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[dev.link] cmd/link: do not put static symbols into name lookup table

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Since the previous CL, we will not reference static symbols by
name. Therefore no need to put them into the name lookup table.

On Linux/ARM, in runtime/internal/atomic/sys_linux_arm.s, the
kernelcas function has a definition and a reference written in
two different forms, one with package prefix, one without. This
way, the assembler cannot know they are the same symbol, only the
linker knows. This is quite unusual, unify the names to so the
assembler can resolve it to index.

Change-Id: Ie7223097be6a3b65f3fa43ed4575da9972ef5b69
Reviewed-on: https://go-review.googlesource.com/c/go/+/201998
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Zhang 2019-10-18 11:19:32 -04:00
parent d56c8149ac
commit c480d32fad
2 changed files with 24 additions and 13 deletions
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17
src/cmd/link/internal/loader/loader.go
View File

@ -147,6 +147,12 @@ func (l *Loader) AddSym(name string, ver int, i Sym, r *oReader, dupok bool, typ
if l.extStart != 0 { if l.extStart != 0 {
panic("AddSym called after AddExtSym is called") panic("AddSym called after AddExtSym is called")
} }
if ver == r.version {
// Static symbol. Add its global index but don't
// add to name lookup table, as it cannot be
// referenced by name.
return true
}
nv := nameVer{name, ver} nv := nameVer{name, ver}
if oldi, ok := l.symsByName[nv]; ok { if oldi, ok := l.symsByName[nv]; ok {
if dupok { if dupok {
@ -294,7 +300,10 @@ func (l *Loader) IsDup(i Sym) bool {
return false return false
} }
if osym.Name == "" { if osym.Name == "" {
return false return false // Unnamed aux symbol cannot be dup.
}
if osym.ABI == goobj2.SymABIstatic {
return false // Static symbol cannot be dup.
} }
name := strings.Replace(osym.Name, "\"\".", r.pkgprefix, -1) name := strings.Replace(osym.Name, "\"\".", r.pkgprefix, -1)
ver := abiToVer(osym.ABI, r.version) ver := abiToVer(osym.ABI, r.version)
@ -656,7 +665,7 @@ func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) {
continue continue
} }
ver := abiToVer(osym.ABI, r.version) ver := abiToVer(osym.ABI, r.version)
if l.symsByName[nameVer{name, ver}] != istart+Sym(i) { if osym.ABI != goobj2.SymABIstatic && l.symsByName[nameVer{name, ver}] != istart+Sym(i) {
continue continue
} }
@ -709,8 +718,9 @@ func loadObjFull(l *Loader, r *oReader) {
} }
ver := abiToVer(osym.ABI, r.version) ver := abiToVer(osym.ABI, r.version)
dupok := osym.Dupok() dupok := osym.Dupok()
if dupok {
if dupsym := l.symsByName[nameVer{name, ver}]; dupsym != istart+Sym(i) { if dupsym := l.symsByName[nameVer{name, ver}]; dupsym != istart+Sym(i) {
if dupok && l.Reachable.Has(dupsym) { if l.Reachable.Has(dupsym) {
// A dupok symbol is resolved to another package. We still need // A dupok symbol is resolved to another package. We still need
// to record its presence in the current package, as the trampoline // to record its presence in the current package, as the trampoline
// pass expects packages are laid out in dependency order. // pass expects packages are laid out in dependency order.
@ -721,6 +731,7 @@ func loadObjFull(l *Loader, r *oReader) {
} }
continue continue
} }
}
s := l.Syms[istart+Sym(i)] s := l.Syms[istart+Sym(i)]
if s == nil { if s == nil {

4
src/runtime/internal/atomic/sys_linux_arm.s
View File

@ -29,9 +29,9 @@ TEXT runtime∕internal∕atomic·Cas(SB),NOSPLIT|NOFRAME,$0
CMP $7, R11 CMP $7, R11
BLT 2(PC) BLT 2(PC)
JMP ·armcas(SB) JMP ·armcas(SB)
JMP ·kernelcas<>(SB) JMP kernelcas<>(SB)
TEXT runtime∕internal∕atomic·kernelcas<>(SB),NOSPLIT,$0 TEXT kernelcas<>(SB),NOSPLIT,$0
MOVW ptr+0(FP), R2 MOVW ptr+0(FP), R2
// trigger potential paging fault here, // trigger potential paging fault here,
// because we don't know how to traceback through __kuser_cmpxchg // because we don't know how to traceback through __kuser_cmpxchg