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Subject: Re: [PATCH v10 3/8] powerpc: Move ima buffer functions to
 drivers/of/kexec.c
To:     Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc:     zohar@linux.ibm.com, robh@kernel.org, gregkh@linuxfoundation.org,
        james.morse@arm.com, catalin.marinas@arm.com, sashal@kernel.org,
        will@kernel.org, mpe@ellerman.id.au, benh@kernel.crashing.org,
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        vincenzo.frascino@arm.com, mark.rutland@arm.com,
        dmitry.kasatkin@gmail.com, jmorris@namei.org, serge@hallyn.com,
        pasha.tatashin@soleen.com, allison@lohutok.net,
        kstewart@linuxfoundation.org, takahiro.akashi@linaro.org,
        tglx@linutronix.de, masahiroy@kernel.org, bhsharma@redhat.com,
        mbrugger@suse.com, hsinyi@chromium.org, tao.li@vivo.com,
        christophe.leroy@c-s.fr, linux-integrity@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        prsriva@linux.microsoft.com, balajib@linux.microsoft.com
References: <20201204195149.611-1-nramas@linux.microsoft.com>
 <20201204195149.611-4-nramas@linux.microsoft.com>
 <87zh2sm3tj.fsf@manicouagan.localdomain>
From:   Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Message-ID: <0cb40d89-cc0b-25cc-479c-f8269af0346a@linux.microsoft.com>
Date:   Sun, 6 Dec 2020 17:53:10 -0800
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On 12/5/20 11:48 AM, Thiago Jung Bauermann wrote:
> 
> Lakshmi Ramasubramanian <nramas@linux.microsoft.com> 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@linux.microsoft.com>
>> Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
>> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> 
> 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@linux.ibm.com>

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).
>