From cf1d2ffcc6f17b422239f6ab34b078945d07f9aa Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Wed, 1 Feb 2023 09:48:12 +0100 Subject: [PATCH] efi: Discover BTI support in runtime services regions 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 Reviewed-by: Kees Cook --- 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 b95241b..78282ce 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 882104f..e2b9d26 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 31d13a6..5d47d42 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 fab05de..78ffd5a 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 47d3ab0..29e9a0d 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 1aa5403..aa6209a 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 b36596b..2e6fe43 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 0a9aba5..3cbf00f 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 9d455d5..df88786 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, -- 2.7.4