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ARM direct CALL/JMP instruction has 24 bit offset, which can only
encodes jumps within +/-32M. When the target is too far, the top
bits get truncated and the program jumps wild.
This CL detects too-far jumps and automatically insert trampolines,
currently only internal linking on ARM.
It is necessary to make the following changes to the linker:
- Resolve direct jump relocs when assigning addresses to functions.
this allows trampoline insertion without moving all code that
already laid down.
- Lay down packages in dependency order, so that when resolving a
inter-package direct jump reloc, the target address is already
known. Intra-package jumps are assumed never too far.
- a linker flag -debugtramp is added for debugging trampolines:
"-debugtramp=1 -v" prints trampoline debug message
"-debugtramp=2" forces all inter-package jump to use
trampolines (currently ARM only)
"-debugtramp=2 -v" does both
- Some data structures are changed for bookkeeping.
On ARM, pseudo DIV/DIVU/MOD/MODU instructions now clobber R8
(unfortunate). In the standard library there is no ARM assembly
code that uses these instructions, and the compiler no longer emits
them (CL 29390).
all.bash passes with -debugtramp=2, except a disassembly test (this
is unavoidable as we changed the instruction).
TBD: debug info of trampolines?
Fixes #17028.
Change-Id: Idcce347ea7e0af77c4079041a160b2f6e114b474
Reviewed-on: https://go-review.googlesource.com/29397
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
142 lines
4.2 KiB
Go
142 lines
4.2 KiB
Go
// Inferno utils/5l/obj.c
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// https://bitbucket.org/inferno-os/inferno-os/src/default/utils/5l/obj.c
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//
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// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
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// Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
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// Portions Copyright © 1997-1999 Vita Nuova Limited
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// Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
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// Portions Copyright © 2004,2006 Bruce Ellis
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// Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
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// Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
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// Portions Copyright © 2009 The Go Authors. All rights reserved.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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package arm
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import (
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"cmd/internal/obj"
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"cmd/internal/sys"
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"cmd/link/internal/ld"
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"fmt"
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)
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func Init() {
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ld.SysArch = sys.ArchARM
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ld.Thearch.Funcalign = FuncAlign
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ld.Thearch.Maxalign = MaxAlign
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ld.Thearch.Minalign = MinAlign
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ld.Thearch.Dwarfregsp = DWARFREGSP
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ld.Thearch.Dwarfreglr = DWARFREGLR
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ld.Thearch.Adddynrel = adddynrel
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ld.Thearch.Archinit = archinit
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ld.Thearch.Archreloc = archreloc
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ld.Thearch.Archrelocvariant = archrelocvariant
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ld.Thearch.Trampoline = trampoline
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ld.Thearch.Asmb = asmb
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ld.Thearch.Elfreloc1 = elfreloc1
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ld.Thearch.Elfsetupplt = elfsetupplt
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ld.Thearch.Gentext = gentext
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ld.Thearch.Machoreloc1 = machoreloc1
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ld.Thearch.Lput = ld.Lputl
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ld.Thearch.Wput = ld.Wputl
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ld.Thearch.Vput = ld.Vputl
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ld.Thearch.Append16 = ld.Append16l
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ld.Thearch.Append32 = ld.Append32l
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ld.Thearch.Append64 = ld.Append64l
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ld.Thearch.Linuxdynld = "/lib/ld-linux.so.3" // 2 for OABI, 3 for EABI
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ld.Thearch.Freebsddynld = "/usr/libexec/ld-elf.so.1"
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ld.Thearch.Openbsddynld = "/usr/libexec/ld.so"
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ld.Thearch.Netbsddynld = "/libexec/ld.elf_so"
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ld.Thearch.Dragonflydynld = "XXX"
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ld.Thearch.Solarisdynld = "XXX"
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}
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func archinit(ctxt *ld.Link) {
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switch ld.Headtype {
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default:
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ld.Exitf("unknown -H option: %v", ld.Headtype)
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case obj.Hplan9: /* plan 9 */
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ld.HEADR = 32
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if *ld.FlagTextAddr == -1 {
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*ld.FlagTextAddr = 4128
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}
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if *ld.FlagDataAddr == -1 {
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*ld.FlagDataAddr = 0
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}
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if *ld.FlagRound == -1 {
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*ld.FlagRound = 4096
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}
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case obj.Hlinux, /* arm elf */
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obj.Hfreebsd,
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obj.Hnetbsd,
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obj.Hopenbsd:
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*ld.FlagD = false
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// with dynamic linking
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ld.Elfinit(ctxt)
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ld.HEADR = ld.ELFRESERVE
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if *ld.FlagTextAddr == -1 {
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*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
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}
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if *ld.FlagDataAddr == -1 {
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*ld.FlagDataAddr = 0
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}
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if *ld.FlagRound == -1 {
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*ld.FlagRound = 4096
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}
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case obj.Hnacl:
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ld.Elfinit(ctxt)
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ld.HEADR = 0x10000
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ld.Funcalign = 16
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if *ld.FlagTextAddr == -1 {
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*ld.FlagTextAddr = 0x20000
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}
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if *ld.FlagDataAddr == -1 {
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*ld.FlagDataAddr = 0
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}
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if *ld.FlagRound == -1 {
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*ld.FlagRound = 0x10000
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}
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case obj.Hdarwin: /* apple MACH */
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*ld.FlagW = true // disable DWARF generation
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ld.Machoinit()
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ld.HEADR = ld.INITIAL_MACHO_HEADR
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if *ld.FlagTextAddr == -1 {
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*ld.FlagTextAddr = 4096 + int64(ld.HEADR)
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}
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if *ld.FlagDataAddr == -1 {
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*ld.FlagDataAddr = 0
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}
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if *ld.FlagRound == -1 {
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*ld.FlagRound = 4096
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}
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}
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if *ld.FlagDataAddr != 0 && *ld.FlagRound != 0 {
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fmt.Printf("warning: -D0x%x is ignored because of -R0x%x\n", uint64(*ld.FlagDataAddr), uint32(*ld.FlagRound))
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}
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}
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