Re: [PATCH] x86: apply more __ro_after_init and const

From: Kees Cook
Date: Thu Sep 08 2016 - 18:18:17 EST

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Hi,

Friendly reminder -- can this please get added to -tip?

Thanks!

-Kees

On Mon, Aug 8, 2016 at 4:29 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> Guided by grsecurity's analogous __read_only markings in arch/x86,
> this applies several uses of __ro_after_init to structures that are
> only updated during __init, and const for some structures that are
> never updated. Additionally extends __init markings to some functions
> that are only used during __init, and cleans up some missing C99 style
> static initializers.
>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> This has been living in linux-next via the KSPP tree, but I think this
> should likely land via the x86 tree instead. I've sent a corresponding
> patch to ARM as well. If this could get into v4.8, that'd be nice. :)
> ---
> arch/x86/include/asm/desc.h | 2 +-
> arch/x86/include/asm/fpu/xstate.h | 3 ++-
> arch/x86/kernel/apic/apic_flat_64.c | 6 +++---
> arch/x86/kernel/apic/apic_noop.c | 2 +-
> arch/x86/kernel/apic/bigsmp_32.c | 2 +-
> arch/x86/kernel/apic/msi.c | 2 +-
> arch/x86/kernel/apic/probe_32.c | 4 ++--
> arch/x86/kernel/apic/x2apic_cluster.c | 2 +-
> arch/x86/kernel/apic/x2apic_phys.c | 2 +-
> arch/x86/kernel/apic/x2apic_uv_x.c | 2 +-
> arch/x86/kernel/cpu/common.c | 11 ++++++++---
> arch/x86/kernel/cpu/mtrr/main.c | 4 ++--
> arch/x86/kernel/cpu/mtrr/mtrr.h | 2 +-
> arch/x86/kernel/ksysfs.c | 2 +-
> arch/x86/kernel/kvmclock.c | 2 +-
> arch/x86/kernel/paravirt.c | 2 +-
> arch/x86/kernel/ptrace.c | 6 +++---
> arch/x86/kernel/reboot.c | 2 +-
> arch/x86/kernel/setup.c | 4 ++--
> arch/x86/kernel/setup_percpu.c | 2 +-
> arch/x86/kernel/x86_init.c | 6 +++---
> arch/x86/kvm/svm.c | 2 +-
> arch/x86/kvm/vmx.c | 2 +-
> arch/x86/pci/pcbios.c | 7 +++++--
> 24 files changed, 45 insertions(+), 36 deletions(-)
>
> diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
> index 4e10d73cf018..12080d87da3b 100644
> --- a/arch/x86/include/asm/desc.h
> +++ b/arch/x86/include/asm/desc.h
> @@ -36,7 +36,7 @@ static inline void fill_ldt(struct desc_struct *desc, const struct user_desc *in
>
> extern struct desc_ptr idt_descr;
> extern gate_desc idt_table[];
> -extern struct desc_ptr debug_idt_descr;
> +extern const struct desc_ptr debug_idt_descr;
> extern gate_desc debug_idt_table[];
>
> struct gdt_page {
> diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
> index 38951b0fcc5a..9c1a4ceddacb 100644
> --- a/arch/x86/include/asm/fpu/xstate.h
> +++ b/arch/x86/include/asm/fpu/xstate.h
> @@ -43,7 +43,8 @@ extern unsigned int xstate_size;
> extern u64 xfeatures_mask;
> extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
>
> -extern void update_regset_xstate_info(unsigned int size, u64 xstate_mask);
> +extern void __init update_regset_xstate_info(unsigned int size,
> + u64 xstate_mask);
>
> void fpu__xstate_clear_all_cpu_caps(void);
> void *get_xsave_addr(struct xregs_state *xsave, int xstate);
> diff --git a/arch/x86/kernel/apic/apic_flat_64.c b/arch/x86/kernel/apic/apic_flat_64.c
> index 76f89e2b245a..1d0a8bac17be 100644
> --- a/arch/x86/kernel/apic/apic_flat_64.c
> +++ b/arch/x86/kernel/apic/apic_flat_64.c
> @@ -25,7 +25,7 @@
> static struct apic apic_physflat;
> static struct apic apic_flat;
