On Fri, 2013-06-28 at 17:39 +0100, David Howells wrote:
> The MN10300 arch is throwing up an error in the SCSI driver and I'm not sure
> whether it needs fixing in the arch - in get_user() - or in the SCSI code.
>
> The problem is this line in sg_scsi_ioctl():
>
> if (get_user(opcode, sic->data))
>
> sic points to the following struct:
>
> typedef struct scsi_ioctl_command {
> unsigned int inlen;
> unsigned int outlen;
> unsigned char data[0];
> } Scsi_Ioctl_Command;
>
> However, __get_user_check() on MN10300 does this:
>
> const __typeof__(ptr) __guc_ptr = (ptr);
>
> which fails with:
>
> block/scsi_ioctl.c:450: error: invalid initializer
>
> The question is what is SCSI actually asking get_user() to do? As far as I
> can tell, gcc thinks that it's being askied to declare some sort of array
> here.
I'm surprised you need to ask this. by convention, an array of char is
usable as a pointer to char *. The compiler therefore thinks this is a
legitimate conversion which doesn't need a cast:
unsigned char *d = sic->data;
Therefore, sic->data should be usable as a char * pointer everywhere.
> Should the SCSI driver be changed to:
>
> if (get_user(opcode, (unsigned char *)sic->data))
can we visit reality for a minute? That proposal would require us to do
an explicit (unsigned char *) conversion everywhere we use an array as a
pointer value ... good grief, no!
> or should the MN10300 arch be changed to morph the array into a pointer,
> perhaps with:
>
> const __typeof__(ptr[0])* __guc_ptr = (ptr);
Neither. It should do what every other architecture does, which is:
const __typeof__(*(ptr)) *__guc_ptr = (ptr);
James
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