Re: [Qemu-devel] [PATCH 23/25] fdc: Move floppy geometry guessing back from block.c

[Anthony Liguori <anthony@codemonkey.ws>]

On 07/09/2012 10:24 AM, Kevin Wolf wrote:
> Am 09.07.2012 17:01, schrieb Anthony Liguori:
>> On 07/09/2012 09:16 AM, Kevin Wolf wrote:
>>> From: Markus Armbruster<armbru@redhat.com>
>>>
>>> Commit 5bbdbb46 moved it to block.c because "other geometry guessing
>>> functions already reside in block.c".  Device-specific functionality
>>> should be kept in device code, not the block layer.  Move it back.
>>>
>>> Disk geometry guessing is still in block.c.  To be moved out in a
>>> later patch series.
>>>
>>> Bonus: the floppy type used in pc_cmos_init() now obviously matches
>>> the one in the FDrive.  Before, we relied on
>>> bdrv_get_floppy_geometry_hint() picking the same type both in
>>> fd_revalidate() and in pc_cmos_init().
>>>
>>> Signed-off-by: Markus Armbruster<armbru@redhat.com>
>>> Signed-off-by: Kevin Wolf<kwolf@redhat.com>
>
>>> diff --git a/hw/pc.c b/hw/pc.c
>>> index c7e9ab3..e5e7647 100644
>>> --- a/hw/pc.c
>>> +++ b/hw/pc.c
>>> @@ -335,10 +335,8 @@ void pc_cmos_init(ram_addr_t ram_size, ram_addr_t above_4g_mem_size,
>>>                      ISADevice *floppy, BusState *idebus0, BusState *idebus1,
>>>                      ISADevice *s)
>>>    {
>>> -    int val, nb, nb_heads, max_track, last_sect, i;
>>> -    FDriveType fd_type[2] = { FDRIVE_DRV_NONE, FDRIVE_DRV_NONE };
>>> -    FDriveRate rate;
>>> -    BlockDriverState *fd[MAX_FD];
>>> +    int val, nb, i;
>>> +    FDriveType fd_type[2];
>>
>> This results in:
>>
>>     CC    i386-softmmu/hw/i386/../pc.o
>> /home/anthony/git/qemu/hw/i386/../pc.c: In function ‘pc_cmos_init’:
>> /home/anthony/git/qemu/hw/i386/../pc.c:339:16: error: ‘fd_type[1]’ may be used
>> uninitialized in this function [-Werror=uninitialized]
>> /home/anthony/git/qemu/hw/i386/../pc.c:339:16: error: ‘fd_type[0]’ may be used
>> uninitialized in this function [-Werror=uninitialized]
>> cc1: all warnings being treated as errors
>>
>> And GCC is right as:
>>
>>>        static pc_cmos_init_late_arg arg;
>>>
>>>        /* various important CMOS locations needed by PC/Bochs bios */
>>> @@ -381,13 +379,8 @@ void pc_cmos_init(ram_addr_t ram_size, ram_addr_t above_4g_mem_size,
>>>
>>>        /* floppy type */
>>>        if (floppy) {
>>> -        fdc_get_bs(fd, floppy);
>>>            for (i = 0; i<   2; i++) {
>>> -            if (fd[i]) {
>>> -                bdrv_get_floppy_geometry_hint(fd[i],&nb_heads,&max_track,
>>> -&last_sect, FDRIVE_DRV_NONE,
>>> -&fd_type[i],&rate);
>>> -            }
>>> +            fd_type[i] = isa_fdc_get_drive_type(floppy, i);
>>>            }
>>>        }
>>>        val = (cmos_get_fd_drive_type(fd_type[0])<<   4) |
>>
>> This is an unconditional use of fd_type[0].  If floppy == NULL, this is
>> dereferencing an uninitialized value.
>>
>> I'm not sure why the explicit initialization was removed...
>
> Looks broken indeed. I just wonder why my gcc (or the buildbots) didn't
> complain.

:-)

> I dropped this patch from for-anthony, so you can give the pull request
> another try.

Okay, am building now and testing.  Looks good so far.

Regards,

Anthony Liguori

>
> Kevin