+Kees
On Wed, Feb 14, 2018 at 04:45:25PM -0600, Josh Poimboeuf wrote:
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?
lkdtm is a "interesting" module in that it tries to do bad things to test for various stuff. Kees, does the above look like it is doing the correct thing?
thanks,
greg k-h