* kernel 4.18+ build problem "Recursive variable 'KBUILD_CFLAGS' "
@ 2018-09-23 14:16 Hauke Mehrtens
2018-09-23 20:03 ` Johannes Berg
0 siblings, 1 reply; 6+ messages in thread
From: Hauke Mehrtens @ 2018-09-23 14:16 UTC (permalink / raw)
To: backports
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Hi,
I tried to compile backports against kernel 4.18 and 4.19-rc4 (header
files from Ubuntu) and ran into this problem when it wants to link the
kernel:
LD [M]
/home/hauke/compat-wireless/backports-4.19-rc4-1/drivers/net/wireless/realtek/rtlwifi/rtl_usb.o
Building modules, stage 2.
scripts/Makefile.lib:10: *** Recursive variable 'KBUILD_CFLAGS'
references itself (eventually). Stop.
Makefile:1507: recipe for target 'modules' failed
make[4]: *** [modules] Error 2
Makefile.build:6: recipe for target 'modules' failed
make[3]: *** [modules] Error 2
Makefile.real:88: recipe for target 'modules' failed
make[2]: *** [modules] Error 2
Makefile:40: recipe for target 'modules' failed
make[1]: *** [modules] Error 2
Makefile:30: recipe for target 'default' failed
make: *** [default] Error 2
Did someone also saw this problem?
Hauke
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: kernel 4.18+ build problem "Recursive variable 'KBUILD_CFLAGS' "
2018-09-23 14:16 kernel 4.18+ build problem "Recursive variable 'KBUILD_CFLAGS' " Hauke Mehrtens
@ 2018-09-23 20:03 ` Johannes Berg
2018-09-23 20:09 ` Johannes Berg
0 siblings, 1 reply; 6+ messages in thread
From: Johannes Berg @ 2018-09-23 20:03 UTC (permalink / raw)
To: Hauke Mehrtens, backports
On Sun, 2018-09-23 at 16:16 +0200, Hauke Mehrtens wrote:
> Hi,
>
> I tried to compile backports against kernel 4.18 and 4.19-rc4 (header
> files from Ubuntu) and ran into this problem when it wants to link the
> kernel:
>
> LD [M]
> /home/hauke/compat-wireless/backports-4.19-rc4-1/drivers/net/wireless/realtek/rtlwifi/rtl_usb.o
> Building modules, stage 2.
> scripts/Makefile.lib:10: *** Recursive variable 'KBUILD_CFLAGS'
> references itself (eventually). Stop.
Hmm. I vaguely remember something like that with our driver, but can't
find it now? I also remember trying to fix it in the upstream kernel ...
Ah yes. This patch:
-subdir-ccflags-y = $(call cc-option,...)
+subdir-ccflags-y := $(call cc-option,...)
My commit log said:
In newer kernels, calling cc-option will use KBUILD_CFLAGS,
which itself gets subdir-ccflags-y added to it. Thus, we get
it referencing itself, since nothing here is evaluated until
KBUILD_CFLAGS is used: KBUILD_CFLAGS contains subdir-ccflags-y,
that in turn contains cc-option call, containing KBUILD_CFLAGS.
To avoid that, use := assignment to subdir-ccflags-y. This
causes make to also evaluate += immediately, cc-option calls
are done right away and we don't end up with KBUILD_CFLAGS
referencing itself.
This fixes build of the driver on kernels 4.15 and higher.
Really in our driver - and it was ChromeOS-specific code too - it was +=
but we had to start with := instead of =.
I don't see something like this in rtlwifi though?
Ah, but we have
subdir-ccflags-y += $(call cc-option, -fno-pie) $(call cc-option, -no-pie)
in backports, so I guess this would help:
--- a/backport/Makefile.kernel
+++ b/backport/Makefile.kernel
@@ -30,7 +30,7 @@ NOSTDINC_FLAGS := \
$(CFLAGS)
endif
-subdir-ccflags-y += $(call cc-option, -fno-pie) $(call cc-option, -no-pie)
+subdir-ccflags-y := $(call cc-option, -fno-pie) $(call cc-option, -no-pie)
ifeq ($(CPTCFG_KERNEL_4_3),y)
subdir-ccflags-y += -Wno-pointer-sign
endif
johannes
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* Re: kernel 4.18+ build problem "Recursive variable 'KBUILD_CFLAGS' "
2018-09-23 20:03 ` Johannes Berg
@ 2018-09-23 20:09 ` Johannes Berg
2018-09-23 20:48 ` Hauke Mehrtens
0 siblings, 1 reply; 6+ messages in thread
From: Johannes Berg @ 2018-09-23 20:09 UTC (permalink / raw)
To: Hauke Mehrtens, backports
On Sun, 2018-09-23 at 22:03 +0200, Johannes Berg wrote:
> On Sun, 2018-09-23 at 16:16 +0200, Hauke Mehrtens wrote:
> > Hi,
> >
> > I tried to compile backports against kernel 4.18 and 4.19-rc4 (header
> > files from Ubuntu) and ran into this problem when it wants to link the
> > kernel:
> >
> > LD [M]
> > /home/hauke/compat-wireless/backports-4.19-rc4-1/drivers/net/wireless/realtek/rtlwifi/rtl_usb.o
> > Building modules, stage 2.
