Add the generic plumbing to detect whether or not the runtime code
regions were constructed with BTI/IBT landing pads by the firmware,
permitting the OS to enable enforcement when mapping these regions into
the OS's address space.
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
arch/arm/include/asm/efi.h | 2 +-
arch/arm/kernel/efi.c | 5 +++--
arch/arm64/include/asm/efi.h | 3 ++-
arch/arm64/kernel/efi.c | 3 ++-
arch/riscv/include/asm/efi.h | 2 +-
arch/riscv/kernel/efi.c | 3 ++-
arch/x86/platform/efi/efi_64.c | 3 ++-
drivers/firmware/efi/memattr.c | 7 ++++++-
include/linux/efi.h | 8 ++++++--
9 files changed, 25 insertions(+), 11 deletions(-)
diff --git a/arch/arm/include/asm/efi.h b/arch/arm/include/asm/efi.h
index b95241b1ca656f3c..78282ced50387dd3 100644
--- a/arch/arm/include/asm/efi.h
+++ b/arch/arm/include/asm/efi.h
@@ -20,7 +20,7 @@ void efi_init(void);
void arm_efi_init(void);
int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
-int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
+int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md, bool);
#define arch_efi_call_virt_setup() efi_virtmap_load()
#define arch_efi_call_virt_teardown() efi_virtmap_unload()
diff --git a/arch/arm/kernel/efi.c b/arch/arm/kernel/efi.c
index 882104f43b3b0928..e2b9d2618c6727c6 100644
--- a/arch/arm/kernel/efi.c
+++ b/arch/arm/kernel/efi.c
@@ -23,7 +23,8 @@ static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
}
int __init efi_set_mapping_permissions(struct mm_struct *mm,
- efi_memory_desc_t *md)
+ efi_memory_desc_t *md,
+ bool ignored)
{
unsigned long base, size;
@@ -71,7 +72,7 @@ int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
* If stricter permissions were specified, apply them now.
*/
if (md->attribute & (EFI_MEMORY_RO | EFI_MEMORY_XP))
- return efi_set_mapping_permissions(mm, md);
+ return efi_set_mapping_permissions(mm, md, false);
return 0;
}
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 31d13a6001df49c4..5d47d429672b1bfb 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -27,7 +27,8 @@ bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
#endif
int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
-int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
+int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md,
+ bool has_bti);
#define arch_efi_call_virt_setup() \
({ \
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index fab05de2e12dd5d8..78ffd5aaddcbbaee 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -110,7 +110,8 @@ static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
}
int __init efi_set_mapping_permissions(struct mm_struct *mm,
- efi_memory_desc_t *md)
+ efi_memory_desc_t *md,
+ bool has_bti)
{
BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
md->type != EFI_RUNTIME_SERVICES_DATA);
diff --git a/arch/riscv/include/asm/efi.h b/arch/riscv/include/asm/efi.h
index 47d3ab0fcc36a186..29e9a0d84b16682f 100644
--- a/arch/riscv/include/asm/efi.h
+++ b/arch/riscv/include/asm/efi.h
@@ -19,7 +19,7 @@ extern void efi_init(void);
#endif
int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
-int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
+int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md, bool);
#define arch_efi_call_virt_setup() ({ \
sync_kernel_mappings(efi_mm.pgd); \
diff --git a/arch/riscv/kernel/efi.c b/arch/riscv/kernel/efi.c
index 1aa540350abd31b0..aa6209a74c83ffc2 100644
--- a/arch/riscv/kernel/efi.c
+++ b/arch/riscv/kernel/efi.c
@@ -78,7 +78,8 @@ static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
}
int __init efi_set_mapping_permissions(struct mm_struct *mm,
- efi_memory_desc_t *md)
+ efi_memory_desc_t *md,
+ bool ignored)
{
BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
md->type != EFI_RUNTIME_SERVICES_DATA);
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index b36596bf0fc38f4f..2e6fe430cb07bbbc 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -389,7 +389,8 @@ static int __init efi_update_mappings(efi_memory_desc_t *md, unsigned long pf)
return err1 || err2;
}
-static int __init efi_update_mem_attr(struct mm_struct *mm, efi_memory_desc_t *md)
+static int __init efi_update_mem_attr(struct mm_struct *mm, efi_memory_desc_t *md,
+ bool has_ibt)
{
unsigned long pf = 0;
diff --git a/drivers/firmware/efi/memattr.c b/drivers/firmware/efi/memattr.c
index 0a9aba5f9ceff0bf..3cbf00f04c5b60ca 100644
--- a/drivers/firmware/efi/memattr.c
+++ b/drivers/firmware/efi/memattr.c
@@ -129,6 +129,7 @@ int __init efi_memattr_apply_permissions(struct mm_struct *mm,
efi_memattr_perm_setter fn)
{
efi_memory_attributes_table_t *tbl;
+ bool has_bti = false;
int i, ret;
if (tbl_size <= sizeof(*tbl))
@@ -150,6 +151,10 @@ int __init efi_memattr_apply_permissions(struct mm_struct *mm,
return -ENOMEM;
}
+ if (tbl->version > 1 &&
+ (tbl->flags & EFI_MEMORY_ATTRIBUTES_FLAGS_RT_FORWARD_CONTROL_FLOW_GUARD))
+ has_bti = true;
+
if (efi_enabled(EFI_DBG))
pr_info("Processing EFI Memory Attributes table:\n");
@@ -169,7 +174,7 @@ int __init efi_memattr_apply_permissions(struct mm_struct *mm,
efi_md_typeattr_format(buf, sizeof(buf), &md));
if (valid) {
- ret = fn(mm, &md);
+ ret = fn(mm, &md, has_bti);
if (ret)
pr_err("Error updating mappings, skipping subsequent md's\n");
}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 9d455d502ac92b65..df88786b59471714 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -584,11 +584,15 @@ typedef struct {
#define EFI_INVALID_TABLE_ADDR (~0UL)
+// BIT0 implies that Runtime code includes the forward control flow guard
+// instruction, such as X86 CET-IBT or ARM BTI.
+#define EFI_MEMORY_ATTRIBUTES_FLAGS_RT_FORWARD_CONTROL_FLOW_GUARD 0x1
+
typedef struct {
u32 version;
u32 num_entries;
u32 desc_size;
- u32 reserved;
+ u32 flags;
efi_memory_desc_t entry[0];
} efi_memory_attributes_table_t;
@@ -751,7 +755,7 @@ extern unsigned long efi_mem_attr_table;
* argument in the page tables referred to by the
* first argument.
*/
-typedef int (*efi_memattr_perm_setter)(struct mm_struct *, efi_memory_desc_t *);
+typedef int (*efi_memattr_perm_setter)(struct mm_struct *, efi_memory_desc_t *, bool);
extern int efi_memattr_init(void);
extern int efi_memattr_apply_permissions(struct mm_struct *mm,
--
2.39.1
