Support for SJ/LJ unwinding (arm)

Author: vhbit

lib/builtins/gcc_personality_v0.c

@@ -180,7 +180,7 @@ static uintptr_t readEncodedPointer(const uint8_t** data, uint8_t encoding)
  * on each frame as the stack is unwound during a C++ exception
  * throw through a C function compiled with -fexceptions.
  */
-#if __arm__
+#if defined(__USING_SJLJ_EXCEPTIONS__)
 // the setjump-longjump based exceptions personality routine has a different name
 COMPILER_RT_ABI _Unwind_Reason_Code
 __gcc_personality_sj0(int version, _Unwind_Action actions,
@@ -216,34 +216,66 @@ __gcc_personality_v0(int version, _Unwind_Action actions,
     if (ttypeEncoding != DW_EH_PE_omit) {
         readULEB128(&lsda);  
     }
-    /* Walk call-site table looking for range that includes current PC. */
+
+    uintptr_t       resumeIp = 0;
     uint8_t         callSiteEncoding = *lsda++;
     uint32_t        callSiteTableLength = readULEB128(&lsda);
-    const uint8_t*  callSiteTableStart = lsda;
-    const uint8_t*  callSiteTableEnd = callSiteTableStart + callSiteTableLength;
-    const uint8_t* p=callSiteTableStart;
-    while (p < callSiteTableEnd) {
-        uintptr_t start = readEncodedPointer(&p, callSiteEncoding);
-        uintptr_t length = readEncodedPointer(&p, callSiteEncoding);
-        uintptr_t landingPad = readEncodedPointer(&p, callSiteEncoding);
-        readULEB128(&p); /* action value not used for C code */
+    const uint8_t*  callSite = lsda;
+
+#if defined(__USING_SJLJ_EXCEPTIONS__)
+    (void)callSiteEncoding;
+    (void)callSiteTableLength;    
+    /* The given "IP" is an index into the call-site table, with two
+    exceptions -- -1 means no-action, and 0 means terminate.  But
+    since we're using uleb128 values, we've not got random access
+    to the array.  */
+    if ((int) pc <= 0)
+        return _URC_CONTINUE_UNWIND;
+    else {
+        uintptr_t csLp;
+        do {
+            csLp = readULEB128(&callSite);
+            readULEB128(&callSite); // skip cs action
+        }
+        while (--pc);
+
+        /* Can never have null landing pad for sjlj -- that would have
+        been indicated by a -1 call site index.  */
+        resumeIp = csLp + 1;
+    }
+#else
+    /* Walk call-site table looking for range that includes current PC. */
+    uintptr_t       funcStart = _Unwind_GetRegionStart(context);
+    uintptr_t       pcOffset = pc - funcStart;
+    const uint8_t*  callSiteTableEnd = callSite + callSiteTableLength;
+
+    while (callSite < callSiteTableEnd) {
+        uintptr_t start = readEncodedPointer(&callSite, callSiteEncoding);
+        uintptr_t length = readEncodedPointer(&callSite, callSiteEncoding);
+        uintptr_t landingPad = readEncodedPointer(&callSite, callSiteEncoding);
+        readULEB128(&callSite); /* action value not used for C code */
         if ( landingPad == 0 )
             continue; /* no landing pad for this entry */
         if ( (start <= pcOffset) && (pcOffset < (start+length)) ) {
             /* Found landing pad for the PC.
-             * Set Instruction Pointer to so we re-enter function 
+             * Set Instruction Pointer to so we re-enter function
              * at landing pad. The landing pad is created by the compiler
              * to take two parameters in registers.
-	     */
-            _Unwind_SetGR(context, __builtin_eh_return_data_regno(0), 
-                                                (uintptr_t)exceptionObject);
-            _Unwind_SetGR(context, __builtin_eh_return_data_regno(1), 0);
-            _Unwind_SetIP(context, funcStart+landingPad);
-            return _URC_INSTALL_CONTEXT;
+            */
+            resumeIp = funcStart + landingPad;
+            break;
         }
     }
-    
-    /* No landing pad found, continue unwinding. */
-    return _URC_CONTINUE_UNWIND;
+#endif // SJ/LJ
+
+    if (resumeIp == 0)
+        return _URC_CONTINUE_UNWIND;
+    else
+    {
+        _Unwind_SetGR(context, __builtin_eh_return_data_regno (0), (uintptr_t)exceptionObject);
+        _Unwind_SetGR(context, __builtin_eh_return_data_regno (1), 0);
+        _Unwind_SetIP(context, resumeIp);
+        return _URC_INSTALL_CONTEXT;
+    }
 }