diff options
Diffstat (limited to 'arch/arm64/kernel/efi.c')
| -rw-r--r-- | arch/arm64/kernel/efi.c | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c new file mode 100644 index 000000000..a30dbe4b9 --- /dev/null +++ b/arch/arm64/kernel/efi.c @@ -0,0 +1,196 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Extensible Firmware Interface + * + * Based on Extensible Firmware Interface Specification version 2.4 + * + * Copyright (C) 2013, 2014 Linaro Ltd. + */ + +#include <linux/efi.h> +#include <linux/init.h> + +#include <asm/efi.h> +#include <asm/stacktrace.h> + +static bool region_is_misaligned(const efi_memory_desc_t *md) +{ + if (PAGE_SIZE == EFI_PAGE_SIZE) + return false; + return !PAGE_ALIGNED(md->phys_addr) || + !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT); +} + +/* + * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be + * executable, everything else can be mapped with the XN bits + * set. Also take the new (optional) RO/XP bits into account. + */ +static __init pteval_t create_mapping_protection(efi_memory_desc_t *md) +{ + u64 attr = md->attribute; + u32 type = md->type; + + if (type == EFI_MEMORY_MAPPED_IO) + return PROT_DEVICE_nGnRE; + + if (region_is_misaligned(md)) { + static bool __initdata code_is_misaligned; + + /* + * Regions that are not aligned to the OS page size cannot be + * mapped with strict permissions, as those might interfere + * with the permissions that are needed by the adjacent + * region's mapping. However, if we haven't encountered any + * misaligned runtime code regions so far, we can safely use + * non-executable permissions for non-code regions. + */ + code_is_misaligned |= (type == EFI_RUNTIME_SERVICES_CODE); + + return code_is_misaligned ? pgprot_val(PAGE_KERNEL_EXEC) + : pgprot_val(PAGE_KERNEL); + } + + /* R-- */ + if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) == + (EFI_MEMORY_XP | EFI_MEMORY_RO)) + return pgprot_val(PAGE_KERNEL_RO); + + /* R-X */ + if (attr & EFI_MEMORY_RO) + return pgprot_val(PAGE_KERNEL_ROX); + + /* RW- */ + if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) == + EFI_MEMORY_XP) || + type != EFI_RUNTIME_SERVICES_CODE) + return pgprot_val(PAGE_KERNEL); + + /* RWX */ + return pgprot_val(PAGE_KERNEL_EXEC); +} + +/* we will fill this structure from the stub, so don't put it in .bss */ +struct screen_info screen_info __section(".data"); +EXPORT_SYMBOL(screen_info); + +int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md) +{ + pteval_t prot_val = create_mapping_protection(md); + bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE || + md->type == EFI_RUNTIME_SERVICES_DATA); + + /* + * If this region is not aligned to the page size used by the OS, the + * mapping will be rounded outwards, and may end up sharing a page + * frame with an adjacent runtime memory region. Given that the page + * table descriptor covering the shared page will be rewritten when the + * adjacent region gets mapped, we must avoid block mappings here so we + * don't have to worry about splitting them when that happens. + */ + if (region_is_misaligned(md)) + page_mappings_only = true; + + create_pgd_mapping(mm, md->phys_addr, md->virt_addr, + md->num_pages << EFI_PAGE_SHIFT, + __pgprot(prot_val | PTE_NG), page_mappings_only); + return 0; +} + +static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data) +{ + efi_memory_desc_t *md = data; + pte_t pte = READ_ONCE(*ptep); + + if (md->attribute & EFI_MEMORY_RO) + pte = set_pte_bit(pte, __pgprot(PTE_RDONLY)); + if (md->attribute & EFI_MEMORY_XP) + pte = set_pte_bit(pte, __pgprot(PTE_PXN)); + set_pte(ptep, pte); + return 0; +} + +int __init efi_set_mapping_permissions(struct mm_struct *mm, + efi_memory_desc_t *md) +{ + BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE && + md->type != EFI_RUNTIME_SERVICES_DATA); + + if (region_is_misaligned(md)) + return 0; + + /* + * Calling apply_to_page_range() is only safe on regions that are + * guaranteed to be mapped down to pages. Since we are only called + * for regions that have been mapped using efi_create_mapping() above + * (and this is checked by the generic Memory Attributes table parsing + * routines), there is no need to check that again here. + */ + return apply_to_page_range(mm, md->virt_addr, + md->num_pages << EFI_PAGE_SHIFT, + set_permissions, md); +} + +/* + * UpdateCapsule() depends on the system being shutdown via + * ResetSystem(). + */ +bool efi_poweroff_required(void) +{ + return efi_enabled(EFI_RUNTIME_SERVICES); +} + +asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f) +{ + pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f); + return s; +} + +DEFINE_RAW_SPINLOCK(efi_rt_lock); + +asmlinkage u64 *efi_rt_stack_top __ro_after_init; + +asmlinkage efi_status_t __efi_rt_asm_recover(void); + +bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg) +{ + /* Check whether the exception occurred while running the firmware */ + if (!current_in_efi() || regs->pc >= TASK_SIZE_64) + return false; + + pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg); + add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK); + clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); + + regs->regs[0] = EFI_ABORTED; + regs->regs[30] = efi_rt_stack_top[-1]; + regs->pc = (u64)__efi_rt_asm_recover; + + if (IS_ENABLED(CONFIG_SHADOW_CALL_STACK)) + regs->regs[18] = efi_rt_stack_top[-2]; + + return true; +} + +/* EFI requires 8 KiB of stack space for runtime services */ +static_assert(THREAD_SIZE >= SZ_8K); + +static int __init arm64_efi_rt_init(void) +{ + void *p; + + if (!efi_enabled(EFI_RUNTIME_SERVICES)) + return 0; + + p = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, GFP_KERNEL, + NUMA_NO_NODE, &&l); +l: if (!p) { + pr_warn("Failed to allocate EFI runtime stack\n"); + clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); + return -ENOMEM; + } + + efi_rt_stack_top = p + THREAD_SIZE; + return 0; +} +core_initcall(arm64_efi_rt_init); |