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Revert "runtime, cmd: rationalize StackLimit and StackGuard"
This reverts commit CL 486380. Submitted out of order and breaks bootstrap. Change-Id: I67bd225094b5c9713b97f70feba04d2c99b7da76 Reviewed-on: https://go-review.googlesource.com/c/go/+/486916 Reviewed-by: David Chase <drchase@google.com> TryBot-Bypass: Austin Clements <austin@google.com>
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@ -9,9 +9,18 @@ import (
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"internal/buildcfg"
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)
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func StackNosplit(race bool) int {
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// This arithmetic must match that in runtime/stack.go:stackNosplit.
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return abi.StackNosplitBase * stackGuardMultiplier(race)
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// For the linkers. Must match Go definitions.
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const (
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STACKSYSTEM = 0
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StackSystem = STACKSYSTEM
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)
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func StackLimit(race bool) int {
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// This arithmetic must match that in runtime/stack.go:{_StackGuard,_StackLimit}.
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stackGuard := 928*stackGuardMultiplier(race) + StackSystem
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stackLimit := stackGuard - StackSystem - abi.StackSmall
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return stackLimit
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}
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// stackGuardMultiplier returns a multiplier to apply to the default
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@ -61,7 +61,7 @@ func (ctxt *Link) doStackCheck() {
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// The call to morestack in every splittable function ensures
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// that there are at least StackLimit bytes available below SP
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// when morestack returns.
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limit := objabi.StackNosplit(*flagRace) - sc.callSize
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limit := objabi.StackLimit(*flagRace) - sc.callSize
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if buildcfg.GOARCH == "arm64" {
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// Need an extra 8 bytes below SP to save FP.
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limit -= 8
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@ -5,14 +5,6 @@
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package abi
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const (
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// StackNosplitBase is the base maximum number of bytes that a chain of
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// NOSPLIT functions can use.
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//
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// This value must be multiplied by the stack guard multiplier, so do not
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// use it directly. See runtime/stack.go:stackNosplit and
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// cmd/internal/objabi/stack.go:StackNosplit.
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StackNosplitBase = 800
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// We have three different sequences for stack bounds checks, depending on
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// whether the stack frame of a function is small, big, or huge.
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@ -320,7 +320,7 @@ func init() {
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total += funcMaxSPDelta(f)
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// Add some overhead for return PCs, etc.
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asyncPreemptStack = uintptr(total) + 8*goarch.PtrSize
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if asyncPreemptStack > stackNosplit {
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if asyncPreemptStack > _StackLimit {
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// We need more than the nosplit limit. This isn't
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// unsafe, but it may limit asynchronous preemption.
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//
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@ -85,18 +85,19 @@ const (
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_FixedStack6 = _FixedStack5 | (_FixedStack5 >> 16)
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_FixedStack = _FixedStack6 + 1
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// stackNosplit is the maximum number of bytes that a chain of NOSPLIT
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// functions can use.
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// This arithmetic must match that in cmd/internal/objabi/stack.go:StackNosplit.
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stackNosplit = abi.StackNosplitBase * sys.StackGuardMultiplier
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// The stack guard is a pointer this many bytes above the
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// bottom of the stack.
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//
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// The guard leaves enough room for a stackNosplit chain of NOSPLIT calls
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// plus one stackSmall frame plus stackSystem bytes for the OS.
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// The guard leaves enough room for one _StackSmall frame plus
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// a _StackLimit chain of NOSPLIT calls plus _StackSystem
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// bytes for the OS.
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// This arithmetic must match that in cmd/internal/objabi/stack.go:StackLimit.
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_StackGuard = stackNosplit + _StackSystem + abi.StackSmall
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_StackGuard = 928*sys.StackGuardMultiplier + _StackSystem
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// The maximum number of bytes that a chain of NOSPLIT
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// functions can use.
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// This arithmetic must match that in cmd/internal/objabi/stack.go:StackLimit.
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_StackLimit = _StackGuard - _StackSystem - abi.StackSmall
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)
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const (
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@ -1210,7 +1211,7 @@ func shrinkstack(gp *g) {
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// down to the SP plus the stack guard space that ensures
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// there's room for nosplit functions.
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avail := gp.stack.hi - gp.stack.lo
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if used := gp.stack.hi - gp.sched.sp + stackNosplit; used >= avail/4 {
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if used := gp.stack.hi - gp.sched.sp + _StackLimit; used >= avail/4 {
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return
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}
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@ -342,15 +342,22 @@ TestCases:
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nosplit := m[3]
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body := m[4]
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// The limit was originally 128 but is now 800.
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// The limit was originally 128 but is now 800 (928-128).
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// Instead of rewriting the test cases above, adjust
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// the first nosplit frame to use up the extra bytes.
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// This isn't exactly right because we could have
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// nosplit -> split -> nosplit, but it's good enough.
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if !adjusted && nosplit != "" {
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const stackNosplitBase = 800 // internal/abi.StackNosplitBase
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adjusted = true
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size += stackNosplitBase - 128
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size += (928 - 128) - 128
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// Noopt builds have a larger stackguard.
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// See ../src/cmd/dist/buildruntime.go:stackGuardMultiplier
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// This increase is included in objabi.StackGuard
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for _, s := range strings.Split(os.Getenv("GO_GCFLAGS"), " ") {
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if s == "-N" {
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size += 928
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}
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}
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}
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if nosplit != "" {
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