runtime: flag static variables as no-pointers

Variables in data sections of 32-bit executables interfere with
garbage collector's ability to free objects and/or unnecessarily
slow down the garbage collector.

This changeset moves some static variables to .noptr sections.
'files' in symtab.c is now allocated dynamically.

R=golang-dev, dvyukov, minux.ma
CC=golang-dev
https://golang.org/cl/9786044

src/pkg/runtime/hashmap.c

@@ -524,6 +524,7 @@ hash_lookup(MapType *t, Hmap *h, byte **keyp)
 }
 
 // When an item is not found, fast versions return a pointer to this zeroed memory.
+#pragma dataflag 16 // no pointers
 static uint8 empty_value[MAXVALUESIZE];
 
 // Specialized versions of mapaccess1 for specific types.

src/pkg/runtime/os_darwin.c

@@ -523,6 +523,7 @@ runtime·setprof(bool on)
 		runtime·sigprocmask(SIG_BLOCK, &sigset_prof, nil);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
@@ -533,6 +534,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.

src/pkg/runtime/os_freebsd.c

@@ -235,6 +235,7 @@ runtime·setprof(bool on)
 	USED(on);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
@@ -245,6 +246,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.

src/pkg/runtime/os_linux.c

@@ -172,6 +172,7 @@ runtime·get_random_data(byte **rnd, int32 *rnd_len)
 		*rnd = runtime·startup_random_data;
 		*rnd_len = runtime·startup_random_data_len;
 	} else {
+		#pragma dataflag 16 // no pointers
 		static byte urandom_data[HashRandomBytes];
 		int32 fd;
 		fd = runtime·open("/dev/urandom", 0 /* O_RDONLY */, 0);
@@ -283,6 +284,7 @@ runtime·setprof(bool on)
 	USED(on);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
@@ -293,6 +295,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
+#pragma dataflag 16  // no pointers
 static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.

src/pkg/runtime/os_netbsd.c

@@ -275,6 +275,7 @@ runtime·setprof(bool on)
 	USED(on);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
@@ -285,6 +286,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.

src/pkg/runtime/os_openbsd.c

@@ -257,6 +257,7 @@ runtime·setprof(bool on)
 	USED(on);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
@@ -267,6 +268,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.

src/pkg/runtime/os_plan9.c

@@ -330,6 +330,7 @@ runtime·setprof(bool on)
 	USED(on);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
@@ -340,6 +341,7 @@ runtime·badcallback(void)
 	runtime·pwrite(2, badcallback, sizeof badcallback - 1, -1LL);
 }
 
+#pragma dataflag 16 // no pointers
 static int8 badsignal[] = "runtime: signal received on thread not created by Go.\n";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.

src/pkg/runtime/os_windows.c

@@ -450,9 +450,11 @@ runtime·setprof(bool on)
 	USED(on);
 }
 
+#pragma dataflag 16 // no pointers
 int8 runtime·badcallbackmsg[] = "runtime: cgo callback on thread not created by Go.\n";
 int32 runtime·badcallbacklen = sizeof runtime·badcallbackmsg - 1;
 
+#pragma dataflag 16 // no pointers
 int8 runtime·badsignalmsg[] = "runtime: signal received on thread not created by Go.\n";
 int32 runtime·badsignallen = sizeof runtime·badsignalmsg - 1;
 

src/pkg/runtime/symtab.c

@@ -307,6 +307,15 @@ gostringn(byte *p, int32 l)
 	return s;
 }
 
+static struct
+{
+	String srcstring;
+	int32 aline;
+	int32 delta;
+} *files;
+
+enum { maxfiles = 200 };
+
 // walk symtab accumulating path names for use by pc/ln table.
 // don't need the full generality of the z entry history stack because
 // there are no includes in go (and only sensible includes in our c);
@@ -314,12 +323,8 @@ gostringn(byte *p, int32 l)
 static void
 dosrcline(Sym *sym)
 {
+	#pragma dataflag 16 // no pointers
 	static byte srcbuf[1000];
-	static struct {
-		String srcstring;
-		int32 aline;
-		int32 delta;
-	} files[200];
 	static int32 incstart;
 	static int32 nfunc, nfile, nhist;
 	Func *f;
@@ -347,7 +352,7 @@ dosrcline(Sym *sym)
 			l = makepath(srcbuf, sizeof srcbuf, sym->name+1);
 			nhist = 0;
 			nfile = 0;
-			if(nfile == nelem(files))
+			if(nfile == maxfiles)
 				return;
 			files[nfile].srcstring = gostringn(srcbuf, l);
 			files[nfile].aline = 0;
@@ -358,7 +363,7 @@ dosrcline(Sym *sym)
 			if(srcbuf[0] != '\0') {
 				if(nhist++ == 0)
 					incstart = sym->value;
-				if(nhist == 0 && nfile < nelem(files)) {
+				if(nhist == 0 && nfile < maxfiles) {
 					// new top-level file
 					files[nfile].srcstring = gostringn(srcbuf, l);
 					files[nfile].aline = sym->value;
@@ -567,10 +572,12 @@ buildfuncs(void)
 	splitpcln();
 
 	// record src file and line info for each func
+	files = runtime·malloc(maxfiles * sizeof(files[0]));
 	walksymtab(dosrcline);  // pass 1: determine hugestring_len
 	hugestring.str = runtime·mallocgc(hugestring_len, FlagNoPointers, 0, 0);
 	hugestring.len = 0;
 	walksymtab(dosrcline);  // pass 2: fill and use hugestring
+	files = nil;
 
 	if(hugestring.len != hugestring_len)
 		runtime·throw("buildfunc: problem in initialization procedure");