source: mainline/kernel/arch/ia32/src/asm.S@ 1558d85

/*
 * Copyright (c) 2010 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
 *
 */

#include <arch/pm.h>
#include <arch/cpu.h>
#include <arch/mm/page.h>
#include <arch/istate_struct.h>

.text
.global paging_on
.global enable_l_apic_in_msr
.global memcpy_from_uspace
.global memcpy_from_uspace_failover_address
.global memcpy_to_uspace
.global memcpy_to_uspace_failover_address
.global early_putchar

#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_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
        
        /* Copy whole words */
        rep movsl
        
        movl MEMCPY_SIZE(%esp), %ecx
        andl $3, %ecx  /* size % 4 */
        jz 0f
        
        /* Copy the rest byte by byte */
        rep movsb
        
        0:
        
                movl %edx, %edi
                movl %eax, %esi
                
                /* MEMCPY_DST(%esp), success */
                movl MEMCPY_DST(%esp), %eax
                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
        
        /* Return 0, failure */
        xorl %eax, %eax
        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

/*
 * Size of the istate structure without the hardware-saved part
 * and without the error word.
 */
#define ISTATE_SOFT_SIZE        ISTATE_SIZE - (6 * 4) 

/*
 * 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:

        /*
         * Note that the space needed for the istate structure has been
         * preallocated on the stack by before_thread_runs_arch().
         */

        /*
         * Save the return address and the userspace stack in the istate
         * structure on locations that would normally be taken by them.
         */
        movl %ebp, ISTATE_OFFSET_ESP(%esp)
        movl %edi, ISTATE_OFFSET_EIP(%esp)

        /*
         * Push syscall arguments onto the stack
         */
        movl %eax, ISTATE_OFFSET_EAX(%esp)
        movl %ebx, ISTATE_OFFSET_EBX(%esp)
        movl %ecx, ISTATE_OFFSET_ECX(%esp)
        movl %edx, ISTATE_OFFSET_EDX(%esp)
        movl %esi, ISTATE_OFFSET_ESI(%esp)
        movl %edi, ISTATE_OFFSET_EDI(%esp)      /* observability; not needed */
        movl %ebp, ISTATE_OFFSET_EBP(%esp)      /* observability; not needed */
        
        /*
         * Fake up the stack trace linkage.
         */
        movl %edi, ISTATE_OFFSET_EIP_FRAME(%esp)
        movl $0, ISTATE_OFFSET_EBP_FRAME(%esp)
        leal ISTATE_OFFSET_EBP_FRAME(%esp), %ebp

        /*
         * Save TLS.
         */
        movl %gs, %edx
        movl %edx, ISTATE_OFFSET_GS(%esp)

        /*
         * Switch to kernel selectors.
         */
        movw $(GDT_SELECTOR(KDATA_DES)), %ax
        movw %ax, %ds
        movw %ax, %es
        
        /*
         * Sanitize EFLAGS.
         *
         * SYSENTER does not clear the NT flag, which could thus proliferate
         * from here to the IRET instruction via a context switch and result
         * in crash.
         *
         * SYSENTER does not clear DF, which the ABI assumes to be cleared.
         *
         * SYSENTER clears IF, which we would like to be set for syscalls.
         *
         */
        pushl $(EFLAGS_IF)  /* specify EFLAGS bits that we want to set */
        popfl               /* set bits from the mask, clear or ignore others */

        call syscall_handler
        
        /*
         * Restore TLS.
         */
        movl ISTATE_OFFSET_GS(%esp), %edx
        movl %edx, %gs
        
        /*
         * Prepare return address and userspace stack for SYSEXIT.
         */
        movl ISTATE_OFFSET_EIP(%esp), %edx
        movl ISTATE_OFFSET_ESP(%esp), %ecx

        sysexit   /* return to userspace */

/*
 * This is the legacy syscall handler using the interrupt mechanism.
 */
.global int_syscall
int_syscall:
        subl $(ISTATE_SOFT_SIZE + 4), %esp

        /*
         * 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.
         *       The istate structure is arranged in the way to support
         *       this idea.
         *
         */
        movl %eax, ISTATE_OFFSET_EAX(%esp)
        movl %ebx, ISTATE_OFFSET_EBX(%esp)
        movl %ecx, ISTATE_OFFSET_ECX(%esp)
        movl %edx, ISTATE_OFFSET_EDX(%esp)
        movl %edi, ISTATE_OFFSET_EDI(%esp)
        movl %esi, ISTATE_OFFSET_ESI(%esp)
        movl %ebp, ISTATE_OFFSET_EBP(%esp)

