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

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>

diff --git a/src/cmd/link/internal/amd64/asm.go b/src/cmd/link/internal/amd64/asm.go
index e2a66daf4f782e4352780032a4907cbe3ef824b5..95831d6dd0c773d5bad2d98025c99a5a30aaf9ea 100644 (file)
--- a/src/cmd/link/internal/amd64/asm.go
+++ b/src/cmd/link/internal/amd64/asm.go
@@ -684,7 +684,7 @@ func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
        }
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }

diff --git a/src/cmd/link/internal/arm/asm.go b/src/cmd/link/internal/arm/asm.go
index e1edc9e45da66c761c35b132b1cf30371cea1bc4..7665cc59f04cf3ea1ef8f21589cde3e104205a9e 100644 (file)
--- a/src/cmd/link/internal/arm/asm.go
+++ b/src/cmd/link/internal/arm/asm.go
@@ -682,7 +682,7 @@ func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
        }
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }

diff --git a/src/cmd/link/internal/arm64/asm.go b/src/cmd/link/internal/arm64/asm.go
index a0f06b6aa67aaebae214d4b5a19381ead36fdf1d..fbcbc9c8c34d127b4893171615dfffa31de8e1d4 100644 (file)
--- a/src/cmd/link/internal/arm64/asm.go
+++ b/src/cmd/link/internal/arm64/asm.go
@@ -830,7 +830,7 @@ func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
        }
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }

diff --git a/src/cmd/link/internal/ld/data2.go b/src/cmd/link/internal/ld/data2.go
index 79badd5fdd19aa4d11e2ff0e43cece24d2000a01..2aba40c231e547bb578467d415f1d07169d081f5 100644 (file)
--- a/src/cmd/link/internal/ld/data2.go
+++ b/src/cmd/link/internal/ld/data2.go
@@ -58,15 +58,6 @@ func relocsym2(target *Target, ldr *loader.Loader, err *ErrorReporter, syms *Arc
        if len(s.R) == 0 {
                return
        }
-       if target.IsWasm() && s.Attr.ReadOnly() {
-               // The symbol's content is backed by read-only memory.
-               // Copy it to writable memory to apply relocations.
-               // Only need to do this on Wasm. On other platforms we
-               // apply relocations to the output buffer, which is
-               // always writeable.
-               s.P = append([]byte(nil), s.P...)
-               // No need to unset AttrReadOnly because it will not be used.
-       }
        for ri := int32(0); ri < int32(len(s.R)); ri++ {
                r := &s.R[ri]
                if r.Done {

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 7264f9383e89cc2575e695366b310391ee5a2a4b..57b9e8cb24c1317a4459542fd8fdabbfdae9b43a 100644 (file)
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -265,7 +265,7 @@ type Arch struct {
        // file. Typically, Asmb writes most of the content (sections and
        // segments), for which we have computed the size and offset. Asmb2
        // writes the rest.
-       Asmb  func(*Link)
+       Asmb  func(*Link, *loader.Loader)
        Asmb2 func(*Link)
 
        Elfreloc1   func(*Link, *sym.Reloc, int64) bool

diff --git a/src/cmd/link/internal/ld/main.go b/src/cmd/link/internal/ld/main.go
index 6c5a18c3595676032e10791c268e271256a49c05..48fea57cc9544f32b71637ef235308c00286bef2 100644 (file)
--- a/src/cmd/link/internal/ld/main.go
+++ b/src/cmd/link/internal/ld/main.go
@@ -325,7 +325,7 @@ func Main(arch *sys.Arch, theArch Arch) {
        // Asmb will redirect symbols to the output file mmap, and relocations
        // will be applied directly there.
        bench.Start("Asmb")
-       thearch.Asmb(ctxt)
+       thearch.Asmb(ctxt, ctxt.loader)
        bench.Start("reloc")
        ctxt.reloc()
        bench.Start("Asmb2")

diff --git a/src/cmd/link/internal/mips/asm.go b/src/cmd/link/internal/mips/asm.go
index 21a57ccbb0d182345685c87985c74272813bc123..928167870442abee54ee3c41cac8e066bd7f0540 100644 (file)
--- a/src/cmd/link/internal/mips/asm.go
+++ b/src/cmd/link/internal/mips/asm.go
@@ -164,7 +164,7 @@ func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym
        return -1
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }

diff --git a/src/cmd/link/internal/mips64/asm.go b/src/cmd/link/internal/mips64/asm.go
index 0a2a3c11f3eff41195fac9ef1b7c339957964853..615851b564a6a80952c9cad1761b91a8999e470e 100644 (file)
--- a/src/cmd/link/internal/mips64/asm.go
+++ b/src/cmd/link/internal/mips64/asm.go
@@ -170,7 +170,7 @@ func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym
        return -1
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }

diff --git a/src/cmd/link/internal/ppc64/asm.go b/src/cmd/link/internal/ppc64/asm.go
index be124acaf86b7565e1a323b55b7e8ec8da8fca4c..6b6e1294d30862b635c9ecaf140e0f9c8f614bbf 100644 (file)
--- a/src/cmd/link/internal/ppc64/asm.go
+++ b/src/cmd/link/internal/ppc64/asm.go
@@ -1082,7 +1082,7 @@ func ensureglinkresolver2(ctxt *ld.Link, ldr *loader.Loader) *loader.SymbolBuild
        return glink
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }

diff --git a/src/cmd/link/internal/riscv64/asm.go b/src/cmd/link/internal/riscv64/asm.go
index 51cc5980c89a75a76a93fb4aab1251a2252fa685..5183de8d6b73d6914c562bcc745bc9ee98de2f7e 100644 (file)
--- a/src/cmd/link/internal/riscv64/asm.go
+++ b/src/cmd/link/internal/riscv64/asm.go
@@ -98,7 +98,7 @@ func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym
        return -1
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }

diff --git a/src/cmd/link/internal/s390x/asm.go b/src/cmd/link/internal/s390x/asm.go
index 59c49b4537698686bfea0b83879495c46c340a83..ac634f99e396a6349cbccda3d56701dd36fdc2b7 100644 (file)
--- a/src/cmd/link/internal/s390x/asm.go
+++ b/src/cmd/link/internal/s390x/asm.go
@@ -485,7 +485,7 @@ func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
        }
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }

diff --git a/src/cmd/link/internal/wasm/asm.go b/src/cmd/link/internal/wasm/asm.go
index 7f8742d00823648701324e5eb06bb437db53c099..1eb3291db6667bd15a3129181383abba8726d938 100644 (file)
--- a/src/cmd/link/internal/wasm/asm.go
+++ b/src/cmd/link/internal/wasm/asm.go
@@ -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 {

diff --git a/src/cmd/link/internal/x86/asm.go b/src/cmd/link/internal/x86/asm.go
index 03c73671b8804e92ece2ceeea213db19475590fc..069d2bc31ce05fefa66206efb986c1e098c85f84 100644 (file)
--- a/src/cmd/link/internal/x86/asm.go
+++ b/src/cmd/link/internal/x86/asm.go
@@ -564,7 +564,7 @@ func addgotsym2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s load
        }
 }
 
-func asmb(ctxt *ld.Link) {
+func asmb(ctxt *ld.Link, _ *loader.Loader) {
        if ctxt.IsELF {
                ld.Asmbelfsetup()
        }