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https://github.com/golang/go
synced 2024-10-04 20:21:22 -06:00
e84d9e1fb3
Split stack checks (morestack) corrupt g->sched, but g->sched must be preserved consistent for GC/traceback. The change implements runtime.notetsleepg function, which does entersyscall/exitsyscall and is carefully arranged to not call any split functions in between. R=rsc CC=golang-dev https://golang.org/cl/11575044
349 lines
9.5 KiB
C
349 lines
9.5 KiB
C
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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#include "runtime.h"
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#include "arch_GOARCH.h"
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#include "malloc.h"
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#include "stack.h"
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enum
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{
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StackDebug = 0,
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};
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typedef struct StackCacheNode StackCacheNode;
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struct StackCacheNode
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{
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StackCacheNode *next;
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void* batch[StackCacheBatch-1];
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};
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static StackCacheNode *stackcache;
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static Lock stackcachemu;
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// stackcacherefill/stackcacherelease implement a global cache of stack segments.
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// The cache is required to prevent unlimited growth of per-thread caches.
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static void
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stackcacherefill(void)
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{
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StackCacheNode *n;
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int32 i, pos;
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runtime·lock(&stackcachemu);
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n = stackcache;
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if(n)
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stackcache = n->next;
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runtime·unlock(&stackcachemu);
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if(n == nil) {
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n = (StackCacheNode*)runtime·SysAlloc(FixedStack*StackCacheBatch);
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if(n == nil)
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runtime·throw("out of memory (stackcacherefill)");
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runtime·xadd64(&mstats.stacks_sys, FixedStack*StackCacheBatch);
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for(i = 0; i < StackCacheBatch-1; i++)
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n->batch[i] = (byte*)n + (i+1)*FixedStack;
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}
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pos = m->stackcachepos;
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for(i = 0; i < StackCacheBatch-1; i++) {
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m->stackcache[pos] = n->batch[i];
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pos = (pos + 1) % StackCacheSize;
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}
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m->stackcache[pos] = n;
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pos = (pos + 1) % StackCacheSize;
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m->stackcachepos = pos;
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m->stackcachecnt += StackCacheBatch;
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}
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static void
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stackcacherelease(void)
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{
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StackCacheNode *n;
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uint32 i, pos;
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pos = (m->stackcachepos - m->stackcachecnt) % StackCacheSize;
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n = (StackCacheNode*)m->stackcache[pos];
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pos = (pos + 1) % StackCacheSize;
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for(i = 0; i < StackCacheBatch-1; i++) {
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n->batch[i] = m->stackcache[pos];
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pos = (pos + 1) % StackCacheSize;
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}
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m->stackcachecnt -= StackCacheBatch;
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runtime·lock(&stackcachemu);
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n->next = stackcache;
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stackcache = n;
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runtime·unlock(&stackcachemu);
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}
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void*
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runtime·stackalloc(uint32 n)
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{
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uint32 pos;
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void *v;
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// Stackalloc must be called on scheduler stack, so that we
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// never try to grow the stack during the code that stackalloc runs.
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// Doing so would cause a deadlock (issue 1547).
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if(g != m->g0)
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runtime·throw("stackalloc not on scheduler stack");
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// Stacks are usually allocated with a fixed-size free-list allocator,
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// but if we need a stack of non-standard size, we fall back on malloc
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// (assuming that inside malloc and GC all the stack frames are small,
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// so that we do not deadlock).
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if(n == FixedStack || m->mallocing || m->gcing) {
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if(n != FixedStack) {
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runtime·printf("stackalloc: in malloc, size=%d want %d\n", FixedStack, n);
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runtime·throw("stackalloc");
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}
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if(m->stackcachecnt == 0)
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stackcacherefill();
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pos = m->stackcachepos;
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pos = (pos - 1) % StackCacheSize;
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v = m->stackcache[pos];
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m->stackcachepos = pos;
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m->stackcachecnt--;
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m->stackinuse++;
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return v;
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}
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return runtime·mallocgc(n, 0, FlagNoProfiling|FlagNoGC|FlagNoZero|FlagNoInvokeGC);
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}
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void
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runtime·stackfree(void *v, uintptr n)
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{
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uint32 pos;
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if(n == FixedStack || m->mallocing || m->gcing) {
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if(m->stackcachecnt == StackCacheSize)
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stackcacherelease();
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pos = m->stackcachepos;
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m->stackcache[pos] = v;
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m->stackcachepos = (pos + 1) % StackCacheSize;
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m->stackcachecnt++;
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m->stackinuse--;
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return;
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}
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runtime·free(v);
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}
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// Called from runtime·lessstack when returning from a function which
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// allocated a new stack segment. The function's return value is in
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// m->cret.
