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cmd/link: move XCOFF data addresses to an unreachable segment

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This commit move data addresses to 0x200000000 for XCOFF executables.
.data and .bss must always be position-independent on AIX. This
modification allows to detect more easily if they aren't, as segfault
will be triggered.

Change-Id: Ied7a5b72b9f4ff9f870a1626cf07c48110635e62
Reviewed-on: https://go-review.googlesource.com/c/151040
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Clément Chigot 2018-11-23 15:12:04 +01:00 committed by Ian Lance Taylor
parent d924c3336c
commit 9a3c1a1bc8
2 changed files with 19 additions and 20 deletions
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5
src/cmd/link/internal/ld/data.go
View file

@ -2036,6 +2036,11 @@ func (ctxt *Link) address() []*sym.Segment {
}
va = uint64(Rnd(int64(va), int64(*FlagRound)))
if ctxt.HeadType == objabi.Haix {
// Data sections are moved to an unreachable segment
// to ensure that they are position-independent.
va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE)
}
order = append(order, &Segdata)
Segdata.Rwx = 06
Segdata.Vaddr = va

34
src/cmd/link/internal/ld/xcoff.go
View file

@ -17,17 +17,20 @@ import (
// as PE and XCOFF are based on COFF files.
// XCOFF files generated are 64 bits.
// Total amount of space to reserve at the start of the file
// for FileHeader, Auxiliary Header, and Section Headers.
// May waste some.
// Based on 24(fhdr) + 120(ahdr) + 23(max sections number) * 72(scnhdr)
const (
XCOFFHDRRESERVE = FILHSZ_64 + AOUTHSZ_EXEC64 + SCNHSZ_64*23
)
// Total amount of space to reserve at the start of the file
// for File Header, Auxiliary Header, and Section Headers.
// May waste some.
XCOFFHDRRESERVE = FILHSZ_64 + AOUTHSZ_EXEC64 + SCNHSZ_64*23
XCOFFSECTALIGN int64 = 32 // base on dump -o
const (
XCOFFSECTALIGN int64 = 32 // base on dump -o
XCOFFBASE = 0x100000000 // Address on 64 bits must start at this value.
// XCOFF binaries should normally have all its sections position-independent.
// However, this is not yet possible for .text because of some R_ADDR relocations
// inside RODATA symbols.
// .data and .bss are position-independent so their address start inside a unreachable
// segment during execution to force segfault if something is wrong.
XCOFFTEXTBASE = 0x100000000 // Start of text address
XCOFFDATABASE = 0x200000000 // Start of data address
)
// File Header
@ -367,12 +370,6 @@ type xcoffFile struct {
loaderReloc []*xcoffLoaderReloc // Reloc that must be made inside loader
}
// Those values will latter be computed in XcoffInit
var (
XCOFFFILEHDR int
XCOFFSECTHDR int
)
// Var used by XCOFF Generation algorithms
var (
xfile xcoffFile
@ -489,14 +486,11 @@ func (f *xcoffFile) getXCOFFscnum(sect *sym.Section) int16 {
func Xcoffinit(ctxt *Link) {
xfile.dynLibraries = make(map[string]int)
XCOFFFILEHDR = int(Rnd(XCOFFHDRRESERVE, XCOFFSECTALIGN))
XCOFFSECTHDR = int(Rnd(int64(XCOFFFILEHDR), XCOFFSECTALIGN))
HEADR = int32(XCOFFFILEHDR)
HEADR = int32(Rnd(XCOFFHDRRESERVE, XCOFFSECTALIGN))
if *FlagTextAddr != -1 {
Errorf(nil, "-T not available on AIX")
}
*FlagTextAddr = XCOFFBASE + int64(XCOFFSECTHDR)
*FlagTextAddr = XCOFFTEXTBASE + int64(HEADR)
*FlagDataAddr = 0
if *FlagRound != -1 {
Errorf(nil, "-R not available on AIX")