1// Inferno utils/5l/asm.c 2// https://bitbucket.org/inferno-os/inferno-os/src/master/utils/5l/asm.c 3// 4// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved. 5// Portions Copyright © 1995-1997 C H Forsyth ([email protected]) 6// Portions Copyright © 1997-1999 Vita Nuova Limited 7// Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com) 8// Portions Copyright © 2004,2006 Bruce Ellis 9// Portions Copyright © 2005-2007 C H Forsyth ([email protected]) 10// Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others 11// Portions Copyright © 2009 The Go Authors. All rights reserved. 12// 13// Permission is hereby granted, free of charge, to any person obtaining a copy 14// of this software and associated documentation files (the "Software"), to deal 15// in the Software without restriction, including without limitation the rights 16// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 17// copies of the Software, and to permit persons to whom the Software is 18// furnished to do so, subject to the following conditions: 19// 20// The above copyright notice and this permission notice shall be included in 21// all copies or substantial portions of the Software. 22// 23// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 24// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 25// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 26// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 27// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 28// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 29// THE SOFTWARE. 30 31package arm 32 33import ( 34 "cmd/internal/objabi" 35 "cmd/internal/sys" 36 "cmd/link/internal/ld" 37 "cmd/link/internal/loader" 38 "cmd/link/internal/sym" 39 "debug/elf" 40 "fmt" 41 "log" 42) 43 44// This assembler: 45// 46// .align 2 47// local.dso_init: 48// ldr r0, .Lmoduledata 49// .Lloadfrom: 50// ldr r0, [r0] 51// b runtime.addmoduledata@plt 52// .align 2 53// .Lmoduledata: 54// .word local.moduledata(GOT_PREL) + (. - (.Lloadfrom + 4)) 55// assembles to: 56// 57// 00000000 <local.dso_init>: 58// 0: e59f0004 ldr r0, [pc, #4] ; c <local.dso_init+0xc> 59// 4: e5900000 ldr r0, [r0] 60// 8: eafffffe b 0 <runtime.addmoduledata> 61// 8: R_ARM_JUMP24 runtime.addmoduledata 62// c: 00000004 .word 0x00000004 63// c: R_ARM_GOT_PREL local.moduledata 64 65func gentext(ctxt *ld.Link, ldr *loader.Loader) { 66 initfunc, addmoduledata := ld.PrepareAddmoduledata(ctxt) 67 if initfunc == nil { 68 return 69 } 70 71 o := func(op uint32) { 72 initfunc.AddUint32(ctxt.Arch, op) 73 } 74 o(0xe59f0004) 75 o(0xe08f0000) 76 77 o(0xeafffffe) 78 rel, _ := initfunc.AddRel(objabi.R_CALLARM) 79 rel.SetOff(8) 80 rel.SetSiz(4) 81 rel.SetSym(addmoduledata) 82 rel.SetAdd(0xeafffffe) // vomit 83 84 o(0x00000000) 85 86 rel2, _ := initfunc.AddRel(objabi.R_PCREL) 87 rel2.SetOff(12) 88 rel2.SetSiz(4) 89 rel2.SetSym(ctxt.Moduledata) 90 rel2.SetAdd(4) 91} 92 93// Preserve highest 8 bits of a, and do addition to lower 24-bit 94// of a and b; used to adjust ARM branch instruction's target. 