module: exclude SHN_UNDEF symbols from kallsyms api
Livepatch modules are special in that we preserve their entire symbol tables in order to be able to apply relocations after module load. The unwanted side effect of this is that undefined (SHN_UNDEF) symbols of livepatch modules are accessible via the kallsyms api and this can confuse symbol resolution in livepatch (klp_find_object_symbol()) and cause subtle bugs in livepatch. Have the module kallsyms api skip over SHN_UNDEF symbols. These symbols are usually not available for normal modules anyway as we cut down their symbol tables to just the core (non-undefined) symbols, so this should really just affect livepatch modules. Note that this patch doesn't affect the display of undefined symbols in /proc/kallsyms. Reported-by: NJosh Poimboeuf <jpoimboe@redhat.com> Tested-by: NJosh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: NJosh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: NJessica Yu <jeyu@kernel.org>
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