Merge tag 'efi-next-for-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi

Pull EFI updates from Ard Biesheuvel:

- Decouple mixed mode startup code from the traditional x86
decompressor

- Revert zero-length file hack in efivarfs

- Prevent EFI zboot from using the CopyMem/SetMem boot services after
ExitBootServices()

- Update EFI zboot to use the ZLIB/ZSTD library interfaces directly

* tag 'efi-next-for-v6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
efi/libstub: Avoid legacy decompressor zlib/zstd wrappers
efi/libstub: Avoid CopyMem/SetMem EFI services after ExitBootServices
efi: efibc: change kmalloc(size * count, ...) to kmalloc_array()
efivarfs: Revert "allow creation of zero length files"
x86/efi/mixed: Move mixed mode startup code into libstub
x86/efi/mixed: Simplify and document thunking logic
x86/efi/mixed: Remove dependency on legacy startup_32 code
x86/efi/mixed: Set up 1:1 mapping of lower 4GiB in the stub
x86/efi/mixed: Factor out and clean up long mode entry
x86/efi/mixed: Check CPU compatibility without relying on verify_cpu()
x86/efistub: Merge PE and handover entrypoints

arch/x86/boot/compressed/Makefile

···
 vmlinux-objs-$(CONFIG_UNACCEPTED_MEMORY) += $(obj)/mem.o
 
 vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
-vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.o
 vmlinux-libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
 
