Merge GDB 7.5.1

gdb/common/linux-ptrace.c

+/* Linux-specific ptrace manipulation routines.
+   Copyright (C) 2012 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/>.  */
+
+#ifdef GDBSERVER
+#include "server.h"
+#else
+#include "defs.h"
+#include "gdb_string.h"
+#endif
+
+#include "linux-ptrace.h"
+#include "linux-procfs.h"
+#include "buffer.h"
+#include "gdb_assert.h"
+
+/* Find all possible reasons we could fail to attach PID and append these
+   newline terminated reason strings to initialized BUFFER.  '\0' termination
+   of BUFFER must be done by the caller.  */
+
+void
+linux_ptrace_attach_warnings (pid_t pid, struct buffer *buffer)
+{
+  pid_t tracerpid;
+
+  tracerpid = linux_proc_get_tracerpid (pid);
+  if (tracerpid > 0)
+    buffer_xml_printf (buffer, _("warning: process %d is already traced "
+                                 "by process %d\n"),
+                       (int) pid, (int) tracerpid);
+
+  if (linux_proc_pid_is_zombie (pid))
+    buffer_xml_printf (buffer, _("warning: process %d is a zombie "
+                                 "- the process has already terminated\n"),
+                       (int) pid);
+}
+
+#if defined __i386__ || defined __x86_64__
+
+/* Address of the 'ret' instruction in asm code block below.  */
+extern void (linux_ptrace_test_ret_to_nx_instr) (void);
+
+#include <sys/reg.h>
+#include <sys/mman.h>
+#include <signal.h>
+#include <sys/wait.h>
+#include <stdint.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;
+
+  return_address = 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"),
+               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"),
+               strerror (errno));
+      return;
+
+    case 0:
+      l = ptrace (PTRACE_TRACEME, 0, NULL, NULL);
+      if (l != 0)
+        warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_TRACEME: %s"),
+                 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" (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, 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;
+    }
+
+  errno = 0;
+#if defined __i386__
+  l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (EIP * 4), NULL);
+#elif defined __x86_64__
+  l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (RIP * 8), NULL);
+#else
+# error "!__i386__ && !__x86_64__"
+#endif
+  if (errno != 0)
+    {
+      warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_PEEKUSER: %s"),
+               strerror (errno));
+      return;
+    }
+  pc = (void *) (uintptr_t) l;
+
+  if (ptrace (PTRACE_KILL, child, NULL, NULL) != 0)
+    {
+      warning (_("linux_ptrace_test_ret_to_nx: Cannot PTRACE_KILL: %s"),
+               strerror (errno));
+      return;
+    }
+  else
+    {
+      int kill_status;
+
+      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, 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, you have broken "
+               "Linux kernel i386 NX (non-executable pages) support!"));
+#endif /* defined __i386__ || defined __x86_64__ */
+}
+
+/* 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 ();
+}