On Tue, May 08, 2018 at 04:25:15PM +0200, Greg KH wrote: > On Tue, May 08, 2018 at 08:34:47AM -0500, Josh Poimboeuf wrote: > > On Tue, May 08, 2018 at 07:51:26AM +0200, Greg KH wrote: > > > On Sun, May 06, 2018 at 11:54:53PM -0500, Josh Poimboeuf wrote: > > > > On Sat, May 05, 2018 at 09:21:12PM +0200, damian wrote: > > > > > Helllo together, > > > > > > > > > > Hello everybody, > > > > > > > > > > is something special to note when kernel build with gcc 8? I receive > > > > > various warnings from the objtool: > > > > > With GCC 7 works all fine. > > > > > > > > > > kernel/cgroup/cgroup.o: warning: objtool: > > > > > parse_cgroup_root_flags()+0x40: sibling call from callable > > > > > instruction with modified stack frame > > > > > kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x2a3: > > > > > sibling call from callable instruction with modified stack frame > > > > > kernel/cgroup/cgroup.o: warning: objtool: > > > > > cgroup_apply_control_enable()+0x20b: sibling call from callable > > > > > instruction with modified stack frame > > > > > kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x296: > > > > > sibling call from callable instruction with modified stack frame > > > > > kernel/cgroup/cgroup.o: warning: objtool: > > > > > cgroup_sk_alloc_disable()+0x10: sibling call from callable > > > > > instruction with modified stack frame > > > > > kernel/cgroup/cgroup.o: warning: objtool: > > > > > parse_cgroup_root_flags.cold.45()+0xa: call without frame pointer > > > > > save/setup > > > > > kernel/cgroup/cgroup.o: warning: objtool: > > > > > cgroup_addrm_files.cold.46()+0x17: call without frame pointer > > > > > save/setup > > > > > kernel/cgroup/cgroup.o: warning: objtool: > > > > > cgroup_apply_control_enable.cold.47()+0x24: call without frame > > > > > pointer save/setup > > > > > kernel/cgroup/cgroup.o: warning: objtool: > > > > > rebind_subsystems.cold.48()+0x10: call without frame pointer > > > > > save/setup > > > > > kernel/cgroup/cgroup.o: warning: objtool: > > > > > cgroup_sk_alloc_disable.cold.49()+0x7: call without frame pointer > > > > > save/setup > > > > > CC kernel/cgroup/stat.o > > > > > CC [M] arch/x86/kvm/../../../virt/kvm/kvm_main.o > > > > > arch/x86/kernel/acpi/boot.o: warning: objtool: > > > > > acpi_register_lapic()+0x10: sibling call from callable instruction > > > > > with modified stack frame > > > > > arch/x86/kernel/acpi/boot.o: warning: objtool: acpi_map_cpu()+0x2c: > > > > > sibling call from callable instruction with modified stack frame > > > > > arch/x86/kernel/acpi/boot.o: warning: objtool: > > > > > acpi_register_lapic.cold.6()+0x7: call without frame pointer > > > > > save/setup > > > > > arch/x86/kernel/acpi/boot.o: warning: objtool: > > > > > acpi_map_cpu.cold.7()+0x7: call without frame pointer save/setup > > > > > > > > Thanks, this is a known issue with GCC 8 that I haven't gotten a chance > > > > to fix yet. They're related to the fact that GCC 8 is splitting out > > > > 'unlikely' code into 'cold' subfunctions in .text.unlikely. > > > > > > > > I've got some old patches that fix it. Now that GCC 8 is out, I'll need > > > > get the patches dusted off and cleaned up for merging. > > > > > > Any pointers to these patches? Archi linux just changed their default > > > compiler to gcc 8 and now I'm seeing this in my local builds :( > > > > I'm still dusting the code off, but this fixes most of the warnings. > > The rest of the code should hopefully be ready soon. > > > > From: Josh Poimboeuf <jpoim...@redhat.com> > > Subject: [PATCH] objtool: Detect GCC 8 cold subfunctions > > > > GCC 8 moves a lot of unlikely code out of line to "cold" subfunctions in > > .text.unlikely. Properly detect the new subfunctions and treat them as > > extensions of the original functions. > > > > This fixes a bunch of warnings like: > > > > kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x33: > > sibling call from callable instruction with modified stack frame > > kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x290: > > sibling call from callable instruction with modified stack frame > > kernel/cgroup/cgroup.o: warning: objtool: > > cgroup_apply_control_enable()+0x25b: sibling call from callable instruction > > with modified stack frame > > kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x325: > > sibling call from callable instruction with modified stack frame > > > > Reported-by: Arnd Bergmann <a...@arndb.de> > > Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> > > --- > > tools/objtool/check.c | 7 ++++--- > > tools/objtool/elf.c | 3 +++ > > tools/objtool/elf.h | 1 + > > 3 files changed, 8 insertions(+), 3 deletions(-) > > <snip> > > Much nicer, thanks for the patch, seems to build things "quieter" now. > For the other warnings, they are "safe" to ignore, right? It's just > objtool checking to see if all is ok, but the result should be fine no > matter what, right?
Yeah, from what I can tell, there's nothing catastrophic in the rest of the warnings. Worst case, the ORC unwinder might get confused in a few places. -- Josh