 $(obj)/vmlinux: $(vmlinux-objs-y) $(vmlinux-libs-y) FORCE

arch/x86/boot/compressed/efi_mixed.S

···
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 2014, 2015 Intel Corporation; author Matt Fleming
- *
- * Early support for invoking 32-bit EFI services from a 64-bit kernel.
- *
- * Because this thunking occurs before ExitBootServices() we have to
- * restore the firmware's 32-bit GDT and IDT before we make EFI service
- * calls.
- *
- * On the plus side, we don't have to worry about mangling 64-bit
- * addresses into 32-bits because we're executing with an identity
- * mapped pagetable and haven't transitioned to 64-bit virtual addresses
- * yet.
- */
-
-#include <linux/linkage.h>
-#include <asm/asm-offsets.h>
-#include <asm/msr.h>
-#include <asm/page_types.h>
-#include <asm/processor-flags.h>
-#include <asm/segment.h>
-#include <asm/setup.h>
-
-	.code64
-	.text
-/*
- * When booting in 64-bit mode on 32-bit EFI firmware, startup_64_mixed_mode()
- * is the first thing that runs after switching to long mode. Depending on
- * whether the EFI handover protocol or the compat entry point was used to
- * enter the kernel, it will either branch to the common 64-bit EFI stub
- * entrypoint efi_stub_entry() directly, or via the 64-bit EFI PE/COFF
- * entrypoint efi_pe_entry(). In the former case, the bootloader must provide a
- * struct bootparams pointer as the third argument, so the presence of such a
- * pointer is used to disambiguate.
- *
- *                                                             +--------------+
- *  +------------------+     +------------+            +------>| efi_pe_entry |
- *  | efi32_pe_entry   |---->|            |            |       +-----------+--+
- *  +------------------+     |            |     +------+----------------+  |
- *                           | startup_32 |---->| startup_64_mixed_mode |  |
- *  +------------------+     |            |     +------+----------------+  |
- *  | efi32_stub_entry |---->|            |            |                   |
- *  +------------------+     +------------+            |                   |
- *                                                     V                   |
- *                           +------------+     +----------------+         |
- *                           | startup_64 |<----| efi_stub_entry |<--------+
- *                           +------------+     +----------------+
- */
-SYM_FUNC_START(startup_64_mixed_mode)
-	lea	efi32_boot_args(%rip), %rdx
-	mov	0(%rdx), %edi
-	mov	4(%rdx), %esi
-
-	/* Switch to the firmware's stack */
-	movl	efi32_boot_sp(%rip), %esp
-	andl	$~7, %esp
-
-#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
-	mov	8(%rdx), %edx		// saved bootparams pointer
-	test	%edx, %edx
-	jnz	efi_stub_entry
-#endif
-	/*
-	 * efi_pe_entry uses MS calling convention, which requires 32 bytes of
-	 * shadow space on the stack even if all arguments are passed in
-	 * registers. We also need an additional 8 bytes for the space that
-	 * would be occupied by the return address, and this also results in
-	 * the correct stack alignment for entry.
-	 */
-	sub	$40, %rsp
-	mov	%rdi, %rcx		// MS calling convention
-	mov	%rsi, %rdx
-	jmp	efi_pe_entry
-SYM_FUNC_END(startup_64_mixed_mode)
-
-SYM_FUNC_START(__efi64_thunk)
-	push	%rbp
-	push	%rbx
-
-	movl	%ds, %eax
-	push	%rax
-	movl	%es, %eax
-	push	%rax
-	movl	%ss, %eax
-	push	%rax
-
-	/* Copy args passed on stack */
-	movq	0x30(%rsp), %rbp
-	movq	0x38(%rsp), %rbx
-	movq	0x40(%rsp), %rax
-
-	/*
-	 * Convert x86-64 ABI params to i386 ABI
-	 */
-	subq	$64, %rsp
-	movl	%esi, 0x0(%rsp)
-	movl	%edx, 0x4(%rsp)
-	movl	%ecx, 0x8(%rsp)
-	movl	%r8d, 0xc(%rsp)
-	movl	%r9d, 0x10(%rsp)
-	movl	%ebp, 0x14(%rsp)
-	movl	%ebx, 0x18(%rsp)
-	movl	%eax, 0x1c(%rsp)
-
-	leaq	0x20(%rsp), %rbx
-	sgdt	(%rbx)
-	sidt	16(%rbx)
-
-	leaq	1f(%rip), %rbp
-
-	/*
-	 * Switch to IDT and GDT with 32-bit segments. These are the firmware
-	 * GDT and IDT that were installed when the kernel started executing.
-	 * The pointers were saved by the efi32_entry() routine below.
-	 *
-	 * Pass the saved DS selector to the 32-bit code, and use far return to
-	 * restore the saved CS selector.
-	 */
-	lidt	efi32_boot_idt(%rip)
-	lgdt	efi32_boot_gdt(%rip)
-
-	movzwl	efi32_boot_ds(%rip), %edx
-	movzwq	efi32_boot_cs(%rip), %rax
-	pushq	%rax
-	leaq	efi_enter32(%rip), %rax
-	pushq	%rax
-	lretq
-
-1:	addq	$64, %rsp
-	movq	%rdi, %rax
-
-	pop	%rbx
-	movl	%ebx, %ss
-	pop	%rbx
-	movl	%ebx, %es
-	pop	%rbx
-	movl	%ebx, %ds
-	/* Clear out 32-bit selector from FS and GS */
-	xorl	%ebx, %ebx
-	movl	%ebx, %fs
-	movl	%ebx, %gs
-
-	pop	%rbx
-	pop	%rbp
-	RET
-SYM_FUNC_END(__efi64_thunk)
-
-	.code32
-#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
-SYM_FUNC_START(efi32_stub_entry)
-	call	1f
-1:	popl	%ecx
-	leal	(efi32_boot_args - 1b)(%ecx), %ebx
-
-	/* Clear BSS */
-	xorl	%eax, %eax
-	leal	(_bss - 1b)(%ecx), %edi
-	leal	(_ebss - 1b)(%ecx), %ecx
-	subl	%edi, %ecx
-	shrl	$2, %ecx
-	cld
-	rep	stosl
-
-	add	$0x4, %esp		/* Discard return address */
-	popl	%ecx
-	popl	%edx
-	popl	%esi
-	movl	%esi, 8(%ebx)
-	jmp	efi32_entry
-SYM_FUNC_END(efi32_stub_entry)
-#endif
-
-/*
- * EFI service pointer must be in %edi.
- *
- * The stack should represent the 32-bit calling convention.
- */
-SYM_FUNC_START_LOCAL(efi_enter32)
-	/* Load firmware selector into data and stack segment registers */
-	movl	%edx, %ds
-	movl	%edx, %es
-	movl	%edx, %fs
-	movl	%edx, %gs
-	movl	%edx, %ss
-
-	/* Reload pgtables */
-	movl	%cr3, %eax
-	movl	%eax, %cr3
-
-	/* Disable paging */
-	movl	%cr0, %eax
-	btrl	$X86_CR0_PG_BIT, %eax
-	movl	%eax, %cr0
-
-	/* Disable long mode via EFER */
-	movl	$MSR_EFER, %ecx
-	rdmsr
-	btrl	$_EFER_LME, %eax
-	wrmsr
-
-	call	*%edi
-
-	/* We must preserve return value */
-	movl	%eax, %edi
-
-	/*
-	 * Some firmware will return with interrupts enabled. Be sure to
-	 * disable them before we switch GDTs and IDTs.
-	 */
-	cli
-
-	lidtl	16(%ebx)
-	lgdtl	(%ebx)
-
-	movl	%cr4, %eax
-	btsl	$(X86_CR4_PAE_BIT), %eax
-	movl	%eax, %cr4
-
-	movl	%cr3, %eax
-	movl	%eax, %cr3
-
-	movl	$MSR_EFER, %ecx
-	rdmsr
-	btsl	$_EFER_LME, %eax
-	wrmsr
-
-	xorl	%eax, %eax
-	lldt	%ax
-
-	pushl	$__KERNEL_CS
-	pushl	%ebp
-
-	/* Enable paging */
-	movl	%cr0, %eax
-	btsl	$X86_CR0_PG_BIT, %eax
-	movl	%eax, %cr0
-	lret
-SYM_FUNC_END(efi_enter32)
-
-/*
- * This is the common EFI stub entry point for mixed mode.
- *
- * Arguments:	%ecx	image handle
- * 		%edx	EFI system table pointer
- *
- * Since this is the point of no return for ordinary execution, no registers
- * are considered live except for the function parameters. [Note that the EFI
- * stub may still exit and return to the firmware using the Exit() EFI boot
- * service.]
- */
-SYM_FUNC_START_LOCAL(efi32_entry)
-	call	1f
-1:	pop	%ebx
-
-	/* Save firmware GDTR and code/data selectors */
-	sgdtl	(efi32_boot_gdt - 1b)(%ebx)
-	movw	%cs, (efi32_boot_cs - 1b)(%ebx)
-	movw	%ds, (efi32_boot_ds - 1b)(%ebx)
-
-	/* Store firmware IDT descriptor */
-	sidtl	(efi32_boot_idt - 1b)(%ebx)
-
-	/* Store firmware stack pointer */
-	movl	%esp, (efi32_boot_sp - 1b)(%ebx)
-
-	/* Store boot arguments */
-	leal	(efi32_boot_args - 1b)(%ebx), %ebx
-	movl	%ecx, 0(%ebx)
-	movl	%edx, 4(%ebx)
-	movb	$0x0, 12(%ebx)          // efi_is64
-
-	/*
-	 * Allocate some memory for a temporary struct boot_params, which only
-	 * needs the minimal pieces that startup_32() relies on.
-	 */
-	subl	$PARAM_SIZE, %esp
-	movl	%esp, %esi
-	movl	$PAGE_SIZE, BP_kernel_alignment(%esi)
-	movl	$_end - 1b, BP_init_size(%esi)
-	subl	$startup_32 - 1b, BP_init_size(%esi)
-
-	/* Disable paging */
-	movl	%cr0, %eax
-	btrl	$X86_CR0_PG_BIT, %eax
-	movl	%eax, %cr0
-
-	jmp	startup_32
-SYM_FUNC_END(efi32_entry)
-
-/*
- * efi_status_t efi32_pe_entry(efi_handle_t image_handle,
- *			       efi_system_table_32_t *sys_table)
- */
-SYM_FUNC_START(efi32_pe_entry)
-	pushl	%ebp
-	movl	%esp, %ebp
-	pushl	%ebx				// save callee-save registers
-	pushl	%edi
-
-	call	verify_cpu			// check for long mode support
-	testl	%eax, %eax
-	movl	$0x80000003, %eax		// EFI_UNSUPPORTED
-	jnz	2f
-
-	movl	8(%ebp), %ecx			// image_handle
-	movl	12(%ebp), %edx			// sys_table
-	jmp	efi32_entry			// pass %ecx, %edx
-						// no other registers remain live
-
-2:	popl	%edi				// restore callee-save registers
-	popl	%ebx
-	leave
-	RET
-SYM_FUNC_END(efi32_pe_entry)
-
-#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
-	.org	efi32_stub_entry + 0x200
-	.code64
-SYM_FUNC_START_NOALIGN(efi64_stub_entry)
-	jmp	efi_handover_entry
-SYM_FUNC_END(efi64_stub_entry)
-#endif
-
-	.data
-	.balign	8
-SYM_DATA_START_LOCAL(efi32_boot_gdt)
-	.word	0
-	.quad	0
-SYM_DATA_END(efi32_boot_gdt)
-
-SYM_DATA_START_LOCAL(efi32_boot_idt)
-	.word	0
-	.quad	0
-SYM_DATA_END(efi32_boot_idt)
-
-SYM_DATA_LOCAL(efi32_boot_cs, .word 0)
-SYM_DATA_LOCAL(efi32_boot_ds, .word 0)
-SYM_DATA_LOCAL(efi32_boot_sp, .long 0)
-SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0)
-SYM_DATA(efi_is64, .byte 1)