        /*
         * Save the selector registers.
         */
        movl %gs, %ecx
        movl %fs, %edx

        movl %ecx, ISTATE_OFFSET_GS(%esp)
        movl %edx, ISTATE_OFFSET_FS(%esp)

        movl %es, %ecx
        movl %ds, %edx
                
        movl %ecx, ISTATE_OFFSET_ES(%esp)
        movl %edx, ISTATE_OFFSET_DS(%esp)

        /*
         * Switch to kernel selectors.
         */
        movl $(GDT_SELECTOR(KDATA_DES)), %eax
        movl %eax, %ds
        movl %eax, %es
                
        movl $0, ISTATE_OFFSET_EBP_FRAME(%esp)
        movl ISTATE_OFFSET_EIP(%esp), %eax
        movl %eax, ISTATE_OFFSET_EIP_FRAME(%esp)
        leal ISTATE_OFFSET_EBP_FRAME(%esp), %ebp
                
        cld
                
        /* Call syscall_handler(edx, ecx, ebx, esi, edi, ebp, eax) */
        call syscall_handler
                        
        /*
         * Restore the selector registers.
         */
        movl ISTATE_OFFSET_GS(%esp), %ecx
        movl ISTATE_OFFSET_FS(%esp), %edx

        movl %ecx, %gs
        movl %edx, %fs

        movl ISTATE_OFFSET_ES(%esp), %ecx
        movl ISTATE_OFFSET_DS(%esp), %edx
                        
        movl %ecx, %es
        movl %edx, %ds
                        
        /*
         * Restore the preserved registers the handler cloberred itself
         * (i.e. EBP).
         */
        movl ISTATE_OFFSET_EBP(%esp), %ebp
                        
        addl $(ISTATE_SOFT_SIZE + 4), %esp
        iret
                
/**
 * 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

.macro handler i
.global int_\i
int_\i:
        /*
         * 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
                        /*
                         * Exception with error word.
                         */
                        subl $ISTATE_SOFT_SIZE, %esp
                .else
                        /*
                         * Exception without error word: fake up one
                         */
                        subl $(ISTATE_SOFT_SIZE + 4), %esp
                .endif
        .else
                /*
                 * Interrupt: fake up an error word 
                 */
                subl $(ISTATE_SOFT_SIZE + 4), %esp
        .endif
        
        /*
         * Save the general purpose registers.
         */
        movl %eax, ISTATE_OFFSET_EAX(%esp)
        movl %ebx, ISTATE_OFFSET_EBX(%esp)
        movl %ecx, ISTATE_OFFSET_ECX(%esp)
        movl %edx, ISTATE_OFFSET_EDX(%esp)
        movl %edi, ISTATE_OFFSET_EDI(%esp)
        movl %esi, ISTATE_OFFSET_ESI(%esp)
        movl %ebp, ISTATE_OFFSET_EBP(%esp)
        
        /*
         * Save the selector registers.
         */
        movl %gs, %ecx
        movl %fs, %edx

        movl %ecx, ISTATE_OFFSET_GS(%esp)
        movl %edx, ISTATE_OFFSET_FS(%esp)

        movl %es, %ecx
        movl %ds, %edx
        
        movl %ecx, ISTATE_OFFSET_ES(%esp)
        movl %edx, ISTATE_OFFSET_DS(%esp)
        
        /*
         * Switch to kernel selectors.
         */
        movl $(GDT_SELECTOR(KDATA_DES)), %eax
        movl %eax, %ds
        movl %eax, %es
        
        /*
         * Imitate a regular stack frame linkage.
         * Stop stack traces here if we came from userspace.
         */
        xorl %eax, %eax
        cmpl $(GDT_SELECTOR(KTEXT_DES)), ISTATE_OFFSET_CS(%esp)
#ifdef PROCESSOR_i486
        jz 0f
                movl %eax, %ebp
        0:
#else
        cmovnzl %eax, %ebp
#endif

        movl %ebp, ISTATE_OFFSET_EBP_FRAME(%esp)
        movl ISTATE_OFFSET_EIP(%esp), %eax
        movl %eax, ISTATE_OFFSET_EIP_FRAME(%esp)
        leal ISTATE_OFFSET_EBP_FRAME(%esp), %ebp
                
        cld
                
        pushl %esp   /* pass istate address */
        pushl $(\i)  /* pass intnum */
                
        /* Call exc_dispatch(intnum, istate) */
        call exc_dispatch
                
        addl $8, %esp  /* clear arguments from the stack */
                
        /*
         * Restore the selector registers.
         */
        movl ISTATE_OFFSET_GS(%esp), %ecx
        movl ISTATE_OFFSET_FS(%esp), %edx

