Here's a set of patches that can determine the secure boot state of the
UEFI BIOS and pass that along to the main kernel image. This involves
generalising ARM's efi_get_secureboot() function and making it mixed-mode
safe.
The patches can be found here also:
http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=efi-secure-boot
at tag:
efi-secure-boot-20161123
Note that the patches are not terminal on the branch.
David
---
David Howells (4):
x86/efi: Allow invocation of arbitrary runtime services
arm/efi: Allow invocation of arbitrary runtime services
efi: Add SHIM and image security database GUID definitions
efi: Get the secure boot status
Josh Boyer (2):
efi: Disable secure boot if shim is in insecure mode
efi: Add EFI_SECURE_BOOT bit
Documentation/x86/zero-page.txt | 2 +
arch/arm/include/asm/efi.h | 1
arch/arm64/include/asm/efi.h | 1
arch/x86/boot/compressed/eboot.c | 3 +
arch/x86/boot/compressed/head_32.S | 6 +-
arch/x86/boot/compressed/head_64.S | 8 +-
arch/x86/include/asm/efi.h | 5 ++
arch/x86/include/uapi/asm/bootparam.h | 3 +
arch/x86/kernel/setup.c | 7 ++
drivers/firmware/efi/libstub/Makefile | 2 -
drivers/firmware/efi/libstub/arm-stub.c | 46 --------------
drivers/firmware/efi/libstub/secureboot.c | 93 +++++++++++++++++++++++++++++
include/linux/efi.h | 6 ++
13 files changed, 128 insertions(+), 55 deletions(-)
create mode 100644 drivers/firmware/efi/libstub/secureboot.c
From: Josh Boyer <[email protected]>
UEFI machines can be booted in Secure Boot mode. Add a EFI_SECURE_BOOT bit
that can be passed to efi_enabled() to find out whether secure boot is
enabled.
This will be used by the SysRq+x handler, registered by the x86 arch, to find
out whether secure boot mode is enabled so that it can be disabled.
Signed-off-by: Josh Boyer <[email protected]>
Signed-off-by: David Howells <[email protected]>
---
arch/x86/kernel/setup.c | 7 +++++++
include/linux/efi.h | 1 +
2 files changed, 8 insertions(+)
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 9c337b0e8ba7..522915d6de1f 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1160,6 +1160,13 @@ void __init setup_arch(char **cmdline_p)
io_delay_init();
+#ifdef CONFIG_EFI
+ if (boot_params.secure_boot) {
+ set_bit(EFI_SECURE_BOOT, &efi.flags);
+ pr_info("Secure boot enabled\n");
+ }
+#endif
+
/*
* Parse the ACPI tables for possible boot-time SMP configuration.
*/
diff --git a/include/linux/efi.h b/include/linux/efi.h
index ff01ad6f2823..d95bb9e69974 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1066,6 +1066,7 @@ extern int __init efi_setup_pcdp_console(char *);
#define EFI_ARCH_1 7 /* First arch-specific bit */
#define EFI_DBG 8 /* Print additional debug info at runtime */
#define EFI_NX_PE_DATA 9 /* Can runtime data regions be mapped non-executable? */
+#define EFI_SECURE_BOOT 10 /* Are we in Secure Boot mode? */
#ifdef CONFIG_EFI
/*
Provide the ability to perform mixed-mode runtime service calls for x86 in
the same way that commit 0a637ee61247bd4bed9b2a07568ef7a1cfc76187
("x86/efi: Allow invocation of arbitrary boot services") provides the
ability to invoke arbitrary boot services.
Suggested-by: Lukas Wunner <[email protected]>
Signed-off-by: David Howells <[email protected]>
---
arch/x86/boot/compressed/eboot.c | 1 +
arch/x86/boot/compressed/head_32.S | 6 +++---
arch/x86/boot/compressed/head_64.S | 8 ++++----
arch/x86/include/asm/efi.h | 5 +++++
4 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index ff01c8fc76f7..c8c32ebcdfdb 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -32,6 +32,7 @@ static void setup_boot_services##bits(struct efi_config *c) \
\
table = (typeof(table))sys_table; \
\
+ c->runtime_services = table->runtime; \
c->boot_services = table->boottime; \
c->text_output = table->con_out; \
}
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index fd0b6a272dd5..d85b9625e836 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -82,7 +82,7 @@ ENTRY(efi_pe_entry)
/* Relocate efi_config->call() */
leal efi32_config(%esi), %eax
- add %esi, 32(%eax)
+ add %esi, 40(%eax)
pushl %eax
call make_boot_params
@@ -108,7 +108,7 @@ ENTRY(efi32_stub_entry)
/* Relocate efi_config->call() */
leal efi32_config(%esi), %eax
- add %esi, 32(%eax)
+ add %esi, 40(%eax)
pushl %eax
2:
call efi_main
@@ -264,7 +264,7 @@ relocated:
#ifdef CONFIG_EFI_STUB
.data
efi32_config:
- .fill 4,8,0
+ .fill 5,8,0
.long efi_call_phys
.long 0
.byte 0
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index efdfba21a5b2..beab8322f72a 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -265,7 +265,7 @@ ENTRY(efi_pe_entry)
/*
* Relocate efi_config->call().
*/
- addq %rbp, efi64_config+32(%rip)
+ addq %rbp, efi64_config+40(%rip)
movq %rax, %rdi
call make_boot_params
@@ -285,7 +285,7 @@ handover_entry:
* Relocate efi_config->call().
