How to avoid 'invalid command' error when building Linux kernel on Fedora 28? - linux

Question

I'm building a Linux kernel on Fedora 28, but always run into the same error such as:
CC init/main.o
init/main.o: warning: objtool: elf_begin: invalid command
make[1]: *** [scripts/Makefile.build:277: init/main.o] Error 1
make[1]: *** Deleting file 'init/main.o'
make: *** [Makefile:1067: init] Error 2
make: *** Waiting for unfinished jobs....
I tried "linux-5.0.16.tar.gz" and "linux-5.0.21.tar.gz" downloaded from kernel.org
, and also tried to follow the instruction on Fedora wiki
But there is no way to avoid this 'invalid command' error. "elfutils-libelf-devel" and "elfutils-libelf" are installed. In the fedora way, 'fedpkg cone -a kernel' was successful, so all dependences are installed. Does anyone know what is missing?
Further progress:
The same procedure works on a different machine installed with Fedora 30.
However, after upgrading the original machine to Fedora 30, the error persists.

Answer 1

The machine with the 'invalid command' problem had an old version of libelf.so installed under /user/local. After removing the old libelf, objtool is linked to the current libelf library, and is able to run during compilation of the linux kernel.
A comment is found in the linux source code /tools/perf/util/symbols.h:
/*
* libelf 0.8.x and earlier do not support ELF_C_READ_MMAP;
* for newer versions we can use mmap to reduce memory usage:
*/
This comment led me to look for an out-dated version of libelf.