cmd/link: collect itablinks as a slice in moduledata

See #14874

This change tells the linker to collect all the itablink symbols and
collect them so that moduledata can have a slice of all compiler
generated itabs.

The logic is shamelessly adapted from what is done with typelink symbols.

Change-Id: Ie93b59acf0fcba908a876d506afbf796f222dbac
Reviewed-on: https://go-review.googlesource.com/20889
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/internal/goobj/read.go b/src/cmd/internal/goobj/read.go
index 6a906a46276642af78d1b3001b02725e138f5543..2506f07de206ab26f2ebf78c4223a510764ce2ac 100644 (file)
--- a/src/cmd/internal/goobj/read.go
+++ b/src/cmd/internal/goobj/read.go
@@ -43,6 +43,7 @@ const (
        SRODATA    SymKind = obj.SRODATA
        SFUNCTAB   SymKind = obj.SFUNCTAB
        STYPELINK  SymKind = obj.STYPELINK
+       SITABLINK  SymKind = obj.SITABLINK
        SSYMTAB    SymKind = obj.SSYMTAB // TODO: move to unmapped section
        SPCLNTAB   SymKind = obj.SPCLNTAB
        SELFROSECT SymKind = obj.SELFROSECT
@@ -106,6 +107,7 @@ var symKindStrings = []string{
        STLSBSS:           "STLSBSS",
        STYPE:             "STYPE",
        STYPELINK:         "STYPELINK",
+       SITABLINK:         "SITABLINK",
        SWINDOWS:          "SWINDOWS",
        SXREF:             "SXREF",
 }

diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 11d451abb26a6e3f923239782bf41fa2c32357cb..152a2acea00e9a0c9d6e83b2e65db4c27e0b5d86 100644 (file)
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -397,6 +397,7 @@ const (
        SFUNCTABRELRO
 
        STYPELINK
+       SITABLINK
        SSYMTAB
        SPCLNTAB
        SELFROSECT

diff --git a/src/cmd/internal/objfile/goobj.go b/src/cmd/internal/objfile/goobj.go
index cf89ebb9e4a19e0cc1fa540cabd6fa88b3122f42..46e5f4e86651cee528c5b04437f3a265d0b9e906 100644 (file)
--- a/src/cmd/internal/objfile/goobj.go
+++ b/src/cmd/internal/objfile/goobj.go
@@ -41,7 +41,7 @@ func (f *goobjFile) symbols() ([]Sym, error) {
                switch s.Kind {
                case goobj.STEXT, goobj.SELFRXSECT:
                        sym.Code = 'T'
-               case goobj.STYPE, goobj.SSTRING, goobj.SGOSTRING, goobj.SGOFUNC, goobj.SRODATA, goobj.SFUNCTAB, goobj.STYPELINK, goobj.SSYMTAB, goobj.SPCLNTAB, goobj.SELFROSECT:
+               case goobj.STYPE, goobj.SSTRING, goobj.SGOSTRING, goobj.SGOFUNC, goobj.SRODATA, goobj.SFUNCTAB, goobj.STYPELINK, goobj.SITABLINK, goobj.SSYMTAB, goobj.SPCLNTAB, goobj.SELFROSECT:
                        sym.Code = 'R'
                case goobj.SMACHOPLT, goobj.SELFSECT, goobj.SMACHO, goobj.SMACHOGOT, goobj.SNOPTRDATA, goobj.SINITARR, goobj.SDATA, goobj.SWINDOWS:
                        sym.Code = 'D'

diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index a5901c52c6ea53e6f5d33ebb48ff539c11170481..cacec8f8fe6c39066f9b0d141b77ccb3eebeeda4 100644 (file)
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -1605,6 +1605,24 @@ func dodata() {
 
