From 67426a8a9eabd6d859e42ca799eab6c1aa0d616a Mon Sep 17 00:00:00 2001
From: Michael Hudson-Doyle <michael.hudson@canonical.com>
Date: Thu, 12 Mar 2015 12:22:18 +1300
Subject: [PATCH] runtime, cmd/internal/ld: change runtime to use a single
 linker symbol

In preparation for being able to run a go program that has code
in several objects, this changes from having several linker
symbols used by the runtime into having one linker symbol that
points at a structure containing the needed data.  Multiple
object support will construct a linked list of such structures.

A follow up will initialize the slices in the themoduledata
structure directly from the linker but I was aiming for a minimal
diff for now.

Change-Id: I613cce35309801cf265a1d5ae5aaca8d689c5cbf
Reviewed-on: https://go-review.googlesource.com/7441
Reviewed-by: Ian Lance Taylor <iant@golang.org>
---
 src/cmd/internal/ld/symtab.go    | 34 +++++++++++++
 src/runtime/heapdump.go          | 12 ++---
 src/runtime/malloc.go            |  2 +-
 src/runtime/mbarrier.go          | 32 ++++++------
 src/runtime/mbitmap.go           |  8 +--
 src/runtime/mem_plan9.go         |  2 +-
 src/runtime/mfinal.go            |  8 +--
 src/runtime/mgc.go               |  7 +--
 src/runtime/mgcmark.go           |  4 +-
 src/runtime/os1_windows_386.go   |  4 +-
 src/runtime/os1_windows_amd64.go |  4 +-
 src/runtime/proc1.go             |  4 +-
 src/runtime/race1.go             | 32 ++++++------
 src/runtime/runtime1.go          |  6 +--
 src/runtime/symtab.go            | 84 ++++++++++++++++++--------------
 15 files changed, 139 insertions(+), 104 deletions(-)

diff --git a/src/cmd/internal/ld/symtab.go b/src/cmd/internal/ld/symtab.go
index e165c8c855..6001ace016 100644
--- a/src/cmd/internal/ld/symtab.go
+++ b/src/cmd/internal/ld/symtab.go
@@ -395,4 +395,38 @@ func symtab() {
 			liveness += (s.Size + int64(s.Align) - 1) &^ (int64(s.Align) - 1)
 		}
 	}
+
+	// Information about the layout of the executable image for the
+	// runtime to use. Any changes here must be matched by changes to
+	// the definition of moduledata in runtime/symtab.go.
+	moduledata := Linklookup(Ctxt, "runtime.themoduledata", 0)
+	moduledata.Type = SNOPTRDATA
+	moduledata.Size = 0 // truncate symbol back to 0 bytes to reinitialize
+	moduledata.Reachable = true
+	// Three slices (pclntable, ftab, filetab), uninitalized
+	moduledata.Size += int64((3 * 3 * Thearch.Ptrsize))
+	Symgrow(Ctxt, moduledata, moduledata.Size)
+	// Three uintptrs, initialized
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.pclntab", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.epclntab", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.findfunctab", 0))
+	// 2 more uintptrs (minpc, maxpc), uninitalized
+	moduledata.Size += int64(2 * Thearch.Ptrsize)
+	Symgrow(Ctxt, moduledata, moduledata.Size)
+	// more initialized uintptrs
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.text", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.etext", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.noptrdata", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.enoptrdata", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.data", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.edata", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.bss", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.ebss", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.noptrbss", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.enoptrbss", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.end", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.gcdata", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.gcbss", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.typelink", 0))
+	Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.etypelink", 0))
 }
diff --git a/src/runtime/heapdump.go b/src/runtime/heapdump.go
index f5770958fd..090a490449 100644
--- a/src/runtime/heapdump.go
+++ b/src/runtime/heapdump.go
@@ -432,17 +432,17 @@ func finq_callback(fn *funcval, obj unsafe.Pointer, nret uintptr, fint *_type, o
 
