[release-branch.go1.22] cmd/internal/obj/ppc64: don't modify runtime.elf_* symbols

The runtime.elf_* symbols are assembly functions which are used
to support the gcc/llvm -Os option when used with cgo.

When compiling Go for shared code, we attempt to strip out the
TOC regenation code added by the go assembler for these symbols.

This causes the symbol to no longer appear as an assembly
function which causes problems later on when handling other
implicit symbols.

Avoid adding a TOC regeneration prologue to these functions
to avoid this issue.

Fixes #66412

Change-Id: Icbf8e4438d177082a57bb228e39b232e7a0d7ada
Reviewed-on: https://go-review.googlesource.com/c/go/+/571835
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Paul Murphy <murp@ibm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/c/go/+/572875

diff --git a/src/cmd/go/testdata/script/test_ppc64_linker_funcs.txt b/src/cmd/go/testdata/script/test_ppc64_linker_funcs.txt
index 735b5dcc7f69567b348d54d77e5c2c61ae9fb46c..d789f89f4e68cdf5114e6733858a9834a1408f2c 100644 (file)
--- a/src/cmd/go/testdata/script/test_ppc64_linker_funcs.txt
+++ b/src/cmd/go/testdata/script/test_ppc64_linker_funcs.txt
@@ -14,6 +14,10 @@ go build -ldflags='-linkmode=internal'
 exec ./abitest
 stdout success
 
+go build -buildmode=pie -o abitest.pie -ldflags='-linkmode=internal'
+exec ./abitest.pie
+stdout success
+
 -- go.mod --
 module abitest
 

diff --git a/src/cmd/internal/obj/ppc64/obj9.go b/src/cmd/internal/obj/ppc64/obj9.go
index a3d392d62c263e7c1b4e2ba617485746ba1272a0..7e26118bc0a1bc8c1006025c3d8d9ff5ef10cce4 100644 (file)
--- a/src/cmd/internal/obj/ppc64/obj9.go
+++ b/src/cmd/internal/obj/ppc64/obj9.go
@@ -37,6 +37,7 @@ import (
        "internal/abi"
        "log"
        "math/bits"
+       "strings"
 )
 
 // Test if this value can encoded as a mask for
@@ -72,6 +73,22 @@ func encodePPC64RLDCMask(mask int64) (mb, me int) {
        return mb, me - 1
 }
 
+// Is this a symbol which should never have a TOC prologue generated?
+// These are special functions which should not have a TOC regeneration
+// prologue.
+func isNOTOCfunc(name string) bool {
+       switch {
+       case name == "runtime.duffzero":
+               return true
+       case name == "runtime.duffcopy":
+               return true
+       case strings.HasPrefix(name, "runtime.elf_"):
+               return true
+       default:
+               return false
+       }
+}
+
 func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
        p.From.Class = 0
        p.To.Class = 0
@@ -762,7 +779,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 
                        q = p
 
-                       if NeedTOCpointer(c.ctxt) && c.cursym.Name != "runtime.duffzero" && c.cursym.Name != "runtime.duffcopy" {
+                       if NeedTOCpointer(c.ctxt) && !isNOTOCfunc(c.cursym.Name) {
                                // When compiling Go into PIC, without PCrel support, all functions must start
                                // with instructions to load the TOC pointer into r2:
                                //

diff --git a/src/cmd/link/internal/ppc64/asm.go b/src/cmd/link/internal/ppc64/asm.go
index 09647d84b192e1268864b506885f3ab80ed1583d..de5614e92af918c73d10032acb85603f59fac712 100644 (file)
--- a/src/cmd/link/internal/ppc64/asm.go
+++ b/src/cmd/link/internal/ppc64/asm.go
@@ -474,24 +474,9 @@ func rewriteABIFuncReloc(ctxt *ld.Link, ldr *loader.Loader, tname string, r load
        r.SetAdd(int64((n - minReg) * offMul))
        firstUse = !ldr.AttrReachable(ts)
        if firstUse {
-               ldr.SetAttrReachable(ts, true)
                // This function only becomes reachable now. It has been dropped from
                // the text section (it was unreachable until now), it needs included.
-               //
-               // Similarly, TOC regeneration should not happen for these functions,
-               // remove it from this save/restore function.
-               if ldr.AttrShared(ts) {
-                       sb := ldr.MakeSymbolUpdater(ts)
-                       sb.SetData(sb.Data()[8:])
-                       sb.SetSize(sb.Size() - 8)
-                       relocs := sb.Relocs()
-                       // Only one PCREL reloc to .TOC. should be present.
-                       if relocs.Count() != 1 {
-                               log.Fatalf("Unexpected number of relocs in %s\n", ldr.SymName(ts))
-                       }
-                       sb.ResetRelocs()
-
-               }
+               ldr.SetAttrReachable(ts, true)
        }
        return ts, firstUse
 }