arch/x86/boot/compressed/head_64.S

···
 	 * used to perform that far jump.
 	 */
 	leal	rva(startup_64)(%ebp), %eax
-#ifdef CONFIG_EFI_MIXED
-	cmpb	$1, rva(efi_is64)(%ebp)
-	je	1f
-	leal	rva(startup_64_mixed_mode)(%ebp), %eax
-1:
-#endif
-
 	pushl	$__KERNEL_CS
 	pushl	%eax
 

drivers/firmware/efi/efibc.c

···
 	if (ret || !data)
 		return NOTIFY_DONE;
 
-	wdata = kmalloc(MAX_DATA_LEN * sizeof(efi_char16_t), GFP_KERNEL);
+	wdata = kmalloc_array(MAX_DATA_LEN, sizeof(efi_char16_t), GFP_KERNEL);
 	if (!wdata)
 		return NOTIFY_DONE;
 

drivers/firmware/efi/libstub/Makefile

···
 # `-fdata-sections` flag from KBUILD_CFLAGS_KERNEL
 KBUILD_CFLAGS_KERNEL := $(filter-out -fdata-sections, $(KBUILD_CFLAGS_KERNEL))
 
+KBUILD_AFLAGS			:= $(KBUILD_CFLAGS) -D__ASSEMBLY__
+
 lib-y				:= efi-stub-helper.o gop.o secureboot.o tpm.o \
 				   file.o mem.o random.o randomalloc.o pci.o \
 				   skip_spaces.o lib-cmdline.o lib-ctype.o \
···
 lib-$(CONFIG_ARM)		+= arm32-stub.o
 lib-$(CONFIG_ARM64)		+= kaslr.o arm64.o arm64-stub.o smbios.o
 lib-$(CONFIG_X86)		+= x86-stub.o smbios.o
+lib-$(CONFIG_EFI_MIXED)		+= x86-mixed.o
 lib-$(CONFIG_X86_64)		+= x86-5lvl.o
 lib-$(CONFIG_RISCV)		+= kaslr.o riscv.o riscv-stub.o
 lib-$(CONFIG_LOONGARCH)		+= loongarch.o loongarch-stub.o
 
