/* SPDX-License-Identifier: GPL-2.0 */
/*
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Enhanced CPU detection and feature setting code by Mike Jagdis
 *  and Martin Mares, November 1997.
 */

.text
#include <linux/export.h>
#include <linux/threads.h>
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/page_types.h>
#include <asm/pgtable_types.h>
#include <asm/cache.h>
#include <asm/thread_info.h>
#include <asm/asm-offsets.h>
#include <asm/setup.h>
#include <asm/processor-flags.h>
#include <asm/msr-index.h>
#include <asm/cpufeatures.h>
#include <asm/percpu.h>
#include <asm/nops.h>
#include <asm/nospec-branch.h>
#include <asm/bootparam.h>
#include <asm/pgtable_32.h>

/* Physical address */
#define pa(X) ((X) - __PAGE_OFFSET)

/*
 * References to members of the new_cpu_data structure.
 */

#define X86             new_cpu_data+CPUINFO_x86
#define X86_VENDOR      new_cpu_data+CPUINFO_x86_vendor
#define X86_MODEL       new_cpu_data+CPUINFO_x86_model
#define X86_STEPPING    new_cpu_data+CPUINFO_x86_stepping
#define X86_HARD_MATH   new_cpu_data+CPUINFO_hard_math
#define X86_CPUID       new_cpu_data+CPUINFO_cpuid_level
#define X86_CAPABILITY  new_cpu_data+CPUINFO_x86_capability
#define X86_VENDOR_ID   new_cpu_data+CPUINFO_x86_vendor_id

/*
 * Worst-case size of the kernel mapping we need to make:
 * a relocatable kernel can live anywhere in lowmem, so we need to be able
 * to map all of lowmem.
 */
KERNEL_PAGES = LOWMEM_PAGES

INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
RESERVE_BRK(pagetables, INIT_MAP_SIZE)

/*
 * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
 * %esi points to the real-mode code as a 32-bit pointer.
 * CS and DS must be 4 GB flat segments, but we don't depend on
 * any particular GDT layout, because we load our own as soon as we
 * can.
 */
        __INIT
SYM_CODE_START(startup_32)
        movl pa(initial_stack),%ecx
        
/*
 * Set segments to known values.
 */
        lgdt pa(boot_gdt_descr)
        movl $(__BOOT_DS),%eax
        movl %eax,%ds
        movl %eax,%es
        movl %eax,%fs
        movl %eax,%gs
        movl %eax,%ss
        leal -__PAGE_OFFSET(%ecx),%esp

/*
 * Clear BSS first so that there are no surprises...
 */
        cld
        xorl %eax,%eax
        movl $pa(__bss_start),%edi
        movl $pa(__bss_stop),%ecx
        subl %edi,%ecx
        shrl $2,%ecx
        rep stosl
/*
 * Copy bootup parameters out of the way.
 * Note: %esi still has the pointer to the real-mode data.
 * With the kexec as boot loader, parameter segment might be loaded beyond
 * kernel image and might not even be addressable by early boot page tables.
 * (kexec on panic case). Hence copy out the parameters before initializing
 * page tables.
 */
        movl $pa(boot_params),%edi
        movl $(PARAM_SIZE/4),%ecx
        cld
        rep movsl
        movl pa(boot_params) + NEW_CL_POINTER,%esi
        andl %esi,%esi
        jz 1f                   # No command line
        movl $pa(boot_command_line),%edi
        movl $(COMMAND_LINE_SIZE/4),%ecx
        rep movsl
1:

#ifdef CONFIG_OLPC
        /* save OFW's pgdir table for later use when calling into OFW */
        movl %cr3, %eax
        movl %eax, pa(olpc_ofw_pgd)
#endif

        /* Create early pagetables. */
        call  mk_early_pgtbl_32

        /* Do early initialization of the fixmap area */
        movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
#ifdef  CONFIG_X86_PAE
#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
        movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
#else
        movl %eax,pa(initial_page_table+0xffc)
#endif

        jmp .Ldefault_entry
SYM_CODE_END(startup_32)

