Bug#841500: gcc-6: Unable to compile upstream kernel with previous .config

[tv.deb...@googlemail.com]

On Mon, 31 Oct 2016 07:19:56 +0100 Klaus Ethgen  wrote:

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Hash: SHA512

Am Do den 27. Okt 2016 um  9:20 schrieb Eric Valette:
> I have reverted to 6.2.0-6 anyway using testing as a source for the gcc
> package. But that will work as long as the "broken for kernel" gcc does not
> enter testing. So please find a way to prevent this compiler entering
> testing until this is resolved.

Too late. It went already to testing as inbetween the severity was set
to normal and now we have the broken package in testing.

Regards
   Klaus
- --
Klaus Ethgen


It is fixed for vanilla kernel.org kernel as of 4.8.11, builds on Sid 
without modification. External modules I could test build fine too 
(including Nvidia via dkms).
Do not apply any previously suggested workarounds on top or the 
resulting kernel will not boot.


Cheers.

Bug#841500: gcc-6: Unable to compile upstream kernel with previous .config

[Klaus Ethgen]

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Hash: SHA512

Am Do den 27. Okt 2016 um  9:20 schrieb Eric Valette:
> I have reverted to 6.2.0-6 anyway using testing as a source for the gcc
> package. But that will work as long as the "broken for kernel" gcc does not
> enter testing. So please find a way to prevent this compiler entering
> testing until this is resolved.

Too late. It went already to testing as inbetween the severity was set
to normal and now we have the broken package in testing.

Had to add the following line to my apt sources:
   deb [check-valid-until=no] 
http://snapshot.debian.org/archive/debian/20161010T164513Z sid main

Regards
   Klaus
- -- 
Klaus Ethgen   http://www.ethgen.ch/
pub  4096R/4E20AF1C 2011-05-16Klaus Ethgen 
Fingerprint: 85D4 CA42 952C 949B 1753  62B3 79D0 B06F 4E20 AF1C
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Bug#841500: gcc-6: Unable to compile upstream kernel with previous .config

[Eric Valette]

On Thu, 27 Oct 2016 01:23:14 -0700 Andres Freund  wrote:

On 2016-10-27 06:25:00 +, Niels Thykier wrote:
> I believe it is possible to compile the kernel with gcc-5.  I hope you
> will consider that an acceptable workaround for you in the interim while
> we solve #841419.

It's quite possible to compile the kernel with a newer gcc as well, you
just need to add the necessary CFLAGs. In my build script I've adjusted
things to:
time make -j8 KCPPFLAGS="-fno-pic -Wno-pointer-sign"
and the kernel compiles and runs normally again.




Thanks.

Does this patch solve also the stack-protector compilation issue? And 
why is -Wno-pointer-sign needed?


Attached is the upstream currently proposed patch (borrowed from LKML). 
WFM !


--eric
--- linux/Makefile~ 2016-10-27 21:59:02.777575151 +0200
+++ linux/Makefile  2016-10-27 22:00:46.014577729 +0200
@@ -615,6 +615,7 @@
 ARCH_CFLAGS :=
 include arch/$(SRCARCH)/Makefile
 
+KBUILD_CFLAGS += $(call cc-option,-fno-pie,)
 KBUILD_CFLAGS  += $(call cc-option,-fno-delete-null-pointer-checks,)
 KBUILD_CFLAGS  += $(call cc-disable-warning,maybe-uninitialized,)
 
--- linux/scripts/gcc-x86_64-has-stack-protector.sh~2016-06-24 
19:18:38.0 +0200
+++ linux/scripts/gcc-x86_64-has-stack-protector.sh 2016-10-27 
22:01:36.685581816 +0200
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-echo "int foo(void) { char X[200]; return 3; }" | $* -S -x c -c -O0 
-mcmodel=kernel -fstack-protector - -o - 2> /dev/null | grep -q "%gs"
+echo "int foo(void) { char X[200]; return 3; }" | $* -S -x c -c -O0 
-mcmodel=kernel -fno-pie -fstack-protector - -o - 2> /dev/null | grep -q "%gs"
 if [ "$?" -eq "0" ] ; then
echo y
 else

Bug#841500: gcc-6: Unable to compile upstream kernel with previous .config

[Andres Freund]

On 2016-10-27 06:25:00 +, Niels Thykier wrote:
> I believe it is possible to compile the kernel with gcc-5.  I hope you
> will consider that an acceptable workaround for you in the interim while
> we solve #841419.

It's quite possible to compile the kernel with a newer gcc as well, you
just need to add the necessary CFLAGs. In my build script I've adjusted
things to:
time make -j8 KCPPFLAGS="-fno-pic -Wno-pointer-sign"
and the kernel compiles and runs normally again.

Bug#841500: gcc-6: Unable to compile upstream kernel with previous .config

[Eric Valette]

On Thu, 27 Oct 2016 06:25:00 + Niels Thykier  wrote:

Control: forcemerge 841438 841500


Hi Eric,

Sorry to hear you ran into issues with gcc-6.

On Fri, 21 Oct 2016 10:40:47 +0200 Eric Valette
 wrote:
> [...]
>
> Entering directory '/usr/src/linux-dell'
>   GEN ./Makefile
> scripts/kconfig/conf  --oldconfig Kconfig
> #
> # configuration written to .config
> #
> [...]
> /usr/src/linux-4.4/scripts/mod/empty.c:1:0: error: code model kernel does not 
support PIC mode

This error suggests that your issue is a duplicate of #841419, which is
that the compiler enables PIE by default (which is basically a variant
of PIC).  I have merged your bug into  #841419 accordingly.

I believe it is possible to compile the kernel with gcc-5.  I hope you
will consider that an acceptable workaround for you in the interim while
we solve #841419.


