qemu-io-cmds.c

/*
 * Command line utility to exercise the QEMU I/O path.
 *
 * Copyright (C) 2009-2016 Red Hat, Inc.
 * Copyright (c) 2003-2005 Silicon Graphics, Inc.
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 */

#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qapi/qmp/qdict.h"
#include "qemu-io.h"
#include "sysemu/block-backend.h"
#include "block/block.h"
#include "block/block_int.h" /* for info_f() */
#include "block/qapi.h"
#include "qemu/error-report.h"
#include "qemu/main-loop.h"
#include "qemu/option.h"
#include "qemu/timer.h"
#include "qemu/cutils.h"

#define CMD_NOFILE_OK   0x01

bool qemuio_misalign;

static cmdinfo_t *cmdtab;
static int ncmds;

static int compare_cmdname(const void *a, const void *b)
{
    return strcmp(((const cmdinfo_t *)a)->name,
                  ((const cmdinfo_t *)b)->name);
}

void qemuio_add_command(const cmdinfo_t *ci)
{
    /* ci->perm assumes a file is open, but the GLOBAL and NOFILE_OK
     * flags allow it not to be, so that combination is invalid.
     * Catch it now rather than letting it manifest as a crash if a
     * particular set of command line options are used.
     */
    assert(ci->perm == 0 ||
           (ci->flags & (CMD_FLAG_GLOBAL | CMD_NOFILE_OK)) == 0);
    cmdtab = g_renew(cmdinfo_t, cmdtab, ++ncmds);
    cmdtab[ncmds - 1] = *ci;
    qsort(cmdtab, ncmds, sizeof(*cmdtab), compare_cmdname);
}

void qemuio_command_usage(const cmdinfo_t *ci)
{
    printf("%s %s -- %s\n", ci->name, ci->args, ci->oneline);
}

static int init_check_command(BlockBackend *blk, const cmdinfo_t *ct)
{
    if (ct->flags & CMD_FLAG_GLOBAL) {
        return 1;
    }
    if (!(ct->flags & CMD_NOFILE_OK) && !blk) {
        fprintf(stderr, "no file open, try 'help open'\n");
        return 0;
    }
    return 1;
}

static int command(BlockBackend *blk, const cmdinfo_t *ct, int argc,
                   char **argv)
{
    char *cmd = argv[0];

    if (!init_check_command(blk, ct)) {
        return -EINVAL;
    }

    if (argc - 1 < ct->argmin || (ct->argmax != -1 && argc - 1 > ct->argmax)) {
        if (ct->argmax == -1) {
            fprintf(stderr,
                    "bad argument count %d to %s, expected at least %d arguments\n",
                    argc-1, cmd, ct->argmin);
        } else if (ct->argmin == ct->argmax) {
            fprintf(stderr,
                    "bad argument count %d to %s, expected %d arguments\n",
                    argc-1, cmd, ct->argmin);
        } else {
            fprintf(stderr,
                    "bad argument count %d to %s, expected between %d and %d arguments\n",
                    argc-1, cmd, ct->argmin, ct->argmax);
        }
        return -EINVAL;
    }

    /* Request additional permissions if necessary for this command. The caller
     * is responsible for restoring the original permissions afterwards if this
     * is what it wants. */
    if (ct->perm && blk_is_available(blk)) {
        uint64_t orig_perm, orig_shared_perm;
        blk_get_perm(blk, &orig_perm, &orig_shared_perm);

        if (ct->perm & ~orig_perm) {
            uint64_t new_perm;
            Error *local_err = NULL;
            int ret;

            new_perm = orig_perm | ct->perm;

            ret = blk_set_perm(blk, new_perm, orig_shared_perm, &local_err);
            if (ret < 0) {
                error_report_err(local_err);
                return ret;
            }
        }
    }

    qemu_reset_optind();
    return ct->cfunc(blk, argc, argv);
}

static const cmdinfo_t *find_command(const char *cmd)
{
    cmdinfo_t *ct;

    for (ct = cmdtab; ct < &cmdtab[ncmds]; ct++) {
        if (strcmp(ct->name, cmd) == 0 ||
            (ct->altname && strcmp(ct->altname, cmd) == 0))
        {
            return (const cmdinfo_t *)ct;
        }
    }
    return NULL;
}

