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[dev.link] cmd/link: support updates to contents of obj-based Syms

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Add in the hooks to SymbolBuilder and to the loader to allow
the linker to make modifications to a non-external symbol (e.g.
a sym whose index is less than loader.extStart).

The basic idea is to manufacture a new external symbol with the same
name and version, then import the old symbol's content (type, data,
relocations, etc) into the payload struct for the new symbol, and
finally redirect the name lookup tables to target the new sym for the
specified name/version.

This change is needed in order to convert over the host object loaders
to avoid use of sym.Symbol.

Change-Id: I79cd42b23794e830bbdbcbcd2c500c35c351f01f
Reviewed-on: https://go-review.googlesource.com/c/go/+/211897
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2019-12-16 14:14:29 -05:00
parent a52cea446d
commit d5854bf8e6
3 changed files with 261 additions and 85 deletions
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49
src/cmd/link/internal/loader/loader_test.go
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@ -59,9 +59,9 @@ func TestAddMaterializedSymbol(t *testing.T) {
}
// Grab symbol builder pointers
sb1 := ldr.MakeSymbolUpdater(es1)
sb2 := ldr.MakeSymbolUpdater(es2)
sb3 := ldr.MakeSymbolUpdater(es3)
sb1, es1 := ldr.MakeSymbolUpdater(es1)
sb2, es2 := ldr.MakeSymbolUpdater(es2)
sb3, es3 := ldr.MakeSymbolUpdater(es3)
// Check get/set symbol type
es3typ := sb3.Type()
@ -108,8 +108,8 @@ func TestAddMaterializedSymbol(t *testing.T) {
}
}
sb1 = ldr.MakeSymbolUpdater(es1)
sb2 = ldr.MakeSymbolUpdater(es2)
sb1, es1 = ldr.MakeSymbolUpdater(es1)
sb2, es2 = ldr.MakeSymbolUpdater(es2)
// Get/set a few other attributes
if ldr.AttrVisibilityHidden(es3) {
@ -217,7 +217,7 @@ func sameRelocSlice(s1 []Reloc, s2 []Reloc) bool {
return true
}
type addFunc func(l *Loader, s Sym, s2 Sym)
type addFunc func(l *Loader, s Sym, s2 Sym) Sym
func TestAddDataMethods(t *testing.T) {
edummy := func(s *sym.Symbol, str string, off int) {}
@ -239,47 +239,52 @@ func TestAddDataMethods(t *testing.T) {
}{
{
which: "AddUint8",
addDataFunc: func(l *Loader, s Sym, _ Sym) {
sb := l.MakeSymbolUpdater(s)
addDataFunc: func(l *Loader, s Sym, _ Sym) Sym {
sb, ns := l.MakeSymbolUpdater(s)
sb.AddUint8('a')
return ns
},
expData: []byte{'a'},
expKind: sym.SDATA,
},
{
which: "AddUintXX",
addDataFunc: func(l *Loader, s Sym, _ Sym) {
sb := l.MakeSymbolUpdater(s)
addDataFunc: func(l *Loader, s Sym, _ Sym) Sym {
sb, ns := l.MakeSymbolUpdater(s)
sb.AddUintXX(arch, 25185, 2)
return ns
},
expData: []byte{'a', 'b'},
expKind: sym.SDATA,
},
{
which: "SetUint8",
addDataFunc: func(l *Loader, s Sym, _ Sym) {
sb := l.MakeSymbolUpdater(s)
addDataFunc: func(l *Loader, s Sym, _ Sym) Sym {
sb, ns := l.MakeSymbolUpdater(s)
sb.AddUint8('a')
sb.AddUint8('b')
sb.SetUint8(arch, 1, 'c')
return ns
},
expData: []byte{'a', 'c'},
expKind: sym.SDATA,
},
{
which: "AddString",
addDataFunc: func(l *Loader, s Sym, _ Sym) {
sb := l.MakeSymbolUpdater(s)
addDataFunc: func(l *Loader, s Sym, _ Sym) Sym {
sb, ns := l.MakeSymbolUpdater(s)
sb.Addstring("hello")
return ns
},
expData: []byte{'h', 'e', 'l', 'l', 'o', 0},
expKind: sym.SNOPTRDATA,
},
{
which: "AddAddrPlus",
addDataFunc: func(l *Loader, s Sym, s2 Sym) {
sb := l.MakeSymbolUpdater(s)
addDataFunc: func(l *Loader, s Sym, s2 Sym) Sym {
sb, ns := l.MakeSymbolUpdater(s)
sb.AddAddrPlus(arch, s2, 3)
return ns
},
expData: []byte{0, 0, 0, 0, 0, 0, 0, 0},
expKind: sym.SDATA,
@ -287,9 +292,10 @@ func TestAddDataMethods(t *testing.T) {
},
{
which: "AddAddrPlus4",
addDataFunc: func(l *Loader, s Sym, s2 Sym) {
sb := l.MakeSymbolUpdater(s)
addDataFunc: func(l *Loader, s Sym, s2 Sym) Sym {
sb, ns := l.MakeSymbolUpdater(s)
sb.AddAddrPlus4(arch, s2, 3)
return ns
},
expData: []byte{0, 0, 0, 0},
expKind: sym.SDATA,
@ -297,9 +303,10 @@ func TestAddDataMethods(t *testing.T) {
},
{
which: "AddCURelativeAddrPlus",
addDataFunc: func(l *Loader, s Sym, s2 Sym) {
sb := l.MakeSymbolUpdater(s)
addDataFunc: func(l *Loader, s Sym, s2 Sym) Sym {
sb, ns := l.MakeSymbolUpdater(s)
sb.AddCURelativeAddrPlus(arch, s2, 7)
return ns
},
expData: []byte{0, 0, 0, 0, 0, 0, 0, 0},
expKind: sym.SDATA,
@ -314,7 +321,7 @@ func TestAddDataMethods(t *testing.T) {
if mi == 0 {
t.Fatalf("AddExtSym failed for '" + name + "'")
}
tp.addDataFunc(ldr, mi, pmi)
mi = tp.addDataFunc(ldr, mi, pmi)
if ldr.SymType(mi) != tp.expKind {
t.Errorf("testing Loader.%s: expected kind %s got %s",
tp.which, tp.expKind, ldr.SymType(mi))