cmd/link,runtime: remove relocations from stkobjs

Use an offset from go.func.* instead.
This removes the last relocation from funcdata symbols,
which lets us simplify that code.

size      before    after     Δ       %
addr2line 3683218   3680706   -2512   -0.068%
api       4951074   4944850   -6224   -0.126%
asm       4744258   4757586   +13328  +0.281%
buildid   2419986   2418546   -1440   -0.060%
cgo       4218306   4197346   -20960  -0.497%
compile   22132066  22076882  -55184  -0.249%
cover     4432834   4411362   -21472  -0.484%
dist      3111202   3091346   -19856  -0.638%
doc       3583602   3563234   -20368  -0.568%
fix       3023922   3020658   -3264   -0.108%
link      6188034   6164642   -23392  -0.378%
nm        3665826   3646818   -19008  -0.519%
objdump   4015234   4012450   -2784   -0.069%
pack      2155010   2153554   -1456   -0.068%
pprof     13044178  13011522  -32656  -0.250%
test2json 2402146   2383906   -18240  -0.759%
trace     9765410   9736514   -28896  -0.296%
vet       6681250   6655058   -26192  -0.392%
total     104217556 103926980 -290576 -0.279%

relocs    before  after   Δ       %
addr2line 25563   25066   -497    -1.944%
api       18409   17176   -1233   -6.698%
asm       18903   18271   -632    -3.343%
buildid   9513    9233    -280    -2.943%
cgo       17103   16222   -881    -5.151%
compile   64825   60421   -4404   -6.794%
cover     19464   18479   -985    -5.061%
dist      10798   10135   -663    -6.140%
doc       13503   12735   -768    -5.688%
fix       11465   10820   -645    -5.626%
link      23214   21849   -1365   -5.880%
nm        25480   24987   -493    -1.935%
objdump   26610   26057   -553    -2.078%
pack      7951    7665    -286    -3.597%
pprof     63964   60761   -3203   -5.008%
test2json 8735    8389    -346    -3.961%
trace     39639   37180   -2459   -6.203%
vet       25970   24044   -1926   -7.416%
total     431108  409489  -21619  -5.015%

Change-Id: I43c26196a008da6d1cb3a782eea2f428778bd569
Reviewed-on: https://go-review.googlesource.com/c/go/+/353138
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

3 files changed, 12 insertions, 30 deletions

diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index 8de0e0df1a..4f0ce23ce7 100644
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -1367,6 +1367,11 @@ func (state *dodataState) makeRelroForSharedLib(target *Link) {
 					// the relro data.
 					isRelro = true
 				}
+			case sym.SGOFUNC:
+				// The only SGOFUNC symbols that contain relocations are .stkobj,
+				// and their relocations are of type objabi.R_ADDROFF,
+				// which always get resolved during linking.
+				isRelro = false
 			}
 			if isRelro {
 				state.setSymType(s, symnrelro)
diff --git a/src/cmd/link/internal/ld/pcln.go b/src/cmd/link/internal/ld/pcln.go
index b041174cfe..b5a66b8517 100644
--- a/src/cmd/link/internal/ld/pcln.go
+++ b/src/cmd/link/internal/ld/pcln.go
@@ -711,7 +711,7 @@ func writeFuncs(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSym
 	ldr := ctxt.loader
 	deferReturnSym := ldr.Lookup("runtime.deferreturn", abiInternalVer)
 	gofunc := ldr.Lookup("go.func.*", 0)
-	gofuncrel := ldr.Lookup("go.funcrel.*", 0)
+	gofuncBase := ldr.SymValue(gofunc)
 	textStart := ldr.SymValue(ldr.Lookup("runtime.text", 0))
 	funcdata := []loader.Sym{}
 	var pcsp, pcfile, pcline, pcinline loader.Sym
@@ -813,24 +813,10 @@ func writeFuncs(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSym
 				continue
 			}
 
-			outer := ldr.OuterSym(fdsym)
-			if outer == 0 {
-				panic(fmt.Sprintf("no carrier sym for symbol %s (funcdata %s#%d)", ldr.SymName(fdsym), ldr.SymName(s), j))
+			if outer := ldr.OuterSym(fdsym); outer != gofunc {
+				panic(fmt.Sprintf("bad carrier sym for symbol %s (funcdata %s#%d), want go.func.* got %s", ldr.SymName(fdsym), ldr.SymName(s), j, ldr.SymName(outer)))
 			}
-			rel := uint32(ldr.SymValue(fdsym) - ldr.SymValue(outer))
-			// Record gofunc vs gofuncrel in bottom bit. See runtime/symtab.go:funcdata.
-			// TODO: The only symbols that in gofuncrel are .stkobj symbols.
-			// Remove those relocations, and simplify this.
-			rel <<= 1
-			switch outer {
-			case gofunc:
-			case gofuncrel:
-				rel |= 1
-			default:
-				panic(fmt.Sprintf("expected symbol %s (funcdata %s#%d) to be placed in go.func.* or go.funcrel.*, got %s (%d)",
-					ldr.SymName(fdsym), ldr.SymName(s), j, ldr.SymName(outer), outer))
-			}
-			sb.SetUint32(ctxt.Arch, int64(dataoff), rel)
+			sb.SetUint32(ctxt.Arch, int64(dataoff), uint32(ldr.SymValue(fdsym)-gofuncBase))
 		}
 	}
 }
diff --git a/src/cmd/link/internal/ld/symtab.go b/src/cmd/link/internal/ld/symtab.go
index c582e4908d..878d30b5f1 100644
--- a/src/cmd/link/internal/ld/symtab.go
+++ b/src/cmd/link/internal/ld/symtab.go
@@ -569,13 +569,8 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
 			strings.HasSuffix(name, ".args_stackmap"),
 			strings.HasSuffix(name, ".stkobj"):
 			ldr.SetAttrNotInSymbolTable(s, true)
-			if ctxt.UseRelro() && strings.HasSuffix(name, ".stkobj") {
-				symGroupType[s] = sym.SGOFUNCRELRO
-				ldr.SetCarrierSym(s, symgofuncrel)
-			} else {
-				symGroupType[s] = sym.SGOFUNC
-				ldr.SetCarrierSym(s, symgofunc)
-			}
+			symGroupType[s] = sym.SGOFUNC
+			ldr.SetCarrierSym(s, symgofunc)
 			if ctxt.Debugvlog != 0 {
 				align := ldr.SymAlign(s)
 				liveness += (ldr.SymSize(s) + int64(align) - 1) &^ (int64(align) - 1)
@@ -676,12 +671,8 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
 	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.gcbss", 0))
 	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.types", 0))
 	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.etypes", 0))
+	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.rodata", 0))
 	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("go.func.*", 0))
-	if gofuncrel := ldr.Lookup("go.funcrel.*", 0); gofuncrel != 0 {
-		moduledata.AddAddr(ctxt.Arch, gofuncrel)
-	} else {
-		moduledata.AddUint(ctxt.Arch, 0)
-	}
 
 	if ctxt.IsAIX() && ctxt.IsExternal() {
 		// Add R_XCOFFREF relocation to prevent ld's garbage collection of