95func braddoff(a int32, b int32) int32 { 96 return int32((uint32(a))&0xff000000 | 0x00ffffff&uint32(a+b)) 97} 98 99func adddynrel(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r loader.Reloc, rIdx int) bool { 100 101 targ := r.Sym() 102 var targType sym.SymKind 103 if targ != 0 { 104 targType = ldr.SymType(targ) 105 } 106 107 switch r.Type() { 108 default: 109 if r.Type() >= objabi.ElfRelocOffset { 110 ldr.Errorf(s, "unexpected relocation type %d (%s)", r.Type(), sym.RelocName(target.Arch, r.Type())) 111 return false 112 } 113 114 // Handle relocations found in ELF object files. 115 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PLT32): 116 su := ldr.MakeSymbolUpdater(s) 117 su.SetRelocType(rIdx, objabi.R_CALLARM) 118 119 if targType == sym.SDYNIMPORT { 120 addpltsym(target, ldr, syms, targ) 121 su.SetRelocSym(rIdx, syms.PLT) 122 su.SetRelocAdd(rIdx, int64(braddoff(int32(r.Add()), ldr.SymPlt(targ)/4))) 123 } 124 125 return true 126 127 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_THM_PC22): // R_ARM_THM_CALL 128 ld.Exitf("R_ARM_THM_CALL, are you using -marm?") 129 return false 130 131 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOT32): // R_ARM_GOT_BREL 132 if targType != sym.SDYNIMPORT { 133 addgotsyminternal(target, ldr, syms, targ) 134 } else { 135 ld.AddGotSym(target, ldr, syms, targ, uint32(elf.R_ARM_GLOB_DAT)) 136 } 137 138 su := ldr.MakeSymbolUpdater(s) 139 su.SetRelocType(rIdx, objabi.R_CONST) // write r->add during relocsym 140 su.SetRelocSym(rIdx, 0) 141 su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ))) 142 return true 143 144 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOT_PREL): // GOT(nil) + A - nil 145 if targType != sym.SDYNIMPORT { 146 addgotsyminternal(target, ldr, syms, targ) 147 } else { 148 ld.AddGotSym(target, ldr, syms, targ, uint32(elf.R_ARM_GLOB_DAT)) 149 } 150 su := ldr.MakeSymbolUpdater(s) 151 su.SetRelocType(rIdx, objabi.R_PCREL) 152 su.SetRelocSym(rIdx, syms.GOT) 153 su.SetRelocAdd(rIdx, r.Add()+4+int64(ldr.SymGot(targ))) 154 return true 155 156 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOTOFF): // R_ARM_GOTOFF32 157 su := ldr.MakeSymbolUpdater(s) 158 su.SetRelocType(rIdx, objabi.R_GOTOFF) 159 return true 160 161 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_GOTPC): // R_ARM_BASE_PREL 162 su := ldr.MakeSymbolUpdater(s) 163 su.SetRelocType(rIdx, objabi.R_PCREL) 164 su.SetRelocSym(rIdx, syms.GOT) 165 su.SetRelocAdd(rIdx, r.Add()+4) 166 return true 167 168 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL): 169 su := ldr.MakeSymbolUpdater(s) 170 su.SetRelocType(rIdx, objabi.R_CALLARM) 171 if targType == sym.SDYNIMPORT { 172 addpltsym(target, ldr, syms, targ) 173 su.SetRelocSym(rIdx, syms.PLT) 174 su.SetRelocAdd(rIdx, int64(braddoff(int32(r.Add()), ldr.SymPlt(targ)/4))) 175 } 176 return true 177 178 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_REL32): // R_ARM_REL32 179 su := ldr.MakeSymbolUpdater(s) 180 su.SetRelocType(rIdx, objabi.R_PCREL) 181 su.SetRelocAdd(rIdx, r.Add()+4) 