 func dumproots() {
 	// data segment
-	dumpbvtypes(&gcdatamask, unsafe.Pointer(&data))
+	dumpbvtypes(&gcdatamask, unsafe.Pointer(themoduledata.data))
 	dumpint(tagData)
-	dumpint(uint64(uintptr(unsafe.Pointer(&data))))
-	dumpmemrange(unsafe.Pointer(&data), uintptr(unsafe.Pointer(&edata))-uintptr(unsafe.Pointer(&data)))
+	dumpint(uint64(themoduledata.data))
+	dumpmemrange(unsafe.Pointer(themoduledata.data), themoduledata.edata-themoduledata.data)
 	dumpfields(gcdatamask)
 
 	// bss segment
-	dumpbvtypes(&gcbssmask, unsafe.Pointer(&bss))
+	dumpbvtypes(&gcbssmask, unsafe.Pointer(themoduledata.bss))
 	dumpint(tagBSS)
-	dumpint(uint64(uintptr(unsafe.Pointer(&bss))))
-	dumpmemrange(unsafe.Pointer(&bss), uintptr(unsafe.Pointer(&ebss))-uintptr(unsafe.Pointer(&bss)))
+	dumpint(uint64(themoduledata.bss))
+	dumpmemrange(unsafe.Pointer(themoduledata.bss), themoduledata.ebss-themoduledata.bss)
 	dumpfields(gcbssmask)
 
 	// MSpan.types
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 11d6f94e54..fde58e2d0c 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -322,7 +322,7 @@ func mallocinit() {
 			// So adjust it upward a little bit ourselves: 1/4 MB to get
 			// away from the running binary image and then round up
 			// to a MB boundary.
-			p = round(uintptr(unsafe.Pointer(&end))+(1<<18), 1<<20)
+			p = round(themoduledata.end+(1<<18), 1<<20)
 			pSize = bitmapSize + spansSize + arenaSize + _PageSize
 			p = uintptr(sysReserve(unsafe.Pointer(p), pSize, &reserved))
 			if p != 0 {
diff --git a/src/runtime/mbarrier.go b/src/runtime/mbarrier.go
index a64bd12815..e6183e74a8 100644
--- a/src/runtime/mbarrier.go
+++ b/src/runtime/mbarrier.go
@@ -428,29 +428,29 @@ func wbshadowinit() {
 	mheap_.shadow_reserved = reserved
 	start := ^uintptr(0)
 	end := uintptr(0)
-	if start > uintptr(unsafe.Pointer(&noptrdata)) {
-		start = uintptr(unsafe.Pointer(&noptrdata))
+	if start > themoduledata.noptrdata {
+		start = themoduledata.noptrdata
 	}
-	if start > uintptr(unsafe.Pointer(&data)) {
-		start = uintptr(unsafe.Pointer(&data))
+	if start > themoduledata.data {
+		start = themoduledata.data
 	}
-	if start > uintptr(unsafe.Pointer(&noptrbss)) {
-		start = uintptr(unsafe.Pointer(&noptrbss))
+	if start > themoduledata.noptrbss {
+		start = themoduledata.noptrbss
 	}
-	if start > uintptr(unsafe.Pointer(&bss)) {
-		start = uintptr(unsafe.Pointer(&bss))
+	if start > themoduledata.bss {
+		start = themoduledata.bss
 	}
-	if end < uintptr(unsafe.Pointer(&enoptrdata)) {
-		end = uintptr(unsafe.Pointer(&enoptrdata))
+	if end < themoduledata.enoptrdata {
+		end = themoduledata.enoptrdata
 	}
-	if end < uintptr(unsafe.Pointer(&edata)) {
-		end = uintptr(unsafe.Pointer(&edata))
+	if end < themoduledata.edata {
+		end = themoduledata.edata
 	}
-	if end < uintptr(unsafe.Pointer(&enoptrbss)) {
-		end = uintptr(unsafe.Pointer(&enoptrbss))
+	if end < themoduledata.enoptrbss {
+		end = themoduledata.enoptrbss
 	}
-	if end < uintptr(unsafe.Pointer(&ebss)) {
-		end = uintptr(unsafe.Pointer(&ebss))
+	if end < themoduledata.ebss {
+		end = themoduledata.ebss
 	}
 	start &^= _PhysPageSize - 1
 	end = round(end, _PhysPageSize)
diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go
index 7dd3637665..ebee7429b1 100644
--- a/src/runtime/mbitmap.go
+++ b/src/runtime/mbitmap.go
@@ -747,12 +747,12 @@ func getgcmask(p unsafe.Pointer, t *_type, mask **byte, len *uintptr) {
 	const typeBitsPerByte = 8 / typeBitsWidth
 
