Build of 5.4-rc8 - Objtool: Unreachable Instruction Warnings

From: Alan Bartlett
Date: Wed Nov 20 2019 - 10:15:12 EST

[Please CC me, as I am not subscribed to the list.]

A build of linux-5.4-rc8 (on RHEL8.1, using gcc (GCC) 8.3.1 20190507
(Red Hat 8.3.1-4)) shows a number of objtool unreachable instruction

arch/x86/kernel/cpu/mce/core.o: warning: objtool: mce_panic()+0x10f:
unreachable instruction
net/core/skbuff.o: warning: objtool: skb_push.cold.95()+0x14:
unreachable instruction
kernel/exit.o: warning: objtool: __x64_sys_exit_group()+0x14:
unreachable instruction
fs/btrfs/extent_io.o: warning: objtool:
__set_extent_bit.cold.61()+0xd: unreachable instruction
fs/btrfs/relocation.o: warning: objtool:
add_tree_block.isra.43.cold.54()+0xc: unreachable instruction
drivers/message/fusion/mptbase.o: warning: objtool:
mpt_HardResetHandler()+0x1ec: unreachable instruction
drivers/gpu/drm/ttm/ttm_bo.o: warning: objtool:
ttm_bo_del_from_lru()+0xe8: unreachable instruction
drivers/scsi/aic7xxx/aic79xx_core.o: warning: objtool:
ahd_handle_seqint.isra.49()+0x6ea: unreachable instruction

I am currently unable to perform a bisection but can provide a little
more context around those warnings, if it would be of help.