182 return true 183 184 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_ABS32): 185 if targType == sym.SDYNIMPORT { 186 ldr.Errorf(s, "unexpected R_ARM_ABS32 relocation for dynamic symbol %s", ldr.SymName(targ)) 187 } 188 su := ldr.MakeSymbolUpdater(s) 189 su.SetRelocType(rIdx, objabi.R_ADDR) 190 return true 191 192 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24), 193 objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24): 194 su := ldr.MakeSymbolUpdater(s) 195 su.SetRelocType(rIdx, objabi.R_CALLARM) 196 if targType == sym.SDYNIMPORT { 197 addpltsym(target, ldr, syms, targ) 198 su.SetRelocSym(rIdx, syms.PLT) 199 su.SetRelocAdd(rIdx, int64(braddoff(int32(r.Add()), ldr.SymPlt(targ)/4))) 200 } 201 202 return true 203 } 204 205 // Handle references to ELF symbols from our own object files. 206 if targType != sym.SDYNIMPORT { 207 return true 208 } 209 210 // Reread the reloc to incorporate any changes in type above. 211 relocs := ldr.Relocs(s) 212 r = relocs.At(rIdx) 213 214 switch r.Type() { 215 case objabi.R_CALLARM: 216 if target.IsExternal() { 217 // External linker will do this relocation. 218 return true 219 } 220 addpltsym(target, ldr, syms, targ) 221 su := ldr.MakeSymbolUpdater(s) 222 su.SetRelocSym(rIdx, syms.PLT) 223 su.SetRelocAdd(rIdx, int64(braddoff(int32(r.Add()), ldr.SymPlt(targ)/4))) // TODO: don't use r.Add for instruction bytes (issue 19811) 224 return true 225 226 case objabi.R_ADDR: 227 if ldr.SymType(s) != sym.SDATA { 228 break 229 } 230 if target.IsElf() { 231 ld.Adddynsym(ldr, target, syms, targ) 232 rel := ldr.MakeSymbolUpdater(syms.Rel) 233 rel.AddAddrPlus(target.Arch, s, int64(r.Off())) 234 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(targ)), uint32(elf.R_ARM_GLOB_DAT))) // we need a nil + A dynamic reloc 235 su := ldr.MakeSymbolUpdater(s) 236 su.SetRelocType(rIdx, objabi.R_CONST) // write r->add during relocsym 237 su.SetRelocSym(rIdx, 0) 238 return true 239 } 240 241 case objabi.R_GOTPCREL: 242 if target.IsExternal() { 243 // External linker will do this relocation. 244 return true 245 } 246 if targType != sym.SDYNIMPORT { 247 ldr.Errorf(s, "R_GOTPCREL target is not SDYNIMPORT symbol: %v", ldr.SymName(targ)) 248 } 249 ld.AddGotSym(target, ldr, syms, targ, uint32(elf.R_ARM_GLOB_DAT)) 250 su := ldr.MakeSymbolUpdater(s) 251 su.SetRelocType(rIdx, objabi.R_PCREL) 252 su.SetRelocSym(rIdx, syms.GOT) 253 su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymGot(targ))) 254 return true 255 } 256 257 return false 258} 259 260func elfreloc1(ctxt *ld.Link, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym, r loader.ExtReloc, ri int, sectoff int64) bool { 261 out.Write32(uint32(sectoff)) 262 263 elfsym := ld.ElfSymForReloc(ctxt, r.Xsym) 264 siz := r.Size 265 switch r.Type { 266 default: 267 return false 268 case objabi.R_ADDR, objabi.R_DWARFSECREF: 269 if siz == 4 { 270 out.Write32(uint32(elf.R_ARM_ABS32) | uint32(elfsym)<<8) 271 } else { 272 return false 273 } 274 case objabi.R_PCREL: 275 if siz == 4 { 276 