if PTRACE_O_TRACESYSGOOD is supported by ptrace,
	563	0 otherwise. */
	564
	565	int
	566	linux_supports_tracesysgood (void)
	567	{
	568	return ptrace_supports_feature (PTRACE_O_TRACESYSGOOD);
	569	}
	570
aa7c7447 JK	571	/* Display possible problems on this system. Display them only once per GDB
	572	execution. */
	573
	574	void
	575	linux_ptrace_init_warnings (void)
	576	{
	577	static int warned = 0;
	578
	579	if (warned)
	580	return;
	581	warned = 1;
	582
	583	linux_ptrace_test_ret_to_nx ();
	584	}
8009206a	585
89a5711c DB	586	/* Extract extended ptrace event from wait status. */
	587
	588	int
	589	linux_ptrace_get_extended_event (int wstat)
	590	{
	591	return (wstat >> 16);
	592	}
	593
	594	/* Determine whether wait status denotes an extended event. */
	595
	596	int
	597	linux_is_extended_waitstatus (int wstat)
	598	{
	599	return (linux_ptrace_get_extended_event (wstat) != 0);
	600	}
c9587f88 AT	601
	602	/* Return true if the event in LP may be caused by breakpoint. */
	603
	604	int
	605	linux_wstatus_maybe_breakpoint (int wstat)
	606	{
	607	return (WIFSTOPPED (wstat)
	608	&& (WSTOPSIG (wstat) == SIGTRAP
	609	/* SIGILL and SIGSEGV are also treated as traps in case a
	610	breakpoint is inserted at the current PC. */
	611	\|\| WSTOPSIG (wstat) == SIGILL
	612	\|\| WSTOPSIG (wstat) == SIGSEGV));
	613	}