        sect.Length = uint64(datsize) - sect.Vaddr
 
+       /* itablink */
+       sect = addsection(segro, relro_prefix+".itablink", relro_perms)
+
+       sect.Align = maxalign(s, obj.SITABLINK)
+       datsize = Rnd(datsize, int64(sect.Align))
+       sect.Vaddr = uint64(datsize)
+       Linklookup(Ctxt, "runtime.itablink", 0).Sect = sect
+       Linklookup(Ctxt, "runtime.eitablink", 0).Sect = sect
+       for ; s != nil && s.Type == obj.SITABLINK; s = s.Next {
+               datsize = aligndatsize(datsize, s)
+               s.Sect = sect
+               s.Type = obj.SRODATA
+               s.Value = int64(uint64(datsize) - sect.Vaddr)
+               growdatsize(&datsize, s)
+       }
+
+       sect.Length = uint64(datsize) - sect.Vaddr
+
        /* gosymtab */
        sect = addsection(segro, relro_prefix+".gosymtab", relro_perms)
 
@@ -1835,7 +1853,8 @@ func address() {
                // object on elf systems.
                typelink = typelink.Next
        }
-       symtab := typelink.Next
+       itablink := typelink.Next
+       symtab := itablink.Next
        pclntab := symtab.Next
 
        var sub *LSym
@@ -1862,6 +1881,8 @@ func address() {
        xdefine("runtime.erodata", obj.SRODATA, int64(rodata.Vaddr+rodata.Length))
        xdefine("runtime.typelink", obj.SRODATA, int64(typelink.Vaddr))
        xdefine("runtime.etypelink", obj.SRODATA, int64(typelink.Vaddr+typelink.Length))
+       xdefine("runtime.itablink", obj.SRODATA, int64(itablink.Vaddr))
+       xdefine("runtime.eitablink", obj.SRODATA, int64(itablink.Vaddr+itablink.Length))
 
        sym := Linklookup(Ctxt, "runtime.gcdata", 0)
        sym.Attr |= AttrLocal

diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go
index f99f5e89846ea3f3fa3be0ca02cce795567acbd1..e1badc2a48c7f91924fc1755803785afb4d74e25 100644 (file)
--- a/src/cmd/link/internal/ld/deadcode.go
+++ b/src/cmd/link/internal/ld/deadcode.go
@@ -107,10 +107,11 @@ func deadcode(ctxt *Link) {
        }
 
        if Buildmode != BuildmodeShared {
-               // Keep a typelink if the symbol it points at is being kept.
-               // (When BuildmodeShared, always keep typelinks.)
+               // Keep a typelink or itablink if the symbol it points at is being kept.
+               // (When BuildmodeShared, always keep typelinks and itablinks.)
                for _, s := range ctxt.Allsym {
-                       if strings.HasPrefix(s.Name, "go.typelink.") {
+                       if strings.HasPrefix(s.Name, "go.typelink.") ||
+                               strings.HasPrefix(s.Name, "go.itablink.") {
                                s.Attr.Set(AttrReachable, len(s.R) == 1 && s.R[0].Sym.Attr.Reachable())
                        }
                }

diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index c5f68273f49958652ed1959a65712cee6dd2ded0..6db7898624fc3614dc08316142bbaead482c30a8 100644 (file)
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -1740,6 +1740,7 @@ func doelf() {
                relro_prefix = ".data.rel.ro"
        }
        Addstring(shstrtab, relro_prefix+".typelink")
+       Addstring(shstrtab, relro_prefix+".itablink")
        Addstring(shstrtab, relro_prefix+".gosymtab")
        Addstring(shstrtab, relro_prefix+".gopclntab")
 
@@ -1751,6 +1752,7 @@ func doelf() {
                        Addstring(shstrtab, ".rela.text")
                        Addstring(shstrtab, ".rela.rodata")
                        Addstring(shstrtab, ".rela"+relro_prefix+".typelink")
+                       Addstring(shstrtab, ".rela"+relro_prefix+".itablink")
                        Addstring(shstrtab, ".rela"+relro_prefix+".gosymtab")
                        Addstring(shstrtab, ".rela"+relro_prefix+".gopclntab")
                        Addstring(shstrtab, ".rela.noptrdata")
@@ -1763,6 +1765,7 @@ func doelf() {
                        Addstring(shstrtab, ".rel.text")
                        Addstring(shstrtab, ".rel.rodata")
                        Addstring(shstrtab, ".rel"+relro_prefix+".typelink")
+                       Addstring(shstrtab, ".rel"+relro_prefix+".itablink")
                        Addstring(shstrtab, ".rel"+relro_prefix+".gosymtab")
                        Addstring(shstrtab, ".rel"+relro_prefix+".gopclntab")
                        Addstring(shstrtab, ".rel.noptrdata")

