source: mainline/kernel/arch/amd64/src/asm.S@ 3da166f0

/*
 * Copyright (c) 2005 Ondrej Palkovsky
 * 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.
 */

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

.text
.global interrupt_handlers
.global syscall_entry
.global cpuid
.global has_cpuid
.global read_efer_flag
.global set_efer_flag
.global memcpy_from_uspace
.global memcpy_to_uspace
.global memcpy_from_uspace_failover_address
.global memcpy_to_uspace_failover_address
.global early_putchar

#define MEMCPY_DST   %rdi
#define MEMCPY_SRC   %rsi
#define MEMCPY_SIZE  %rdx

/**
 * Copy memory from/to 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  Destination address.
 * @param MEMCPY_SRC  Source address.
 * @param MEMCPY_SIZE Number of bytes to copy.
 *
 * @retrun MEMCPY_DST on success, 0 on failure.
 *
 */
memcpy_from_uspace:
memcpy_to_uspace:
        movq MEMCPY_DST, %rax
        
        movq MEMCPY_SIZE, %rcx
        shrq $3, %rcx           /* size / 8 */
        
        rep movsq               /* copy as much as possible word by word */
        
        movq MEMCPY_SIZE, %rcx
        andq $7, %rcx           /* size % 8 */
        jz 0f
        
        rep movsb               /* copy the rest byte by byte */
        
        0:
                ret                 /* return MEMCPY_SRC, success */

memcpy_from_uspace_failover_address:
memcpy_to_uspace_failover_address:
        xorl %eax, %eax         /* return 0, failure */
        ret

/** Determine CPUID support
*
* @return 0 in EAX if CPUID is not support, 1 if supported.
*
*/
has_cpuid:
        /* Load RFLAGS */
        pushfq
        popq %rax
        movq %rax, %rdx
        
        /* Flip the ID bit */
        btcl $21, %edx
        
        /* Store RFLAGS */
        pushq %rdx
        popfq
        pushfq
        
        /* Get the ID bit again */
        popq %rdx
        andl $(1 << 21), %eax
        andl $(1 << 21), %edx
        
        /* 0 if not supported, 1 if supported */
        xorl %edx, %eax
        ret

cpuid:
        /* Preserve %rbx across function calls */
        movq %rbx, %r10
        
        /* Load the command into %eax */
        movl %edi, %eax
        
        cpuid
        movl %eax, 0(%rsi)
        movl %ebx, 4(%rsi)
        movl %ecx, 8(%rsi)
        movl %edx, 12(%rsi)
        
        movq %r10, %rbx
        ret

set_efer_flag:
        movl $0xc0000080, %ecx
        rdmsr
        btsl %edi, %eax
        wrmsr
        ret

read_efer_flag:
        movl $0xc0000080, %ecx
        rdmsr
        ret

/*
 * Size of the istate structure without the hardware-saved part and without the
 * error word.
 */
#define ISTATE_SOFT_SIZE        ISTATE_SIZE - (6 * 8)

/**
 * 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:

        /*
         * Choose between version with error code and version without error
         * code.
         */
        
        .iflt \i-32
                .if (1 << \i) & ERROR_WORD_INTERRUPT_LIST
                        /*
                         * Version with error word.
                         */
                        subq $ISTATE_SOFT_SIZE, %rsp
                .else
                        /*
                         * Version without error word.
                         */
                        subq $(ISTATE_SOFT_SIZE + 8), %rsp
                .endif
        .else
                /*
                 * Version without error word.
                 */
                subq $(ISTATE_SOFT_SIZE + 8), %rsp
        .endif
        
