linux_kernel/arch/x86/include/asm/processor.h

#ifndef _ASM_X86_PROCESSOR_H
#define _ASM_X86_PROCESSOR_H

#include <asm/processor-flags.h>

/* Forward declaration, a strange C thing */
struct task_struct;
struct mm_struct;
struct vm86;

#include <asm/math_emu.h>
#include <asm/segment.h>
#include <asm/types.h>
#include <uapi/asm/sigcontext.h>
#include <asm/current.h>
#include <asm/cpufeatures.h>
#include <asm/page.h>
#include <asm/pgtable_types.h>
#include <asm/percpu.h>
#include <asm/msr.h>
#include <asm/desc_defs.h>
#include <asm/nops.h>
#include <asm/special_insns.h>
#include <asm/fpu/types.h>

#include <linux/personality.h>
#include <linux/cache.h>
#include <linux/threads.h>
#include <linux/math64.h>
#include <linux/err.h>
#include <linux/irqflags.h>

/*
 * We handle most unaligned accesses in hardware.  On the other hand
 * unaligned DMA can be quite expensive on some Nehalem processors.
 *
 * Based on this we disable the IP header alignment in network drivers.
 */
#define NET_IP_ALIGN	0

#define HBP_NUM 4
/*
 * Default implementation of macro that returns current
 * instruction pointer ("program counter").
 */
static inline void *current_text_addr(void)
{
	void *pc;

	asm volatile("mov $1f, %0; 1:":"=r" (pc));

	return pc;
}

/*
 * These alignment constraints are for performance in the vSMP case,
 * but in the task_struct case we must also meet hardware imposed
 * alignment requirements of the FPU state:
 */
#ifdef CONFIG_X86_VSMP
# define ARCH_MIN_TASKALIGN		(1 << INTERNODE_CACHE_SHIFT)
# define ARCH_MIN_MMSTRUCT_ALIGN	(1 << INTERNODE_CACHE_SHIFT)
#else
# define ARCH_MIN_TASKALIGN		__alignof__(union fpregs_state)
# define ARCH_MIN_MMSTRUCT_ALIGN	0
#endif

enum tlb_infos {
	ENTRIES,
	NR_INFO
};

extern u16 __read_mostly tlb_lli_4k[NR_INFO];
extern u16 __read_mostly tlb_lli_2m[NR_INFO];
extern u16 __read_mostly tlb_lli_4m[NR_INFO];
extern u16 __read_mostly tlb_lld_4k[NR_INFO];
extern u16 __read_mostly tlb_lld_2m[NR_INFO];
extern u16 __read_mostly tlb_lld_4m[NR_INFO];
extern u16 __read_mostly tlb_lld_1g[NR_INFO];

/*
 *  CPU type and hardware bug flags. Kept separately for each CPU.
 *  Members of this structure are referenced in head.S, so think twice
 *  before touching them. [mj]
 */

struct cpuinfo_x86 {
	__u8			x86;		/* CPU family */
	__u8			x86_vendor;	/* CPU vendor */
	__u8			x86_model;
	__u8			x86_mask;
#ifdef CONFIG_X86_32
	char			wp_works_ok;	/* It doesn't on 386's */

	/* Problems on some 486Dx4's and old 386's: */
	char			rfu;
	char			pad0;
	char			pad1;
#else
	/* Number of 4K pages in DTLB/ITLB combined(in pages): */
	int			x86_tlbsize;
#endif
	__u8			x86_virt_bits;
	__u8			x86_phys_bits;
	/* CPUID returned core id bits: */
	__u8			x86_coreid_bits;
	/* Max extended CPUID function supported: */
	__u32			extended_cpuid_level;
	/* Maximum supported CPUID level, -1=no CPUID: */
	int			cpuid_level;
	__u32			x86_capability[NCAPINTS + NBUGINTS];
	char			x86_vendor_id[16];
	char			x86_model_id[64];
	/* in KB - valid for CPUS which support this call: */
	int			x86_cache_size;
	int			x86_cache_alignment;	/* In bytes */
	/* Cache QoS architectural values: */
	int			x86_cache_max_rmid;	/* max index */
	int			x86_cache_occ_scale;	/* scale to bytes */
	int			x86_power;
	unsigned long		loops_per_jiffy;
	/* cpuid returned max cores value: */
	u16			 x86_max_cores;
	u16			apicid;
	u16			initial_apicid;
	u16			x86_clflush_size;
	/* number of cores as seen by the OS: */
	u16			booted_cores;
	/* Physical processor id: */
	u16			phys_proc_id;
	/* Logical processor id: */
	u16			logical_proc_id;
	/* Core id: */
	u16			cpu_core_id;
	/* Index into per_cpu list: */
	u16			cpu_index;
	u32			microcode;
};

