/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_SEGMENT_H
#define _ASM_X86_SEGMENT_H

#include <linux/const.h>
#include <asm/alternative.h>
#include <asm/ibt.h>

/*
 * Constructor for a conventional segment GDT (or LDT) entry.
 * This is a macro so it can be used in initializers.
 */
#define GDT_ENTRY(flags, base, limit)                   \
        ((((base)  & _AC(0xff000000,ULL)) << (56-24)) | \
         (((flags) & _AC(0x0000f0ff,ULL)) << 40) |      \
         (((limit) & _AC(0x000f0000,ULL)) << (48-16)) | \
         (((base)  & _AC(0x00ffffff,ULL)) << 16) |      \
         (((limit) & _AC(0x0000ffff,ULL))))

/* Simple and small GDT entries for booting only: */

#define GDT_ENTRY_BOOT_CS       2
#define GDT_ENTRY_BOOT_DS       3
#define GDT_ENTRY_BOOT_TSS      4
#define __BOOT_CS               (GDT_ENTRY_BOOT_CS*8)
#define __BOOT_DS               (GDT_ENTRY_BOOT_DS*8)
#define __BOOT_TSS              (GDT_ENTRY_BOOT_TSS*8)

/*
 * Bottom two bits of selector give the ring
 * privilege level
 */
#define SEGMENT_RPL_MASK        0x3

/*
 * When running on Xen PV, the actual privilege level of the kernel is 1,
 * not 0. Testing the Requested Privilege Level in a segment selector to
 * determine whether the context is user mode or kernel mode with
 * SEGMENT_RPL_MASK is wrong because the PV kernel's privilege level
 * matches the 0x3 mask.
 *
 * Testing with USER_SEGMENT_RPL_MASK is valid for both native and Xen PV
 * kernels because privilege level 2 is never used.
 */
#define USER_SEGMENT_RPL_MASK   0x2

/* User mode is privilege level 3: */
#define USER_RPL                0x3

/* Bit 2 is Table Indicator (TI): selects between LDT or GDT */
#define SEGMENT_TI_MASK         0x4
/* LDT segment has TI set ... */
#define SEGMENT_LDT             0x4
/* ... GDT has it cleared */
#define SEGMENT_GDT             0x0

#define GDT_ENTRY_INVALID_SEG   0

#if defined(CONFIG_X86_32) && !defined(BUILD_VDSO32_64)
/*
 * The layout of the per-CPU GDT under Linux:
 *
 *   0 - null                                                           <=== cacheline #1
 *   1 - reserved
 *   2 - reserved
 *   3 - reserved
 *
 *   4 - unused                                                         <=== cacheline #2
 *   5 - unused
 *
 *  ------- start of TLS (Thread-Local Storage) segments:
 *
 *   6 - TLS segment #1                 [ glibc's TLS segment ]
 *   7 - TLS segment #2                 [ Wine's %fs Win32 segment ]
 *   8 - TLS segment #3                                                 <=== cacheline #3
 *   9 - reserved
 *  10 - reserved
 *  11 - reserved
 *
 *  ------- start of kernel segments:
 *
 *  12 - kernel code segment                                            <=== cacheline #4
 *  13 - kernel data segment
 *  14 - default user CS
 *  15 - default user DS
 *  16 - TSS                                                            <=== cacheline #5
 *  17 - LDT
 *  18 - PNPBIOS support (16->32 gate)
 *  19 - PNPBIOS support
 *  20 - PNPBIOS support                                                <=== cacheline #6
 *  21 - PNPBIOS support
 *  22 - PNPBIOS support
 *  23 - APM BIOS support
 *  24 - APM BIOS support                                               <=== cacheline #7
 *  25 - APM BIOS support
 *
 *  26 - ESPFIX small SS
 *  27 - per-cpu                        [ offset to per-cpu data area ]
 *  28 - VDSO getcpu
 *  29 - unused
 *  30 - unused
 *  31 - TSS for double fault handler
 */
#define GDT_ENTRY_TLS_MIN               6
#define GDT_ENTRY_TLS_MAX               (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)

#define GDT_ENTRY_KERNEL_CS             12
#define GDT_ENTRY_KERNEL_DS             13
#define GDT_ENTRY_DEFAULT_USER_CS       14
#define GDT_ENTRY_DEFAULT_USER_DS       15
#define GDT_ENTRY_TSS                   16
#define GDT_ENTRY_LDT                   17
#define GDT_ENTRY_PNPBIOS_CS32          18
#define GDT_ENTRY_PNPBIOS_CS16          19
#define GDT_ENTRY_PNPBIOS_DS            20
#define GDT_ENTRY_PNPBIOS_TS1           21
#define GDT_ENTRY_PNPBIOS_TS2           22
#define GDT_ENTRY_APMBIOS_BASE          23

