bsd-user: sysctl helper funtions: sysctl_name2oid and sysctl_oidfmt

[mirror_qemu.git] / bsd-user / freebsd / os-sys.c

/*
 *  FreeBSD sysctl() and sysarch() system call emulation
 *
 *  Copyright (c) 2013-15 Stacey D. Son
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include "qemu/osdep.h"
#include "qemu.h"
#include "target_arch_sysarch.h"

#include <sys/sysctl.h>

/*
 * Length for the fixed length types.
 * 0 means variable length for strings and structures
 * Compare with sys/kern_sysctl.c ctl_size
 * Note: Not all types appear to be used in-tree.
 */
static const int guest_ctl_size[CTLTYPE + 1] = {
        [CTLTYPE_INT] = sizeof(abi_int),
        [CTLTYPE_UINT] = sizeof(abi_uint),
        [CTLTYPE_LONG] = sizeof(abi_long),
        [CTLTYPE_ULONG] = sizeof(abi_ulong),
        [CTLTYPE_S8] = sizeof(int8_t),
        [CTLTYPE_S16] = sizeof(int16_t),
        [CTLTYPE_S32] = sizeof(int32_t),
        [CTLTYPE_S64] = sizeof(int64_t),
        [CTLTYPE_U8] = sizeof(uint8_t),
        [CTLTYPE_U16] = sizeof(uint16_t),
        [CTLTYPE_U32] = sizeof(uint32_t),
        [CTLTYPE_U64] = sizeof(uint64_t),
};

static const int host_ctl_size[CTLTYPE + 1] = {
        [CTLTYPE_INT] = sizeof(int),
        [CTLTYPE_UINT] = sizeof(u_int),
        [CTLTYPE_LONG] = sizeof(long),
        [CTLTYPE_ULONG] = sizeof(u_long),
        [CTLTYPE_S8] = sizeof(int8_t),
        [CTLTYPE_S16] = sizeof(int16_t),
        [CTLTYPE_S32] = sizeof(int32_t),
        [CTLTYPE_S64] = sizeof(int64_t),
        [CTLTYPE_U8] = sizeof(uint8_t),
        [CTLTYPE_U16] = sizeof(uint16_t),
        [CTLTYPE_U32] = sizeof(uint32_t),
        [CTLTYPE_U64] = sizeof(uint64_t),
};

#ifdef TARGET_ABI32
/*
 * Limit the amount of available memory to be most of the 32-bit address
 * space. 0x100c000 was arrived at through trial and error as a good
 * definition of 'most'.
 */
static const abi_ulong guest_max_mem = UINT32_MAX - 0x100c000 + 1;

static abi_ulong G_GNUC_UNUSED cap_memory(uint64_t mem)
{
    return MIN(guest_max_mem, mem);
}
#endif

static abi_ulong G_GNUC_UNUSED scale_to_guest_pages(uint64_t pages)
{
    /* Scale pages from host to guest */
    pages = muldiv64(pages, qemu_real_host_page_size(), TARGET_PAGE_SIZE);
#ifdef TARGET_ABI32
    /* cap pages if need be */
    pages = MIN(pages, guest_max_mem / (abi_ulong)TARGET_PAGE_SIZE);
#endif
    return pages;
}

#ifdef TARGET_ABI32
/* Used only for TARGET_ABI32 */
static abi_long h2g_long_sat(long l)
{
    if (l > INT32_MAX) {
        l = INT32_MAX;
    } else if (l < INT32_MIN) {
        l = INT32_MIN;
    }
    return l;
}

static abi_ulong h2g_ulong_sat(u_long ul)
{
    return MIN(ul, UINT32_MAX);
}
#endif

/*
 * placeholder until bsd-user downstream upstreams this with its thread support
 */
#define bsd_get_ncpu() 1

