On Wed, Feb 14, 2018 at 04:24:12PM -0600, Josh Poimboeuf wrote:
> On Wed, Feb 14, 2018 at 04:11:15PM +0100, Arnd Bergmann wrote:
> > Hi Josh,
> >
> > I recently did some randconfig testing with a plain 4.14-stable kernel
> > and gcc-7.3.0, and came across three distinct objtool warnings:
> >
> > drivers/misc/lkdtm_bugs.o: warning: objtool:
> > lkdtm_CORRUPT_LIST_ADD()+0x15: return with modified stack frame
While this is probably an objtool bug, the code is very odd:
00000000000001a8 <lkdtm_CORRUPT_LIST_ADD>:
1a8: e8 00 00 00 00 callq 1ad <lkdtm_CORRUPT_LIST_ADD+0x5>
1a9: R_X86_64_PC32 __fentry__-0x4
1ad: 55 push %rbp
1ae: 48 89 e5 mov %rsp,%rbp
1b1: 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1b5: 48 83 ec 20 sub $0x20,%rsp
1b9: 48 89 ec mov %rbp,%rsp
1bc: 5d pop %rbp
1bd: c3 retq
The function just allocates/aligns its stack space and then returns. It
seems like GCC was too smart for its own good here, as the function
doesn't test what it's supposed to. Can you share the config for this
one?
> > crypto/asymmetric_keys/x509_cert_parser.o: warning: objtool:
> > x509_note_pkey_algo()+0xa4: sibling call from callable instruction
> > with modified stack frame
>From a quick glance, this looks like yet another switch statement
detection issue. I'll need to dig into it more (unless PeterZ, my shiny
new co-maintainer, wants to take a look!)
--
Josh