        /*
         * Save the general purpose registers.
         */
        movq %rax, ISTATE_OFFSET_RAX(%rsp)
        movq %rbx, ISTATE_OFFSET_RBX(%rsp)
        movq %rcx, ISTATE_OFFSET_RCX(%rsp)
        movq %rdx, ISTATE_OFFSET_RDX(%rsp)
        movq %rsi, ISTATE_OFFSET_RSI(%rsp)
        movq %rdi, ISTATE_OFFSET_RDI(%rsp)
        movq %rbp, ISTATE_OFFSET_RBP(%rsp)
        movq %r8, ISTATE_OFFSET_R8(%rsp)
        movq %r9, ISTATE_OFFSET_R9(%rsp)
        movq %r10, ISTATE_OFFSET_R10(%rsp)
        movq %r11, ISTATE_OFFSET_R11(%rsp)
        movq %r12, ISTATE_OFFSET_R12(%rsp)
        movq %r13, ISTATE_OFFSET_R13(%rsp)
        movq %r14, ISTATE_OFFSET_R14(%rsp)
        movq %r15, ISTATE_OFFSET_R15(%rsp)

        /*
         * Imitate a regular stack frame linkage.
         * Stop stack traces here if we came from userspace.
         */
        xorl %edx, %edx
        cmpq $(GDT_SELECTOR(KTEXT_DES)), ISTATE_OFFSET_CS(%rsp)
        cmovnzq %rdx, %rbp

        movq %rbp, ISTATE_OFFSET_RBP_FRAME(%rsp)
        movq ISTATE_OFFSET_RIP(%rsp), %rax
        movq %rax, ISTATE_OFFSET_RIP_FRAME(%rsp)
        leaq ISTATE_OFFSET_RBP_FRAME(%rsp), %rbp

        movq $(\i), %rdi   /* pass intnum in the first argument */
        movq %rsp, %rsi    /* pass istate address in the second argument */
        
        cld

        /* Call exc_dispatch(i, istate) */
        call exc_dispatch

        /*
         * Restore all scratch registers and the preserved registers we have
         * clobbered in this handler (i.e. RBP).
         */
        movq ISTATE_OFFSET_RAX(%rsp), %rax
        movq ISTATE_OFFSET_RCX(%rsp), %rcx
        movq ISTATE_OFFSET_RDX(%rsp), %rdx
        movq ISTATE_OFFSET_RSI(%rsp), %rsi
        movq ISTATE_OFFSET_RDI(%rsp), %rdi
        movq ISTATE_OFFSET_RBP(%rsp), %rbp
        movq ISTATE_OFFSET_R8(%rsp), %r8
        movq ISTATE_OFFSET_R9(%rsp), %r9
        movq ISTATE_OFFSET_R10(%rsp), %r10
        movq ISTATE_OFFSET_R11(%rsp), %r11
        
        /* $8 = Skip error word */
        addq $(ISTATE_SOFT_SIZE + 8), %rsp
        iretq
.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

/** Low-level syscall handler
 *
 * Registers on entry:
 *
 * @param %rcx Userspace return address.
 * @param %r11 Userspace RLFAGS.
 *
 * @param %rax Syscall number.
 * @param %rdi 1st syscall argument.
 * @param %rsi 2nd syscall argument.
 * @param %rdx 3rd syscall argument.
 * @param %r10 4th syscall argument. Used instead of RCX because
 *             the SYSCALL instruction clobbers it.
 * @param %r8  5th syscall argument.
 * @param %r9  6th syscall argument.
 *
 * @return Return value is in %rax.
 *
 */
syscall_entry:
        /* Switch to hidden %gs */
        swapgs
        
        /*
         * %gs:0 Scratch space for this thread's user RSP
         * %gs:8 Address to be used as this thread's kernel RSP
         */
        
        movq %rsp, %gs:0  /* save this thread's user RSP */
        movq %gs:8, %rsp  /* set this thread's kernel RSP */
        
        /*
         * Note that the space needed for the imitated istate structure has been
         * preallocated for us in thread_create_arch() and set in
         * before_thread_runs_arch().
         */