*/
movq efi_config(%rip), %rax
- addq %rbp, 32(%rax)
+ addq %rbp, 40(%rax)
2:
movq efi_config(%rip), %rdi
call efi_main
@@ -457,14 +457,14 @@ efi_config:
#ifdef CONFIG_EFI_MIXED
.global efi32_config
efi32_config:
- .fill 4,8,0
+ .fill 5,8,0
.quad efi64_thunk
.byte 0
#endif
.global efi64_config
efi64_config:
- .fill 4,8,0
+ .fill 5,8,0
.quad efi_call
.byte 1
#endif /* CONFIG_EFI_STUB */
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index e99675b9c861..2f77bcefe6b4 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -191,6 +191,7 @@ static inline efi_status_t efi_thunk_set_virtual_address_map(
struct efi_config {
u64 image_handle;
u64 table;
+ u64 runtime_services;
u64 boot_services;
u64 text_output;
efi_status_t (*call)(unsigned long, ...);
@@ -226,6 +227,10 @@ static inline bool efi_is_64bit(void)
#define __efi_call_early(f, ...) \
__efi_early()->call((unsigned long)f, __VA_ARGS__);
+#define efi_call_runtime(f, ...) \
+ __efi_early()->call(efi_table_attr(efi_runtime_services, f, \
+ __efi_early()->runtime_services), __VA_ARGS__)
+
extern bool efi_reboot_required(void);
#else
Add the definitions for shim and image security database, both of which
are used widely in various Linux distros.
Signed-off-by: Josh Boyer <[email protected]>
Signed-off-by: David Howells <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
---
include/linux/efi.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/include/linux/efi.h b/include/linux/efi.h
index a07a476178cd..24db4e5ec817 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -610,6 +610,9 @@ void efi_native_runtime_setup(void);
#define EFI_CONSOLE_OUT_DEVICE_GUID EFI_GUID(0xd3b36f2c, 0xd551, 0x11d4, 0x9a, 0x46, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)
#define APPLE_PROPERTIES_PROTOCOL_GUID EFI_GUID(0x91bd12fe, 0xf6c3, 0x44fb, 0xa5, 0xb7, 0x51, 0x22, 0xab, 0x30, 0x3a, 0xe0)
+#define EFI_IMAGE_SECURITY_DATABASE_GUID EFI_GUID(0xd719b2cb, 0x3d3a, 0x4596, 0xa3, 0xbc, 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f)
+#define EFI_SHIM_LOCK_GUID EFI_GUID(0x605dab50, 0xe046, 0x4300, 0xab, 0xb6, 0x3d, 0xd8, 0x10, 0xdd, 0x8b, 0x23)
+
/*
* This GUID is used to pass to the kernel proper the struct screen_info
* structure that was populated by the stub based on the GOP protocol instance
From: Josh Boyer <[email protected]>
A user can manually tell the shim boot loader to disable validation of
images it loads. When a user does this, it creates a UEFI variable called
MokSBState that does not have the runtime attribute set. Given that the
user explicitly disabled validation, we can honor that and not enable
secure boot mode if that variable is set.
Signed-off-by: Josh Boyer <[email protected]>
Signed-off-by: David Howells <[email protected]>
---
drivers/firmware/efi/libstub/secureboot.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
index 466fe24f5866..ca643eba5a4b 100644
--- a/drivers/firmware/efi/libstub/secureboot.c
+++ b/drivers/firmware/efi/libstub/secureboot.c
@@ -23,6 +23,12 @@ static const efi_char16_t const efi_SetupMode_name[] = {
'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0
};
+/* SHIM variables */
+static const efi_guid_t shim_guid = EFI_SHIM_LOCK_GUID;
+static efi_char16_t const shim_MokSBState_name[] = {
+ 'M', 'o', 'k', 'S', 'B', 'S', 't', 'a', 't', 'e', 0
+};
+
#define get_efi_var(name, vendor, ...) \
efi_call_runtime(get_variable, \
(efi_char16_t *)(name), (efi_guid_t *)(vendor), \
@@ -33,7 +39,8 @@ static const efi_char16_t const efi_SetupMode_name[] = {
*/
int efi_get_secureboot(efi_system_table_t *sys_table_arg)
{
- u8 val;
+ u32 attr;
+ u8 val, moksbstate;
unsigned long size = sizeof(val);
efi_status_t status;
@@ -55,6 +62,21 @@ int efi_get_secureboot(efi_system_table_t *sys_table_arg)
if (val == 1)
return 0;
+ /* See if a user has put shim into insecure mode. If so, and if the
+ * variable doesn't have the runtime attribute set, we might as well
+ * honor that.
+ */
+ size = sizeof(moksbstate);
+ status = get_efi_var(shim_MokSBState_name, &shim_guid,
+ &attr, &size, &moksbstate);
+
+ /* If it fails, we don't care why. Default to secure */
+ if (status != EFI_SUCCESS)
+ return 1;
+
+ if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS) && moksbstate == 1)
+ return 0;
+
return 1;
out_efi_err:
Get the firmware's secure-boot status in the kernel boot wrapper and stash
it somewhere that the main kernel image can find.
The efi_get_secureboot() function is extracted from the arm stub and (a)
generalised so that it can be called from x86 and (b) made to use
efi_call_runtime() so that it can be run in mixed-mode.
