// SPDX-License-Identifier: GPL-2.0
/*
 * arch/alpha/boot/bootp.c
 *
 * Copyright (C) 1997 Jay Estabrook
 *
 * This file is used for creating a bootp file for the Linux/AXP kernel
 *
 * based significantly on the arch/alpha/boot/main.c of Linus Torvalds
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <generated/utsrelease.h>
#include <linux/mm.h>

#include <asm/console.h>
#include <asm/hwrpb.h>
#include <asm/io.h>

#include <linux/stdarg.h>

#include "ksize.h"

extern unsigned long switch_to_osf_pal(unsigned long nr,
        struct pcb_struct *pcb_va, struct pcb_struct *pcb_pa,
        unsigned long *vptb);

extern void move_stack(unsigned long new_stack);

struct hwrpb_struct *hwrpb = INIT_HWRPB;
static struct pcb_struct pcb_va[1];

/*
 * Find a physical address of a virtual object..
 *
 * This is easy using the virtual page table address.
 */

static inline void *
find_pa(unsigned long *vptb, void *ptr)
{
        unsigned long address = (unsigned long) ptr;
        unsigned long result;

        result = vptb[address >> 13];
        result >>= 32;
        result <<= 13;
        result |= address & 0x1fff;
        return (void *) result;
}       

/*
 * This function moves into OSF/1 pal-code, and has a temporary
 * PCB for that. The kernel proper should replace this PCB with
 * the real one as soon as possible.
 *
 * The page table muckery in here depends on the fact that the boot
 * code has the L1 page table identity-map itself in the second PTE
 * in the L1 page table. Thus the L1-page is virtually addressable
 * itself (through three levels) at virtual address 0x200802000.
 */

#define VPTB    ((unsigned long *) 0x200000000)
#define L1      ((unsigned long *) 0x200802000)

void
pal_init(void)
{
        unsigned long i, rev;
        struct percpu_struct * percpu;
        struct pcb_struct * pcb_pa;

        /* Create the dummy PCB.  */
        pcb_va->ksp = 0;
        pcb_va->usp = 0;
        pcb_va->ptbr = L1[1] >> 32;
        pcb_va->asn = 0;
        pcb_va->pcc = 0;
        pcb_va->unique = 0;
        pcb_va->flags = 1;
        pcb_va->res1 = 0;
        pcb_va->res2 = 0;
        pcb_pa = find_pa(VPTB, pcb_va);

        /*
         * a0 = 2 (OSF)
         * a1 = return address, but we give the asm the vaddr of the PCB
         * a2 = physical addr of PCB
         * a3 = new virtual page table pointer
         * a4 = KSP (but the asm sets it)
         */
        srm_printk("Switching to OSF PAL-code .. ");

        i = switch_to_osf_pal(2, pcb_va, pcb_pa, VPTB);
        if (i) {
                srm_printk("failed, code %ld\n", i);
                __halt();
        }

        percpu = (struct percpu_struct *)
                (INIT_HWRPB->processor_offset + (unsigned long) INIT_HWRPB);
        rev = percpu->pal_revision = percpu->palcode_avail[2];

        srm_printk("Ok (rev %lx)\n", rev);

        tbia(); /* do it directly in case we are SMP */
}

static inline void
load(unsigned long dst, unsigned long src, unsigned long count)
{
        memcpy((void *)dst, (void *)src, count);
}

/*
 * Start the kernel.
 */
static inline void
runkernel(void)
{
        __asm__ __volatile__(
                "bis %0,%0,$27\n\t"
                "jmp ($27)"
                : /* no outputs: it doesn't even return */
                : "r" (START_ADDR));
}

extern char _end;
#define KERNEL_ORIGIN \
        ((((unsigned long)&_end) + 511) & ~511)

void
start_kernel(void)
{
        /*
         * Note that this crufty stuff with static and envval
         * and envbuf is because:
         *
         * 1. Frequently, the stack is short, and we don't want to overrun;
         * 2. Frequently the stack is where we are going to copy the kernel to;
         * 3. A certain SRM console required the GET_ENV output to stack.
         *    ??? A comment in the aboot sources indicates that the GET_ENV
         *    destination must be quadword aligned.  Might this explain the
         *    behaviour, rather than requiring output to the stack, which
         *    seems rather far-fetched.
         */
        static long nbytes;
        static char envval[256] __attribute__((aligned(8)));
        static unsigned long initrd_start;

        srm_printk("Linux/AXP bootp loader for Linux " UTS_RELEASE "\n");
        if (INIT_HWRPB->pagesize != 8192) {
                srm_printk("Expected 8kB pages, got %ldkB\n",
                           INIT_HWRPB->pagesize >> 10);
                return;
        }
        if (INIT_HWRPB->vptb != (unsigned long) VPTB) {
                srm_printk("Expected vptb at %p, got %p\n",
                           VPTB, (void *)INIT_HWRPB->vptb);
                return;
        }
        pal_init();

        /* The initrd must be page-aligned.  See below for the 
           cause of the magic number 5.  */
        initrd_start = ((START_ADDR + 5*KERNEL_SIZE + PAGE_SIZE) |
                        (PAGE_SIZE-1)) + 1;
#ifdef INITRD_IMAGE_SIZE
        srm_printk("Initrd positioned at %#lx\n", initrd_start);
#endif

        /*
         * Move the stack to a safe place to ensure it won't be
         * overwritten by kernel image.
         */
        move_stack(initrd_start - PAGE_SIZE);

        nbytes = callback_getenv(ENV_BOOTED_OSFLAGS, envval, sizeof(envval));
        if (nbytes < 0 || nbytes >= sizeof(envval)) {
                nbytes = 0;
        }
        envval[nbytes] = '\0';
        srm_printk("Loading the kernel...'%s'\n", envval);

        /* NOTE: *no* callbacks or printouts from here on out!!! */

        /* This is a hack, as some consoles seem to get virtual 20000000 (ie
         * where the SRM console puts the kernel bootp image) memory
         * overlapping physical memory where the kernel wants to be put,
         * which causes real problems when attempting to copy the former to
         * the latter... :-(
         *
         * So, we first move the kernel virtual-to-physical way above where
         * we physically want the kernel to end up, then copy it from there
         * to its final resting place... ;-}
         *
         * Sigh...  */

#ifdef INITRD_IMAGE_SIZE
        load(initrd_start, KERNEL_ORIGIN+KERNEL_SIZE, INITRD_IMAGE_SIZE);
#endif
        load(START_ADDR+(4*KERNEL_SIZE), KERNEL_ORIGIN, KERNEL_SIZE);
        load(START_ADDR, START_ADDR+(4*KERNEL_SIZE), KERNEL_SIZE);

        memset((char*)ZERO_PGE, 0, PAGE_SIZE);
        strcpy((char*)ZERO_PGE, envval);
#ifdef INITRD_IMAGE_SIZE
        ((long *)(ZERO_PGE+256))[0] = initrd_start;
        ((long *)(ZERO_PGE+256))[1] = INITRD_IMAGE_SIZE;
#endif

        runkernel();
}