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[dev.link] cmd/link: write data sections to heap in Asmb on Wasm

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Make Wasm more like other architectures, writing data sections to
heap in Asmb instead of Asmb2. Then we can remove the
copy-on-write logic in applying relocations.

Change-Id: I26d5315ea9fba032fe4bdb9b5c7fe483611c4373
Reviewed-on: https://go-review.googlesource.com/c/go/+/230465
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
This commit is contained in:
Cherry Zhang 2020-04-28 09:53:29 -04:00
parent 3e8975172f
commit dd34841de7
13 changed files with 39 additions and 35 deletions
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43
src/cmd/link/internal/wasm/asm.go
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@ -92,7 +92,30 @@ func assignAddress(ldr *loader.Loader, sect *sym.Section, n int, s loader.Sym, v
return sect, n, va
}
func asmb(ctxt *ld.Link) {} // dummy
type wasmDataSect struct {
sect *sym.Section
data []byte
}
var dataSects []wasmDataSect
func asmb(ctxt *ld.Link, ldr *loader.Loader) {
sections := []*sym.Section{
ldr.SymSect(ldr.Lookup("runtime.rodata", 0)),
ldr.SymSect(ldr.Lookup("runtime.typelink", 0)),
ldr.SymSect(ldr.Lookup("runtime.itablink", 0)),
ldr.SymSect(ldr.Lookup("runtime.symtab", 0)),
ldr.SymSect(ldr.Lookup("runtime.pclntab", 0)),
ldr.SymSect(ldr.Lookup("runtime.noptrdata", 0)),
ldr.SymSect(ldr.Lookup("runtime.data", 0)),
}
dataSects = make([]wasmDataSect, len(sections))
for i, sect := range sections {
data := ld.DatblkBytes(ctxt, int64(sect.Vaddr), int64(sect.Length))
dataSects[i] = wasmDataSect{sect, data}
}
}
// asmb writes the final WebAssembly module binary.
// Spec: https://webassembly.github.io/spec/core/binary/modules.html
@ -396,16 +419,6 @@ func writeCodeSec(ctxt *ld.Link, fns []*wasmFunc) {
func writeDataSec(ctxt *ld.Link) {
sizeOffset := writeSecHeader(ctxt, sectionData)
sections := []*sym.Section{
ctxt.Syms.Lookup("runtime.rodata", 0).Sect,
ctxt.Syms.Lookup("runtime.typelink", 0).Sect,
ctxt.Syms.Lookup("runtime.itablink", 0).Sect,
ctxt.Syms.Lookup("runtime.symtab", 0).Sect,
ctxt.Syms.Lookup("runtime.pclntab", 0).Sect,
ctxt.Syms.Lookup("runtime.noptrdata", 0).Sect,
ctxt.Syms.Lookup("runtime.data", 0).Sect,
}
type dataSegment struct {
offset int32
data []byte
@ -420,9 +433,9 @@ func writeDataSec(ctxt *ld.Link) {
const maxNumSegments = 100000
var segments []*dataSegment
for secIndex, sec := range sections {
data := ld.DatblkBytes(ctxt, int64(sec.Vaddr), int64(sec.Length))
offset := int32(sec.Vaddr)
for secIndex, ds := range dataSects {
data := ds.data
offset := int32(ds.sect.Vaddr)
// skip leading zeroes
for len(data) > 0 && data[0] == 0 {
@ -433,7 +446,7 @@ func writeDataSec(ctxt *ld.Link) {
for len(data) > 0 {
dataLen := int32(len(data))
var segmentEnd, zeroEnd int32
if len(segments)+(len(sections)-secIndex) == maxNumSegments {
if len(segments)+(len(dataSects)-secIndex) == maxNumSegments {
segmentEnd = dataLen
zeroEnd = dataLen
} else {