Suggested-by: Lukas Wunner <[email protected]>
Signed-off-by: David Howells <[email protected]>
---
Documentation/x86/zero-page.txt | 2 +
arch/x86/boot/compressed/eboot.c | 2 +
arch/x86/include/uapi/asm/bootparam.h | 3 +
drivers/firmware/efi/libstub/Makefile | 2 -
drivers/firmware/efi/libstub/arm-stub.c | 46 -------------------
drivers/firmware/efi/libstub/secureboot.c | 71 +++++++++++++++++++++++++++++
include/linux/efi.h | 2 +
7 files changed, 80 insertions(+), 48 deletions(-)
create mode 100644 drivers/firmware/efi/libstub/secureboot.c
diff --git a/Documentation/x86/zero-page.txt b/Documentation/x86/zero-page.txt
index 95a4d34af3fd..b8527c6b7646 100644
--- a/Documentation/x86/zero-page.txt
+++ b/Documentation/x86/zero-page.txt
@@ -31,6 +31,8 @@ Offset Proto Name Meaning
1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below)
1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
(below)
+1EB/001 ALL kbd_status Numlock is enabled
+1EC/001 ALL secure_boot Secure boot is enabled in the firmware
1EF/001 ALL sentinel Used to detect broken bootloaders
290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
2D0/A00 ALL e820_map E820 memory map table
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index c8c32ebcdfdb..6023b0e6f2af 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -1158,6 +1158,8 @@ struct boot_params *efi_main(struct efi_config *c,
else
setup_boot_services32(efi_early);
+ boot_params->secure_boot = (efi_get_secureboot(sys_table) == 1);
+
setup_graphics(boot_params);
setup_efi_pci(boot_params);
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index b10bf319ed20..5138dacf8bb8 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -135,7 +135,8 @@ struct boot_params {
__u8 eddbuf_entries; /* 0x1e9 */
__u8 edd_mbr_sig_buf_entries; /* 0x1ea */
__u8 kbd_status; /* 0x1eb */
- __u8 _pad5[3]; /* 0x1ec */
+ __u8 secure_boot; /* 0x1ec */
+ __u8 _pad5[2]; /* 0x1ed */
/*
* The sentinel is set to a nonzero value (0xff) in header.S.
*
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 6621b13c370f..9af966863612 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -28,7 +28,7 @@ OBJECT_FILES_NON_STANDARD := y
# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
KCOV_INSTRUMENT := n
-lib-y := efi-stub-helper.o gop.o
+lib-y := efi-stub-helper.o gop.o secureboot.o
# include the stub's generic dependencies from lib/ when building for ARM/arm64
arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index b4f7d78f9e8b..552ee61ddbed 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -20,52 +20,6 @@
bool __nokaslr;
-static int efi_get_secureboot(efi_system_table_t *sys_table_arg)
-{
- static efi_char16_t const sb_var_name[] = {
- 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 };
- static efi_char16_t const sm_var_name[] = {
- 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 };
-
- efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
- efi_get_variable_t *f_getvar = sys_table_arg->runtime->get_variable;
- u8 val;
- unsigned long size = sizeof(val);
- efi_status_t status;
-
- status = f_getvar((efi_char16_t *)sb_var_name, (efi_guid_t *)&var_guid,
- NULL, &size, &val);
-
- if (status != EFI_SUCCESS)
- goto out_efi_err;
-
- if (val == 0)
- return 0;
-
- status = f_getvar((efi_char16_t *)sm_var_name, (efi_guid_t *)&var_guid,
- NULL, &size, &val);
-
- if (status != EFI_SUCCESS)
- goto out_efi_err;
-
- if (val == 1)
- return 0;
-
- return 1;
-
-out_efi_err:
- switch (status) {
- case EFI_NOT_FOUND:
- return 0;
- case EFI_DEVICE_ERROR:
- return -EIO;
- case EFI_SECURITY_VIOLATION:
- return -EACCES;
- default:
- return -EINVAL;
- }
-}
-
efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg,
void *__image, void **__fh)
{
diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
new file mode 100644
index 000000000000..466fe24f5866
--- /dev/null
+++ b/drivers/firmware/efi/libstub/secureboot.c
@@ -0,0 +1,71 @@
+/*
+ * Secure boot handling.
+ *
+ * Copyright (C) 2013,2014 Linaro Limited
+ * Roy Franz <[email protected]
+ * Copyright (C) 2013 Red Hat, Inc.
+ * Mark Salter <[email protected]>
+ *
+ * This file is part of the Linux kernel, and is made available under the
+ * terms of the GNU General Public License version 2.
+ *
+ */
+
+#include <linux/efi.h>
+#include <asm/efi.h>
+
+/* BIOS variables */
+static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
+static const efi_char16_t const efi_SecureBoot_name[] = {
+ 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0
+};
+static const efi_char16_t const efi_SetupMode_name[] = {
+ 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0
+};
+
+#define get_efi_var(name, vendor, ...) \
+ efi_call_runtime(get_variable, \
+ (efi_char16_t *)(name), (efi_guid_t *)(vendor), \
+ __VA_ARGS__);
+
+/*
+ * Determine whether we're in secure boot mode.
+ */
+int efi_get_secureboot(efi_system_table_t *sys_table_arg)
+{
+ u8 val;
+ unsigned long size = sizeof(val);
+ efi_status_t status;
+
+ status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
+ NULL, &size, &val);
+
+ if (status != EFI_SUCCESS)
+ goto out_efi_err;
+
+ if (val == 0)
+ return 0;
+
+ status = get_efi_var(efi_SetupMode_name, &efi_variable_guid,
+ NULL, &size, &val);
+
+ if (status != EFI_SUCCESS)
+ goto out_efi_err;
+
+ if (val == 1)
+ return 0;
+
+ return 1;
+
+out_efi_err:
+ switch (status) {
+ case EFI_NOT_FOUND:
+ return 0;
+ case EFI_DEVICE_ERROR:
+ return -EIO;
+ case EFI_SECURITY_VIOLATION:
+ return -EACCES;
+ default:
+ return -EINVAL;
+ }
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 24db4e5ec817..ff01ad6f2823 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1477,6 +1477,8 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg,
bool efi_runtime_disabled(void);
extern void efi_call_virt_check_flags(unsigned long flags, const char *call);
+int efi_get_secureboot(efi_system_table_t *sys_table_arg);
+
/*
* Arch code can implement the following three template macros, avoiding
* reptition for the void/non-void return cases of {__,}efi_call_virt():
Provide the ability to perform mixed-mode runtime service calls for arm in
the same way that commit 0a637ee61247bd4bed9b2a07568ef7a1cfc76187
("x86/efi: Allow invocation of arbitrary boot services") provides the
ability to invoke arbitrary boot services.