out.Write32(uint32(elf.R_ARM_REL32) | uint32(elfsym)<<8) 277 } else { 278 return false 279 } 280 case objabi.R_CALLARM: 281 if siz == 4 { 282 relocs := ldr.Relocs(s) 283 r := relocs.At(ri) 284 if r.Add()&0xff000000 == 0xeb000000 { // BL // TODO: using r.Add here is bad (issue 19811) 285 out.Write32(uint32(elf.R_ARM_CALL) | uint32(elfsym)<<8) 286 } else { 287 out.Write32(uint32(elf.R_ARM_JUMP24) | uint32(elfsym)<<8) 288 } 289 } else { 290 return false 291 } 292 case objabi.R_TLS_LE: 293 out.Write32(uint32(elf.R_ARM_TLS_LE32) | uint32(elfsym)<<8) 294 case objabi.R_TLS_IE: 295 out.Write32(uint32(elf.R_ARM_TLS_IE32) | uint32(elfsym)<<8) 296 case objabi.R_GOTPCREL: 297 if siz == 4 { 298 out.Write32(uint32(elf.R_ARM_GOT_PREL) | uint32(elfsym)<<8) 299 } else { 300 return false 301 } 302 } 303 304 return true 305} 306 307func elfsetupplt(ctxt *ld.Link, ldr *loader.Loader, plt, got *loader.SymbolBuilder, dynamic loader.Sym) { 308 if plt.Size() == 0 { 309 // str lr, [sp, #-4]! 310 plt.AddUint32(ctxt.Arch, 0xe52de004) 311 312 // ldr lr, [pc, #4] 313 plt.AddUint32(ctxt.Arch, 0xe59fe004) 314 315 // add lr, pc, lr 316 plt.AddUint32(ctxt.Arch, 0xe08fe00e) 317 318 // ldr pc, [lr, #8]! 319 plt.AddUint32(ctxt.Arch, 0xe5bef008) 320 321 // .word &GLOBAL_OFFSET_TABLE[0] - . 322 plt.AddPCRelPlus(ctxt.Arch, got.Sym(), 4) 323 324 // the first .plt entry requires 3 .plt.got entries 325 got.AddUint32(ctxt.Arch, 0) 326 327 got.AddUint32(ctxt.Arch, 0) 328 got.AddUint32(ctxt.Arch, 0) 329 } 330} 331 332func machoreloc1(*sys.Arch, *ld.OutBuf, *loader.Loader, loader.Sym, loader.ExtReloc, int64) bool { 333 return false 334} 335 336func pereloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym, r loader.ExtReloc, sectoff int64) bool { 337 rs := r.Xsym 338 rt := r.Type 339 340 if ldr.SymDynid(rs) < 0 { 341 ldr.Errorf(s, "reloc %d (%s) to non-coff symbol %s type=%d (%s)", rt, sym.RelocName(arch, rt), ldr.SymName(rs), ldr.SymType(rs), ldr.SymType(rs)) 342 return false 343 } 344 345 out.Write32(uint32(sectoff)) 346 out.Write32(uint32(ldr.SymDynid(rs))) 347 348 var v uint32 349 switch rt { 350 default: 351 // unsupported relocation type 352 return false 353 354 case objabi.R_DWARFSECREF: 355 v = ld.IMAGE_REL_ARM_SECREL 356 357 case objabi.R_ADDR: 358 v = ld.IMAGE_REL_ARM_ADDR32 359 360 case objabi.R_PEIMAGEOFF: 361 v = ld.IMAGE_REL_ARM_ADDR32NB 362 } 363 364 out.Write16(uint16(v)) 365 366 return true 367} 368 369// sign extend a 24-bit integer. 370func signext24(x int64) int32 { 371 return (int32(x) << 8) >> 8 372} 373 374// encode an immediate in ARM's imm12 format. copied from ../../../internal/obj/arm/asm5.go 375func immrot(v uint32) uint32 { 376 for i := 0; i < 16; i++ { 377 if v&^0xff == 0 { 378 return uint32(i<<8) | v | 1<<25 379 } 380 v = v<<2 | v>>30 381 } 382 return 0 383} 384 385// Convert the direct jump relocation r to refer to a trampoline if the target is too far. 386func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) { 387 relocs := ldr.Relocs(s) 388 r := relocs.At(ri) 389 switch r.Type() { 