Re: [Qemu-devel] [RFC PATCH v2 07/17] fuzz: Add ramfile qemu-file type

[Paolo Bonzini]

On 05/08/19 09:11, Oleinik, Alexander wrote:
> +#ifdef CONFIG_FUZZ
> +#define INCREMENT 10240
> +static ssize_t ram_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
> +        int64_t pos)
> +{
> +    ram_disk *rd = (ram_disk *)opaque;
> +    gsize newsize;
> +    ssize_t total_size = 0;
> +    int i;
> +    if (!rd->base) {
> +        rd->base = g_malloc(INCREMENT);
> +        rd->len = INCREMENT;
> +    }
> +    for (i = 0; i < iovcnt; i++) {
> +        if (pos + iov[i].iov_len >= rd->len) {
> +            newsize = ((pos + iov[i].iov_len) / INCREMENT + 1) * INCREMENT;
> +            rd->base = g_realloc(rd->base, newsize);
> +            rd->len = newsize;
> +        }
> +        memcpy(rd->base + pos, iov[i].iov_base, iov[i].iov_len);
> +        pos += iov[i].iov_len;
> +        total_size += iov[i].iov_len;
> +    }
> +    return total_size;
> +}

A lot of this code can be replaced with GByteArray:
https://developer.gnome.org/glib/stable/glib-Byte-Arrays.html

Since GByteArray is reference counted, you could also easily get rid of
qemu_freopen_ro_ram.  Instead, just close the old QEMUFile and open a
new one.

Paolo

> +static ssize_t ram_get_buffer(void *opaque, uint8_t *buf, int64_t pos,
> +        size_t size)
> +{
> +    ram_disk *rd = (ram_disk *)opaque;
> +    if (pos + size > rd->len) {
> +        if (rd->len - pos >= 0) {
> +            memcpy(buf, rd->base + pos, rd->len - pos);
> +            size = rd->len - pos;
> +        }
> +    } else {
> +        memcpy(buf, rd->base + pos, size);
> +    }
> +    return size;
> +}
> +
> +static int ram_fclose(void *opaque)
> +{
> +    return 0;
> +}
> +
> +static const QEMUFileOps ram_read_ops = {
> +    .get_buffer = ram_get_buffer,
> +    .close =      ram_fclose
> +};
> +
> +static const QEMUFileOps ram_write_ops = {
> +    .writev_buffer = ram_writev_buffer,
> +    .close =      ram_fclose
> +};
> +
> +QEMUFile *qemu_fopen_ram(ram_disk **return_rd)
> +{
> +    ram_disk *rd = g_new0(ram_disk, 1);
> +    *return_rd = rd;
> +    return qemu_fopen_ops(rd, &ram_write_ops);
> +}
> +
> +QEMUFile *qemu_fopen_ro_ram(ram_disk* rd)
> +{
> +    return qemu_fopen_ops(rd, &ram_read_ops);
> +}
> +
> +void qemu_freopen_ro_ram(QEMUFile *f)
> +{
> +    void *rd = f->opaque;
> +    f->bytes_xfer = 0;
> +    f->xfer_limit = 0;
> +    f->last_error = 0;
> +    f->iovcnt = 0;
> +    f->buf_index = 0;
> +    f->buf_size = 0;
> +    f->pos = 0;
> +    f->ops = &ram_read_ops;
> +    f->opaque = rd;
> +    return;
> +}
> +#endif
> diff --git a/migration/qemu-file.h b/migration/qemu-file.h
> index 13baf896bd..7048674f1b 100644
> --- a/migration/qemu-file.h
> +++ b/migration/qemu-file.h
> @@ -177,4 +177,15 @@ size_t ram_control_save_page(QEMUFile *f, ram_addr_t 
> block_offset,
>  
>  void qemu_put_counted_string(QEMUFile *f, const char *name);
>  
> +#ifdef CONFIG_FUZZ
> +typedef struct ram_disk {
> +    void *base;
> +    gsize len;
> +} ram_disk;
> +
> +QEMUFile *qemu_fopen_ram(ram_disk **rd);
> +QEMUFile *qemu_fopen_ro_ram(ram_disk* rd);
> +void qemu_freopen_ro_ram(QEMUFile *f);
> +#endif
> +
>  #endif
>