Suggested-by: Lukas Wunner <[email protected]>
Signed-off-by: David Howells <[email protected]>
---
arch/arm/include/asm/efi.h | 1 +
arch/arm64/include/asm/efi.h | 1 +
2 files changed, 2 insertions(+)
diff --git a/arch/arm/include/asm/efi.h b/arch/arm/include/asm/efi.h
index 0b06f5341b45..e4e6a9d6a825 100644
--- a/arch/arm/include/asm/efi.h
+++ b/arch/arm/include/asm/efi.h
@@ -55,6 +55,7 @@ void efi_virtmap_unload(void);
#define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)
#define __efi_call_early(f, ...) f(__VA_ARGS__)
+#define efi_call_runtime(f, ...) sys_table_arg->runtime->f(__VA_ARGS__)
#define efi_is_64bit() (false)
#define efi_call_proto(protocol, f, instance, ...) \
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 771b3f0bc757..d74ae223d89f 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -49,6 +49,7 @@ int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
#define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)
#define __efi_call_early(f, ...) f(__VA_ARGS__)
+#define efi_call_runtime(f, ...) sys_table_arg->runtime->f(__VA_ARGS__)
#define efi_is_64bit() (true)
#define efi_call_proto(protocol, f, instance, ...) \
On Wed, Nov 23, 2016 at 12:23:12AM +0000, David Howells wrote:
> From: Josh Boyer <[email protected]>
>
> UEFI machines can be booted in Secure Boot mode. Add a EFI_SECURE_BOOT bit
> that can be passed to efi_enabled() to find out whether secure boot is
> enabled.
>
> This will be used by the SysRq+x handler, registered by the x86 arch, to find
> out whether secure boot mode is enabled so that it can be disabled.
>
> Signed-off-by: Josh Boyer <[email protected]>
> Signed-off-by: David Howells <[email protected]>
> ---
>
> arch/x86/kernel/setup.c | 7 +++++++
> include/linux/efi.h | 1 +
> 2 files changed, 8 insertions(+)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 9c337b0e8ba7..522915d6de1f 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1160,6 +1160,13 @@ void __init setup_arch(char **cmdline_p)
>
> io_delay_init();
>
> +#ifdef CONFIG_EFI
> + if (boot_params.secure_boot) {
> + set_bit(EFI_SECURE_BOOT, &efi.flags);
> + pr_info("Secure boot enabled\n");
> + }
> +#endif
> +
Section 20 of Documentation/CodingStyle recommends IS_ENABLED()
instead of #ifdef. Also, CONFIG_EFI_STUB might be more apt than
CONFIG_EFI.
Thanks,
Lukas
> /*
> * Parse the ACPI tables for possible boot-time SMP configuration.
> */
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index ff01ad6f2823..d95bb9e69974 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -1066,6 +1066,7 @@ extern int __init efi_setup_pcdp_console(char *);
> #define EFI_ARCH_1 7 /* First arch-specific bit */
> #define EFI_DBG 8 /* Print additional debug info at runtime */
> #define EFI_NX_PE_DATA 9 /* Can runtime data regions be mapped non-executable? */
> +#define EFI_SECURE_BOOT 10 /* Are we in Secure Boot mode? */
>
> #ifdef CONFIG_EFI
> /*
>
On Wed, Nov 23, 2016 at 12:22:57AM +0000, David Howells wrote:
> Get the firmware's secure-boot status in the kernel boot wrapper and stash
> it somewhere that the main kernel image can find.
>
> The efi_get_secureboot() function is extracted from the arm stub and (a)
> generalised so that it can be called from x86 and (b) made to use
> efi_call_runtime() so that it can be run in mixed-mode.
>
> Suggested-by: Lukas Wunner <[email protected]>
> Signed-off-by: David Howells <[email protected]>
> ---
>
> Documentation/x86/zero-page.txt | 2 +
> arch/x86/boot/compressed/eboot.c | 2 +
> arch/x86/include/uapi/asm/bootparam.h | 3 +
> drivers/firmware/efi/libstub/Makefile | 2 -
> drivers/firmware/efi/libstub/arm-stub.c | 46 -------------------
> drivers/firmware/efi/libstub/secureboot.c | 71 +++++++++++++++++++++++++++++
> include/linux/efi.h | 2 +
> 7 files changed, 80 insertions(+), 48 deletions(-)
> create mode 100644 drivers/firmware/efi/libstub/secureboot.c
>
> diff --git a/Documentation/x86/zero-page.txt b/Documentation/x86/zero-page.txt
> index 95a4d34af3fd..b8527c6b7646 100644
> --- a/Documentation/x86/zero-page.txt
> +++ b/Documentation/x86/zero-page.txt
> @@ -31,6 +31,8 @@ Offset Proto Name Meaning
> 1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below)
> 1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
> (below)
> +1EB/001 ALL kbd_status Numlock is enabled
> +1EC/001 ALL secure_boot Secure boot is enabled in the firmware
> 1EF/001 ALL sentinel Used to detect broken bootloaders
> 290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
> 2D0/A00 ALL e820_map E820 memory map table
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index c8c32ebcdfdb..6023b0e6f2af 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -1158,6 +1158,8 @@ struct boot_params *efi_main(struct efi_config *c,
> else
> setup_boot_services32(efi_early);
>
> + boot_params->secure_boot = (efi_get_secureboot(sys_table) == 1);
> +
It just occurred to me that the boot_params struct is populated in
make_boot_params(), perhaps it makes sense to move this line there.
Otherwise LGTM.
Thanks,
Lukas
> setup_graphics(boot_params);
>
> setup_efi_pci(boot_params);
> diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
> index b10bf319ed20..5138dacf8bb8 100644
> --- a/arch/x86/include/uapi/asm/bootparam.h
> +++ b/arch/x86/include/uapi/asm/bootparam.h
> @@ -135,7 +135,8 @@ struct boot_params {
> __u8 eddbuf_entries; /* 0x1e9 */
> __u8 edd_mbr_sig_buf_entries; /* 0x1ea */
> __u8 kbd_status; /* 0x1eb */
> - __u8 _pad5[3]; /* 0x1ec */
> + __u8 secure_boot; /* 0x1ec */
> + __u8 _pad5[2]; /* 0x1ed */
> /*
> * The sentinel is set to a nonzero value (0xff) in header.S.