 	// data
-	if uintptr(unsafe.Pointer(&data)) <= uintptr(p) && uintptr(p) < uintptr(unsafe.Pointer(&edata)) {
+	if themoduledata.data <= uintptr(p) && uintptr(p) < themoduledata.edata {
 		n := (*ptrtype)(unsafe.Pointer(t)).elem.size
 		*len = n / ptrSize
 		*mask = &make([]byte, *len)[0]
 		for i := uintptr(0); i < n; i += ptrSize {
-			off := (uintptr(p) + i - uintptr(unsafe.Pointer(&data))) / ptrSize
+			off := (uintptr(p) + i - themoduledata.data) / ptrSize
 			bits := (*(*byte)(add(unsafe.Pointer(gcdatamask.bytedata), off/typeBitsPerByte)) >> ((off % typeBitsPerByte) * typeBitsWidth)) & typeMask
 			*(*byte)(add(unsafe.Pointer(*mask), i/ptrSize)) = bits
 		}
@@ -760,12 +760,12 @@ func getgcmask(p unsafe.Pointer, t *_type, mask **byte, len *uintptr) {
 	}
 
 	// bss
-	if uintptr(unsafe.Pointer(&bss)) <= uintptr(p) && uintptr(p) < uintptr(unsafe.Pointer(&ebss)) {
+	if themoduledata.bss <= uintptr(p) && uintptr(p) < themoduledata.ebss {
 		n := (*ptrtype)(unsafe.Pointer(t)).elem.size
 		*len = n / ptrSize
 		*mask = &make([]byte, *len)[0]
 		for i := uintptr(0); i < n; i += ptrSize {
-			off := (uintptr(p) + i - uintptr(unsafe.Pointer(&bss))) / ptrSize
+			off := (uintptr(p) + i - themoduledata.bss) / ptrSize
 			bits := (*(*byte)(add(unsafe.Pointer(gcbssmask.bytedata), off/typeBitsPerByte)) >> ((off % typeBitsPerByte) * typeBitsWidth)) & typeMask
 			*(*byte)(add(unsafe.Pointer(*mask), i/ptrSize)) = bits
 		}
diff --git a/src/runtime/mem_plan9.go b/src/runtime/mem_plan9.go
index bf7d23881f..62c6a6f7de 100644
--- a/src/runtime/mem_plan9.go
+++ b/src/runtime/mem_plan9.go
@@ -116,7 +116,7 @@ func memRound(p uintptr) uintptr {
 }
 
 func initBloc() {
-	bloc = memRound(uintptr(unsafe.Pointer(&end)))
+	bloc = memRound(themoduledata.end)
 }
 