390 case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL), 391 objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24), 392 objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24): 393 // Host object relocations that will be turned into a PLT call. 394 // The PLT may be too far. Insert a trampoline for them. 395 fallthrough 396 case objabi.R_CALLARM: 397 var t int64 398 // ldr.SymValue(rs) == 0 indicates a cross-package jump to a function that is not yet 399 // laid out. Conservatively use a trampoline. This should be rare, as we lay out packages 400 // in dependency order. 401 if ldr.SymValue(rs) != 0 { 402 // Workaround for issue #58425: it appears that the 403 // external linker doesn't always take into account the 404 // relocation addend when doing reachability checks. This 405 // means that if you have a call from function XYZ at 406 // offset 8 to runtime.duffzero with addend 800 (for 407 // example), where the distance between the start of XYZ 408 // and the start of runtime.duffzero is just over the 409 // limit (by 100 bytes, say), you can get "relocation 410 // doesn't fit" errors from the external linker. To deal 411 // with this, ignore the addend when performing the 412 // distance calculation (this assumes that we're only 413 // handling backward jumps; ideally we might want to check 414 // both with and without the addend). 415 if ctxt.IsExternal() { 416 t = (ldr.SymValue(rs) - (ldr.SymValue(s) + int64(r.Off()))) / 4 417 } else { 418 // r.Add is the instruction 419 // low 24-bit encodes the target address 420 t = (ldr.SymValue(rs) + int64(signext24(r.Add()&0xffffff)*4) - (ldr.SymValue(s) + int64(r.Off()))) / 4 421 } 422 } 423 if t > 0x7fffff || t <= -0x800000 || ldr.SymValue(rs) == 0 || (*ld.FlagDebugTramp > 1 && ldr.SymPkg(s) != ldr.SymPkg(rs)) { 424 // direct call too far, need to insert trampoline. 425 // look up existing trampolines first. if we found one within the range 426 // of direct call, we can reuse it. otherwise create a new one. 427 offset := (signext24(r.Add()&0xffffff) + 2) * 4 428 var tramp loader.Sym 429 for i := 0; ; i++ { 430 oName := ldr.SymName(rs) 431 name := oName + fmt.Sprintf("%+d-tramp%d", offset, i) 432 tramp = ldr.LookupOrCreateSym(name, int(ldr.SymVersion(rs))) 433 ldr.SetAttrReachable(tramp, true) 434 if ldr.SymType(tramp) == sym.SDYNIMPORT { 435 // don't reuse trampoline defined in other module 436 continue 437 } 438 if oName == "runtime.deferreturn" { 439 ldr.SetIsDeferReturnTramp(tramp, true) 440 } 441 if ldr.SymValue(tramp) == 0 { 442 // either the trampoline does not exist -- we need to create one, 443 // or found one the address which is not assigned -- this will be 444 // laid down immediately after the current function. use this one. 445 break 446 } 447 448 t = (ldr.SymValue(tramp) - 8 - (ldr.SymValue(s) + int64(r.Off()))) / 4 449 if t >= -0x800000 && t < 0x7fffff { 450 // found an existing trampoline that is not too far 451 // we can just use it 452 break 453 } 454 } 455 if ldr.SymType(tramp) == 0 { 