Re: [PATCH v10 3/8] powerpc: Move ima buffer functions to drivers/of/kexec.c

[Lakshmi Ramasubramanian]

On 12/5/20 11:48 AM, Thiago Jung Bauermann wrote:
> Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx> writes:
>
> > The functions do_get_kexec_buffer() and get_addr_size_cells(),
> > defined in arch/powerpc/kexec/ima.c, retrieve the address and size
> > of the given property from the device tree blob. These functions do
> > not have architecture specific code, but are currently limited to
> > powerpc. do_get_kexec_buffer() correctly handles a device tree property
> > that is a child node of the root node, but not anything other than
> > the immediate root child nodes.
> >
> > Move architecture independent functions get_ima_kexec_buffer() and
> > get_root_addr_size_cells() to "drivers/of/kexec.c". These functions
> > retrieve the chosen node "linux,ima-kexec-buffer" from the device tree,
> > and return the address and size of the buffer used for carrying forward
> > the IMA measurement log across kexec system call.
> >
> > Co-developed-by: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Prakhar Srivastava <prsriva@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Lakshmi Ramasubramanian <nramas@xxxxxxxxxxxxxxxxxxx>
>
> I'd personally squash this patch with the next one, but I'll leave it
> just as a suggestion since maintainers are the ones who know best what
> works well in this regard.
>
> The code is good, except for a nit below:
>
> Reviewed-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>

Thanks Thiago.

I'll remove "extern" key word in function declarations when I update the 
patch.

 -lakshmi

> > ---
> >   drivers/of/kexec.c    | 70 +++++++++++++++++++++++++++++++++++++++++++
> >   include/linux/kexec.h |  3 ++
> >   2 files changed, 73 insertions(+)
> >
> > diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> > index b7d59105fcb8..516b86f7113a 100644
> > --- a/drivers/of/kexec.c
> > +++ b/drivers/of/kexec.c
> > @@ -59,3 +59,73 @@ int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size)
> >   
> >   	return -ENOENT;
> >   }
> > +
> > +/**
> > + * get_root_addr_size_cells - Get address and size of root node
> > + *
> > + * @addr_cells: Return address of the root node
> > + * @size_cells: Return size of the root node
> > + *
> > + * Return: 0 on success, or negative errno on error.
> > + */
> > +int get_root_addr_size_cells(int *addr_cells, int *size_cells)
> > +{
> > +	struct device_node *root;
> > +
> > +	if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
> > +		return -EOPNOTSUPP;
> > +
> > +	root = of_find_node_by_path("/");
> > +	if (!root)
> > +		return -EINVAL;
> > +
> > +	*addr_cells = of_n_addr_cells(root);
> > +	*size_cells = of_n_size_cells(root);
> > +
> > +	of_node_put(root);
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * get_ima_kexec_buffer - Get address and size of IMA kexec buffer
> > + *
> > + * @fdt: Flattened Device Tree
> > + * @chosen_node: Offset of chosen node in the FDT
> > + * @addr: Return address of the node
> > + * @size: Return size of the node
> > + *
> > + * Return: 0 on success, or negative errno on error.
> > + */
> > +int get_ima_kexec_buffer(void *fdt, int chosen_node,
> > +			 unsigned long *addr, size_t *size)
> > +{
> > +	const void *prop;
> > +	int addr_cells, size_cells, prop_len;
> > +	int rc;
> > +
> > +	if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
> > +		return -EOPNOTSUPP;
> > +
> > +	rc = get_root_addr_size_cells(&addr_cells, &size_cells);
> > +	if (rc)
> > +		return rc;
> > +
> > +	if (fdt)
> > +		prop = fdt_getprop(fdt, chosen_node,
> > +				   "linux,ima-kexec-buffer", &prop_len);
> > +	else
> > +		prop = of_get_property(of_chosen,
> > +				       "linux,ima-kexec-buffer", &prop_len);
> > +
> > +	if (!prop)
> > +		return -ENOENT;
> > +
> > +	if (prop_len < 4 * (addr_cells + size_cells))
> > +		return -EINVAL;
> > +
> > +	*addr = of_read_number(prop, addr_cells);
> > +	*size = of_read_number(prop + 4 * addr_cells, size_cells);
> > +
> > +	return 0;
> > +}
> > diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> > index d0234c4815da..10ff704ab670 100644
> > --- a/include/linux/kexec.h
> > +++ b/include/linux/kexec.h
> > @@ -408,6 +408,9 @@ static inline int kexec_crash_loaded(void) { return 0; }
> >   #endif /* CONFIG_KEXEC_CORE */
> >   
> >   #if defined(CONFIG_OF_FLATTREE)
> > +extern int get_root_addr_size_cells(int *addr_cells, int *size_cells);
> > +extern int get_ima_kexec_buffer(void *fdt, int chosen_node,
> > +				unsigned long *addr, size_t *size);
> >   extern int delete_fdt_mem_rsv(void *fdt, unsigned long start,
> >   			      unsigned long size);
> >   #endif /* CONFIG_OF_FLATTREE */
>
> The extern keyword on function prototypes doesn't have any meaning.
> It's better to drop them (I should have mentioned this on the previous
> patch as well).