/* Invoke fn() for commands with a matching prefix */
void qemuio_complete_command(const char *input,
                             void (*fn)(const char *cmd, void *opaque),
                             void *opaque)
{
    cmdinfo_t *ct;
    size_t input_len = strlen(input);

    for (ct = cmdtab; ct < &cmdtab[ncmds]; ct++) {
        if (strncmp(input, ct->name, input_len) == 0) {
            fn(ct->name, opaque);
        }
    }
}

static char **breakline(char *input, int *count)
{
    int c = 0;
    char *p;
    char **rval = g_new0(char *, 1);

    while (rval && (p = qemu_strsep(&input, " ")) != NULL) {
        if (!*p) {
            continue;
        }
        c++;
        rval = g_renew(char *, rval, (c + 1));
        rval[c - 1] = p;
        rval[c] = NULL;
    }
    *count = c;
    return rval;
}

static int64_t cvtnum(const char *s)
{
    int err;
    uint64_t value;

    err = qemu_strtosz(s, NULL, &value);
    if (err < 0) {
        return err;
    }
    if (value > INT64_MAX) {
        return -ERANGE;
    }
    return value;
}

static void print_cvtnum_err(int64_t rc, const char *arg)
{
    switch (rc) {
    case -EINVAL:
        printf("Parsing error: non-numeric argument,"
               " or extraneous/unrecognized suffix -- %s\n", arg);
        break;
    case -ERANGE:
        printf("Parsing error: argument too large -- %s\n", arg);
        break;
    default:
        printf("Parsing error: %s\n", arg);
    }
}

#define EXABYTES(x)     ((long long)(x) << 60)
#define PETABYTES(x)    ((long long)(x) << 50)
#define TERABYTES(x)    ((long long)(x) << 40)
#define GIGABYTES(x)    ((long long)(x) << 30)
#define MEGABYTES(x)    ((long long)(x) << 20)
#define KILOBYTES(x)    ((long long)(x) << 10)

#define TO_EXABYTES(x)  ((x) / EXABYTES(1))
#define TO_PETABYTES(x) ((x) / PETABYTES(1))
#define TO_TERABYTES(x) ((x) / TERABYTES(1))
#define TO_GIGABYTES(x) ((x) / GIGABYTES(1))
#define TO_MEGABYTES(x) ((x) / MEGABYTES(1))
#define TO_KILOBYTES(x) ((x) / KILOBYTES(1))

static void cvtstr(double value, char *str, size_t size)
{
    char *trim;
    const char *suffix;

    if (value >= EXABYTES(1)) {
        suffix = " EiB";
        snprintf(str, size - 4, "%.3f", TO_EXABYTES(value));
    } else if (value >= PETABYTES(1)) {
        suffix = " PiB";
        snprintf(str, size - 4, "%.3f", TO_PETABYTES(value));
    } else if (value >= TERABYTES(1)) {
        suffix = " TiB";
        snprintf(str, size - 4, "%.3f", TO_TERABYTES(value));
    } else if (value >= GIGABYTES(1)) {
        suffix = " GiB";
        snprintf(str, size - 4, "%.3f", TO_GIGABYTES(value));
    } else if (value >= MEGABYTES(1)) {
        suffix = " MiB";
        snprintf(str, size - 4, "%.3f", TO_MEGABYTES(value));
    } else if (value >= KILOBYTES(1)) {
        suffix = " KiB";
        snprintf(str, size - 4, "%.3f", TO_KILOBYTES(value));
    } else {
        suffix = " bytes";
        snprintf(str, size - 6, "%f", value);
    }

    trim = strstr(str, ".000");
    if (trim) {
        strcpy(trim, suffix);
    } else {
        strcat(str, suffix);
    }
}



static struct timespec tsub(struct timespec t1, struct timespec t2)
{
    t1.tv_nsec -= t2.tv_nsec;
    if (t1.tv_nsec < 0) {
        t1.tv_nsec += NANOSECONDS_PER_SECOND;
        t1.tv_sec--;
    }
    t1.tv_sec -= t2.tv_sec;
    return t1;
}

static double tdiv(double value, struct timespec tv)
{
    double seconds = tv.tv_sec + (tv.tv_nsec / 1e9);
    return value / seconds;
}

