diff options
| -rw-r--r-- | src/cmd/compile/internal/gc/plive.go | 118 | ||||
| -rw-r--r-- | src/cmd/compile/internal/gc/ssa.go | 19 | ||||
| -rw-r--r-- | src/cmd/compile/internal/ssa/func.go | 11 | ||||
| -rw-r--r-- | test/fixedbugs/issue40629.go | 69 |
4 files changed, 99 insertions, 118 deletions
diff --git a/src/cmd/compile/internal/gc/plive.go b/src/cmd/compile/internal/gc/plive.go index 7e1c0c1a95..bdb458015f 100644 --- a/src/cmd/compile/internal/gc/plive.go +++ b/src/cmd/compile/internal/gc/plive.go @@ -140,24 +140,14 @@ type Liveness struct { regMaps []liveRegMask cache progeffectscache - - // These are only populated if open-coded defers are being used. - // List of vars/stack slots storing defer args - openDeferVars []openDeferVarInfo - // Map from defer arg OpVarDef to the block where the OpVarDef occurs. - openDeferVardefToBlockMap map[*Node]*ssa.Block - // Map of blocks that cannot reach a return or exit (panic) - nonReturnBlocks map[*ssa.Block]bool -} - -type openDeferVarInfo struct { - n *Node // Var/stack slot storing a defer arg - varsIndex int // Index of variable in lv.vars } // LivenessMap maps from *ssa.Value to LivenessIndex. type LivenessMap struct { vals map[ssa.ID]LivenessIndex + // The set of live, pointer-containing variables at the deferreturn + // call (only set when open-coded defers are used). + deferreturn LivenessIndex } func (m *LivenessMap) reset() { @@ -168,6 +158,7 @@ func (m *LivenessMap) reset() { delete(m.vals, k) } } + m.deferreturn = LivenessInvalid } func (m *LivenessMap) set(v *ssa.Value, i LivenessIndex) { @@ -542,7 +533,7 @@ func newliveness(fn *Node, f *ssa.Func, vars []*Node, idx map[*Node]int32, stkpt if cap(lc.be) >= f.NumBlocks() { lv.be = lc.be[:f.NumBlocks()] } - lv.livenessMap = LivenessMap{lc.livenessMap.vals} + lv.livenessMap = LivenessMap{vals: lc.livenessMap.vals, deferreturn: LivenessInvalid} lc.livenessMap.vals = nil } if lv.be == nil { @@ -893,58 +884,12 @@ func (lv *Liveness) hasStackMap(v *ssa.Value) bool { func (lv *Liveness) prologue() { lv.initcache() - if lv.fn.Func.HasDefer() && !lv.fn.Func.OpenCodedDeferDisallowed() { - lv.openDeferVardefToBlockMap = make(map[*Node]*ssa.Block) - for i, n := range lv.vars { - if n.Name.OpenDeferSlot() { - lv.openDeferVars = append(lv.openDeferVars, openDeferVarInfo{n: n, varsIndex: i}) - } - } - - // Find any blocks that cannot reach a return or a BlockExit - // (panic) -- these must be because of an infinite loop. - reachesRet := make(map[ssa.ID]bool) - blockList := make([]*ssa.Block, 0, 256) - - for _, b := range lv.f.Blocks { - if b.Kind == ssa.BlockRet || b.Kind == ssa.BlockRetJmp || b.Kind == ssa.BlockExit { - blockList = append(blockList, b) - } - } - - for len(blockList) > 0 { - b := blockList[0] - blockList = blockList[1:] - if reachesRet[b.ID] { - continue - } - reachesRet[b.ID] = true - for _, e := range b.Preds { - blockList = append(blockList, e.Block()) - } - } - - lv.nonReturnBlocks = make(map[*ssa.Block]bool) - for _, b := range lv.f.Blocks { - if !reachesRet[b.ID] { - lv.nonReturnBlocks[b] = true - //fmt.Println("No reach ret", lv.f.Name, b.ID, b.Kind) - } - } - } - for _, b := range lv.f.Blocks { be := lv.blockEffects(b) // Walk the block instructions backward and update the block // effects with the each prog effects. for j := len(b.Values) - 1; j >= 0; j-- { - if b.Values[j].Op == ssa.OpVarDef { - n := b.Values[j].Aux.