cmd/link, runtime: arm implementation of addmoduledata

Change-Id: I3975e10c2445e23c2798a7203a877ff2de3427c7
Reviewed-on: https://go-review.googlesource.com/14189
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/link/internal/arm/asm.go b/src/cmd/link/internal/arm/asm.go
index 5507312a1b1e836f12073c19c62ef8674b6157aa..8ffa656208a64755de93e6bdbcd9cfc907d33b7f 100644 (file)
--- a/src/cmd/link/internal/arm/asm.go
+++ b/src/cmd/link/internal/arm/asm.go
@@ -37,7 +37,75 @@ import (
        "log"
 )
 
+// This assembler:
+//
+//         .align 2
+// local.dso_init:
+//         ldr r0, .Lmoduledata
+// .Lloadfrom:
+//         ldr r0, [r0]
+//         b runtime.addmoduledata@plt
+// .align 2
+// .Lmoduledata:
+//         .word local.moduledata(GOT_PREL) + (. - (.Lloadfrom + 4))
+// assembles to:
+//
+// 00000000 <local.dso_init>:
+//    0:        e59f0004        ldr     r0, [pc, #4]    ; c <local.dso_init+0xc>
+//    4:        e5900000        ldr     r0, [r0]
+//    8:        eafffffe        b       0 <runtime.addmoduledata>
+//                      8: R_ARM_JUMP24 runtime.addmoduledata
+//    c:        00000004        .word   0x00000004
+//                      c: R_ARM_GOT_PREL       local.moduledata
+
 func gentext() {
+       if !ld.DynlinkingGo() {
+               return
+       }
+       addmoduledata := ld.Linklookup(ld.Ctxt, "runtime.addmoduledata", 0)
+       if addmoduledata.Type == obj.STEXT {
+               // we're linking a module containing the runtime -> no need for
+               // an init function
+               return
+       }
+       addmoduledata.Reachable = true
+       initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
+       initfunc.Type = obj.STEXT
+       initfunc.Local = true
+       initfunc.Reachable = true
+       o := func(op uint32) {
+               ld.Adduint32(ld.Ctxt, initfunc, op)
+       }
+       o(0xe59f0004)
+       o(0xe08f0000)
+
+       o(0xeafffffe)
+       rel := ld.Addrel(initfunc)
+       rel.Off = 8
+       rel.Siz = 4
+       rel.Sym = ld.Linklookup(ld.Ctxt, "runtime.addmoduledata", 0)
+       rel.Type = obj.R_CALLARM
+       rel.Add = 0xeafffffe // vomit
+
+       o(0x00000000)
+       rel = ld.Addrel(initfunc)
+       rel.Off = 12
+       rel.Siz = 4
+       rel.Sym = ld.Ctxt.Moduledata
+       rel.Type = obj.R_PCREL
+       rel.Add = 4
+
+       if ld.Ctxt.Etextp != nil {
+               ld.Ctxt.Etextp.Next = initfunc
+       } else {
+               ld.Ctxt.Textp = initfunc
+       }
+       ld.Ctxt.Etextp = initfunc
+       initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
+       initarray_entry.Reachable = true
+       initarray_entry.Local = true
+       initarray_entry.Type = obj.SINITARR
+       ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
 }
 
 // Preserve highest 8 bits of a, and do addition to lower 24-bit
@@ -228,6 +296,13 @@ func elfreloc1(r *ld.Reloc, sectoff int64) int {
 
        case obj.R_TLS_IE:
                ld.Thearch.Lput(ld.R_ARM_TLS_IE32 | uint32(elfsym)<<8)
+
+       case obj.R_GOTPCREL:
+               if r.Siz == 4 {
+                       ld.Thearch.Lput(ld.R_ARM_GOT_PREL | uint32(elfsym)<<8)
+               } else {
+                       return -1
+               }
        }
 
        return 0

diff --git a/src/runtime/asm_arm.s b/src/runtime/asm_arm.s
index 8472090d8be110a8378b3b079453cd631eeb6e45..62f2a276e775411dd5d8058f76380942cec7dfc5 100644 (file)
--- a/src/runtime/asm_arm.s
+++ b/src/runtime/asm_arm.s
@@ -1076,3 +1076,14 @@ TEXT runtime·usplitR0(SB),NOSPLIT,$0
 
 TEXT runtime·sigreturn(SB),NOSPLIT,$0-4
         RET
+
+#ifndef GOOS_nacl
+// This is called from .init_array and follows the platform, not Go, ABI.
+TEXT runtime·addmoduledata(SB),NOSPLIT,$0-4
+       MOVW    R9, saver9-4(SP) // The access to global variables below implicitly uses R9, which is callee-save
+       MOVW    runtime·lastmoduledatap(SB), R1
+       MOVW    R0, moduledata_next(R1)
+       MOVW    R0, runtime·lastmoduledatap(SB)
+       MOVW    saver9-4(SP), R9
+       RET
+#endif