1 files changed, 83 insertions, 18 deletions

diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index e1be6c429810..fab05de2e12d 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -12,6 +12,14 @@
 
 #include <asm/efi.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
@@ -25,14 +33,22 @@ static __init pteval_t create_mapping_protection(efi_memory_desc_t *md)
 	if (type == EFI_MEMORY_MAPPED_IO)
 		return PROT_DEVICE_nGnRE;
 
-	if (WARN_ONCE(!PAGE_ALIGNED(md->phys_addr),
-		      "UEFI Runtime regions are not aligned to 64 KB -- buggy firmware?"))
+	if (region_is_misaligned(md)) {
+		static bool __initdata code_is_misaligned;
+
 		/*
-		 * If the region is not aligned to the page size of the OS, we
-		 * can not use strict permissions, since that would also affect
-		 * the mapping attributes of the adjacent regions.
+		 * 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.
 		 */
-		return pgprot_val(PAGE_KERNEL_EXEC);
+		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)) ==
@@ -63,19 +79,16 @@ int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
 	bool page_mappings_only = (md->type == EFI_RUNTIME_SERVICES_CODE ||
 				   md->type == EFI_RUNTIME_SERVICES_DATA);
 
-	if (!PAGE_ALIGNED(md->phys_addr) ||
-	    !PAGE_ALIGNED(md->num_pages << EFI_PAGE_SHIFT)) {
-		/*
-		 * If the end address of this region is not aligned to page
-		 * size, the mapping is rounded up, and may end up sharing a
-		 * page frame with the next UEFI memory region. If we create
-		 * a block entry now, we may need to split it again when mapping
-		 * the next region, and support for that is going to be removed
-		 * from the MMU routines. So avoid block mappings altogether in
-		 * that case.
-		 */
+	/*
+	 * 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,
@@ -102,6 +115,9 @@ int __init efi_set_mapping_permissions(struct mm_struct *mm,
 	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
@@ -128,3 +144,52 @@ 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_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_work() != &efi_rts_work.work || 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);