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[Qemu-devel] Re: [PATCH] Add serial number support for virtio_blk
From: |
john cooper |
Subject: |
[Qemu-devel] Re: [PATCH] Add serial number support for virtio_blk |
Date: |
Tue, 23 Jun 2009 08:42:32 -0400 |
User-agent: |
Thunderbird 2.0.0.9 (X11/20071115) |
Anthony Liguori wrote:
> john cooper wrote:
>>
>> s = (VirtIOBlock *)virtio_init_pci(bus, "virtio-blk",
>> PCI_VENDOR_ID_REDHAT_QUMRANET,
>> @@ -369,6 +420,10 @@ void *virtio_blk_init(PCIBus *bus,
>> BlockDriverState *bs)
>> s->vdev.reset = virtio_blk_reset;
>> s->bs = bs;
>> s->rq = NULL;
>> + if (strlen(ps = (char *)drive_get_serial(bs)))
>> + strncpy(s->serial_str, ps, sizeof(s->serial_str));
>> + else
>> + snprintf(s->serial_str, sizeof(s->serial_str), "0");
>>
>
> ps = drive_get_serial(bs);
> snprintf(s->serial_str, sizeof(s->serial_str), "%s", *ps ? ps : "0");
>
> strncpy() doesn't do what you think it does. It doesn't always null
> terminate.
In general yes, but here it is contrived to copy a
terminating nul. The string is maintained as a 21
byte [BLOCK_SERIAL_STRLEN + 1] char[] and the
incoming cmdline serial string is hard null terminated
by get_opt_value(). Above, strncpy() into a sizeof(21)
byte s->serial_str, will copy the trailing nul.
However when this data is exported by the guest driver
in a char[20] sized structure the trailing nul may be
omitted.
The same logic may be found in IDE and SCSI counterparts.
I agree it's not the most obvious approach, and this
clause should ideally be factored out as common to
all cases once we have the patch under discussion
resolved.
> Doesn't serial_str need to be saved in the savevm format?
Possibly, but currently it isn't being captured in
IDE nor SCSI AFAICT. I'll take a closer look.
-john
--
address@hidden
[Qemu-devel] Re: [PATCH] Add serial number support for virtio_blk, john cooper, 2009/06/23