#define X86_VENDOR_INTEL	0
#define X86_VENDOR_CYRIX	1
#define X86_VENDOR_AMD		2
#define X86_VENDOR_UMC		3
#define X86_VENDOR_CENTAUR	5
#define X86_VENDOR_TRANSMETA	7
#define X86_VENDOR_NSC		8
#define X86_VENDOR_NUM		9

#define X86_VENDOR_UNKNOWN	0xff

/*
 * capabilities of CPUs
 */
extern struct cpuinfo_x86	boot_cpu_data;
extern struct cpuinfo_x86	new_cpu_data;

extern struct tss_struct	doublefault_tss;
extern __u32			cpu_caps_cleared[NCAPINTS];
extern __u32			cpu_caps_set[NCAPINTS];

#ifdef CONFIG_SMP
DECLARE_PER_CPU_READ_MOSTLY(struct cpuinfo_x86, cpu_info);
#define cpu_data(cpu)		per_cpu(cpu_info, cpu)
#else
#define cpu_info		boot_cpu_data
#define cpu_data(cpu)		boot_cpu_data
#endif

extern const struct seq_operations cpuinfo_op;

#define cache_line_size()	(boot_cpu_data.x86_cache_alignment)

extern void cpu_detect(struct cpuinfo_x86 *c);

extern void early_cpu_init(void);
extern void identify_boot_cpu(void);
extern void identify_secondary_cpu(struct cpuinfo_x86 *);
extern void print_cpu_info(struct cpuinfo_x86 *);
void print_cpu_msr(struct cpuinfo_x86 *);
extern void init_scattered_cpuid_features(struct cpuinfo_x86 *c);
extern unsigned int init_intel_cacheinfo(struct cpuinfo_x86 *c);
extern void init_amd_cacheinfo(struct cpuinfo_x86 *c);

extern void detect_extended_topology(struct cpuinfo_x86 *c);
extern void detect_ht(struct cpuinfo_x86 *c);

#ifdef CONFIG_X86_32
extern int have_cpuid_p(void);
#else
static inline int have_cpuid_p(void)
{
	return 1;
}
#endif
static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
				unsigned int *ecx, unsigned int *edx)
{
	/* ecx is often an input as well as an output. */
	asm volatile("cpuid"
	    : "=a" (*eax),
	      "=b" (*ebx),
	      "=c" (*ecx),
	      "=d" (*edx)
	    : "0" (*eax), "2" (*ecx)
	    : "memory");
}

static inline void load_cr3(pgd_t *pgdir)
{
	write_cr3(__pa(pgdir));
}

#ifdef CONFIG_X86_32
/* This is the TSS defined by the hardware. */
struct x86_hw_tss {
	unsigned short		back_link, __blh;
	unsigned long		sp0;
	unsigned short		ss0, __ss0h;
	unsigned long		sp1;

