Imported Upstream version 1.4upstream/1.4

1 files changed, 864 insertions, 0 deletions

diff --git a/src/runtime/heapdump.c b/src/runtime/heapdump.c
new file mode 100644
index 000000000..7eba8c005
--- /dev/null
+++ b/src/runtime/heapdump.c
@@ -0,0 +1,864 @@
+// Copyright 2014 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.
+
+// Implementation of runtime/debug.WriteHeapDump.  Writes all
+// objects in the heap plus additional info (roots, threads,
+// finalizers, etc.) to a file.
+
+// The format of the dumped file is described at
+// http://golang.org/s/go14heapdump.
+
+#include "runtime.h"
+#include "arch_GOARCH.h"
+#include "malloc.h"
+#include "mgc0.h"
+#include "type.h"
+#include "typekind.h"
+#include "funcdata.h"
+#include "zaexperiment.h"
+#include "textflag.h"
+
+extern byte runtime·data[];
+extern byte runtime·edata[];
+extern byte runtime·bss[];
+extern byte runtime·ebss[];
+
+enum {
+	FieldKindEol = 0,
+	FieldKindPtr = 1,
+	FieldKindIface = 2,
+	FieldKindEface = 3,
+
+	TagEOF = 0,
+	TagObject = 1,
+	TagOtherRoot = 2,
+	TagType = 3,
+	TagGoRoutine = 4,
+	TagStackFrame = 5,
+	TagParams = 6,
+	TagFinalizer = 7,
+	TagItab = 8,
+	TagOSThread = 9,
+	TagMemStats = 10,
+	TagQueuedFinalizer = 11,
+	TagData = 12,
+	TagBss = 13,
+	TagDefer = 14,
+	TagPanic = 15,
+	TagMemProf = 16,
+	TagAllocSample = 17,
+};
+
+static uintptr* playgcprog(uintptr offset, uintptr *prog, void (*callback)(void*,uintptr,uintptr), void *arg);
+static void dumpfields(BitVector bv);
+static void dumpbvtypes(BitVector *bv, byte *base);
+static BitVector makeheapobjbv(byte *p, uintptr size);
+
+// fd to write the dump to.
+static uintptr	dumpfd;
+
+#pragma dataflag NOPTR /* tmpbuf not a heap pointer at least */
+static byte	*tmpbuf;
+static uintptr	tmpbufsize;
+
+// buffer of pending write data
+enum {
+	BufSize = 4096,
+};
+#pragma dataflag NOPTR
+static byte buf[BufSize];
+static uintptr nbuf;
+
+static void
+write(byte *data, uintptr len)
+{
+	if(len + nbuf <= BufSize) {
+		runtime·memmove(buf + nbuf, data, len);
+		nbuf += len;
+		return;
+	}
+	runtime·write(dumpfd, buf, nbuf);
+	if(len >= BufSize) {
+		runtime·write(dumpfd, data, len);
+		nbuf = 0;
+	} else {
+		runtime·memmove(buf, data, len);
+		nbuf = len;
+	}
+}
+
+static void
+flush(void)
+{
+	runtime·write(dumpfd, buf, nbuf);
+	nbuf = 0;
+}
+
+// Cache of types that have been serialized already.
+// We use a type's hash field to pick a bucket.
+// Inside a bucket, we keep a list of types that
+// have been serialized so far, most recently used first.
+// Note: when a bucket overflows we may end up
+// serializing a type more than once.  That's ok.
