[PATCH 2/3] gdb: testsuite: add new gdb_attach to fix attach-pie-noexec.exp

[Tiezhu Yang <yangtiezhu@loongson.cn>]

This commit adds gdb_attach to check various output of "attach" command,
and then use gdb_attach to fix the following issue.

If /proc/sys/kernel/yama/ptrace_scope is 1, when execute the following
command without superuser:

  make check-gdb TESTS="gdb.base/attach-pie-noexec.exp"

we can see the following messages in gdb/testsuite/gdb.log:

  (gdb) attach 6500
  Attaching to process 6500
  ptrace: Operation not permitted.
  (gdb) PASS: gdb.base/attach-pie-noexec.exp: attach

It is obviously wrong, the expected result should be UNSUPPORTED in such
a case.

With this patch, we can see "Operation not permitted" in the log info,
and then we can do the following processes to test:
(1) set ptrace_scope as 0
    $ echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
    $ make check-gdb TESTS="gdb.base/attach-pie-noexec.exp"
(2) use sudo
    $ sudo make check-gdb TESTS="gdb.base/attach-pie-noexec.exp"

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 gdb/testsuite/gdb.base/attach-pie-noexec.exp |  4 +++-
 gdb/testsuite/lib/gdb.exp                    | 15 +++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/gdb.base/attach-pie-noexec.exp b/gdb/testsuite/gdb.base/attach-pie-noexec.exp
index 4712824..9a1bafe 100644
--- a/gdb/testsuite/gdb.base/attach-pie-noexec.exp
+++ b/gdb/testsuite/gdb.base/attach-pie-noexec.exp
@@ -59,7 +59,9 @@ set testpid [spawn_id_get_pid $test_spawn_id]
 
 gdb_start
 file delete -- $binfile
-gdb_test "attach $testpid" "Attaching to process $testpid\r\n.*" "attach"
+if {![gdb_attach $testpid]} {
+    return 0
+}
 gdb_test "set architecture $arch" "The target architecture is set to \"$arch\"\\."
 gdb_test "info shared" "From\[ \t\]+To\[ \t\]+Syms Read\[ \t\]+Shared Object Library\r\n0x.*"
 
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 8fafcc0..599e8cc 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -5102,6 +5102,21 @@ proc can_spawn_for_attach { } {
     return 1
 }
 
+# Check various output of "attach" command.
+
+proc gdb_attach { testpid } {
+    gdb_test_multiple "attach $testpid" "gdb attach" {
+	-re -wrap "Attaching to process $testpid\r\n.*No executable file now.*" {
+	  pass $gdb_test_name
+	  return 1
+	}
+	-re -wrap "Attaching to process $testpid\r\n.*ptrace: Operation not permitted\\." {
+	  unsupported "$gdb_test_name (Operation not permitted)"
+	  return 0
+	}
+    }
+}
+
 # Kill a progress previously started with spawn_wait_for_attach, and
 # reap its wait status.  PROC_SPAWN_ID is the spawn id associated with
 # the process.
-- 
2.1.0