>
> -struct apic __read_mostly *apic = &apic_flat;
> +struct apic *apic __ro_after_init = &apic_flat;
> EXPORT_SYMBOL_GPL(apic);
>
> static int flat_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
> @@ -154,7 +154,7 @@ static int flat_probe(void)
> return 1;
> }
>
> -static struct apic apic_flat = {
> +static struct apic apic_flat __ro_after_init = {
> .name = "flat",
> .probe = flat_probe,
> .acpi_madt_oem_check = flat_acpi_madt_oem_check,
> @@ -249,7 +249,7 @@ static int physflat_probe(void)
> return 0;
> }
>
> -static struct apic apic_physflat = {
> +static struct apic apic_physflat __ro_after_init = {
>
> .name = "physical flat",
> .probe = physflat_probe,
> diff --git a/arch/x86/kernel/apic/apic_noop.c b/arch/x86/kernel/apic/apic_noop.c
> index 13d19ed58514..8a6ce344fe9c 100644
> --- a/arch/x86/kernel/apic/apic_noop.c
> +++ b/arch/x86/kernel/apic/apic_noop.c
> @@ -109,7 +109,7 @@ static void noop_apic_write(u32 reg, u32 v)
> WARN_ON_ONCE(boot_cpu_has(X86_FEATURE_APIC) && !disable_apic);
> }
>
> -struct apic apic_noop = {
> +struct apic apic_noop __ro_after_init = {
> .name = "noop",
> .probe = noop_probe,
> .acpi_madt_oem_check = NULL,
> diff --git a/arch/x86/kernel/apic/bigsmp_32.c b/arch/x86/kernel/apic/bigsmp_32.c
> index cf9bd896c12d..9618dbd63361 100644
> --- a/arch/x86/kernel/apic/bigsmp_32.c
> +++ b/arch/x86/kernel/apic/bigsmp_32.c
> @@ -142,7 +142,7 @@ static int probe_bigsmp(void)
> return dmi_bigsmp;
> }
>
> -static struct apic apic_bigsmp = {
> +static struct apic apic_bigsmp __ro_after_init = {
>
> .name = "bigsmp",
> .probe = probe_bigsmp,
> diff --git a/arch/x86/kernel/apic/msi.c b/arch/x86/kernel/apic/msi.c
> index ade25320df96..015bbf30e3e3 100644
> --- a/arch/x86/kernel/apic/msi.c
> +++ b/arch/x86/kernel/apic/msi.c
> @@ -269,7 +269,7 @@ static void hpet_msi_write_msg(struct irq_data *data, struct msi_msg *msg)
> hpet_msi_write(irq_data_get_irq_handler_data(data), msg);
> }
>
> -static struct irq_chip hpet_msi_controller = {
> +static struct irq_chip hpet_msi_controller __ro_after_init = {
> .name = "HPET-MSI",
> .irq_unmask = hpet_msi_unmask,
> .irq_mask = hpet_msi_mask,
> diff --git a/arch/x86/kernel/apic/probe_32.c b/arch/x86/kernel/apic/probe_32.c
> index f316e34abb42..b04eeec2950c 100644
> --- a/arch/x86/kernel/apic/probe_32.c
> +++ b/arch/x86/kernel/apic/probe_32.c
> @@ -72,7 +72,7 @@ static int probe_default(void)
> return 1;
> }
>
> -static struct apic apic_default = {
> +static struct apic apic_default __ro_after_init = {
>
> .name = "default",
> .probe = probe_default,
> @@ -127,7 +127,7 @@ static struct apic apic_default = {
>
> apic_driver(apic_default);
>
> -struct apic *apic = &apic_default;
> +struct apic *apic __ro_after_init = &apic_default;
> EXPORT_SYMBOL_GPL(apic);
>
> static int cmdline_apic __initdata;
> diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
> index aca8b75c1552..fcaa27ee7b52 100644
> --- a/arch/x86/kernel/apic/x2apic_cluster.c
> +++ b/arch/x86/kernel/apic/x2apic_cluster.c
> @@ -242,7 +242,7 @@ static void cluster_vector_allocation_domain(int cpu, struct cpumask *retmask,
> cpumask_and(retmask, mask, per_cpu(cpus_in_cluster, cpu));
> }
>
> -static struct apic apic_x2apic_cluster = {
> +static struct apic apic_x2apic_cluster __ro_after_init = {
>
> .name = "cluster x2apic",
> .probe = x2apic_cluster_probe,
> diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c
> index a1242e2c12e6..108e6307a076 100644
> --- a/arch/x86/kernel/apic/x2apic_phys.c
> +++ b/arch/x86/kernel/apic/x2apic_phys.c
> @@ -98,7 +98,7 @@ static int x2apic_phys_probe(void)
> return apic == &apic_x2apic_phys;
> }
>
> -static struct apic apic_x2apic_phys = {
> +static struct apic apic_x2apic_phys __ro_after_init = {
>
> .name = "physical x2apic",
> .probe = x2apic_phys_probe,
> diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
> index 29003154fafd..831e1cea3917 100644
> --- a/arch/x86/kernel/apic/x2apic_uv_x.c
> +++ b/arch/x86/kernel/apic/x2apic_uv_x.c
> @@ -554,7 +554,7 @@ static int uv_probe(void)
> return apic == &apic_x2apic_uv_x;
> }
>
> -static struct apic __refdata apic_x2apic_uv_x = {
> +static struct apic apic_x2apic_uv_x __ro_after_init = {
>
> .name = "UV large system",
> .probe = uv_probe,
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index 0fe6953f421c..d8f84250f139 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -1265,9 +1265,14 @@ static __init int setup_disablecpuid(char *arg)
> __setup("clearcpuid=", setup_disablecpuid);
>
> #ifdef CONFIG_X86_64
> -struct desc_ptr idt_descr = { NR_VECTORS * 16 - 1, (unsigned long) idt_table };
> -struct desc_ptr debug_idt_descr = { NR_VECTORS * 16 - 1,
> - (unsigned long) debug_idt_table };
> +struct desc_ptr idt_descr __ro_after_init = {
> + .size = NR_VECTORS * 16 - 1,
> + .address = (unsigned long) idt_table,
> +};
> +const struct desc_ptr debug_idt_descr = {
> + .size = NR_VECTORS * 16 - 1,
> + .address = (unsigned long) debug_idt_table,
> +};
>
> DEFINE_PER_CPU_FIRST(union irq_stack_union,
> irq_stack_union) __aligned(PAGE_SIZE) __visible;
> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> index 7d393ecdeee6..5c367d9cde87 100644
> --- a/arch/x86/kernel/cpu/mtrr/main.c
> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> @@ -72,14 +72,14 @@ static DEFINE_MUTEX(mtrr_mutex);
> u64 size_or_mask, size_and_mask;
> static bool mtrr_aps_delayed_init;
>
> -static const struct mtrr_ops *mtrr_ops[X86_VENDOR_NUM];
> +static const struct mtrr_ops *mtrr_ops[X86_VENDOR_NUM] __ro_after_init;
>
> const struct mtrr_ops *mtrr_if;
>
> static void set_mtrr(unsigned int reg, unsigned long base,
> unsigned long size, mtrr_type type);
>
> -void set_mtrr_ops(const struct mtrr_ops *ops)
> +void __init set_mtrr_ops(const struct mtrr_ops *ops)
> {
> if (ops->vendor && ops->vendor < X86_VENDOR_NUM)
> mtrr_ops[ops->vendor] = ops;
> diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.h b/arch/x86/kernel/cpu/mtrr/mtrr.h
> index 6c7ced07d16d..ad8bd763efa5 100644
> --- a/arch/x86/kernel/cpu/mtrr/mtrr.h
> +++ b/arch/x86/kernel/cpu/mtrr/mtrr.h
> @@ -54,7 +54,7 @@ void fill_mtrr_var_range(unsigned int index,
> bool get_mtrr_state(void);
> void mtrr_bp_pat_init(void);
>
> -extern void set_mtrr_ops(const struct mtrr_ops *ops);
> +extern void __init set_mtrr_ops(const struct mtrr_ops *ops);
>
> extern u64 size_or_mask, size_and_mask;
> extern const struct mtrr_ops *mtrr_if;
> diff --git a/arch/x86/kernel/ksysfs.c b/arch/x86/kernel/ksysfs.c
> index c2bedaea11f7..4afc67f5facc 100644
> --- a/arch/x86/kernel/ksysfs.c
> +++ b/arch/x86/kernel/ksysfs.c
> @@ -184,7 +184,7 @@ out:
>
> static struct kobj_attribute type_attr = __ATTR_RO(type);
>
> -static struct bin_attribute data_attr = {
> +static struct bin_attribute data_attr __ro_after_init = {
