objtool: Teach get_alt_entry() about more relocation types

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2090231



commit 24ff6525
Author: Peter Zijlstra <peterz@infradead.org>
Date:   Thu, 30 Sep 2021 12:43:10 +0200

    objtool: Teach get_alt_entry() about more relocation types

    Occasionally objtool encounters symbol (as opposed to section)
    relocations in .altinstructions. Typically they are the alternatives
    written by elf_add_alternative() as encountered on a noinstr
    validation run on vmlinux after having already ran objtool on the
    individual .o files.

    Basically this is the counterpart of commit 44f6a7c0 ("objtool:
    Fix seg fault with Clang non-section symbols"), because when these new
    assemblers (binutils now also does this) strip the section symbols,
    elf_add_reloc_to_insn() is forced to emit symbol based relocations.

    As such, teach get_alt_entry() about different relocation types.

    Fixes: 9bc0bb50 ("objtool/x86: Rewrite retpoline thunk calls")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
    Link: https://lore.kernel.org/r/YVWUvknIEVNkPvnP@hirez.programming.kicks-ass.net



Signed-off-by: Waiman Long <longman@redhat.com>