-/*
- * mono-signal-handler.h: Handle signal handler differences across platforms
+/**
+ * \file
+ * Handle signal handler differences across platforms
*
* Copyright (C) 2013 Xamarin Inc
+ * Licensed under the MIT license. See LICENSE file in the project root for full license information.
*/
#ifndef __MONO_SIGNAL_HANDLER_H__
#include "config.h"
-#ifdef ENABLE_EXTENSION_MODULE
-#include "../../../mono-extensions/mono/utils/mono-signal-handler.h"
+/*
+ * When a signal is delivered to a thread on a Krait Android device
+ * that's in the middle of skipping over an "IT" block, such as this
+ * one:
+ *
+ * 0x40184ef0 <dlfree+1308>: ldr r1, [r3, #0]
+ * 0x40184ef2 <dlfree+1310>: add.w r5, r12, r2, lsl #3
+ * 0x40184ef6 <dlfree+1314>: lsls.w r2, r0, r2
+ * 0x40184efa <dlfree+1318>: tst r2, r1
+ * ### this is the IT instruction
+ * 0x40184efc <dlfree+1320>: itt eq
+ * 0x40184efe <dlfree+1322>: orreq r2, r1
+ * ### signal arrives here
+ * 0x40184f00 <dlfree+1324>: streq r2, [r3, #0]
+ * 0x40184f02 <dlfree+1326>: beq.n 0x40184f1a <dlfree+1350>
+ * 0x40184f04 <dlfree+1328>: ldr r2, [r5, #8]
+ * 0x40184f06 <dlfree+1330>: ldr r3, [r3, #16]
+ *
+ * then the first few (at most four, one would assume) instructions of
+ * the signal handler (!) might be skipped. They happen to be the
+ * push of the frame pointer and return address, so once the signal
+ * handler has done its work, it returns into a SIGSEGV.
+ */
+
+#if defined (TARGET_ARM) && defined (HAVE_ARMV7) && defined (TARGET_ANDROID)
+#define KRAIT_IT_BUG_WORKAROUND 1
+#endif
+
+#ifdef KRAIT_IT_BUG_WORKAROUND
+#define MONO_SIGNAL_HANDLER_FUNC(access, name, arglist) \
+ static void __krait_ ## name arglist; \
+ __attribute__ ((__naked__)) access void \
+ name arglist \
+ { \
+ asm volatile ( \
+ "mov r0, r0\n\t" \
+ "mov r0, r0\n\t" \
+ "mov r0, r0\n\t" \
+ "mov r0, r0\n\t" \
+ "b __krait_" # name \
+ "\n\t"); \
+ } \
+ static __attribute__ ((__used__)) void __krait_ ## name arglist
#endif
/* Don't use this */