> .attr = {
> .name = "data",
> .mode = S_IRUGO,
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> index 1d39bfbd26bb..0964399ef942 100644
> --- a/arch/x86/kernel/kvmclock.c
> +++ b/arch/x86/kernel/kvmclock.c
> @@ -29,7 +29,7 @@
> #include <asm/x86_init.h>
> #include <asm/reboot.h>
>
> -static int kvmclock = 1;
> +static int kvmclock __ro_after_init = 1;
> static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
> static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
> static cycle_t kvm_sched_clock_offset;
> diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
> index 7b3b3f24c3ea..59222a21ef0e 100644
> --- a/arch/x86/kernel/paravirt.c
> +++ b/arch/x86/kernel/paravirt.c
> @@ -388,7 +388,7 @@ NOKPROBE_SYMBOL(native_load_idt);
> #define PTE_IDENT __PV_IS_CALLEE_SAVE(_paravirt_ident_64)
> #endif
>
> -struct pv_mmu_ops pv_mmu_ops = {
> +struct pv_mmu_ops pv_mmu_ops __ro_after_init = {
>
> .read_cr2 = native_read_cr2,
> .write_cr2 = native_write_cr2,
> diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
> index 600edd225e81..acaf2fc7a2ae 100644
> --- a/arch/x86/kernel/ptrace.c
> +++ b/arch/x86/kernel/ptrace.c
> @@ -1247,7 +1247,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
>
> #ifdef CONFIG_X86_64
>
> -static struct user_regset x86_64_regsets[] __read_mostly = {
> +static struct user_regset x86_64_regsets[] __ro_after_init = {
> [REGSET_GENERAL] = {
> .core_note_type = NT_PRSTATUS,
> .n = sizeof(struct user_regs_struct) / sizeof(long),
> @@ -1288,7 +1288,7 @@ static const struct user_regset_view user_x86_64_view = {
> #endif /* CONFIG_X86_64 */
>
> #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
> -static struct user_regset x86_32_regsets[] __read_mostly = {
> +static struct user_regset x86_32_regsets[] __ro_after_init = {
> [REGSET_GENERAL] = {
> .core_note_type = NT_PRSTATUS,
> .n = sizeof(struct user_regs_struct32) / sizeof(u32),
> @@ -1341,7 +1341,7 @@ static const struct user_regset_view user_x86_32_view = {
> */
> u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
>
> -void update_regset_xstate_info(unsigned int size, u64 xstate_mask)
> +void __init update_regset_xstate_info(unsigned int size, u64 xstate_mask)
> {
> #ifdef CONFIG_X86_64
> x86_64_regsets[REGSET_XSTATE].n = size / sizeof(u64);
> diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
> index a9b31eb815f2..fe98493932ad 100644
> --- a/arch/x86/kernel/reboot.c
> +++ b/arch/x86/kernel/reboot.c
> @@ -684,7 +684,7 @@ static void native_machine_power_off(void)
> tboot_shutdown(TB_SHUTDOWN_HALT);
> }
>
> -struct machine_ops machine_ops = {
> +struct machine_ops machine_ops __ro_after_init = {
> .power_off = native_machine_power_off,
> .shutdown = native_machine_shutdown,
> .emergency_restart = native_machine_emergency_restart,
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index c4e7b3991b60..eb2f3b5d9192 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -209,9 +209,9 @@ EXPORT_SYMBOL(boot_cpu_data);
>
>
> #if !defined(CONFIG_X86_PAE) || defined(CONFIG_X86_64)
> -__visible unsigned long mmu_cr4_features;
> +__visible unsigned long mmu_cr4_features __ro_after_init;
> #else
> -__visible unsigned long mmu_cr4_features = X86_CR4_PAE;
> +__visible unsigned long mmu_cr4_features __ro_after_init = X86_CR4_PAE;
> #endif
>
> /* Boot loader ID and version as integers, for the benefit of proc_dointvec */
> diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
> index e4fcb87ba7a6..8ce03678166e 100644
> --- a/arch/x86/kernel/setup_percpu.c
> +++ b/arch/x86/kernel/setup_percpu.c
> @@ -33,7 +33,7 @@ EXPORT_PER_CPU_SYMBOL(cpu_number);
> DEFINE_PER_CPU_READ_MOSTLY(unsigned long, this_cpu_off) = BOOT_PERCPU_OFFSET;
> EXPORT_PER_CPU_SYMBOL(this_cpu_off);
>
> -unsigned long __per_cpu_offset[NR_CPUS] __read_mostly = {
> +unsigned long __per_cpu_offset[NR_CPUS] __ro_after_init = {
> [0 ... NR_CPUS-1] = BOOT_PERCPU_OFFSET,
> };
> EXPORT_SYMBOL(__per_cpu_offset);
> diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
> index dad5fe9633a3..111b838db7fe 100644
> --- a/arch/x86/kernel/x86_init.c
> +++ b/arch/x86/kernel/x86_init.c
> @@ -91,7 +91,7 @@ struct x86_cpuinit_ops x86_cpuinit = {
> static void default_nmi_init(void) { };
> static int default_i8042_detect(void) { return 1; };
>
> -struct x86_platform_ops x86_platform = {
> +struct x86_platform_ops x86_platform __ro_after_init = {
> .calibrate_tsc = native_calibrate_tsc,
> .get_wallclock = mach_get_cmos_time,
> .set_wallclock = mach_set_rtc_mmss,
> @@ -107,7 +107,7 @@ struct x86_platform_ops x86_platform = {
> EXPORT_SYMBOL_GPL(x86_platform);
>
> #if defined(CONFIG_PCI_MSI)
> -struct x86_msi_ops x86_msi = {
> +struct x86_msi_ops x86_msi __ro_after_init = {
> .setup_msi_irqs = native_setup_msi_irqs,
> .teardown_msi_irq = native_teardown_msi_irq,
> .teardown_msi_irqs = default_teardown_msi_irqs,
> @@ -136,7 +136,7 @@ void arch_restore_msi_irqs(struct pci_dev *dev)
> }
> #endif
>
> -struct x86_io_apic_ops x86_io_apic_ops = {
> +struct x86_io_apic_ops x86_io_apic_ops __ro_after_init = {
> .read = native_io_apic_read,
> .disable = native_disable_io_apic,
> };
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 16ef31b87452..9b0d7b98bc51 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -4955,7 +4955,7 @@ static inline void avic_post_state_restore(struct kvm_vcpu *vcpu)
> avic_handle_ldr_update(vcpu);
> }
>
> -static struct kvm_x86_ops svm_x86_ops = {
> +static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
> .cpu_has_kvm_support = has_svm,
> .disabled_by_bios = is_disabled,
> .hardware_setup = svm_hardware_setup,
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 64a79f271276..9faec9dc5476 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -10905,7 +10905,7 @@ out:
> return ret;
> }
>
> -static struct kvm_x86_ops vmx_x86_ops = {
> +static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
> .cpu_has_kvm_support = cpu_has_kvm_support,
> .disabled_by_bios = vmx_disabled_by_bios,
> .hardware_setup = hardware_setup,
> diff --git a/arch/x86/pci/pcbios.c b/arch/x86/pci/pcbios.c
> index 9770e55e768f..1d97cea3b3a4 100644
> --- a/arch/x86/pci/pcbios.c
> +++ b/arch/x86/pci/pcbios.c
> @@ -120,9 +120,12 @@ static unsigned long __init bios32_service(unsigned long service)
> static struct {
> unsigned long address;
> unsigned short segment;
> -} pci_indirect = { 0, __KERNEL_CS };
> +} pci_indirect __ro_after_init = {
> + .address = 0,
> + .segment = __KERNEL_CS,
> +};
>
> -static int pci_bios_present;
> +static int pci_bios_present __ro_after_init;
>
> static int __init check_pcibios(void)
> {
> --
> 2.7.4
>
>
> --
> Kees Cook
> Brillo & Chrome OS Security

--
Kees Cook
Nexus Security

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