efi/arm64: libstub: Split off kernel image relocation for builtin stub

The arm64 build of the EFI stub is part of the core kernel image, and
therefore accesses section markers directly when it needs to figure out
the size of the various section.

The zboot decompressor does not have access to those symbols, but
doesn't really need that either. So let's move handle_kernel_image()
into a separate file (or rather, move everything else into a separate
file) so that the zboot build does not pull in unused code that links to
symbols that it does not define.

While at it, introduce a helper routine that the generic zboot loader
will need to invoke after decompressing the image but before invoking
it, to ensure that the I-side view of memory is consistent.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/Makefile

@@ -86,7 +86,7 @@ lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o string.o intrinsics.o systable.o \
 				   screen_info.o efi-stub-entry.o
 
 lib-$(CONFIG_ARM)		+= arm32-stub.o
-lib-$(CONFIG_ARM64)		+= arm64-stub.o arm64-entry.o
+lib-$(CONFIG_ARM64)		+= arm64.o arm64-stub.o arm64-entry.o
 lib-$(CONFIG_X86)		+= x86-stub.o
 lib-$(CONFIG_RISCV)		+= riscv.o riscv-stub.o
 lib-$(CONFIG_LOONGARCH)		+= loongarch-stub.o

drivers/firmware/efi/libstub/arm64-entry.S

@@ -8,6 +8,16 @@
 #include <linux/linkage.h>
 #include <asm/assembler.h>
 
+	/*
+	 * The entrypoint of a arm64 bare metal image is at offset #0 of the
+	 * image, so this is a reasonable default for primary_entry_offset.
+	 * Only when the EFI stub is integrated into the core kernel, it is not
+	 * guaranteed that the PE/COFF header has been copied to memory too, so
+	 * in this case, primary_entry_offset should be overridden by the
+	 * linker and point to primary_entry() directly.
+	 */
+	.weak	primary_entry_offset
+
 SYM_CODE_START(efi_enter_kernel)
 	/*
 	 * efi_pe_entry() will have copied the kernel image if necessary and we

drivers/firmware/efi/libstub/arm64-stub.c

@@ -11,37 +11,9 @@
 #include <asm/efi.h>
 #include <asm/memory.h>
 #include <asm/sections.h>
-#include <asm/sysreg.h>
 
 #include "efistub.h"
 
-efi_status_t check_platform_features(void)
-{
-	u64 tg;
-
-	/*
-	 * If we have 48 bits of VA space for TTBR0 mappings, we can map the
-	 * UEFI runtime regions 1:1 and so calling SetVirtualAddressMap() is
-	 * unnecessary.
-	 */
-	if (VA_BITS_MIN >= 48)
-		efi_novamap = true;
-
-	/* UEFI mandates support for 4 KB granularity, no need to check */
-	if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
-		return EFI_SUCCESS;
-
-	tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_EL1_TGRAN_SHIFT) & 0xf;
-	if (tg < ID_AA64MMFR0_EL1_TGRAN_SUPPORTED_MIN || tg > ID_AA64MMFR0_EL1_TGRAN_SUPPORTED_MAX) {
-		if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
-			efi_err("This 64 KB granular kernel is not supported by your CPU\n");
-		else
-			efi_err("This 16 KB granular kernel is not supported by your CPU\n");
-		return EFI_UNSUPPORTED;
-	}
-	return EFI_SUCCESS;
-}
-
 /*
  * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail
  * to provide space, and fail to zero it). Check for this condition by double

drivers/firmware/efi/libstub/arm64.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2013, 2014 Linaro Ltd;  <roy.franz@linaro.org>
+ *
+ * This file implements the EFI boot stub for the arm64 kernel.
+ * Adapted from ARM version by Mark Salter <msalter@redhat.com>
+ */
+
+
+#include <linux/efi.h>
+#include <asm/efi.h>
+#include <asm/memory.h>
+#include <asm/sysreg.h>
+
+#include "efistub.h"
+
+efi_status_t check_platform_features(void)
+{
+	u64 tg;
+
+	/*
+	 * If we have 48 bits of VA space for TTBR0 mappings, we can map the
+	 * UEFI runtime regions 1:1 and so calling SetVirtualAddressMap() is
+	 * unnecessary.
+	 */
+	if (VA_BITS_MIN >= 48)
+		efi_novamap = true;
+
+	/* UEFI mandates support for 4 KB granularity, no need to check */
+	if (IS_ENABLED(CONFIG_ARM64_4K_PAGES))
+		return EFI_SUCCESS;
+
+	tg = (read_cpuid(ID_AA64MMFR0_EL1) >> ID_AA64MMFR0_EL1_TGRAN_SHIFT) & 0xf;
+	if (tg < ID_AA64MMFR0_EL1_TGRAN_SUPPORTED_MIN || tg > ID_AA64MMFR0_EL1_TGRAN_SUPPORTED_MAX) {
+		if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
+			efi_err("This 64 KB granular kernel is not supported by your CPU\n");
+		else
+			efi_err("This 16 KB granular kernel is not supported by your CPU\n");
+		return EFI_UNSUPPORTED;
+	}
+	return EFI_SUCCESS;
+}
+
+void efi_cache_sync_image(unsigned long image_base,
+			  unsigned long alloc_size,
+			  unsigned long code_size)
+{
+	u32 ctr = read_cpuid_effective_cachetype();
+	u64 lsize = 4 << cpuid_feature_extract_unsigned_field(ctr,
+						CTR_EL0_DminLine_SHIFT);
+
+	do {
+		asm("dc civac, %0" :: "r"(image_base));
+		image_base += lsize;
+		alloc_size -= lsize;
+	} while (alloc_size >= lsize);
+
+	asm("ic ialluis");
+	dsb(ish);
+	isb();
+}

drivers/firmware/efi/libstub/efistub.h

@@ -986,4 +986,8 @@ void efi_retrieve_tpm2_eventlog(void);
 struct screen_info *alloc_screen_info(void);
 void free_screen_info(struct screen_info *si);
 
+void efi_cache_sync_image(unsigned long image_base,
+			  unsigned long alloc_size,
+			  unsigned long code_size);
+
 #endif