efi/x86: Expose number of entries in the EFI configuration table via sysfs
PATCH 1/1 efi/x86: Expose number of entries in the EFI configuration table via sysfs
Currently Linux exposes the physical address of the EFI configuration table via sysfs, but not the number of entries.
The number of entries for the EFI configuration table is located in the EFI system table and the EFI system table is not exposed, so there is no way for a userspace application to reliably navigate the EFI configuration table.
One potential use case for such a userspace program would be a monitoring agent, which parses Image Execution Information Table from the EFI configuration table and reports all the UEFI executables, which have been denied execution due to the enforced Secure Boot policy thus providing intrusion detection capabilities.
--- Documentation/ABI/testing/sysfs-firmware-efi | 12 +++++++++- arch/x86/platform/efi/efi.c | 24 +++++++++++++++----- drivers/firmware/efi/efi.c | 2 ++ 3 files changed, 31 insertions(+), 7 deletions(-)
Documentation/ABI/testing/sysfs-firmware-efi +11 -1
@@ -17,7 +17,9 @@ Date: December 2013 Contact: Dave Young <[email protected]> Description: It shows the physical address of config table entry in the EFI system table. -Users: Kexec +Users: Kexec, userspace tools for reading information from UEFI + configuration table (for example, Image Execution Information + Table) What: /sys/firmware/efi/systab Date: April 2005
@@ -36,3 +38,11 @@ Description: Displays the content of the Runtime Configuration Interface Table version 2 on Dell EMC PowerEdge systems in binary format Users: It is used by Dell EMC OpenManage Server Administrator tool to populate BIOS setup page. + +What: /sys/firmware/efi/nr_tables +Date: April 2020 +Contact: [email protected] +Description: It shows number of entries in the config table entry in the EFI + system table. +Users: Userspace tools for reading information from UEFI configuration + table (for example, Image Execution Information Table)
arch/x86/platform/efi/efi.c +18 -6
@@ -57,9 +57,9 @@static unsigned long efi_systab_phys__initdata ;static unsigned long prop_phys =EFI_INVALID_TABLE_ADDR ;static unsigned long uga_phys =EFI_INVALID_TABLE_ADDR ; -static unsigned long efi_runtime, efi_nr_tables; +static unsigned long efi_runtime; -unsigned long efi_fw_vendor, efi_config_table; +unsigned long efi_fw_vendor, efi_config_table, efi_nr_tables;static const efi_config_table_type_t arch_tables[]__initconst = { {EFI_PROPERTIES_TABLE_GUID ,"PROP" , &prop_phys},
@@ -963,20 +963,29 @@ char *efi_systab_show_arch(char *str)#define EFI_FIELD (var) efi_ ## var -#define EFI_ATTR_SHOW (name) \ +#define EFI_ATTR_SHOW_ADDR (name) \ static ssize_t name##_show(struct kobject *kobj, \ struct kobj_attribute *attr, char *buf) \ { \ return sprintf(buf, "0x%lx\n", EFI_FIELD(name)); \ } -EFI_ATTR_SHOW (fw_vendor); -EFI_ATTR_SHOW (runtime); -EFI_ATTR_SHOW (config_table); +#define EFI_ATTR_SHOW_ULONG (name) \ +static ssize_t name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, char *buf) \ +{ \ + return sprintf(buf, "%lu\n", EFI_FIELD(name)); \ +} + +EFI_ATTR_SHOW_ADDR (fw_vendor); +EFI_ATTR_SHOW_ADDR (runtime); +EFI_ATTR_SHOW_ADDR (config_table); +EFI_ATTR_SHOW_ULONG (nr_tables);struct kobj_attribute efi_attr_fw_vendor =__ATTR_RO (fw_vendor);struct kobj_attribute efi_attr_runtime =__ATTR_RO (runtime);struct kobj_attribute efi_attr_config_table =__ATTR_RO (config_table); +struct kobj_attribute efi_attr_nr_tables =__ATTR_RO (nr_tables);umode_t efi_attr_is_visible (struct kobject *kobj,struct attribute *attr,int n) {
@@ -990,6 +999,9 @@ umode_t efi_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n) }else if (attr == &efi_attr_config_table.attr) {if (efi_config_table ==EFI_INVALID_TABLE_ADDR )return 0 ; + }else if (attr == &efi_attr_nr_tables.attr) { +if (efi_config_table ==EFI_INVALID_TABLE_ADDR ) +return 0 ; }return attr->mode; }
drivers/firmware/efi/efi.c +2 -0
@@ -150,6 +150,7 @@ static ssize_t fw_platform_size_show(struct kobject *kobj,extern __weak struct kobj_attribute efi_attr_fw_vendor;extern __weak struct kobj_attribute efi_attr_runtime;extern __weak struct kobj_attribute efi_attr_config_table; +extern __weak struct kobj_attribute efi_attr_nr_tables;static struct kobj_attribute efi_attr_fw_platform_size =__ATTR_RO (fw_platform_size);
@@ -159,6 +160,7 @@ static struct attribute *efi_subsys_attrs[] = { &efi_attr_fw_vendor.attr, &efi_attr_runtime.attr, &efi_attr_config_table.attr, + &efi_attr_nr_tables.attr, NULL, };
Signature · 1 line
2.20.1
Ard Biesheuvel
maintainerHello Ignat,
Thanks for the patch.