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 5121a873b2975c2a00e3c8dc403da0b6f031c03c..5ec5c98290c3d1d96d5ba6266666411575b8059f 100644 (file)
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1930,6 +1930,7 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
                        obj.SGCBITSRELRO,
                        obj.SRODATARELRO,
                        obj.STYPELINK,
+                       obj.SITABLINK,
                        obj.SWINDOWS:
                        if !s.Attr.Reachable() {
                                continue

diff --git a/src/cmd/link/internal/ld/symtab.go b/src/cmd/link/internal/ld/symtab.go
index 6d1175b1c66109e26afee1f8c2ff839a241bbe14..c44b67d50dace73aae09d835363288cb43a625a0 100644 (file)
--- a/src/cmd/link/internal/ld/symtab.go
+++ b/src/cmd/link/internal/ld/symtab.go
@@ -342,6 +342,8 @@ func symtab() {
        xdefine("runtime.etext", obj.STEXT, 0)
        xdefine("runtime.typelink", obj.SRODATA, 0)
        xdefine("runtime.etypelink", obj.SRODATA, 0)
+       xdefine("runtime.itablink", obj.SRODATA, 0)
+       xdefine("runtime.eitablink", obj.SRODATA, 0)
        xdefine("runtime.rodata", obj.SRODATA, 0)
        xdefine("runtime.erodata", obj.SRODATA, 0)
        xdefine("runtime.noptrdata", obj.SNOPTRDATA, 0)
@@ -428,6 +430,9 @@ func symtab() {
        symtypelink := Linklookup(Ctxt, "runtime.typelink", 0)
        symtypelink.Type = obj.STYPELINK
 
+       symitablink := Linklookup(Ctxt, "runtime.itablink", 0)
+       symitablink.Type = obj.SITABLINK
+
        symt = Linklookup(Ctxt, "runtime.symtab", 0)
        symt.Attr |= AttrLocal
        symt.Type = obj.SSYMTAB
@@ -435,6 +440,7 @@ func symtab() {
        symt.Attr |= AttrReachable
 
        ntypelinks := 0
+       nitablinks := 0
 
        // assign specific types so that they sort together.
        // within a type they sort by size, so the .* symbols
@@ -463,6 +469,13 @@ func symtab() {
                        s.Outer = symtypelink
                }
 
+               if strings.HasPrefix(s.Name, "go.itablink.") {
+                       nitablinks++
+                       s.Type = obj.SITABLINK
+                       s.Attr |= AttrHidden
+                       s.Outer = symitablink
+               }
+
                if strings.HasPrefix(s.Name, "go.string.") {
                        s.Type = obj.SGOSTRING
                        s.Attr |= AttrHidden
@@ -543,6 +556,10 @@ func symtab() {
        Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.typelink", 0))
        adduint(Ctxt, moduledata, uint64(ntypelinks))
        adduint(Ctxt, moduledata, uint64(ntypelinks))
+       // The itablinks slice
+       Addaddr(Ctxt, moduledata, Linklookup(Ctxt, "runtime.itablink", 0))
+       adduint(Ctxt, moduledata, uint64(nitablinks))
+       adduint(Ctxt, moduledata, uint64(nitablinks))
        if len(Ctxt.Shlibs) > 0 {
                thismodulename := filepath.Base(outfile)
                switch Buildmode {

diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
index cd328eb899bf5f1aba28877288f387d459d5126e..158bdcea0dace95bfcdf2dc282f32206b75494f1 100644 (file)
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -129,6 +129,7 @@ type moduledata struct {
        end, gcdata, gcbss    uintptr
 
        typelinks []*_type
+       itablinks []*itab
 
        modulename   string
        modulehashes []modulehash