 CFLAGS_arm32-stub.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
 
-zboot-obj-$(CONFIG_RISCV)	:= lib-clz_ctz.o lib-ashldi3.o
+zboot-obj-y			:= zboot-decompress-gzip.o
+CFLAGS_zboot-decompress-gzip.o	+= -I$(srctree)/lib/zlib_inflate
+zboot-obj-$(CONFIG_KERNEL_ZSTD)	:= zboot-decompress-zstd.o lib-xxhash.o
+CFLAGS_zboot-decompress-zstd.o	+= -I$(srctree)/lib/zstd
+
+zboot-obj-$(CONFIG_RISCV)	+= lib-clz_ctz.o lib-ashldi3.o
 lib-$(CONFIG_EFI_ZBOOT)		+= zboot.o $(zboot-obj-y)
 
 lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o

drivers/firmware/efi/libstub/efistub.h

···
 void accept_memory(phys_addr_t start, unsigned long size);
 void arch_accept_memory(phys_addr_t start, phys_addr_t end);
 
+efi_status_t efi_zboot_decompress_init(unsigned long *alloc_size);
+efi_status_t efi_zboot_decompress(u8 *out, unsigned long outlen);
+
 #endif

drivers/firmware/efi/libstub/intrinsics.c

···
 void *__memset(void *s, int c, size_t count) __alias(memset);
 #endif
 
+static void *efistub_memmove(u8 *dst, const u8 *src, size_t len)
+{
+	if (src > dst || dst >= (src + len))
+		for (size_t i = 0; i < len; i++)
+			dst[i] = src[i];
+	else
+		for (ssize_t i = len - 1; i >= 0; i--)
+			dst[i] = src[i];
+
+	return dst;
+}
+
+static void *efistub_memset(void *dst, int c, size_t len)
+{
+	for (u8 *d = dst; len--; d++)
+		*d = c;
+
+	return dst;
+}
+
 void *memcpy(void *dst, const void *src, size_t len)
 {
+	if (efi_table_attr(efi_system_table, boottime) == NULL)
+		return efistub_memmove(dst, src, len);
+
 	efi_bs_call(copy_mem, dst, src, len);
 	return dst;
 }
···
 
 void *memset(void *dst, int c, size_t len)
 {
+	if (efi_table_attr(efi_system_table, boottime) == NULL)
+		return efistub_memset(dst, c, len);
+
 	efi_bs_call(set_mem, dst, len, c & U8_MAX);
 	return dst;
 }

