cmd/link: work around arm64 linker bugs with GOT relocations against local symbols

Change-Id: Ie14530c57720f1af1960ab77686b860e906058c6
Reviewed-on: https://go-review.googlesource.com/16582
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/cmd/link/internal/arm64/asm.go b/src/cmd/link/internal/arm64/asm.go
index 844a363d7a37ee310b7238dd52ca9ec86c14fbef..0e5a2d0a63cdf26c51f854c0570c4fa987fb54c3 100644 (file)
--- a/src/cmd/link/internal/arm64/asm.go
+++ b/src/cmd/link/internal/arm64/asm.go
@@ -241,8 +241,38 @@ func archreloc(r *ld.Reloc, s *ld.LSym, val *int64) int {
                default:
                        return -1
 
-               case obj.R_ADDRARM64,
-                       obj.R_ARM64_GOTPCREL:
+               case obj.R_ARM64_GOTPCREL:
+                       var o1, o2 uint32
+                       if ld.Ctxt.Arch.ByteOrder == binary.BigEndian {
+                               o1 = uint32(*val >> 32)
+                               o2 = uint32(*val)
+                       } else {
+                               o1 = uint32(*val)
+                               o2 = uint32(*val >> 32)
+                       }
+                       // Any relocation against a function symbol is redirected to
+                       // be against a local symbol instead (see putelfsym in
+                       // symtab.go) but unfortunately the system linker was buggy
+                       // when confronted with a R_AARCH64_ADR_GOT_PAGE relocation
+                       // against a local symbol until May 2015
+                       // (https://sourceware.org/bugzilla/show_bug.cgi?id=18270). So
+                       // we convert the adrp; ld64 + R_ARM64_GOTPCREL into adrp;
+                       // add + R_ADDRARM64.
+                       if !(r.Sym.Version != 0 || (r.Sym.Type&obj.SHIDDEN != 0) || r.Sym.Local) && r.Sym.Type == obj.STEXT && ld.DynlinkingGo() {
+                               if o2&0xffc00000 != 0xf9400000 {
+                                       ld.Ctxt.Diag("R_ARM64_GOTPCREL against unexpected instruction %x", o2)
+                               }
+                               o2 = 0x91000000 | (o2 & 0x000003ff)
+                               r.Type = obj.R_ADDRARM64
+                       }
+                       if ld.Ctxt.Arch.ByteOrder == binary.BigEndian {
+                               *val = int64(o1)<<32 | int64(o2)
+                       } else {
+                               *val = int64(o2)<<32 | int64(o1)
+                       }
+                       fallthrough
+
+               case obj.R_ADDRARM64:
                        r.Done = 0
 
                        // set up addend for eventual relocation via outer symbol.