456 // trampoline does not exist, create one 457 trampb := ldr.MakeSymbolUpdater(tramp) 458 ctxt.AddTramp(trampb) 459 if ctxt.DynlinkingGo() || ldr.SymType(rs) == sym.SDYNIMPORT { 460 if immrot(uint32(offset)) == 0 { 461 ctxt.Errorf(s, "odd offset in dynlink direct call: %v+%d", ldr.SymName(rs), offset) 462 } 463 gentrampdyn(ctxt.Arch, trampb, rs, int64(offset)) 464 } else if ctxt.BuildMode == ld.BuildModeCArchive || ctxt.BuildMode == ld.BuildModeCShared || ctxt.BuildMode == ld.BuildModePIE { 465 gentramppic(ctxt.Arch, trampb, rs, int64(offset)) 466 } else { 467 gentramp(ctxt.Arch, ctxt.LinkMode, ldr, trampb, rs, int64(offset)) 468 } 469 } 470 // modify reloc to point to tramp, which will be resolved later 471 sb := ldr.MakeSymbolUpdater(s) 472 relocs := sb.Relocs() 473 r := relocs.At(ri) 474 r.SetSym(tramp) 475 r.SetAdd(r.Add()&0xff000000 | 0xfffffe) // clear the offset embedded in the instruction 476 } 477 default: 478 ctxt.Errorf(s, "trampoline called with non-jump reloc: %d (%s)", r.Type(), sym.RelocName(ctxt.Arch, r.Type())) 479 } 480} 481 482// generate a trampoline to target+offset. 483func gentramp(arch *sys.Arch, linkmode ld.LinkMode, ldr *loader.Loader, tramp *loader.SymbolBuilder, target loader.Sym, offset int64) { 484 tramp.SetSize(12) // 3 instructions 485 P := make([]byte, tramp.Size()) 486 t := ldr.SymValue(target) + offset 487 o1 := uint32(0xe5900000 | 12<<12 | 15<<16) // MOVW (R15), R12 // R15 is actual pc + 8 488 o2 := uint32(0xe12fff10 | 12) // JMP (R12) 489 o3 := uint32(t) // WORD $target 490 arch.ByteOrder.PutUint32(P, o1) 491 arch.ByteOrder.PutUint32(P[4:], o2) 492 arch.ByteOrder.PutUint32(P[8:], o3) 493 tramp.SetData(P) 494 495 if linkmode == ld.LinkExternal || ldr.SymValue(target) == 0 { 496 r, _ := tramp.AddRel(objabi.R_ADDR) 497 r.SetOff(8) 498 r.SetSiz(4) 499 r.SetSym(target) 500 r.SetAdd(offset) 501 } 502} 503 504// generate a trampoline to target+offset in position independent code. 505func gentramppic(arch *sys.Arch, tramp *loader.SymbolBuilder, target loader.Sym, offset int64) { 506 tramp.SetSize(16) // 4 instructions 507 P := make([]byte, tramp.Size()) 508 o1 := uint32(0xe5900000 | 12<<12 | 15<<16 | 4) // MOVW 4(R15), R12 // R15 is actual pc + 8 509 o2 := uint32(0xe0800000 | 12<<12 | 15<<16 | 12) // ADD R15, R12, R12 510 o3 := uint32(0xe12fff10 | 12) // JMP (R12) 511 o4 := uint32(0) // WORD $(target-pc) // filled in with relocation 512 arch.ByteOrder.PutUint32(P, o1) 513 arch.ByteOrder.PutUint32(P[4:], o2) 514 arch.ByteOrder.PutUint32(P[8:], o3) 515 arch.ByteOrder.PutUint32(P[12:], o4) 516 tramp.SetData(P) 517 518 r, _ := tramp.AddRel(objabi.R_PCREL) 519 r.SetOff(12) 520 r.SetSiz(4) 521 r.SetSym(target) 522 r.SetAdd(offset + 4) 523} 524 525// generate a trampoline to target+offset in dynlink mode (using GOT). 