linux.git/arch/mips/Makefile, branch v4.14.124

MIPS: Always use -march=, not - shortcuts

2018-09-05T07:26:41+00:00

commit 344ebf09949c31bcb8818d8458b65add29f1d67b upstream.

The VDSO Makefile filters CFLAGS to select a subset which it uses whilst
building the VDSO ELF. One of the flags it allows through is the -march=
flag that selects the architecture/ISA to target.

Unfortunately in cases where CONFIG_CPU_MIPS32_R{1,2}=y and the
toolchain defaults to building for MIPS64, the main MIPS Makefile ends
up using the short-form - flags in cflags-y. This is because the
calls to cc-option always fail to use the long-form -march= flag
due to the lack of an -mabi= flag in KBUILD_CFLAGS at the point
where the cc-option function is executed. The resulting GCC invocation
is something like:

  $ mips64-linux-gcc -Werror -march=mips32r2 -c -x c /dev/null -o tmp
  cc1: error: '-march=mips32r2' is not compatible with the selected ABI

These short-form - flags are dropped by the VDSO Makefile's
filtering, and so we attempt to build the VDSO without specifying any
architecture. This results in an attempt to build the VDSO using
whatever the compiler's default architecture is, regardless of whether
that is suitable for the kernel configuration.

One encountered build failure resulting from this mismatch is a
rejection of the sync instruction if the kernel is configured for a
MIPS32 or MIPS64 r1 or r2 target but the toolchain defaults to an older
architecture revision such as MIPS1 which did not include the sync
instruction:

    CC      arch/mips/vdso/gettimeofday.o
  /tmp/ccGQKoOj.s: Assembler messages:
  /tmp/ccGQKoOj.s:273: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:329: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:520: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:714: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1009: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1066: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1114: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1279: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1334: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1374: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1459: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1514: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:1814: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:2002: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  /tmp/ccGQKoOj.s:2066: Error: opcode not supported on this processor: mips1 (mips1) `sync'
  make[2]: *** [scripts/Makefile.build:318: arch/mips/vdso/gettimeofday.o] Error 1
  make[1]: *** [scripts/Makefile.build:558: arch/mips/vdso] Error 2
  make[1]: *** Waiting for unfinished jobs....

This can be reproduced for example by attempting to build
pistachio_defconfig using Arnd's GCC 8.1.0 mips64 toolchain from
kernel.org:

  https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/8.1.0/x86_64-gcc-8.1.0-nolibc-mips64-linux.tar.xz

Resolve this problem by using the long-form -march= in all cases,
which makes it through the arch/mips/vdso/Makefile's filtering & is thus
consistently used to build both the kernel proper & the VDSO.

The use of cc-option to prefer the long-form & fall back to the
short-form flags makes no sense since the short-form is just an
abbreviation for the also-supported long-form in all GCC versions that
we support building with. This means there is no case in which we have
to use the short-form - flags, so we can simply remove them.

The manual redefinition of _MIPS_ISA is removed naturally along with the
use of the short-form flags that it accompanied, and whilst here we
remove the separate assembler ISA selection. I suspect that both of
these were only required due to the mips32 vs mips2 mismatch that was
introduced by commit 59b3e8e9aac6 ("[MIPS] Makefile crapectomy.") and
fixed but not cleaned up by commit 9200c0b2a07c ("[MIPS] Fix Makefile
bugs for MIPS32/MIPS64 R1 and R2.").

I've marked this for backport as far as v4.4 where the MIPS VDSO was
introduced. In earlier kernels there should be no ill effect to using
the short-form flags.

Signed-off-by: Paul Burton 
Cc: Ralf Baechle 
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # v4.4+
Reviewed-by: James Hogan 
Patchwork: https://patchwork.linux-mips.org/patch/19579/
Signed-off-by: Greg Kroah-Hartman

MIPS: Add DWARF unwinding to assembly

2017-09-06T09:01:52+00:00

This will allow kdump dumps to work correclty with MIPS and
future DWARF unwinding of the stack to give accurate tracebacks.

Signed-off-by: Corey Minyard 
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16990/
Signed-off-by: Ralf Baechle

MIPS: Prevent direct use of generic_defconfig

2017-08-29T22:57:28+00:00

Using generic_defconfig directly is unlikely to be what a user actually
wants to do - it doesn't specify any particular ISA revision & it
doesn't enable any board or driver support, resulting in a largely
useless kernel.