#define HOURS(sec)      ((sec) / (60 * 60))
#define MINUTES(sec)    (((sec) % (60 * 60)) / 60)
#define SECONDS(sec)    ((sec) % 60)

enum {
    DEFAULT_TIME        = 0x0,
    TERSE_FIXED_TIME    = 0x1,
    VERBOSE_FIXED_TIME  = 0x2,
};

static void timestr(struct timespec *tv, char *ts, size_t size, int format)
{
    double frac_sec = tv->tv_nsec / 1e9;

    if (format & TERSE_FIXED_TIME) {
        if (!HOURS(tv->tv_sec)) {
            snprintf(ts, size, "%u:%05.2f",
                     (unsigned int) MINUTES(tv->tv_sec),
                     SECONDS(tv->tv_sec) + frac_sec);
            return;
        }
        format |= VERBOSE_FIXED_TIME; /* fallback if hours needed */
    }

    if ((format & VERBOSE_FIXED_TIME) || tv->tv_sec) {
        snprintf(ts, size, "%u:%02u:%05.2f",
                (unsigned int) HOURS(tv->tv_sec),
                (unsigned int) MINUTES(tv->tv_sec),
                 SECONDS(tv->tv_sec) + frac_sec);
    } else {
        snprintf(ts, size, "%05.2f sec", frac_sec);
    }
}

/*
 * Parse the pattern argument to various sub-commands.
 *
 * Because the pattern is used as an argument to memset it must evaluate
 * to an unsigned integer that fits into a single byte.
 */
static int parse_pattern(const char *arg)
{
    char *endptr = NULL;
    long pattern;

    pattern = strtol(arg, &endptr, 0);
    if (pattern < 0 || pattern > UCHAR_MAX || *endptr != '\0') {
        printf("%s is not a valid pattern byte\n", arg);
        return -1;
    }

    return pattern;
}

/*
 * Memory allocation helpers.
 *
 * Make sure memory is aligned by default, or purposefully misaligned if
 * that is specified on the command line.
 */

#define MISALIGN_OFFSET     16
static void *qemu_io_alloc(BlockBackend *blk, size_t len, int pattern)
{
    void *buf;

    if (qemuio_misalign) {
        len += MISALIGN_OFFSET;
    }
    buf = blk_blockalign(blk, len);
    memset(buf, pattern, len);
    if (qemuio_misalign) {
        buf += MISALIGN_OFFSET;
    }
    return buf;
}

static void qemu_io_free(void *p)
{
    if (qemuio_misalign) {
        p -= MISALIGN_OFFSET;
    }
    qemu_vfree(p);
}

/*
 * qemu_io_alloc_from_file()
 *
 * Allocates the buffer and populates it with the content of the given file
 * up to @len bytes. If the file length is less than @len, then the buffer
 * is populated with the file content cyclically.
 *
 * @blk - the block backend where the buffer content is going to be written to
 * @len - the buffer length
 * @file_name - the file to read the content from
 *
 * Returns: the buffer pointer on success
 *          NULL on error
 */
static void *qemu_io_alloc_from_file(BlockBackend *blk, size_t len,
                                     const char *file_name)
{
    char *buf, *buf_origin;
    FILE *f = fopen(file_name, "r");
    int pattern_len;

    if (!f) {
        perror(file_name);
        return NULL;
    }

    if (qemuio_misalign) {
        len += MISALIGN_OFFSET;
    }

    buf_origin = buf = blk_blockalign(blk, len);

    if (qemuio_misalign) {
        buf_origin += MISALIGN_OFFSET;
        buf += MISALIGN_OFFSET;
        len -= MISALIGN_OFFSET;
    }

    pattern_len = fread(buf_origin, 1, len, f);

    if (ferror(f)) {
        perror(file_name);
        goto error;
    }

    if (pattern_len == 0) {
        fprintf(stderr, "%s: file is empty\n", file_name);
        goto error;
    }

    fclose(f);
    f = NULL;

    if (len > pattern_len) {
        len -= pattern_len;
        buf += pattern_len;

