From: H.J. Lu <hongjiu.lu@intel.com>
Date: Thu, 19 Apr 2018 17:05:39 +0000 (+0000)
Subject: libgcc/CET: Skip signal frames when unwinding shadow stack
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=5707be3c7da6196efcef2d86e623771153eb6c7f;p=gcc.git

libgcc/CET: Skip signal frames when unwinding shadow stack

When -fcf-protection -mcet is used, I got

FAIL: g++.dg/eh/sighandle.C

(gdb) bt
 #0  _Unwind_RaiseException (exc=exc@entry=0x416ed0)
    at /export/gnu/import/git/sources/gcc/libgcc/unwind.inc:140
 #1  0x00007ffff7d9936b in __cxxabiv1::__cxa_throw (obj=<optimized out>,
    tinfo=0x403dd0 <typeinfo for int@@CXXABI_1.3>, dest=0x0)
    at /export/gnu/import/git/sources/gcc/libstdc++-v3/libsupc++/eh_throw.cc:90
 #2  0x0000000000401255 in sighandler (signo=11, si=0x7fffffffd6f8,
    uc=0x7fffffffd5c0)
    at /export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/eh/sighandle.C:9
 #3  <signal handler called> <<<< Signal frame which isn't on shadow stack
 #4  dosegv ()
    at /export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/eh/sighandle.C:14
 #5  0x00000000004012e3 in main ()
    at /export/gnu/import/git/sources/gcc/gcc/testsuite/g++.dg/eh/sighandle.C:30
(gdb) p frames
$6 = 5
(gdb)

frame count should be 4, not 5.  This patch skips signal frames when
unwinding shadow stack.

gcc/testsuite/

	PR libgcc/85334
	* g++.dg/torture/pr85334.C: New test.

libgcc/

	PR libgcc/85334
	* unwind-generic.h (_Unwind_Frames_Increment): New.
	* config/i386/shadow-stack-unwind.h (_Unwind_Frames_Increment):
	Likewise.
	* unwind.inc (_Unwind_RaiseException_Phase2): Increment frame
	count with _Unwind_Frames_Increment.
	(_Unwind_ForcedUnwind_Phase2): Likewise.

From-SVN: r259502
---

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 62dec374218..e7b9547c1a4 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-04-19  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR libgcc/85334
+	* g++.dg/torture/pr85334.C: New test.
+
 2018-04-19  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR c++/85464 - missing location for -Wignored-qualifiers diagnostic
diff --git a/gcc/testsuite/g++.dg/torture/pr85334.C b/gcc/testsuite/g++.dg/torture/pr85334.C
new file mode 100644
index 00000000000..080978143bd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr85334.C
@@ -0,0 +1,38 @@
+// { dg-do run { target { i?86-*-linux* i?86-*-gnu* x86_64-*-linux* } } }
+// { dg-require-effective-target cet }
+// { dg-additional-options "-fexceptions -fnon-call-exceptions -fcf-protection -mcet" }
+
+#include <signal.h>
+#include <stdlib.h>
+
+void sighandler (int signo, siginfo_t * si, void * uc)
+{
+  throw (5);
+}
+
+char * dosegv ()
+{    
+  * ((volatile int *)0) = 12;
+  return 0;
+}
+
+int main ()
+{
+  struct sigaction sa;
+  int status;
+
+  sa.sa_sigaction = sighandler;
+  sa.sa_flags = SA_SIGINFO;
+    
+  status = sigaction (SIGSEGV, & sa, NULL);
+  status = sigaction (SIGBUS, & sa, NULL);
+
+  try {
+    dosegv ();
+  }
+  catch (int x) {
+    return (x != 5);
+  }
+
+  return 1;
+}
diff --git a/libgcc/ChangeLog b/libgcc/ChangeLog
index 674d2041bd7..8a645c80e3d 100644
--- a/libgcc/ChangeLog
+++ b/libgcc/ChangeLog
@@ -1,3 +1,13 @@
+2018-04-19  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR libgcc/85334
+	* unwind-generic.h (_Unwind_Frames_Increment): New.
+	* config/i386/shadow-stack-unwind.h (_Unwind_Frames_Increment):
+	Likewise.
+	* unwind.inc (_Unwind_RaiseException_Phase2): Increment frame
+	count with _Unwind_Frames_Increment.
+	(_Unwind_ForcedUnwind_Phase2): Likewise.
+
 2018-04-19  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR libgcc/85379
diff --git a/libgcc/config/i386/shadow-stack-unwind.h b/libgcc/config/i386/shadow-stack-unwind.h
index 40f48df2aec..a32f3e74b52 100644
--- a/libgcc/config/i386/shadow-stack-unwind.h
+++ b/libgcc/config/i386/shadow-stack-unwind.h
@@ -49,3 +49,8 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 	}					\
     }						\
     while (0)
+
+/* Increment frame count.  Skip signal frames.  */
+#undef _Unwind_Frames_Increment
+#define _Unwind_Frames_Increment(context, frames) \
+  if (!_Unwind_IsSignalFrame (context)) frames++
diff --git a/libgcc/unwind-generic.h b/libgcc/unwind-generic.h
index b5e3568e1bc..639c96f438e 100644
--- a/libgcc/unwind-generic.h
+++ b/libgcc/unwind-generic.h
@@ -291,4 +291,7 @@ EXCEPTION_DISPOSITION _GCC_specific_handler (PEXCEPTION_RECORD, void *,
 /* Additional actions to unwind number of stack frames.  */
 #define _Unwind_Frames_Extra(frames)
 
+/* Increment frame count.  */
+#define _Unwind_Frames_Increment(context, frames) frames++
+
 #endif /* unwind.h */
diff --git a/libgcc/unwind.inc b/libgcc/unwind.inc
index 68c08964d30..19a8e4f6c80 100644
--- a/libgcc/unwind.inc
+++ b/libgcc/unwind.inc
@@ -73,7 +73,7 @@ _Unwind_RaiseException_Phase2(struct _Unwind_Exception *exc,
       gcc_assert (!match_handler);
 
       uw_update_context (context, &fs);
-      frames++;
+      _Unwind_Frames_Increment (context, frames);
     }
 
   *frames_p = frames;
@@ -190,7 +190,7 @@ _Unwind_ForcedUnwind_Phase2 (struct _Unwind_Exception *exc,
       /* Update cur_context to describe the same frame as fs, and discard
 	 the previous context if necessary.  */
       uw_advance_context (context, &fs);
-      frames++;
+      _Unwind_Frames_Increment (context, frames);
     }
 
   *frames_p = frames;