Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull low-level x86 updates from Ingo Molnar:
 "In this cycle this topic tree has become one of those 'super topics'
  that accumulated a lot of changes:

   - Add CONFIG_VMAP_STACK=y support to the core kernel and enable it on
     x86 - preceded by an array of changes. v4.8 saw preparatory changes
     in this area already - this is the rest of the work. Includes the
     thread stack caching performance optimization. (Andy Lutomirski)

   - switch_to() cleanups and all around enhancements. (Brian Gerst)

   - A large number of dumpstack infrastructure enhancements and an
     unwinder abstraction. The secret long term plan is safe(r) live
     patching plus maybe another attempt at debuginfo based unwinding -
     but all these current bits are standalone enhancements in a frame
     pointer based debug environment as well. (Josh Poimboeuf)

   - More __ro_after_init and const annotations. (Kees Cook)

   - Enable KASLR for the vmemmap memory region. (Thomas Garnier)"

[ The virtually mapped stack changes are pretty fundamental, and not
  x86-specific per se, even if they are only used on x86 right now. ]

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  x86/asm: Get rid of __read_cr4_safe()
  thread_info: Use unsigned long for flags
  x86/alternatives: Add stack frame dependency to alternative_call_2()
  x86/dumpstack: Fix show_stack() task pointer regression
  x86/dumpstack: Remove dump_trace() and related callbacks
  x86/dumpstack: Convert show_trace_log_lvl() to use the new unwinder
  oprofile/x86: Convert x86_backtrace() to use the new unwinder
  x86/stacktrace: Convert save_stack_trace_*() to use the new unwinder
  perf/x86: Convert perf_callchain_kernel() to use the new unwinder
  x86/unwind: Add new unwind interface and implementations
  x86/dumpstack: Remove NULL task pointer convention
  fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y
  sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK
  lib/syscall: Pin the task stack in collect_syscall()
  x86/process: Pin the target stack in get_wchan()
  x86/dumpstack: Pin the target stack when dumping it
  kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function
  sched/core: Add try_get_task_stack() and put_task_stack()
  x86/entry/64: Fix a minor comment rebase error
  iommu/amd: Don't put completion-wait semaphore on stack
  ...

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,
@@ -248,7 +248,7 @@ 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,

arch/x86/kernel/apic/apic_noop.c

@@ -108,7 +108,7 @@ 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,

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,

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,

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,
@@ -126,7 +126,7 @@ 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;

arch/x86/kernel/apic/x2apic_cluster.c

@@ -227,7 +227,7 @@ 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,

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,

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -560,7 +560,7 @@ 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,