> > scripts/Makefile.lib:10: *** Recursive variable 'KBUILD_CFLAGS'
> > references itself (eventually). Stop.
>
> Hmm. I vaguely remember something like that with our driver, but can't
> find it now? I also remember trying to fix it in the upstream kernel ...
Hmm. Well, I can't find any changes from me upstream in this area, so
either I didn't succeed or it didn't get applied. I also can't find a
public record of a patch, so I guess I didn't succeed?
Seems simple enough though, just make cc-option := instead of = in
scripts/Kbuild.include? Or maybe not, dunno.
johannes
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* Re: kernel 4.18+ build problem "Recursive variable 'KBUILD_CFLAGS' "
2018-09-23 20:09 ` Johannes Berg
@ 2018-09-23 20:48 ` Hauke Mehrtens
2018-09-23 20:49 ` Johannes Berg
0 siblings, 1 reply; 6+ messages in thread
From: Hauke Mehrtens @ 2018-09-23 20:48 UTC (permalink / raw)
To: Johannes Berg, backports
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On 09/23/2018 10:09 PM, Johannes Berg wrote:
> On Sun, 2018-09-23 at 22:03 +0200, Johannes Berg wrote:
>> On Sun, 2018-09-23 at 16:16 +0200, Hauke Mehrtens wrote:
>>> Hi,
>>>
>>> I tried to compile backports against kernel 4.18 and 4.19-rc4 (header
>>> files from Ubuntu) and ran into this problem when it wants to link the
>>> kernel:
>>>
>>> LD [M]
>>> /home/hauke/compat-wireless/backports-4.19-rc4-1/drivers/net/wireless/realtek/rtlwifi/rtl_usb.o
>>> Building modules, stage 2.
>>> scripts/Makefile.lib:10: *** Recursive variable 'KBUILD_CFLAGS'
>>> references itself (eventually). Stop.
>>
>> Hmm. I vaguely remember something like that with our driver, but can't
>> find it now? I also remember trying to fix it in the upstream kernel ...
>
> Hmm. Well, I can't find any changes from me upstream in this area, so
> either I didn't succeed or it didn't get applied. I also can't find a
> public record of a patch, so I guess I didn't succeed?
>
> Seems simple enough though, just make cc-option := instead of = in
> scripts/Kbuild.include? Or maybe not, dunno.
>
> johannes
This works for me, will you add a patch?
Hauke
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: kernel 4.18+ build problem "Recursive variable 'KBUILD_CFLAGS' "
2018-09-23 20:48 ` Hauke Mehrtens
@ 2018-09-23 20:49 ` Johannes Berg
2018-09-24 7:18 ` Johannes Berg
0 siblings, 1 reply; 6+ messages in thread
From: Johannes Berg @ 2018-09-23 20:49 UTC (permalink / raw)
To: Hauke Mehrtens, backports
On Sun, 2018-09-23 at 22:48 +0200, Hauke Mehrtens wrote:
>
> > Seems simple enough though, just make cc-option := instead of = in
> > scripts/Kbuild.include? Or maybe not, dunno.
>
> This works for me, will you add a patch?
Sure, I can do that.
johannes
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* Re: kernel 4.18+ build problem "Recursive variable 'KBUILD_CFLAGS' "
2018-09-23 20:49 ` Johannes Berg
@ 2018-09-24 7:18 ` Johannes Berg
0 siblings, 0 replies; 6+ messages in thread
From: Johannes Berg @ 2018-09-24 7:18 UTC (permalink / raw)
To: Hauke Mehrtens, backports
On Sun, 2018-09-23 at 22:49 +0200, Johannes Berg wrote:
> On Sun, 2018-09-23 at 22:48 +0200, Hauke Mehrtens wrote:
> >
> > > Seems simple enough though, just make cc-option := instead of = in
> > > scripts/Kbuild.include? Or maybe not, dunno.
> >
> > This works for me, will you add a patch?
>
> Sure, I can do that.
Done now.
johannes
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end of thread, other threads:[~2018-09-24 13:19 UTC | newest]
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2018-09-23 14:16 kernel 4.18+ build problem "Recursive variable 'KBUILD_CFLAGS' " Hauke Mehrtens
2018-09-23 20:03 ` Johannes Berg
2018-09-23 20:09 ` Johannes Berg
2018-09-23 20:48 ` Hauke Mehrtens
2018-09-23 20:49 ` Johannes Berg
2018-09-24 7:18 ` Johannes Berg
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