On Tue, 2020-02-25 at 12:55 -0500, Arvind Sankar wrote: > On Wed, Feb 05, 2020 at 02:39:44PM -0800, Kristen Carlson Accardi > wrote: > > Allow user to select CONFIG_FG_KASLR if dependencies are met. > > Change > > the make file to build with -ffunction-sections if CONFIG_FG_KASLR > > > > Signed-off-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx> > > --- > > Makefile | 4 ++++ > > arch/x86/Kconfig | 13 +++++++++++++ > > 2 files changed, 17 insertions(+) > > > > diff --git a/Makefile b/Makefile > > index c50ef91f6136..41438a921666 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -846,6 +846,10 @@ ifdef CONFIG_LIVEPATCH > > KBUILD_CFLAGS += $(call cc-option, -flive-patching=inline-clone) > > endif > > > > +ifdef CONFIG_FG_KASLR > > +KBUILD_CFLAGS += -ffunction-sections > > +endif > > + > > With -ffunction-sections I get a few unreachable code warnings from > objtool. > > arch/x86/kernel/dumpstack.o: warning: objtool: show_iret_regs()+0x10: > unreachable instruction > fs/sysfs/dir.o: warning: objtool: sysfs_create_mount_point()+0x4f: > unreachable instruction > kernel/time/clocksource.o: warning: objtool: > __clocksource_register_scale()+0x21: unreachable instruction > drivers/tty/sysrq.o: warning: objtool: sysrq_filter()+0x2ef: > unreachable instruction > arch/x86/mm/fault.o: warning: objtool: pgtable_bad()+0x3f: > unreachable instruction > drivers/acpi/pci_root.o: warning: objtool: > acpi_pci_osc_control_set()+0x123: unreachable instruction > drivers/rtc/class.o: warning: objtool: > devm_rtc_device_register()+0x40: unreachable instruction > kernel/power/process.o: warning: objtool: > freeze_processes.cold()+0x0: unreachable instruction > drivers/pnp/quirks.o: warning: objtool: quirk_awe32_resources()+0x42: > unreachable instruction > drivers/acpi/utils.o: warning: objtool: acpi_evaluate_dsm()+0xf1: > unreachable instruction > kernel/reboot.o: warning: objtool: __do_sys_reboot()+0x1b6: > unreachable instruction > kernel/power/swap.o: warning: objtool: swsusp_read()+0x185: > unreachable instruction > drivers/hid/hid-core.o: warning: objtool: hid_hw_start()+0x38: > unreachable instruction > drivers/acpi/battery.o: warning: objtool: > sysfs_add_battery.cold()+0x1a: unreachable instruction > arch/x86/kernel/cpu/mce/core.o: warning: objtool: > do_machine_check.cold()+0x33: unreachable instruction > drivers/pcmcia/cistpl.o: warning: objtool: pccard_store_cis()+0x4e: > unreachable instruction > drivers/gpu/vga/vgaarb.o: warning: objtool: pci_notify()+0x35: > unreachable instruction > arch/x86/kernel/tsc.o: warning: objtool: > determine_cpu_tsc_frequencies()+0x45: unreachable instruction > drivers/pcmcia/yenta_socket.o: warning: objtool: > ti1250_override()+0x50: unreachable instruction > fs/proc/proc_sysctl.o: warning: objtool: > sysctl_print_dir.isra.0()+0x19: unreachable instruction > drivers/iommu/intel-iommu.o: warning: objtool: > intel_iommu_init()+0x4f4: unreachable instruction > net/mac80211/ibss.o: warning: objtool: > ieee80211_ibss_work.cold()+0x157: unreachable instruction > drivers/net/ethernet/intel/e1000/e1000_main.o: warning: objtool: > e1000_clean.cold()+0x0: unreachable instruction > net/core/skbuff.o: warning: objtool: skb_dump.cold()+0x3fd: > unreachable instruction I'm still working on a solution, but the issue here is that any .cold function is going to be in a different section than the related function, and when objtool is searching for instructions in find_insn(), it assumes that it must be in the same section as the caller.