> *
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 6621b13c370f..9af966863612 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -28,7 +28,7 @@ OBJECT_FILES_NON_STANDARD := y
> # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
> KCOV_INSTRUMENT := n
>
> -lib-y := efi-stub-helper.o gop.o
> +lib-y := efi-stub-helper.o gop.o secureboot.o
>
> # include the stub's generic dependencies from lib/ when building for ARM/arm64
> arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c
> diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
> index b4f7d78f9e8b..552ee61ddbed 100644
> --- a/drivers/firmware/efi/libstub/arm-stub.c
> +++ b/drivers/firmware/efi/libstub/arm-stub.c
> @@ -20,52 +20,6 @@
>
> bool __nokaslr;
>
> -static int efi_get_secureboot(efi_system_table_t *sys_table_arg)
> -{
> - static efi_char16_t const sb_var_name[] = {
> - 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0 };
> - static efi_char16_t const sm_var_name[] = {
> - 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0 };
> -
> - efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID;
> - efi_get_variable_t *f_getvar = sys_table_arg->runtime->get_variable;
> - u8 val;
> - unsigned long size = sizeof(val);
> - efi_status_t status;
> -
> - status = f_getvar((efi_char16_t *)sb_var_name, (efi_guid_t *)&var_guid,
> - NULL, &size, &val);
> -
> - if (status != EFI_SUCCESS)
> - goto out_efi_err;
> -
> - if (val == 0)
> - return 0;
> -
> - status = f_getvar((efi_char16_t *)sm_var_name, (efi_guid_t *)&var_guid,
> - NULL, &size, &val);
> -
> - if (status != EFI_SUCCESS)
> - goto out_efi_err;
> -
> - if (val == 1)
> - return 0;
> -
> - return 1;
> -
> -out_efi_err:
> - switch (status) {
> - case EFI_NOT_FOUND:
> - return 0;
> - case EFI_DEVICE_ERROR:
> - return -EIO;
> - case EFI_SECURITY_VIOLATION:
> - return -EACCES;
> - default:
> - return -EINVAL;
> - }
> -}
> -
> efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg,
> void *__image, void **__fh)
> {
> diff --git a/drivers/firmware/efi/libstub/secureboot.c b/drivers/firmware/efi/libstub/secureboot.c
> new file mode 100644
> index 000000000000..466fe24f5866
> --- /dev/null
> +++ b/drivers/firmware/efi/libstub/secureboot.c
> @@ -0,0 +1,71 @@
> +/*
> + * Secure boot handling.
> + *
> + * Copyright (C) 2013,2014 Linaro Limited
> + * Roy Franz <[email protected]
> + * Copyright (C) 2013 Red Hat, Inc.
> + * Mark Salter <[email protected]>
> + *
> + * This file is part of the Linux kernel, and is made available under the
> + * terms of the GNU General Public License version 2.
> + *
> + */
> +
> +#include <linux/efi.h>
> +#include <asm/efi.h>
> +
> +/* BIOS variables */
> +static const efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
> +static const efi_char16_t const efi_SecureBoot_name[] = {
> + 'S', 'e', 'c', 'u', 'r', 'e', 'B', 'o', 'o', 't', 0
> +};
> +static const efi_char16_t const efi_SetupMode_name[] = {
> + 'S', 'e', 't', 'u', 'p', 'M', 'o', 'd', 'e', 0
> +};
> +
> +#define get_efi_var(name, vendor, ...) \
> + efi_call_runtime(get_variable, \
> + (efi_char16_t *)(name), (efi_guid_t *)(vendor), \
> + __VA_ARGS__);
> +
> +/*
> + * Determine whether we're in secure boot mode.
> + */
> +int efi_get_secureboot(efi_system_table_t *sys_table_arg)
> +{
> + u8 val;
> + unsigned long size = sizeof(val);
> + efi_status_t status;
> +
> + status = get_efi_var(efi_SecureBoot_name, &efi_variable_guid,
> + NULL, &size, &val);
> +
> + if (status != EFI_SUCCESS)
> + goto out_efi_err;
> +
> + if (val == 0)
> + return 0;
> +
> + status = get_efi_var(efi_SetupMode_name, &efi_variable_guid,
> + NULL, &size, &val);
> +
> + if (status != EFI_SUCCESS)
> + goto out_efi_err;
> +
> + if (val == 1)
> + return 0;
> +
> + return 1;
> +
> +out_efi_err:
> + switch (status) {
> + case EFI_NOT_FOUND:
> + return 0;
> + case EFI_DEVICE_ERROR:
> + return -EIO;
> + case EFI_SECURITY_VIOLATION:
> + return -EACCES;
> + default:
> + return -EINVAL;
> + }
> +}
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 24db4e5ec817..ff01ad6f2823 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -1477,6 +1477,8 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg,
> bool efi_runtime_disabled(void);
> extern void efi_call_virt_check_flags(unsigned long flags, const char *call);
>
> +int efi_get_secureboot(efi_system_table_t *sys_table_arg);
> +
> /*
> * Arch code can implement the following three template macros, avoiding
> * reptition for the void/non-void return cases of {__,}efi_call_virt():
>
David Howells <[email protected]> wrote:
> +#define efi_call_runtime(f, ...) sys_table_arg->runtime->f(__VA_ARGS__)
Turns out it's not that simple - of course. runtime->get_variable is just a
void pointer. The old arm stub was casting it by virtue of assignment to a
function pointer variable.
The x86_64 appears to be doing bypassing all the compile-time type checking by
passing the arguments through an ellipsis and then fixing up the argument list
in the ->call() function.