/*
 * This uses the undocumented oidfmt interface to find the kind of a requested
 * sysctl, see /sys/kern/kern_sysctl.c:sysctl_sysctl_oidfmt() (compare to
 * src/sbin/sysctl/sysctl.c)
 */
static int G_GNUC_UNUSED oidfmt(int *oid, int len, char *fmt, uint32_t *kind)
{
    int qoid[CTL_MAXNAME + 2];
    uint8_t buf[BUFSIZ];
    int i;
    size_t j;

    qoid[0] = CTL_SYSCTL;
    qoid[1] = CTL_SYSCTL_OIDFMT;
    memcpy(qoid + 2, oid, len * sizeof(int));

    j = sizeof(buf);
    i = sysctl(qoid, len + 2, buf, &j, 0, 0);
    if (i) {
        return i;
    }

    if (kind) {
        *kind = *(uint32_t *)buf;
    }

    if (fmt) {
        strcpy(fmt, (char *)(buf + sizeof(uint32_t)));
    }
    return 0;
}

/*
 * Convert the old value from host to guest.
 *
 * For LONG and ULONG on ABI32, we need to 'down convert' the 8 byte quantities
 * to 4 bytes. The caller setup a buffer in host memory to get this data from
 * the kernel and pass it to us. We do the down conversion and adjust the length
 * so the caller knows what to write as the returned length into the target when
 * it copies the down converted values into the target.
 *
 * For normal integral types, we just need to byte swap. No size changes.
 *
 * For strings and node data, there's no conversion needed.
 *
 * For opaque data, per sysctl OID converts take care of it.
 */
static void G_GNUC_UNUSED h2g_old_sysctl(void *holdp, size_t *holdlen, uint32_t kind)
{
    size_t len;
    int hlen, glen;
    uint8_t *hp, *gp;

    /*
     * Although rare, we can have arrays of sysctl. Both sysctl_old_ddb in
     * kern_sysctl.c and show_var in sbin/sysctl/sysctl.c have code that loops
     * this way.  *holdlen has been set by the kernel to the host's length.
     * Only LONG and ULONG on ABI32 have different sizes: see below.
     */
    gp = hp = (uint8_t *)holdp;
    len = 0;
    hlen = host_ctl_size[kind & CTLTYPE];
    glen = guest_ctl_size[kind & CTLTYPE];

    /*
     * hlen == 0 for CTLTYPE_STRING and CTLTYPE_NODE, which need no conversion
     * as well as CTLTYPE_OPAQUE, which needs special converters.
     */
    if (hlen == 0) {
        return;
    }

    while (len < *holdlen) {
        if (hlen == glen) {
            switch (hlen) {
            case 1:
                /* Nothing needed: no byteswapping and assigning in place */
                break;
            case 2:
                *(uint16_t *)gp = tswap16(*(uint16_t *)hp);
                break;
            case 4:
                *(uint32_t *)gp = tswap32(*(uint32_t *)hp);
                break;
            case 8:
                *(uint64_t *)gp = tswap64(*(uint64_t *)hp);
                break;
            default:
                g_assert_not_reached();
            }
        } else {
#ifdef TARGET_ABI32
            /*
             * Saturating assignment for the only two types that differ between
             * 32-bit and 64-bit machines. All other integral types have the
             * same, fixed size and will be converted w/o loss of precision
             * in the above switch.
             */
            switch (kind & CTLTYPE) {
            case CTLTYPE_LONG:
                *(abi_long *)gp = tswap32(h2g_long_sat(*(long *)hp));
                break;
            case CTLTYPE_ULONG:
                *(abi_ulong *)gp = tswap32(h2g_ulong_sat(*(u_long *)hp));
                break;
            default:
                g_assert_not_reached();
            }
#else
            g_assert_not_reached();
#endif
        }
        gp += glen;
        hp += hlen;
        len += hlen;
    }
#ifdef TARGET_ABI32
    if (hlen != glen) {
        *holdlen = (*holdlen / hlen) * glen;
    }
#endif
}

/*
 * Convert the undocmented name2oid sysctl data for the target.
 */
static inline void G_GNUC_UNUSED sysctl_name2oid(uint32_t *holdp, size_t holdlen)
{
    size_t i, num = holdlen / sizeof(uint32_t);

    for (i = 0; i < num; i++) {
        holdp[i] = tswap32(holdp[i]);
    }
}

static inline void G_GNUC_UNUSED sysctl_oidfmt(uint32_t *holdp)
{
    /* byte swap the kind */
    holdp[0] = tswap32(holdp[0]);
}

/* sysarch() is architecture dependent. */
abi_long do_freebsd_sysarch(void *cpu_env, abi_long arg1, abi_long arg2)
{
    return do_freebsd_arch_sysarch(cpu_env, arg1, arg2);
}