[PATCH v2] Fix logic in exec_file_locate_attach

[Gary Benson <gbenson@redhat.com>]

Hi all,

This is an updated version of the patch I posted yesterday.
It fails silently rather than throwing if the executable is
not in the sysroot, which both fixes the sysroot-escape issue
and results in a better GDB session for the user.

Built and regtested on RHEL 6.6 x86_64.

Luis, I think this patch will fix your connection drop without
any further changes.  Could you test it please?

Thanks,
Gary

---
This commit fixes an error in exec_file_locate_attach where
the main executable could be loaded from outside the sysroot
if a nonempty, non-"target:" sysroot was set but the discovered
executable filename did not exist in that sysroot and did exist
on the main filesystem.

gdb/ChangeLog:

	* exec.c (exec_file_locate_attach): Do not attempt to
	locate main executable locally if not found in sysroot.

gdb/testsuite/ChangeLog:

	* gdb.base/attach-pie-noexec.exp: Do not expect an error
	message on attach.
---
 gdb/ChangeLog                                |    5 +++++
 gdb/exec.c                                   |    9 ++++++---
 gdb/testsuite/ChangeLog                      |    5 +++++
 gdb/testsuite/gdb.base/attach-pie-noexec.exp |    2 +-
 4 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/gdb/exec.c b/gdb/exec.c
index 0b8c077..90811c0 100644
--- a/gdb/exec.c
+++ b/gdb/exec.c
@@ -156,9 +156,12 @@ exec_file_locate_attach (int pid, int from_tty)
   /* If gdb_sysroot is not empty and the discovered filename
      is absolute then prefix the filename with gdb_sysroot.  */
   if (*gdb_sysroot != '\0' && IS_ABSOLUTE_PATH (exec_file))
-    full_exec_path = exec_file_find (exec_file, NULL);
-
-  if (full_exec_path == NULL)
+    {
+      full_exec_path = exec_file_find (exec_file, NULL);
+      if (full_exec_path == NULL)
+	return;
+    }
+  else
     {
       /* It's possible we don't have a full path, but rather just a
 	 filename.  Some targets, such as HP-UX, don't provide the
diff --git a/gdb/testsuite/gdb.base/attach-pie-noexec.exp b/gdb/testsuite/gdb.base/attach-pie-noexec.exp
index f3e693a..1a51049 100644
--- a/gdb/testsuite/gdb.base/attach-pie-noexec.exp
+++ b/gdb/testsuite/gdb.base/attach-pie-noexec.exp
@@ -60,7 +60,7 @@ set testpid [spawn_id_get_pid $test_spawn_id]
 
 gdb_start
 file delete -- $binfile
-gdb_test "attach $testpid" "Attaching to process $testpid\r\n.*: No such file or directory\\." "attach"
+gdb_test "attach $testpid" "Attaching to process $testpid\r\n.*" "attach"
 gdb_test "set architecture $arch" "The target architecture is assumed to be $arch"
 gdb_test "info shared" "From\[ \t\]+To\[ \t\]+Syms Read\[ \t\]+Shared Object Library\r\n0x.*"
 
-- 
1.7.1