#define GDT_ENTRY_ESPFIX_SS             26
#define GDT_ENTRY_PERCPU                27
#define GDT_ENTRY_CPUNODE               28

#define GDT_ENTRY_DOUBLEFAULT_TSS       31

/*
 * Number of entries in the GDT table:
 */
#define GDT_ENTRIES                     32

/*
 * Segment selector values corresponding to the above entries:
 */

#define __KERNEL_CS                     (GDT_ENTRY_KERNEL_CS*8)
#define __KERNEL_DS                     (GDT_ENTRY_KERNEL_DS*8)
#define __USER_DS                       (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
#define __USER_CS                       (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
#define __USER32_CS                     __USER_CS
#define __ESPFIX_SS                     (GDT_ENTRY_ESPFIX_SS*8)

/* segment for calling fn: */
#define PNP_CS32                        (GDT_ENTRY_PNPBIOS_CS32*8)
/* code segment for BIOS: */
#define PNP_CS16                        (GDT_ENTRY_PNPBIOS_CS16*8)

/* "Is this PNP code selector (PNP_CS32 or PNP_CS16)?" */
#define SEGMENT_IS_PNP_CODE(x)          (((x) & 0xf4) == PNP_CS32)

/* data segment for BIOS: */
#define PNP_DS                          (GDT_ENTRY_PNPBIOS_DS*8)
/* transfer data segment: */
#define PNP_TS1                         (GDT_ENTRY_PNPBIOS_TS1*8)
/* another data segment: */
#define PNP_TS2                         (GDT_ENTRY_PNPBIOS_TS2*8)

#ifdef CONFIG_SMP
# define __KERNEL_PERCPU                (GDT_ENTRY_PERCPU*8)
#else
# define __KERNEL_PERCPU                0
#endif

#define __CPUNODE_SEG                   (GDT_ENTRY_CPUNODE*8 + 3)

#else /* 64-bit: */

#include <asm/cache.h>

#define GDT_ENTRY_KERNEL32_CS           1
#define GDT_ENTRY_KERNEL_CS             2
#define GDT_ENTRY_KERNEL_DS             3

/*
 * We cannot use the same code segment descriptor for user and kernel mode,
 * not even in long flat mode, because of different DPL.
 *
 * GDT layout to get 64-bit SYSCALL/SYSRET support right. SYSRET hardcodes
 * selectors:
 *
 *   if returning to 32-bit userspace: cs = STAR.SYSRET_CS,
 *   if returning to 64-bit userspace: cs = STAR.SYSRET_CS+16,
 *
 * ss = STAR.SYSRET_CS+8 (in either case)
 *
 * thus USER_DS should be between 32-bit and 64-bit code selectors:
 */
#define GDT_ENTRY_DEFAULT_USER32_CS     4
#define GDT_ENTRY_DEFAULT_USER_DS       5
#define GDT_ENTRY_DEFAULT_USER_CS       6

/* Needs two entries */
#define GDT_ENTRY_TSS                   8
/* Needs two entries */
#define GDT_ENTRY_LDT                   10

#define GDT_ENTRY_TLS_MIN               12
#define GDT_ENTRY_TLS_MAX               14

#define GDT_ENTRY_CPUNODE               15

/*
 * Number of entries in the GDT table:
 */
#define GDT_ENTRIES                     16

/*
 * Segment selector values corresponding to the above entries:
 *
 * Note, selectors also need to have a correct RPL,
 * expressed with the +3 value for user-space selectors:
 */
#define __KERNEL32_CS                   (GDT_ENTRY_KERNEL32_CS*8)
#define __KERNEL_CS                     (GDT_ENTRY_KERNEL_CS*8)
#define __KERNEL_DS                     (GDT_ENTRY_KERNEL_DS*8)
#define __USER32_CS                     (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3)
#define __USER_DS                       (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
#define __USER_CS                       (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
#define __CPUNODE_SEG                   (GDT_ENTRY_CPUNODE*8 + 3)

#endif

#define IDT_ENTRIES                     256
#define NUM_EXCEPTION_VECTORS           32

/* Bitmask of exception vectors which push an error code on the stack: */
#define EXCEPTION_ERRCODE_MASK          0x20027d00