/*
 * Non-boot CPU entry point; entered from trampoline.S
 * We can't lgdt here, because lgdt itself uses a data segment, but
 * we know the trampoline has already loaded the boot_gdt for us.
 *
 * If cpu hotplug is not supported then this code can go in init section
 * which will be freed later
 */
#ifdef CONFIG_HOTPLUG_CPU
       .text
#endif
SYM_FUNC_START(startup_32_smp)
        cld
        movl $(__BOOT_DS),%eax
        movl %eax,%ds
        movl %eax,%es
        movl %eax,%fs
        movl %eax,%gs
        movl pa(initial_stack),%ecx
        movl %eax,%ss
        leal -__PAGE_OFFSET(%ecx),%esp

.Ldefault_entry:
        movl $(CR0_STATE & ~X86_CR0_PG),%eax
        movl %eax,%cr0

/*
 * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
 * bits like NT set. This would confuse the debugger if this code is traced. So
 * initialize them properly now before switching to protected mode. That means
 * DF in particular (even though we have cleared it earlier after copying the
 * command line) because GCC expects it.
 */
        pushl $0
        popfl

/*
 * New page tables may be in 4Mbyte page mode and may be using the global pages.
 *
 * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
 * if and only if CPUID exists and has flags other than the FPU flag set.
 */
        movl $-1,pa(X86_CPUID)          # preset CPUID level
        movl $X86_EFLAGS_ID,%ecx
        pushl %ecx
        popfl                           # set EFLAGS=ID
        pushfl
        popl %eax                       # get EFLAGS
        testl $X86_EFLAGS_ID,%eax       # did EFLAGS.ID remained set?
        jz .Lenable_paging              # hw disallowed setting of ID bit
                                        # which means no CPUID and no CR4

        xorl %eax,%eax
        cpuid
        movl %eax,pa(X86_CPUID)         # save largest std CPUID function

        movl $1,%eax
        cpuid
        andl $~1,%edx                   # Ignore CPUID.FPU
        jz .Lenable_paging              # No flags or only CPUID.FPU = no CR4

        movl pa(mmu_cr4_features),%eax
        movl %eax,%cr4

        testb $X86_CR4_PAE, %al         # check if PAE is enabled
        jz .Lenable_paging

        /* Check if extended functions are implemented */
        movl $0x80000000, %eax
        cpuid
        /* Value must be in the range 0x80000001 to 0x8000ffff */
        subl $0x80000001, %eax
        cmpl $(0x8000ffff-0x80000001), %eax
        ja .Lenable_paging

        /* Clear bogus XD_DISABLE bits */
        call verify_cpu

        mov $0x80000001, %eax
        cpuid
        /* Execute Disable bit supported? */
        btl $(X86_FEATURE_NX & 31), %edx
        jnc .Lenable_paging

        /* Setup EFER (Extended Feature Enable Register) */
        movl $MSR_EFER, %ecx
        rdmsr

        btsl $_EFER_NX, %eax
        /* Make changes effective */
        wrmsr

.Lenable_paging:

/*
 * Enable paging
 */
        movl $pa(initial_page_table), %eax
        movl %eax,%cr3          /* set the page table pointer.. */
        movl $CR0_STATE,%eax
        movl %eax,%cr0          /* ..and set paging (PG) bit */
        ljmp $__BOOT_CS,$1f     /* Clear prefetch and normalize %eip */
1:
        /* Shift the stack pointer to a virtual address */
        addl $__PAGE_OFFSET, %esp

/*
 * Check if it is 486
 */
        movb $4,X86                     # at least 486
        cmpl $-1,X86_CPUID
        je .Lis486

        /* get vendor info */
        xorl %eax,%eax                  # call CPUID with 0 -> return vendor ID
        cpuid
        movl %eax,X86_CPUID             # save CPUID level
        movl %ebx,X86_VENDOR_ID         # lo 4 chars
        movl %edx,X86_VENDOR_ID+4       # next 4 chars
        movl %ecx,X86_VENDOR_ID+8       # last 4 chars

        orl %eax,%eax                   # do we have processor info as well?
        je .Lis486

        movl $1,%eax            # Use the CPUID instruction to get CPU type
        cpuid
        movb %al,%cl            # save reg for future use
        andb $0x0f,%ah          # mask processor family
        movb %ah,X86
        andb $0xf0,%al          # mask model
        shrb $4,%al
        movb %al,X86_MODEL
        andb $0x0f,%cl          # mask mask revision
        movb %cl,X86_STEPPING
        movl %edx,X86_CAPABILITY

