Regex fixes for mips and x86 cross-compile

Trying to run the x86 relocs tool on a BSD based HOSTCC (cross compilation environment) leads to errors like

VOFFSET arch/x86/boot/compressed/../voffset.h - due to: vmlinux
CC arch/x86/boot/compressed/misc.o - due to: arch/x86/boot/compressed/../voffset.h
OBJCOPY arch/x86/boot/compressed/vmlinux.bin - due to: vmlinux
RELOCS arch/x86/boot/compressed/vmlinux.relocs - due to: vmlinux
empty (sub)expressionarch/x86/boot/compressed/Makefile:118: recipe for target 'arch/x86/boot/compressed/vmlinux.relocs' failed make[3]: *** [arch/x86/boot/compressed/vmlinux.relocs] Error 1

and when cross compiling a MIPS kernel on a BSD based HOSTCC we get errors like

SYNC include/config/auto.conf.cmd - due to: .config
egrep: empty (sub)expression
UPD include/config/kernel.release
HOSTCC scripts/dtc/dtc.o - due to target missing

It turns out that relocs.c on x86 uses patterns like

	"something(|_end)"

while MIPS uses egrep with

	(|MINOR_|PATCHLEVEL_)

In both cases it is not valid syntax or gives undefined results according to POSIX 9.5.3 ERE Grammar

	https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html

It seems to be silently accepted by the Linux regcmp() or egrep implementation while a BSD host complains.

Such patterns can be replaced by a transformation like

	"(|p1|p2)" -> "(p1|p2)?"

Test Linux:

root@letux:~# echo foo | egrep '^(|foo)$'
foo
root@letux:~# echo fool | egrep '^(foo)?$'
root@letux:~# echo fun | egrep '^(|foo)$'
root@letux:~# echo f | egrep '^(|foo)$'
root@letux:~# echo | egrep '^(|foo)$'

root@letux:~# echo foo | egrep '^(foo)?$'
foo
root@letux:~# echo fool | egrep '^(foo)?$'
root@letux:~# echo fun | egrep '^(foo)?$'
root@letux:~# echo f | egrep '^(foo)?$'
root@letux:~# echo | egrep '^(foo)?$'

root@letux:~#

Test BSD:

iMac:master hns$ echo foo | egrep '^(|foo)$'
egrep: empty (sub)expression
iMac:master hns$ echo fool | egrep '^(foo)?$'
egrep: empty (sub)expression
iMac:master hns$ echo fun | egrep '^(|foo)$'
egrep: empty (sub)expression
iMac:master hns$ echo f | egrep '^(|foo)$'
egrep: empty (sub)expression
iMac:master hns$ echo | egrep '^(|foo)$'
egrep: empty (sub)expression
iMac:master hns$ echo foo | egrep '^(foo)?$'
foo
iMac:master hns$ echo fool | egrep '^(foo)?$'
iMac:master hns$ echo fun | egrep '^(foo)?$'
iMac:master hns$ echo f | egrep '^(foo)?$'
iMac:master hns$ echo | egrep '^(foo)?$'

iMac:master hns$

H. Nikolaus Schaller (2):
x86/tools/relocs: Fix non-POSIX regexp
arch: mips: Fix non-POSIX regexp

 arch/mips/Makefile      | 2 +-
 arch/x86/tools/relocs.c | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

2.31.1