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 6a906a4..2506f07 100644
--- a/src/cmd/internal/goobj/read.go
+++ b/src/cmd/internal/goobj/read.go
@@ -43,6 +43,7 @@
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 @@
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 11d451a..152a2ac 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -397,6 +397,7 @@
SFUNCTABRELRO
STYPELINK
+ SITABLINK
SSYMTAB
SPCLNTAB
SELFROSECT
diff --git a/src/cmd/internal/objfile/goobj.go b/src/cmd/internal/objfile/goobj.go
index cf89ebb..46e5f4e 100644
--- a/src/cmd/internal/objfile/goobj.go
+++ b/src/cmd/internal/objfile/goobj.go
@@ -41,7 +41,7 @@
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 a5901c5..cacec8f 100644
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -1605,6 +1605,24 @@
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 @@
// 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 @@
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 f99f5e8..e1badc2 100644
--- a/src/cmd/link/internal/ld/deadcode.go
+++ b/src/cmd/link/internal/ld/deadcode.go
@@ -107,10 +107,11 @@
}
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 c5f6827..6db7898 100644
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -1740,6 +1740,7 @@
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 @@
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 @@
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 5121a87..5ec5c98 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1930,6 +1930,7 @@
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 6d1175b..c44b67d 100644
--- a/src/cmd/link/internal/ld/symtab.go
+++ b/src/cmd/link/internal/ld/symtab.go
@@ -342,6 +342,8 @@
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 @@
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 @@
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 @@
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 @@
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 cd328eb..158bdce 100644
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -129,6 +129,7 @@
end, gcdata, gcbss uintptr
typelinks []*_type
+ itablinks []*itab
modulename string
modulehashes []modulehash