Quoted 4 lines · Ignat Korchagin
Currently Linux exposes the physical address of the EFI configuration table via sysfs, but not the number of entries.
It does so on x86 only, and the purpose is specifically defined as kexec. This is for a good reason: kexec on x86 EFI machines has accumulated some historical quirks dealing with issues that do not exist on other architectures.
Quoted 9 lines
The number of entries for the EFI configuration table is located in the EFI system table and the EFI system table is not exposed, so there is no way for a userspace application to reliably navigate the EFI configuration table.
One potential use case for such a userspace program would be a monitoring agent, which parses Image Execution Information Table from the EFI configuration table and reports all the UEFI executables, which have been denied execution due to the enforced Secure Boot policy thus providing intrusion detection capabilities.
Exposing a physical address via syfs and using /dev/mem to scoop up the data is not a robust, secure or portable interface, especially in the quoted context of a UEFI secure boot enabled system.
If you need to access this table from userland, I suggest we come up with a generic method that does not rely on /dev/mem. It would be even better if we could come up with some infrastructure that makes this easily extendable to other configuration tables. But simply exposing the address and size of the config table array in memory is not the right way.
Quoted 117 lines
Signed-off-by Ignat Korchagin <[email protected]>--- Documentation/ABI/testing/sysfs-firmware-efi | 12 +++++++++- arch/x86/platform/efi/efi.c | 24 +++++++++++++++----- drivers/firmware/efi/efi.c | 2 ++ 3 files changed, 31 insertions(+), 7 deletions(-)Documentation/ABI/testing/sysfs-firmware-efi +11
-1@@ -17,7 +17,9 @@ Date: December 2013 Contact: Dave Young <[email protected]> Description: It shows the physical address of config table entry in the EFI system table. -Users: Kexec +Users: Kexec, userspace tools for reading information from UEFI + configuration table (for example, Image Execution Information + Table) What: /sys/firmware/efi/systab Date: April 2005@@ -36,3 +38,11 @@ Description: Displays the content of the Runtime Configuration Interface Table version 2 on Dell EMC PowerEdge systems in binary format Users: It is used by Dell EMC OpenManage Server Administrator tool to populate BIOS setup page. + +What: /sys/firmware/efi/nr_tables +Date: April 2020 +Contact: [email protected] +Description: It shows number of entries in the config table entry in the EFI + system table. +Users: Userspace tools for reading information from UEFI configuration + table (for example, Image Execution Information Table)arch/x86/platform/efi/efi.c +18
-6@@ -57,9 +57,9 @@static unsigned long efi_systab_phys__initdata ;static unsigned long prop_phys =EFI_INVALID_TABLE_ADDR ;static unsigned long uga_phys =EFI_INVALID_TABLE_ADDR ; -static unsigned long efi_runtime, efi_nr_tables; +static unsigned long efi_runtime; -unsigned long efi_fw_vendor, efi_config_table; +unsigned long efi_fw_vendor, efi_config_table, efi_nr_tables;static const efi_config_table_type_t arch_tables[]__initconst = { {EFI_PROPERTIES_TABLE_GUID ,"PROP" , &prop_phys},@@ -963,20 +963,29 @@ char *efi_systab_show_arch(char *str)#define EFI_FIELD (var) efi_ ## var -#define EFI_ATTR_SHOW (name) \ +#define EFI_ATTR_SHOW_ADDR (name) \ static ssize_t name##_show(struct kobject *kobj, \ struct kobj_attribute *attr, char *buf) \ { \ return sprintf(buf, "0x%lx\n", EFI_FIELD(name)); \ } -EFI_ATTR_SHOW (fw_vendor); -EFI_ATTR_SHOW (runtime); -EFI_ATTR_SHOW (config_table); +#define EFI_ATTR_SHOW_ULONG (name) \ +static ssize_t name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, char *buf) \ +{ \ + return sprintf(buf, "%lu\n", EFI_FIELD(name)); \ +} + +EFI_ATTR_SHOW_ADDR (fw_vendor); +EFI_ATTR_SHOW_ADDR (runtime); +EFI_ATTR_SHOW_ADDR (config_table); +EFI_ATTR_SHOW_ULONG (nr_tables);struct kobj_attribute efi_attr_fw_vendor =__ATTR_RO (fw_vendor);struct kobj_attribute efi_attr_runtime =__ATTR_RO (runtime);struct kobj_attribute efi_attr_config_table =__ATTR_RO (config_table); +struct kobj_attribute efi_attr_nr_tables =__ATTR_RO (nr_tables);umode_t efi_attr_is_visible (struct kobject *kobj,struct attribute *attr,int n) {@@ -990,6 +999,9 @@ umode_t efi_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n) }else if (attr == &efi_attr_config_table.attr) {if (efi_config_table ==EFI_INVALID_TABLE_ADDR )return 0 ; + }else if (attr == &efi_attr_nr_tables.attr) { +if (efi_config_table ==EFI_INVALID_TABLE_ADDR ) +return 0 ; }return attr->mode; }drivers/firmware/efi/efi.c +2
-1@@ -150,6 +150,7 @@ static ssize_t fw_platform_size_show(struct kobject *kobj,extern __weak struct kobj_attribute efi_attr_fw_vendor;extern __weak struct kobj_attribute efi_attr_runtime;extern __weak struct kobj_attribute efi_attr_config_table; +extern __weak struct kobj_attribute efi_attr_nr_tables;static struct kobj_attribute efi_attr_fw_platform_size =__ATTR_RO (fw_platform_size);@@ -159,6 +160,7 @@ static struct attribute *efi_subsys_attrs[] = { &efi_attr_fw_vendor.attr, &efi_attr_runtime.attr, &efi_attr_config_table.attr, + &efi_attr_nr_tables.attr, NULL, }; --2.20.1
Quoted 26 lines · Ard Biesheuvel
Hello Ignat,
Thanks for the patch.
Quoted 4 lines · Ignat Korchagin
Currently Linux exposes the physical address of the EFI configuration table via sysfs, but not the number of entries.
It does so on x86 only, and the purpose is specifically defined as kexec. This is for a good reason: kexec on x86 EFI machines has accumulated some historical quirks dealing with issues that do not exist on other architectures.
Quoted 9 lines
The number of entries for the EFI configuration table is located in the EFI system table and the EFI system table is not exposed, so there is no way for a userspace application to reliably navigate the EFI configuration table.
One potential use case for such a userspace program would be a monitoring agent, which parses Image Execution Information Table from the EFI configuration table and reports all the UEFI executables, which have been denied execution due to the enforced Secure Boot policy thus providing intrusion detection capabilities.
Quoted 3 lines
Exposing a physical address via syfs and using
/dev/memto scoop up the data is not a robust, secure or portable interface, especially in the quoted context of a UEFI secure boot enabled system.
TBH, it is not hard to find this number by scanning the same mapped region for EFI system table (which is easily identifiable by its signature). So security is not an
issue here, although robustness and portability indeed.
Quoted 6 lines
If you need to access this table from userland, I suggest we come up with a generic method that does not rely on
/dev/mem. It would be even better if we could come up with some infrastructure that makes this easily extendable to other configuration tables. But simply exposing the address and size of the config table array in memory is not the right way.
Would you prefer something closer to the efivars filesystem then?
