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cmd/internal/obj/ppc64: avoid calling morestack via a PLT when dynamically linking 

Change-Id: Ie79f72786b1d7154f1910e717a0faf354b913b89
Reviewed-on: https://go-review.googlesource.com/15970
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Michael Hudson-Doyle 2015-10-16 20:50:59 +13:00
parent 2ac993107f
commit 64fbca41c8
1 changed files with 51 additions and 8 deletions
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59
src/cmd/internal/obj/ppc64/obj9.go
View File

@ -940,19 +940,62 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
q.Pcond = p
}
// BL runtime.morestack(SB)
p = obj.Appendp(ctxt, p)
p.As = ABL
p.To.Type = obj.TYPE_BRANCH
var morestacksym *obj.LSym
if ctxt.Cursym.Cfunc != 0 {
p.To.Sym = obj.Linklookup(ctxt, "runtime.morestackc", 0)
morestacksym = obj.Linklookup(ctxt, "runtime.morestackc", 0)
} else if ctxt.Cursym.Text.From3.Offset&obj.NEEDCTXT == 0 {
p.To.Sym = obj.Linklookup(ctxt, "runtime.morestack_noctxt", 0)
morestacksym = obj.Linklookup(ctxt, "runtime.morestack_noctxt", 0)
} else {
p.To.Sym = obj.Linklookup(ctxt, "runtime.morestack", 0)
morestacksym = obj.Linklookup(ctxt, "runtime.morestack", 0)
}
if ctxt.Flag_dynlink {
// Avoid calling morestack via a PLT when dynamically linking. The
// PLT stubs generated by the system linker on ppc64le when "std r2,
// 24(r1)" to save the TOC pointer in their callers stack
// frame. Unfortunately (and necessarily) morestack is called before
// the function that calls it sets up its frame and so the PLT ends
// up smashing the saved TOC pointer for its caller's caller.
//
// According to the ABI documentation there is a mechanism to avoid
// the TOC save that the PLT stub does (put a R_PPC64_TOCSAVE
// relocation on the nop after the call to morestack) but at the time
// of writing it is not supported at all by gold and my attempt to
// use it with ld.bfd caused an internal linker error. So this hack
// seems preferable.
// MOVD $runtime.morestack(SB), R12
p = obj.Appendp(ctxt, p)
p.As = AMOVD
p.From.Type = obj.TYPE_MEM
p.From.Sym = morestacksym
p.From.Name = obj.NAME_GOTREF
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_R12
// MOVD R12, CTR
p = obj.Appendp(ctxt, p)
p.As = AMOVD
p.From.Type = obj.TYPE_REG
p.From.Reg = REG_R12
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_CTR
// BL CTR
p = obj.Appendp(ctxt, p)
p.As = obj.ACALL
p.From.Type = obj.TYPE_REG
p.From.Reg = REG_R12
p.To.Type = obj.TYPE_REG
p.To.Reg = REG_CTR
} else {
// BL runtime.morestack(SB)
p = obj.Appendp(ctxt, p)
p.As = ABL
p.To.Type = obj.TYPE_BRANCH
p.To.Sym = morestacksym
}
// BR start
p = obj.Appendp(ctxt, p)