drivers/firmware/efi/libstub/x86-mixed.S

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2014, 2015 Intel Corporation; author Matt Fleming
+ *
+ * Early support for invoking 32-bit EFI services from a 64-bit kernel.
+ *
+ * Because this thunking occurs before ExitBootServices() we have to
+ * restore the firmware's 32-bit GDT and IDT before we make EFI service
+ * calls.
+ *
+ * On the plus side, we don't have to worry about mangling 64-bit
+ * addresses into 32-bits because we're executing with an identity
+ * mapped pagetable and haven't transitioned to 64-bit virtual addresses
+ * yet.
+ */
+
+#include <linux/linkage.h>
+#include <asm/desc_defs.h>
+#include <asm/msr.h>
+#include <asm/page_types.h>
+#include <asm/pgtable_types.h>
+#include <asm/processor-flags.h>
+#include <asm/segment.h>
+
+	.text
+	.code32
+#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
+SYM_FUNC_START(efi32_stub_entry)
+	call	1f
+1:	popl	%ecx
+
+	/* Clear BSS */
+	xorl	%eax, %eax
+	leal	(_bss - 1b)(%ecx), %edi
+	leal	(_ebss - 1b)(%ecx), %ecx
+	subl	%edi, %ecx
+	shrl	$2, %ecx
+	cld
+	rep	stosl
+
+	add	$0x4, %esp		/* Discard return address */
+	movl	8(%esp), %ebx		/* struct boot_params pointer */
+	jmp	efi32_startup
+SYM_FUNC_END(efi32_stub_entry)
+#endif
+
+/*
+ * Called using a far call from __efi64_thunk() below, using the x86_64 SysV
+ * ABI (except for R8/R9 which are inaccessible to 32-bit code - EAX/EBX are
+ * used instead).  EBP+16 points to the arguments passed via the stack.
+ *
+ * The first argument (EDI) is a pointer to the boot service or protocol, to
+ * which the remaining arguments are passed, each truncated to 32 bits.
+ */
+SYM_FUNC_START_LOCAL(efi_enter32)
+	/*
+	 * Convert x86-64 SysV ABI params to i386 ABI
+	 */
+	pushl	32(%ebp)	/* Up to 3 args passed via the stack */
+	pushl	24(%ebp)
+	pushl	16(%ebp)
+	pushl	%ebx		/* R9 */
+	pushl	%eax		/* R8 */
+	pushl	%ecx
+	pushl	%edx
+	pushl	%esi
+
+	/* Disable paging */
+	movl	%cr0, %eax
+	btrl	$X86_CR0_PG_BIT, %eax
+	movl	%eax, %cr0
+
+	/* Disable long mode via EFER */
+	movl	$MSR_EFER, %ecx
+	rdmsr
+	btrl	$_EFER_LME, %eax
+	wrmsr
+
+	call	*%edi
+
+	/* We must preserve return value */
+	movl	%eax, %edi
+
+	call	efi32_enable_long_mode
+
+	addl	$32, %esp
+	movl	%edi, %eax
+	lret
+SYM_FUNC_END(efi_enter32)
+
+	.code64
+SYM_FUNC_START(__efi64_thunk)
+	push	%rbp
+	movl	%esp, %ebp
+	push	%rbx
+
+	/* Move args #5 and #6 into 32-bit accessible registers */
+	movl	%r8d, %eax
+	movl	%r9d, %ebx
+
+	lcalll	*efi32_call(%rip)
+
+	pop	%rbx
+	pop	%rbp
+	RET
+SYM_FUNC_END(__efi64_thunk)
+
+	.code32
+SYM_FUNC_START_LOCAL(efi32_enable_long_mode)
+	movl	%cr4, %eax
+	btsl	$(X86_CR4_PAE_BIT), %eax
+	movl	%eax, %cr4
+
+	movl	$MSR_EFER, %ecx
+	rdmsr
+	btsl	$_EFER_LME, %eax
+	wrmsr
+
+	/* Disable interrupts - the firmware's IDT does not work in long mode */
+	cli
+
+	/* Enable paging */
+	movl	%cr0, %eax
+	btsl	$X86_CR0_PG_BIT, %eax
+	movl	%eax, %cr0
+	ret
+SYM_FUNC_END(efi32_enable_long_mode)
+
+/*
+ * This is the common EFI stub entry point for mixed mode. It sets up the GDT
+ * and page tables needed for 64-bit execution, after which it calls the
+ * common 64-bit EFI entrypoint efi_stub_entry().
+ *
+ * Arguments:	0(%esp)	image handle
+ * 		4(%esp)	EFI system table pointer
+ *		%ebx	struct boot_params pointer (or NULL)
+ *
+ * Since this is the point of no return for ordinary execution, no registers
+ * are considered live except for the function parameters. [Note that the EFI
+ * stub may still exit and return to the firmware using the Exit() EFI boot
+ * service.]
+ */
+SYM_FUNC_START_LOCAL(efi32_startup)
+	movl	%esp, %ebp
+
+	subl	$8, %esp
+	sgdtl	(%esp)			/* Save GDT descriptor to the stack */
+	movl	2(%esp), %esi		/* Existing GDT pointer */
+	movzwl	(%esp), %ecx		/* Existing GDT limit */
+	inc	%ecx			/* Existing GDT size */
+	andl	$~7, %ecx		/* Ensure size is multiple of 8 */
+
+	subl	%ecx, %esp		/* Allocate new GDT */
+	andl	$~15, %esp		/* Realign the stack */
+	movl	%esp, %edi		/* New GDT address */
+	leal	7(%ecx), %eax		/* New GDT limit */
+	pushw	%cx			/* Push 64-bit CS (for LJMP below) */
+	pushl	%edi			/* Push new GDT address */
+	pushw	%ax			/* Push new GDT limit */
+
+	/* Copy GDT to the stack and add a 64-bit code segment at the end */
+	movl	$GDT_ENTRY(DESC_CODE64, 0, 0xfffff) & 0xffffffff, (%edi,%ecx)
+	movl	$GDT_ENTRY(DESC_CODE64, 0, 0xfffff) >> 32, 4(%edi,%ecx)
+	shrl	$2, %ecx
+	cld
+	rep	movsl			/* Copy the firmware GDT */
+	lgdtl	(%esp)			/* Switch to the new GDT */
+
+	call	1f
+1:	pop	%edi
+
+	/* Record mixed mode entry */
+	movb	$0x0, (efi_is64 - 1b)(%edi)
+
+	/* Set up indirect far call to re-enter 32-bit mode */
+	leal	(efi32_call - 1b)(%edi), %eax
+	addl	%eax, (%eax)
+	movw	%cs, 4(%eax)
+
+	/* Disable paging */
+	movl	%cr0, %eax
+	btrl	$X86_CR0_PG_BIT, %eax
+	movl	%eax, %cr0
+
+	/* Set up 1:1 mapping */
+	leal	(pte - 1b)(%edi), %eax
+	movl	$_PAGE_PRESENT | _PAGE_RW | _PAGE_PSE, %ecx
+	leal	(_PAGE_PRESENT | _PAGE_RW)(%eax), %edx
+2:	movl	%ecx, (%eax)
+	addl	$8, %eax
+	addl	$PMD_SIZE, %ecx
+	jnc	2b
+
+	movl	$PAGE_SIZE, %ecx
+	.irpc	l, 0123
+	movl	%edx, \l * 8(%eax)
+	addl	%ecx, %edx
+	.endr
+	addl	%ecx, %eax
+	movl	%edx, (%eax)
+	movl	%eax, %cr3
+
+	call	efi32_enable_long_mode
+
+	/* Set up far jump to 64-bit mode (CS is already on the stack) */
+	leal	(efi_stub_entry - 1b)(%edi), %eax
+	movl	%eax, 2(%esp)
+
+	movl	0(%ebp), %edi
+	movl	4(%ebp), %esi
+	movl	%ebx, %edx
+	ljmpl	*2(%esp)
+SYM_FUNC_END(efi32_startup)
+
+/*
+ * efi_status_t efi32_pe_entry(efi_handle_t image_handle,
+ *			       efi_system_table_32_t *sys_table)
+ */
+SYM_FUNC_START(efi32_pe_entry)
+	pushl	%ebx				// save callee-save registers
+
+	/* Check whether the CPU supports long mode */
+	movl	$0x80000001, %eax		// assume extended info support
+	cpuid
+	btl	$29, %edx			// check long mode bit
+	jnc	1f
+	leal	8(%esp), %esp			// preserve stack alignment
+	xor	%ebx, %ebx			// no struct boot_params pointer
+	jmp	efi32_startup			// only ESP and EBX remain live
+1:	movl	$0x80000003, %eax		// EFI_UNSUPPORTED
+	popl	%ebx
+	RET
+SYM_FUNC_END(efi32_pe_entry)
+
+#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
+	.org	efi32_stub_entry + 0x200
+	.code64
+SYM_FUNC_START_NOALIGN(efi64_stub_entry)
+	jmp	efi_handover_entry
+SYM_FUNC_END(efi64_stub_entry)
+#endif
+
+	.data
+	.balign	8
+SYM_DATA_START_LOCAL(efi32_call)
+	.long	efi_enter32 - .
+	.word	0x0
+SYM_DATA_END(efi32_call)
+SYM_DATA(efi_is64, .byte 1)
+
+	.bss
+	.balign PAGE_SIZE
+SYM_DATA_LOCAL(pte, .fill 6 * PAGE_SIZE, 1, 0)