	/*
	 * We don't use ring 1, so ss1 is a convenient scratch space in
	 * the same cacheline as sp0.  We use ss1 to cache the value in
	 * MSR_IA32_SYSENTER_CS.  When we context switch
	 * MSR_IA32_SYSENTER_CS, we first check if the new value being
	 * written matches ss1, and, if it's not, then we wrmsr the new
	 * value and update ss1.
	 *
	 * The only reason we context switch MSR_IA32_SYSENTER_CS is
	 * that we set it to zero in vm86 tasks to avoid corrupting the
	 * stack if we were to go through the sysenter path from vm86
	 * mode.
	 */
	unsigned short		ss1;	/* MSR_IA32_SYSENTER_CS */

	unsigned short		__ss1h;
	unsigned long		sp2;
	unsigned short		ss2, __ss2h;
	unsigned long		__cr3;
	unsigned long		ip;
	unsigned long		flags;
	unsigned long		ax;
	unsigned long		cx;
	unsigned long		dx;
	unsigned long		bx;
	unsigned long		sp;
	unsigned long		bp;
	unsigned long		si;
	unsigned long		di;
	unsigned short		es, __esh;
	unsigned short		cs, __csh;
	unsigned short		ss, __ssh;
	unsigned short		ds, __dsh;
	unsigned short		fs, __fsh;
	unsigned short		gs, __gsh;
	unsigned short		ldt, __ldth;
	unsigned short		trace;
	unsigned short		io_bitmap_base;

} __attribute__((packed));
#else
struct x86_hw_tss {
	u32			reserved1;
	u64			sp0;
	u64			sp1;
	u64			sp2;
	u64			reserved2;
	u64			ist[7];
	u32			reserved3;
	u32			reserved4;
	u16			reserved5;
	u16			io_bitmap_base;

} __attribute__((packed)) ____cacheline_aligned;
#endif

/*
 * IO-bitmap sizes:
 */
#define IO_BITMAP_BITS			65536
#define IO_BITMAP_BYTES			(IO_BITMAP_BITS/8)
#define IO_BITMAP_LONGS			(IO_BITMAP_BYTES/sizeof(long))
#define IO_BITMAP_OFFSET		offsetof(struct tss_struct, io_bitmap)
#define INVALID_IO_BITMAP_OFFSET	0x8000

struct tss_struct {
	/*
	 * The hardware state:
	 */
	struct x86_hw_tss	x86_tss;

	/*
	 * The extra 1 is there because the CPU will access an
	 * additional byte beyond the end of the IO permission
	 * bitmap. The extra byte must be all 1 bits, and must
	 * be within the limit.
	 */
	unsigned long		io_bitmap[IO_BITMAP_LONGS + 1];

#ifdef CONFIG_X86_32
	/*
	 * Space for the temporary SYSENTER stack.
	 */
	unsigned long		SYSENTER_stack_canary;
	unsigned long		SYSENTER_stack[64];
#endif

} ____cacheline_aligned;

DECLARE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss);

#ifdef CONFIG_X86_32
DECLARE_PER_CPU(unsigned long, cpu_current_top_of_stack);
#endif

/*
 * Save the original ist values for checking stack pointers during debugging
 */
struct orig_ist {
	unsigned long		ist[7];
};

#ifdef CONFIG_X86_64
DECLARE_PER_CPU(struct orig_ist, orig_ist);

union irq_stack_union {
	char irq_stack[IRQ_STACK_SIZE];
	/*
	 * GCC hardcodes the stack canary as %gs:40.  Since the
	 * irq_stack is the object at %gs:0, we reserve the bottom
	 * 48 bytes of the irq stack for the canary.
	 */
	struct {
		char gs_base[40];
		unsigned long stack_canary;
	};
};

DECLARE_PER_CPU_FIRST(union irq_stack_union, irq_stack_union) __visible;
DECLARE_INIT_PER_CPU(irq_stack_union);

