[PATCH v2 1/2] powerpc/tpm: Create linux,sml-base/size as big endian

[Stefan Berger]

On 7/10/23 17:23, Jarkko Sakkinen wrote:
> On Thu, 2023-06-15 at 22:37 +1000, Michael Ellerman wrote:
>> There's code in prom_instantiate_sml() to do a "SML handover" (Stored
>> Measurement Log) from OF to Linux, before Linux shuts down Open
>> Firmware.
>>
>> This involves creating a buffer to hold the SML, and creating two device
>> tree properties to record its base address and size. The kernel then
>> later reads those properties from the device tree to find the SML.
>>
>> When the code was initially added in commit 4a727429abec ("PPC64: Add
>> support for instantiating SML from Open Firmware") the powerpc kernel
>> was always built big endian, so the properties were created big endian
>> by default.
>>
>> However since then little endian support was added to powerpc, and now
>> the code lacks conversions to big endian when creating the properties.
>>
>> This means on little endian kernels the device tree properties are
>> little endian, which is contrary to the device tree spec, and in
>> contrast to all other device tree properties.
>>
>> To cope with that a workaround was added in tpm_read_log_of() to skip
>> the endian conversion if the properties were created via the SML
>> handover.
>>
>> A better solution is to encode the properties as big endian as they
>> should be, and remove the workaround.
>>
>> Typically changing the encoding of a property like this would present
>> problems for kexec. However the SML is not propagated across kexec, so
>> changing the encoding of the properties is a non-issue.
>>
>> Fixes: e46e22f12b19 ("tpm: enhance read_log_of() to support Physical TPM event log")
>> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
>> Reviewed-by: Stefan Berger <stefanb at linux.ibm.com>
>> ---
>>   arch/powerpc/kernel/prom_init.c |  8 ++++++--
>>   drivers/char/tpm/eventlog/of.c  | 23 ++++-------------------
>>   2 files changed, 10 insertions(+), 21 deletions(-)
> 
> Split into two patches (producer and consumer).

I think this wouldn't be right since it would break the system when only one patch is applied since it would be reading the fields in the wrong endianess.

     Stefan
> 
> BR, Jarkko
> 
>>
>> v2: Add Stefan's reviewed-by.
>>
>> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
>> index d464ba412084..72fe306b6820 100644
>> --- a/arch/powerpc/kernel/prom_init.c
>> +++ b/arch/powerpc/kernel/prom_init.c
>> @@ -1900,6 +1900,7 @@ static void __init prom_instantiate_sml(void)
>>   	u32 entry = 0, size = 0, succ = 0;
>>   	u64 base;
>>   	__be32 val;
>> +	__be64 val64;
>>   
>>   	prom_debug("prom_instantiate_sml: start...\n");
>>   
>> @@ -1956,10 +1957,13 @@ static void __init prom_instantiate_sml(void)
>>   
>>   	reserve_mem(base, size);
>>   
>> +	val64 = cpu_to_be64(base);
>>   	prom_setprop(ibmvtpm_node, "/vdevice/vtpm", "linux,sml-base",
>> -		     &base, sizeof(base));
>> +		     &val64, sizeof(val64));
>> +
>> +	val = cpu_to_be32(size);
>>   	prom_setprop(ibmvtpm_node, "/vdevice/vtpm", "linux,sml-size",
>> -		     &size, sizeof(size));
>> +		     &val, sizeof(val));
>>   
>>   	prom_debug("sml base     = 0x%llx\n", base);
>>   	prom_debug("sml size     = 0x%x\n", size);
>> diff --git a/drivers/char/tpm/eventlog/of.c b/drivers/char/tpm/eventlog/of.c
>> index 930fe43d5daf..0bc0cb6333c6 100644
>> --- a/drivers/char/tpm/eventlog/of.c
>> +++ b/drivers/char/tpm/eventlog/of.c
>> @@ -51,8 +51,8 @@ static int tpm_read_log_memory_region(struct tpm_chip *chip)
>>   int tpm_read_log_of(struct tpm_chip *chip)
>>   {
>>   	struct device_node *np;
>> -	const u32 *sizep;
>> -	const u64 *basep;
>> +	const __be32 *sizep;
>> +	const __be64 *basep;
>>   	struct tpm_bios_log *log;
>>   	u32 size;
>>   	u64 base;
>> @@ -73,23 +73,8 @@ int tpm_read_log_of(struct tpm_chip *chip)
>>   	if (sizep == NULL || basep == NULL)
>>   		return -EIO;
>>   
>> -	/*
>> -	 * For both vtpm/tpm, firmware has log addr and log size in big
>> -	 * endian format. But in case of vtpm, there is a method called
>> -	 * sml-handover which is run during kernel init even before
>> -	 * device tree is setup. This sml-handover function takes care
>> -	 * of endianness and writes to sml-base and sml-size in little
>> -	 * endian format. For this reason, vtpm doesn't need conversion
>> -	 * but physical tpm needs the conversion.
>> -	 */
>> -	if (of_property_match_string(np, "compatible", "IBM,vtpm") < 0 &&
>> -	    of_property_match_string(np, "compatible", "IBM,vtpm20") < 0) {
>> -		size = be32_to_cpup((__force __be32 *)sizep);
>> -		base = be64_to_cpup((__force __be64 *)basep);
>> -	} else {
>> -		size = *sizep;
>> -		base = *basep;
>> -	}
>> +	size = be32_to_cpup(sizep);
>> +	base = be64_to_cpup(basep);
>>   
>>   	if (size == 0) {
>>   		dev_warn(&chip->dev, "%s: Event log area empty\n", __func__);
>