 func sbrk(n uintptr) unsafe.Pointer {
diff --git a/src/runtime/mfinal.go b/src/runtime/mfinal.go
index 55ba06d4b0..2de75656e5 100644
--- a/src/runtime/mfinal.go
+++ b/src/runtime/mfinal.go
@@ -289,10 +289,10 @@ func SetFinalizer(obj interface{}, finalizer interface{}) {
 		// The relevant segments are: noptrdata, data, bss, noptrbss.
 		// We cannot assume they are in any order or even contiguous,
 		// due to external linking.
-		if uintptr(unsafe.Pointer(&noptrdata)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&enoptrdata)) ||
-			uintptr(unsafe.Pointer(&data)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&edata)) ||
-			uintptr(unsafe.Pointer(&bss)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&ebss)) ||
-			uintptr(unsafe.Pointer(&noptrbss)) <= uintptr(e.data) && uintptr(e.data) < uintptr(unsafe.Pointer(&enoptrbss)) {
+		if themoduledata.noptrdata <= uintptr(e.data) && uintptr(e.data) < themoduledata.enoptrdata ||
+			themoduledata.data <= uintptr(e.data) && uintptr(e.data) < themoduledata.edata ||
+			themoduledata.bss <= uintptr(e.data) && uintptr(e.data) < themoduledata.ebss ||
+			themoduledata.noptrbss <= uintptr(e.data) && uintptr(e.data) < themoduledata.enoptrbss {
 			return
 		}
 		throw("runtime.SetFinalizer: pointer not in allocated block")
diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 8eba5a8bc2..89f3fb5340 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -130,9 +130,6 @@ const (
 	_RootCount       = 5
 )
 
-// linker-provided
-var data, edata, bss, ebss, gcdata, gcbss, noptrdata, enoptrdata, noptrbss, enoptrbss, end struct{}
-
 //go:linkname weak_cgo_allocate go.weak.runtime._cgo_allocate_internal
 var weak_cgo_allocate byte
 
@@ -160,8 +157,8 @@ func gcinit() {
 
 	work.markfor = parforalloc(_MaxGcproc)
 	gcpercent = readgogc()
-	gcdatamask = unrollglobgcprog((*byte)(unsafe.Pointer(&gcdata)), uintptr(unsafe.Pointer(&edata))-uintptr(unsafe.Pointer(&data)))
-	gcbssmask = unrollglobgcprog((*byte)(unsafe.Pointer(&gcbss)), uintptr(unsafe.Pointer(&ebss))-uintptr(unsafe.Pointer(&bss)))
+	gcdatamask = unrollglobgcprog((*byte)(unsafe.Pointer(themoduledata.gcdata)), themoduledata.edata-themoduledata.data)
+	gcbssmask = unrollglobgcprog((*byte)(unsafe.Pointer(themoduledata.gcbss)), themoduledata.ebss-themoduledata.bss)
 	memstats.next_gc = heapminimum
 }
 
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index bdb5888a28..3a9679e43a 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -60,10 +60,10 @@ func markroot(desc *parfor, i uint32) {
 	// Note: if you add a case here, please also update heapdump.go:dumproots.
 	switch i {
 	case _RootData:
-		scanblock(uintptr(unsafe.Pointer(&data)), uintptr(unsafe.Pointer(&edata))-uintptr(unsafe.Pointer(&data)), gcdatamask.bytedata, &gcw)
+		scanblock(themoduledata.data, themoduledata.edata-themoduledata.data, gcdatamask.bytedata, &gcw)
 
 	case _RootBss:
-		scanblock(uintptr(unsafe.Pointer(&bss)), uintptr(unsafe.Pointer(&ebss))-uintptr(unsafe.Pointer(&bss)), gcbssmask.bytedata, &gcw)
+		scanblock(themoduledata.bss, themoduledata.ebss-themoduledata.bss, gcbssmask.bytedata, &gcw)
 
 	case _RootFinalizers:
 		for fb := allfin; fb != nil; fb = fb.alllink {
diff --git a/src/runtime/os1_windows_386.go b/src/runtime/os1_windows_386.go
index f105539659..e5fe7486cb 100644
--- a/src/runtime/os1_windows_386.go
+++ b/src/runtime/os1_windows_386.go
@@ -8,8 +8,6 @@ import (
 	"unsafe"
 )
 
