linux-nat: Exploit /proc/<pid>/mem for writing

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

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 5d5efa0af45fa8c36b143d6cc8b812f06c64e568..73ef2d49473e9d1761e8391bd7acfeeb1a15cc02 100644 (file)
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -1,6 +1,6 @@
 /* GNU/Linux native-dependent code common to multiple platforms.
 
-   Copyright (C) 2001-2016 Free Software Foundation, Inc.
+   Copyright (C) 2001-2017 Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -355,6 +355,14 @@ lwp_stop_reason (struct lwp_info *lwp)
   return lwp->stop_reason;
 }
 
+/* See nat/linux-nat.h.  */
+
+int
+lwp_is_stepping (struct lwp_info *lwp)
+{
+  return lwp->step;
+}
+
 \f
 /* Trivial list manipulation functions to keep track of a list of
    new stopped processes.  */
@@ -1245,7 +1253,7 @@ linux_nat_attach (struct target_ops *ops, const char *args, int from_tty)
          int exit_code = WEXITSTATUS (status);
 
          target_terminal_ours ();
-         target_mourn_inferior ();
+         target_mourn_inferior (inferior_ptid);
          if (exit_code == 0)
            error (_("Unable to attach: program exited normally."));
          else
@@ -1257,7 +1265,7 @@ linux_nat_attach (struct target_ops *ops, const char *args, int from_tty)
          enum gdb_signal signo;
 
          target_terminal_ours ();
-         target_mourn_inferior ();
+         target_mourn_inferior (inferior_ptid);
 
          signo = gdb_signal_from_host (WTERMSIG (status));
          error (_("Unable to attach: program terminated with signal "
@@ -3776,7 +3784,7 @@ linux_nat_kill (struct target_ops *ops)
       iterate_over_lwps (ptid, kill_wait_callback, NULL);
     }
 
-  target_mourn_inferior ();
+  target_mourn_inferior (inferior_ptid);
 }
 
 static void
@@ -3970,10 +3978,9 @@ linux_child_pid_to_exec_file (struct target_ops *self, int pid)
   return linux_proc_pid_to_exec_file (pid);
 }
 
-/* Implement the to_xfer_partial interface for memory reads using the /proc
-   filesystem.  Because we can use a single read() call for /proc, this
-   can be much more efficient than banging away at PTRACE_PEEKTEXT,
-   but it doesn't support writes.  */
+/* Implement the to_xfer_partial target method using /proc/<pid>/mem.
+   Because we can use a single read/write call, this can be much more
+   efficient than banging away at PTRACE_PEEKTEXT.  */
 
 static enum target_xfer_status
 linux_proc_xfer_partial (struct target_ops *ops, enum target_object object,
@@ -3985,7 +3992,7 @@ linux_proc_xfer_partial (struct target_ops *ops, enum target_object object,
   int fd;
   char filename[64];
 
-  if (object != TARGET_OBJECT_MEMORY || !readbuf)
+  if (object != TARGET_OBJECT_MEMORY)
     return TARGET_XFER_EOF;
 
   /* Don't bother for one word.  */
@@ -3996,26 +4003,27 @@ linux_proc_xfer_partial (struct target_ops *ops, enum target_object object,
      thread.  That requires some juggling, but is even faster.  */
   xsnprintf (filename, sizeof filename, "/proc/%d/mem",
             ptid_get_pid (inferior_ptid));
-  fd = gdb_open_cloexec (filename, O_RDONLY | O_LARGEFILE, 0);
+  fd = gdb_open_cloexec (filename, ((readbuf ? O_RDONLY : O_WRONLY)
+                                   | O_LARGEFILE), 0);
   if (fd == -1)
     return TARGET_XFER_EOF;
 
-  /* If pread64 is available, use it.  It's faster if the kernel
-     supports it (only one syscall), and it's 64-bit safe even on
-     32-bit platforms (for instance, SPARC debugging a SPARC64
-     application).  */
+  /* Use pread64/pwrite64 if available, since they save a syscall and can
+     handle 64-bit offsets even on 32-bit platforms (for instance, SPARC
+     debugging a SPARC64 application).  */
 #ifdef HAVE_PREAD64
-  if (pread64 (fd, readbuf, len, offset) != len)
+  ret = (readbuf ? pread64 (fd, readbuf, len, offset)
+        : pwrite64 (fd, writebuf, len, offset));
 #else
-  if (lseek (fd, offset, SEEK_SET) == -1 || read (fd, readbuf, len) != len)
+  ret = lseek (fd, offset, SEEK_SET);
+  if (ret != -1)
+    ret = (readbuf ? read (fd, readbuf, len)
+          : write (fd, writebuf, len));
 #endif
-    ret = 0;
-  else
-    ret = len;
 
   close (fd);
 
-  if (ret == 0)
+  if (ret == -1 || ret == 0)
     return TARGET_XFER_EOF;
   else
     {
@@ -4289,7 +4297,7 @@ cleanup_target_stop (void *arg)
   gdb_assert (arg != NULL);
 
   /* Unpause all */
-  target_resume (*ptid, 0, GDB_SIGNAL_0);
+  target_continue_no_signal (*ptid);
 }
 
 static VEC(static_tracepoint_marker_p) *
@@ -4409,9 +4417,8 @@ linux_nat_is_async_p (struct target_ops *ops)
 static int
 linux_nat_can_async_p (struct target_ops *ops)
 {
-  /* NOTE: palves 2008-03-21: We're only async when the user requests
-     it explicitly with the "set target-async" command.
-     Someday, linux will always be async.  */
+  /* We're always async, unless the user explicitly prevented it with the
+     "maint set target-async" command.  */
   return target_async_permitted;
 }