526func gentrampdyn(arch *sys.Arch, tramp *loader.SymbolBuilder, target loader.Sym, offset int64) { 527 tramp.SetSize(20) // 5 instructions 528 o1 := uint32(0xe5900000 | 12<<12 | 15<<16 | 8) // MOVW 8(R15), R12 // R15 is actual pc + 8 529 o2 := uint32(0xe0800000 | 12<<12 | 15<<16 | 12) // ADD R15, R12, R12 530 o3 := uint32(0xe5900000 | 12<<12 | 12<<16) // MOVW (R12), R12 531 o4 := uint32(0xe12fff10 | 12) // JMP (R12) 532 o5 := uint32(0) // WORD $target@GOT // filled in with relocation 533 o6 := uint32(0) 534 if offset != 0 { 535 // insert an instruction to add offset 536 tramp.SetSize(24) // 6 instructions 537 o6 = o5 538 o5 = o4 539 o4 = 0xe2800000 | 12<<12 | 12<<16 | immrot(uint32(offset)) // ADD $offset, R12, R12 540 o1 = uint32(0xe5900000 | 12<<12 | 15<<16 | 12) // MOVW 12(R15), R12 541 } 542 P := make([]byte, tramp.Size()) 543 arch.ByteOrder.PutUint32(P, o1) 544 arch.ByteOrder.PutUint32(P[4:], o2) 545 arch.ByteOrder.PutUint32(P[8:], o3) 546 arch.ByteOrder.PutUint32(P[12:], o4) 547 arch.ByteOrder.PutUint32(P[16:], o5) 548 if offset != 0 { 549 arch.ByteOrder.PutUint32(P[20:], o6) 550 } 551 tramp.SetData(P) 552 553 r, _ := tramp.AddRel(objabi.R_GOTPCREL) 554 r.SetOff(16) 555 r.SetSiz(4) 556 r.SetSym(target) 557 r.SetAdd(8) 558 if offset != 0 { 559 // increase reloc offset by 4 as we inserted an ADD instruction 560 r.SetOff(20) 561 r.SetAdd(12) 562 } 563} 564 565func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loader.Reloc, s loader.Sym, val int64) (o int64, nExtReloc int, ok bool) { 566 rs := r.Sym() 567 if target.IsExternal() { 568 switch r.Type() { 569 case objabi.R_CALLARM: 570 // set up addend for eventual relocation via outer symbol. 571 _, off := ld.FoldSubSymbolOffset(ldr, rs) 572 xadd := int64(signext24(r.Add()&0xffffff))*4 + off 573 if xadd/4 > 0x7fffff || xadd/4 < -0x800000 { 574 ldr.Errorf(s, "direct call too far %d", xadd/4) 575 } 576 return int64(braddoff(int32(0xff000000&uint32(r.Add())), int32(0xffffff&uint32(xadd/4)))), 1, true 577 } 578 return -1, 0, false 579 } 580 581 const isOk = true 582 const noExtReloc = 0 583 switch r.Type() { 584 // The following three arch specific relocations are only for generation of 585 // Linux/ARM ELF's PLT entry (3 assembler instruction) 586 case objabi.R_PLT0: // add ip, pc, #0xXX00000 587 if ldr.SymValue(syms.GOTPLT) < ldr.SymValue(syms.PLT) { 588 ldr.Errorf(s, ".got.plt should be placed after .plt section.") 589 } 590 return 0xe28fc600 + (0xff & (int64(uint32(ldr.SymValue(rs)-(ldr.SymValue(syms.PLT)+int64(r.Off()))+r.Add())) >> 20)), noExtReloc, isOk 591 case objabi.R_PLT1: // add ip, ip, #0xYY000 592 return 0xe28cca00 + (0xff & (int64(uint32(ldr.SymValue(rs)-(ldr.SymValue(syms.PLT)+int64(r.Off()))+r.Add()+4)) >> 12)), noExtReloc, isOk 593 case objabi.R_PLT2: // ldr pc, [ip, #0xZZZ]! 594 return 0xe5bcf000 + (0xfff & int64(uint32(ldr.SymValue(rs)-(ldr.SymValue(syms.PLT)+int64(r.Off()))+r.Add()+8))), noExtReloc, isOk 595 case objabi.R_CALLARM: // bl XXXXXX or b YYYYYY 596 // r.Add is the instruction 597 // low 24-bit encodes the target address 598 t := (ldr.SymValue(rs) + int64(signext24(r.Add()&0xffffff)*4) - (ldr.SymValue(s) + int64(r.Off()))) / 4 599 if t > 0x7fffff || t < -0x800000 { 600 ldr.Errorf(s, "direct call too far: %s %x", ldr.SymName(rs), t) 601 } 602 return int64(braddoff(int32(0xff000000&uint32(r.Add())), int32(0xffffff&t))), noExtReloc, isOk 603 } 604 605 return val, 0, false 606} 607 608func archrelocvariant(*ld.Target, *loader.Loader, loader.Reloc, sym.RelocVariant, loader.Sym, int64, []byte) int64 { 609 log.Fatalf("unexpected relocation variant") 610 return -1 611} 612 613func extreloc(target *ld.Target, ldr *loader.Loader, r loader.Reloc, s loader.Sym) (loader.ExtReloc, bool) { 614 rs := r.Sym() 615 var rr loader.ExtReloc 616 switch r.Type() { 617 case objabi.R_CALLARM: 618 // set up addend for eventual relocation via outer symbol. 619 rs, off := ld.FoldSubSymbolOffset(ldr, rs) 620 rr.Xadd = int64(signext24(r.Add()&0xffffff))*4 + off 621 rst := ldr.SymType(rs) 622 if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil { 623 ldr.Errorf(s, "missing section for %s", ldr.SymName(rs)) 624 } 625 rr.Xsym = rs 626 rr.Type = r.Type() 627 rr.Size = r.Siz() 628 return rr, true 629 } 630 return rr, false 631} 632 633func addpltreloc(ldr *loader.Loader, plt *loader.SymbolBuilder, got *loader.SymbolBuilder, s loader.Sym, typ objabi.RelocType) { 634 r, _ := plt.AddRel(typ) 635 r.SetSym(got.Sym()) 636 r.SetOff(int32(plt.Size())) 637 r.SetSiz(4) 638 r.SetAdd(int64(ldr.SymGot(s)) - 8) 639 640 plt.SetReachable(true) 641 plt.SetSize(plt.Size() + 4) 642 plt.Grow(plt.Size()) 643} 644 645func addpltsym(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) { 646 if ldr.SymPlt(s) >= 0 { 647 return 648 } 649 650 ld.Adddynsym(ldr, target, syms, s) 651 652 if target.IsElf() { 653 plt := ldr.MakeSymbolUpdater(syms.PLT) 654 got := ldr.MakeSymbolUpdater(syms.GOTPLT) 655 rel := ldr.MakeSymbolUpdater(syms.RelPLT) 656 if plt.Size() == 0 { 657 panic("plt is not set up") 658 } 659 660 // .got entry 661 ldr.SetGot(s, int32(got.Size())) 662 663 // In theory, all GOT should point to the first PLT entry, 664 // Linux/ARM's dynamic linker will do that for us, but FreeBSD/ARM's 665 // dynamic linker won't, so we'd better do it ourselves. 666 got.AddAddrPlus(target.Arch, plt.Sym(), 0) 667 668 // .plt entry, this depends on the .got entry 669 ldr.SetPlt(s, int32(plt.Size())) 670 671 addpltreloc(ldr, plt, got, s, objabi.R_PLT0) // add lr, pc, #0xXX00000 672 addpltreloc(ldr, plt, got, s, objabi.R_PLT1) // add lr, lr, #0xYY000 673 addpltreloc(ldr, plt, got, s, objabi.R_PLT2) // ldr pc, [lr, #0xZZZ]! 674 675 // rel 676 rel.AddAddrPlus(target.Arch, got.Sym(), int64(ldr.SymGot(s))) 677 678 rel.AddUint32(target.Arch, elf.R_INFO32(uint32(ldr.SymDynid(s)), uint32(elf.R_ARM_JUMP_SLOT))) 679 } else { 680 ldr.Errorf(s, "addpltsym: unsupported binary format") 681 } 682} 683 684func addgotsyminternal(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym) { 685 if ldr.SymGot(s) >= 0 { 686 return 687 } 688 689 got := ldr.MakeSymbolUpdater(syms.GOT) 690 ldr.SetGot(s, int32(got.Size())) 691 got.AddAddrPlus(target.Arch, s, 0) 692 693 if target.IsElf() { 694 } else { 695 ldr.Errorf(s, "addgotsyminternal: unsupported binary format") 696 } 697} 698