        while (len > 0) {
            size_t len_to_copy = MIN(pattern_len, len);

            memcpy(buf, buf_origin, len_to_copy);

            len -= len_to_copy;
            buf += len_to_copy;
        }
    }

    return buf_origin;

error:
    qemu_io_free(buf_origin);
    if (f) {
        fclose(f);
    }
    return NULL;
}

static void dump_buffer(const void *buffer, int64_t offset, int64_t len)
{
    uint64_t i;
    int j;
    const uint8_t *p;

    for (i = 0, p = buffer; i < len; i += 16) {
        const uint8_t *s = p;

        printf("%08" PRIx64 ":  ", offset + i);
        for (j = 0; j < 16 && i + j < len; j++, p++) {
            printf("%02x ", *p);
        }
        printf(" ");
        for (j = 0; j < 16 && i + j < len; j++, s++) {
            if (isalnum(*s)) {
                printf("%c", *s);
            } else {
                printf(".");
            }
        }
        printf("\n");
    }
}

static void print_report(const char *op, struct timespec *t, int64_t offset,
                         int64_t count, int64_t total, int cnt, bool Cflag)
{
    char s1[64], s2[64], ts[64];

    timestr(t, ts, sizeof(ts), Cflag ? VERBOSE_FIXED_TIME : 0);
    if (!Cflag) {
        cvtstr((double)total, s1, sizeof(s1));
        cvtstr(tdiv((double)total, *t), s2, sizeof(s2));
        printf("%s %"PRId64"/%"PRId64" bytes at offset %" PRId64 "\n",
               op, total, count, offset);
        printf("%s, %d ops; %s (%s/sec and %.4f ops/sec)\n",
               s1, cnt, ts, s2, tdiv((double)cnt, *t));
    } else {/* bytes,ops,time,bytes/sec,ops/sec */
        printf("%"PRId64",%d,%s,%.3f,%.3f\n",
            total, cnt, ts,
            tdiv((double)total, *t),
            tdiv((double)cnt, *t));
    }
}

/*
 * Parse multiple length statements for vectored I/O, and construct an I/O
 * vector matching it.
 */
static void *
create_iovec(BlockBackend *blk, QEMUIOVector *qiov, char **argv, int nr_iov,
             int pattern)
{
    size_t *sizes = g_new0(size_t, nr_iov);
    size_t count = 0;
    void *buf = NULL;
    void *p;
    int i;

    for (i = 0; i < nr_iov; i++) {
        char *arg = argv[i];
        int64_t len;

        len = cvtnum(arg);
        if (len < 0) {
            print_cvtnum_err(len, arg);
            goto fail;
        }

        if (len > BDRV_REQUEST_MAX_BYTES) {
            printf("Argument '%s' exceeds maximum size %" PRIu64 "\n", arg,
                   (uint64_t)BDRV_REQUEST_MAX_BYTES);
            goto fail;
        }

        if (count > BDRV_REQUEST_MAX_BYTES - len) {
            printf("The total number of bytes exceed the maximum size %" PRIu64
                   "\n", (uint64_t)BDRV_REQUEST_MAX_BYTES);
            goto fail;
        }

        sizes[i] = len;
        count += len;
    }

    qemu_iovec_init(qiov, nr_iov);

    buf = p = qemu_io_alloc(blk, count, pattern);

    for (i = 0; i < nr_iov; i++) {
        qemu_iovec_add(qiov, p, sizes[i]);
        p += sizes[i];
    }

fail:
    g_free(sizes);
    return buf;
}

static int do_pread(BlockBackend *blk, char *buf, int64_t offset,
                    int64_t bytes, int64_t *total)
{
    if (bytes > INT_MAX) {
        return -ERANGE;
    }

    *total = blk_pread(blk, offset, (uint8_t *)buf, bytes);
    if (*total < 0) {
        return *total;
    }
    return 1;
}

static int do_pwrite(BlockBackend *blk, char *buf, int64_t offset,
                     int64_t bytes, int flags, int64_t *total)
{
    if (bytes > INT_MAX) {
        return -ERANGE;
    }