-var text struct{}
-
 func dumpregs(r *context) {
 	print("eax     ", hex(r.eax), "\n")
 	print("ebx     ", hex(r.ebx), "\n")
@@ -29,7 +27,7 @@ func dumpregs(r *context) {
 func isgoexception(info *exceptionrecord, r *context) bool {
 	// Only handle exception if executing instructions in Go binary
 	// (not Windows library code).
-	if r.eip < uint32(uintptr(unsafe.Pointer(&text))) || uint32(uintptr(unsafe.Pointer(&etext))) < r.eip {
+	if r.eip < uint32(themoduledata.text) || uint32(themoduledata.etext) < r.eip {
 		return false
 	}
 
diff --git a/src/runtime/os1_windows_amd64.go b/src/runtime/os1_windows_amd64.go
index 1b6b99988d..37a97b7382 100644
--- a/src/runtime/os1_windows_amd64.go
+++ b/src/runtime/os1_windows_amd64.go
@@ -8,8 +8,6 @@ import (
 	"unsafe"
 )
 
-var text struct{}
-
 func dumpregs(r *context) {
 	print("rax     ", hex(r.rax), "\n")
 	print("rbx     ", hex(r.rbx), "\n")
@@ -36,7 +34,7 @@ func dumpregs(r *context) {
 func isgoexception(info *exceptionrecord, r *context) bool {
 	// Only handle exception if executing instructions in Go binary
 	// (not Windows library code).
-	if r.rip < uint64(uintptr(unsafe.Pointer(&text))) || uint64(uintptr(unsafe.Pointer(&etext))) < r.rip {
+	if r.rip < uint64(themoduledata.text) || uint64(themoduledata.etext) < r.rip {
 		return false
 	}
 
diff --git a/src/runtime/proc1.go b/src/runtime/proc1.go
index 30d6c7b9c6..7fa519dd70 100644
--- a/src/runtime/proc1.go
+++ b/src/runtime/proc1.go
@@ -2293,8 +2293,6 @@ func _System()       { _System() }
 func _ExternalCode() { _ExternalCode() }
 func _GC()           { _GC() }
 
-var etext struct{}
-
 // Called if we receive a SIGPROF signal.
 func sigprof(pc, sp, lr uintptr, gp *g, mp *m) {
 	if prof.hz == 0 {
@@ -2408,7 +2406,7 @@ func sigprof(pc, sp, lr uintptr, gp *g, mp *m) {
 			// If all of the above has failed, account it against abstract "System" or "GC".
 			n = 2
 			// "ExternalCode" is better than "etext".
-			if pc > uintptr(unsafe.Pointer(&etext)) {
+			if pc > themoduledata.etext {
 				pc = funcPC(_ExternalCode) + _PCQuantum
 			}
 			stk[0] = pc
diff --git a/src/runtime/race1.go b/src/runtime/race1.go
index 4c14d84746..18ecc88a5f 100644
--- a/src/runtime/race1.go
+++ b/src/runtime/race1.go
@@ -119,29 +119,29 @@ func raceinit() uintptr {
 	// Round data segment to page boundaries, because it's used in mmap().
 	start := ^uintptr(0)
 	end := uintptr(0)
-	if start > uintptr(unsafe.Pointer(&noptrdata)) {
-		start = uintptr(unsafe.Pointer(&noptrdata))
+	if start > themoduledata.noptrdata {
+		start = themoduledata.noptrdata
 	}
-	if start > uintptr(unsafe.Pointer(&data)) {
-		start = uintptr(unsafe.Pointer(&data))
+	if start > themoduledata.data {
+		start = themoduledata.data
 	}
-	if start > uintptr(unsafe.Pointer(&noptrbss)) {
-		start = uintptr(unsafe.Pointer(&noptrbss))
+	if start > themoduledata.noptrbss {
+		start = themoduledata.noptrbss
 	}
-	if start > uintptr(unsafe.Pointer(&bss)) {
-		start = uintptr(unsafe.Pointer(&bss))
+	if start > themoduledata.bss {
+		start = themoduledata.bss
 	}
-	if end < uintptr(unsafe.Pointer(&enoptrdata)) {
-		end = uintptr(unsafe.Pointer(&enoptrdata))
+	if end < themoduledata.enoptrdata {
+		end = themoduledata.enoptrdata
 	}
-	if end < uintptr(unsafe.Pointer(&edata)) {
-		end = uintptr(unsafe.Pointer(&edata))
+	if end < themoduledata.edata {
+		end = themoduledata.edata
 	}
-	if end < uintptr(unsafe.Pointer(&enoptrbss)) {
-		end = uintptr(unsafe.Pointer(&enoptrbss))
+	if end < themoduledata.enoptrbss {
+		end = themoduledata.enoptrbss
 	}
-	if end < uintptr(unsafe.Pointer(&ebss)) {
-		end = uintptr(unsafe.Pointer(&ebss))
+	if end < themoduledata.ebss {
+		end = themoduledata.ebss
 	}
 	size := round(end-start, _PageSize)
 	racecall(&__tsan_map_shadow, start, size, 0, 0)
diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go
index ac9042c792..072a58552e 100644
--- a/src/runtime/runtime1.go
+++ b/src/runtime/runtime1.go
@@ -424,15 +424,13 @@ func gomcache() *mcache {
 	return getg().m.mcache
 }
 
