gdb/

* common/linux-ptrace.c: Include gdb_assert.h.
	<__i386__> (linux_ptrace_test_ret_to_nx_instr): New declaration.
	<__i386__>: Include sys/reg.h, sys/mman.h, signal.h, sys/wait.h and
	stdint.h.
	(linux_ptrace_test_ret_to_nx, linux_ptrace_init_warnings): New
	functions.
	* common/linux-ptrace.h (linux_ptrace_init_warnings): New declarations.
	* linux-nat.c (linux_child_post_attach)
	(linux_child_post_startup_inferior): Call linux_ptrace_init_warnings.

gdb/gdbserver/
	* gdbserver/linux-low.c (initialize_low): Call
	linux_ptrace_init_warnings.

gdb/ChangeLog

@@ -1,3 +1,15 @@
+2012-07-07  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	* common/linux-ptrace.c: Include gdb_assert.h.
+	<__i386__> (linux_ptrace_test_ret_to_nx_instr): New declaration.
+	<__i386__>: Include sys/reg.h, sys/mman.h, signal.h, sys/wait.h and
+	stdint.h.
+	(linux_ptrace_test_ret_to_nx, linux_ptrace_init_warnings): New
+	functions.
+	* common/linux-ptrace.h (linux_ptrace_init_warnings): New declarations.
+	* linux-nat.c (linux_child_post_attach)
+	(linux_child_post_startup_inferior): Call linux_ptrace_init_warnings.
+
 2012-07-07  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	* linux-thread-db.c (thread_db_find_new_threads_silently): Do not apply

gdb/common/linux-ptrace.c

@@ -26,6 +26,7 @@
 #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
@@ -47,3 +48,126 @@ linux_ptrace_attach_warnings (pid_t pid, struct buffer *buffer)
 				 "- the process has already terminated\n"),
 		       (int) pid);
 }
+
+#ifdef __i386__
+
+/* 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 /* __i386__ */
+
+/* Test broken off-trunk Linux kernel patchset for NX support on i386.  It was
+   removed in Fedora kernel 88fa1f0332d188795ed73d7ac2b1564e11a0b4cd.  */
+
+static void
+linux_ptrace_test_ret_to_nx (void)
+{
+#ifdef __i386__
+  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
+	{
+	  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");
+	  gdb_assert_not_reached ("asm block did not terminate");
+	}
+
+      _exit (1);
+    }
+
+  got_pid = waitpid (child, &status, 0);
+  gdb_assert (got_pid == child);
+  gdb_assert (WIFSTOPPED (status));
+
+  /* We may get SIGSEGV due to missing PROT_EXEC of the return_address.  */
+  gdb_assert (WSTOPSIG (status) == SIGTRAP || WSTOPSIG (status) == SIGSEGV);
+
+  errno = 0;
+  l = ptrace (PTRACE_PEEKUSER, child, (void *) (uintptr_t) (EIP * 4), NULL);
+  gdb_assert (errno == 0);
+  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));
+  else
+    {
+      int kill_status;
+
+      got_pid = waitpid (child, &kill_status, 0);
+      gdb_assert (got_pid == child);
+      gdb_assert (WIFSIGNALED (kill_status));
+    }
+
+  /* + 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;
+    }
+
+  gdb_assert ((void (*) (void)) pc == &linux_ptrace_test_ret_to_nx_instr);
+
+  warning (_("Cannot call inferior functions, you have broken "
+	     "Linux kernel i386 NX (non-executable pages) support!"));
+#endif /* __i386__ */
+}
+
+/* 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 ();
+}

gdb/common/linux-ptrace.h

@@ -68,5 +68,6 @@ struct buffer;
 #endif
 
 extern void linux_ptrace_attach_warnings (pid_t pid, struct buffer *buffer);
+extern void linux_ptrace_init_warnings (void);
 
 #endif /* COMMON_LINUX_PTRACE_H */

gdb/gdbserver/ChangeLog

@@ -1,3 +1,8 @@
+2012-07-07  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	* gdbserver/linux-low.c (initialize_low): Call
+	linux_ptrace_init_warnings.
+
 2012-07-02  Doug Evans  <dje@google.com>
 
 	* mem-break.c (gdb_no_commands_at_breakpoint): Fix cast from

gdb/gdbserver/linux-low.c

@@ -5878,6 +5878,7 @@ initialize_low (void)
 		       the_low_target.breakpoint_len);
   linux_init_signals ();
   linux_test_for_tracefork ();
+  linux_ptrace_init_warnings ();
 #ifdef HAVE_LINUX_REGSETS
   for (num_regsets = 0; target_regsets[num_regsets].size >= 0; num_regsets++)
     ;

gdb/linux-nat.c

@@ -583,6 +583,7 @@ linux_child_post_attach (int pid)
 {
   linux_enable_event_reporting (pid_to_ptid (pid));
   linux_enable_tracesysgood (pid_to_ptid (pid));
+  linux_ptrace_init_warnings ();
 }
 
 static void
@@ -590,6 +591,7 @@ linux_child_post_startup_inferior (ptid_t ptid)
 {
   linux_enable_event_reporting (ptid);
   linux_enable_tracesysgood (ptid);
+  linux_ptrace_init_warnings ();
 }
 
 /* Return the number of known LWPs in the tgid given by PID.  */