drivers/firmware/efi/libstub/x86-stub.c

···
 		asm("hlt");
 }
 
-void __noreturn efi_stub_entry(efi_handle_t handle,
-			       efi_system_table_t *sys_table_arg,
-			       struct boot_params *boot_params);
-
 /*
  * Because the x86 boot code expects to be passed a boot_params we
  * need to create one ourselves (usually the bootloader would create
  * one for us).
  */
-efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
-				   efi_system_table_t *sys_table_arg)
+static efi_status_t efi_allocate_bootparams(efi_handle_t handle,
+					    struct boot_params **bp)
 {
 	efi_guid_t proto = LOADED_IMAGE_PROTOCOL_GUID;
 	struct boot_params *boot_params;
···
 	unsigned long alloc;
 	char *cmdline_ptr;
 
-	efi_system_table = sys_table_arg;
-
-	/* Check if we were booted by the EFI firmware */
-	if (efi_system_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
-		efi_exit(handle, EFI_INVALID_PARAMETER);
-
 	status = efi_bs_call(handle_protocol, handle, &proto, (void **)&image);
 	if (status != EFI_SUCCESS) {
 		efi_err("Failed to get handle for LOADED_IMAGE_PROTOCOL\n");
-		efi_exit(handle, status);
+		return status;
 	}
 
 	status = efi_allocate_pages(PARAM_SIZE, &alloc, ULONG_MAX);
 	if (status != EFI_SUCCESS)
-		efi_exit(handle, status);
+		return status;
 
 	boot_params = memset((void *)alloc, 0x0, PARAM_SIZE);
 	hdr	    = &boot_params->hdr;
···
 	cmdline_ptr = efi_convert_cmdline(image);
 	if (!cmdline_ptr) {
 		efi_free(PARAM_SIZE, alloc);
-		efi_exit(handle, EFI_OUT_OF_RESOURCES);
+		return EFI_OUT_OF_RESOURCES;
 	}
 
 	efi_set_u64_split((unsigned long)cmdline_ptr, &hdr->cmd_line_ptr,
 			  &boot_params->ext_cmd_line_ptr);
 
-	efi_stub_entry(handle, sys_table_arg, boot_params);
-	/* not reached */
+	*bp = boot_params;
+	return EFI_SUCCESS;
 }
 
 static void add_e820ext(struct boot_params *params,
···
 	return efi_parse_options(cmdline);
 }
 
-static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry)
+static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry,
+					  struct boot_params *boot_params)
 {
 	unsigned long virt_addr = LOAD_PHYSICAL_ADDR;
 	unsigned long addr, alloc_size, entry;
 	efi_status_t status;
 	u32 seed[2] = {};
+
+	boot_params_ptr	= boot_params;
 
 	/* determine the required size of the allocation */
 	alloc_size = ALIGN(max_t(unsigned long, output_len, kernel_total_size),
···
 			seed[0] = 0;
 		}
 
