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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package sym
import (
"cmd/internal/objabi"
"cmd/internal/sys"
"debug/elf"
)
// Reloc is a relocation.
//
// The typical Reloc rewrites part of a symbol at offset Off to address Sym.
// A Reloc is stored in a slice on the Symbol it rewrites.
//
// Relocations are generated by the compiler as the type
// cmd/internal/obj.Reloc, which is encoded into the object file wire
// format and decoded by the linker into this type. A separate type is
// used to hold linker-specific state about the relocation.
//
// Some relocations are created by cmd/link.
type Reloc struct {
Off int32 // offset to rewrite
Siz uint8 // number of bytes to rewrite, 1, 2, or 4
Done bool // set to true when relocation is complete
Type objabi.RelocType // the relocation type
Add int64 // addend
Sym *Symbol // symbol the relocation addresses
*RelocExt // extra fields (see below), may be nil, call InitExt before use
}
// relocExt contains extra fields in Reloc that are used only in
// certain cases.
type RelocExt struct {
Xadd int64 // addend passed to external linker
Xsym *Symbol // symbol passed to external linker
Variant RelocVariant // variation on Type, currently used only on PPC64 and S390X
}
func (r *Reloc) InitExt() {
if r.RelocExt == nil {
r.RelocExt = new(RelocExt)
}
}
// RelocVariant is a linker-internal variation on a relocation.
type RelocVariant uint8
const (
RV_NONE RelocVariant = iota
RV_POWER_LO
RV_POWER_HI
RV_POWER_HA
RV_POWER_DS
// RV_390_DBL is a s390x-specific relocation variant that indicates that
// the value to be placed into the relocatable field should first be
// divided by 2.
RV_390_DBL
RV_CHECK_OVERFLOW RelocVariant = 1 << 7
RV_TYPE_MASK RelocVariant = RV_CHECK_OVERFLOW - 1
)
func RelocName(arch *sys.Arch, r objabi.RelocType) string {
// We didn't have some relocation types at Go1.4.
// Uncomment code when we include those in bootstrap code.
switch {
case r >= objabi.MachoRelocOffset: // Mach-O
// nr := (r - objabi.MachoRelocOffset)>>1
// switch ctxt.Arch.Family {
// case sys.AMD64:
// return macho.RelocTypeX86_64(nr).String()
// case sys.ARM:
// return macho.RelocTypeARM(nr).String()
// case sys.ARM64:
// return macho.RelocTypeARM64(nr).String()
// case sys.I386:
// return macho.RelocTypeGeneric(nr).String()
// default:
// panic("unreachable")
// }
case r >= objabi.ElfRelocOffset: // ELF
nr := r - objabi.ElfRelocOffset
switch arch.Family {
case sys.AMD64:
return elf.R_X86_64(nr).String()
case sys.ARM:
return elf.R_ARM(nr).String()
case sys.ARM64:
return elf.R_AARCH64(nr).String()
case sys.I386:
return elf.R_386(nr).String()
case sys.MIPS, sys.MIPS64:
return elf.R_MIPS(nr).String()
case sys.PPC64:
return elf.R_PPC64(nr).String()
case sys.S390X:
return elf.R_390(nr).String()
default:
panic("unreachable")
}
}
return r.String()
}
// RelocByOff implements sort.Interface for sorting relocations by offset.
type RelocByOff []Reloc
func (x RelocByOff) Len() int { return len(x) }
func (x RelocByOff) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
func (x RelocByOff) Less(i, j int) bool {
a := &x[i]
b := &x[j]
if a.Off < b.Off {
return true
}
if a.Off > b.Off {
return false
}
return false
}