    *total = blk_pwrite(blk, offset, (uint8_t *)buf, bytes, flags);
    if (*total < 0) {
        return *total;
    }
    return 1;
}

typedef struct {
    BlockBackend *blk;
    int64_t offset;
    int64_t bytes;
    int64_t *total;
    int flags;
    int ret;
    bool done;
} CoWriteZeroes;

static void coroutine_fn co_pwrite_zeroes_entry(void *opaque)
{
    CoWriteZeroes *data = opaque;

    data->ret = blk_co_pwrite_zeroes(data->blk, data->offset, data->bytes,
                                     data->flags);
    data->done = true;
    if (data->ret < 0) {
        *data->total = data->ret;
        return;
    }

    *data->total = data->bytes;
}

static int do_co_pwrite_zeroes(BlockBackend *blk, int64_t offset,
                               int64_t bytes, int flags, int64_t *total)
{
    Coroutine *co;
    CoWriteZeroes data = {
        .blk    = blk,
        .offset = offset,
        .bytes  = bytes,
        .total  = total,
        .flags  = flags,
        .done   = false,
    };

    if (bytes > INT_MAX) {
        return -ERANGE;
    }

    co = qemu_coroutine_create(co_pwrite_zeroes_entry, &data);
    bdrv_coroutine_enter(blk_bs(blk), co);
    while (!data.done) {
        aio_poll(blk_get_aio_context(blk), true);
    }
    if (data.ret < 0) {
        return data.ret;
    } else {
        return 1;
    }
}

static int do_write_compressed(BlockBackend *blk, char *buf, int64_t offset,
                               int64_t bytes, int64_t *total)
{
    int ret;

    if (bytes > BDRV_REQUEST_MAX_BYTES) {
        return -ERANGE;
    }

    ret = blk_pwrite_compressed(blk, offset, buf, bytes);
    if (ret < 0) {
        return ret;
    }
    *total = bytes;
    return 1;
}

static int do_load_vmstate(BlockBackend *blk, char *buf, int64_t offset,
                           int64_t count, int64_t *total)
{
    if (count > INT_MAX) {
        return -ERANGE;
    }

    *total = blk_load_vmstate(blk, (uint8_t *)buf, offset, count);
    if (*total < 0) {
        return *total;
    }
    return 1;
}

static int do_save_vmstate(BlockBackend *blk, char *buf, int64_t offset,
                           int64_t count, int64_t *total)
{
    if (count > INT_MAX) {
        return -ERANGE;
    }

    *total = blk_save_vmstate(blk, (uint8_t *)buf, offset, count);
    if (*total < 0) {
        return *total;
    }
    return 1;
}

#define NOT_DONE 0x7fffffff
static void aio_rw_done(void *opaque, int ret)
{
    *(int *)opaque = ret;
}

static int do_aio_readv(BlockBackend *blk, QEMUIOVector *qiov,
                        int64_t offset, int *total)
{
    int async_ret = NOT_DONE;

    blk_aio_preadv(blk, offset, qiov, 0, aio_rw_done, &async_ret);
    while (async_ret == NOT_DONE) {
        main_loop_wait(false);
    }

    *total = qiov->size;
    return async_ret < 0 ? async_ret : 1;
}

static int do_aio_writev(BlockBackend *blk, QEMUIOVector *qiov,
                         int64_t offset, int flags, int *total)
{
    int async_ret = NOT_DONE;

    blk_aio_pwritev(blk, offset, qiov, flags, aio_rw_done, &async_ret);
    while (async_ret == NOT_DONE) {
        main_loop_wait(false);
    }

    *total = qiov->size;
    return async_ret < 0 ? async_ret : 1;
}

static void read_help(void)
{
    printf(
"\n"
" reads a range of bytes from the given offset\n"
"\n"
" Example:\n"
" 'read -v 512 1k' - dumps 1 kilobyte read from 512 bytes into the file\n"
"\n"
" Reads a segment of the currently open file, optionally dumping it to the\n"
" standard output stream (with -v option) for subsequent inspection.\n"
" -b, -- read from the VM state rather than the virtual disk\n"
" -C, -- report statistics in a machine parsable format\n"
" -l, -- length for pattern verification (only with -P)\n"
" -p, -- ignored for backwards compatibility\n"
" -P, -- use a pattern to verify read data\n"
" -q, -- quiet mode, do not show I/O statistics\n"
" -s, -- start offset for pattern verification (only with -P)\n"
" -v, -- dump buffer to standard output\n"
"\n");
}