-		boot_params_ptr->hdr.loadflags |= KASLR_FLAG;
+		boot_params->hdr.loadflags |= KASLR_FLAG;
 	}
 
 	status = efi_random_alloc(alloc_size, CONFIG_PHYSICAL_ALIGN, &addr,
···
 void __noreturn efi_stub_entry(efi_handle_t handle,
 			       efi_system_table_t *sys_table_arg,
 			       struct boot_params *boot_params)
+
 {
 	efi_guid_t guid = EFI_MEMORY_ATTRIBUTE_PROTOCOL_GUID;
-	struct setup_header *hdr = &boot_params->hdr;
 	const struct linux_efi_initrd *initrd = NULL;
 	unsigned long kernel_entry;
+	struct setup_header *hdr;
 	efi_status_t status;
-
-	boot_params_ptr = boot_params;
 
 	efi_system_table = sys_table_arg;
 	/* Check if we were booted by the EFI firmware */
 	if (efi_system_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
 		efi_exit(handle, EFI_INVALID_PARAMETER);
+
+	if (!IS_ENABLED(CONFIG_EFI_HANDOVER_PROTOCOL) || !boot_params) {
+		status = efi_allocate_bootparams(handle, &boot_params);
+		if (status != EFI_SUCCESS)
+			efi_exit(handle, status);
+	}
+
+	hdr = &boot_params->hdr;
 
 	if (have_unsupported_snp_features())
 		efi_exit(handle, EFI_UNSUPPORTED);
···
 	if (efi_mem_encrypt > 0)
 		hdr->xloadflags |= XLF_MEM_ENCRYPTION;
 
-	status = efi_decompress_kernel(&kernel_entry);
+	status = efi_decompress_kernel(&kernel_entry, boot_params);
 	if (status != EFI_SUCCESS) {
 		efi_err("Failed to decompress kernel\n");
 		goto fail;
···
 	efi_err("efi_stub_entry() failed!\n");
 
 	efi_exit(handle, status);
+}
+
+efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
+				   efi_system_table_t *sys_table_arg)
+{
+	efi_stub_entry(handle, sys_table_arg, NULL);
 }
 
 #ifdef CONFIG_EFI_HANDOVER_PROTOCOL

drivers/firmware/efi/libstub/zboot-decompress-gzip.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi.h>
+#include <linux/zlib.h>
+
+#include <asm/efi.h>
+
+#include "efistub.h"
+
+#include "inftrees.c"
+#include "inffast.c"
+#include "inflate.c"
+
+extern unsigned char _gzdata_start[], _gzdata_end[];
+extern u32 __aligned(1) payload_size;
+
+static struct z_stream_s stream;
+
+efi_status_t efi_zboot_decompress_init(unsigned long *alloc_size)
+{
+	efi_status_t status;
+	int rc;
+
+	/* skip the 10 byte header, assume no recorded filename */
+	stream.next_in = _gzdata_start + 10;
+	stream.avail_in = _gzdata_end - stream.next_in;
+
+	status = efi_allocate_pages(zlib_inflate_workspacesize(),
+				    (unsigned long *)&stream.workspace,
+				    ULONG_MAX);
+	if (status != EFI_SUCCESS)
+		return status;
+
+	rc = zlib_inflateInit2(&stream, -MAX_WBITS);
+	if (rc != Z_OK) {
+		efi_err("failed to initialize GZIP decompressor: %d\n", rc);
+		status = EFI_LOAD_ERROR;
+		goto out;
+	}
+
+	*alloc_size = payload_size;
+	return EFI_SUCCESS;
+out:
+	efi_free(zlib_inflate_workspacesize(), (unsigned long)stream.workspace);
+	return status;
+}
+
+efi_status_t efi_zboot_decompress(u8 *out, unsigned long outlen)
+{
+	int rc;
+
+	stream.next_out = out;
+	stream.avail_out = outlen;
+
+	rc = zlib_inflate(&stream, 0);
+	zlib_inflateEnd(&stream);
+
+	efi_free(zlib_inflate_workspacesize(), (unsigned long)stream.workspace);
+
+	if (rc != Z_STREAM_END) {
+		efi_err("GZIP decompression failed with status %d\n", rc);
+		return EFI_LOAD_ERROR;
+	}
+
+	efi_cache_sync_image((unsigned long)out, outlen);
+
+	return EFI_SUCCESS;
+}

drivers/firmware/efi/libstub/zboot-decompress-zstd.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi.h>
+#include <linux/zstd.h>
+
+#include <asm/efi.h>
+
+#include "decompress_sources.h"
+#include "efistub.h"
+
+extern unsigned char _gzdata_start[], _gzdata_end[];
+extern u32 __aligned(1) payload_size;
+
+static size_t wksp_size;
+static void *wksp;
+
+efi_status_t efi_zboot_decompress_init(unsigned long *alloc_size)
+{
+	efi_status_t status;
+
+	wksp_size = zstd_dctx_workspace_bound();
+	status = efi_allocate_pages(wksp_size, (unsigned long *)&wksp, ULONG_MAX);
+	if (status != EFI_SUCCESS)
+		return status;
+
+	*alloc_size = payload_size;
+	return EFI_SUCCESS;
+}
+
+efi_status_t efi_zboot_decompress(u8 *out, unsigned long outlen)
+{
+	zstd_dctx *dctx = zstd_init_dctx(wksp, wksp_size);
+	size_t ret;
+	int retval;
+
+	ret = zstd_decompress_dctx(dctx, out, outlen, _gzdata_start,
+				   _gzdata_end - _gzdata_start - 4);
+	efi_free(wksp_size, (unsigned long)wksp);
+
+	retval = zstd_get_error_code(ret);
+	if (retval) {
+		efi_err("ZSTD-decompression failed with status %d\n", retval);
+		return EFI_LOAD_ERROR;
+	}
+
+	efi_cache_sync_image((unsigned long)out, outlen);
+
+	return EFI_SUCCESS;
+}

drivers/firmware/efi/libstub/zboot.c

···
 
 #include "efistub.h"
 