DECLARE_PER_CPU(char *, irq_stack_ptr);
DECLARE_PER_CPU(unsigned int, irq_count);
extern asmlinkage void ignore_sysret(void);
#else	/* X86_64 */
#ifdef CONFIG_CC_STACKPROTECTOR
/*
 * Make sure stack canary segment base is cached-aligned:
 *   "For Intel Atom processors, avoid non zero segment base address
 *    that is not aligned to cache line boundary at all cost."
 * (Optim Ref Manual Assembly/Compiler Coding Rule 15.)
 */
struct stack_canary {
	char __pad[20];		/* canary at %gs:20 */
	unsigned long canary;
};
DECLARE_PER_CPU_ALIGNED(struct stack_canary, stack_canary);
#endif
/*
 * per-CPU IRQ handling stacks
 */
struct irq_stack {
	u32                     stack[THREAD_SIZE/sizeof(u32)];
} __aligned(THREAD_SIZE);

DECLARE_PER_CPU(struct irq_stack *, hardirq_stack);
DECLARE_PER_CPU(struct irq_stack *, softirq_stack);
#endif	/* X86_64 */

extern unsigned int xstate_size;

struct perf_event;

typedef struct {
	unsigned long		seg;
} mm_segment_t;

struct thread_struct {
	/* Cached TLS descriptors: */
	struct desc_struct	tls_array[GDT_ENTRY_TLS_ENTRIES];
	unsigned long		sp0;
	unsigned long		sp;
#ifdef CONFIG_X86_32
	unsigned long		sysenter_cs;
#else
	unsigned short		es;
	unsigned short		ds;
	unsigned short		fsindex;
	unsigned short		gsindex;
#endif
#ifdef CONFIG_X86_32
	unsigned long		ip;
#endif
#ifdef CONFIG_X86_64
	unsigned long		fsbase;
	unsigned long		gsbase;
#else
	/*
	 * XXX: this could presumably be unsigned short.  Alternatively,
	 * 32-bit kernels could be taught to use fsindex instead.
	 */
	unsigned long fs;
	unsigned long gs;
#endif

	/* Save middle states of ptrace breakpoints */
	struct perf_event	*ptrace_bps[HBP_NUM];
	/* Debug status used for traps, single steps, etc... */
	unsigned long           debugreg6;
	/* Keep track of the exact dr7 value set by the user */
	unsigned long           ptrace_dr7;
	/* Fault info: */
	unsigned long		cr2;
	unsigned long		trap_nr;
	unsigned long		error_code;
#ifdef CONFIG_VM86
	/* Virtual 86 mode info */
	struct vm86		*vm86;
#endif
	/* IO permissions: */
	unsigned long		*io_bitmap_ptr;
	unsigned long		iopl;
	/* Max allowed port in the bitmap, in bytes: */
	unsigned		io_bitmap_max;

	mm_segment_t		addr_limit;

	unsigned int		sig_on_uaccess_err:1;
	unsigned int		uaccess_err:1;	/* uaccess failed */

	/* Floating point and extended processor state */
	struct fpu		fpu;
	/*
	 * WARNING: 'fpu' is dynamically-sized.  It *MUST* be at
	 * the end.
	 */
};

/*
 * Set IOPL bits in EFLAGS from given mask
 */
static inline void native_set_iopl_mask(unsigned mask)
{
#ifdef CONFIG_X86_32
	unsigned int reg;

	asm volatile ("pushfl;"
		      "popl %0;"
		      "andl %1, %0;"
		      "orl %2, %0;"
		      "pushl %0;"
		      "popfl"
		      : "=&r" (reg)
		      : "i" (~X86_EFLAGS_IOPL), "r" (mask));
#endif
}

static inline void
native_load_sp0(struct tss_struct *tss, struct thread_struct *thread)
{
	tss->x86_tss.sp0 = thread->sp0;
#ifdef CONFIG_X86_32
	/* Only happens when SEP is enabled, no need to test "SEP"arately: */
	if (unlikely(tss->x86_tss.ss1 != thread->sysenter_cs)) {
		tss->x86_tss.ss1 = thread->sysenter_cs;
		wrmsr(MSR_IA32_SYSENTER_CS, thread->sysenter_cs, 0);
	}
#endif
}

static inline void native_swapgs(void)
{
#ifdef CONFIG_X86_64
	asm volatile("swapgs" ::: "memory");
#endif
}

static inline unsigned long current_top_of_stack(void)
{
#ifdef CONFIG_X86_64
	return this_cpu_read_stable(cpu_tss.x86_tss.sp0);
#else
	/* sp0 on x86_32 is special in and around vm86 mode. */
	return this_cpu_read_stable(cpu_current_top_of_stack);
#endif
}

