[PATCH v1] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

[PATCH v1] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

[Kuppuswamy Sathyanarayanan]

The Confidential Computing Event Log (CCEL) table provides the address
and length of the CCEL records area in UEFI reserved memory. To access
these records, userspace can use /dev/mem to retrieve them. But
'/dev/mem' is not enabled on many systems for security reasons.

So to allow user space access these event log records without the
/dev/mem interface, add support to access it via sysfs interface. The
ACPI driver has provided read only access to BERT records area via
'/sys/firmware/acpi/tables/data/BERT' in sysfs. So follow the same way,
and add support for /sys/firmware/acpi/tables/data/CCEL to enable
read-only access to the CCEL recorids area.

More details about the CCEL table can be found in ACPI specification
r6.5, sec titled "CC Event Log ACPI Table".

Original-patch-by: Haibo Xu <haibo1.xu@intel.com>
[Original patch is for TDEL table, modified it for CCEL support]
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 drivers/acpi/sysfs.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index 7db3b530279b..afeac925b31b 100644
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -458,11 +458,28 @@ static int acpi_bert_data_init(void *th, struct acpi_data_attr *data_attr)
 	return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
 }
 
+static int acpi_ccel_data_init(void *th, struct acpi_data_attr *data_attr)
+{
+	struct acpi_table_ccel *ccel = th;
+
+	if (ccel->header.length < sizeof(struct acpi_table_ccel) ||
+	    !(ccel->log_area_start_address) || !(ccel->log_area_minimum_length)) {
+		kfree(data_attr);
+		return -EINVAL;
+	}
+	data_attr->addr = ccel->log_area_start_address;
+	data_attr->attr.size = ccel->log_area_minimum_length;
+	data_attr->attr.attr.name = "CCEL";
+
+	return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
+}
+
 static struct acpi_data_obj {
 	char *name;
 	int (*fn)(void *, struct acpi_data_attr *);
 } acpi_data_objs[] = {
 	{ ACPI_SIG_BERT, acpi_bert_data_init },
+	{ ACPI_SIG_CCEL, acpi_ccel_data_init },
 };
 
 #define NUM_ACPI_DATA_OBJS ARRAY_SIZE(acpi_data_objs)
-- 
2.34.1

Re: [PATCH v1] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

[Sathyanarayanan Kuppuswamy]

Hi Rafael,

Gentle ping! Any comments on this patch?

On 3/1/23 11:13 PM, Kuppuswamy Sathyanarayanan wrote:
> The Confidential Computing Event Log (CCEL) table provides the address
> and length of the CCEL records area in UEFI reserved memory. To access
> these records, userspace can use /dev/mem to retrieve them. But
> '/dev/mem' is not enabled on many systems for security reasons.
> 
> So to allow user space access these event log records without the
> /dev/mem interface, add support to access it via sysfs interface. The
> ACPI driver has provided read only access to BERT records area via
> '/sys/firmware/acpi/tables/data/BERT' in sysfs. So follow the same way,
> and add support for /sys/firmware/acpi/tables/data/CCEL to enable
> read-only access to the CCEL recorids area.
> 
> More details about the CCEL table can be found in ACPI specification
> r6.5, sec titled "CC Event Log ACPI Table".
> 
> Original-patch-by: Haibo Xu <haibo1.xu@intel.com>
> [Original patch is for TDEL table, modified it for CCEL support]
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> ---
>  drivers/acpi/sysfs.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
> index 7db3b530279b..afeac925b31b 100644
> --- a/drivers/acpi/sysfs.c
> +++ b/drivers/acpi/sysfs.c
> @@ -458,11 +458,28 @@ static int acpi_bert_data_init(void *th, struct acpi_data_attr *data_attr)
>  	return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
>  }
>  
> +static int acpi_ccel_data_init(void *th, struct acpi_data_attr *data_attr)
> +{
> +	struct acpi_table_ccel *ccel = th;
> +
> +	if (ccel->header.length < sizeof(struct acpi_table_ccel) ||
> +	    !(ccel->log_area_start_address) || !(ccel->log_area_minimum_length)) {
> +		kfree(data_attr);
> +		return -EINVAL;
> +	}
> +	data_attr->addr = ccel->log_area_start_address;
> +	data_attr->attr.size = ccel->log_area_minimum_length;
> +	data_attr->attr.attr.name = "CCEL";
> +
> +	return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
> +}
> +
>  static struct acpi_data_obj {
>  	char *name;
>  	int (*fn)(void *, struct acpi_data_attr *);
>  } acpi_data_objs[] = {
>  	{ ACPI_SIG_BERT, acpi_bert_data_init },
> +	{ ACPI_SIG_CCEL, acpi_ccel_data_init },
>  };
>  
>  #define NUM_ACPI_DATA_OBJS ARRAY_SIZE(acpi_data_objs)

