func addstacksplit(ctxt *liblink.Link, cursym *liblink.LSym) {
var p *liblink.Prog
var q *liblink.Prog
var p1 *liblink.Prog
var p2 *liblink.Prog
var autoffset int32
var deltasp int32
var a int
if ctxt.Symmorestack[0] == nil {
ctxt.Symmorestack[0] = liblink.Linklookup(ctxt, "runtime.morestack", 0)
ctxt.Symmorestack[1] = liblink.Linklookup(ctxt, "runtime.morestack_noctxt", 0)
}
if ctxt.Headtype == liblink.Hplan9 && ctxt.Plan9privates == nil {
ctxt.Plan9privates = liblink.Linklookup(ctxt, "_privates", 0)
}
ctxt.Cursym = cursym
if cursym.Text == nil || cursym.Text.Link == nil {
return
}
p = cursym.Text
autoffset = int32(p.To.Offset)
if autoffset < 0 {
autoffset = 0
}
cursym.Locals = autoffset
cursym.Args = p.To.Offset2
q = nil
if !(p.From.Scale&liblink.NOSPLIT != 0) || (p.From.Scale&liblink.WRAPPER != 0) {
p = liblink.Appendp(ctxt, p)
p = load_g_cx(ctxt, p) // load g into CX
}
if !(cursym.Text.From.Scale&liblink.NOSPLIT != 0) {
p = stacksplit(ctxt, p, autoffset, bool2int(!(cursym.Text.From.Scale&liblink.NEEDCTXT != 0)), &q) // emit split check
}
if autoffset != 0 {
p = liblink.Appendp(ctxt, p)
p.As = AADJSP
p.From.Type_ = D_CONST
p.From.Offset = int64(autoffset)
p.Spadj = autoffset
} else {
// zero-byte stack adjustment.
// Insert a fake non-zero adjustment so that stkcheck can
// recognize the end of the stack-splitting prolog.
p = liblink.Appendp(ctxt, p)
p.As = ANOP
p.Spadj = int32(-ctxt.Arch.Ptrsize)
p = liblink.Appendp(ctxt, p)
p.As = ANOP
p.Spadj = int32(ctxt.Arch.Ptrsize)
}
if q != nil {
q.Pcond = p
}
deltasp = autoffset
if cursym.Text.From.Scale&liblink.WRAPPER != 0 {
// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
//
// MOVL g_panic(CX), BX
// TESTL BX, BX
// JEQ end
// LEAL (autoffset+4)(SP), DI
// CMPL panic_argp(BX), DI
// JNE end
// MOVL SP, panic_argp(BX)
// end:
// NOP
//
// The NOP is needed to give the jumps somewhere to land.
// It is a liblink NOP, not an x86 NOP: it encodes to 0 instruction bytes.
p = liblink.Appendp(ctxt, p)
p.As = AMOVL
p.From.Type_ = D_INDIR + D_CX
p.From.Offset = 4 * int64(ctxt.Arch.Ptrsize) // G.panic
p.To.Type_ = D_BX
p = liblink.Appendp(ctxt, p)
p.As = ATESTL
p.From.Type_ = D_BX
p.To.Type_ = D_BX
p = liblink.Appendp(ctxt, p)
p.As = AJEQ
p.To.Type_ = D_BRANCH
p1 = p
p = liblink.Appendp(ctxt, p)
p.As = ALEAL
p.From.Type_ = D_INDIR + D_SP
p.From.Offset = int64(autoffset) + 4
p.To.Type_ = D_DI
p = liblink.Appendp(ctxt, p)
p.As = ACMPL
p.From.Type_ = D_INDIR + D_BX
p.From.Offset = 0 // Panic.argp
p.To.Type_ = D_DI
p = liblink.Appendp(ctxt, p)
p.As = AJNE
p.To.Type_ = D_BRANCH
p2 = p
p = liblink.Appendp(ctxt, p)
p.As = AMOVL
p.From.Type_ = D_SP
p.To.Type_ = D_INDIR + D_BX
p.To.Offset = 0 // Panic.argp
p = liblink.Appendp(ctxt, p)
p.As = ANOP
p1.Pcond = p
p2.Pcond = p
}
if ctxt.Debugzerostack != 0 && autoffset != 0 && !(cursym.Text.From.Scale&liblink.NOSPLIT != 0) {
// 8l -Z means zero the stack frame on entry.
// This slows down function calls but can help avoid
// false positives in garbage collection.
p = liblink.Appendp(ctxt, p)
p.As = AMOVL
p.From.Type_ = D_SP
p.To.Type_ = D_DI
p = liblink.Appendp(ctxt, p)
p.As = AMOVL
p.From.Type_ = D_CONST
p.From.Offset = int64(autoffset) / 4
p.To.Type_ = D_CX
p = liblink.Appendp(ctxt, p)
p.As = AMOVL
p.From.Type_ = D_CONST
p.From.Offset = 0
p.To.Type_ = D_AX
p = liblink.Appendp(ctxt, p)
p.As = AREP
p = liblink.Appendp(ctxt, p)
p.As = ASTOSL
}
for ; p != nil; p = p.Link {
a = int(p.From.Type_)
if a == D_AUTO {
p.From.Offset += int64(deltasp)
}
if a == D_PARAM {
p.From.Offset += int64(deltasp) + 4
}
a = int(p.To.Type_)
if a == D_AUTO {
p.To.Offset += int64(deltasp)
}
if a == D_PARAM {
p.To.Offset += int64(deltasp) + 4
}
switch p.As {
default:
continue
case APUSHL,
APUSHFL:
deltasp += 4
p.Spadj = 4
continue
case APUSHW,
APUSHFW:
deltasp += 2
p.Spadj = 2
continue
case APOPL,
APOPFL:
deltasp -= 4
p.Spadj = -4
continue
case APOPW,
APOPFW:
deltasp -= 2
p.Spadj = -2
continue
case ARET:
break
}
if autoffset != deltasp {
ctxt.Diag("unbalanced PUSH/POP")
}
if autoffset != 0 {
p.As = AADJSP
p.From.Type_ = D_CONST
p.From.Offset = int64(-autoffset)
p.Spadj = -autoffset
p = liblink.Appendp(ctxt, p)
p.As = ARET
// If there are instructions following
// this ARET, they come from a branch
// with the same stackframe, so undo
// the cleanup.
p.Spadj = +autoffset
}
if p.To.Sym != nil { // retjmp
p.As = AJMP
}
}
}