+enum {
+	TypeCacheBuckets = 256, // must be a power of 2
+	TypeCacheAssoc = 4,
+};
+typedef struct TypeCacheBucket TypeCacheBucket;
+struct TypeCacheBucket {
+	Type *t[TypeCacheAssoc];
+};
+#pragma dataflag NOPTR /* only initialized and used while world is stopped */
+static TypeCacheBucket typecache[TypeCacheBuckets];
+
+// dump a uint64 in a varint format parseable by encoding/binary
+static void
+dumpint(uint64 v)
+{
+	byte buf[10];
+	int32 n;
+	n = 0;
+	while(v >= 0x80) {
+		buf[n++] = v | 0x80;
+		v >>= 7;
+	}
+	buf[n++] = v;
+	write(buf, n);
+}
+
+static void
+dumpbool(bool b)
+{
+	dumpint(b ? 1 : 0);
+}
+
+// dump varint uint64 length followed by memory contents
+static void
+dumpmemrange(byte *data, uintptr len)
+{
+	dumpint(len);
+	write(data, len);
+}
+
+static void
+dumpstr(String s)
+{
+	dumpmemrange(s.str, s.len);
+}
+
+static void
+dumpcstr(int8 *c)
+{
+	dumpmemrange((byte*)c, runtime·findnull((byte*)c));
+}
+
+// dump information for a type
+static void
+dumptype(Type *t)
+{
+	TypeCacheBucket *b;
+	int32 i, j;
+
+	if(t == nil) {
+		return;
+	}
+
+	// If we've definitely serialized the type before,
+	// no need to do it again.
+	b = &typecache[t->hash & (TypeCacheBuckets-1)];
+	if(t == b->t[0]) return;
+	for(i = 1; i < TypeCacheAssoc; i++) {
+		if(t == b->t[i]) {
+			// Move-to-front
+			for(j = i; j > 0; j--) {
+				b->t[j] = b->t[j-1];
+			}
+			b->t[0] = t;
+			return;
+		}
+	}
+	// Might not have been dumped yet.  Dump it and
+	// remember we did so.
+	for(j = TypeCacheAssoc-1; j > 0; j--) {
+		b->t[j] = b->t[j-1];
+	}
+	b->t[0] = t;
+	
+	// dump the type
+	dumpint(TagType);
+	dumpint((uintptr)t);
+	dumpint(t->size);
+	if(t->x == nil || t->x->pkgPath == nil || t->x->name == nil) {
+		dumpstr(*t->string);
+	} else {
+		dumpint(t->x->pkgPath->len + 1 + t->x->name->len);
+		write(t->x->pkgPath->str, t->x->pkgPath->len);
+		write((byte*)".", 1);
+		write(t->x->name->str, t->x->name->len);
+	}
+	dumpbool((t->kind & KindDirectIface) == 0 || (t->kind & KindNoPointers) == 0);
+}
+
+// dump an object
+static void
+dumpobj(byte *obj, uintptr size, BitVector bv)
+{
+	dumpbvtypes(&bv, obj);
+	dumpint(TagObject);
+	dumpint((uintptr)obj);
+	dumpmemrange(obj, size);
+	dumpfields(bv);
+}
+
+static void
+dumpotherroot(int8 *description, byte *to)
+{
+	dumpint(TagOtherRoot);
+	dumpcstr(description);
+	dumpint((uintptr)to);
+}
+
+static void
+dumpfinalizer(byte *obj, FuncVal *fn, Type* fint, PtrType *ot)
+{
+	dumpint(TagFinalizer);
+	dumpint((uintptr)obj);
+	dumpint((uintptr)fn);
+	dumpint((uintptr)fn->fn);
+	dumpint((uintptr)fint);
+	dumpint((uintptr)ot);
+}
+
+typedef struct ChildInfo ChildInfo;
+struct ChildInfo {
+	// Information passed up from the callee frame about
+	// the layout of the outargs region.
+	uintptr argoff;     // where the arguments start in the frame
+	uintptr arglen;     // size of args region
+	BitVector args;    // if args.n >= 0, pointer map of args region
+
+	byte *sp;           // callee sp
+	uintptr depth;      // depth in call stack (0 == most recent)
+};
+
+// dump kinds & offsets of interesting fields in bv
+static void
+dumpbv(BitVector *bv, uintptr offset)
+{
+	uintptr i;
+
+	for(i = 0; i < bv->n; i += BitsPerPointer) {
+		switch(bv->bytedata[i/8] >> i%8 & 3) {
+		case BitsDead:
+			// BitsDead has already been processed in makeheapobjbv.
+			// We should only see it in stack maps, in which case we should continue processing.