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void
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runtime·oldstack(void)
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{
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Stktop *top;
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uint32 argsize;
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byte *sp, *old;
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uintptr *src, *dst, *dstend;
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G *gp;
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int64 goid;
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int32 oldstatus;
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gp = m->curg;
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top = (Stktop*)gp->stackbase;
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old = (byte*)gp->stackguard - StackGuard;
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sp = (byte*)top;
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argsize = top->argsize;
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if(StackDebug) {
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runtime·printf("runtime: oldstack gobuf={pc:%p sp:%p lr:%p} cret=%p argsize=%p\n",
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top->gobuf.pc, top->gobuf.sp, top->gobuf.lr, m->cret, (uintptr)argsize);
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}
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// gp->status is usually Grunning, but it could be Gsyscall if a stack split
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// happens during a function call inside entersyscall.
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oldstatus = gp->status;
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gp->sched = top->gobuf;
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gp->sched.ret = m->cret;
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m->cret = 0; // drop reference
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gp->status = Gwaiting;
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gp->waitreason = "stack unsplit";
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if(argsize > 0) {
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sp -= argsize;
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dst = (uintptr*)top->argp;
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dstend = dst + argsize/sizeof(*dst);
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src = (uintptr*)sp;
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while(dst < dstend)
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*dst++ = *src++;
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}
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goid = top->gobuf.g->goid; // fault if g is bad, before gogo
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USED(goid);
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gp->stackbase = top->stackbase;
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gp->stackguard = top->stackguard;
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gp->stackguard0 = gp->stackguard;
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if(top->free != 0)
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runtime·stackfree(old, top->free);
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gp->status = oldstatus;
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runtime·gogo(&gp->sched);
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}
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// Called from reflect·call or from runtime·morestack when a new
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// stack segment is needed. Allocate a new stack big enough for
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// m->moreframesize bytes, copy m->moreargsize bytes to the new frame,
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// and then act as though runtime·lessstack called the function at
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// m->morepc.
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void
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runtime·newstack(void)
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{
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int32 framesize, argsize, oldstatus;
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Stktop *top;
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byte *stk;
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uintptr sp;
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uintptr *src, *dst, *dstend;
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G *gp;
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Gobuf label;
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bool reflectcall;
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uintptr free;
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// gp->status is usually Grunning, but it could be Gsyscall if a stack split
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// happens during a function call inside entersyscall.
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gp = m->curg;
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oldstatus = gp->status;
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framesize = m->moreframesize;
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argsize = m->moreargsize;
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gp->status = Gwaiting;
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gp->waitreason = "stack split";
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reflectcall = framesize==1;
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if(reflectcall)
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framesize = 0;
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// For reflectcall the context already points to beginning of reflect·call.
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if(!reflectcall)
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runtime·rewindmorestack(&gp->sched);
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sp = gp->sched.sp;
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if(thechar == '6' || thechar == '8') {
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// The call to morestack cost a word.
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sp -= sizeof(uintptr);
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}
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if(StackDebug || sp < gp->stackguard - StackGuard) {
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runtime·printf("runtime: newstack framesize=%p argsize=%p sp=%p stack=[%p, %p]\n"
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"\tmorebuf={pc:%p sp:%p lr:%p}\n"
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"\tsched={pc:%p sp:%p lr:%p ctxt:%p}\n",
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(uintptr)framesize, (uintptr)argsize, sp, gp->stackguard - StackGuard, gp->stackbase,
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m->morebuf.pc, m->morebuf.sp, m->morebuf.lr,
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gp->sched.pc, gp->sched.sp, gp->sched.lr, gp->sched.ctxt);
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}
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if(sp < gp->stackguard - StackGuard) {
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runtime·printf("runtime: split stack overflow: %p < %p\n", sp, gp->stackguard - StackGuard);
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runtime·throw("runtime: split stack overflow");
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}
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if(argsize % sizeof(uintptr) != 0) {
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runtime·printf("runtime: stack split with misaligned argsize %d\n", argsize);
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runtime·throw("runtime: stack split argsize");
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}
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if(gp->stackguard0 == (uintptr)StackPreempt) {
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if(gp == m->g0)
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runtime·throw("runtime: preempt g0");
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if(oldstatus == Grunning && m->p == nil)
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runtime·throw("runtime: g is running but p is not");
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if(oldstatus == Gsyscall && m->locks == 0)
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runtime·throw("runtime: stack split during syscall");
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// Be conservative about where we preempt.