What I've changed the ARM and ARM64 things to is:
#define efi_call_runtime(f, ...) ((efi_##f##_t *)sys_table_arg->runtime->f)(__VA_ARGS__)
David
Lukas Wunner <[email protected]> wrote:
> It just occurred to me that the boot_params struct is populated in
> make_boot_params(), perhaps it makes sense to move this line there.
> Otherwise LGTM.
Ummm... Looking at arch/x86/boot/compressed/head_64.S, make_boot_params() is
only called if the stub is entered through efi_pe_entry, not if entered
through efi64_stub_entry, whereas efi_main() is called in both cases. I think
entry through efi32_stub_entry may also skip make_boot_params().
The comment on make_boot_params() suggests that this function is only used if
whoever booted the kernel didn't supply it.
David
Lukas Wunner <[email protected]> wrote:
> > +#ifdef CONFIG_EFI
> > + if (boot_params.secure_boot) {
> > + set_bit(EFI_SECURE_BOOT, &efi.flags);
> > + pr_info("Secure boot enabled\n");
> > + }
> > +#endif
> > +
>
> Section 20 of Documentation/CodingStyle recommends IS_ENABLED()
> instead of #ifdef.
The problem is this:
arch/x86/include/asm/bitops.h:75: undefined reference to `efi'
To quote section 20: "... Thus, you still have to use an #ifdef if the code
inside the block references symbols that will not exist if the condition is
not met."
> Also, CONFIG_EFI_STUB might be more apt than CONFIG_EFI.
Other stuff in the same function is contingent on CONFIG_EFI. EFI_STUB is to
do with how the thing can be booted, I think - not whether EFI support is
enabled.
David
David Howells <[email protected]> wrote:
> > > +#ifdef CONFIG_EFI
> > > + if (boot_params.secure_boot) {
> > > + set_bit(EFI_SECURE_BOOT, &efi.flags);
> > > + pr_info("Secure boot enabled\n");
> > > + }
> > > +#endif
> > > +
> >
> > Section 20 of Documentation/CodingStyle recommends IS_ENABLED()
> > instead of #ifdef.
>
> The problem is this:
>
> arch/x86/include/asm/bitops.h:75: undefined reference to `efi'
>
> To quote section 20: "... Thus, you still have to use an #ifdef if the code
> inside the block references symbols that will not exist if the condition is
> not met."
Okay, I take that back - it does actually work. However, should I follow the
scheme of the rest of the file?
David
On Wed, Nov 23, 2016 at 09:53:00AM +0000, David Howells wrote:
> Lukas Wunner <[email protected]> wrote:
> > It just occurred to me that the boot_params struct is populated in
> > make_boot_params(), perhaps it makes sense to move this line there.
> > Otherwise LGTM.
>
> Ummm... Looking at arch/x86/boot/compressed/head_64.S, make_boot_params() is
> only called if the stub is entered through efi_pe_entry, not if entered
> through efi64_stub_entry, whereas efi_main() is called in both cases. I think
> entry through efi32_stub_entry may also skip make_boot_params().
>
> The comment on make_boot_params() suggests that this function is only used if
> whoever booted the kernel didn't supply it.
Good point. :-) I didn't dig this deep, it was just something that
crossed my mind when skimming over the patch.
You're also right about the (efi_##f##_t *) addition in patch 2.
Thanks,
Lukas
Hi,
Any reason to not Cc LAKML?
On Wed, Nov 23, 2016 at 12:22:43AM +0000, David Howells wrote:
> Provide the ability to perform mixed-mode runtime service calls for arm in
> the same way that commit 0a637ee61247bd4bed9b2a07568ef7a1cfc76187
> ("x86/efi: Allow invocation of arbitrary boot services") provides the
> ability to invoke arbitrary boot services.
I'm not sure I understand. On arm/arm64, "mixed-mode" simply isn't possible.
I see we already call runtime services directly in efi_get_secureboot()
in drivers/firmware/efi/libstub/arm-stub.c.
If this is just to provide a consistent API for the stub, please note
that.
> Suggested-by: Lukas Wunner <[email protected]>
> Signed-off-by: David Howells <[email protected]>
> ---
>
> arch/arm/include/asm/efi.h | 1 +
> arch/arm64/include/asm/efi.h | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/arch/arm/include/asm/efi.h b/arch/arm/include/asm/efi.h
> index 0b06f5341b45..e4e6a9d6a825 100644
> --- a/arch/arm/include/asm/efi.h
> +++ b/arch/arm/include/asm/efi.h
> @@ -55,6 +55,7 @@ void efi_virtmap_unload(void);
>
> #define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)
> #define __efi_call_early(f, ...) f(__VA_ARGS__)
> +#define efi_call_runtime(f, ...) sys_table_arg->runtime->f(__VA_ARGS__)
> #define efi_is_64bit() (false)
>
> #define efi_call_proto(protocol, f, instance, ...) \
> diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
> index 771b3f0bc757..d74ae223d89f 100644
> --- a/arch/arm64/include/asm/efi.h
> +++ b/arch/arm64/include/asm/efi.h
> @@ -49,6 +49,7 @@ int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
>
> #define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)
> #define __efi_call_early(f, ...) f(__VA_ARGS__)
> +#define efi_call_runtime(f, ...) sys_table_arg->runtime->f(__VA_ARGS__)
Given this can only work in the stub, the name is somewhat unfortunate,
as it sounds like it's expected to be used at runtime (i.e. in the
kernel). But I guess that's not a big problem.
Other than the casting issue you noted, I think this should work,
though.
Thanks,
Mark.
On 23 November 2016 at 09:34, David Howells <[email protected]> wrote:
> David Howells <[email protected]> wrote:
>
>> +#define efi_call_runtime(f, ...) sys_table_arg->runtime->f(__VA_ARGS__)
>
> Turns out it's not that simple - of course. runtime->get_variable is just a
> void pointer. The old arm stub was casting it by virtue of assignment to a
> function pointer variable.