.Lis486:
        movl $0x50022,%ecx      # set AM, WP, NE and MP
        movl %cr0,%eax
        andl $0x80000011,%eax   # Save PG,PE,ET
        orl %ecx,%eax
        movl %eax,%cr0

        lgdt early_gdt_descr
        ljmp $(__KERNEL_CS),$1f
1:      movl $(__KERNEL_DS),%eax        # reload all the segment registers
        movl %eax,%ss                   # after changing gdt.

        movl $(__USER_DS),%eax          # DS/ES contains default USER segment
        movl %eax,%ds
        movl %eax,%es

        movl $(__KERNEL_PERCPU), %eax
        movl %eax,%fs                   # set this cpu's percpu

        xorl %eax,%eax
        movl %eax,%gs                   # clear possible garbage in %gs

        xorl %eax,%eax                  # Clear LDT
        lldt %ax

        call *(initial_code)
1:      jmp 1b
SYM_FUNC_END(startup_32_smp)

#include "verify_cpu.S"

__INIT
SYM_FUNC_START(early_idt_handler_array)
        # 36(%esp) %eflags
        # 32(%esp) %cs
        # 28(%esp) %eip
        # 24(%rsp) error code
        i = 0
        .rept NUM_EXCEPTION_VECTORS
        .if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
        pushl $0                # Dummy error code, to make stack frame uniform
        .endif
        pushl $i                # 20(%esp) Vector number
        jmp early_idt_handler_common
        i = i + 1
        .fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
        .endr
SYM_FUNC_END(early_idt_handler_array)
        
SYM_CODE_START_LOCAL(early_idt_handler_common)
        /*
         * The stack is the hardware frame, an error code or zero, and the
         * vector number.
         */
        cld

        incl %ss:early_recursion_flag

        /* The vector number is in pt_regs->gs */

        cld
        pushl   %fs             /* pt_regs->fs (__fsh varies by model) */
        pushl   %es             /* pt_regs->es (__esh varies by model) */
        pushl   %ds             /* pt_regs->ds (__dsh varies by model) */
        pushl   %eax            /* pt_regs->ax */
        pushl   %ebp            /* pt_regs->bp */
        pushl   %edi            /* pt_regs->di */
        pushl   %esi            /* pt_regs->si */
        pushl   %edx            /* pt_regs->dx */
        pushl   %ecx            /* pt_regs->cx */
        pushl   %ebx            /* pt_regs->bx */

        /* Fix up DS and ES */
        movl    $(__KERNEL_DS), %ecx
        movl    %ecx, %ds
        movl    %ecx, %es

        /* Load the vector number into EDX */
        movl    PT_GS(%esp), %edx

        /* Load GS into pt_regs->gs (and maybe clobber __gsh) */
        movw    %gs, PT_GS(%esp)

        movl    %esp, %eax      /* args are pt_regs (EAX), trapnr (EDX) */
        call    early_fixup_exception

        popl    %ebx            /* pt_regs->bx */
        popl    %ecx            /* pt_regs->cx */
        popl    %edx            /* pt_regs->dx */
        popl    %esi            /* pt_regs->si */
        popl    %edi            /* pt_regs->di */
        popl    %ebp            /* pt_regs->bp */
        popl    %eax            /* pt_regs->ax */
        popl    %ds             /* pt_regs->ds (always ignores __dsh) */
        popl    %es             /* pt_regs->es (always ignores __esh) */
        popl    %fs             /* pt_regs->fs (always ignores __fsh) */
        popl    %gs             /* pt_regs->gs (always ignores __gsh) */
        decl    %ss:early_recursion_flag
        addl    $4, %esp        /* pop pt_regs->orig_ax */
        iret
SYM_CODE_END(early_idt_handler_common)

/* This is the default interrupt "handler" :-) */
SYM_FUNC_START(early_ignore_irq)
        cld
#ifdef CONFIG_PRINTK
        pushl %eax
        pushl %ecx
        pushl %edx
        pushl %es
        pushl %ds
        movl $(__KERNEL_DS),%eax
        movl %eax,%ds
        movl %eax,%es
        cmpl $2,early_recursion_flag
        je hlt_loop
        incl early_recursion_flag
        pushl 16(%esp)
        pushl 24(%esp)
        pushl 32(%esp)
        pushl 40(%esp)
        pushl $int_msg
        call _printk

        call dump_stack

        addl $(5*4),%esp
        popl %ds
        popl %es
        popl %edx
        popl %ecx
        popl %eax
#endif
        iret

hlt_loop:
        hlt
        jmp hlt_loop
SYM_FUNC_END(early_ignore_irq)

