[PATCH] btrace: do not return out of TRY/CATCH

[PATCH] btrace: do not return out of TRY/CATCH

[Markus Metzger]

In btrace_pt_readmem_callback, we read memory inside TRY/CATCH and return in
case of an error return value.  This corrupts the cleanup chain, which
eventually results in a SEGV when doing or discarding cleanups later on.

2015-12-23  Markus Metzger  <markus.t.metzger@intel.com>

gdb/
	* btrace.c (btrace_pt_readmem_callback): Do not return in TRY/CATCH.

testsuite/
	* gdb.btrace/dlopen.exp: New.
	* gdb.btrace/dlopen.c: New.
	* gdb.btrace/dlopen-dso.c: New.
---
 gdb/btrace.c                          |  9 +++---
 gdb/testsuite/gdb.btrace/dlopen-dso.c | 22 +++++++++++++++
 gdb/testsuite/gdb.btrace/dlopen.c     | 50 +++++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.btrace/dlopen.exp   | 52 +++++++++++++++++++++++++++++++++++
 4 files changed, 129 insertions(+), 4 deletions(-)
 create mode 100644 gdb/testsuite/gdb.btrace/dlopen-dso.c
 create mode 100644 gdb/testsuite/gdb.btrace/dlopen.c
 create mode 100644 gdb/testsuite/gdb.btrace/dlopen.exp

diff --git a/gdb/btrace.c b/gdb/btrace.c
index 35431cb..152daa7 100644
--- a/gdb/btrace.c
+++ b/gdb/btrace.c
@@ -842,21 +842,22 @@ btrace_pt_readmem_callback (gdb_byte *buffer, size_t size,
 			    const struct pt_asid *asid, uint64_t pc,
 			    void *context)
 {
-  int errcode;
+  int result, errcode;
 
+  result = (int) size;
   TRY
     {
       errcode = target_read_code ((CORE_ADDR) pc, buffer, size);
       if (errcode != 0)
-	return -pte_nomap;
+	result = -pte_nomap;
     }
   CATCH (error, RETURN_MASK_ERROR)
     {
-      return -pte_nomap;
+      result = -pte_nomap;
     }
   END_CATCH
 
-  return size;
+  return result;
 }
 
 /* Translate the vendor from one enum to another.  */
diff --git a/gdb/testsuite/gdb.btrace/dlopen-dso.c b/gdb/testsuite/gdb.btrace/dlopen-dso.c
new file mode 100644
index 0000000..1ea7657
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/dlopen-dso.c
@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int
+answer (void)
+{
+  return 42;
+}
diff --git a/gdb/testsuite/gdb.btrace/dlopen.c b/gdb/testsuite/gdb.btrace/dlopen.c
new file mode 100644
index 0000000..70df604
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/dlopen.c
@@ -0,0 +1,50 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <assert.h>
+#include <stdlib.h>
+
+static int
+test (void)
+{
+  void *dso;
+  int (*fun) (void);
+  int answer;
+
+  dso = dlopen (DSO_NAME, RTLD_NOW | RTLD_GLOBAL);
+  assert (dso != NULL);
+
+  fun = (int (*) (void)) dlsym (dso, "answer");
+  assert (fun != NULL);
+
+  answer = fun ();
+
+  dlclose (dso);
+
+  return answer;
+}
+
+int
+main (void)
+{
+  int answer;
+
+  answer = test ();
+
+  return answer;
+}
diff --git a/gdb/testsuite/gdb.btrace/dlopen.exp b/gdb/testsuite/gdb.btrace/dlopen.exp
new file mode 100644
index 0000000..48368ae
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/dlopen.exp
@@ -0,0 +1,52 @@
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2015 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if { [skip_btrace_tests] } { return -1 }
+if { [skip_shlib_tests]  } { return -1 }
+
+standard_testfile
+
+set basename_lib dlopen-dso
+set srcfile_lib $srcdir/$subdir/$basename_lib.c
+set binfile_lib [standard_output_file $basename_lib.so]
+
+if { [gdb_compile_shlib $srcfile_lib $binfile_lib \
+	  [list additional_flags=-fPIC]] != "" } {
+    untested "Could not compile $binfile_lib."
+    return -1
+}
+
+if { [prepare_for_testing $testfile.exp $testfile $srcfile \
+	  [list additional_flags=-DDSO_NAME=\"$binfile_lib\" libs=-ldl]] } {
+    return -1
+}
+
+if ![runto_main] {
+    return 0
+}
+
+# Trace the test function
+#
+gdb_test_no_output "record btrace"
+gdb_test "next"
+
+# The memory containing the library call we traced is already gone.
+# Trace decode used to run into a SEGV after corrupting the cleanup chain.
+#
+# The test passes if we don't crash GDB.
+#
+gdb_test "info record"
-- 
1.8.3.1

Re: [PATCH] btrace: do not return out of TRY/CATCH

[Joel Brobecker]

> 2015-12-23  Markus Metzger  <markus.t.metzger@intel.com>
> 
> gdb/
> 	* btrace.c (btrace_pt_readmem_callback): Do not return in TRY/CATCH.
> 
> testsuite/
> 	* gdb.btrace/dlopen.exp: New.
> 	* gdb.btrace/dlopen.c: New.
> 	* gdb.btrace/dlopen-dso.c: New.

Looks good to me (and I verified that the TRY/CATCH documentation
mentions that we should not goto or return out of it).

Thanks!
-- 
Joel