From owner-freebsd-bugs  Wed Jul 19 17:34:27 2000
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To: sheldonh@FreeBSD.ORG
Cc: pfeifer@dbai.tuwien.ac.at, freebsd-bugs@FreeBSD.ORG,
	cracauer@FreeBSD.ORG
Subject: Re: bin/19983: sh dumps core reproducibly
From: Tor.Egge@fast.no
In-Reply-To: Your message of "Tue, 18 Jul 2000 09:40:48 -0700 (PDT)"
References: <200007181640.JAA81033@freefall.freebsd.org>
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Date: Thu, 20 Jul 2000 02:34:05 +0200
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growstackblock() sometimes relocates a stack_block considered empty 
without properly relocating stack marks referencing that block.
The first call to popstackmark() with the unrelocated stack mark
as argument then causes sh to abort.

Relocating the relevant stack marks seems to solve this problem.

The patch changes the semantics of popstackmark() somewhat.  It can
only be called once after a call to setstackmark(), thus cmdloop() in
main.c needs an extra call to setstackmark().

- Tor Egge

Index: bin/sh/main.c
===================================================================
RCS file: /home/ncvs/src/bin/sh/main.c,v
retrieving revision 1.19
diff -u -r1.19 main.c
--- bin/sh/main.c	2000/04/14 06:03:39	1.19
+++ bin/sh/main.c	2000/07/20 00:26:56
@@ -253,12 +253,13 @@
 			evaltree(n, 0);
 		}
 		popstackmark(&smark);
+		setstackmark(&smark);
 		if (evalskip == SKIPFILE) {
 			evalskip = 0;
 			break;
 		}
 	}
-	popstackmark(&smark);		/* unnecessary */
+	popstackmark(&smark);
 }
 
 
Index: bin/sh/memalloc.c
===================================================================
RCS file: /home/ncvs/src/bin/sh/memalloc.c,v
retrieving revision 1.15
diff -u -r1.15 memalloc.c
--- bin/sh/memalloc.c	1999/08/27 23:15:16	1.15
+++ bin/sh/memalloc.c	2000/07/20 00:09:03
@@ -118,6 +118,7 @@
 
 struct stack_block stackbase;
 struct stack_block *stackp = &stackbase;
+struct stackmark *markp;
 char *stacknxt = stackbase.space;
 int stacknleft = MINSIZE;
 int sstrnleft;
@@ -176,6 +177,8 @@
 	mark->stackp = stackp;
 	mark->stacknxt = stacknxt;
 	mark->stacknleft = stacknleft;
+	mark->marknext = markp;
+	markp = mark;
 }
 
 
@@ -186,6 +189,7 @@
 	struct stack_block *sp;
 
 	INTOFF;
+	markp = mark->marknext;
 	while (stackp != mark->stackp) {
 		sp = stackp;
 		stackp = sp->prev;
@@ -215,6 +219,7 @@
 	char *oldspace;
 	int oldlen;
 	struct stack_block *sp;
+	struct stack_block *oldstackp;
 
 	newlen = ALIGN(stacknleft * 2 + 100);
 	oldspace = stacknxt;
@@ -222,6 +227,7 @@
 
 	if (stacknxt == stackp->space && stackp != &stackbase) {
 		INTOFF;
+		oldstackp = stackp;
 		sp = stackp;
 		stackp = sp->prev;
 		sp = ckrealloc((pointer)sp, sizeof(struct stack_block) - 
@@ -230,6 +236,19 @@
 		stackp = sp;
 		stacknxt = sp->space;
 		stacknleft = newlen;
+		{
+		  /* Stack marks pointing to the start of the old block
+		   * must be relocated to point to the new block 
+		   */
+		  struct stackmark *xmark;
+		  xmark = markp;
+		  while (xmark != NULL && xmark->stackp == oldstackp) {
+		    xmark->stackp = stackp;
+		    xmark->stacknxt = stacknxt;
+		    xmark->stacknleft = stacknleft;
+		    xmark = xmark->marknext;
+		  }
+		}
 		INTON;
 	} else {
 		p = stalloc(newlen);
Index: bin/sh/memalloc.h
===================================================================
RCS file: /home/ncvs/src/bin/sh/memalloc.h,v
retrieving revision 1.6
diff -u -r1.6 memalloc.h
--- bin/sh/memalloc.h	1999/08/27 23:15:17	1.6
+++ bin/sh/memalloc.h	2000/07/20 00:08:33
@@ -41,6 +41,7 @@
 	struct stack_block *stackp;
 	char *stacknxt;
 	int stacknleft;
+        struct stackmark *marknext;
 };
 
 


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