-static unsigned char zboot_heap[SZ_256K] __aligned(64);
-static unsigned long free_mem_ptr, free_mem_end_ptr;
-
-#define STATIC static
-#if defined(CONFIG_KERNEL_GZIP)
-#include "../../../../lib/decompress_inflate.c"
-#elif defined(CONFIG_KERNEL_LZ4)
-#include "../../../../lib/decompress_unlz4.c"
-#elif defined(CONFIG_KERNEL_LZMA)
-#include "../../../../lib/decompress_unlzma.c"
-#elif defined(CONFIG_KERNEL_LZO)
-#include "../../../../lib/decompress_unlzo.c"
-#elif defined(CONFIG_KERNEL_XZ)
-#undef memcpy
-#define memcpy memcpy
-#undef memmove
-#define memmove memmove
-#include "../../../../lib/decompress_unxz.c"
-#elif defined(CONFIG_KERNEL_ZSTD)
-#include "../../../../lib/decompress_unzstd.c"
-#endif
-
-extern char efi_zboot_header[];
-extern char _gzdata_start[], _gzdata_end[];
-
-static void error(char *x)
-{
-	efi_err("EFI decompressor: %s\n", x);
-}
-
 static unsigned long alloc_preferred_address(unsigned long alloc_size)
 {
 #ifdef EFI_KIMG_PREFERRED_ADDRESS
···
 asmlinkage efi_status_t __efiapi
 efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab)
 {
-	unsigned long compressed_size = _gzdata_end - _gzdata_start;
+	char *cmdline_ptr __free(efi_pool) = NULL;
 	unsigned long image_base, alloc_size;
 	efi_loaded_image_t *image;
 	efi_status_t status;
-	char *cmdline_ptr;
-	int ret;
 
 	WRITE_ONCE(efi_system_table, systab);
-
-	free_mem_ptr = (unsigned long)&zboot_heap;
-	free_mem_end_ptr = free_mem_ptr + sizeof(zboot_heap);
 
 	status = efi_bs_call(handle_protocol, handle,
 			     &LOADED_IMAGE_PROTOCOL_GUID, (void **)&image);
 	if (status != EFI_SUCCESS) {
-		error("Failed to locate parent's loaded image protocol");
+		efi_err("Failed to locate parent's loaded image protocol\n");
 		return status;
 	}
 
···
 
 	efi_info("Decompressing Linux Kernel...\n");
 
-	// SizeOfImage from the compressee's PE/COFF header
-	alloc_size = round_up(get_unaligned_le32(_gzdata_end - 4),
-			      EFI_ALLOC_ALIGN);
+	status = efi_zboot_decompress_init(&alloc_size);
+	if (status != EFI_SUCCESS)
+		return status;
 
 	 // If the architecture has a preferred address for the image,
 	 // try that first.
···
 					  seed, EFI_LOADER_CODE, 0, EFI_ALLOC_LIMIT);
 		if (status != EFI_SUCCESS) {
 			efi_err("Failed to allocate memory\n");
-			goto free_cmdline;
+			return status;
 		}
 	}
 
-	// Decompress the payload into the newly allocated buffer.
-	ret = __decompress(_gzdata_start, compressed_size, NULL, NULL,
-			   (void *)image_base, alloc_size, NULL, error);
-	if (ret	< 0) {
-		error("Decompression failed");
-		status = EFI_DEVICE_ERROR;
-		goto free_image;
-	}
+	// Decompress the payload into the newly allocated buffer
+	status = efi_zboot_decompress((void *)image_base, alloc_size) ?:
+	         efi_stub_common(handle, image, image_base, cmdline_ptr);
 
-	efi_cache_sync_image(image_base, alloc_size);
-
-	status = efi_stub_common(handle, image, image_base, cmdline_ptr);
-
-free_image:
 	efi_free(alloc_size, image_base);
-free_cmdline:
-	efi_bs_call(free_pool, cmdline_ptr);
 	return status;
 }

drivers/firmware/efi/libstub/zboot.lds

···
 	.rodata : ALIGN(8) {
 		__efistub__gzdata_start = .;
 		*(.gzdata)
+		__efistub_payload_size = . - 4;
 		__efistub__gzdata_end = .;
 		*(.rodata* .init.rodata* .srodata*)
 

fs/efivarfs/file.c

···
 
 	if (bytes == -ENOENT) {
 		/*
-		 * FIXME: temporary workaround for fwupdate, signal
-		 * failed write with a 1 to keep created but not
-		 * written files
+		 * zero size signals to release that the write deleted
+		 * the variable
 		 */
-		i_size_write(inode, 1);
+		i_size_write(inode, 0);
 	} else {
 		i_size_write(inode, datasize + sizeof(attributes));
 		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
···
 	struct efivar_entry *var = inode->i_private;
 
 	inode_lock(inode);
-	/* FIXME: temporary work around for fwupdate */
-	var->removed = (--var->open_count == 0 && i_size_read(inode) == 1);
+	var->removed = (--var->open_count == 0 && i_size_read(inode) == 0);
 	inode_unlock(inode);
 
 	if (var->removed)