#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
#else
#define __cpuid			native_cpuid

static inline void load_sp0(struct tss_struct *tss,
			    struct thread_struct *thread)
{
	native_load_sp0(tss, thread);
}

#define set_iopl_mask native_set_iopl_mask
#endif /* CONFIG_PARAVIRT */

/* Free all resources held by a thread. */
extern void release_thread(struct task_struct *);

unsigned long get_wchan(struct task_struct *p);

/*
 * Generic CPUID function
 * clear %ecx since some cpus (Cyrix MII) do not set or clear %ecx
 * resulting in stale register contents being returned.
 */
static inline void cpuid(unsigned int op,
			 unsigned int *eax, unsigned int *ebx,
			 unsigned int *ecx, unsigned int *edx)
{
	*eax = op;
	*ecx = 0;
	__cpuid(eax, ebx, ecx, edx);
}

/* Some CPUID calls want 'count' to be placed in ecx */
static inline void cpuid_count(unsigned int op, int count,
			       unsigned int *eax, unsigned int *ebx,
			       unsigned int *ecx, unsigned int *edx)
{
	*eax = op;
	*ecx = count;
	__cpuid(eax, ebx, ecx, edx);
}

/*
 * CPUID functions returning a single datum
 */
static inline unsigned int cpuid_eax(unsigned int op)
{
	unsigned int eax, ebx, ecx, edx;

	cpuid(op, &eax, &ebx, &ecx, &edx);

	return eax;
}

static inline unsigned int cpuid_ebx(unsigned int op)
{
	unsigned int eax, ebx, ecx, edx;

	cpuid(op, &eax, &ebx, &ecx, &edx);

	return ebx;
}

static inline unsigned int cpuid_ecx(unsigned int op)
{
	unsigned int eax, ebx, ecx, edx;

	cpuid(op, &eax, &ebx, &ecx, &edx);

	return ecx;
}

static inline unsigned int cpuid_edx(unsigned int op)
{
	unsigned int eax, ebx, ecx, edx;

	cpuid(op, &eax, &ebx, &ecx, &edx);

	return edx;
}

/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
static __always_inline void rep_nop(void)
{
	asm volatile("rep; nop" ::: "memory");
}

static __always_inline void cpu_relax(void)
{
	rep_nop();
}

#define cpu_relax_lowlatency() cpu_relax()

/* Stop speculative execution and prefetching of modified code. */
static inline void sync_core(void)
{
	int tmp;

#ifdef CONFIG_M486
	/*
	 * Do a CPUID if available, otherwise do a jump.  The jump
	 * can conveniently enough be the jump around CPUID.
	 */
	asm volatile("cmpl %2,%1\n\t"
		     "jl 1f\n\t"
		     "cpuid\n"
		     "1:"
		     : "=a" (tmp)
		     : "rm" (boot_cpu_data.cpuid_level), "ri" (0), "0" (1)
		     : "ebx", "ecx", "edx", "memory");
#else
	/*
	 * CPUID is a barrier to speculative execution.
	 * Prefetched instructions are automatically
	 * invalidated when modified.
	 */
	asm volatile("cpuid"
		     : "=a" (tmp)
		     : "0" (1)
		     : "ebx", "ecx", "edx", "memory");
#endif
}

extern void select_idle_routine(const struct cpuinfo_x86 *c);
extern void init_amd_e400_c1e_mask(void);

extern unsigned long		boot_option_idle_override;
extern bool			amd_e400_c1e_detected;

enum idle_boot_override {IDLE_NO_OVERRIDE=0, IDLE_HALT, IDLE_NOMWAIT,
			 IDLE_POLL};

extern void enable_sep_cpu(void);
extern int sysenter_setup(void);

extern void early_trap_init(void);
void early_trap_pf_init(void);

