qemu/pc-bios/s390-ccw/start.S

/*
 * First stage boot loader for virtio devices. The compiled output goes
 * into the pc-bios directory of qemu.
 *
 * Copyright (c) 2013 Alexander Graf <agraf@suse.de>
 * Copyright IBM Corp. 2013, 2017
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or (at
 * your option) any later version. See the COPYING file in the top-level
 * directory.
 */

#define STACK_SIZE        0x8000
#define STACK_FRAME_SIZE  160

    .globl _start
_start:

    larl    %r15,stack + STACK_SIZE - STACK_FRAME_SIZE   /* Set up stack */

    /* clear bss */
    larl    %r2,bss_start_literal   /* __bss_start might be unaligned ... */
    lg      %r2,0(%r2)              /* ... so load it indirectly */
    larl    %r3,_end
    slgr    %r3,%r2    /* get sizeof bss */
    ltgr    %r3,%r3    /* bss empty? */
    jz      done
    aghi    %r3,-1
    srlg    %r4,%r3,8  /* how many 256 byte chunks? */
    ltgr    %r4,%r4
    lgr     %r1,%r2
    jz      remainder
loop:
    xc      0(256,%r1),0(%r1)
    la      %r1,256(%r1)
    brctg   %r4,loop
remainder:
    larl    %r2,memsetxc
    ex      %r3,0(%r2)
done:
    /* set up a pgm exception disabled wait psw */
    larl    %r2,disabled_wait_psw
    mvc     0x01d0(16),0(%r2)
    j       main       /* And call C */

memsetxc:
    xc      0(1,%r1),0(%r1)

/*
 * void disabled_wait(void)
 *
 * stops the current guest cpu.
 */
    .globl disabled_wait
disabled_wait:
    larl    %r1,disabled_wait_psw
    lpswe   0(%r1)
1:  j       1b


/*
 * void consume_sclp_int(void)
 *
 * eats one sclp interrupt
 */
    .globl consume_sclp_int
consume_sclp_int:
    /* enable service interrupts in cr0 */
    stctg   %c0,%c0,0(%r15)
    oi      6(%r15),0x2
    lctlg   %c0,%c0,0(%r15)
    /* prepare external call handler */
    larl    %r1,external_new_code
    stg     %r1,0x1b8
    larl    %r1,external_new_mask
    mvc     0x1b0(8),0(%r1)
    /* load enabled wait PSW */
    larl    %r1,enabled_wait_psw
    lpswe   0(%r1)

/*
 * void consume_io_int(void)
 *
 * eats one I/O interrupt
 */
    .globl consume_io_int
consume_io_int:
    /* enable I/O interrupts in cr6 */
    stctg   %c6,%c6,0(%r15)
    oi      4(%r15), 0xff
    lctlg   %c6,%c6,0(%r15)
    /* prepare i/o call handler */
    larl    %r1,io_new_code
    stg     %r1,0x1f8
    larl    %r1,io_new_mask
    mvc     0x1f0(8),0(%r1)
    /* load enabled wait PSW */
    larl    %r1,enabled_wait_psw
    lpswe   0(%r1)

external_new_code:
    /* disable service interrupts in cr0 */
    stctg   %c0,%c0,0(%r15)
    ni      6(%r15),0xfd
    lctlg   %c0,%c0,0(%r15)
    br      %r14

io_new_code:
    /* disable I/O interrupts in cr6 */
    stctg   %c6,%c6,0(%r15)
    ni      4(%r15),0x00
    lctlg   %c6,%c6,0(%r15)
    br      %r14

    .align  8
bss_start_literal:
    .quad   __bss_start
disabled_wait_psw:
    .quad   0x0002000180000000,0x0000000000000000
enabled_wait_psw:
    .quad   0x0302000180000000,0x0000000000000000
external_new_mask:
    .quad   0x0000000180000000
io_new_mask:
    .quad   0x0000000180000000

.bss
    .align  8
stack:
    .space  STACK_SIZE
    .size   stack,STACK_SIZE