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@xxxxxxxxxxxxxx>
> Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> ---
> 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).
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__);