        movl %ecx, %gs
        movl %edx, %fs

        movl ISTATE_OFFSET_ES(%esp), %ecx
        movl ISTATE_OFFSET_DS(%esp), %edx
                
        movl %ecx, %es
        movl %edx, %ds
                
        /*
         * Restore the scratch registers and the preserved
         * registers the handler cloberred itself
         * (i.e. EBP).
         */
        movl ISTATE_OFFSET_EAX(%esp), %eax
        movl ISTATE_OFFSET_ECX(%esp), %ecx
        movl ISTATE_OFFSET_EDX(%esp), %edx
        movl ISTATE_OFFSET_EBP(%esp), %ebp
                
        addl $(ISTATE_SOFT_SIZE + 4), %esp
        iret
.endm

#define LIST_0_63 \
        0, 1, 2, 3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,\
        28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,\
        53,54,55,56,57,58,59,60,61,62,63

interrupt_handlers:
.irp cnt, LIST_0_63 
        handler \cnt
.endr

/** Print Unicode character to EGA display.
 *
 * If CONFIG_EGA is undefined or CONFIG_FB is defined
 * then this function does nothing.
 *
 * Since the EGA can only display Extended ASCII (usually
 * ISO Latin 1) characters, some of the Unicode characters
 * can be displayed in a wrong way. Only newline and backspace
 * are interpreted, all other characters (even unprintable) are
 * printed verbatim.
 *
 * @param %ebp+0x08 Unicode character to be printed.
 *
 */
early_putchar:
        
#if ((defined(CONFIG_EGA)) && (!defined(CONFIG_FB)))
        
        /* Prologue, save preserved registers */
        pushl %ebp
        movl %esp, %ebp
        pushl %ebx
        pushl %esi
        pushl %edi
        
        movl $(PA2KA(0xb8000)), %edi  /* base of EGA text mode memory */
        xorl %eax, %eax
        
        /* Read bits 8 - 15 of the cursor address */
        movw $0x3d4, %dx
        movb $0xe, %al
        outb %al, %dx
        
        movw $0x3d5, %dx
        inb %dx, %al
        shl $8, %ax
        
        /* Read bits 0 - 7 of the cursor address */
        movw $0x3d4, %dx
        movb $0xf, %al
        outb %al, %dx
        
        movw $0x3d5, %dx
        inb %dx, %al
        
        /* Sanity check for the cursor on screen */
        cmp $2000, %ax
        jb early_putchar_cursor_ok
        
                movw $1998, %ax
        
        early_putchar_cursor_ok:
        
        movw %ax, %bx
        shl $1, %eax
        addl %eax, %edi
        
        movl 0x08(%ebp), %eax
        
        cmp $0x0a, %al
        jne early_putchar_backspace
        
                /* Interpret newline */
                
                movw %bx, %ax  /* %bx -> %dx:%ax */
                xorw %dx, %dx
                
                movw $80, %cx
                idivw %cx, %ax  /* %dx = %bx % 80 */
                
                /* %bx <- %bx + 80 - (%bx % 80) */
                addw %cx, %bx
                subw %dx, %bx
                
                jmp early_putchar_skip
        
        early_putchar_backspace:
        
                cmp $0x08, %al
                jne early_putchar_print
                
                /* Interpret backspace */
                
                cmp $0x0000, %bx
                je early_putchar_skip
                
                dec %bx
                jmp early_putchar_skip
        
        early_putchar_print:
        
                /* Print character */
                
                movb $0x0e, %ah  /* black background, yellow foreground */
                stosw
                inc %bx
        
        early_putchar_skip:
        
        /* Sanity check for the cursor on the last line */
        cmp $2000, %bx
        jb early_putchar_no_scroll
        
                /* Scroll the screen (24 rows) */
                movl $(PA2KA(0xb80a0)), %esi
                movl $(PA2KA(0xb8000)), %edi
                movl $960, %ecx
                rep movsl
                
                /* Clear the 24th row */
                xorl %eax, %eax
                movl $40, %ecx
                rep stosl
                
                /* Go to row 24 */
                movw $1920, %bx
        
        early_putchar_no_scroll:
        
        /* Write bits 8 - 15 of the cursor address */
        movw $0x3d4, %dx
        movb $0xe, %al
        outb %al, %dx
        
        movw $0x3d5, %dx
        movb %bh, %al
        outb %al, %dx
        
        /* Write bits 0 - 7 of the cursor address */
        movw $0x3d4, %dx
        movb $0xf, %al
        outb %al, %dx
        
        movw $0x3d5, %dx
        movb %bl, %al
        outb %al, %dx
        
        /* Epilogue, restore preserved registers */
        popl %edi
        popl %esi
        popl %ebx
        leave
        
#endif
        
        ret