I have reverted to 6.2.0-6 anyway using testing as a source for the gcc 
package. But that will work as long as the "broken for kernel" gcc does 
not enter testing. So please find a way to prevent this compiler 
entering testing until this is resolved. Downloading from shapshots is 
way more painfull. And I wuld also like to know if various stacprotector 
options are broken for other user space or not because many people use 
this for hardening critical apps. If it is a problem, grave for security 
reason should stay.


Ther are indeed two bugs (stackprotector and pie) to solve. But as 
fixing thsi properly requires upstream fixes, that could have been done 
for long if other distro have already switched, I'm dubious this will be 
fixed anytime soon, especially because the same flaw of bugs have 
already happened for Ubuntu and nothing changed.


-- eric

Bug#841500: gcc-6: Unable to compile upstream kernel with previous .config

[Niels Thykier]

Control: forcemerge 841438 841500


Hi Eric,

Sorry to hear you ran into issues with gcc-6.

On Fri, 21 Oct 2016 10:40:47 +0200 Eric Valette
 wrote:
> [...]
> 
> Entering directory '/usr/src/linux-dell'
>   GEN ./Makefile
> scripts/kconfig/conf  --oldconfig Kconfig
> #
> # configuration written to .config
> #
> [...]
> /usr/src/linux-4.4/scripts/mod/empty.c:1:0: error: code model kernel does not 
> support PIC mode

This error suggests that your issue is a duplicate of #841419, which is
that the compiler enables PIE by default (which is basically a variant
of PIC).  I have merged your bug into  #841419 accordingly.

I believe it is possible to compile the kernel with gcc-5.  I hope you
will consider that an acceptable workaround for you in the interim while
we solve #841419.

Thanks,
~Niels

Bug#841500: gcc-6: Unable to compile upstream kernel with previous .config

[Gianfranco Costamagna]

control: reassign -1 src:linux
control: forcemerge -1 841438

sigh



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Bug#841500: gcc-6: Unable to compile upstream kernel with previous .config

[Eric Valette]

Package: gcc-6
Version: 6.2.0-9
Severity: grave
Justification: renders package unusable

Wanted to patch my upstream kernel for the COW vulenraibilty. Applied
incremental patch, started the rebuild with same .config:


Entering directory '/usr/src/linux-dell'
  GEN ./Makefile
scripts/kconfig/conf  --oldconfig Kconfig
#
# configuration written to .config
#
make[1]: Leaving directory '/usr/src/linux-dell'
make[1]: Entering directory '/usr/src/linux-dell'
arch/x86/Makefile:133: stack-protector enabled but compiler support broken
/usr/src/linux-4.4/Makefile:668: Cannot use CONFIG_CC_STACKPROTECTOR_REGULAR: 
-fstack-protector not supported by compiler
  GEN ./Makefile
scripts/kconfig/conf  --silentoldconfig Kconfig
arch/x86/Makefile:133: stack-protector enabled but compiler support broken
/usr/src/linux-4.4/Makefile:668: Cannot use CONFIG_CC_STACKPROTECTOR_REGULAR: 
-fstack-protector not supported by compiler
  CHK include/config/kernel.release
  GEN ./Makefile
  CHK include/generated/uapi/linux/version.h
  CHK include/generated/utsrelease.h
  CC  scripts/mod/empty.o
/usr/src/linux-4.4/scripts/mod/empty.c:1:0: error: code model kernel does not 
support PIC mode
 /* empty file to figure out endianness / word size */
 
/usr/src/linux-4.4/scripts/Makefile.build:258: recipe for target 
'scripts/mod/empty.o' failed
make[3]: *** [scripts/mod/empty.o] Error 1
/usr/src/linux-4.4/scripts/Makefile.build:403: recipe for target 'scripts/mod' 
failed
make[2]: *** [scripts/mod] Error 2
/usr/src/linux-4.4/Makefile:555: recipe for target 'scripts' failed
make[1]: *** [scripts] Error 2
make[1]: Leaving directory '/usr/src/linux-dell'
Makefile:150: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2



-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 4.4.25 (SMP w/4 CPU cores; PREEMPT)
Locale: LANG=en_US.UTF8, LC_CTYPE=en_US.UTF8 (charmap=UTF-8) (ignored: LC_ALL 
set to en_US.UTF8)
Shell: /bin/sh linked to /bin/bash
Init: systemd (via /run/systemd/system)

Versions of packages gcc-6 depends on:
ii  binutils  2.27-9
ii  cpp-6 6.2.0-9
ii  gcc-6-base6.2.0-9
ii  libc6 2.24-5
ii  libcc1-0  6.2.0-9
ii  libgcc-6-dev  6.2.0-9
ii  libgcc1   1:6.2.0-9
ii  libgmp10  2:6.1.1+dfsg-1
ii  libisl15  0.17.1-1
ii  libmpc3   1.0.3-1
ii  libmpfr4  3.1.5-1
ii  libstdc++66.2.0-9
ii  zlib1g1:1.2.8.dfsg-2+b1

Versions of packages gcc-6 recommends:
ii  libc6-dev  2.24-5

Versions of packages gcc-6 suggests:
pn  gcc-6-doc 
pn  gcc-6-locales 
pn  gcc-6-multilib
pn  libasan3-dbg  
pn  libatomic1-dbg
pn  libcilkrts5-dbg   
pn  libgcc1-dbg   
pn  libgomp1-dbg  
pn  libitm1-dbg   
pn  liblsan0-dbg  
pn  libmpx2-dbg   
pn  libquadmath0-dbg  
pn  libtsan0-dbg  
pn  libubsan0-dbg 

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