        /*
         * Save the general purpose registers and push the 7th argument (syscall
         * number) onto the stack. Note that the istate structure has a layout
         * which supports this.
         */
        movq %rax, ISTATE_OFFSET_RAX(%rsp)  /* 7th argument, passed on stack */
        movq %rbx, ISTATE_OFFSET_RBX(%rsp)  /* observability */
        movq %rcx, ISTATE_OFFSET_RCX(%rsp)  /* userspace RIP */
        movq %rdx, ISTATE_OFFSET_RDX(%rsp)  /* 3rd argument, observability */
        movq %rsi, ISTATE_OFFSET_RSI(%rsp)  /* 2nd argument, observability */ 
        movq %rdi, ISTATE_OFFSET_RDI(%rsp)  /* 1st argument, observability */
        movq %rbp, ISTATE_OFFSET_RBP(%rsp)  /* need to preserve userspace RBP */
        movq %r8, ISTATE_OFFSET_R8(%rsp)    /* 5th argument, observability */
        movq %r9, ISTATE_OFFSET_R9(%rsp)    /* 6th argument, observability */
        movq %r10, ISTATE_OFFSET_R10(%rsp)  /* 4th argument, observability */
        movq %r11, ISTATE_OFFSET_R11(%rsp)  /* low 32 bits userspace RFLAGS */
        movq %r12, ISTATE_OFFSET_R12(%rsp)  /* observability */
        movq %r13, ISTATE_OFFSET_R13(%rsp)  /* observability */
        movq %r14, ISTATE_OFFSET_R14(%rsp)  /* observability */
        movq %r15, ISTATE_OFFSET_R15(%rsp)  /* observability */

        /*
         * Save the return address and the userspace stack on locations that
         * would normally be taken by them.
         */
        movq %gs:0, %rax
        movq %rax, ISTATE_OFFSET_RSP(%rsp)
        movq %rcx, ISTATE_OFFSET_RIP(%rsp)

        /*
         * Imitate a regular stack frame linkage.
         */
        movq $0, ISTATE_OFFSET_RBP_FRAME(%rsp)
        movq %rcx, ISTATE_OFFSET_RIP_FRAME(%rsp)
        leaq ISTATE_OFFSET_RBP_FRAME(%rsp), %rbp

        /* Switch back to normal %gs */
        swapgs
        sti
        
        /* Copy the 4th argument where it is expected  */
        movq %r10, %rcx

        /*
         * Call syscall_handler() with the 7th argument passed on stack.
         */
        call syscall_handler

        /*
         * Test if the saved return address is canonical and not-kernel.
         * We do this by looking at the 16 most significant bits
         * of the saved return address (two bytes at offset 6).
         */
        testw $0xffff, ISTATE_OFFSET_RIP+6(%rsp)
        jnz bad_rip 

        cli
        
        /*
         * Restore registers needed for return via the SYSRET instruction and
         * the clobbered preserved registers (i.e. RBP).
         */
        movq ISTATE_OFFSET_RBP(%rsp), %rbp
        movq ISTATE_OFFSET_RCX(%rsp), %rcx
        movq ISTATE_OFFSET_R11(%rsp), %r11
        movq ISTATE_OFFSET_RSP(%rsp), %rsp

        /*
         * Clear the rest of the scratch registers to prevent information leak.
         * The 32-bit XOR on the low GPRs actually clears the entire 64-bit
         * register and the instruction is shorter.
         */
        xorl %edx, %edx
        xorl %esi, %esi
        xorl %edi, %edi
        xorq %r8, %r8
        xorq %r9, %r9
        xorq %r10, %r10

        sysretq

bad_rip:
        movq %rsp, %rdi
        movabs $bad_rip_msg, %rsi
        xorb %al, %al
        callq fault_from_uspace
        /* not reached */
        
bad_rip_msg:
        .asciz "Invalid instruction pointer."

/** 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 %rdi Unicode character to be printed.
 *
 */
early_putchar:
        
#if ((defined(CONFIG_EGA)) && (!defined(CONFIG_FB)))
        
        /* Prologue, save preserved registers */
        pushq %rbp
        movq %rsp, %rbp
        pushq %rbx
        
        movq %rdi, %rsi
        movq $(PA2KA(0xb8000)), %rdi  /* 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, %rax
        addq %rax, %rdi
        
        movq %rsi, %rax
        
        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) */
                movq $(PA2KA(0xb80a0)), %rsi
                movq $(PA2KA(0xb8000)), %rdi
                movl $480, %ecx
                rep movsq
                
                /* Clear the 24th row */
                xorl %eax, %eax
                movl $20, %ecx
                rep stosq
                
                /* 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 */
        popq %rbx
        leave
        
#endif
        
        ret