Messages in this thread | | | Date | Fri, 15 Jan 2021 12:31:26 +0100 (CET) | From | Miroslav Benes <> | Subject | Re: [PATCH] objtool: Don't fail on missing symbol table |
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On Thu, 14 Jan 2021, Josh Poimboeuf wrote:
> Thanks to a recent binutils change which doesn't generate unused > symbols, it's now possible for thunk_64.o be completely empty with > CONFIG_PREEMPTION: no text, no data, no symbols.
"without CONFIG_PREEMPTION", or did I misunderstand?
> We could edit the Makefile to only build that file when > CONFIG_PREEMPTION is enabled, but that will likely create confusion > if/when the thunks end up getting used by some other code again. > > Just ignore it and move on. > > Reported-by: Nathan Chancellor <natechancellor@gmail.com> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
with the note below.
> --- > tools/objtool/elf.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c > index be89c741ba9a..2b0f4f52f7b5 100644 > --- a/tools/objtool/elf.c > +++ b/tools/objtool/elf.c > @@ -380,8 +380,11 @@ static int read_symbols(struct elf *elf) > > symtab = find_section_by_name(elf, ".symtab"); > if (!symtab) { > - WARN("missing symbol table"); > - return -1; > + /* > + * A missing symbol table is actually possible if it's an empty > + * .o file. This can happen for thunk_64.o. > + */ > + return 0; > }
We rely on .symtab presence elsewhere in the code. See elf_create_{rel,rela}_reloc_section(). However, there should never be a problem. If there is a need to create a new reloc section (either for a static call site, or ORC), there should always be a symbol to create it for (or because of it).
Miroslav
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