objtool: Support Clang non-section symbols in ORC generation
When compiling the kernel with AS=clang, objtool produces a lot of warnings: warning: objtool: missing symbol for section .text warning: objtool: missing symbol for section .init.text warning: objtool: missing symbol for section .ref.text It then fails to generate the ORC table. The problem is that objtool assumes text section symbols always exist. But the Clang assembler is aggressive about removing them. When generating relocations for the ORC table, objtool always tries to reference instructions by their section symbol offset. If the section symbol doesn't exist, it bails. Do a fallback: when a section symbol isn't available, reference a function symbol instead. Reported-by:Dmitry Golovin <dima@golovin.in> Signed-off-by:
Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by:
Borislav Petkov <bp@suse.de> Tested-by:
Nathan Chancellor <natechancellor@gmail.com> Reviewed-by:
Miroslav Benes <mbenes@suse.cz> Acked-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://github.com/ClangBuiltLinux/linux/issues/669 Link: https://lkml.kernel.org/r/9a9cae7fcf628843aabe5a086b1a3c5bf50f42e8.1585761021.git.jpoimboe@redhat.com
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