Prevent users from using it directly, printing a helpful message to
point them in the right direction if they attempt to.

Signed-off-by: Paul Burton 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16946/
Signed-off-by: Ralf Baechle

MIPS: generic: Allow filtering enabled boards by requirements

2017-08-29T22:57:28+00:00

Up until now when configuring a generic kernel all board config
fragments have been merged by default unless boards are explicitly
selected by the user specifying BOARDS=.

In many cases this is sub-optimal, since some boards don't make sense to
include in some kernels. For example the MIPS SEAD-3 development board
has only ever been used with 32 bit CPUs, so including support for the
SEAD-3 in a 64 bit kernel is wasteful.

This patch introduces support for specifying requirements in board
config fragments, using comments formatted like so:

  # require CONFIG_BLA=y

For example the SEAD-3 board could specify that it should only be merged
for 32 bit kernels using a requirement line like the following:

  # require CONFIG_32BIT=y

A new generic-board-config.sh script is introduced to handle selecting
the board config fragments to merge & calling merge_config.sh to merge
them. In order to allow requirements to check Kconfig symbols that are
implicitly selected, rather than explicitly specified by
generic_defconfig or one of the ISA config fragments, an intermediate
.config file is saved & used as a reference when checking requirements.

Signed-off-by: Paul Burton 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16943/
Signed-off-by: Ralf Baechle

MIPS: Allow platform to specify multiple its.S files

2017-08-29T13:21:52+00:00

In preparation for splitting arch/mips/generic/vmlinux.its.S into
multiple files such that it doesn't become a conflict magnet as boards
are added, allow platforms to specify a list of image tree source files
which will be concatenated to form the final source used to build the
image tree.

Signed-off-by: Paul Burton 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16938/
Signed-off-by: Ralf Baechle

MIPS: Remove unused R6000 support

2017-08-29T13:21:51+00:00

The kernel contains a small amount of incomplete code aimed at
supporting old R6000 CPUs. This is:

  - Unused, as no machine selects CONFIG_SYS_HAS_CPU_R6000.

  - Broken, since there are glaring errors such as r6000_fpu.S moving
    the FCSR register to t1, then ignoring it & instead saving t0 into
    struct sigcontext...

  - A maintenance headache, since it's code that nobody can test which
    nevertheless imposes constraints on code which it shares with other
    machines.

Remove this incomplete & broken R6000 CPU support in order to clean up
and in preparation for changes which will no longer need to consider
dragging the pretense of R6000 support along with them.

Signed-off-by: Paul Burton 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16236/
Signed-off-by: Ralf Baechle

MIPS: Set ISA bit in entry-y for microMIPS kernels

2017-08-08T12:00:50+00:00

When building a kernel for the microMIPS ISA, ensure that the ISA bit
(ie. bit 0) in the entry address is set. Otherwise we may include an
entry address in images which bootloaders will jump to as MIPS32 code.

I originally tried using "objdump -f" to obtain the entry address, which
works for microMIPS but it always outputs a 32 bit address for a 32 bit
ELF whilst nm will sign extend to 64 bit. That matters for systems where
we might want to run a MIPS32 kernel on a MIPS64 CPU & load it with a
MIPS64 bootloader, which would then jump to a non-canonical
(non-sign-extended) address.

This works in all cases as it only changes the behaviour for microMIPS
kernels, but isn't the prettiest solution. A possible alternative would
be to write a custom tool to just extract, sign extend & print the entry
point of an ELF executable. I'm open to feedback if that would be
preferred.

Signed-off-by: Paul Burton 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16950/
Signed-off-by: Ralf Baechle

MIPS: build: Fix "-modd-spreg" switch usage when compiling for mips32r6

2017-06-29T00:42:23+00:00

Add "-modd-spreg" when compiling the kernel for mips32r6 target.