/* Defined in head.S */
extern struct desc_ptr		early_gdt_descr;

extern void cpu_set_gdt(int);
extern void switch_to_new_gdt(int);
extern void load_percpu_segment(int);
extern void cpu_init(void);

static inline unsigned long get_debugctlmsr(void)
{
	unsigned long debugctlmsr = 0;

#ifndef CONFIG_X86_DEBUGCTLMSR
	if (boot_cpu_data.x86 < 6)
		return 0;
#endif
	rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctlmsr);

	return debugctlmsr;
}

static inline void update_debugctlmsr(unsigned long debugctlmsr)
{
#ifndef CONFIG_X86_DEBUGCTLMSR
	if (boot_cpu_data.x86 < 6)
		return;
#endif
	wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctlmsr);
}

extern void set_task_blockstep(struct task_struct *task, bool on);

/* Boot loader type from the setup header: */
extern int			bootloader_type;
extern int			bootloader_version;

extern char			ignore_fpu_irq;

#define HAVE_ARCH_PICK_MMAP_LAYOUT 1
#define ARCH_HAS_PREFETCHW
#define ARCH_HAS_SPINLOCK_PREFETCH

#ifdef CONFIG_X86_32
# define BASE_PREFETCH		""
# define ARCH_HAS_PREFETCH
#else
# define BASE_PREFETCH		"prefetcht0 %P1"
#endif

/*
 * Prefetch instructions for Pentium III (+) and AMD Athlon (+)
 *
 * It's not worth to care about 3dnow prefetches for the K6
 * because they are microcoded there and very slow.
 */
static inline void prefetch(const void *x)
{
	alternative_input(BASE_PREFETCH, "prefetchnta %P1",
			  X86_FEATURE_XMM,
			  "m" (*(const char *)x));
}

/*
 * 3dnow prefetch to get an exclusive cache line.
 * Useful for spinlocks to avoid one state transition in the
 * cache coherency protocol:
 */
static inline void prefetchw(const void *x)
{
	alternative_input(BASE_PREFETCH, "prefetchw %P1",
			  X86_FEATURE_3DNOWPREFETCH,
			  "m" (*(const char *)x));
}

static inline void spin_lock_prefetch(const void *x)
{
	prefetchw(x);
}

#define TOP_OF_INIT_STACK ((unsigned long)&init_stack + sizeof(init_stack) - \
			   TOP_OF_KERNEL_STACK_PADDING)

#ifdef CONFIG_X86_32
/*
 * User space process size: 3GB (default).
 */
#define TASK_SIZE		PAGE_OFFSET
#define TASK_SIZE_MAX		TASK_SIZE
#define STACK_TOP		TASK_SIZE
#define STACK_TOP_MAX		STACK_TOP

#define INIT_THREAD  {							  \
	.sp0			= TOP_OF_INIT_STACK,			  \
	.sysenter_cs		= __KERNEL_CS,				  \
	.io_bitmap_ptr		= NULL,					  \
	.addr_limit		= KERNEL_DS,				  \
}

extern unsigned long thread_saved_pc(struct task_struct *tsk);

/*
 * TOP_OF_KERNEL_STACK_PADDING reserves 8 bytes on top of the ring0 stack.
 * This is necessary to guarantee that the entire "struct pt_regs"
 * is accessible even if the CPU haven't stored the SS/ESP registers
 * on the stack (interrupt gate does not save these registers
 * when switching to the same priv ring).
 * Therefore beware: accessing the ss/esp fields of the
 * "struct pt_regs" is possible, but they may contain the
 * completely wrong values.
 */
#define task_pt_regs(task) \
({									\
	unsigned long __ptr = (unsigned long)task_stack_page(task);	\
	__ptr += THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;		\
	((struct pt_regs *)__ptr) - 1;					\
})

#define KSTK_ESP(task)		(task_pt_regs(task)->sp)