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// We are interested in preempting user Go code, not runtime code.
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if(oldstatus != Grunning || m->locks || m->mallocing || m->gcing || m->p->status != Prunning) {
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// Let the goroutine keep running for now.
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// gp->preempt is set, so it will be preempted next time.
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gp->stackguard0 = gp->stackguard;
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gp->status = oldstatus;
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runtime·gogo(&gp->sched); // never return
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}
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// Act like goroutine called runtime.Gosched.
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gp->status = oldstatus;
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runtime·gosched0(gp); // never return
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}
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if(reflectcall && m->morebuf.sp - sizeof(Stktop) - argsize - 32 > gp->stackguard) {
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// special case: called from reflect.call (framesize==1)
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// to call code with an arbitrary argument size,
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// and we have enough space on the current stack.
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// the new Stktop* is necessary to unwind, but
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// we don't need to create a new segment.
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top = (Stktop*)(m->morebuf.sp - sizeof(*top));
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stk = (byte*)gp->stackguard - StackGuard;
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free = 0;
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} else {
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// allocate new segment.
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framesize += argsize;
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framesize += StackExtra; // room for more functions, Stktop.
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if(framesize < StackMin)
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framesize = StackMin;
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framesize += StackSystem;
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stk = runtime·stackalloc(framesize);
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top = (Stktop*)(stk+framesize-sizeof(*top));
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free = framesize;
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}
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if(StackDebug) {
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runtime·printf("\t-> new stack [%p, %p]\n", stk, top);
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}
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top->stackbase = gp->stackbase;
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top->stackguard = gp->stackguard;
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top->gobuf = m->morebuf;
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top->argp = m->moreargp;
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top->argsize = argsize;
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top->free = free;
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m->moreargp = nil;
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m->morebuf.pc = (uintptr)nil;
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m->morebuf.lr = (uintptr)nil;
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m->morebuf.sp = (uintptr)nil;
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// copy flag from panic
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top->panic = gp->ispanic;
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gp->ispanic = false;
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gp->stackbase = (uintptr)top;
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gp->stackguard = (uintptr)stk + StackGuard;
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gp->stackguard0 = gp->stackguard;
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sp = (uintptr)top;
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if(argsize > 0) {
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sp -= argsize;
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dst = (uintptr*)sp;
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dstend = dst + argsize/sizeof(*dst);
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src = (uintptr*)top->argp;
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while(dst < dstend)
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*dst++ = *src++;
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}
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if(thechar == '5') {
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// caller would have saved its LR below args.
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sp -= sizeof(void*);
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*(void**)sp = nil;
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}
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// Continue as if lessstack had just called m->morepc
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// (the PC that decided to grow the stack).
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runtime·memclr((byte*)&label, sizeof label);
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label.sp = sp;
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label.pc = (uintptr)runtime·lessstack;
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label.g = m->curg;
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if(reflectcall)
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runtime·gostartcallfn(&label, (FuncVal*)m->cret);
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else {
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runtime·gostartcall(&label, (void(*)(void))gp->sched.pc, gp->sched.ctxt);
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gp->sched.ctxt = nil;
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}
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gp->status = oldstatus;
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runtime·gogo(&label);
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*(int32*)345 = 123; // never return
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}
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// adjust Gobuf as if it executed a call to fn
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// and then did an immediate gosave.
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void
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runtime·gostartcallfn(Gobuf *gobuf, FuncVal *fv)
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{
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runtime·gostartcall(gobuf, fv->fn, fv);
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}
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