cmd/link: support trampoline insertion for PLT calls on ARM

This is CL 314452, for ARM.

Fixes #30949.

Change-Id: Ib4e46a5bd11c698c4f8ea3bc4e7a605d7a538efc
Reviewed-on: https://go-review.googlesource.com/c/go/+/314455
Trust: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

diff --git a/src/cmd/link/internal/arm/asm.go b/src/cmd/link/internal/arm/asm.go
index 33b20febd7780434c36b7879c0eafbd38c2f9224..ab780214bb65f547c3dc89d7446939fade4e7c63 100644 (file)
--- a/src/cmd/link/internal/arm/asm.go
+++ b/src/cmd/link/internal/arm/asm.go
@@ -111,7 +111,7 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loade
                        return false
                }
 
-               // Handle relocations found in ELF object files.
+       // Handle relocations found in ELF object files.
        case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PLT32):
                su := ldr.MakeSymbolUpdater(s)
                su.SetRelocType(rIdx, objabi.R_CALLARM)
@@ -237,6 +237,21 @@ func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loade
                        su.SetRelocSym(rIdx, 0)
                        return true
                }
+
+       case objabi.R_GOTPCREL:
+               if target.IsExternal() {
+                       // External linker will do this relocation.
+                       return true
+               }
+               if targType != sym.SDYNIMPORT {
+                       ldr.Errorf(s, "R_GOTPCREL target is not SDYNIMPORT symbol: %v", ldr.SymName(targ))
+               }
+               ld.AddGotSym(target, ldr, syms, targ, uint32(elf.R_ARM_GLOB_DAT))
+               su := ldr.MakeSymbolUpdater(s)
+               su.SetRelocType(rIdx, objabi.R_PCREL)
+               su.SetRelocSym(rIdx, syms.GOT)
+               su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ)))
+               return true
        }
 
        return false
@@ -369,6 +384,12 @@ func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
        relocs := ldr.Relocs(s)
        r := relocs.At(ri)
        switch r.Type() {
+       case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL),
+               objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24),
+               objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24):
+               // Host object relocations that will be turned into a PLT call.
+               // The PLT may be too far. Insert a trampoline for them.
+               fallthrough
        case objabi.R_CALLARM:
                var t int64
                // ldr.SymValue(rs) == 0 indicates a cross-package jump to a function that is not yet
@@ -415,7 +436,7 @@ func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
                                // trampoline does not exist, create one
                                trampb := ldr.MakeSymbolUpdater(tramp)
                                ctxt.AddTramp(trampb)
-                               if ctxt.DynlinkingGo() {
+                               if ctxt.DynlinkingGo() || ldr.SymType(rs) == sym.SDYNIMPORT {
                                        if immrot(uint32(offset)) == 0 {
                                                ctxt.Errorf(s, "odd offset in dynlink direct call: %v+%d", ldr.SymName(rs), offset)
                                        }

diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index 1b5eb2f7e3107a00cf8f083d33eafda1af0a6eb3..1c3af946920ed80565b63795ca5e65e3861aed37 100644 (file)
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -134,6 +134,12 @@ func isPLTCall(rt objabi.RelocType) bool {
                objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_JUMP26),
                objabi.MachoRelocOffset + MACHO_ARM64_RELOC_BRANCH26*2 + pcrel:
                return true
+
+       // ARM
+       case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL),
+               objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24),
+               objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24):
+               return true
        }
        // TODO: other architectures.
        return false