// SPDX-License-Identifier: GPL-2.0
/*
 *    Hypervisor filesystem for Linux on s390. z/VM implementation.
 *
 *    Copyright IBM Corp. 2006
 *    Author(s): Michael Holzheu <holzheu@de.ibm.com>
 */

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <asm/extable.h>
#include <asm/machine.h>
#include <asm/diag.h>
#include <asm/ebcdic.h>
#include <asm/timex.h>
#include "hypfs_vm.h"
#include "hypfs.h"

#define DBFS_D2FC_HDR_VERSION 0

static char local_guest[] = "        ";
static char all_guests[] = "*       ";
static char *all_groups = all_guests;
char *diag2fc_guest_query;

static int diag2fc(int size, char* query, void *addr)
{
        unsigned long residual_cnt;
        unsigned long rc;
        struct diag2fc_parm_list parm_list;

        memcpy(parm_list.userid, query, DIAG2FC_NAME_LEN);
        ASCEBC(parm_list.userid, DIAG2FC_NAME_LEN);
        memcpy(parm_list.aci_grp, all_groups, DIAG2FC_NAME_LEN);
        ASCEBC(parm_list.aci_grp, DIAG2FC_NAME_LEN);
        parm_list.addr = (unsigned long)addr;
        parm_list.size = size;
        parm_list.fmt = 0x02;
        rc = -1;

        diag_stat_inc(DIAG_STAT_X2FC);
        asm volatile(
                "       diag    %0,%1,0x2fc\n"
                "0:     nopr    %%r7\n"
                EX_TABLE(0b,0b)
                : "=d" (residual_cnt), "+d" (rc) : "0" (&parm_list) : "memory");

        if ((rc != 0 ) && (rc != -2))
                return rc;
        else
                return -residual_cnt;
}

/*
 * Allocate buffer for "query" and store diag 2fc at "offset"
 */
void *diag2fc_store(char *query, unsigned int *count, int offset)
{
        void *data;
        int size;

        do {
                size = diag2fc(0, query, NULL);
                if (size < 0)
                        return ERR_PTR(-EACCES);
                data = vmalloc(size + offset);
                if (!data)
                        return ERR_PTR(-ENOMEM);
                if (diag2fc(size, query, data + offset) == 0)
                        break;
                vfree(data);
        } while (1);
        *count = (size / sizeof(struct diag2fc_data));

        return data;
}

void diag2fc_free(const void *data)
{
        vfree(data);
}

struct dbfs_d2fc_hdr {
        u64     len;            /* Length of d2fc buffer without header */
        u16     version;        /* Version of header */
        union tod_clock tod_ext; /* TOD clock for d2fc */
        u64     count;          /* Number of VM guests in d2fc buffer */
        char    reserved[30];
} __attribute__ ((packed));

struct dbfs_d2fc {
        struct dbfs_d2fc_hdr    hdr;    /* 64 byte header */
        char                    buf[];  /* d2fc buffer */
} __attribute__ ((packed));

static int dbfs_diag2fc_create(void **data, void **data_free_ptr, size_t *size)
{
        struct dbfs_d2fc *d2fc;
        unsigned int count;

        d2fc = diag2fc_store(diag2fc_guest_query, &count, sizeof(d2fc->hdr));
        if (IS_ERR(d2fc))
                return PTR_ERR(d2fc);
        store_tod_clock_ext(&d2fc->hdr.tod_ext);
        d2fc->hdr.len = count * sizeof(struct diag2fc_data);
        d2fc->hdr.version = DBFS_D2FC_HDR_VERSION;
        d2fc->hdr.count = count;
        memset(&d2fc->hdr.reserved, 0, sizeof(d2fc->hdr.reserved));
        *data = d2fc;
        *data_free_ptr = d2fc;
        *size = d2fc->hdr.len + sizeof(struct dbfs_d2fc_hdr);
        return 0;
}

static struct hypfs_dbfs_file dbfs_file_2fc = {
        .name           = "diag_2fc",
        .data_create    = dbfs_diag2fc_create,
        .data_free      = diag2fc_free,
};

int hypfs_vm_init(void)
{
        if (!machine_is_vm())
                return 0;
        if (diag2fc(0, all_guests, NULL) > 0)
                diag2fc_guest_query = all_guests;
        else if (diag2fc(0, local_guest, NULL) > 0)
                diag2fc_guest_query = local_guest;
        else
                return -EACCES;
        hypfs_dbfs_create_file(&dbfs_file_2fc);
        return 0;
}

void hypfs_vm_exit(void)
{
        if (!machine_is_vm())
                return;
        hypfs_dbfs_remove_file(&dbfs_file_2fc);
}