Rerouted the global alternate stack to the end (lowest address) of each process stack. This fixes potentially shared stacks and allows the garbage collector to traverse stack frames even if a process is currently handling user-defined signals on the alternate stack. However, the alternate stack is used for catching segmentation faults caused by stack overflows, which may now reuse the last part of the stack and therefore corrupt stack traces. This is an experimental patch and may need improvement.

git-svn-id: https://svn.inf.ethz.ch/svn/lecturers/a2/trunk@8468 8c9fc860-2736-0410-a75d-ab315db34111

source/Linux.Unix.Mod

@@ -22,6 +22,8 @@ CONST
 
 	PageSize* = 4096;	(* least MMU page size *)
 
+	AlternateStackSize = 32 * 4096;
+
 	stdin* = 0;  stdout* = 1;  stderr* = 2;
 
 	(** Unix error codes:	*)
@@ -463,9 +465,6 @@ VAR
 		sysname-, nodename-, release-, version-, machine-: ARRAY 65 OF CHAR;
 	END;
 
-	sigstack-: ARRAY 32*4096 OF CHAR;
-
-
 	sysconf: PROCEDURE {C} (name: LONGINT):WORD;
 
 	pthread_mutex_init: PROCEDURE {C} (mutex: ADDRESS; mutexattr: ADDRESS): WORD;
@@ -493,9 +492,12 @@ VAR
 	pthread_getspecific	: PROCEDURE {C} ( key: Key_t ): ADDRESS;
 
 	pthread_attr_init: PROCEDURE {C} (attr: ADDRESS);
+	pthread_attr_destroy: PROCEDURE {C} (attr: ADDRESS);
 	pthread_attr_setscope: PROCEDURE {C}(attr: ADDRESS; set: WORD);
 	pthread_attr_setdetachstate: PROCEDURE {C}(attr: ADDRESS; set: WORD);
 	pthread_attr_setstacksize: PROCEDURE {C}(attr: ADDRESS; stackSize: SIZE);
+	pthread_attr_getstacksize: PROCEDURE {C}(attr: ADDRESS; stackSize: ADDRESS);
+	pthread_getattr_np: PROCEDURE {C} (thr: ADDRESS; attr: ADDRESS);
 	pthread_self-: PROCEDURE {C} (): Thread_t;
 
 	sched_get_priority_max: PROCEDURE {C} (policy: LONGINT): LONGINT;
@@ -737,25 +739,29 @@ VAR
 	    RETURN  param.sched_priority;
 	END ThrGetPriority;
 
-	VAR
-		sigstk: Stack;
-
-	PROCEDURE SetSigaltstack;
-	BEGIN {UNCOOPERATIVE, UNCHECKED}
-		IF sigaltstack(ADDRESS OF sigstk, NIL) < 0 THEN
-			Perror("sigaltstack")
-		END;
-	END SetSigaltstack;
-
 	PROCEDURE {C} Starter(proc: PROCEDURE): ADDRESS;
 	VAR
 		me: Thread_t;
 		old, new: Sigset_t;
 		param: Sched_param;
 		res: WORD;
+		attr: PThreadAttr;
+		stack: Stack;
+		size: SIZE;
 	BEGIN {UNCOOPERATIVE, UNCHECKED}
 		me := pthread_self();
-		SetSigaltstack();
+
+		pthread_getattr_np(me, ADDRESS OF attr);
+		pthread_attr_getstacksize (ADDRESS OF attr, ADDRESS OF size);
+		pthread_attr_destroy(ADDRESS OF attr);
+
+		stack.sp := S.GetFramePointer () - size + AlternateStackSize;
+		stack.size := AlternateStackSize;
+		stack.flags := {};
+
+		IF sigaltstack(ADDRESS OF stack, NIL) # 0 THEN
+			Perror("signaltstack")
+		END;
 
 		IF sigfillset( ADDRESS OF new ) < 0 THEN
 			Perror("sigfillset");
@@ -792,7 +798,7 @@ VAR
 		pthread_attr_setscope(ADDRESS OF attr, PTHREAD_SCOPE_SYSTEM);
 		pthread_attr_setdetachstate(ADDRESS OF attr, PTHREAD_CREATE_DETACHED);
 		(*pthread_attr_setdetachstate(ADDRESS OF attr, 0);*)
-		pthread_attr_setstacksize(ADDRESS OF attr, stackSize);
+		pthread_attr_setstacksize(ADDRESS OF attr, stackSize + AlternateStackSize);
 		res := pthread_create(ADDRESS OF id, ADDRESS OF attr, Starter, p);
 		RETURN id;
 	END ThrStart;
@@ -1002,15 +1008,6 @@ VAR
 		copy( p, sysinfo.machine );
 	END getSysinfo;
 
-	PROCEDURE CreateSignalStack;
-	BEGIN {UNCOOPERATIVE, UNCHECKED}
-		sigstk.sp := ADDRESS OF sigstack;
-		sigstk.size := LEN(sigstack);
-		sigstk.flags := {};
-	END CreateSignalStack;
-
-
-
 	VAR trap: SignalTrap;
 
 	PROCEDURE {C} SigHandler  ( sig: LONGINT; scp: ADDRESS; ucp: Ucontext ); (* reversed arguments !! *)
@@ -1177,9 +1174,12 @@ VAR
 		Dlsym( libp, "pthread_setcancelstate", ADDRESSOF(pthread_setcancelstate) );
 		Dlsym( libp, "pthread_setcanceltype", ADDRESSOF(pthread_setcanceltype) );
 		Dlsym( libp, "pthread_attr_init", ADDRESSOF(pthread_attr_init) );
+		Dlsym( libp, "pthread_attr_destroy", ADDRESSOF(pthread_attr_destroy) );
 		Dlsym( libp, "pthread_attr_setscope", ADDRESSOF(pthread_attr_setscope) );
 		Dlsym( libp, "pthread_attr_setdetachstate", ADDRESSOF(pthread_attr_setdetachstate) );
 		Dlsym( libp, "pthread_attr_setstacksize", ADDRESSOF(pthread_attr_setstacksize) );
+		Dlsym( libp, "pthread_attr_getstacksize", ADDRESSOF(pthread_attr_getstacksize) );
+		Dlsym( libp, "pthread_getattr_np", ADDRESSOF(pthread_getattr_np) );
 		Dlsym( libp, "pthread_self", ADDRESSOF(pthread_self) );
 
 		Dlsym( libp, "sem_init", ADDRESSOF(sem_init) );
@@ -1279,8 +1279,6 @@ VAR
 		Dlsym( libc, "__errno_location",	ADDRESSOF(errno_location ) );
 
 		getSysinfo;
-
-		CreateSignalStack;
 	END Init;
 
 	(* load X11 related libaries only on demand *)