#else
/*
 * User space process size. 47bits minus one guard page.  The guard
 * page is necessary on Intel CPUs: if a SYSCALL instruction is at
 * the highest possible canonical userspace address, then that
 * syscall will enter the kernel with a non-canonical return
 * address, and SYSRET will explode dangerously.  We avoid this
 * particular problem by preventing anything from being mapped
 * at the maximum canonical address.
 */
#define TASK_SIZE_MAX	((1UL << 47) - PAGE_SIZE)

/* This decides where the kernel will search for a free chunk of vm
 * space during mmap's.
 */
#define IA32_PAGE_OFFSET	((current->personality & ADDR_LIMIT_3GB) ? \
					0xc0000000 : 0xFFFFe000)

#define TASK_SIZE		(test_thread_flag(TIF_ADDR32) ? \
					IA32_PAGE_OFFSET : TASK_SIZE_MAX)
#define TASK_SIZE_OF(child)	((test_tsk_thread_flag(child, TIF_ADDR32)) ? \
					IA32_PAGE_OFFSET : TASK_SIZE_MAX)

#define STACK_TOP		TASK_SIZE
#define STACK_TOP_MAX		TASK_SIZE_MAX

#define INIT_THREAD  {						\
	.sp0			= TOP_OF_INIT_STACK,		\
	.addr_limit		= KERNEL_DS,			\
}

/*
 * Return saved PC of a blocked thread.
 * What is this good for? it will be always the scheduler or ret_from_fork.
 */
#define thread_saved_pc(t)	READ_ONCE_NOCHECK(*(unsigned long *)((t)->thread.sp - 8))

#define task_pt_regs(tsk)	((struct pt_regs *)(tsk)->thread.sp0 - 1)
extern unsigned long KSTK_ESP(struct task_struct *task);

#endif /* CONFIG_X86_64 */

extern void start_thread(struct pt_regs *regs, unsigned long new_ip,
					       unsigned long new_sp);

/*
 * This decides where the kernel will search for a free chunk of vm
 * space during mmap's.
 */
#define TASK_UNMAPPED_BASE	(PAGE_ALIGN(TASK_SIZE / 3))

#define KSTK_EIP(task)		(task_pt_regs(task)->ip)

/* Get/set a process' ability to use the timestamp counter instruction */
#define GET_TSC_CTL(adr)	get_tsc_mode((adr))
#define SET_TSC_CTL(val)	set_tsc_mode((val))

extern int get_tsc_mode(unsigned long adr);
extern int set_tsc_mode(unsigned int val);

/* Register/unregister a process' MPX related resource */
#define MPX_ENABLE_MANAGEMENT()	mpx_enable_management()
#define MPX_DISABLE_MANAGEMENT()	mpx_disable_management()

#ifdef CONFIG_X86_INTEL_MPX
extern int mpx_enable_management(void);
extern int mpx_disable_management(void);
#else
static inline int mpx_enable_management(void)
{
	return -EINVAL;
}
static inline int mpx_disable_management(void)
{
	return -EINVAL;
}
#endif /* CONFIG_X86_INTEL_MPX */

extern u16 amd_get_nb_id(int cpu);
extern u32 amd_get_nodes_per_socket(void);

static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
{
	uint32_t base, eax, signature[3];

	for (base = 0x40000000; base < 0x40010000; base += 0x100) {
		cpuid(base, &eax, &signature[0], &signature[1], &signature[2]);

		if (!memcmp(sig, signature, 12) &&
		    (leaves == 0 || ((eax - base) >= leaves)))
			return base;
	}

	return 0;
}

extern unsigned long arch_align_stack(unsigned long sp);
extern void free_init_pages(char *what, unsigned long begin, unsigned long end);

void default_idle(void);
#ifdef	CONFIG_XEN
bool xen_set_default_idle(void);
#else
#define xen_set_default_idle 0
#endif

void stop_this_cpu(void *dummy);
void df_debug(struct pt_regs *regs, long error_code);
#endif /* _ASM_X86_PROCESSOR_H */