[U-Boot] [PATCH] Loop block device for sandbox

[Pavel Herrmann]

On Thursday 30 of August 2012 20:45:13 Marek Vasut wrote:
> Dear Pavel Herrmann,
> 
> > On Thursday 30 of August 2012 00:18:18 Marek Vasut wrote:
> > ...snip...
> > 
> > > > +extern block_dev_desc_t sata_dev_desc[];
> > > > +
> > > > +int init_sata(int dev)
> > > > +{
> > > > +	block_dev_desc_t *pdev = &(sata_dev_desc[dev]);
> > > 
> > > Superfluous braces ... Actually, I think sata_dev_desc as it would work
> > > very well too.
> > 
> > Straight copy from dwc_ahsata.c, makes it more readable thought, as the
> > order of operation is not very intuitive IMHO.
> 
> sata_dev_desc + dev ?

even less intuitive

> > > > +lbaint_t sata_read(int dev, lbaint_t start, lbaint_t blkcnt, void
> > > > *buffer)
> > > > +{
> > > > +	block_dev_desc_t *pdev = &(sata_dev_desc[dev]);
> > > > +	int fd = (long) pdev->priv;
> > > 
> > > If pdev is NULL, this will crash
> > 
> > well, it isn't, at least not from the command - thats why you define the
> > number of ports in advance, you get "dev" already range-checked
> 
> Range check is fine, but will pdev be inited? It's a pointer from some
> array.

init_sata is called first, so pdev is inited (see cmd_sata.c)

> > > > +	lbaint_t retval;
> > > > +
> > > > +	os_lseek(fd, start*ATA_SECT_SIZE, OS_SEEK_SET);
> > > > +	retval = os_read(fd, buffer, ATA_SECT_SIZE * blkcnt);
> > > > +
> > > > +	return retval/ATA_SECT_SIZE;
> > > > +}
> > > > +
> > > > +lbaint_t sata_write(int dev, lbaint_t start, lbaint_t blkcnt, void
> > > > *buffer) +{
> > > > +	block_dev_desc_t *pdev = &(sata_dev_desc[dev]);
> > > > +	int fd = (long) pdev->priv;
> > > > +	lbaint_t retval;
> > > > +
> > > > +	os_lseek(fd, start*ATA_SECT_SIZE, OS_SEEK_SET);
> > > 
> > > Besides, lseek can fail, can it not?
> > 
> > If you open a pipe (or nothing), yes
> > in the first case, you shouldn't
> 
> Shouldn't ... what? Sorry, I cannot parse this.

shouldn't do that - means i agree there should be a check in case you are 
actively trying to break things, and use pipes/sockets as loop blocks

> > in the second, the I/O op will harmlessly
> > fail as well
> 
> How so?

because then the fd is -1, and read/write will do the right thing there 
(nothing, return -1 and set errno to EBADF)

> > > > +	if (namelen > 20)
> > > > +		namelen = 20;
> > > 
> > > Why do you trim down the string, won't simple strdup() work?
> > 
> > nah, the destination is char[21], as it is the exact length of
> > corresponding field in ATA identify response (one more for a 0 at the end)
> 
> I see, is it a full path ? If so, it might be a better idea to use the
> filename itself instead of the whole path. So you'd prevent names like
> "~/../foo/../.././bar.img" .

yes, i was thinking about "...${last 17 bytes of the name}" if the name was 
longer, but this proved significantly simpler for demonstrating the general 
idea.

> > > > +	memcpy(pdev->product, filenames[dev], namelen);
> > > > +	pdev->product[20] = 0;
> > > > +
> > > > +	if (fd != -1) {
> > > 
> > > And if "fd" is -1 ?
> > 
> > then all defaults to an invalid device, because you failed to open the
> > file, for whatever the reason.
> 
> At least the printf below will choke, since pdev->lba is uninited

not the case. sata_dev_desc is inited in cmd_sata.c, and therefore by not 
doing anything we get an empty device

Best Regards
Pavel Herrmann