cmd/ld: do not assume that only pe section names start with '.'

Our current pe object reader assumes that every symbol starting with
'.' is section. It appeared to be true, until now gcc 4.9.1 generates
some symbols with '.' at the front. Change that logic to check other
symbol fields in addition to checking for '.'. I am not an expert
here, but it seems reasonable to me.

Added test, but it is only good, if tested with gcc 4.9.1. Otherwise
the test PASSes regardless.

Fixes #8811.
Fixes #8856.

LGTM=jfrederich, iant, stephen.gutekanst
R=golang-codereviews, jfrederich, stephen.gutekanst, iant
CC=alex.brainman, golang-codereviews
https://golang.org/cl/152410043

1 files changed, 12 insertions, 5 deletions

diff --git a/src/cmd/ld/ldpe.c b/src/cmd/ld/ldpe.c
index 9257c243c9..4f5e51f2f1 100644
--- a/src/cmd/ld/ldpe.c
+++ b/src/cmd/ld/ldpe.c
@@ -128,6 +128,7 @@ struct PeObj {
 };
 
 static int map(PeObj *obj, PeSect *sect);
+static int issect(PeSym *s);
 static int readsym(PeObj *obj, int i, PeSym **sym);
 
 void
@@ -318,8 +319,8 @@ ldpe(Biobuf *f, char *pkg, int64 len, char *pn)
 			// ld -r could generate multiple section symbols for the
 			// same section but with different values, we have to take
 			// that into account
-			if (obj->pesym[symindex].name[0] == '.')
-					rp->add += obj->pesym[symindex].value;
+			if(issect(&obj->pesym[symindex]))
+				rp->add += obj->pesym[symindex].value;
 		}
 		qsort(r, rsect->sh.NumberOfRelocations, sizeof r[0], rbyoff);
 		
@@ -327,12 +328,12 @@ ldpe(Biobuf *f, char *pkg, int64 len, char *pn)
 		s->r = r;
 		s->nr = rsect->sh.NumberOfRelocations;
 	}
-	
+
 	// enter sub-symbols into symbol table.
 	for(i=0; i<obj->npesym; i++) {
 		if(obj->pesym[i].name == 0)
 			continue;
-		if(obj->pesym[i].name[0] == '.') //skip section
+		if(issect(&obj->pesym[i]))
 			continue;
 		if(obj->pesym[i].sectnum > 0) {
 			sect = &obj->sect[obj->pesym[i].sectnum-1];
@@ -431,6 +432,12 @@ map(PeObj *obj, PeSect *sect)
 }
 
 static int
+issect(PeSym *s)
+{
+	return s->sclass == IMAGE_SYM_CLASS_STATIC && s->type == 0 && s->name[0] == '.';
+}
+
+static int
 readsym(PeObj *obj, int i, PeSym **y)
 {
 	LSym *s;
@@ -445,7 +452,7 @@ readsym(PeObj *obj, int i, PeSym **y)
 	sym = &obj->pesym[i];
 	*y = sym;
 	
-	if(sym->name[0] == '.') // .section
+	if(issect(sym))
 		name = obj->sect[sym->sectnum-1].sym->name;
 	else {
 		name = sym->name;