Quoted 117 lines
Quoted 117 lines
Signed-off-by Ignat Korchagin <[email protected]>--- Documentation/ABI/testing/sysfs-firmware-efi | 12 +++++++++- arch/x86/platform/efi/efi.c | 24 +++++++++++++++----- drivers/firmware/efi/efi.c | 2 ++ 3 files changed, 31 insertions(+), 7 deletions(-)Documentation/ABI/testing/sysfs-firmware-efi +11
-1@@ -17,7 +17,9 @@ Date: December 2013 Contact: Dave Young <[email protected]> Description: It shows the physical address of config table entry in the EFI system table. -Users: Kexec +Users: Kexec, userspace tools for reading information from UEFI + configuration table (for example, Image Execution Information + Table) What: /sys/firmware/efi/systab Date: April 2005@@ -36,3 +38,11 @@ Description: Displays the content of the Runtime Configuration Interface Table version 2 on Dell EMC PowerEdge systems in binary format Users: It is used by Dell EMC OpenManage Server Administrator tool to populate BIOS setup page. + +What: /sys/firmware/efi/nr_tables +Date: April 2020 +Contact: [email protected] +Description: It shows number of entries in the config table entry in the EFI + system table. +Users: Userspace tools for reading information from UEFI configuration + table (for example, Image Execution Information Table)arch/x86/platform/efi/efi.c +18
-6@@ -57,9 +57,9 @@static unsigned long efi_systab_phys__initdata ;static unsigned long prop_phys =EFI_INVALID_TABLE_ADDR ;static unsigned long uga_phys =EFI_INVALID_TABLE_ADDR ; -static unsigned long efi_runtime, efi_nr_tables; +static unsigned long efi_runtime; -unsigned long efi_fw_vendor, efi_config_table; +unsigned long efi_fw_vendor, efi_config_table, efi_nr_tables;static const efi_config_table_type_t arch_tables[]__initconst = { {EFI_PROPERTIES_TABLE_GUID ,"PROP" , &prop_phys},@@ -963,20 +963,29 @@ char *efi_systab_show_arch(char *str)#define EFI_FIELD (var) efi_ ## var -#define EFI_ATTR_SHOW (name) \ +#define EFI_ATTR_SHOW_ADDR (name) \ static ssize_t name##_show(struct kobject *kobj, \ struct kobj_attribute *attr, char *buf) \ { \ return sprintf(buf, "0x%lx\n", EFI_FIELD(name)); \ } -EFI_ATTR_SHOW (fw_vendor); -EFI_ATTR_SHOW (runtime); -EFI_ATTR_SHOW (config_table); +#define EFI_ATTR_SHOW_ULONG (name) \ +static ssize_t name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, char *buf) \ +{ \ + return sprintf(buf, "%lu\n", EFI_FIELD(name)); \ +} + +EFI_ATTR_SHOW_ADDR (fw_vendor); +EFI_ATTR_SHOW_ADDR (runtime); +EFI_ATTR_SHOW_ADDR (config_table); +EFI_ATTR_SHOW_ULONG (nr_tables);struct kobj_attribute efi_attr_fw_vendor =__ATTR_RO (fw_vendor);struct kobj_attribute efi_attr_runtime =__ATTR_RO (runtime);struct kobj_attribute efi_attr_config_table =__ATTR_RO (config_table); +struct kobj_attribute efi_attr_nr_tables =__ATTR_RO (nr_tables);umode_t efi_attr_is_visible (struct kobject *kobj,struct attribute *attr,int n) {@@ -990,6 +999,9 @@ umode_t efi_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n) }else if (attr == &efi_attr_config_table.attr) {if (efi_config_table ==EFI_INVALID_TABLE_ADDR )return 0 ; + }else if (attr == &efi_attr_nr_tables.attr) { +if (efi_config_table ==EFI_INVALID_TABLE_ADDR ) +return 0 ; }return attr->mode; }drivers/firmware/efi/efi.c +2
-1@@ -150,6 +150,7 @@ static ssize_t fw_platform_size_show(struct kobject *kobj,extern __weak struct kobj_attribute efi_attr_fw_vendor;extern __weak struct kobj_attribute efi_attr_runtime;extern __weak struct kobj_attribute efi_attr_config_table; +extern __weak struct kobj_attribute efi_attr_nr_tables;static struct kobj_attribute efi_attr_fw_platform_size =__ATTR_RO (fw_platform_size);@@ -159,6 +160,7 @@ static struct attribute *efi_subsys_attrs[] = { &efi_attr_fw_vendor.attr, &efi_attr_runtime.attr, &efi_attr_config_table.attr, + &efi_attr_nr_tables.attr, NULL, }; --2.20.1
Ard Biesheuvel
maintainer(+ Peter)
Quoted 37 lines · Ignat Korchagin
Quoted 26 lines · Ard Biesheuvel
Hello Ignat,
Thanks for the patch.