static int read_f(BlockBackend *blk, int argc, char **argv);

static const cmdinfo_t read_cmd = {
    .name       = "read",
    .altname    = "r",
    .cfunc      = read_f,
    .argmin     = 2,
    .argmax     = -1,
    .args       = "[-abCqv] [-P pattern [-s off] [-l len]] off len",
    .oneline    = "reads a number of bytes at a specified offset",
    .help       = read_help,
};

static int read_f(BlockBackend *blk, int argc, char **argv)
{
    struct timespec t1, t2;
    bool Cflag = false, qflag = false, vflag = false;
    bool Pflag = false, sflag = false, lflag = false, bflag = false;
    int c, cnt, ret;
    char *buf;
    int64_t offset;
    int64_t count;
    /* Some compilers get confused and warn if this is not initialized.  */
    int64_t total = 0;
    int pattern = 0;
    int64_t pattern_offset = 0, pattern_count = 0;

    while ((c = getopt(argc, argv, "bCl:pP:qs:v")) != -1) {
        switch (c) {
        case 'b':
            bflag = true;
            break;
        case 'C':
            Cflag = true;
            break;
        case 'l':
            lflag = true;
            pattern_count = cvtnum(optarg);
            if (pattern_count < 0) {
                print_cvtnum_err(pattern_count, optarg);
                return pattern_count;
            }
            break;
        case 'p':
            /* Ignored for backwards compatibility */
            break;
        case 'P':
            Pflag = true;
            pattern = parse_pattern(optarg);
            if (pattern < 0) {
                return -EINVAL;
            }
            break;
        case 'q':
            qflag = true;
            break;
        case 's':
            sflag = true;
            pattern_offset = cvtnum(optarg);
            if (pattern_offset < 0) {
                print_cvtnum_err(pattern_offset, optarg);
                return pattern_offset;
            }
            break;
        case 'v':
            vflag = true;
            break;
        default:
            qemuio_command_usage(&read_cmd);
            return -EINVAL;
        }
    }

    if (optind != argc - 2) {
        qemuio_command_usage(&read_cmd);
        return -EINVAL;
    }

    offset = cvtnum(argv[optind]);
    if (offset < 0) {
        print_cvtnum_err(offset, argv[optind]);
        return offset;
    }

    optind++;
    count = cvtnum(argv[optind]);
    if (count < 0) {
        print_cvtnum_err(count, argv[optind]);
        return count;
    } else if (count > BDRV_REQUEST_MAX_BYTES) {
        printf("length cannot exceed %" PRIu64 ", given %s\n",
               (uint64_t)BDRV_REQUEST_MAX_BYTES, argv[optind]);
        return -EINVAL;
    }

    if (!Pflag && (lflag || sflag)) {
        qemuio_command_usage(&read_cmd);
        return -EINVAL;
    }

    if (!lflag) {
        pattern_count = count - pattern_offset;
    }

    if ((pattern_count < 0) || (pattern_count + pattern_offset > count))  {
        printf("pattern verification range exceeds end of read data\n");
        return -EINVAL;
    }

    if (bflag) {
        if (!QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)) {
            printf("%" PRId64 " is not a sector-aligned value for 'offset'\n",
                   offset);
            return -EINVAL;
        }
        if (!QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE)) {
            printf("%"PRId64" is not a sector-aligned value for 'count'\n",
                   count);
            return -EINVAL;
        }
    }

    buf = qemu_io_alloc(blk, count, 0xab);

    clock_gettime(CLOCK_MONOTONIC, &t1);
    if (bflag) {
        ret = do_load_vmstate(blk, buf, offset, count, &total);
    } else {
        ret = do_pread(blk, buf, offset, count, &total);
    }
    clock_gettime(CLOCK_MONOTONIC, &t2);

    if (ret < 0) {
        printf("read failed: %s\n", strerror(-ret));
        goto out;
    }
    cnt = ret;

    ret = 0;

