From: Rob Pike <r@golang.org>
Date: Thu, 4 Sep 2008 02:58:46 +0000 (-0700)
Subject: fix bug in stack overflow check.
X-Git-Tag: weekly.2009-11-06~3279
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=6c72bfa55be31d60c7c87951a30cff9c6477d1cb;p=gostls13.git

fix bug in stack overflow check.
if stack is in low memory and frame size is huge, test could wrap around!
fix by omitting test altogether if we know frame is big.

R=gri
OCL=14782
CL=14782
---

diff --git a/src/cmd/6l/pass.c b/src/cmd/6l/pass.c
index e071f6e1a9..fed9495c17 100644
--- a/src/cmd/6l/pass.c
+++ b/src/cmd/6l/pass.c
@@ -669,34 +669,36 @@ dostkoff(void)
 			q = P;
 			if(pmorestack != P)
 			if(!(p->from.scale & NOSPLIT)) {
-				if(autoffset <= 75) {
-					// small stack
-					p = appendp(p);
-					p->as = ACMPQ;
-					p->from.type = D_SP;
-					p->to.type = D_INDIR+D_R15;
-					
-				} else {
-					// large stack
-					p = appendp(p);
-					p->as = ALEAQ;
-					p->from.type = D_INDIR+D_SP;
-					p->from.offset = -(autoffset-75);
-					p->to.type = D_AX;
-
+				if(autoffset < 4096) {  // do we need to call morestack
+					if(autoffset <= 75) {
+						// small stack
+						p = appendp(p);
+						p->as = ACMPQ;
+						p->from.type = D_SP;
+						p->to.type = D_INDIR+D_R15;
+						
+					} else {
+						// large stack
+						p = appendp(p);
+						p->as = ALEAQ;
+						p->from.type = D_INDIR+D_SP;
+						p->from.offset = -(autoffset-75);
+						p->to.type = D_AX;
+	
+						p = appendp(p);
+						p->as = ACMPQ;
+						p->from.type = D_AX;
+						p->to.type = D_INDIR+D_R15;
+					}
+	
+					// common
 					p = appendp(p);
-					p->as = ACMPQ;
-					p->from.type = D_AX;
-					p->to.type = D_INDIR+D_R15;
+					p->as = AJHI;
+					p->to.type = D_BRANCH;
+					p->to.offset = 4;
+					q = p;
 				}
 
-				// common
-				p = appendp(p);
-				p->as = AJHI;
-				p->to.type = D_BRANCH;
-				p->to.offset = 4;
-				q = p;
-
 				p = appendp(p);
 				p->as = AMOVQ;
 				p->from.type = D_CONST;
diff --git a/test/bugs/bug092.go b/test/fixedbugs/bug092.go
similarity index 100%
rename from test/bugs/bug092.go
rename to test/fixedbugs/bug092.go
diff --git a/test/golden.out b/test/golden.out
index da9ff597f3..fd062fa9a7 100644
--- a/test/golden.out
+++ b/test/golden.out
@@ -145,10 +145,6 @@ BUG: fails incorrectly
 =========== bugs/bug090.go
 BUG: compilation succeeds incorrectly
 
-=========== bugs/bug092.go
-BUG should not crash
-$RUNFILE: line 1: PID Illegal instruction     ./$A.out
-
 =========== fixedbugs/bug015.go
 fixedbugs/bug015.go:7: overflow converting constant to <int64>INT64