This makes sure the kernel builds properly even with toolchains that
use "-mno-odd-spreg" by default. This is the case with Android gcc.
Prior to this patch, kernel builds using gcc for Android failed with
following error messages, if target architecture is set to mips32r6:

arch/mips/kernel/r4k_switch.S: Assembler messages:
.../r4k_switch.S:210: Error: float register should be even, was 1
.../r4k_switch.S:212: Error: float register should be even, was 3
.../r4k_switch.S:214: Error: float register should be even, was 5
.../r4k_switch.S:216: Error: float register should be even, was 7
.../r4k_switch.S:218: Error: float register should be even, was 9
.../r4k_switch.S:220: Error: float register should be even, was 11
.../r4k_switch.S:222: Error: float register should be even, was 13
.../r4k_switch.S:224: Error: float register should be even, was 15
.../r4k_switch.S:226: Error: float register should be even, was 17
.../r4k_switch.S:228: Error: float register should be even, was 19
.../r4k_switch.S:230: Error: float register should be even, was 21
.../r4k_switch.S:232: Error: float register should be even, was 23
.../r4k_switch.S:234: Error: float register should be even, was 25
.../r4k_switch.S:236: Error: float register should be even, was 27
.../r4k_switch.S:238: Error: float register should be even, was 29
.../r4k_switch.S:240: Error: float register should be even, was 31
make[2]: *** [arch/mips/kernel/r4k_switch.o] Error 1

Signed-off-by: Miodrag Dinic 
Signed-off-by: Goran Ferenc 
Signed-off-by: Aleksandar Markovic 
Cc: James.Hogan@imgtec.com
Cc: Paul.Burton@imgtec.com
Cc: Raghu.Gandham@imgtec.com
Cc: Leonid.Yegoshin@imgtec.com
Cc: Douglas.Leung@imgtec.com
Cc: Petar.Jovanovic@imgtec.com
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16509/
Signed-off-by: Ralf Baechle

MIPS: generic: fix out-of-tree defconfig target builds

2017-04-11T11:17:31+00:00

When specifying a generic defconfig target with O=... option set, make
is invoked in the output location before a target makefile wrapper is
created. Ensure that the correct makefile is used by specifying the
kernel source makefile during make invocation.

This fixes the either of the following errors:

$ make sead3_defoncifg ARCH=mips O=test
make[1]: Entering directory '/mnt/ssd/MIPS/linux-next/test'
make[2]: *** No rule to make target '32r2el_defconfig'.  Stop.
arch/mips/Makefile:506: recipe for target 'sead3_defconfig' failed
make[1]: *** [sead3_defconfig] Error 2
make[1]: Leaving directory '/mnt/ssd/MIPS/linux-next/test'
Makefile:152: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2

$ make 32r2el_defconfig ARCH=mips O=test
make[1]: Entering directory '/mnt/ssd/MIPS/linux-next/test'
Using ../arch/mips/configs/generic_defconfig as base
Merging ../arch/mips/configs/generic/32r2.config
Merging ../arch/mips/configs/generic/el.config
Merging ../arch/mips/configs/generic/board-sead-3.config
!
! merged configuration written to .config (needs make)
!
make[2]: *** No rule to make target 'olddefconfig'.  Stop.
arch/mips/Makefile:489: recipe for target '32r2el_defconfig' failed
make[1]: *** [32r2el_defconfig] Error 2
make[1]: Leaving directory '/mnt/ssd/MIPS/linux-next/test'
Makefile:152: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2

Fixes: eed0eabd12ef ('MIPS: generic: Introduce generic DT-based board support')
Fixes: 3f5f0a4475e1 ('MIPS: generic: Convert SEAD-3 to a generic board')
Signed-off-by: Marcin Nowakowski 
Cc: Paul Burton 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15464/
Signed-off-by: Ralf Baechle

MIPS: Disable stack checks on MIPS kernels

2017-02-14T09:00:23+00:00

Disable stack checking on MIPS kernels.  Some distribution toolchains
might pass the -fstack-check option to gcc.  This results in a
store-doubleword instruction being emitted at the top of all
functions that checks the available stack space.  E.g.,

  a80000000001d740 :
  a80000000001d740:       ffa0bfc0        sd      zero,-16448(sp)
  a80000000001d744:       2405ffc9        li      a1,-55
  a80000000001d748:       67bdffc0        daddiu  sp,sp,-64

Generally, this is undesirable, and especially on the SGI IP27
platform, it will trigger a NULL pointer dereference in
'_raw_spin_lock_irq' during early init.

Signed-off-by: Joshua Kinard 
Suggested-by: James Hogan 
Cc: Ralf Baechle 
Cc: "Maciej W. Rozycki" 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15132/
Signed-off-by: James Hogan