Michael Ellerman wrote:
Christophe Leroy <christophe.le...@csgroup.eu> writes:
Le 05/05/2023 à 09:18, Nicholas Piggin a écrit :
This series has the steps to remove ELFv1 from the kernel build.
Patch 1 is a build fix, 2 defaults everything to ELFv2, 3 is
really a separate issue that concerns userspace. 4 removes v1
support.
Super glad to see this!
I see CONFIG_MPROFILE_KERNEL is restricted to LITTLE_ENDIAN. Is that
correct ? Don't we have mprofile_kernel as well on BIG ENDIAN once
switched to ABI v2 ? If so, can we drop the -pg based profiling
completely, or is CLANG still not supporting mprofile_kernel ?
Clang does not support -mprofile-kernel.
AIUI they would like us to switch to -fpatchable-function-entry which
could then be supported on GCC & clang.
That would be a nice cleanup but also a bunch of work that no one has
found time to do.
https://github.com/linuxppc/issues/issues/447
https://github.com/llvm/llvm-project/issues/57031
GCC's support for -fpatchable-function-entry needed fixes for ABIv2,
which have landed in the recent v13.1 release. I am looking into adding
support for that.
So for now we need to keep the -pg based version.
Indeed, but removing elf v1 support does help cleaning up and
simplifying some of the tracing code. Much of the -pg code is already
separate, so it should be easy to drop that once clang picks up support
for -fpatchable-function-entry.
- Naveen