#define GDT_SIZE                        (GDT_ENTRIES*8)
#define GDT_ENTRY_TLS_ENTRIES           3
#define TLS_SIZE                        (GDT_ENTRY_TLS_ENTRIES* 8)

/* Bit size and mask of CPU number stored in the per CPU data (and TSC_AUX) */
#define VDSO_CPUNODE_BITS               12
#define VDSO_CPUNODE_MASK               0xfff

#ifndef __ASSEMBLER__

/* Helper functions to store/load CPU and node numbers */

static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node)
{
        return (node << VDSO_CPUNODE_BITS) | cpu;
}

static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
{
        unsigned long p;

        /*
         * Load CPU and node number from the GDT.  LSL is faster than RDTSCP
         * and works on all CPUs.  This is volatile so that it orders
         * correctly with respect to barrier() and to keep GCC from cleverly
         * hoisting it out of the calling function.
         *
         * If RDPID is available, use it.
         */
        alternative_io ("lsl %[seg],%k[p]",
                        "rdpid %[p]",
                        X86_FEATURE_RDPID,
                        [p] "=r" (p), [seg] "r" (__CPUNODE_SEG));

        if (cpu)
                *cpu = (p & VDSO_CPUNODE_MASK);
        if (node)
                *node = (p >> VDSO_CPUNODE_BITS);
}

#endif /* !__ASSEMBLER__ */

#ifdef __KERNEL__

/*
 * early_idt_handler_array is an array of entry points referenced in the
 * early IDT.  For simplicity, it's a real array with one entry point
 * every nine bytes.  That leaves room for an optional 'push $0' if the
 * vector has no error code (two bytes), a 'push $vector_number' (two
 * bytes), and a jump to the common entry code (up to five bytes).
 */
#define EARLY_IDT_HANDLER_SIZE (9 + ENDBR_INSN_SIZE)

/*
 * xen_early_idt_handler_array is for Xen pv guests: for each entry in
 * early_idt_handler_array it contains a prequel in the form of
 * pop %rcx; pop %r11; jmp early_idt_handler_array[i]; summing up to
 * max 8 bytes.
 */
#define XEN_EARLY_IDT_HANDLER_SIZE (8 + ENDBR_INSN_SIZE)

#ifndef __ASSEMBLER__

extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
extern void early_ignore_irq(void);

#ifdef CONFIG_XEN_PV
extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE];
#endif

/*
 * Load a segment. Fall back on loading the zero segment if something goes
 * wrong.  This variant assumes that loading zero fully clears the segment.
 * This is always the case on Intel CPUs and, even on 64-bit AMD CPUs, any
 * failure to fully clear the cached descriptor is only observable for
 * FS and GS.
 */
#define __loadsegment_simple(seg, value)                                \
do {                                                                    \
        unsigned short __val = (value);                                 \
                                                                        \
        asm volatile("                                          \n"     \
                     "1:        movl %k0,%%" #seg "             \n"     \
                     _ASM_EXTABLE_TYPE_REG(1b, 1b, EX_TYPE_ZERO_REG, %k0)\
                     : "+r" (__val) : : "memory");                      \
} while (0)

#define __loadsegment_ss(value) __loadsegment_simple(ss, (value))
#define __loadsegment_ds(value) __loadsegment_simple(ds, (value))
#define __loadsegment_es(value) __loadsegment_simple(es, (value))

#ifdef CONFIG_X86_32

/*
 * On 32-bit systems, the hidden parts of FS and GS are unobservable if
 * the selector is NULL, so there's no funny business here.
 */
#define __loadsegment_fs(value) __loadsegment_simple(fs, (value))
#define __loadsegment_gs(value) __loadsegment_simple(gs, (value))

#else

static inline void __loadsegment_fs(unsigned short value)
{
        asm volatile("                                          \n"
                     "1:        movw %0, %%fs                   \n"
                     "2:                                        \n"

                     _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_CLEAR_FS)

                     : : "rm" (value) : "memory");
}

/* __loadsegment_gs is intentionally undefined.  Use load_gs_index instead. */

#endif

#define loadsegment(seg, value) __loadsegment_ ## seg (value)

/*
 * Save a segment register away:
 */
#define savesegment(seg, value)                         \
        asm("movl %%" #seg ",%k0" : "=r" (value) : : "memory")

#endif /* !__ASSEMBLER__ */
#endif /* __KERNEL__ */

#endif /* _ASM_X86_SEGMENT_H */