>
> The x86_64 appears to be doing bypassing all the compile-time type checking by
> passing the arguments through an ellipsis and then fixing up the argument list
> in the ->call() function.
>
> What I've changed the ARM and ARM64 things to is:
>
> #define efi_call_runtime(f, ...) ((efi_##f##_t *)sys_table_arg->runtime->f)(__VA_ARGS__)
>
Could we please instead fix the definition of efi_runtime_services_t,
given that we have typedefs already for all its members?
On Wed, Nov 23, 2016 at 12:22:57AM +0000, David Howells wrote:
> @@ -1158,6 +1158,8 @@ struct boot_params *efi_main(struct efi_config *c,
> else
> setup_boot_services32(efi_early);
>
> + boot_params->secure_boot = (efi_get_secureboot(sys_table) == 1);
In the arm stub's efi_entry(), we fail-safe, and assume secure boot for any
non-zero status (including errors). e.g.
secure_boot = efi_get_secureboot(sys_table);
if (secure_boot > 0)
pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
if (secure_boot < 0) {
pr_efi_err(sys_table,
"could not determine UEFI Secure Boot status.\n");
}
/*
* Unauthenticated device tree data is a security hazard, so
* ignore 'dtb=' unless UEFI Secure Boot is disabled.
*/
if (secure_boot != 0 && strstr(cmdline_ptr, "dtb=")) {
pr_efi(sys_table, "Ignoring DTB from command line.\n");
... should we not do likewise here, e.g.
int secure_boot = efi_get_secureboot(sys_table);
if (secure_boot > 0)
pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
if (secure_boot < 0)
pr_efi_err(sys_table,
"could not determine UEFI Secure Boot status.\n");
/*
* Fail-safe in the case of an error determining the secure boot
* status.
*/
boot_params->secure_boot = (secure_boot != 0);
... ?
Thanks,
Mark.
Mark Rutland <[email protected]> wrote:
> int secure_boot = efi_get_secureboot(sys_table);
>
> if (secure_boot > 0)
> pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
> if (secure_boot < 0)
> pr_efi_err(sys_table,
> "could not determine UEFI Secure Boot status.\n");
In which case, should this be moved into efi_get_secureboot() and it return a
bool?
David
Mark Rutland <[email protected]> wrote:
> Any reason to not Cc LAKML?
Probably not.
> On Wed, Nov 23, 2016 at 12:22:43AM +0000, David Howells wrote:
> > Provide the ability to perform mixed-mode runtime service calls for arm in
> > the same way that commit 0a637ee61247bd4bed9b2a07568ef7a1cfc76187
> > ("x86/efi: Allow invocation of arbitrary boot services") provides the
> > ability to invoke arbitrary boot services.
>
> I'm not sure I understand. On arm/arm64, "mixed-mode" simply isn't possible.
>
> I see we already call runtime services directly in efi_get_secureboot()
> in drivers/firmware/efi/libstub/arm-stub.c.
>
> If this is just to provide a consistent API for the stub, please note
> that.
How about:
arm/efi: Allow invocation of arbitrary runtime services
efi_call_runtime() is provided for x86 to be able abstract mixed mode
support. Provide this for ARM also so that common code work in mixed mode
also.
David
Ard Biesheuvel <[email protected]> wrote:
> > What I've changed the ARM and ARM64 things to is:
> >
> > #define efi_call_runtime(f, ...) ((efi_##f##_t *)sys_table_arg->runtime->f)(__VA_ARGS__)
> >
>
> Could we please instead fix the definition of efi_runtime_services_t,
> given that we have typedefs already for all its members?
Okay, I've pulled in your patch and removed the cast.
I would like to provide wrapper static inlines for things like
efi_get_variable() to get the parameter checking, but the sys_table_arg
behind-the-scenes parameter is tricky to deal with in that case.
David
On Wed, Nov 23, 2016 at 12:23:04AM +0000, David Howells wrote:
> + /* See if a user has put shim into insecure mode. If so, and if the
> + * variable doesn't have the runtime attribute set, we might as well
> + * honor that.
> + */
> + size = sizeof(moksbstate);
> + status = get_efi_var(shim_MokSBState_name, &shim_guid,
> + &attr, &size, &moksbstate);
> +
> + /* If it fails, we don't care why. Default to secure */
> + if (status != EFI_SUCCESS)
> + return 1;
I was going to suggest branching to out_efi_err, but I see that wouldn't
work when EFI_NOT_FOUND was returned. It might be worth noting
explicitly that we can't use that, so as to avoid 'obvious' cleanup in
future.
Thanks,
Mark.
On Wed, Nov 23, 2016 at 11:46:38AM +0000, David Howells wrote:
> Mark Rutland <[email protected]> wrote:
> > On Wed, Nov 23, 2016 at 12:22:43AM +0000, David Howells wrote:
> > > Provide the ability to perform mixed-mode runtime service calls for arm in
> > > the same way that commit 0a637ee61247bd4bed9b2a07568ef7a1cfc76187
> > > ("x86/efi: Allow invocation of arbitrary boot services") provides the
> > > ability to invoke arbitrary boot services.
> >
> > I'm not sure I understand. On arm/arm64, "mixed-mode" simply isn't possible.
> >
> > I see we already call runtime services directly in efi_get_secureboot()
> > in drivers/firmware/efi/libstub/arm-stub.c.
> >
> > If this is just to provide a consistent API for the stub, please note
> > that.
>
> How about:
>
> arm/efi: Allow invocation of arbitrary runtime services
>
> efi_call_runtime() is provided for x86 to be able abstract mixed mode
> support. Provide this for ARM also so that common code work in mixed mode
> also.
That sounds good to me.
Thanks,
Mark.