+			break;
+		case BitsScalar:
+			break;
+		case BitsPointer:
+			dumpint(FieldKindPtr);
+			dumpint(offset + i / BitsPerPointer * PtrSize);
+			break;
+		case BitsMultiWord:
+			switch(bv->bytedata[(i+BitsPerPointer)/8] >> (i+BitsPerPointer)%8 & 3) {
+			default:
+				runtime·throw("unexpected garbage collection bits");
+			case BitsIface:
+				dumpint(FieldKindIface);
+				dumpint(offset + i / BitsPerPointer * PtrSize);
+				i += BitsPerPointer;
+				break;
+			case BitsEface:
+				dumpint(FieldKindEface);
+				dumpint(offset + i / BitsPerPointer * PtrSize);
+				i += BitsPerPointer;
+				break;
+			}
+		}
+	}
+}
+
+static bool
+dumpframe(Stkframe *s, void *arg)
+{
+	Func *f;
+	ChildInfo *child;
+	uintptr pc, off, size;
+	int32 pcdata;
+	StackMap *stackmap;
+	int8 *name;
+	BitVector bv;
+
+	child = (ChildInfo*)arg;
+	f = s->fn;
+
+	// Figure out what we can about our stack map
+	pc = s->pc;
+	if(pc != f->entry)
+		pc--;
+	pcdata = runtime·pcdatavalue(f, PCDATA_StackMapIndex, pc);
+	if(pcdata == -1) {
+		// We do not have a valid pcdata value but there might be a
+		// stackmap for this function.  It is likely that we are looking
+		// at the function prologue, assume so and hope for the best.
+		pcdata = 0;
+	}
+	stackmap = runtime·funcdata(f, FUNCDATA_LocalsPointerMaps);
+
+	// Dump any types we will need to resolve Efaces.
+	if(child->args.n >= 0)
+		dumpbvtypes(&child->args, (byte*)s->sp + child->argoff);
+	if(stackmap != nil && stackmap->n > 0) {
+		bv = runtime·stackmapdata(stackmap, pcdata);
+		dumpbvtypes(&bv, (byte*)(s->varp - bv.n / BitsPerPointer * PtrSize));
+	} else {
+		bv.n = -1;
+	}
+
+	// Dump main body of stack frame.
+	dumpint(TagStackFrame);
+	dumpint(s->sp); // lowest address in frame
+	dumpint(child->depth); // # of frames deep on the stack
+	dumpint((uintptr)child->sp); // sp of child, or 0 if bottom of stack
+	dumpmemrange((byte*)s->sp, s->fp - s->sp);  // frame contents
+	dumpint(f->entry);
+	dumpint(s->pc);
+	dumpint(s->continpc);
+	name = runtime·funcname(f);
+	if(name == nil)
+		name = "unknown function";
+	dumpcstr(name);
+
+	// Dump fields in the outargs section
+	if(child->args.n >= 0) {
+		dumpbv(&child->args, child->argoff);
+	} else {
+		// conservative - everything might be a pointer
+		for(off = child->argoff; off < child->argoff + child->arglen; off += PtrSize) {
+			dumpint(FieldKindPtr);
+			dumpint(off);
+		}
+	}
+
+	// Dump fields in the local vars section
+	if(stackmap == nil) {
+		// No locals information, dump everything.
+		for(off = child->arglen; off < s->varp - s->sp; off += PtrSize) {
+			dumpint(FieldKindPtr);
+			dumpint(off);
+		}
+	} else if(stackmap->n < 0) {
+		// Locals size information, dump just the locals.
+		size = -stackmap->n;
+		for(off = s->varp - size - s->sp; off <  s->varp - s->sp; off += PtrSize) {
+			dumpint(FieldKindPtr);
+			dumpint(off);
+		}
+	} else if(stackmap->n > 0) {
+		// Locals bitmap information, scan just the pointers in
+		// locals.
+		dumpbv(&bv, s->varp - bv.n / BitsPerPointer * PtrSize - s->sp);
+	}
+	dumpint(FieldKindEol);
+
+	// Record arg info for parent.
