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#
# Copyright (c) 2001-2004 Jakub Jermar
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright
#   notice, this list of conditions and the following disclaimer in the
#   documentation and/or other materials provided with the distribution.
# - The name of the author may not be used to endorse or promote products
#   derived from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#

## very low and hardware-level functions

# Mask for interrupts 0 - 31 (bits 0 - 31) where 0 means that int has no error
# word and 1 means interrupt with error word
#define ERROR_WORD_INTERRUPT_LIST 0x00027d00

.text

.global paging_on
.global enable_l_apic_in_msr
.global interrupt_handlers
.global memsetb
.global memsetw
.global memcpy
.global memcpy_from_uspace
.global memcpy_from_uspace_failover_address
.global memcpy_to_uspace
.global memcpy_to_uspace_failover_address


# Wrapper for generic memsetb
memsetb:
    jmp _memsetb

# Wrapper for generic memsetw
memsetw:
    jmp _memsetw


#define MEMCPY_DST  4
#define MEMCPY_SRC  8
#define MEMCPY_SIZE 12

/** Copy memory to/from userspace.
 *
 * This is almost conventional memcpy().
 * The difference is that there is a failover part
 * to where control is returned from a page fault
 * if the page fault occurs during copy_from_uspace()
 * or copy_to_uspace().
 *
 * @param MEMCPY_DST(%esp)  Destination address.
 * @param MEMCPY_SRC(%esp)  Source address.
 * @param MEMCPY_SIZE(%esp) Size.
 *
 * @return MEMCPY_DST(%esp) on success and 0 on failure.
 */
memcpy:
memcpy_from_uspace:
memcpy_to_uspace:
    movl %edi, %edx         /* save %edi */
    movl %esi, %eax         /* save %esi */
    
    movl MEMCPY_SIZE(%esp), %ecx
    shrl $2, %ecx           /* size / 4 */
    
    movl MEMCPY_DST(%esp), %edi
    movl MEMCPY_SRC(%esp), %esi
    
    rep movsl           /* copy whole words */

    movl MEMCPY_SIZE(%esp), %ecx
    andl $3, %ecx           /* size % 4 */
    jz 0f
    
    rep movsb           /* copy the rest byte by byte */

0:
    movl %edx, %edi
    movl %eax, %esi
    movl MEMCPY_DST(%esp), %eax /* MEMCPY_DST(%esp), success */
    ret
    
/*
 * We got here from as_page_fault() after the memory operations
 * above had caused a page fault.
 */
memcpy_from_uspace_failover_address:
memcpy_to_uspace_failover_address:
    movl %edx, %edi
    movl %eax, %esi
    xorl %eax, %eax         /* return 0, failure */
    ret

## Turn paging on
#
# Enable paging and write-back caching in CR0.
#
paging_on:
    movl %cr0, %edx
    orl $(1 << 31), %edx        # paging on
    # clear Cache Disable and not Write Though
    andl $~((1 << 30) | (1 << 29)), %edx
    movl %edx,%cr0
    jmp 0f
0:
    ret


## Enable local APIC
#
# Enable local APIC in MSR.
#
enable_l_apic_in_msr:
    movl $0x1b, %ecx
    rdmsr
    orl $(1 << 11), %eax
    orl $(0xfee00000), %eax
    wrmsr
    ret

# Clear nested flag
# overwrites %ecx
.macro CLEAR_NT_FLAG
    pushfl
    pop %ecx
    and $0xffffbfff, %ecx
    push %ecx
    popfl
.endm   