-var typelink, etypelink [0]byte
-
 //go:linkname reflect_typelinks reflect.typelinks
 //go:nosplit
 func reflect_typelinks() []*_type {
 	var ret []*_type
 	sp := (*slice)(unsafe.Pointer(&ret))
-	sp.array = (*byte)(unsafe.Pointer(&typelink))
-	sp.len = uint((uintptr(unsafe.Pointer(&etypelink)) - uintptr(unsafe.Pointer(&typelink))) / unsafe.Sizeof(ret[0]))
+	sp.array = (*byte)(unsafe.Pointer(themoduledata.typelink))
+	sp.len = uint((themoduledata.etypelink - themoduledata.typelink) / unsafe.Sizeof(ret[0]))
 	sp.cap = sp.len
 	return ret
 }
diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
index 4f3111d551..689a3361a8 100644
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -29,15 +29,27 @@ const (
 	_ArgsSizeUnknown            = -0x80000000
 )
 
-var (
-	pclntable []byte
-	ftab      []functab
-	filetab   []uint32
-
-	pclntab, epclntab, findfunctab struct{} // linker symbols
+// moduledata records information about the layout of the executable
+// image. It is written by the linker. Any changes here must be
+// matched changes to the code in cmd/internal/ld/symtab.go:symtab.
+type moduledata struct {
+	pclntable                      []byte
+	ftab                           []functab
+	filetab                        []uint32
+	pclntab, epclntab, findfunctab uintptr
+	minpc, maxpc                   uintptr
+
+	text, etext           uintptr
+	noptrdata, enoptrdata uintptr
+	data, edata           uintptr
+	bss, ebss             uintptr
+	noptrbss, enoptrbss   uintptr
+	end, gcdata, gcbss    uintptr
+
+	typelink, etypelink uintptr
+}
 
-	minpc, maxpc uintptr
-)
+var themoduledata moduledata // linker symbol
 
 type functab struct {
 	entry   uintptr
@@ -64,38 +76,38 @@ func symtabinit() {
 	// See golang.org/s/go12symtab for header: 0xfffffffb,
 	// two zero bytes, a byte giving the PC quantum,
 	// and a byte giving the pointer width in bytes.
-	pcln := (*[8]byte)(unsafe.Pointer(&pclntab))
-	pcln32 := (*[2]uint32)(unsafe.Pointer(&pclntab))
+	pcln := (*[8]byte)(unsafe.Pointer(themoduledata.pclntab))
+	pcln32 := (*[2]uint32)(unsafe.Pointer(themoduledata.pclntab))
 	if pcln32[0] != 0xfffffffb || pcln[4] != 0 || pcln[5] != 0 || pcln[6] != _PCQuantum || pcln[7] != ptrSize {
 		println("runtime: function symbol table header:", hex(pcln32[0]), hex(pcln[4]), hex(pcln[5]), hex(pcln[6]), hex(pcln[7]))
 		throw("invalid function symbol table\n")
 	}
 