+	child->argoff = s->argp - s->fp;
+	child->arglen = s->arglen;
+	child->sp = (byte*)s->sp;
+	child->depth++;
+	stackmap = runtime·funcdata(f, FUNCDATA_ArgsPointerMaps);
+	if(stackmap != nil)
+		child->args = runtime·stackmapdata(stackmap, pcdata);
+	else
+		child->args.n = -1;
+	return true;
+}
+
+static void
+dumpgoroutine(G *gp)
+{
+	uintptr sp, pc, lr;
+	ChildInfo child;
+	Defer *d;
+	Panic *p;
+	bool (*fn)(Stkframe*, void*);
+
+	if(gp->syscallsp != (uintptr)nil) {
+		sp = gp->syscallsp;
+		pc = gp->syscallpc;
+		lr = 0;
+	} else {
+		sp = gp->sched.sp;
+		pc = gp->sched.pc;
+		lr = gp->sched.lr;
+	}
+
+	dumpint(TagGoRoutine);
+	dumpint((uintptr)gp);
+	dumpint((uintptr)sp);
+	dumpint(gp->goid);
+	dumpint(gp->gopc);
+	dumpint(runtime·readgstatus(gp));
+	dumpbool(gp->issystem);
+	dumpbool(false);  // isbackground
+	dumpint(gp->waitsince);
+	dumpstr(gp->waitreason);
+	dumpint((uintptr)gp->sched.ctxt);
+	dumpint((uintptr)gp->m);
+	dumpint((uintptr)gp->defer);
+	dumpint((uintptr)gp->panic);
+
+	// dump stack
+	child.args.n = -1;
+	child.arglen = 0;
+	child.sp = nil;
+	child.depth = 0;
+	fn = dumpframe;
+	runtime·gentraceback(pc, sp, lr, gp, 0, nil, 0x7fffffff, &fn, &child, 0);
+
+	// dump defer & panic records
+	for(d = gp->defer; d != nil; d = d->link) {
+		dumpint(TagDefer);
+		dumpint((uintptr)d);
+		dumpint((uintptr)gp);
+		dumpint((uintptr)d->argp);
+		dumpint((uintptr)d->pc);
+		dumpint((uintptr)d->fn);
+		dumpint((uintptr)d->fn->fn);
+		dumpint((uintptr)d->link);
+	}
+	for (p = gp->panic; p != nil; p = p->link) {
+		dumpint(TagPanic);
+		dumpint((uintptr)p);
+		dumpint((uintptr)gp);
+		dumpint((uintptr)p->arg.type);
+		dumpint((uintptr)p->arg.data);
+		dumpint(0); // was p->defer, no longer recorded
+		dumpint((uintptr)p->link);
+	}
+}
+
+static void
+dumpgs(void)
+{
+	G *gp;
+	uint32 i;
+	uint32 status;
+
+	// goroutines & stacks
+	for(i = 0; i < runtime·allglen; i++) {
+		gp = runtime·allg[i];
+		status = runtime·readgstatus(gp); // The world is stopped so gp will not be in a scan state.
+		switch(status){
+		default:
+			runtime·printf("runtime: unexpected G.status %d\n", status);
+			runtime·throw("dumpgs in STW - bad status");
+		case Gdead:
+			break;
+		case Grunnable:
+		case Gsyscall:
+		case Gwaiting:
+			dumpgoroutine(gp);
+			break;
+		}
+	}
+}
+
+static void
+finq_callback(FuncVal *fn, byte *obj, uintptr nret, Type *fint, PtrType *ot)
+{
+	dumpint(TagQueuedFinalizer);
+	dumpint((uintptr)obj);
+	dumpint((uintptr)fn);
+	dumpint((uintptr)fn->fn);
+	dumpint((uintptr)fint);
+	dumpint((uintptr)ot);
+	USED(&nret);
+}
+
+
+static void
+dumproots(void)
+{
+	MSpan *s, **allspans;
+	uint32 spanidx;
+	Special *sp;
+	SpecialFinalizer *spf;
+	byte *p;
+
+	// data segment
+	dumpbvtypes(&runtime·gcdatamask, runtime·data);
+	dumpint(TagData);
+	dumpint((uintptr)runtime·data);
+	dumpmemrange(runtime·data, runtime·edata - runtime·data);
+	dumpfields(runtime·gcdatamask);
+
+	// bss segment
+	dumpbvtypes(&runtime·gcbssmask, runtime·bss);
+	dumpint(TagBss);
+	dumpint((uintptr)runtime·bss);
+	dumpmemrange(runtime·bss, runtime·ebss - runtime·bss);
+	dumpfields(runtime·gcbssmask);
+
+	// MSpan.types
+	allspans = runtime·mheap.allspans;
+	for(spanidx=0; spanidx<runtime·mheap.nspan; spanidx++) {
+		s = allspans[spanidx];
+		if(s->state == MSpanInUse) {
+			// Finalizers
+			for(sp = s->specials; sp != nil; sp = sp->next) {
+				if(sp->kind != KindSpecialFinalizer)
+					continue;
+				spf = (SpecialFinalizer*)sp;
+				p = (byte*)((s->start << PageShift) + spf->special.offset);
+				dumpfinalizer(p, spf->fn, spf->fint, spf->ot);
+			}
+		}
+	}
+
+	// Finalizer queue
+	runtime·iterate_finq(finq_callback);
+}
+
+// Bit vector of free marks.	