/*
 * The SYSENTER syscall mechanism can be used for syscalls with
 * four or fewer arguments. To pass these four arguments, we
 * use four registers: EDX, ECX, EBX, ESI. The syscall number
 * is passed in EAX. We use EDI to remember the return address
 * and EBP to remember the stack. The INT-based syscall mechanism
 * can actually handle six arguments plus the syscall number
 * entirely in registers.
 */
.global sysenter_handler
sysenter_handler:
    pushl %ebp  # remember user stack
    pushl %edi  # remember return user address

    pushl %gs   # remember TLS

    pushl %eax  # syscall number
    subl $8, %esp   # unused sixth and fifth argument
    pushl %esi  # fourth argument
    pushl %ebx  # third argument
    pushl %ecx  # second argument
    pushl %edx  # first argument

    movw $16, %ax
    movw %ax, %ds
    movw %ax, %es

    cld
    call syscall_handler
    addl $28, %esp  # remove arguments from stack

    pop %gs     # restore TLS

    pop %edx    # prepare return EIP for SYSEXIT
    pop %ecx    # prepare userspace ESP for SYSEXIT

    sysexit     # return to userspace


## Declare interrupt handlers
#
# Declare interrupt handlers for n interrupt
# vectors starting at vector i.
#
# The handlers setup data segment registers
# and call exc_dispatch().
#
#define INTERRUPT_ALIGN 64
.macro handler i n

.ifeq \i - 0x30     # Syscall handler
    pushl %ds
    pushl %es
    pushl %fs
    pushl %gs

    #
    # Push syscall arguments onto the stack
    #
    # NOTE: The idea behind the order of arguments passed in registers is to
    #   use all scratch registers first and preserved registers next.
    #   An optimized libc syscall wrapper can make use of this setup.
    #
    pushl %eax
    pushl %ebp
    pushl %edi
    pushl %esi
    pushl %ebx
    pushl %ecx
    pushl %edx
    
    # we must fill the data segment registers
    movw $16, %ax
    movw %ax, %ds
    movw %ax, %es
    
    cld
    sti
    # syscall_handler(edx, ecx, ebx, esi, edi, ebp, eax)
    call syscall_handler   
    cli
    addl $28, %esp         # clean-up of parameters
    
    popl %gs
    popl %fs
    popl %es
    popl %ds
    
    CLEAR_NT_FLAG
    iret
.else   
    /*
     * This macro distinguishes between two versions of ia32 exceptions.
     * One version has error word and the other does not have it.
     * The latter version fakes the error word on the stack so that the
     * handlers and istate_t can be the same for both types.
     */
    .iflt \i - 32
        .if (1 << \i) & ERROR_WORD_INTERRUPT_LIST
            /* 
             * With error word, do nothing
             */
                .else
                        /*
                         * Version without error word,
                         */
            subl $4, %esp
                .endif
        .else
                /*
                 * Version without error word,
                 */
        subl $4, %esp
    .endif
    
    pushl %ds
    pushl %es
    pushl %fs
    pushl %gs

#ifdef CONFIG_DEBUG_ALLREGS
    pushl %ebx
    pushl %ebp
    pushl %edi
    pushl %esi
#else
    subl $16, %esp
#endif
    pushl %edx
    pushl %ecx
    pushl %eax
    
    # we must fill the data segment registers
    movw $16, %ax
    movw %ax, %ds
    movw %ax, %es

    cld

    pushl %esp          # *istate
    pushl $(\i)         # intnum
    call exc_dispatch   # excdispatch(intnum, *istate)
    addl $8, %esp       # Clear arguments from stack

    CLEAR_NT_FLAG # Modifies %ecx
    
    popl %eax
    popl %ecx
    popl %edx
#ifdef CONFIG_DEBUG_ALLREGS
    popl %esi
    popl %edi
    popl %ebp
    popl %ebx
#else
    addl $16, %esp
#endif  
    
    popl %gs
    popl %fs
    popl %es
    popl %ds

    addl $4, %esp   # Skip error word, no matter whether real or fake.
    iret
.endif

    .align INTERRUPT_ALIGN
    .if (\n- \i) - 1
    handler "(\i + 1)", \n
    .endif
.endm

# keep in sync with pm.h !!!
IDT_ITEMS = 64
.align INTERRUPT_ALIGN
interrupt_handlers:
h_start:
    handler 0 IDT_ITEMS
h_end:

.data
.global interrupt_handler_size

interrupt_handler_size: .long (h_end - h_start) / IDT_ITEMS