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-rw-r--r--arch/arm64/kernel/efi.c196
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);