Quoted 4 lines · Ignat Korchagin
Currently Linux exposes the physical address of the EFI configuration table via sysfs, but not the number of entries.
It does so on x86 only, and the purpose is specifically defined as kexec. This is for a good reason: kexec on x86 EFI machines has accumulated some historical quirks dealing with issues that do not exist on other architectures.
Quoted 9 lines
The number of entries for the EFI configuration table is located in the EFI system table and the EFI system table is not exposed, so there is no way for a userspace application to reliably navigate the EFI configuration table.
One potential use case for such a userspace program would be a monitoring agent, which parses Image Execution Information Table from the EFI configuration table and reports all the UEFI executables, which have been denied execution due to the enforced Secure Boot policy thus providing intrusion detection capabilities.
Quoted 3 lines
Exposing a physical address via syfs and using
/dev/memto scoop up the data is not a robust, secure or portable interface, especially in the quoted context of a UEFI secure boot enabled system.TBH, it is not hard to find this number by scanning the same mapped region for EFI system table (which is easily identifiable by its signature). So security is not an
issue here, although robustness and portability indeed.
Quoted 9 lines
Quoted 6 lines
If you need to access this table from userland, I suggest we come up with a generic method that does not rely on
/dev/mem. It would be even better if we could come up with some infrastructure that makes this easily extendable to other configuration tables. But simply exposing the address and size of the config table array in memory is not the right way.Would you prefer something closer to the efivars filesystem then?
The problem with EFI configuration tables is that there is no standard way to discover their size. Each GUID denotes a different type of table, each of which has its own structure and layout in memory.
We already record and expose a substantial set of config tables, but perhaps it is time to add a generic layer as well. I have cc'ed Peter, which may have some observations of his own to share on this topic.
A pseudo file system might work, as long as it only exposes tables that have been explicitly registered for this, along with the size of each individual table. But then it becomes complicated if you want to expose things like ACPI or SMBIOS, which are not flat tables, but sets of tables pointing to other tables etc etc.
Quoted 27 lines · Ignat Korchagin
Quoted 26 lines · Ard Biesheuvel
Hello Ignat,
Thanks for the patch.
Quoted 4 lines · Ignat Korchagin
Currently Linux exposes the physical address of the EFI configuration table via sysfs, but not the number of entries.
It does so on x86 only, and the purpose is specifically defined as kexec. This is for a good reason: kexec on x86 EFI machines has accumulated some historical quirks dealing with issues that do not exist on other architectures.
Quoted 9 lines
The number of entries for the EFI configuration table is located in the EFI system table and the EFI system table is not exposed, so there is no way for a userspace application to reliably navigate the EFI configuration table.
One potential use case for such a userspace program would be a monitoring agent, which parses Image Execution Information Table from the EFI configuration table and reports all the UEFI executables, which have been denied execution due to the enforced Secure Boot policy thus providing intrusion detection capabilities.
Quoted 8 lines
Quoted 3 lines
Exposing a physical address via syfs and using
/dev/memto scoop up the data is not a robust, secure or portable interface, especially in the quoted context of a UEFI secure boot enabled system.TBH, it is not hard to find this number by scanning the same mapped region for EFI system table (which is easily identifiable by its signature). So security is not an
issue here, although robustness and portability indeed.
If security was an issue, /dev/mem would be disabled.
Quoted 9 lines
Quoted 7 lines
If you need to access this table from userland, I suggest we come up with a generic method that does not rely on
/dev/mem. It would be even better if we could come up with some infrastructure that makes this easily extendable to other configuration tables. But simply exposing the address and size of the config table array in memory is not the right way.Would you prefer something closer to the efivars filesystem then?
Maybe something like DMI_SYSFS?