(*Node) - if n.Name.OpenDeferSlot() { - lv.openDeferVardefToBlockMap[n] = b - } - } pos, e := lv.valueEffects(b.Values[j]) regUevar, regKill := lv.regEffects(b.Values[j]) if e&varkill != 0 { @@ -961,20 +906,6 @@ func (lv *Liveness) prologue() { } } -// markDeferVarsLive marks each variable storing an open-coded defer arg as -// specially live in block b if the variable definition dominates block b. -func (lv *Liveness) markDeferVarsLive(b *ssa.Block, newliveout *varRegVec) { - // Only force computation of dominators if we have a block where we need - // to specially mark defer args live. - sdom := lv.f.Sdom() - for _, info := range lv.openDeferVars { - defB := lv.openDeferVardefToBlockMap[info.n] - if sdom.IsAncestorEq(defB, b) { - newliveout.vars.Set(int32(info.varsIndex)) - } - } -} - // Solve the liveness dataflow equations. func (lv *Liveness) solve() { // These temporary bitvectors exist to avoid successive allocations and @@ -1018,23 +949,6 @@ func (lv *Liveness) solve() { } } - if lv.fn.Func.HasDefer() && !lv.fn.Func.OpenCodedDeferDisallowed() && - (b.Kind == ssa.BlockExit || lv.nonReturnBlocks[b]) { - // Open-coded defer args slots must be live - // everywhere in a function, since a panic can - // occur (almost) anywhere. Force all appropriate - // defer arg slots to be live in BlockExit (panic) - // blocks and in blocks that do not reach a return - // (because of infinite loop). - // - // We are assuming that the defer exit code at - // BlockReturn/BlockReturnJmp accesses all of the - // defer args (with pointers), and so keeps them - // live. This analysis may have to be adjusted if - // that changes (because of optimizations). - lv.markDeferVarsLive(b, &newliveout) - } - if !be.liveout.Eq(newliveout) { change = true be.liveout.Copy(newliveout) @@ -1087,6 +1001,17 @@ func (lv *Liveness) epilogue() { n.Name.SetNeedzero(true) livedefer.Set(int32(i)) } + if n.Name.OpenDeferSlot() { + // Open-coded defer args slots must be live + // everywhere in a function, since a panic can + // occur (almost) anywhere. Because it is live + // everywhere, it must be zeroed on entry. + livedefer.Set(int32(i)) + // It was already marked as Needzero when created. + if !n.Name.Needzero() { + Fatalf("all pointer-containing defer arg slots should have Needzero set") + } + } } } @@ -1188,6 +1113,17 @@ func (lv *Liveness) epilogue() { lv.compact(b) } + // If we have an open-coded deferreturn call, make a liveness map for it. + if lv.fn.Func.OpenCodedDeferDisallowed() { + lv.livenessMap.deferreturn = LivenessInvalid + } else { + lv.livenessMap.deferreturn = LivenessIndex{ + stackMapIndex: lv.stackMapSet.add(livedefer), + regMapIndex: 0, // entry regMap, containing no live registers + isUnsafePoint: false, + } + } + // Done compacting. Throw out the stack map set. lv.stackMaps = lv.stackMapSet.extractUniqe() lv.stackMapSet = bvecSet{} diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go index d4d23a2956..5d0098b4e6 100644 --- a/src/cmd/compile/internal/gc/ssa.go +++ b/src/cmd/compile/internal/gc/ssa.go @@ -4318,12 +4318,6 @@ func (s *state) openDeferExit() { } } - if i == len(s.openDefers)-1 { - // Record the call of the first defer. This will be used - // to set liveness info for the deferreturn (which is also - // used for any location that causes a runtime panic) - s.f.LastDeferExit = call - } s.endBlock() s.startBlock(bEnd) } @@ -5807,11 +5801,6 @@ type SSAGenState struct { // wasm: The number of values on the WebAssembly stack. This is only used as a safeguard. OnWasmStackSkipped int - - // Liveness index