gdb/

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

diff --git a/gdb/common/linux-ptrace.c b/gdb/common/linux-ptrace.c
index 600dcb9d77efd970e69d9d812617da37ddb75567..fdec5d6291c13b329ea921a0321e3cecf6dcb9cb 100644 (file)
--- a/gdb/common/linux-ptrace.c
+++ b/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 ();
+}