On Wed, Nov 23, 2016 at 11:25:57AM +0000, David Howells wrote:
> Mark Rutland <[email protected]> wrote:
>
> > int secure_boot = efi_get_secureboot(sys_table);
> >
> > if (secure_boot > 0)
> > pr_efi(sys_table, "UEFI Secure Boot is enabled.\n");
> > if (secure_boot < 0)
> > pr_efi_err(sys_table,
> > "could not determine UEFI Secure Boot status.\n");
>
> In which case, should this be moved into efi_get_secureboot() and it return a
> bool?
That would make sense to me, provided we're only likely to call that
once (and only log once).
I guess it would also make sense to change the latter case to soemthing
like:
Could not determine UEFI Secure Boot status. Assuming enabled.
... so as to make it clear what the effect is.
Thanks,
Mark.
Mark Rutland <[email protected]> wrote:
> > > if (secure_boot < 0)
> > > pr_efi_err(sys_table,
> > > "could not determine UEFI Secure Boot status.\n");
> >
> > In which case, should this be moved into efi_get_secureboot() and it return a
> > bool?
>
> That would make sense to me, provided we're only likely to call that
> once (and only log once).
>
> I guess it would also make sense to change the latter case to soemthing
> like:
>
> Could not determine UEFI Secure Boot status. Assuming enabled.
>
> ... so as to make it clear what the effect is.
Actually, the two arches have a different interpretation on how to deal with
an error. Matthew Garrett's original x86 patch assumes that if we get an
error when trying to read SecureBoot and SetupMode that we're *not* in secure
mode, but ARM assumes the opposite.
David
Mark Rutland <[email protected]> wrote:
> On Wed, Nov 23, 2016 at 02:13:28PM +0000, David Howells wrote:
> > Mark Rutland <[email protected]> wrote:
> >
> > > > > if (secure_boot < 0)
> > > > > pr_efi_err(sys_table,
> > > > > "could not determine UEFI Secure Boot status.\n");
> > > >
> > > > In which case, should this be moved into efi_get_secureboot() and it
> > > > return a bool?
> > >
> > > That would make sense to me, provided we're only likely to call that
> > > once (and only log once).
> > >
> > > I guess it would also make sense to change the latter case to soemthing
> > > like:
> > >
> > > Could not determine UEFI Secure Boot status. Assuming enabled.
> > >
> > > ... so as to make it clear what the effect is.
> >
> > Actually, the two arches have a different interpretation on how to deal
> > with an error. Matthew Garrett's original x86 patch assumes that if we
> > get an error when trying to read SecureBoot and SetupMode that we're *not*
> > in secure mode, but ARM assumes the opposite.
>
> Ok.
>
> IIUC, that x86 patch was never upstream, so is there any need to follow
> that example?
Whilst that may be true, that doesn't mean a lot of people aren't using it.
> Was there a rationale for that, or can we simply follow the upstream ARM
> example?
>
> Perhaps it's best to ask Matthew?
Sure - adding him to the To: line.
David
On Wed, Nov 23, 2016 at 02:13:28PM +0000, David Howells wrote:
> Mark Rutland <[email protected]> wrote:
>
> > > > if (secure_boot < 0)
> > > > pr_efi_err(sys_table,
> > > > "could not determine UEFI Secure Boot status.\n");
> > >
> > > In which case, should this be moved into efi_get_secureboot() and it return a
> > > bool?
> >
> > That would make sense to me, provided we're only likely to call that
> > once (and only log once).
> >
> > I guess it would also make sense to change the latter case to soemthing
> > like:
> >
> > Could not determine UEFI Secure Boot status. Assuming enabled.
> >
> > ... so as to make it clear what the effect is.
>
> Actually, the two arches have a different interpretation on how to deal with
> an error. Matthew Garrett's original x86 patch assumes that if we get an
> error when trying to read SecureBoot and SetupMode that we're *not* in secure
> mode, but ARM assumes the opposite.
Ok.
IIUC, that x86 patch was never upstream, so is there any need to follow
that example? Was there a rationale for that, or can we simply follow
the upstream ARM example?
Perhaps it's best to ask Matthew?
Thanks,
Mark.
On Wed, Nov 23, 2016 at 6:55 AM, David Howells <[email protected]> wrote:
> Mark Rutland <[email protected]> wrote:
>> > Actually, the two arches have a different interpretation on how to deal
>> > with an error. Matthew Garrett's original x86 patch assumes that if we
>> > get an error when trying to read SecureBoot and SetupMode that we're *not*
>> > in secure mode, but ARM assumes the opposite.
>>
>> Ok.
>>
>> IIUC, that x86 patch was never upstream, so is there any need to follow
>> that example?
>
> Whilst that may be true, that doesn't mean a lot of people aren't using it.
A conforming implementation that supports secure boot should always
return those variables without error. If they're not present (which is
valid for x86 systems - many predate the feature) then assuming Secure
Boot is disabled is correct. The question of what to do in the event
of other errors is more open, but it wouldn't surprise me if there are
implementations that return non-spec errors for missing variables
under certain circumstances.
Mark Rutland <[email protected]> wrote:
> > + boot_params->secure_boot = (efi_get_secureboot(sys_table) == 1);
>
> In the arm stub's efi_entry(), we fail-safe, and assume secure boot for any
> non-zero status (including errors). e.g.
Okay, given what Matthew said:
A conforming implementation that supports secure boot should always
return those variables without error. If they're not present (which is
valid for x86 systems - many predate the feature) then assuming Secure
Boot is disabled is correct. The question of what to do in the event
of other errors is more open, but it wouldn't surprise me if there are
implementations that return non-spec errors for missing variables
under certain circumstances.
I think I have to assume the default to be that secure boot is *not* enabled
in the case of one of the variables we need to check is not being present.
As for getting other errors, I think we have to assume a buggy BIOS. In this
case, I would also go with assuming we're not in secure boot.
Another possibility is to punt the decision and make it compile-time
configurable.
David