__INITDATA
        .align 4
SYM_DATA(early_recursion_flag, .long 0)

__REFDATA
        .align 4
SYM_DATA(initial_code,          .long i386_start_kernel)

#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
#define PGD_ALIGN       (2 * PAGE_SIZE)
#define PTI_USER_PGD_FILL       1024
#else
#define PGD_ALIGN       (PAGE_SIZE)
#define PTI_USER_PGD_FILL       0
#endif
/*
 * BSS section
 */
__PAGE_ALIGNED_BSS
        .align PGD_ALIGN
#ifdef CONFIG_X86_PAE
.globl initial_pg_pmd
initial_pg_pmd:
        .fill 1024*KPMDS,4,0
#else
.globl initial_page_table
initial_page_table:
        .fill 1024,4,0
#endif
        .align PGD_ALIGN
initial_pg_fixmap:
        .fill 1024,4,0
.globl swapper_pg_dir
        .align PGD_ALIGN
swapper_pg_dir:
        .fill 1024,4,0
        .fill PTI_USER_PGD_FILL,4,0
.globl empty_zero_page
empty_zero_page:
        .fill 4096,1,0
EXPORT_SYMBOL(empty_zero_page)

/*
 * This starts the data section.
 */
#ifdef CONFIG_X86_PAE
__PAGE_ALIGNED_DATA
        /* Page-aligned for the benefit of paravirt? */
        .align PGD_ALIGN
SYM_DATA_START(initial_page_table)
        .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0     /* low identity map */
# if KPMDS == 3
        .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
        .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
        .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
# elif KPMDS == 2
        .long   0,0
        .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
        .long   pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
# elif KPMDS == 1
        .long   0,0
        .long   0,0
        .long   pa(initial_pg_pmd+PGD_IDENT_ATTR),0
# else
#  error "Kernel PMDs should be 1, 2 or 3"
# endif
        .align PAGE_SIZE                /* needs to be page-sized too */

#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
        /*
         * PTI needs another page so sync_initial_pagetable() works correctly
         * and does not scribble over the data which is placed behind the
         * actual initial_page_table. See clone_pgd_range().
         */
        .fill 1024, 4, 0
#endif

SYM_DATA_END(initial_page_table)
#endif

.data
.balign 4
SYM_DATA(initial_stack, .long __top_init_kernel_stack)

__INITRODATA
int_msg:
        .asciz "Unknown interrupt or fault at: %p %p %p\n"

#include "../xen/xen-head.S"

/*
 * The IDT and GDT 'descriptors' are a strange 48-bit object
 * only used by the lidt and lgdt instructions. They are not
 * like usual segment descriptors - they consist of a 16-bit
 * segment size, and 32-bit linear address value:
 */

        .data
        ALIGN
# early boot GDT descriptor (must use 1:1 address mapping)
        .word 0                         # 32 bit align gdt_desc.address
SYM_DATA_START_LOCAL(boot_gdt_descr)
        .word __BOOT_DS+7
        .long boot_gdt - __PAGE_OFFSET
SYM_DATA_END(boot_gdt_descr)

# boot GDT descriptor (later on used by CPU#0):
        .word 0                         # 32 bit align gdt_desc.address
SYM_DATA_START(early_gdt_descr)
        .word GDT_ENTRIES*8-1
        .long gdt_page                  /* Overwritten for secondary CPUs */
SYM_DATA_END(early_gdt_descr)

/*
 * The boot_gdt must mirror the equivalent in setup.S and is
 * used only for booting.
 */
        .align L1_CACHE_BYTES
SYM_DATA_START(boot_gdt)
        .fill GDT_ENTRY_BOOT_CS,8,0
        .quad 0x00cf9a000000ffff        /* kernel 4GB code at 0x00000000 */
        .quad 0x00cf92000000ffff        /* kernel 4GB data at 0x00000000 */
SYM_DATA_END(boot_gdt)