+// Needs to be as big as the largest number of objects per span.	
+#pragma dataflag NOPTR
+static byte free[PageSize/8];	
+
+static void
+dumpobjs(void)
+{
+	uintptr i, j, size, n;
+	MSpan *s;
+	MLink *l;
+	byte *p;
+
+	for(i = 0; i < runtime·mheap.nspan; i++) {
+		s = runtime·mheap.allspans[i];
+		if(s->state != MSpanInUse)
+			continue;
+		p = (byte*)(s->start << PageShift);
+		size = s->elemsize;
+		n = (s->npages << PageShift) / size;
+		if(n > nelem(free))	
+			runtime·throw("free array doesn't have enough entries");	
+		for(l = s->freelist; l != nil; l = l->next)
+			free[((byte*)l - p) / size] = true;	
+		for(j = 0; j < n; j++, p += size) {
+			if(free[j]) {	
+				free[j] = false;	
+				continue;	
+			}
+			dumpobj(p, size, makeheapobjbv(p, size));
+		}
+	}
+}
+
+static void
+dumpparams(void)
+{
+	byte *x;
+
+	dumpint(TagParams);
+	x = (byte*)1;
+	if(*(byte*)&x == 1)
+		dumpbool(false); // little-endian ptrs
+	else
+		dumpbool(true); // big-endian ptrs
+	dumpint(PtrSize);
+	dumpint((uintptr)runtime·mheap.arena_start);
+	dumpint((uintptr)runtime·mheap.arena_used);
+	dumpint(thechar);
+	dumpcstr(GOEXPERIMENT);
+	dumpint(runtime·ncpu);
+}
+
+static void
+itab_callback(Itab *tab)
+{
+	Type *t;
+
+	t = tab->type;
+	// Dump a map from itab* to the type of its data field.
+	// We want this map so we can deduce types of interface referents.
+	if((t->kind & KindDirectIface) == 0) {
+		// indirect - data slot is a pointer to t.
+		dumptype(t->ptrto);
+		dumpint(TagItab);
+		dumpint((uintptr)tab);
+		dumpint((uintptr)t->ptrto);
+	} else if((t->kind & KindNoPointers) == 0) {
+		// t is pointer-like - data slot is a t.
+		dumptype(t);
+		dumpint(TagItab);
+		dumpint((uintptr)tab);
+		dumpint((uintptr)t);
+	} else {
+		// Data slot is a scalar.  Dump type just for fun.
+		// With pointer-only interfaces, this shouldn't happen.
