[dev.link] cmd/link: add support for "local" sym attribute

Add loader hooks to get/set the "local" symbol attribute.

Change-Id: Ifc6986c678bda8923fb9b6ef041e77330f441e1f
Reviewed-on: https://go-review.googlesource.com/c/go/+/213422
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index 2276dff1bc0a14750a4a2eb88dcb4056a598c083..4ddffcc44b4bf40fe83a7af81ab27164dfab012b 100644 (file)
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -177,6 +177,7 @@ type Loader struct {
        // semantics / interpretation of the specific flags or attribute.
        attrReachable        bitmap // reachable symbols, indexed by global index
        attrOnList           bitmap // "on list" symbols, indexed by global index
+       attrLocal            bitmap // "local" symbols, indexed by global index
        attrVisibilityHidden bitmap // hidden symbols, indexed by ext sym index
        attrDuplicateOK      bitmap // dupOK symbols, indexed by ext sym index
        attrShared           bitmap // shared symbols, indexed by ext sym index
@@ -780,6 +781,22 @@ func (l *Loader) SetAttrOnList(i Sym, v bool) {
        }
 }
 
+// AttrLocal returns true for symbols that are only visible within the
+// module (executable or shared library) being linked. This attribute
+// is applied to thunks and certain other linker-generated symbols.
+func (l *Loader) AttrLocal(i Sym) bool {
+       return l.attrLocal.has(i)
+}
+
+// SetAttrLocal the "local" property for a symbol (see AttrLocal above).
+func (l *Loader) SetAttrLocal(i Sym, v bool) {
+       if v {
+               l.attrLocal.set(i)
+       } else {
+               l.attrLocal.unset(i)
+       }
+}
+
 // AttrVisibilityHidden symbols returns true for ELF symbols with
 // visibility set to STV_HIDDEN. They become local symbols in
 // the final executable. Only relevant when internally linking
@@ -1375,6 +1392,7 @@ func (l *Loader) growAttrBitmaps(reqLen int) {
                // These are indexed by global symbol
                l.attrReachable = growBitmap(reqLen, l.attrReachable)
                l.attrOnList = growBitmap(reqLen, l.attrOnList)
+               l.attrLocal = growBitmap(reqLen, l.attrLocal)
        }
        // These are indexed by external symbol offset (e.g. i - l.extStart)
        if l.extStart == 0 {
@@ -1691,10 +1709,17 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
                        s.Sub = l.Syms[sub]
                }
 
-               // Preprocess symbol and set reachability and onlist.
+               // Preprocess symbol.
                preprocess(arch, s)
+
+               // Convert attributes.
+               // Note: this is an incomplete set; will be fixed up in
+               // a subsequent patch.
                s.Attr.Set(sym.AttrReachable, l.attrReachable.has(i))
                s.Attr.Set(sym.AttrOnList, l.attrOnList.has(i))
+               if l.attrLocal.has(i) {
+                       s.Attr.Set(sym.AttrLocal, true)
+               }
 
                // Set sub-symbol attribute. FIXME: would be better
                // to do away with this and just use l.OuterSymbol() != 0