for the first function call in the final defer exit code - // path that we generated. All defer functions and args should be live at - // this point. This will be used to set the liveness for the deferreturn. - lastDeferLiveness LivenessIndex } // Prog appends a new Prog. @@ -6056,12 +6045,6 @@ func genssa(f *ssa.Func, pp *Progs) { // instruction. s.pp.nextLive = s.livenessMap.Get(v) - // Remember the liveness index of the first defer call of - // the last defer exit - if v.Block.Func.LastDeferExit != nil && v == v.Block.Func.LastDeferExit { - s.lastDeferLiveness = s.pp.nextLive - } - // Special case for first line in function; move it to the start. if firstPos != src.NoXPos { s.SetPos(firstPos) @@ -6122,7 +6105,7 @@ func genssa(f *ssa.Func, pp *Progs) { // When doing open-coded defers, generate a disconnected call to // deferreturn and a return. This will be used to during panic // recovery to unwind the stack and return back to the runtime. - s.pp.nextLive = s.lastDeferLiveness + s.pp.nextLive = s.livenessMap.deferreturn gencallret(pp, Deferreturn) } diff --git a/src/cmd/compile/internal/ssa/func.go b/src/cmd/compile/internal/ssa/func.go index 7cf72a8e37..4b9189fb3e 100644 --- a/src/cmd/compile/internal/ssa/func.go +++ b/src/cmd/compile/internal/ssa/func.go @@ -33,15 +33,8 @@ type Func struct { Blocks []*Block // unordered set of all basic blocks (note: not indexable by ID) Entry *Block // the entry basic block - // If we are using open-coded defers, this is the first call to a deferred - // function in the final defer exit sequence that we generated. This call - // should be after all defer statements, and will have all args, etc. of - // all defer calls as live. The liveness info of this call will be used - // for the deferreturn/ret segment generated for functions with open-coded - // defers. - LastDeferExit *Value - bid idAlloc // block ID allocator - vid idAlloc // value ID allocator + bid idAlloc // block ID allocator + vid idAlloc // value ID allocator // Given an environment variable used for debug hash match, // what file (if any) receives the yes/no logging? diff --git a/test/fixedbugs/issue40629.go b/test/fixedbugs/issue40629.go new file mode 100644 index 0000000000..c6ef408f49 --- /dev/null +++ b/test/fixedbugs/issue40629.go @@ -0,0 +1,69 @@ +// run + +// Copyright 2020 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package main + +import "fmt" + +const N = 40 + +func main() { + var x [N]int // stack-allocated memory + for i := range x { + x[i] = 0x999 + } + + // This defer checks to see if x is uncorrupted. + defer func(p *[N]int) { + recover() + for i := range p { + if p[i] != 0x999 { + for j := range p { + fmt.Printf("p[%d]=0x%x\n", j, p[j]) + } + panic("corrupted stack variable") + } + } + }(&x) + + // This defer starts a new goroutine, which will (hopefully) + // overwrite x on the garbage stack. + defer func() { + c := make(chan bool) + go func() { + useStack(1000) + c <- true + }() + <-c + + }() + + // This defer causes a stack copy. + // The old stack is now garbage. + defer func() { + useStack(1000) + }() + + // Trigger a segfault. + *g = 0 + + // Make the return statement unreachable. + // That makes the stack map at the deferreturn call empty. + // In particular, the argument to the first defer is not + // marked as a pointer, so it doesn't get adjusted + // during the stack copy. + for { + } +} + +var g *int64 + +func useStack(n int) { + if n == 0 { + return + } + useStack(n - 1) +} |