cmd/link: separate elf addend size from reloc size

The size of the field may be smaller than the addend,
such is the case with R_PPC64_TOC16_HA/LO and similar
relocations.

Add an extra return value to ldelf.relSize to account for
addend size which may be larger than the relocated field,
and fix the related ppc64 relocations.

Such relocs can be seen in large PIC blobs such
as the ppc64le race detector included with golang.

Change-Id: I457186fea5d0ec5572b9bbf79bb7fa21a36cc1b0
Reviewed-on: https://go-review.googlesource.com/c/go/+/303990
Run-TryBot: Paul Murphy <murp@ibm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Lynn Boger <laboger@linux.vnet.ibm.com>

diff --git a/src/cmd/link/internal/loadelf/ldelf.go b/src/cmd/link/internal/loadelf/ldelf.go
index e373a6e0b413d3c98c7877585ddf21f8bc5df392..28284e9de0d0f2965446e1c57fcf3ac9001e18ab 100644 (file)
--- a/src/cmd/link/internal/loadelf/ldelf.go
+++ b/src/cmd/link/internal/loadelf/ldelf.go
@@ -755,7 +755,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, f *bio.Reader,
                        }
 
                        rType := objabi.ElfRelocOffset + objabi.RelocType(relocType)
-                       rSize, err := relSize(arch, pn, uint32(relocType))
+                       rSize, addendSize, err := relSize(arch, pn, uint32(relocType))
                        if err != nil {
                                return nil, 0, err
                        }
@@ -772,10 +772,10 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, f *bio.Reader,
                                }
                        }
 
-                       if rSize == 2 {
+                       if addendSize == 2 {
                                rAdd = int64(int16(rAdd))
                        }
-                       if rSize == 4 {
+                       if addendSize == 4 {
                                rAdd = int64(int32(rAdd))
                        }
 
@@ -947,7 +947,10 @@ func readelfsym(newSym, lookup func(string, int) loader.Sym, l *loader.Loader, a
        return nil
 }
 
-func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, error) {
+// Return the size of the relocated field, and the size of the addend as the first
+// and second values. Note, the addend may be larger than the relocation field in
+// some cases when a relocated value is split across multiple relocations.
+func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, uint8, error) {
        // TODO(mdempsky): Replace this with a struct-valued switch statement
        // once golang.org/issue/15164 is fixed or found to not impair cmd/link
        // performance.
@@ -966,7 +969,7 @@ func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, error) {
 
        switch uint32(arch.Family) | elftype<<16 {
        default:
-               return 0, fmt.Errorf("%s: unknown relocation type %d; compiled without -fpic?", pn, elftype)
+               return 0, 0, fmt.Errorf("%s: unknown relocation type %d; compiled without -fpic?", pn, elftype)
 
        case MIPS | uint32(elf.R_MIPS_HI16)<<16,
                MIPS | uint32(elf.R_MIPS_LO16)<<16,
@@ -990,26 +993,18 @@ func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, error) {
                MIPS64 | uint32(elf.R_MIPS_GPREL32)<<16,
                MIPS64 | uint32(elf.R_MIPS_64)<<16,
                MIPS64 | uint32(elf.R_MIPS_GOT_DISP)<<16:
-               return 4, nil
+               return 4, 4, nil
 
        case S390X | uint32(elf.R_390_8)<<16:
-               return 1, nil
+               return 1, 1, nil
 
        case PPC64 | uint32(elf.R_PPC64_TOC16)<<16,
-               PPC64 | uint32(elf.R_PPC64_TOC16_LO)<<16,
-               PPC64 | uint32(elf.R_PPC64_TOC16_HI)<<16,
-               PPC64 | uint32(elf.R_PPC64_TOC16_HA)<<16,
-               PPC64 | uint32(elf.R_PPC64_TOC16_DS)<<16,
-               PPC64 | uint32(elf.R_PPC64_TOC16_LO_DS)<<16,
-               PPC64 | uint32(elf.R_PPC64_REL16_LO)<<16,
-               PPC64 | uint32(elf.R_PPC64_REL16_HI)<<16,
-               PPC64 | uint32(elf.R_PPC64_REL16_HA)<<16,
                S390X | uint32(elf.R_390_16)<<16,
                S390X | uint32(elf.R_390_GOT16)<<16,
                S390X | uint32(elf.R_390_PC16)<<16,
                S390X | uint32(elf.R_390_PC16DBL)<<16,
                S390X | uint32(elf.R_390_PLT16DBL)<<16:
-               return 2, nil
+               return 2, 2, nil
 
        case ARM | uint32(elf.R_ARM_ABS32)<<16,
                ARM | uint32(elf.R_ARM_GOT32)<<16,
@@ -1057,7 +1052,7 @@ func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, error) {
                S390X | uint32(elf.R_390_PLT32DBL)<<16,
                S390X | uint32(elf.R_390_GOTPCDBL)<<16,
                S390X | uint32(elf.R_390_GOTENT)<<16:
-               return 4, nil
+               return 4, 4, nil
 
        case AMD64 | uint32(elf.R_X86_64_64)<<16,
                AMD64 | uint32(elf.R_X86_64_PC64)<<16,
@@ -1072,11 +1067,11 @@ func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, error) {
                S390X | uint32(elf.R_390_PC64)<<16,
                S390X | uint32(elf.R_390_GOT64)<<16,
                S390X | uint32(elf.R_390_PLT64)<<16:
-               return 8, nil
+               return 8, 8, nil
 
        case RISCV64 | uint32(elf.R_RISCV_RVC_BRANCH)<<16,
                RISCV64 | uint32(elf.R_RISCV_RVC_JUMP)<<16:
-               return 2, nil
+               return 2, 2, nil
 
        case RISCV64 | uint32(elf.R_RISCV_32)<<16,
                RISCV64 | uint32(elf.R_RISCV_BRANCH)<<16,
@@ -1088,12 +1083,22 @@ func relSize(arch *sys.Arch, pn string, elftype uint32) (uint8, error) {
                RISCV64 | uint32(elf.R_RISCV_PCREL_LO12_I)<<16,
                RISCV64 | uint32(elf.R_RISCV_PCREL_LO12_S)<<16,
                RISCV64 | uint32(elf.R_RISCV_RELAX)<<16:
-               return 4, nil
+               return 4, 4, nil
 
        case RISCV64 | uint32(elf.R_RISCV_64)<<16,
                RISCV64 | uint32(elf.R_RISCV_CALL)<<16,
                RISCV64 | uint32(elf.R_RISCV_CALL_PLT)<<16:
-               return 8, nil
+               return 8, 8, nil
+
+       case PPC64 | uint32(elf.R_PPC64_TOC16_LO)<<16,
+               PPC64 | uint32(elf.R_PPC64_TOC16_HI)<<16,
+               PPC64 | uint32(elf.R_PPC64_TOC16_HA)<<16,
+               PPC64 | uint32(elf.R_PPC64_TOC16_DS)<<16,
+               PPC64 | uint32(elf.R_PPC64_TOC16_LO_DS)<<16,
+               PPC64 | uint32(elf.R_PPC64_REL16_LO)<<16,
+               PPC64 | uint32(elf.R_PPC64_REL16_HI)<<16,
+               PPC64 | uint32(elf.R_PPC64_REL16_HA)<<16:
+               return 2, 4, nil
        }
 }