For the record, this is what's causing the config differences between
the gcc versions:
With gcc 10.3.0, CC_HAS_KASAN_GENERIC is not available as it depends on
the following compiler flag:
config CC_HAS_KASAN_GENERIC
def_bool $(cc-option, -fsanitize=kernel-address)
'cc-option' will do something similar to the following, which with gcc
10.2.0 riscv64 cross compiler would return success:
$ /usr/bin/riscv64-linux-gnu-gcc-10 -Werror -fsanitize=kernel-address -c -x c
/dev/null
$ echo $?
0
But with 10.3.0 this doesn't seem to be supported anymore as a
standalone flag, depending now on '-fasan-shadow-offset=':
$ /usr/bin/riscv64-linux-gnu-gcc-10 -Werror -fsanitize=kernel-address -c -x c
/dev/null
cc1: error: ‘-fsanitize=kernel-address’ with stack protection is not supported
without ‘-fasan-shadow-offset=’ for this target [-Werror]
And all KASAN options get removed altogether.
This doesn't cause any real config change, as we disable CONFIG_KASAN
anyway. But for our annotations '-' != 'n', failing the config checks.
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https://bugs.launchpad.net/bugs/1933856
Title:
gcc version used for kernel configs doesn't match the one used for
builds
Status in linux-riscv-5.8 package in Ubuntu:
Invalid
Status in linux-riscv-5.8 source package in Focal:
Fix Committed
Bug description:
[Impact]
linux-riscv-5.8 needs to be built with gcc-10 in Focal otherwise it won't
boot. This was fixed by commit "UBUNTU: [Packaging] Use gcc-10 for riscv 5.8
kernel build", which adds gcc-10 as "Build-Depends-Arch" and sets a variable
"gcc" in 'debian/rules', which is passed down to make by
'debian/rules.d/2-binary-arch.mk'.
The other gcc version dependency is when we generate locally the
kernel configs by running 'make syncconfig', which is called by
'debian/scripts/misc/kernelconfig'. Currently, the syncconfig is
called using the chroot default compiler, which in Focal is gcc-9. So
far there hasn't been any major differences, however with the update
of gcc-10 in Groovy and Focal from 10.2.0 to 10.3.0 some KASAN related
config options are not available anymore, causing some changes on the
configs generated. The problem with non-matching gcc versions being
used, is that there will be a mismatch between the configs being
generated during the preparation of the kernel and the ones during the
build.
[Fix]
The proposed fix is to use the same variable defined for the build, passing
it down to 'debian/scripts/misc/kernelconfig' and using it to define the
correct cross-compiler to be used.
[Where problems could occur]
If the environment variables are not set correctly the build can break in
some environment which was not tested.
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