On Mon, Oct 10, 2016 at 02:56:56PM +0200, Arnd Bergmann wrote: > I have no idea what is actually going on here, but building an x86 kernel > with CONFIG_MATOM results in countless warnings from objtool, such as > > arch/x86/events/intel/ds.o: warning: objtool: intel_pmu_pebs_del()+0x43: call > without frame pointer save/setup > security/keys/keyring.o: warning: objtool: keyring_read()+0x59: call without > frame pointer save/setup > kernel/signal.o: warning: objtool: __dequeue_signal()+0xd8: call without > frame pointer save/setup > kernel/signal.o: warning: objtool: kill_pid()+0x15: call without frame > pointer save/setup > kernel/signal.o: warning: objtool: SyS_signal()+0x27: call without frame > pointer save/setup > mm/page_alloc.o: warning: objtool: zone_watermark_ok_safe()+0x27: call > without frame pointer save/setup > fs/exec.o: warning: objtool: read_code()+0x18: call without frame pointer > save/setup > mm/swap.o: warning: objtool: get_kernel_page()+0x24: call without frame > pointer save/setup > mm/swap.o: warning: objtool: pagevec_move_tail.constprop.25()+0x26: call > without frame pointer save/setup > block/bio.o: warning: objtool: bio_map_kern()+0x47: call without frame > pointer save/setup > arch/x86/crypto/poly1305_glue.o: warning: objtool: poly1305_simd_mult()+0x2d: > call without frame pointer save/setup > crypto/skcipher.o: warning: objtool: skcipher_encrypt_ablkcipher()+0x58: call > without frame pointer save/setup > crypto/skcipher.o: warning: objtool: skcipher_decrypt_ablkcipher()+0x58: call > without frame pointer save/setup > fs/inode.o: warning: objtool: ilookup()+0x5d: call without frame pointer > save/setup > fs/inode.o: warning: objtool: proc_nr_inodes()+0x3e: call without frame > pointer save/setup > fs/namei.o: warning: objtool: lookup_one_len_unlocked()+0x21: call without > frame pointer save/setup > block/elevator.o: warning: objtool: elv_rb_add()+0x5b: call without frame > pointer save/setup > crypto/shash.o: warning: objtool: shash_async_init()+0x1e: call without frame > pointer save/setup > crypto/shash.o: warning: objtool: shash_async_import()+0x1e: call without > frame pointer save/setup > mm/vmscan.o: warning: objtool: pfmemalloc_watermark_ok()+0xb9: call without > frame pointer save/setup > > I have not looked at whether this is a bug in gcc or in objtool, however > I found that not using -mtune=atom reliably avoids the problem. I could > reproduce the problem with gcc versions 4.7 through 6.1.
Thanks for reporting it. It looks like 'mtune=atom' sometimes makes a slight change to one of the stack frame setup instructions. Instead of: move rsp, rbp It sometimes does: lea (%rsp),%rbp They're two different instructions, but they have the same result. It's an easy fix for objtool. I'll post a patch soon. -- Josh