+		dumptype(t);
+		dumpint(TagItab);
+		dumpint((uintptr)tab);
+		dumpint((uintptr)t);
+	}
+}
+
+static void
+dumpitabs(void)
+{
+	void (*fn)(Itab*);
+	
+	fn = itab_callback;
+	runtime·iterate_itabs(&fn);
+}
+
+static void
+dumpms(void)
+{
+	M *mp;
+
+	for(mp = runtime·allm; mp != nil; mp = mp->alllink) {
+		dumpint(TagOSThread);
+		dumpint((uintptr)mp);
+		dumpint(mp->id);
+		dumpint(mp->procid);
+	}
+}
+
+static void
+dumpmemstats(void)
+{
+	int32 i;
+
+	dumpint(TagMemStats);
+	dumpint(mstats.alloc);
+	dumpint(mstats.total_alloc);
+	dumpint(mstats.sys);
+	dumpint(mstats.nlookup);
+	dumpint(mstats.nmalloc);
+	dumpint(mstats.nfree);
+	dumpint(mstats.heap_alloc);
+	dumpint(mstats.heap_sys);
+	dumpint(mstats.heap_idle);
+	dumpint(mstats.heap_inuse);
+	dumpint(mstats.heap_released);
+	dumpint(mstats.heap_objects);
+	dumpint(mstats.stacks_inuse);
+	dumpint(mstats.stacks_sys);
+	dumpint(mstats.mspan_inuse);
+	dumpint(mstats.mspan_sys);
+	dumpint(mstats.mcache_inuse);
+	dumpint(mstats.mcache_sys);
+	dumpint(mstats.buckhash_sys);
+	dumpint(mstats.gc_sys);
+	dumpint(mstats.other_sys);
+	dumpint(mstats.next_gc);
+	dumpint(mstats.last_gc);
+	dumpint(mstats.pause_total_ns);
+	for(i = 0; i < 256; i++)
+		dumpint(mstats.pause_ns[i]);
+	dumpint(mstats.numgc);
+}
+
+static void
+dumpmemprof_callback(Bucket *b, uintptr nstk, uintptr *stk, uintptr size, uintptr allocs, uintptr frees)
+{
+	uintptr i, pc;
+	Func *f;
+	byte buf[20];
+	String file;
+	int32 line;
+
+	dumpint(TagMemProf);
+	dumpint((uintptr)b);
+	dumpint(size);
+	dumpint(nstk);
+	for(i = 0; i < nstk; i++) {
+		pc = stk[i];
+		f = runtime·findfunc(pc);
+		if(f == nil) {
+			runtime·snprintf(buf, sizeof(buf), "%X", (uint64)pc);
+			dumpcstr((int8*)buf);
+			dumpcstr("?");
+			dumpint(0);
+		} else {
+			dumpcstr(runtime·funcname(f));
+			// TODO: Why do we need to back up to a call instruction here?
+			// Maybe profiler should do this.
+			if(i > 0 && pc > f->entry) {
+				if(thechar == '6' || thechar == '8')
+					pc--;
+				else
+					pc -= 4; // arm, etc
+			}
+			line = runtime·funcline(f, pc, &file);
+			dumpstr(file);
+			dumpint(line);
+		}
+	}
+	dumpint(allocs);
+	dumpint(frees);
+}
+
+static void
+dumpmemprof(void)
+{
+	MSpan *s, **allspans;
+	uint32 spanidx;
+	Special *sp;
+	SpecialProfile *spp;
+	byte *p;
+	void (*fn)(Bucket*, uintptr, uintptr*, uintptr, uintptr, uintptr);
+	
+	fn = dumpmemprof_callback;
+	runtime·iterate_memprof(&fn);
+
+	allspans = runtime·mheap.allspans;
+	for(spanidx=0; spanidx<runtime·mheap.nspan; spanidx++) {
+		s = allspans[spanidx];
+		if(s->state != MSpanInUse)
+			continue;
+		for(sp = s->specials; sp != nil; sp = sp->next) {
+			if(sp->kind != KindSpecialProfile)
+				continue;
+			spp = (SpecialProfile*)sp;
+			p = (byte*)((s->start << PageShift) + spp->special.offset);
+			dumpint(TagAllocSample);
+			dumpint((uintptr)p);
+			dumpint((uintptr)spp->b);
+		}
+	}
+}
+
+static void
+mdump(void)
+{
+	byte *hdr;
+	uintptr i;
+	MSpan *s;
+
+	// make sure we're done sweeping
+	for(i = 0; i < runtime·mheap.nspan; i++) {
+		s = runtime·mheap.allspans[i];
+		if(s->state == MSpanInUse)
+			runtime·MSpan_EnsureSwept(s);
+	}
+
+	runtime·memclr((byte*)&typecache[0], sizeof(typecache));
+	hdr = (byte*)"go1.4 heap dump\n";
+	write(hdr, runtime·findnull(hdr));
+	dumpparams();
+	dumpitabs();
+	dumpobjs();
+	dumpgs();
+	dumpms();
+	dumproots();
+	dumpmemstats();
+	dumpmemprof();
+	dumpint(TagEOF);
+	flush();
+}
+
+void
+runtime·writeheapdump_m(void)
+{
+	uintptr fd;
+	
+	fd = g->m->scalararg[0];
+	g->m->scalararg[0] = 0;
+
+	runtime·casgstatus(g->m->curg, Grunning, Gwaiting);
+	g->waitreason = runtime·gostringnocopy((byte*)"dumping heap");
+
+	// Update stats so we can dump them.