Quoted 118 lines
Quoted 118 lines
Quoted 118 lines
Signed-off-by Ignat Korchagin <[email protected]>--- Documentation/ABI/testing/sysfs-firmware-efi | 12 +++++++++- arch/x86/platform/efi/efi.c | 24 +++++++++++++++----- drivers/firmware/efi/efi.c | 2 ++ 3 files changed, 31 insertions(+), 7 deletions(-)Documentation/ABI/testing/sysfs-firmware-efi +11
-1@@ -17,7 +17,9 @@ Date: December 2013 Contact: Dave Young <[email protected]> Description: It shows the physical address of config table entry in the EFI system table. -Users: Kexec +Users: Kexec, userspace tools for reading information from UEFI + configuration table (for example, Image Execution Information + Table) What: /sys/firmware/efi/systab Date: April 2005@@ -36,3 +38,11 @@ Description: Displays the content of the Runtime Configuration Interface Table version 2 on Dell EMC PowerEdge systems in binary format Users: It is used by Dell EMC OpenManage Server Administrator tool to populate BIOS setup page. + +What: /sys/firmware/efi/nr_tables +Date: April 2020 +Contact: [email protected] +Description: It shows number of entries in the config table entry in the EFI + system table. +Users: Userspace tools for reading information from UEFI configuration + table (for example, Image Execution Information Table)arch/x86/platform/efi/efi.c +18
-6@@ -57,9 +57,9 @@static unsigned long efi_systab_phys__initdata ;static unsigned long prop_phys =EFI_INVALID_TABLE_ADDR ;static unsigned long uga_phys =EFI_INVALID_TABLE_ADDR ; -static unsigned long efi_runtime, efi_nr_tables; +static unsigned long efi_runtime; -unsigned long efi_fw_vendor, efi_config_table; +unsigned long efi_fw_vendor, efi_config_table, efi_nr_tables;static const efi_config_table_type_t arch_tables[]__initconst = { {EFI_PROPERTIES_TABLE_GUID ,"PROP" , &prop_phys},@@ -963,20 +963,29 @@ char *efi_systab_show_arch(char *str)#define EFI_FIELD (var) efi_ ## var -#define EFI_ATTR_SHOW (name) \ +#define EFI_ATTR_SHOW_ADDR (name) \ static ssize_t name##_show(struct kobject *kobj, \ struct kobj_attribute *attr, char *buf) \ { \ return sprintf(buf, "0x%lx\n", EFI_FIELD(name)); \ } -EFI_ATTR_SHOW (fw_vendor); -EFI_ATTR_SHOW (runtime); -EFI_ATTR_SHOW (config_table); +#define EFI_ATTR_SHOW_ULONG (name) \ +static ssize_t name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, char *buf) \ +{ \ + return sprintf(buf, "%lu\n", EFI_FIELD(name)); \ +} + +EFI_ATTR_SHOW_ADDR (fw_vendor); +EFI_ATTR_SHOW_ADDR (runtime); +EFI_ATTR_SHOW_ADDR (config_table); +EFI_ATTR_SHOW_ULONG (nr_tables);struct kobj_attribute efi_attr_fw_vendor =__ATTR_RO (fw_vendor);struct kobj_attribute efi_attr_runtime =__ATTR_RO (runtime);struct kobj_attribute efi_attr_config_table =__ATTR_RO (config_table); +struct kobj_attribute efi_attr_nr_tables =__ATTR_RO (nr_tables);umode_t efi_attr_is_visible (struct kobject *kobj,struct attribute *attr,int n) {@@ -990,6 +999,9 @@ umode_t efi_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n) }else if (attr == &efi_attr_config_table.attr) {if (efi_config_table ==EFI_INVALID_TABLE_ADDR )return 0 ; + }else if (attr == &efi_attr_nr_tables.attr) { +if (efi_config_table ==EFI_INVALID_TABLE_ADDR ) +return 0 ; }return attr->mode; }drivers/firmware/efi/efi.c +2
-1@@ -150,6 +150,7 @@ static ssize_t fw_platform_size_show(struct kobject *kobj,extern __weak struct kobj_attribute efi_attr_fw_vendor;extern __weak struct kobj_attribute efi_attr_runtime;extern __weak struct kobj_attribute efi_attr_config_table; +extern __weak struct kobj_attribute efi_attr_nr_tables;static struct kobj_attribute efi_attr_fw_platform_size =__ATTR_RO (fw_platform_size);@@ -159,6 +160,7 @@ static struct attribute *efi_subsys_attrs[] = { &efi_attr_fw_vendor.attr, &efi_attr_runtime.attr, &efi_attr_config_table.attr, + &efi_attr_nr_tables.attr, NULL, }; --2.20.1