Date:   Wed, 16 Dec 2020 08:58:00 -0800
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Rob Herring <robh@...nel.org>
Cc:     zohar@...ux.ibm.com, bauerman@...ux.ibm.com,
        takahiro.akashi@...aro.org, gregkh@...uxfoundation.org,
        will@...nel.org, catalin.marinas@....com, mpe@...erman.id.au,
        james.morse@....com, sashal@...nel.org, benh@...nel.crashing.org,
        paulus@...ba.org, frowand.list@...il.com,
        vincenzo.frascino@....com, mark.rutland@....com,
        dmitry.kasatkin@...il.com, jmorris@...ei.org, serge@...lyn.com,
        pasha.tatashin@...een.com, allison@...utok.net,
        masahiroy@...nel.org, bhsharma@...hat.com, mbrugger@...e.com,
        hsinyi@...omium.org, tao.li@...o.com, christophe.leroy@....fr,
        prsriva@...ux.microsoft.com, balajib@...ux.microsoft.com,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v11 2/8] powerpc: Move ima buffer functions to
 drivers/of/kexec.c

On 12/15/20 10:16 AM, Rob Herring wrote:
> On Mon, Dec 14, 2020 at 11:18:48AM -0800, Lakshmi Ramasubramanian wrote:
>> 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@...ux.microsoft.com>
>> Signed-off-by: Prakhar Srivastava <prsriva@...ux.microsoft.com>
>> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
>> ---
>>   drivers/of/kexec.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++
>>   include/linux/of.h |  3 ++
>>   2 files changed, 71 insertions(+)
>>
>> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
>> index 66787be081fe..9af5371340b1 100644
>> --- a/drivers/of/kexec.c
>> +++ b/drivers/of/kexec.c
>> @@ -30,6 +30,10 @@
>>   /**
>>    * fdt_find_and_del_mem_rsv - delete memory reservation with given address and size
>>    *
>> + * @fdt: Flattened Device Tree to update
>> + * @start: Starting address of the reservation to delete
>> + * @size: Size of the reservation to delete
>> + *
> 
> This belongs in the patch adding fdt_find_and_del_mem_rsv.

Yes.

> 
>>    * Return: 0 on success, or negative errno on error.
>>    */
>>   static int fdt_find_and_del_mem_rsv(void *fdt, unsigned long start, unsigned long size)
>> @@ -226,3 +230,67 @@ int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
>>   
>>   	return 0;
>>   }
>> +
>> +/**
>> + * 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;
>> +
>> +	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;
>> +
>> +	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);
> 
> This is an odd structure. The DT APIs are generally of_foo() for
> unflattened tree and of_flat_foo() for FDT.
> 
Ok - will update.

>> +
>> +	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/of.h b/include/linux/of.h
>> index 3375f5295875..fb2ef274135d 100644
>> --- a/include/linux/of.h
>> +++ b/include/linux/of.h
>> @@ -562,6 +562,9 @@ struct kimage;
>>   int of_kexec_setup_new_fdt(const struct kimage *image, void *fdt,
>>   			   unsigned long initrd_load_addr, unsigned long initrd_len,
>>   			   const char *cmdline);
>> +int get_root_addr_size_cells(int *addr_cells, int *size_cells);
>> +int get_ima_kexec_buffer(void *fdt, int chosen_node,
>> +			 unsigned long *addr, size_t *size);
> 
> The whole point of moving code out of arch code was to avoid all these
> cross tree calls.
> 
> I was expecting the next step to be moving setup_ima_buffer() call into
> of_kexec_setup_new_fdt with all the code in powerpc/kexec/ima.c moved
> here. Then the end result to enable on arm64 is just selecting
> HAVE_IMA_KEXEC and adding fields to kimage_arch.
> 

setup_ima_buffer() implemented for powerpc can be simplified by using
fdt_appendprop_addrrange() to add the IMA buffer's address and size to 
"linux,ima-kexec-buffer" node. With that change, setup_ima_buffer() can 
be moved into of_kexec_setup_new_fdt along with all the code in 
powerpc/kexec/ima.c to drivers'of/kexec.c

I'll make the above change and post the next version shortly.

thanks,
  -lakshmi

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