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[dev.link] cmd/link: add loader support for recording ElfType for symbols

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Add hooks in the loader for recording the ElfType of a symbol, as a
replacement for the sym.Symbol ElfType() and SetElfType() methods.
This symbol property is set only for symbols read from shared
libraries by ldshlibsyms.

Change-Id: I3a3c193c3718dcfb73a2364d6e19e0419dab5b41
Reviewed-on: https://go-review.googlesource.com/c/go/+/213420
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
This commit is contained in:
Than McIntosh 2020-01-03 15:17:26 -05:00
parent db48d45838
commit ce7a0dda31
1 changed files with 38 additions and 4 deletions
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42
src/cmd/link/internal/loader/loader.go
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@ -13,6 +13,7 @@ import (
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/sym"
"debug/elf"
"fmt"
"log"
"math/bits"
@ -197,10 +198,11 @@ type Loader struct {
align map[Sym]int32 // stores alignment for symbols
dynimplib map[Sym]string // stores Dynimplib symbol attribute
dynimpvers map[Sym]string // stores Dynimpvers symbol attribute
localentry map[Sym]uint8 // stores Localentry symbol attribute
extname map[Sym]string // stores Extname symbol attribute
dynimplib map[Sym]string // stores Dynimplib symbol attribute
dynimpvers map[Sym]string // stores Dynimpvers symbol attribute
localentry map[Sym]uint8 // stores Localentry symbol attribute
extname map[Sym]string // stores Extname symbol attribute
elfType map[Sym]elf.SymType // stores elf type symbol property
// Used to implement field tracking; created during deadcode if
// field tracking is enabled. Reachparent[K] contains the index of
@ -250,6 +252,7 @@ func NewLoader(flags uint32, elfsetstring elfsetstringFunc) *Loader {
localentry: make(map[Sym]uint8),
extname: make(map[Sym]string),
attrReadOnly: make(map[Sym]bool),
elfType: make(map[Sym]elf.SymType),
attrTopFrame: make(map[Sym]struct{}),
attrSpecial: make(map[Sym]struct{}),
attrCgoExportDynamic: make(map[Sym]struct{}),
@ -1137,6 +1140,30 @@ func (l *Loader) SetSymExtname(i Sym, value string) {
}
}
// SymElfType returns the previously recorded ELF type for a symbol
// (used only for symbols read from shared libraries by ldshlibsyms).
// It is not set for symbols defined by the packages being linked or
// by symbols read by ldelf (and so is left as elf.STT_NOTYPE).
func (l *Loader) SymElfType(i Sym) elf.SymType {
if et, ok := l.elfType[i]; ok {
return et
}
return elf.STT_NOTYPE
}
// SetSymElfType sets the elf type attribute for a symbol.
func (l *Loader) SetSymElfType(i Sym, et elf.SymType) {
// reject bad symbols
if i > l.max || i == 0 {
panic("bad symbol index in SetSymElfType")
}
if et == elf.STT_NOTYPE {
delete(l.elfType, i)
} else {
l.elfType[i] = et
}
}
// SymLocalentry returns the "local entry" value for the specified
// symbol.
func (l *Loader) SymLocalentry(i Sym) uint8 {
@ -1633,6 +1660,11 @@ func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols) {
if l.SymDynimpvers(i) != "" {
s.SetDynimpvers(l.SymDynimpvers(i))
}
// Copy ELF type if set.
if et, ok := l.elfType[i]; ok {
s.SetElfType(et)
}
}
// load contents of defined symbols
@ -1780,6 +1812,8 @@ func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) int {
}
s := l.addNewSym(istart+Sym(i), name, ver, r.unit, t)
// NB: this is an incomplete set of attributes; a more complete
// attribute migration appears in a subsequent patch.
s.Attr.Set(sym.AttrReachable, l.attrReachable.has(istart+Sym(i)))
nr += r.NReloc(i)
}