Subject: Re: [PATCH 2/2] tpm: of: If available Use linux,sml-log to get the log and its size

From: Michael Ellerman <[email-masked]>
Date: Thu, 07 Mar 2024 21:42:59 +1100

Stefan Berger <[email-masked]> writes:
> If linux,sml-log is available use it to get the TPM log rather than the
> pointer found in linux,sml-base. This resolves an issue on PowerVM and KVM
> on Power where after a kexec the memory pointed to by linux,sml-base may
> have been corrupted. Also, linux,sml-log has replaced linux,sml-base and
> linux,sml-size on these two platforms.

It would be good to mention that powernv platforms (sometimes called
Open Power or bare metal) still use linux,sml-base/size, via skiboot.

cheers

> Signed-off-by: Stefan Berger <[email-masked]>
> ---
>  drivers/char/tpm/eventlog/of.c | 36 +++++++++++-----------------------
>  1 file changed, 11 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/char/tpm/eventlog/of.c b/drivers/char/tpm/eventlog/of.c
> index 930fe43d5daf..e37196e64ef1 100644
> --- a/drivers/char/tpm/eventlog/of.c
> +++ b/drivers/char/tpm/eventlog/of.c
> @@ -54,8 +54,8 @@ int tpm_read_log_of(struct tpm_chip *chip)
>  	const u32 *sizep;
>  	const u64 *basep;
>  	struct tpm_bios_log *log;
> +	const void *logp;
>  	u32 size;
> -	u64 base;
>  
>  	log = &chip->log;
>  	if (chip->dev.parent && chip->dev.parent->of_node)
> @@ -66,37 +66,23 @@ int tpm_read_log_of(struct tpm_chip *chip)
>  	if (of_property_read_bool(np, "powered-while-suspended"))
>  		chip->flags |= TPM_CHIP_FLAG_ALWAYS_POWERED;
>  
> -	sizep = of_get_property(np, "linux,sml-size", NULL);
> -	basep = of_get_property(np, "linux,sml-base", NULL);
> -	if (sizep == NULL && basep == NULL)
> -		return tpm_read_log_memory_region(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) {
> +	logp = of_get_property(np, "linux,sml-log", &size);
> +	if (logp == NULL) {
> +		sizep = of_get_property(np, "linux,sml-size", NULL);
> +		basep = of_get_property(np, "linux,sml-base", NULL);
> +		if (sizep == NULL && basep == NULL)
> +			return tpm_read_log_memory_region(chip);
> +		if (sizep == NULL || basep == NULL)
> +			return -EIO;
> +		logp = __va(be64_to_cpup((__force __be64 *)basep));
>  		size = be32_to_cpup((__force __be32 *)sizep);
> -		base = be64_to_cpup((__force __be64 *)basep);
> -	} else {
> -		size = *sizep;
> -		base = *basep;
>  	}
> -
>  	if (size == 0) {
>  		dev_warn(&chip->dev, "%s: Event log area empty\n", __func__);
>  		return -EIO;
>  	}
>  
> -	log->bios_event_log = devm_kmemdup(&chip->dev, __va(base), size, GFP_KERNEL);
> +	log->bios_event_log = devm_kmemdup(&chip->dev, logp, size, GFP_KERNEL);
>  	if (!log->bios_event_log)
>  		return -ENOMEM;
>  
> -- 
> 2.43.0