 	// pclntable is all bytes of pclntab symbol.
-	sp := (*sliceStruct)(unsafe.Pointer(&pclntable))
-	sp.array = unsafe.Pointer(&pclntab)
-	sp.len = int(uintptr(unsafe.Pointer(&epclntab)) - uintptr(unsafe.Pointer(&pclntab)))
+	sp := (*sliceStruct)(unsafe.Pointer(&themoduledata.pclntable))
+	sp.array = unsafe.Pointer(themoduledata.pclntab)
+	sp.len = int(uintptr(unsafe.Pointer(themoduledata.epclntab)) - uintptr(unsafe.Pointer(themoduledata.pclntab)))
 	sp.cap = sp.len
 
 	// ftab is lookup table for function by program counter.
 	nftab := int(*(*uintptr)(add(unsafe.Pointer(pcln), 8)))
 	p := add(unsafe.Pointer(pcln), 8+ptrSize)
-	sp = (*sliceStruct)(unsafe.Pointer(&ftab))
+	sp = (*sliceStruct)(unsafe.Pointer(&themoduledata.ftab))
 	sp.array = p
 	sp.len = nftab + 1
 	sp.cap = sp.len
 	for i := 0; i < nftab; i++ {
 		// NOTE: ftab[nftab].entry is legal; it is the address beyond the final function.
-		if ftab[i].entry > ftab[i+1].entry {
-			f1 := (*_func)(unsafe.Pointer(&pclntable[ftab[i].funcoff]))
-			f2 := (*_func)(unsafe.Pointer(&pclntable[ftab[i+1].funcoff]))
+		if themoduledata.ftab[i].entry > themoduledata.ftab[i+1].entry {
+			f1 := (*_func)(unsafe.Pointer(&themoduledata.pclntable[themoduledata.ftab[i].funcoff]))
+			f2 := (*_func)(unsafe.Pointer(&themoduledata.pclntable[themoduledata.ftab[i+1].funcoff]))
 			f2name := "end"
 			if i+1 < nftab {
 				f2name = funcname(f2)
 			}
-			println("function symbol table not sorted by program counter:", hex(ftab[i].entry), funcname(f1), ">", hex(ftab[i+1].entry), f2name)
+			println("function symbol table not sorted by program counter:", hex(themoduledata.ftab[i].entry), funcname(f1), ">", hex(themoduledata.ftab[i+1].entry), f2name)
 			for j := 0; j <= i; j++ {
-				print("\t", hex(ftab[j].entry), " ", funcname((*_func)(unsafe.Pointer(&pclntable[ftab[j].funcoff]))), "\n")
+				print("\t", hex(themoduledata.ftab[j].entry), " ", funcname((*_func)(unsafe.Pointer(&themoduledata.pclntable[themoduledata.ftab[j].funcoff]))), "\n")
 			}
 			throw("invalid runtime symbol table")
 		}
@@ -104,19 +116,19 @@ func symtabinit() {
 	// The ftab ends with a half functab consisting only of
 	// 'entry', followed by a uint32 giving the pcln-relative
 	// offset of the file table.
-	sp = (*sliceStruct)(unsafe.Pointer(&filetab))
-	end := unsafe.Pointer(&ftab[nftab].funcoff) // just beyond ftab
+	sp = (*sliceStruct)(unsafe.Pointer(&themoduledata.filetab))
+	end := unsafe.Pointer(&themoduledata.ftab[nftab].funcoff) // just beyond ftab
 	fileoffset := *(*uint32)(end)
-	sp.array = unsafe.Pointer(&pclntable[fileoffset])
+	sp.array = unsafe.Pointer(&themoduledata.pclntable[fileoffset])
 	// length is in first element of array.
 	// set len to 1 so we can get first element.
 	sp.len = 1
 	sp.cap = 1
-	sp.len = int(filetab[0])
+	sp.len = int(themoduledata.filetab[0])
 	sp.cap = sp.len
 
