cmd/link: additional fixes for -newobj and "ld -r" ELF host objects
The previous fix for this issue (CL 208479) was not general enough;
this patch revises it to handle more cases.
The problem with the original fix was that once a sym.Symbol is
created for a given static symbol and given a bogus anonymous version
of -1, we hit problems if some other non-anonymous symbol (created by
host object loading) had relocations targeting the static symbol.
In this patch instead of assigning a fixed anonymous version of -1 to
such symbols, each time loader.Create is invoked we create a new
(unique) anonymous version for the sym.Symbol, then enter the result
into the loader's extStaticSyms map, permitting it to be found in
lookups when processing relocation targets.
NB: this code will hopefully get a lot simpler once we can move host
object loading away from early sym.Symbol creation.
Updates #35779.
Change-Id: I450ff577e17549025565d355d6707a2d28a5a617
Reviewed-on: https://go-review.googlesource.com/c/go/+/208778
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index 4e0dfb1..0adc395 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -111,6 +111,8 @@
Syms []*sym.Symbol // indexed symbols. XXX we still make sym.Symbol for now.
+ anonVersion int // most recently assigned ext static sym pseudo-version
+
Reachable bitmap // bitmap of reachable symbols, indexed by global index
// Used to implement field tracking; created during deadcode if
@@ -130,9 +132,6 @@
FlagStrictDups = 1 << iota
)
-// anonVersion is used to tag symbols created by loader.Create.
-const anonVersion = -1
-
func NewLoader(flags uint32) *Loader {
nbuiltin := goobj2.NBuiltin()
return &Loader{
@@ -350,7 +349,7 @@
// This is more like Syms.ROLookup than Lookup -- it doesn't create
// new symbol.
func (l *Loader) Lookup(name string, ver int) Sym {
- if ver >= sym.SymVerStatic {
+ if ver >= sym.SymVerStatic || ver < 0 {
return l.extStaticSyms[nameVer{name, ver}]
}
return l.symsByName[ver][name]
@@ -846,13 +845,22 @@
}
// Add symbols to the ctxt.Syms lookup table. This explicitly
- // skips things created via loader.Create (marked with
- // anonVersion), since if we tried to add these we'd wind up with
- // collisions.
+ // skips things created via loader.Create (marked with versions
+ // less than zero), since if we tried to add these we'd wind up
+ // with collisions. Along the way, update the version from the
+ // negative anon version to something larger than sym.SymVerStatic
+ // (needed so that sym.symbol.IsFileLocal() works properly).
+ anonVerReplacement := syms.IncVersion()
for _, s := range l.Syms {
- if s != nil && s.Name != "" && s.Version != anonVersion {
+ if s == nil {
+ continue
+ }
+ if s.Name != "" && s.Version >= 0 {
syms.Add(s)
}
+ if s.Version < 0 {
+ s.Version = int16(anonVerReplacement)
+ }
}
}
@@ -985,11 +993,14 @@
return s
}
-// Create creates a symbol with the specified name, but does not
-// insert it into any lookup table (hence it is possible to create a
-// symbol name with name X when there is already an existing symbol
-// named X entered into the loader). This method is intended for
-// static/hidden symbols discovered while loading host objects.
+// Create creates a symbol with the specified name, returning a
+// sym.Symbol object for it. This method is intended for static/hidden
+// symbols discovered while loading host objects. We can see more than
+// one instance of a given static symbol with the same name/version,
+// so we can't add them to the lookup tables "as is". Instead assign
+// them fictitious (unique) versions, starting at -1 and decreasing by
+// one for each newly created symbol, and record them in the
+// extStaticSyms hash.
func (l *Loader) Create(name string, syms *sym.Symbols) *sym.Symbol {
i := l.max + 1
l.max++
@@ -997,13 +1008,17 @@
l.extStart = i
}
- // Note the use of anonVersion -- this is to mark the symbol so that
- // it can be skipped when ExtractSymbols is adding ext syms to the
- // sym.Symbols hash.
- l.extSyms = append(l.extSyms, nameVer{name, anonVersion})
+ // Assign a new unique negative version -- this is to mark the
+ // symbol so that it can be skipped when ExtractSymbols is adding
+ // ext syms to the sym.Symbols hash.
+ l.anonVersion--
+ ver := l.anonVersion
+ l.extSyms = append(l.extSyms, nameVer{name, ver})
l.growSyms(int(i))
- s := syms.Newsym(name, -1)
+ s := syms.Newsym(name, ver)
l.Syms[i] = s
+ l.extStaticSyms[nameVer{name, ver}] = i
+
return s
}