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer

Re: [PATCH v1] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

[Rafael J. Wysocki]

On Thu, Mar 2, 2023 at 8:13 AM Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
>
> The Confidential Computing Event Log (CCEL) table provides the address
> and length of the CCEL records area in UEFI reserved memory. To access
> these records, userspace can use /dev/mem to retrieve them. But
> '/dev/mem' is not enabled on many systems for security reasons.
>
> So to allow user space access these event log records without the
> /dev/mem interface, add support to access it via sysfs interface. The
> ACPI driver has provided read only access to BERT records area via
> '/sys/firmware/acpi/tables/data/BERT' in sysfs. So follow the same way,
> and add support for /sys/firmware/acpi/tables/data/CCEL to enable
> read-only access to the CCEL recorids area.
>
> More details about the CCEL table can be found in ACPI specification
> r6.5, sec titled "CC Event Log ACPI Table".
>
> Original-patch-by: Haibo Xu <haibo1.xu@intel.com>
> [Original patch is for TDEL table, modified it for CCEL support]
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> ---
>  drivers/acpi/sysfs.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
> index 7db3b530279b..afeac925b31b 100644
> --- a/drivers/acpi/sysfs.c
> +++ b/drivers/acpi/sysfs.c
> @@ -458,11 +458,28 @@ static int acpi_bert_data_init(void *th, struct acpi_data_attr *data_attr)
>         return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
>  }
>
> +static int acpi_ccel_data_init(void *th, struct acpi_data_attr *data_attr)
> +{
> +       struct acpi_table_ccel *ccel = th;
> +
> +       if (ccel->header.length < sizeof(struct acpi_table_ccel) ||
> +           !(ccel->log_area_start_address) || !(ccel->log_area_minimum_length)) {

The inner parens in this line are not necessary AFAICS.

Otherwise I have no objections.

> +               kfree(data_attr);
> +               return -EINVAL;
> +       }
> +       data_attr->addr = ccel->log_area_start_address;
> +       data_attr->attr.size = ccel->log_area_minimum_length;
> +       data_attr->attr.attr.name = "CCEL";
> +
> +       return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
> +}
> +
>  static struct acpi_data_obj {
>         char *name;
>         int (*fn)(void *, struct acpi_data_attr *);
>  } acpi_data_objs[] = {
>         { ACPI_SIG_BERT, acpi_bert_data_init },
> +       { ACPI_SIG_CCEL, acpi_ccel_data_init },
>  };
>
>  #define NUM_ACPI_DATA_OBJS ARRAY_SIZE(acpi_data_objs)
> --

Re: [PATCH v1] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

[Sathyanarayanan Kuppuswamy]

Hi Rafael,

On 3/20/23 10:15 AM, Rafael J. Wysocki wrote:
> On Thu, Mar 2, 2023 at 8:13 AM Kuppuswamy Sathyanarayanan
> <sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
>>
>> The Confidential Computing Event Log (CCEL) table provides the address
>> and length of the CCEL records area in UEFI reserved memory. To access
>> these records, userspace can use /dev/mem to retrieve them. But
>> '/dev/mem' is not enabled on many systems for security reasons.
>>
>> So to allow user space access these event log records without the
>> /dev/mem interface, add support to access it via sysfs interface. The
>> ACPI driver has provided read only access to BERT records area via
>> '/sys/firmware/acpi/tables/data/BERT' in sysfs. So follow the same way,
>> and add support for /sys/firmware/acpi/tables/data/CCEL to enable
>> read-only access to the CCEL recorids area.
>>
>> More details about the CCEL table can be found in ACPI specification
>> r6.5, sec titled "CC Event Log ACPI Table".
>>
>> Original-patch-by: Haibo Xu <haibo1.xu@intel.com>
>> [Original patch is for TDEL table, modified it for CCEL support]
>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
>> ---
>>  drivers/acpi/sysfs.c | 17 +++++++++++++++++
>>  1 file changed, 17 insertions(+)
>>
>> diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
>> index 7db3b530279b..afeac925b31b 100644
>> --- a/drivers/acpi/sysfs.c
>> +++ b/drivers/acpi/sysfs.c
>> @@ -458,11 +458,28 @@ static int acpi_bert_data_init(void *th, struct acpi_data_attr *data_attr)
>>         return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
>>  }
>>
>> +static int acpi_ccel_data_init(void *th, struct acpi_data_attr *data_attr)
>> +{
>> +       struct acpi_table_ccel *ccel = th;
>> +
>> +       if (ccel->header.length < sizeof(struct acpi_table_ccel) ||
>> +           !(ccel->log_area_start_address) || !(ccel->log_area_minimum_length)) {
> 
> The inner parens in this line are not necessary AFAICS.
> 
> Otherwise I have no objections.