    if (Pflag) {
        void *cmp_buf = g_malloc(pattern_count);
        memset(cmp_buf, pattern, pattern_count);
        if (memcmp(buf + pattern_offset, cmp_buf, pattern_count)) {
            printf("Pattern verification failed at offset %"
                   PRId64 ", %"PRId64" bytes\n",
                   offset + pattern_offset, pattern_count);
            ret = -EINVAL;
        }
        g_free(cmp_buf);
    }

    if (qflag) {
        goto out;
    }

    if (vflag) {
        dump_buffer(buf, offset, count);
    }

    /* Finally, report back -- -C gives a parsable format */
    t2 = tsub(t2, t1);
    print_report("read", &t2, offset, count, total, cnt, Cflag);

out:
    qemu_io_free(buf);
    return ret;
}

static void readv_help(void)
{
    printf(
"\n"
" reads a range of bytes from the given offset into multiple buffers\n"
"\n"
" Example:\n"
" 'readv -v 512 1k 1k ' - dumps 2 kilobytes read from 512 bytes into the file\n"
"\n"
" Reads a segment of the currently open file, optionally dumping it to the\n"
" standard output stream (with -v option) for subsequent inspection.\n"
" Uses multiple iovec buffers if more than one byte range is specified.\n"
" -C, -- report statistics in a machine parsable format\n"
" -P, -- use a pattern to verify read data\n"
" -v, -- dump buffer to standard output\n"
" -q, -- quiet mode, do not show I/O statistics\n"
"\n");
}

static int readv_f(BlockBackend *blk, int argc, char **argv);

static const cmdinfo_t readv_cmd = {
    .name       = "readv",
    .cfunc      = readv_f,
    .argmin     = 2,
    .argmax     = -1,
    .args       = "[-Cqv] [-P pattern] off len [len..]",
    .oneline    = "reads a number of bytes at a specified offset",
    .help       = readv_help,
};

static int readv_f(BlockBackend *blk, int argc, char **argv)
{
    struct timespec t1, t2;
    bool Cflag = false, qflag = false, vflag = false;
    int c, cnt, ret;
    char *buf;
    int64_t offset;
    /* Some compilers get confused and warn if this is not initialized.  */
    int total = 0;
    int nr_iov;
    QEMUIOVector qiov;
    int pattern = 0;
    bool Pflag = false;

    while ((c = getopt(argc, argv, "CP:qv")) != -1) {
        switch (c) {
        case 'C':
            Cflag = true;
            break;
        case 'P':
            Pflag = true;
            pattern = parse_pattern(optarg);
            if (pattern < 0) {
                return -EINVAL;
            }
            break;
        case 'q':
            qflag = true;
            break;
        case 'v':
            vflag = true;
            break;
        default:
            qemuio_command_usage(&readv_cmd);
            return -EINVAL;
        }
    }

    if (optind > argc - 2) {
        qemuio_command_usage(&readv_cmd);
        return -EINVAL;
    }


    offset = cvtnum(argv[optind]);
    if (offset < 0) {
        print_cvtnum_err(offset, argv[optind]);
        return offset;
    }
    optind++;

    nr_iov = argc - optind;
    buf = create_iovec(blk, &qiov, &argv[optind], nr_iov, 0xab);
    if (buf == NULL) {
        return -EINVAL;
    }

    clock_gettime(CLOCK_MONOTONIC, &t1);
    ret = do_aio_readv(blk, &qiov, offset, &total);
    clock_gettime(CLOCK_MONOTONIC, &t2);

    if (ret < 0) {
        printf("readv failed: %s\n", strerror(-ret));
        goto out;
    }
    cnt = ret;

    ret = 0;

    if (Pflag) {
        void *cmp_buf = g_malloc(qiov.size);
        memset(cmp_buf, pattern, qiov.size);
        if (memcmp(buf, cmp_buf, qiov.size)) {
            printf("Pattern verification failed at offset %"
                   PRId64 ", %zu bytes\n", offset, qiov.size);
            ret = -EINVAL;
        }
        g_free(cmp_buf);
    }

    if (qflag) {
        goto out;
    }

    if (vflag) {
        dump_buffer(buf, offset, qiov.size);
    }