+	// As a side effect, flushes all the MCaches so the MSpan.freelist
+	// lists contain all the free objects.
+	runtime·updatememstats(nil);
+
+	// Set dump file.
+	dumpfd = fd;
+
+	// Call dump routine.
+	mdump();
+
+	// Reset dump file.
+	dumpfd = 0;
+	if(tmpbuf != nil) {
+		runtime·SysFree(tmpbuf, tmpbufsize, &mstats.other_sys);
+		tmpbuf = nil;
+		tmpbufsize = 0;
+	}
+
+	runtime·casgstatus(g->m->curg, Gwaiting, Grunning);
+}
+
+// dumpint() the kind & offset of each field in an object.
+static void
+dumpfields(BitVector bv)
+{
+	dumpbv(&bv, 0);
+	dumpint(FieldKindEol);
+}
+
+// The heap dump reader needs to be able to disambiguate
+// Eface entries.  So it needs to know every type that might
+// appear in such an entry.  The following routine accomplishes that.
+
+// Dump all the types that appear in the type field of
+// any Eface described by this bit vector.
+static void
+dumpbvtypes(BitVector *bv, byte *base)
+{
+	uintptr i;
+
+	for(i = 0; i < bv->n; i += BitsPerPointer) {
+		if((bv->bytedata[i/8] >> i%8 & 3) != BitsMultiWord)
+			continue;
+		switch(bv->bytedata[(i+BitsPerPointer)/8] >> (i+BitsPerPointer)%8 & 3) {
+		default:
+			runtime·throw("unexpected garbage collection bits");
+		case BitsIface:
+			i += BitsPerPointer;
+			break;
+		case BitsEface:
+			dumptype(*(Type**)(base + i / BitsPerPointer * PtrSize));
+			i += BitsPerPointer;
+			break;
+		}
+	}
+}
+
+static BitVector
+makeheapobjbv(byte *p, uintptr size)
+{
+	uintptr off, nptr, i;
+	byte shift, *bitp, bits;
+	bool mw;
+
+	// Extend the temp buffer if necessary.
+	nptr = size/PtrSize;
+	if(tmpbufsize < nptr*BitsPerPointer/8+1) {
+		if(tmpbuf != nil)
+			runtime·SysFree(tmpbuf, tmpbufsize, &mstats.other_sys);
+		tmpbufsize = nptr*BitsPerPointer/8+1;
+		tmpbuf = runtime·sysAlloc(tmpbufsize, &mstats.other_sys);
+		if(tmpbuf == nil)
+			runtime·throw("heapdump: out of memory");
+	}
+
+	// Copy and compact the bitmap.
+	mw = false;
+	for(i = 0; i < nptr; i++) {
+		off = (uintptr*)(p + i*PtrSize) - (uintptr*)runtime·mheap.arena_start;
+		bitp = runtime·mheap.arena_start - off/wordsPerBitmapByte - 1;
+		shift = (off % wordsPerBitmapByte) * gcBits;
+		bits = (*bitp >> (shift + 2)) & BitsMask;
+		if(!mw && bits == BitsDead)
+			break;  // end of heap object
+		mw = !mw && bits == BitsMultiWord;
+		tmpbuf[i*BitsPerPointer/8] &= ~(BitsMask<<((i*BitsPerPointer)%8));
+		tmpbuf[i*BitsPerPointer/8] |= bits<<((i*BitsPerPointer)%8);
+	}
+	return (BitVector){i*BitsPerPointer, tmpbuf};
+}