Yes. We can do without it. Shall I submit v2 with this change, or you want to
fix it when applying?

> 
>> +               kfree(data_attr);
>> +               return -EINVAL;
>> +       }
>> +       data_attr->addr = ccel->log_area_start_address;
>> +       data_attr->attr.size = ccel->log_area_minimum_length;
>> +       data_attr->attr.attr.name = "CCEL";
>> +
>> +       return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
>> +}
>> +
>>  static struct acpi_data_obj {
>>         char *name;
>>         int (*fn)(void *, struct acpi_data_attr *);
>>  } acpi_data_objs[] = {
>>         { ACPI_SIG_BERT, acpi_bert_data_init },
>> +       { ACPI_SIG_CCEL, acpi_ccel_data_init },
>>  };
>>
>>  #define NUM_ACPI_DATA_OBJS ARRAY_SIZE(acpi_data_objs)
>> --

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer

Re: [PATCH v1] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

[Rafael J. Wysocki]

On Mon, Mar 20, 2023 at 6:34 PM Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
>
> Hi Rafael,
>
> On 3/20/23 10:15 AM, Rafael J. Wysocki wrote:
> > On Thu, Mar 2, 2023 at 8:13 AM Kuppuswamy Sathyanarayanan
> > <sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
> >>
> >> The Confidential Computing Event Log (CCEL) table provides the address
> >> and length of the CCEL records area in UEFI reserved memory. To access
> >> these records, userspace can use /dev/mem to retrieve them. But
> >> '/dev/mem' is not enabled on many systems for security reasons.
> >>
> >> So to allow user space access these event log records without the
> >> /dev/mem interface, add support to access it via sysfs interface. The
> >> ACPI driver has provided read only access to BERT records area via
> >> '/sys/firmware/acpi/tables/data/BERT' in sysfs. So follow the same way,
> >> and add support for /sys/firmware/acpi/tables/data/CCEL to enable
> >> read-only access to the CCEL recorids area.
> >>
> >> More details about the CCEL table can be found in ACPI specification
> >> r6.5, sec titled "CC Event Log ACPI Table".
> >>
> >> Original-patch-by: Haibo Xu <haibo1.xu@intel.com>
> >> [Original patch is for TDEL table, modified it for CCEL support]
> >> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
> >> ---
> >>  drivers/acpi/sysfs.c | 17 +++++++++++++++++
> >>  1 file changed, 17 insertions(+)
> >>
> >> diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
> >> index 7db3b530279b..afeac925b31b 100644
> >> --- a/drivers/acpi/sysfs.c
> >> +++ b/drivers/acpi/sysfs.c
> >> @@ -458,11 +458,28 @@ static int acpi_bert_data_init(void *th, struct acpi_data_attr *data_attr)
> >>         return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
> >>  }
> >>
> >> +static int acpi_ccel_data_init(void *th, struct acpi_data_attr *data_attr)
> >> +{
> >> +       struct acpi_table_ccel *ccel = th;
> >> +
> >> +       if (ccel->header.length < sizeof(struct acpi_table_ccel) ||
> >> +           !(ccel->log_area_start_address) || !(ccel->log_area_minimum_length)) {
> >
> > The inner parens in this line are not necessary AFAICS.
> >
> > Otherwise I have no objections.
>
> Yes. We can do without it. Shall I submit v2 with this change, or you want to
> fix it when applying?

I would appreciate a v2.

> >
> >> +               kfree(data_attr);
> >> +               return -EINVAL;
> >> +       }
> >> +       data_attr->addr = ccel->log_area_start_address;
> >> +       data_attr->attr.size = ccel->log_area_minimum_length;
> >> +       data_attr->attr.attr.name = "CCEL";
> >> +
> >> +       return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
> >> +}
> >> +
> >>  static struct acpi_data_obj {
> >>         char *name;
> >>         int (*fn)(void *, struct acpi_data_attr *);
> >>  } acpi_data_objs[] = {
> >>         { ACPI_SIG_BERT, acpi_bert_data_init },
> >> +       { ACPI_SIG_CCEL, acpi_ccel_data_init },
> >>  };
> >>
> >>  #define NUM_ACPI_DATA_OBJS ARRAY_SIZE(acpi_data_objs)
> >> --
>
> --