-	minpc = ftab[0].entry
-	maxpc = ftab[nftab].entry
+	themoduledata.minpc = themoduledata.ftab[0].entry
+	themoduledata.maxpc = themoduledata.ftab[nftab].entry
 }
 
 // FuncForPC returns a *Func describing the function that contains the
@@ -147,33 +159,33 @@ func (f *Func) FileLine(pc uintptr) (file string, line int) {
 }
 
 func findfunc(pc uintptr) *_func {
-	if pc < minpc || pc >= maxpc {
+	if pc < themoduledata.minpc || pc >= themoduledata.maxpc {
 		return nil
 	}
 	const nsub = uintptr(len(findfuncbucket{}.subbuckets))
 
-	x := pc - minpc
+	x := pc - themoduledata.minpc
 	b := x / pcbucketsize
 	i := x % pcbucketsize / (pcbucketsize / nsub)
 
-	ffb := (*findfuncbucket)(add(unsafe.Pointer(&findfunctab), b*unsafe.Sizeof(findfuncbucket{})))
+	ffb := (*findfuncbucket)(add(unsafe.Pointer(themoduledata.findfunctab), b*unsafe.Sizeof(findfuncbucket{})))
 	idx := ffb.idx + uint32(ffb.subbuckets[i])
-	if pc < ftab[idx].entry {
+	if pc < themoduledata.ftab[idx].entry {
 		throw("findfunc: bad findfunctab entry")
 	}
 
 	// linear search to find func with pc >= entry.
-	for ftab[idx+1].entry <= pc {
+	for themoduledata.ftab[idx+1].entry <= pc {
 		idx++
 	}
-	return (*_func)(unsafe.Pointer(&pclntable[ftab[idx].funcoff]))
+	return (*_func)(unsafe.Pointer(&themoduledata.pclntable[themoduledata.ftab[idx].funcoff]))
 }
 
 func pcvalue(f *_func, off int32, targetpc uintptr, strict bool) int32 {
 	if off == 0 {
 		return -1
 	}
-	p := pclntable[off:]
+	p := themoduledata.pclntable[off:]
 	pc := f.entry
 	val := int32(-1)
 	for {
@@ -195,7 +207,7 @@ func pcvalue(f *_func, off int32, targetpc uintptr, strict bool) int32 {
 
 	print("runtime: invalid pc-encoded table f=", funcname(f), " pc=", hex(pc), " targetpc=", hex(targetpc), " tab=", p, "\n")
 
-	p = pclntable[off:]
+	p = themoduledata.pclntable[off:]
 	pc = f.entry
 	val = -1
 	for {
@@ -215,7 +227,7 @@ func cfuncname(f *_func) *byte {
 	if f == nil || f.nameoff == 0 {
 		return nil
 	}
-	return (*byte)(unsafe.Pointer(&pclntable[f.nameoff]))
+	return (*byte)(unsafe.Pointer(&themoduledata.pclntable[f.nameoff]))
 }
 
 func funcname(f *_func) string {
@@ -225,11 +237,11 @@ func funcname(f *_func) string {
 func funcline1(f *_func, targetpc uintptr, strict bool) (file string, line int32) {
 	fileno := int(pcvalue(f, f.pcfile, targetpc, strict))
 	line = pcvalue(f, f.pcln, targetpc, strict)
-	if fileno == -1 || line == -1 || fileno >= len(filetab) {
+	if fileno == -1 || line == -1 || fileno >= len(themoduledata.filetab) {
 		// print("looking for ", hex(targetpc), " in ", funcname(f), " got file=", fileno, " line=", lineno, "\n")
 		return "?", 0
 	}
-	file = gostringnocopy(&pclntable[filetab[fileno]])
+	file = gostringnocopy(&themoduledata.pclntable[themoduledata.filetab[fileno]])
 	return
 }
 
-- 
2.48.1